Computational Structural Engineering

This contribution discusses modern concepts in multi-scale analysis. Emphasis is placed in the discussion on so-called concurrent approaches, in which computations are carried out simultaneously at two or more scales. Since analyses at a lower level typically involve more discontinuities to be considered, attention is also paid to the proper modelling of evolving discontinuities. Another related problem is the treatment of discontinuities for problems that involve the modelling of diffusion phenomena in addition to a stress analysis, since this also requires the application of multi-scale concepts. As a further step the coupling of dissimilar media is considered like continuum to discrete models.

A method for damage cumulation analysis of welded joints under low-cycle loading is presented in this paper. A damage cumulation model for steel weld material is first generated based on results of tensile and strain-controlled low cycle fatigue tests carried out on specimens extracted from a welded T-joint. Finite element sub-program has been generated in the framework of a commercial FE package to predict the hysteretic behavior of welded joints under low cycle loadings considering damage cumulation of both steel and weld materials. Damage cumulation effect may be taken into account in seismic analysis of new welded structures and residual-strength/life prediction for maintenance or repair of existing structures.

A numerical approach is presented in this paper for the analysis of large concrete dams due to ageing degradation, based on damage mechanics concepts. The proposed method can be used to analyse the seismic responses of aged concrete dams by combining techniques such as degradation evaluation methods, damage mechanics, finite element/boundary element methods. The effect of ageing degradation is taken into account by introducing a degradation factor into formulations of damage mechanics.

Coupled analysis of mass transport and damage mechanics associated with steel corrosion is presented for structural performance assessment of reinforced concrete. Multi-scale modeling of micro-pore formation and transport phenomena of moisture and ions are mutually linked for predicting the corrosion of reinforcement and volumetric changes. The interaction of crack propagation with corroded gel migration is simulated. Two computer codes for multi-chemo physical simulation (

DuCOM

) and nonlinear dynamic mechanics of structural concrete (

COM3

) were combined and verified by the laboratory scale experiments of damaged reinforced concrete members under static and dynamic loads, and has been applied to safety and serviceability assessment of existing infrastructures.

In this paper a statistical multi-scale method for the mechanics parameter prediction of the rock mass with random distribution of multi-scale cracks/joints is presented. First the micro-structure of the rock mass with random distribution of multi-scale cracks/joints is represented. Then the statistical second-order two-scale method for the mechanics performance predictions of the rock mass structure with random cracks/joints distribution is presented, including the statistical second-order two-scale expression on the vector-valued displacement, strain tensor and stress tensor, and the algorithm procedure of statistical multi-sale computation for the mechanics parameters. Finally some numerical results for mechanical parameters for the rock mass with random distributions of multi-scale joints/cracks by statistical multi-scale method are shown.

Trefftz-FEM (T-FEM), Adaptive Cross Approximation BEM (ACA BEM) and Method of Continuous Source Functions (MCSF) are presented for simulation of Composites Reinforced by Short Fibres (CRSF) with the aim to show possibilities of reduction the problem of complicated and important interactions in such composite materials.

Tunnel cross-sections are analyzed applying different material models (linear-elastic and linear-elastic/ideal-plastic) and modes to consider fire loading (equivalent temperature loading and nonlinear temperature distribution). The influence of spalling and the effect of combined thermal and mechanical loading (by consideration of Load Induced Thermal Strains — LITS) on the numerical results is investigated.

Moisture considerably affects the macroscopic material behavior of wood. Since moisture takes effect on wood at various length scales, a computational multiscale approach is presented in this paper in order to explain and mathematically describe the macroscopic mechanical and transport behavior of wood. Such an approach allows for appropriate consideration of the underlying physical phenomena and for the suitable representation of the influence of microstructural characteristics of individual wood tissues on the macroscopic behavior. Continuum (poro-)micromechanics is applied as homogenization technique in order to link properties at different length scales. Building the model on universal constituents with tissue-independent properties and on universal building patterns, the only tissue-dependent input parameters are wood species, mass density, moisture content, and temperature. All these parameters are easily accessible, what renders the models powerful and easily applicable tools for practical timber engineering.

A smooth integration of geometric models and numerical simulation has been in the focus of research in computational mechanics for long, as the classical transition from CAD-based geometric models to finite element meshes is, despite all support by sophisticated preprocessors, very often still error prone and time consuming. High order finite element methods bear some advantages for a closer coupling, as much more complex surface types can be represented by p-elements than by the classical low order approach. Significant progress in the direction of model integration has recently been made with the introduction of the ‘iso-geometric analysis’ concept, where the discretization of surfaces and the Ansatz for the shape functions is based on a common concept of a NURBS-description. In this paper we discuss a recently proposed different approach, the

Finite Cell Method

, which combines ideas from fictitious domain methods with high order approximation techniques. The basic idea is an extension of a partial differential equation beyond the physical domain of computation up to the boundaries of an embedding domain, which can easier be meshed. The actual domain is only taken into account using a precise integration technique of ‘cells’ which are cut by the domains' boundary. If this extension is smooth, the solution can be well approximated by high order polynomials. The method shows exponential rate of convergence for smooth problems and good accuracy even in the presence of singularities.

This paper introduces theoretical model and methods for computationally determining aerodynamic forces of long-span bridges under wind-induced vibration, and emphasis is placed on self-excited aerodynamic force model and numerical identification of model's parameters, flutter derivatives. Through a serious analysis of the thin-plate cross section, the H-shaped section, and the closed box section, the main problems and the key prospects are concluded.

Zero-stiffness postbuckling of a structure is characterized by a secondary load-displacement path along which the load remains constant. In sensitivity analysis it is usually considered as a borderline case between imperfection sensitivity and imperfection insensitivity. However, it is unclear whether zero-stiffness postbuckling is imperfection sensitive or insensitive. In this paper, Koiter's initial postbuckling analysis is used as a tool for sensitivity analysis. Distinction between two kinds of imperfections is made on the basis of the behavior of the equilibrium path of the imperfect structure. New definitions of imperfection

in

sensitivity of the postbuckling behavior are provided according to the classification of the imperfections. A structure with two degrees of freedom with a zero-stiffness postbuckling path is studied, considering four different imperfections. The results from this example show that zero-stiffness postbuckling is a transition case from imperfection sensitivity to imperfection insensitivity for imperfections of the first kind and that it is imperfection

in

sensitive for imperfections of the second kind.

The probabilistic variation of buckling loads of bridges subjected to live load variations is evaluated. For this purpose, the imperfection sensitivity law is extended to live loads. The formulated relation is validated numerically for multiple imperfection pattern vectors subject to normally distributed live loads. A more realistic case is realized based on measured random traffic loads. Computational cost of stability analysis to investigate the probabilistic variation in buckling loads caused by the real random traffic loads has been reduced by utilizing the imperfection sensitivity law.

The study is focused in the parametric instability of the deep-sea risers due to the platform heave motions. As offshore hydrocarbon resources exploration and exploitation moving to much deeper waters, risers play more important roles than before, and face with many technological challenges. The riser resonance can produce disastrous results, such as environment pollution and economical loss. In this work, firstly, the governing motion equation of the marine riser is formulated. Then the stability behavior of the risers with and without nonlinear damping is investigated by employing the Floquet theory. During the numerical solution of the governing equation, the coupling between the modes was considered. Finally, special attention has been paid to the effect of damping for the parametric unstable region changes. The results show that damping can effectively reduce unstable regions. Several useful suggestions are proposed for the design of deep-sea riser structures.

Structural progressive collapse is a great threat to life safety and therefore it is necessary to study its mechanism in detail. Numerical simulation is significant to study the whole process of progressive collapse in structural level. Since collapse is a complicated procedure from continuum into discrete fragments, numerical model should be competent in nonlinear deformation before collapse and breaking and crashing of fragments after collapse. Coupled Finite element-discrete element method on simulating structural progressive collapse is proposed to meet the requirements. Relatively accurate models, such as fiber model and multi-shell shell model, are introduced to construct the finite element model of structure. In the analysis, the failed finite elements will be removed and replaced with granular discrete elements according to the criteria of equivalent total mass and volume so that the impacting and heaping of fragments can be taken into account. The sample with the coupled method shows that this method not only possesses the advantages of finite element method but also simulates the behavior of fragments well.

During shield tunnelling, as segments are cleared off by the shield, annular void occurs between shield tail inner side and lining outer side. The void must be back-filled with grout subsidence to ensure compacted filling, the grout subsidence caused the tunnel uplift. This paper studies the relationship between early strength of grout subsidence and tunnel stability upon shield tunneling. Influence of the rate of tunneling on tunnel stability against uplift is also studied. A longitudinal and transverse calculation model is established to investigate tunnel uplift, which results in grout strength increase. In analysis, safety criteria of structural lining are verified. Finally, relevant construction technological measures are suggested against tunnel uplift for shield tunneling.

Buckling is an instability phenomenon that can occur if a slender and thin-walled plate — plane or curved — is subjected to axial pressure (e.g. inplane compression). At a certain given critical load the plate will buckle very sudden in the out-of-plane transverse direction. The destabilizing force could come from pure axial compression, bending moment, shear or local concentrated loads, or by a combination of these. If the structural element is bulky, the load-carrying capacity is governed by the yield stress of the material, rather than the buckling strength. If instead the element is slender and/ or thin-walled, the buckling strength is governed by the so-called slenderness ratio — the buckling length over the radius of gyration for global buckling of a column or a strut, or the loaded width over the thickness of the plate for local buckling. A special form of instability, that has to be considered with great care in design, is the combined global and local buckling risk of a slender and thin-walled axially loaded plated column — the capacity could be much lower than the two buckling effects analyzed separately. Conventionally, averaged initial stresses due to compression or shear are considered in a plate buckling analysis. Unfortunately, the analytical solutions of initial stresses for a cantilever square plate subject to uniform compression that the initial stresses concentrated at corners and cannot be considered uniform at all. The paper will report on the effects of concentrated initial stress on the global buckling of plates.

With the increasing shortage of water resources in the whole earth, many diversion projects have been constructed to make a better use of water resources in many water-shorting places and the radial gates are need to operate partly for adjustment of discharge in these projects. However, the low head steel gate accident emerges increasingly one after another, due to the instability of radial gate arms under dynamic loading action. In this article, the space frame composed of main cross beams, vehicle beams, arms and some other components is taken as one analytical model, based on the perturbation method and thin-walled structure theory, the dynamic instability region can be calculated by the finite element method. Finally, the method is validated by a comparison with existing project data.

The nonlinear stability analysis of the short box, the long box and the whole wing structure were compared by MARC2003 nonlinear finite element calculation software. The results indicated they were not appropriate to substitute the important part for the whole structure and use the node displacements of the linear calculation as the boundary conditions of the nonlinear analysis. This technique should not be used for the stability design. By comparing the differences of the deflection and the torsion angle between the linear and nonlinear analysis, it was concluded that the nonlinearity seldom influenced the deflection whereas it could remarkably influence the torsion angle. In conclusion, the nonlinear impact must be considered in the torsion stiffness and aeroelastic designs of the wing.

According to retaining walls reinforced by extensible reinforcements such as geogrids and geotextiles, a new slice analysis methodology was developed to analyze its internal stability under horizontal and vertical seismic loads. The slide failure wedge of the reinforced retaning wall was divided into a number of soil slices parrallel to the reinforcements. Based on the single line shape assumption for the critical slip surface of the wall, the equilibrium equations for horizontal forces, vertical forces and moments of each soil slice were established. And then, the recurrence formulas for horizontal and vertical inter-slice forces, reinforcement tensile forces were derived consequently, in which the relationship between the inter-slice forces and the safety factor

FS

of the wall was included. The safety factor

FS

and the vertical bearing capacity qmax at the wall top were obtained by solving those recurrence formulas. This proposed slice method was applied to analyze the seismic stability of one reinforced retaining wall whose height was 10m, and the results were compared with those of strength reduction method. The results show that: this method is simple, practical and good precision in calculation, so it can be used in actual seismic stability design of reinforced walls; the simplifed critcal slip surface is more feasible and convenient for engineering application than the log-spiral failure surface.

The buckling restrained braces (BRBs) might yield but would not buckle whether compressed or tensioned. Thus, BRBs could dissipate in advance the energy of weak earthquake action and protect the structure of main complex from destruction. Meantime, under the action of strong earthquake the BRBs could absorb its energy in large amount, so that the structural safety was improved. The double-steel tube BRBs with was remodeled with additional contact-ring in the middle of their inner tube and at their ends. Finite element numeric simulation was conducted for this kind of BRBs and its result showed that it exhibited fine ability of energy dissipation and force performance.

In this paper, a discrete element model for collapse simulation of RC frame structure is constructed by discretizing the structure into a few elements and spring groups. This model introduces special hysteretic models of connected springs for arbitrary loading path, and also takes into account reasonable failure criteria for springs considering coupling effect of shear and axial force. Based on the discrete element model, a computer program is developed to simulate the whole process of RC frame structures from initial state to collapse under earthquakes. Particularly, the contact-impact problem between discrete elements has been treated with effective measures. Then the program is employed to study the collapse mechanism of a real building in Wenchuan earthquake-hit area, the result of which shows that the simulation program developed based on the new model can realistically simulate the seismic collapse process of RC frame structures.

An accurate local time-domain transmitting boundary, called high-order spring-dashpot-mass boundary (HSDMB), is proposed for modeling the propagation of cylindrical waves in infinite elastic medium. HSDMB is a high-accuracy approximation to the exact analytical transmitting boundary, which can be easily implemented into finite element method and even commercial software, leading to stable and efficient computation. Numerical examples are given to indicate the effectiveness of HSDMB.

This paper proposes a unified formulation for Real time dynamic hybrid testing (RTDHT), which is a structural seismic response simulation method combining the numerical simulation of the

computational substructure

and the physical testing of the

experimental substructure

. By introducing a set of splitting coefficient matrices to the general equation of motion of the structural model subjected to investigation, various seismic testing methods can be formulated, including real time pseudo-dynamic substructure testing, effective force testing and shake table testing. This paper first reviews the seismic testing methods currently used in earthquake engineering with a brief introduction about the RTDHT. Then the unified formulation is presented with a detailed discussion of the splitting coefficient matrices. Hardware components necessary to implement the unified formulation RTDHT are integrated into a unified test platform. While a number of tests were performed in medium scale, a small-scale pilot setup was used in the verification tests. Test results which validated the concept of the proposed unified formulation and the feasibility of the corresponding platform for RTDHS are discussed at last.

Because self-anchored suspension bridge is a floating system, some seismic reduction devices are installed between tower and stiffening girder to reduce the displacements and forces induced by longitudinal seismic wave. Using time history analysis method, the pounding process of a concrete self-anchored suspension bridge with main span of 180m is studied in detail. The influences of different stiffness, free gap, damping coefficient of the device and different frequency spectrum characteristics of seismic wave were considered in the analysis. The parameter analysis reveals that the pounding may increase or decrease the seismic response which is mainly depend on the free gap between the tower and the main girder. The frequency spectrum characteristics of seismic wave have great influence on the displacement, forces and times of pounding. Compared with pounding device, viscous dampers are also researched to reduce the seismic responses of self-anchored suspension bridge and the main influential factors are considered in detail. The conclusions of the study are useful for the practical design of self-anchored suspension.

This paper presents a study of the influence of three different types of seismic input methods on the longitudinal seismic response of a short, three-span, variable cross-section, reinforced concrete bridge. Research progress of the seismic model is introduced briefly. Finite element model is created for the bridge and time history analysis conducted. Three different types of illustrative excitations are considered: 1) the EI-Centro seismic wave is used as uniform excitations at all bridge supports; 2) fixed apparent wave velocity is used for response analysis of traveling wave excitations on the bridge; 3) conforming to a selected coherency model, the multiple seismic excitation time histories considering spatially variable effects are generated. The contrast study of the response analysis result under the three different seismic excitations is conducted and the influence of different seismic input methods is studied. The comparative analysis of the bridge model shows that the uniform ground motion input can not provide conservative seismic demands-in a number of cases it results in lower response than that predicted by multiple seismic excitations. The result of uniform excitation and traveling wave excitation shows very small difference. Consequently, multiple seismic excitation needs to be applied at the bridge supports for response analysis of short span bridge.

The steel-concrete hybrid structure is mainly designed by foreign companies because of its complexity and China backward technology. Its stiffness and mass is non-uniform at vertical direction. The structural model is established with software SAP2000. Its dynamic behavior is studied with mode method. Results show that its mode is complicated. Its torsion response is obvious. Its one way, both way and vertical seismic response is analyzed with response spectrum method. Results show that the shear of its foundation bottom by different seismic action is similar. Its vertical seismic response should be analyzed based on the codes. Its one way and both way seismic response is analyzed with elastic time history method by three seismic waves. Results show that structural torsion response by one way and both way seismic action is similar. The shear average with three time history curves is smaller than that with response spectrum method.

This paper took the railroad through tied-arch bridge with steel box rids as engineering background. Author established 3-D finite element model of this whole bridge with the ANSYS FEM software, and calculated its seismic response by time-history analysis. Then, changed the bridges' type, such as the number of struts, parallel ribs or X ribs and the type of suspenders, analyzed their seismic responses and structural type effect of steel box tied arch bridge to seismic excitation. The results should be used to guide the aseismatic design of the steel box tied arch bridge.

Five different splicing design methods are used to design the columntree web connection, and a method called S-F which has characters of transmits force directly, simple calculation, economic materials consumption is obtained by theories and finite element simulation analysis. In order to consider the influence of several factors such as the thickness of beam and column flange and web, friction coefficient and so on, a series of specimen are obtained by change the parameters of S-F design method with which as the BASE specimen. Finite element simulation analysis in monotonic and cyclic load of these specimen are carried out, at the same time,mechanical behavior of BASE specimen and failure mechanism of connections are analyzed, and the result provides a reference for design and construction of this connection.

Direct displacement-based Seismic design of high-rise buildings considering higher mode effects is realized. The structural natural periods and corresponding modes are obtained by free vibration analysis. Based on the periods, the equivalent displacement of single-degree-of-freedom system for each mode is obtained by displacement response spectra, and the structural lateral elastic displacement of each mode could be determined by “Equivalence Principle”. So the structural lateral elastic displacement can be deduced by SRSS rule. Then, based on allowable storey drift ratio, the structural target lateral displacement of each mode could be determined, and the storey shear is obtained by SRSS rule. The design example shown in Table 3 demonstrates that the base shear considering higher mode effect in serviceability performance level is 2212kN, that is larger than 1975kN which only considering the first mode, so the design results will be more safety. The elasto-plastic time history analysis proves that this method is accurate enough to practical application in building design.

In this article, the rotational components of Ninghe wave was obtained through the translational components of it using the procedure of Matlab software developed by Author, and time history analysis was carried on when the rotational component and the translational components were input to the specially-shaped column frame's space elastoplasticity model which establishes through the ANSYS software simultaneously. The result indicated that the specially-shaped column structure is very sensitive to the rotational seismic component, the effect's enlargement by rotational components should be considered fully when the specially-shaped column structure was designed, and enlarge the frame's seismic safety.

Underground construction at densely populated downtown may confront with reconstruction in existing building. Therefore, mechanical performance of building structure after such reconstruction is the main issue, especially under earthquake. In this present paper, SSI effect is discussed. Dynamic models are built to investigate whether the existing substructure can behavior as the fixed foundation to support the up-structure. Seismic assessment based on dynamic analysis of these structures in two situations, that is, before reconstruction and after it. To account for the response of complicated building structure, software package ETABS are applied to set up three-dimension numerical model. Investigation focuses on typical structural members and drift of reformed structural under seismic inputs.

A single wharf segment tends to behave as a simple 1-DOF structure under transverse component of seismic excitation. Main complexities arise from the significant torsional behavior under longitudinal component of seismic excitation. The objective of seismic analysis is to estimate target displacement at critical piles under transverse and longitudinal components of seismic excitation applied simultaneously. This demand can be done by using Multi-mode Spectral Method (MSM) which is a standard one used in most seismic codes. This paper presents a simplified method, called Equivalent Single mode Spectral Method (ESSM). This method determines target displacement by multiplying the displacement induced by transverse component of seismic excitation and a factor, called Displacement Amplification Factor (F

a

), which accounts for torsional components of response and multi-directional effects of seismic excitation. The proposed equations of F

a

were from a parametric study using 2520 wharf examples with different conditions of soil and structure. In this parametric study, pile-soil interaction was represented by the Winkler spring model, nonlinear force-deformation response of springs was determined based on Matlock's p-y model for soft clay under cyclic loading and MSM was used as a main tool for seismic analysis. The study showed very good fits between displacements resulted from ESSM and that resulted from MSM.

As a new nonlinear science, fractal theory is investigated and applied widely in many complex fields, such as seismology. Today there have been many research results to prove that seismic waves have fractal characteristics, while the influence and significance of the fractal is neglected calculating earthquake action of practical engineering design. Seismic wave is fractal time series data, and the fractal dimensionality of it is a magnitude which can characterize the degree of the data enriching the time amplitude plane. In this paper, it was pointed out that the fractal dimensionality value also should be as one of the parameters of the seismic waves from researching on the design response spectrum curve. Using an improved ‘box counting method’, this study was carried out to calculate fractal dimensionalities of a set of famous ground motion records in different site conditions and basic intensities. And some characteristics of fractal dimensionalities were introduced though contrasting and analyzing. Furthermore, four influencing factors were illustrated, which can impact the magnitudes of fractal dimensionalities of seismic waves.

Nonlinear dynamics theory and chaotic time series analysis are suggested to investigate the nonlinear characteristic of near-fault ground motions and structural seismic responses in this paper. Based on the power spectrum analysis and principal component analysis, it is illustrated qualitatively that the acceleration time series of ground motions have chaotic property. Then, the chaotic time series analysis is applied to calculate quantitatively the nonlinear characteristic parameters of 30 acceleration time histories of near-fault ground motions. Numerical results show that the correlation dimension of these ground motions is fractal dimension with the value 1.0–4.0, and their maximal Lyapunov exponent is in the interval 0-2.0. The average maximum Lyapunov exponents between the ground motions with rupture forward directivity and fling-step effect are close, while those values of non-pulse ground motions are smaller. Moreover, the earthquake ground motions present the chaotic characteristic rather than the pure random signal. Finally, the chaotic feature of seismic responses of single degree of freedom systems subjected to ground motions is revealed by using chaotic time series analysis.

The procedure of random vibration analysis of linear structure subjected to spatial variation ground motion was deduced. A linear continuous beam subjected to spatial variation ground motion was established; By using the Claugh-Penzien self power spectrum model and Harichandran-Vanmarcke coherence function model, the influences of distance between supports, system damping ratio, and site condition on structural mean square response were researched, the results of parameters studies are useful for further studies.

The strength reduction factor spectra of constant ductility factor for bidirectional ground motions is developed by considering the multi-component earthquake excitation and coupled characteristics of structural response, which is defined as the ratio of the maximum displacement response in the same principal axes direction of a single-mass-system with two translational freedoms along its perpendicular principal axes when subjected to two-and one-dimensional ground motions respectively. The effects on nonlinear response of systems under bidirectional earthquake excitations are discussed based on statistic analysis of 178 recordings for hard site, medium site and soft site. By the sufficient statistic analysis, the simplified model of strength reduction factor design spectra of constant ductility factors is established, which is the foundation for forming the inelastic design demand spectra for structures subjected to bi-directional ground motions.

A great many large dams with high seism have been built and will be built in the northwest and southwest regions in China. As large dams have great significance for the national economic development, the aseismic safety evaluation of large dams is an important part of earthquake engineering. The aseismic safety assessment criteria of dams based on the probabilistic method has been an important trend in the safety research of hydraulic structure in recent ten Year>s. Based on the gravity dam, the linear elastic mode-superposition response spectrum method is used in the seismic response; the dynamic and static combination method is discussed. The method of seismic dynamic reliability analysis of gravity dam is also established using the stress coefficient method and Monte-Carlo simulation method. The point strength reliability in the dam and the seismic sliding stability reliability can be calculated via this method. It is simple, convenient and efficient.

Dam-Reservoir system subjected to earthquake is a nonlinear system regardless of the dam body model used (linear of nonlinear) because the fluid equations are always nonlinear. Therefore, transient analysis of Dam-reservoir system subjected to earthquake ground acceleration is necessary for realistic analysis. In this study, Dam-reservoir interaction under earthquake load is modeled by utilizing couple finite element equation. The iterative computing of two-way coupling method is used to solve this couple equation. In this solution, the fluid and solid solution variables are fully coupled. The fluid equations and solid equations are solved individually in succession, using the latest information provided from another part of the coupled system. Following from this, the method was applied in analysis of Sonla concrete gravity dam constructed in Sonla province, Vietnam. The methodology introduced is very convenient and can be easy implemented in the finite element program ADINA with regard to fluid-structure interaction modules.

In order to depict seismic response of a newly-built shield tunnel used for water supply and its extinct features during earthquake, a three-dimensional numerical simulation method for large-scale seismic response of tunnel structure is proposed with the character of fully approximating to the reality. The development of appropriate crucial theories and methods are briefly described, including explicit finite element algorithm, time step control and equivalent connecting method between local refined model and integral model. Then the three-dimensional analytical object is set up from geometrical model to finite element model, which consists of surrounding soils, shield tunnel segments, bolts, and many other entities. This model could consider dynamic hysteretic nonlinear behaviors of soil, contact interface between soil and tunnel, contact interface between bolts and segments; and the contact interfaces between segments. Final calculation is successfully completed on a high-performance computer. According to the calculation results, the whole dynamic tendency of shield tunnel are achieved, which reveals the interaction and distortion of the foundation soil-shield tunnel system under seismic loading. Consequently, it provides a practical method and meaningful data for the seismic design and analysis of tunnel structure.

The polynomial interpolation acceleration method for time history analysis is presented, in which accelerations between several equal neighboring time steps are assumed to be polynomial function of time. In term of Taylor deployment theorem, with the increase of degree of polynomial, higher order precision of the solution of dynamic equation can be achieved thus wider time step can be used to solve the dynamic equation with truncation error in the acceptable limit. However, when higher degree of polynomial is used, the stabilization field of the method narrow down, which leads to restriction of the time step size. Once time step is larger than the limit of smaller convergence field, the transferred error will be magnified many times and results in the failure of solution. Numerical analysis shows that the higher order polynomial interpolation acceleration method unnecessarily leads to wider acceptable time step. Stabilization field and convergence accuracy taken into account, the square acceleration method is superior to linear and third-degree polynomial acceleration method.

An approach to analyze vibration of beam with arbitrary sections is presented. This element formulation employs element equilibrium relationship to obtain an accurate representation to internal forces of a beam. The stiffness matrix and mass matrix are derived for the proposed beam element. Verification example demonstrates the accuracy of this formulation and its ability to vibration analysis of beams.

By applying overlapping mesh, this work simulated vortex-induced vibrations (VIV) of low-mass-damping cylinder. Because of no need to re-mesh on the whole computational domain, but to find donors for nodes on the boundary of sub-domain, time and CPU resources were saved dramatically. We found that the transverse amplitudes increased by approximately 30% in the resonance area when took streamwise degree of freedom into account. But the transverse amplitudes had no change outside of the resonance area. In the range

m

* = 1.0 ~ 40, the ratios of streamwise amplitudes to those of transverse increased as

m

* decreased, especially as

m

*<2.6, the ratios would be greater than around 10%; moreover, the phase angles between streamewise displacements and transverse displacements descended as

m

* ascended.

The numerical simulation technology for structural impacts is used to develop the equivalent static loading for design of bridges against ship collisions. FEM models of five ships whose DWT vary from 3000T–50000T have been developed for numerical collision simulations using the software, LS-DYNA. Time histories for ship-rigid wall collisions are obtained and three kinds of equivalent static loading, the maximum collision force, the local average collision force and the global average collision force are defined. The relationship between the equivalent static loading and DWT, the collision velocity of a ship are established. Modification factors are introduced to consider the effects of geometry of a bridge foundation on the equivalent static loading.

Shanghai Bridge over Yangtze River is a steel cable-stayed bridge with a main span of 730m and a centrally-slotted twin-box deck. The equivalent aerodynamic admittances with and without signature turbulence effect were identified at first for the windward and leeward deck boxes, respectively, via sectional model wind tunnel tests of force measurement, and fitted using proposed model functions of fraction (series). The buffeting responses of the bridge with and without signature turbulence effect were then analyzed using a CQC method in frequency domain, where, the buffeting forces on the windward and leeward deck boxes were separately modeled. The analyzed responses were then compared with those obtained via full bridge aeroelastic model test. The results show that the calculated buffeting responses using measured aerodynamic admittances approach well to the tested results, and the signature turbulence exerts almost no effect on the buffeting responses at the wind speeds higher than 10m/s, but fairly significant influence that at lower wind speeds about 7m/s. This means that the signature turbulence will not prick up the strength issue of bridge structure, but may significantly aggravate the fatigue issue of bridge structure due to buffeting and vortex-excited resonance at lower wind speeds.

Based on the theory of turbulence and molecule kinetics, an extended Lattice Boltzmann equation (ELBE) is derived to solve turbulent flow, in which sub-grid turbulence model is introduced to simulate vortex viscosity as well as turbulence relaxation time to modify the normal LBGK equation. Further more, the ELBE is applied to predict aerodynamic forces and vortex shedding frequency of bridge truss girder, and an equivalent two-dimensional model is studied to solve truss girder considering block ratio.

As two computational fluid dynamics (CFD) simulation methods, detached-eddy simulation (DES) and large-eddy simulation (LES) are compared in a turbulent channel flow simulation at Reb=2800. The Navier—Stokes equations are solved with three different grid resolutions by using a co-located finite-volume method. Spalart-Allmaras model dynamic model and are implemented in DES and LES, accordingly. DES acts as a wall-modeling of LES and functions powerfully as a near-wall treatment for LES technique, though it failed to predict the near wall turbulent structure as expected. The results of LES with the finest mesh compared well with direct numerical simulation (DNS).

A dynamic constitutive model for reinforced concrete based on micro-plane model M4 for plain concrete was presented. The model is established based on two hypotheses as strain being parallel coupling and macro stress being superposition of those on all microplanes. The constitutive model of Cowper-Symonds considering strain rate effect is adopted for steel. This model is adapted for explicit computational algorithm. This model is calibrated and verified by comparison with test data.

In this paper, finite element models which couple Ford F800, semi-rigid and flexible guardrail together in program ANSYS/LS-DYNA were established in order to probe into the feasibility of applying cable flexible guardrail learning from the structural type of semi-rigid guardrail on East-sea bridge to bridge. The result of numerical simulation shows that it is feasible to apply the flexible guardrail structure to bridge guardrail, while guide behavior and safety of flexible guardrail is worse than semi-rigid guardrail.

A new Bridge-Vehicle interaction model based on finite element method with considerations on both the randomness of excitation forces and system parameters is given in this paper. The random properties included in the proposed model are assumed to be non-Gaussian. The Karhumen-Loéve expansion and polynomial chaos expansion are employed to form a framework for the non-Gaussian processes and the stochastic equation of motion of system is transformed into a set of deterministic differential equations which can be easily solved by using a numerical method. The proposed method is compared with Monte Carlo method in numerical simulations with good agreements. The mean value and variance of the structural responses are found very accurate even for the case with large system uncertainties and excitation randomness.

More and more mega-frame structures are extensively adopted by the whole world, because it has the good flexible layout and the good whole space property. But study on dynamic interaction of mega-frame structure is not systematical. This paper calculates the dynamic interaction of the mega-frame-raft foundation-sand gravel soil structure under seismic waves with finite element method. And the numerical calculation includes five projects and contraposes all kinds of factor including: the interaction, the hypo-frame, the model about raft foundation and the thickness of raft foundation. The natural vibration frequency of mega-frame structure and the maximum displacement of all levels are studied. The interaction action change the dynamic characteristic of the whole mega-frame structure, for example, the natural vibration period is extended, the vibration mode is altered and the maximum displacement of the top floor is increased. The results given by the paper might be a significant guide for the interaction theoretical analysis and the engineering of mega-frame structure.

The ultimate span length of cable-stayed bridge has been an interesting issue among bridge engineers for a long time. Although knowledge about the span limitation is growing, little is known about the difference of structural mechanical performances among cable-stayed bridges with even larger spans. Four bridges with main span length from 1,000 to 2,500m were preliminarily designed and calculated, with their components and main parameters adopted based on existing long-span cable-stayed bridges such as Sutong Bridge. The bridge models with the spans from 1,000m to 2,000m can meet requirements of strength, rigidity and stability, but in-plane stability of the 2,500m model can not be ensured.

This paper addresses the aerodynamic effect on the nonlinear oscillation, particularly parametric vibration of cables in cable-stayed bridges. A simplified 2-DOF model including a beam and a stayed cable is formulated first. Response of the cable under global harmonic excitation which is associated with wind speed is obtained using multiple scales method. Via numerical analysis, the stability condition of the cable in terms of wind speed is derived. The method is applied to a numerical example and a real cable-stayed bridge at Hong Kong to analyze all the cables of the bridge. It is demonstrated that very large vibration at one of the longest cables in the middle span of the bridge can be parametrically excited when the wind speed is over around 140 km/h.

VIV (Vortex-induced vibration) of a stay cable subjected to a wind profile is numerically simulated through combining CFD (Computational Fluid Dynamics) code CFX 10.0 and CSD (Computational Structural Dynamics) code ANSYS 10.0. A stay cable with the inclined angle of 30° is used as the numerical model. Under a profile of mean wind speed, unsteady aerodynamic lift coefficients of the cable have been analyzed in both time-domain and frequency-domain when VIV occurs. The results indicate that the lift coefficient wave response of the stay cable under a wind profile is different from that of an infinitely long cable under a uniform flow in water (i.e. without consideration of profile) obtained by direct numerical simulation. Cable oscillations can severely influence the unsteady aerodynamic frequencies, and change flow field distribution near the cable and influence the vortex shedding in the wake.

The aerodynamic interference effect between wind turbine blade and tower is very common in the wind turbine structure, so the study of the physical mechanism of the interference effect is both of important practical interest and profound academic interest. Firstly, the full two-dimensional Navier—Stokes algorithm and the k-ω SST turbulence model were used to investigate incompressible viscous flow past the wind turbine NACA 63-430 airfoil and tower in detail. The flow physics in the two-dimensional analysis was clarified by the aerodynamic loads acting on the wind turbine tower. The numerical results under the blade-tower interference effect and the results under a single tower were compared in view of lift and drag coefficient time histories. Furthermore, the effect of the three-dimensional blade rotation on the wind turbine tower was simulated based on the rotational sliding mesh technique and the effective large eddy simulation (LES) methods. The force perturbation acting on the tower under the blade rotational effect was clearly studied. As a result, the numerical results are very used for understanding the physical mechanism of the aerodynamic interference effect between the wind turbine blade and tower, which will be helpful for guiding the structural design of the wind turbine tower.

Windborne debris is one of the most important causes of the envelop destruction according to the post-damage investigations. The problem of windborne debris damage could be summarized as three parts, including windborne debris risk analysis, debris flying trajectories, and the impact resistance of the envelopes analysis. The method of debris distribution was developed. The flying trajectories of compact and plate-like debris were solved by using numerical method according to the different aerodynamic characteristics. The impact resistance of the envelopes was analyzed. Besides, the process of windborne debris damage analysis was described in detail. An example of industrial building was given to demonstrate the whole method by using the observed data of typhoon CHANCHU (2006). The method developed in this paper could be applied to risk assessment of windborne debris for structures in wind hazard.

In the current civil engineering field, the characteristics of typhoon wind field are chiefly studied through field measurements and simple numerical simulation of typhoon engineering model. This paper will bring in the sophisticated non-hydrostatic version 3.7 of American Pennsylvania State University (PSU) — National Center for Atmospheric Research (NCAR) Fifth-Generation Mesoscale Model MM5 in meteorology to simulate typhoon in order to apply in disaster prevention and reduction of civil engineering. Taking the strong typhoon Wipha (0713) as a example, the quadrupled nesting grid with spacing of 27 km, 9 km, 3 km and 1 km in MM5 is applied to the typhoon to obtain the highresolution, three-dimensional wind field. Meanwhile the effectiveness and applicability of MM5 model are evaluated by the typhoon yearbook of China Meteorological Administration. Then the engineering characteristics of typhoon wind field in the boundary layer, such as horizontal wind speed and wind profile are presented and briefly analyzed from the respect of physics essence.

Modern wind turbine blades become more and more flexible with its increasing size. Under extreme wind excitations, the considerable blade deformation may result in large deflection at blade tip. This paper proposes a Variable Step Deformation Difference Method (VSDDM) to analyze the nonlinear blade structure. The VSDDM has the advantages of distinct concept, easy to understand, and simple to program. Owing to the linear solution always bigger than the nonlinear solution, the design would be conservative based on the linear solution.

This paper proposes a new procedure for simulation of random wind velocity field with only a few random variables. The procedure starts with decomposing the random wind velocity field into a product of a stochastic process and a random field, which represent the time property and spatial correlation property of the wind velocity fluctuation respectively. Then the stochastic process for wind velocity fluctuations is represented as a finite sum of deterministic time functions with corresponding uncorrelated random coefficients by an innovative orthogonal expansion technology. Similarly, the random field is expressed as a combination form with only a few random variables by the Karhunen-Loeve decomposition. It provides opportunities to use probability density evolution method (PDEM), which had been proved to be of high accuracy and efficiency, in computing the dynamic response and reliability of general linear/nonlinear structural systems. A numerical example, which deals with a MDOF frame structure subjected to wind loads, is given for the purpose of illustrating the proposed approach.

The modern tall buildings, slender and lightly damped, are vulnerable to the dynamic wind action. Vortex induced vibration, a typical crosswind excited vibration, is significant for the flexible structures and complex in the mechanism. In order to predict the vortex induced response of a super tall building with a SDOF empirical model, wind tunnel tests were carried out with an improved aero-elastic model according to the similitude. Based on the experimental data, the vortex-excited force parameters were determined and the characteristics of vortex induced vibration were investigated in some details. The time history of acceleration at the lock-in wind speeds range of the tall building is then obtained through Runge-Kutta method and the results show good agreement with measurements.

The wind pressure on the surface of a cooling tower with gas flue is compared with the corresponding cooling tower without gas flue through wind-tunnel testing, then the characteristics of wind pressure distribution around the flue is investigated. The strength and buckling nearby the flue are analysed with finite element software. It is found that stress concentration nearby the flue is very obvious, and its safe factor of local buckling is much less than the value without flue, which makes unsafe place to transfers from top of the tower to the area near flue. The corresponding schemes of reinforcement on the basis of this situation are proposed, and static performance of each scheme is compared for selecting the better one.

The two-dimensional numerical simulation of the vortex induced vibrations of four cylinders in an in-line square arrangement is investigated at low Reynolds number in this paper. The mean and fluctuating aerodynamic forces, Strouhal number (St) and vortex shedding pattern in the wake for each cylinder are analyzed with the six spacing ratio L/D changing from 2.5 to 6.0. The results indicate that the mean drag force and the fluctuating lift forces and the transverse displacements of the upstream cylinders are relatively larger than the downstream cylinders, and the downstream cylinders usually undergoing serious fluctuating streamwise displacement. The dominant frequency of drag coefficient is equal to St of downstream cylinders for all spacing ratio, so the simultaneous resonance in the in-flow and cross-flow directions may occur for downstream structures of multi-body oscillating system. The streamwise oscillation of downstream cylinders which is free to move in two degrees of freedom could be as large as 0.75 diameter, and the maximum transverse amplitude of upstream cylinders may achieve 0.82 diameter, is much higher than the transverse amplitude of flow around a single cylinder at same parameter setting.

The large finite element software ANSYS and the CFD software FLUENT are used to analyze the dynamic response of TLP's tendon in current load effect. ANSYS is used to figure out the hydrodynamic forces of tendon. The hydrodynamic forces are transferred to the tendon through flow field. The tendon is considered as two tips end-fixed and its dynamic response is solved in different pretensions. The results show that the tendon has realizing transverse vibration and little vibration in current direction, but the realizing drift in current direction must be considered.

Investigation on flutter stabilization and its mechanism of long-span suspension bridges with box girders by using central air vent, which resulted in central-slotted box girders, was introduced in this paper. With the experimental results of wind tunnel tests, the minimum values of critical flutter speeds for certain slot width were always measured at the +3° angle of attack. Based on the concept of full-degree coupling analysis, stabilization mechanism was found with the references of aerodynamic damping and degree participation. The characteristics of main vortices around the decks in the flow field obtained from Particle Image Ve-locimetry (PIV) wind tunnel tests and numerical calculations were finally investigated.

ANSYS software was used to analyze the influence on nature frequency of cantilever structure with water inside or outside. The calculation frequencies of this paper were compared to those of the theoretical formula, and the results are found to be the same. It comes to a conclusion that the internal and external hy-drodynamic pressure has great influence on nature influence of structure. It cannot be neglected especially to slender structure and thin-walled structure.

In this paper a computational method for evaluating moisture induced stresses in timber connections is proposed. A 3D orthotropic-viscoelastic-mechanosorptive model for wood is implemented in the Umat subroutine of the FEM code Abaqus and a moisture-stress analysis is performed. Some dowel-type connections are computationally analyzed under sustained mechanical loads and natural humidity conditions.

This paper focuses on a strength analysis of the timber structure of Penglai Pavilion. A finite element model is presented to evaluate the dynamic characteristics and strength of the timber frame structure. Some constructive suggestions are presented to be a basis for strengthening the ancient timber Pavilion.

An approach to the numerical simulation of wood drying based on the finite element method is presented. Wood, as a hygroscopic, strongly anisotropic porous material, must be dried before being used for a practical purpose. Wood drying leads to a combination of vapor, bound water, and free water movement. A numerical simulation of the drying process of wood involves three fundamental phenomena: heat transfer, movement of moisture, and mechanical deformation. Liquid flow due to capillarity, water vapor and air (diffusing and convection in bulk gas flow), and bound liquid diffusion are basic mechanisms of mass transfer in wood. The aim of the paper is to present a numerical model of coupled heat, moisture and air transfer in pores of wood subjected to high temperature drying conditions. Heat and moisture exchange take place between wood and drying medium, and coupled problems can be described from a macroscopic viewpoint of continuum mechanics. Benchmark tests of a 3-D model under Dirichlet and mixed type of boundary conditions are used to account for the coupling among temperature, moisture content and gas pressure.

Dowel-type connections of wood are characterized by a complex load-bearing behavior and failure mechanism. For prediction and understanding of this behavior, numerical simulations of double shear dowel-type connections are introduced. The failure of the wood components and the steel fasteners are modeled and appropriate material formulations are introduced. The analysis of the numerical calculation and verification shows the suitability of the model to predicting the load-carrying capacity and the failure mechanism.

In order to protect Chinese ancient buildings, Shen-Wu Gate in the Forbidden City is taken as an example to study its aseismic character under 8-degree of seldomly occurred earthquake by pushover analysis. Based on constitution of tenon-mortise joint and tou-kung, finite model of the structure is built. By modal analysis main mode of the structure is obtained, based on which level loads is applied to the structure to carry out pushover analysis. Results show that mode 1 in y direction is main mode of the structure. Under 8-degree of seldomly occurred earthquake the structure produces displacement which is less than permissible value. Under earthquake plastic hinges mainly appear near bottom tenon-mortise joints. However the upper part remains intact because of isolation of tou-kung.

In order to protect Chinese ancient buildings, a wooden building in Guangyuan city in China is taken as an example to study aseismic effects of masonry walls to wooden constitution by Wenchuan earthquake. By ANSYS PROGRAM, semi-rigid character of tenon-mortise joint as well as contact between wooden constitution and walls are simulated. Then finite element model of the building is built. By comparison method, vibration modal as well as dynamic responses of the structure before and after considering wall effects are studied. Results show that after considering embedding effects of masonry walls, main mode of the ancient building is mode 1 in x direction. Under Wenchuan earthquake the wooden constitution produces lower displacement but higher acceleration values.

In each traditional timber structure in China, the mortise and tenon are one of the most important parts, because they connect differential components as a whole more big component. Of course, they made also beam and column as a frame. To conveniently utilize FEM for computing timber structure, mortise and tenon are considered as relative independent configurations, as well as the part which should be paid more attention. Because the connection between mortise and tenon is semi-rigid deformation behavior, rather than full rigid or ideally pinned connection, it is a key to accurately approach property of semi-rigid stiffness of mortise and tenon during the numerical simulation, for expressing the property of whole actual wooden structure. This study summarizes the research of the development of semi-rigid element and establishes easy computing and analytic finite element model of mortise and tenon. In addition, parameters of the model have been obtained by comparing numerical result applied MSC FEM software and the consequence of crossing timber frame experiment, based on the response surface method and optimize interactive theory. The analysis and the result mentioned above could be applied on the study of other entire large-scale ancient wooden architecture.

Concrete slabs are among the most common structural elements and their stability under blasting load has received the most attention recently. Therefore, to investigate the concrete slab response to blasting loads is a very significant project. In this paper, 2D dynamic numerical models for concrete slabs subjected to explosive loading are developed through the use of AUTODYN code and the following two issues are investigated: (1) material statuses of concrete slab as a function of time from the exploding source; (2) slabs with different layers of materials under dynamic loading. The objective is to compare their behaviors and find out useful tips to improve the blast-resistant capacity of concrete slabs. In the simulation, RHT failure model which considers damage accumulation, strain-hardening and strain rate are employed to determine concrete material statuses. The simulation results shows that two damage zones of different characters occur in the plain concrete slab and the damage statuses of layered slabs are extensively different from that of plain slabs.

The analysis method about concrete column to resist vehicle bomb is proposed in this paper. The example how to use this method is shown using LS-DYNA software. The loading rate and boundary condition's effects on the analysis result are studied. The concrete columns can not be destroyed totally because of the vehicle bomb's blast load, there is the residual capacity in the column after the blast loading. The method provided in this paper is suitable to study the concrete's residual capacity and damage factor because of vehicle bomb. The calculated residual capacity can be affected by the loading rate, but the damage factor is almost the same if the loading rate is kept unchanged when the original capacity and the residual capacity are calculated. The simple single column model can be used when studying the column to resist vehicle bomb. The study result in this paper can be taken as the reference for analyzing and researching the column to resist vehicle bomb.

The determination of pressure produced by blast loads was carried out with the aid of hydrocode LS-DYNA. The simulations of the blast wave both in air and encountering a solid target were discussed. Numerical results were compared with those obtained from the empirical expressions for different scaled distances. The material parameters of explosive and air were studied. In order to accurately evaluate the incident pressure distributions within building structures, the Arbitrary Lagrangian Eulerian (ALE) coupling was adopted to simulate the blast loading and its interaction with the structure. The blast wave was predicted by the Jones-Wilkins-Lee (JWL) equation of state for high explosives. The effect of mesh size on pressure evaluation and the appropriate boundary conditions were also studied. The results show that the material parameters and the numerical algorithm are applicable for the blast loads determination.

The numerical simulation for responses of reinforced concrete slabs under blast loads with the finite element program LS-DYNA was performed. A quarter of the three-dimensional solid model was established for the reinforced concrete slab. Blast loads were imposed on the surface of the slab. The H-J-C model for concrete was employed, taking into account the damage and the strain rate effect. The J-C model was employed to model the steel bar, taking strain effect into account. And the parameters of J-C model were derived by means of regressive analysis of experimental data conducted in our research group. The erosion technique was adopted to model the spallation process. The comparison result between numerical simulation and the test shows that the numerical simulation is an appropriate way for the study of responses of reinforced concrete components under blast loads.

Due to the confined space in a station, the internal blast effects are obviously different from the air blast. In order to design and retrofit a subway station to resist an internal blast, the distribution of blast loading and its effects on structures should be acquired firstly. The explicit dynamic nonlinear finite element software —ANSYS/LS-DYNA was used in this study. It briefly introduced the material constitutive models and boundary conditions used in the simulation. The numerical model of a typical two-layer and three-span frame subway station is established. Then two cases of different location of explosives were considered to analyze the dynamic responses of the structure. The effective plastic strain, displacement and total energy of the structure in the two cases were presented and discussed.

The present paper aims to quantify the relation between structural temperatures and its natural frequencies via thermodynamic approach. A simply-supported beam was tested in laboratory. The temperature values at different points were recorded continuously in one day, together with a series of forced modal testing to extract its frequencies. A thermodynamic model is established to estimate the temperature distribution of the slab and compared with the measurement data. The frequencies of the slab are calculated, and the variation of frequency with respect to temperature is established and verified by the experiment. The present study provides a new approach to investigate the environmental effect on structural responses.

This paper introduces the experimental study on vibration behavior of 4 full scale cold-formed steel composite floors. The research is focused on the fundamental frequency of composite floor, which considering the influence of screw spacing and rigid blocking under different loading cases during normal use. The test apparatus and methods are introduced in details. The finite element analysis model of cold-formed steel composite floors is set up to study the vibration behavior. Finite element analysis results are close to those of the experiments. The results show that the flexural rigidity of composite floor can be improved by changing the spacing of screws. The fundamental frequency of composite floor with large spacing of screws, that connect profiled steel sheet and the flange of joists, is smaller than the composite floor with small screw spacing. The flexural rigidity and frequency of composite floor can be increased by setting rigid blocking at mid-span of adjacent joist of the composite floor and bearing rigid support. It is suggested that the fundamental frequency of cold-formed steel concrete composite floor should be more than 8 Hz.

A method of reverberation ray matrix (MRRM) is developed for transient response analysis of space structures composed of bar elements taking into account of damping effect. Based on the forms of exact solution in frequency domain for axial, bending and twisting wave motions in beam structure, displacements and internal forces in the beam can be expressed by arriving and departing vectors, which are determined by evaluating a reverberation ray matrix. The IFFT algorism is finally used to derive transient response of the structures. As an application, a framed structure under impact load is considered as computational model. Comparison with results from FEM shows a high precision in computation for the method. The result shows that high-frequency portions of the response are weakened by effect of damping.

The bending-bending-torsional coupled undamped free vibrations of axially-loaded Euler-Bernoulli beams with bi-asymmetric cross sections are studied in this paper; and the warping effect is considered. The reference point is chosen coincident with the mass center of the cross sections of the beam and reference axes are chosen parallel to the geometric axes of the cross sections; geometric parameters of the cross-sections of the beam are determined with respect to geometric axes. The numerical results show the accuracy and effectiveness of the present method, and the effects of axial load and warping rigidity on natural frequencies are discussed.

In this article, we utilized the lumped damage mechanics method to implement the damage analysis to the 3D frame structure under impulsive load. First, take the damage parameters as the interior variable of the system, and based on the finite unit, combine continuum mechanics, fracture mechanics and plastic hinge to analyze the mechanical behaviors of the structure, and finally implement numerical simulation analysis to the frame structure with two layers, and compare the result with the computation result of ABAQUS to validate the feasibility.

This paper is devoted to investigate the dynamic response of a semirigid pavement under impact loading. Both experimental and numerical approaches are proposed. The experimental approach is conducted using a suitable instrumentation of the pavement. For numerical modelling, the finite element method is applied to simulate the elasto-dynamic response of the pavement.

This paper presents a method for the elastic analysis of vertical loaded single pile in multilayered saturated soil. Based on Biot's consolidation equation, plane strain assumption is applied to research pile-soil interaction in saturated soil. The analytical solution of impedance function of soil is obtained. Combining with a transfer-matrix formulation in the case of multi-layered saturated soil, the analytical solution of vertical impedances of pile are determined. The results of this method are compared well with the existing solutions in the literature. A parametric study for a two-layered saturated soil is further presented to show the effects of layered soils on the behavior of a single pile.

With the effect of vehicle-bridge coupling considered, the local dynamic response in deck slabs of concrete box girder bridges are analyzed. The mathematical model assumes a finite element representation of the slabs with shell elements. And the vehicle simulation uses a 3 dimensional linear vehicle model with 7 independent degrees of freedom. A well-known power spectral density of road pavement profiles defines the deck surface roughness for Good and Poor roads respectively. Response data are produced on concrete highway bridge decks made of straight box section girder. In this way, a parametric study is conducted to analyze the effects of factors such as road surface roughness, vehicle speed, and bridge damping on the bridge dynamic amplification factors (DAFs). Results are presented to verify the extension of the local dynamical effects on concrete box girder decks with different working condition. From these results some general conclusions have been drawn.

The steady-state response of a beam on an elastic foundation subjected to a moving structure with constant speed is studied. The moving structure is assumed as an elastic Euler-Bernoulli beam with distributed stiffness and inertial effect considered in the analysis. The integral transforms methods are introduced to transform the partial differential equations to algebraic equations. Then parametric analyses by numerical examples are performed.

Applied the stochastic optimal strategy to introduce building structure response to wind and earthquake excitation. First deduced the wind load model in the frequency domain and the wind load model in the time domain, then listed a set of stochastic differential equations based on the power spectral matrix of the discredited fluctuating wind field. For earthquake, represented random processes in the frequency domain by their power spectral density functions. For a structure involving many degrees of freedom, the mode-superposition method is usually adopted for determining the dynamic response of the structure under all random excitation.

Inspired by the hunting behavior of woodpeckers, a new tapping-scan method is proposed for the damage detection of bridge structures with high accuracy. The whole detecting system is a scanning vehicle integrated with tapping devices. With this system, the damage detection can be applied without disturbing the traffic on the bridge. To enhance the detection sensitivity, an analytical solution is firstly deduced to unveil the relation between the vehicle acceleration and the damage. Then numerical simulations are carried out for different damage scenarios. The obtained spectrum of vehicle acceleration is used to locate the damage.

A structure damnification diagnose system method based on radial basis function (RBF)network is put forward which is composed of three networks from finding damaged position to ensuring damaged extent. Preference of remainder force matrix based on vibration equation is bring forward. Its feasibility and validity of the damnification diagnose system are proved through mode simulate analyzing. Take the discontinuity of concrete structure, better modulus parameter can be chosen as input parameter according to different structure of its dynamic characteristic.

The basic principle of curvature modal is discussed, and a mathematical comparison between the vibration mode relative variable quantity and the modal curvature is given. Dynamic test is carried on 9 pieces of RC beams, in which the beam is subjected to an increasing static load in the middle to introduce cracks. After each load step, unloading, and an experimental dynamic monitoring is performed on the beam. Test data is analyzed by means of the system of Data Acquisition Signal Process, and the displacement modal is obtained. The curvature modal is gained from the displacement modal with second order differentiation method.The results show that curvature modal can identify the damage of RC simple-supported beam more accurately, and it is more sensitive to tiny damage. Based on the concept of function total differential, the error transmission formulas from vibration mode to the curvature mode are derived.

The vibrotechnique may be applied to damage identification in civil engineering, but there are some technical problems. The identification precision of displacement mode shape is low; however it of strain mode shape is high. Although the present methods of strain modal parameters can be applied to detect damage location, only very few can rough detect damage degree. Furthermore, the precondition of the methods is that the modal parameters of original structure and damage structure must be obtained. It is very difficult for the original structure. Therefore, the direct index method of damage degree identification (the abbreviation is

I

LSMSA

) is advanced in the paper. It is based on local strain mode shape area of the damage structure. The strain modal parameters of original structure needn't be provided. The polynomial is applied to fit strain mode shape of the original structure. The mathematics models of optimization polynomial degree and

I

LSMSA

are founded. According to theoretical derivation and statistical analysis of numerical simulations, the four characteristics of

I

LSMSA

are obtained. First,

I

LSMSA

presents monotone increasing tendency with increasing damage degree. Secondly, it is independent of damage location. Thirdly, it is independent of the order of strain mode shape. Fourth, it is independent of normalization.

Structural damage detection consists of determining the location and severity of damage in civil structures by using measured parameters. Genetic algorithm is a meta-heuristic computing method for finding approximated global minimums in large optimization problems and has the advantage of probabilistic hill climbing. In this work the improved genetic algorithm is employed to solve damage detection problem in truss type structures using vibration data (natural frequencies and mode shapes). The formulation of the objective function for the optimization procedure is based on natural frequency and vibration mode shapes. Present structural damage-identification scheme is confirmed and assessed using a Finite Element Model formulation (FEM) of truss structure. Results are presented in tables.

To concrete structures, the defects such as cracks in this porous-full material are generated naturally. In service life, these defects in tunnel lining concrete will develop to damages under the effect of carbonization, steel corrode, high water pressure, permeability, etc. Incontrovertibly the generation, development and accumulation of these damages will give deterioration to the performance of the structures in service life. The speciality of the tunnel lining structure vary with that of ground structure determines that the normal damage identification method to ground structure such as bridge, building, chimney etc. is not suit for tunnel lining damage identification. Considering of damage expression, material damage model, and damage identification, here a new approach is proposed for damage identification using monitoring stresses data. In this approach, the expression of forces, stresses, and strains under loads is got through analytic method. Considering of possible damages in tunnel lining structure, using substance damage expression and stress damage expression to concrete structure, the difference values of forces, stresses, and strain can be got between those from analytic calculation and those from local monitoring. These values are used as error function; we can get the minimum value through comparing each other. The minimum value of the error function is the representative of damaged state of the lining structure. Then the integral damage and the damage level of the structure can be identified.

Based on the easy testability and high measure precision of structural frequency, a damage identification method for shear buildings is presented. With frequency being regarded as the function of damage parameters, the homogeneous linear equations with damage parameters as unknowns can be constructed via Taylor expansion. The equations are solved to locate the whole damage location and quantify the severity of the damage. The data used in the method include frequency and mode shape measurement before and after damage. A numerical simulation example using a three-storey sheer structure is given to validate the present method.

The artificial neural network (ANN) models are presented for diagnosing pile in this paper based on the pile integrity test (PIT) also known as low strain dynamic test. The back-propagation learning algorithm is employed to train the network for extracting knowledge from training examples. There are fifty-three input neurons in the network including the PIT response and pile length, cross-sectional area and wave velocity. In order to obtain the pile condition in quantity, the novel technique is proposed containing two back-propagation ANN models. The first is to identify the defect patters while the second to investigate the exact degree of pile defect by computing the change of equivalent cross-sectional area. Training and testing data were drawn from response records of actual piles. The results from the testing phase indicate that the presented method is successful.

This paper focuses on damage control design of SMA dampers in steel frames. A parametric study based on time history analyses is carried out on a frame bridge pier with axial-type SMA damping devices. The parameters examined are design parameters of strength ratio α

F

and stiffness ratio α

K

..Three JRA recommended Level 2 Ground Type 2 ground motions are used as inputs. Design recommendations are suggested following results of the parametric study.

Vibration control of a super-tall frame-shell wall building with connective structure is studied in this paper. According to the natural characteristics of the structure, three kinds of vibration control plans with nonlinear viscous dampers are proposed to proceed vibration control in wind action. The fluctuating wind time-series of the structural forward and reverse Y-direction in 10-year frequency are simulated by improved AR model based on Fourier-transform. The structural dynamic responses of different control plans in wind action are studied, and corresponding vibration control effects are analyzed technically. The results show that the structural wind-induced vibration responses can be controlled effectively by the proposed three control plans, the maximum acceleration reduction of 39.2% can be achieved for point 319 of the top story and then structural comfort induced by wind action is improved greatly. Energy of about 30%–40% input by wind-induced vibration can be dissipated by viscous dampers. So, the effectivity and feasibility of nonlinear viscous dampers in reducing wind-induced vibration responses of high-rise or super-tall structures are fully proved.

To control the amplitude of limit cycle of coupled van der Pol systems, the feedback controllers are designed, the control equations of weakly nonlinear systems are obtained by using the approximate method and the relationship between the amplitude of limit cycle and the control parameter is acquired, hence amplitude of limit cycle can be controlled effectively. The method may also be applied to other coupled van der Pol systems. On some systems, it is difficult to find the function in the amplitude of limit cycle and the control parameter directly. By means of the numerical analysis, we can design effective controllers; therefore can preferably control the amplitude of limit cycle of coupled van der Pol systems.

Firstly, we introduced the structural form intelligent optimization (SFIO) basic theory and the methodological framework including the alternative scheme intelligent producing and innovative, intelligent evaluation, intelligent optimization selection and decision-making, knowledge automatic access, intelligent means, laying a foundation for farther study the SFIO theories and methods. Secondly, we gave a more comprehensive overview of DM techniques in SFIO, the important research results and the latest research progress such as Apriori-based, Bayes-based, ID3-based, NN-based, GA-based, RS-based and fuzzy RS-based algorithm, and their characteristics. These methods can mine FO knowledge from a different perspective, and possess a better complementary. This paper gives more comprehensive overview of the data mining technology in the SFIO.

The design of light-weight structures is a subject of central importance in the development of numerous civil and mechanical engineering products, such as bridges, roofs, and aerospace constructions. Based on matrix operators, a new methodology is established in the present study to design minimum-weight dual-material truss layout structures with curved support boundaries that represent broader engineering applications. To validate the new methodology, logarithmic spirals on a circular support boundary are investigated to determine the radii of curvature along the boundary points. A torsion structure case study is explored to compare deflections with calculated results obtained from the optimality criteria. The solutions are very close to theoretical values.

This work presents the implementation of genetic algorithms in the optimization design of deepwater Steel Catenary Risers (SCRs) with discrete design variables. For deepwater developments, riser system requirements become a significant factor in the cost of the overall oil field investment. Hence, riser design must consider safety before reducing costs. Firstly, three dimensional nonlinear SCRs models were constructed by finite element method; In addition, nonlinear characteristics of soil/structure interaction are also included according to regulations. Secondly, a steel catenary riser is analyzed for several typical ocean environmental conditions to prove the vast potential of the proposed strategy as a design tool; thirdly, SCRs design based on genetic algorithm were applied for given design parameters such as riser thickness, coating properties and constraints. Compared with conventional design method, the optimized configuration not only can cut the cost while satisfied all constraints, but also reduce the maximum von Mises stress. According to the above analysis, the optimization strategy base on genetic algorithm is a useful tool for SCRs design, and that the proposed method for selection of optimum design variables will enable an engineer to identify designs with minimum costs in an efficient way.

Two approaches are examined for seeking the best stacking sequence of laminated composite wing structures with manufacturing constraints: smeared stiffness-based method and lamination parameter-based method. In the first method, minimizing the total number of plies is the objective function at the global level and shuffling the stack of all the layers to satisfy manufacturing constraints is optimized at the local level. The second method introduced in this paper is to use lamination parameters related with out-of-plane stiffness matrix and numbers of ply angle (90, 0, 45/-45) as design variables with considerations of buckling and strength constraints in the top level optimization. Given lamination parameters from top level optimization as objective function for the local level, optimal stacking sequence will be determined to satisfy industrial manufacturing requirements. The results of a three-part wing box example using these two approaches are compared to results from published papers to demonstrate their potencies.

Researches on how to save the design cost of pressure vessel are investigated here, in which the thickness of the vessel and the number of stiffeners are considered as the design variables. This paper presents an algorithm based on hierarchical architecture. It is convenient and feasible to apply stratification optimization method to solve the problem with discrete-continuum mixed variables. At the same time, considering the independence of sample point analysis and used parallel computing, the present software in this paper is of more efficiency and utility.

A framework for solving the multiobjective optimization problems in multidisciplinary design environment is advised in this paper. Based on the collaborative optimization (CO) algorithm, a new system level objective function is advised to minimize relative value between the collaborative objective function and single disciplinary objective function. It eliminates the effect of dimensions and magnitude orders among different disciplinary objective functions. A new subsystem level objective function is developed that includes the disciplinary objective function and the consistency constraint. A new framework of multiobjec-tive collaborative optimization (MOCO) is developed. In MOCO framework, the system level optimizer does not only independently invoke the subdisciplinary analysis tools, but also invoke its subdisciplinary optimizer. The feasibility and reliability of the MOCO are highlighted by the successful convergence of two examples.

In this paper, the passive control approach to three dimensional building structures excited by 2-dimensional earthquake ground motions is presented by using Bi-direction tuned masse damper (TMD) system. The mathematic model of a multi-storey building structure including the TMD system is established and its combined equation of motion is given. The optimization of TMD parameters can be obtained by using the Genetic Algorithm Method based on the object function. The numerical example shows that the presented method is effective and flexible. It may obviously control the translational response and rotational response of three dimensional building structures.

A thermo-mechanical model based on a phenomenological approach is presented for the evaluation of the load-carrying behavior of fire exposed reinforced concrete structures. It is validated by the numerical simulation of fire tests on concrete specimens and of a large scale fire test on a reinforced concrete slab and it is applied to the evaluation of the structural response of a fire exposed tunnel structure.

The paper presents a numerical modeling of Reinforced Concrete (RC) columns under fire and loading simultaneously. It proposes a concrete model at high temperature considering both transient strain and load path, which is an improvement of the concrete model in EC2. The parameters of the concrete model are tuned so that they are suitable for the concrete materials that are commonly found in China. The concrete model is implemented in the FE software SAFIR, which is developed in the University of Liege by Prof. J. M. Franssen for calculation of structures in fire. The paper continues to validate the material models by experimental results of restrained concrete columns under fire conditions.

This paper based on the basic theory of field simulation, analyzed the characteristics of typical subway station through FDS (Fire dynamic simulator), obtained the temperature curve based on the analysis of fire scene, compared and analyzed with the ISO-834 standard temperature curves. Then, calculated the temperature field of the component-section, compared and analyzed the influence of the simulated temperature curve and the standard temperature curve on the component cross-section temperature field.

With using a numerical model proposed by the authors, numerical tests were performed to investigate the effects of thermally cracking process with considering the heterogeneity of material properties on the spalling in concrete exposed to a transient thermal load. The numerical results showed that the thermal cracking is the key factor causing the corner and surface spalling.

The determination of the effective diffusivity of cement-based materials is a point of major importance to control service life of concrete structures. In this contribution, a multiscale model for cement-based materials focusing on the prediction of effective diffusivity is developed, treating cement-based materials as hierarchically organized material separated by three length scales. The comparison with experimental data taken from the literature reveals the non-negligible contribution of gel-pore.

A geometrically nonlinear total Lagrangian meshfree formulation based on the stabilized conforming nodal integration is presented for efficient analysis of shear deformable beam. The incremental equilibrium equation is obtained by the consistent linearization of variational equation. The meshfree shape function is constructed purely based on the initial configuration. Subsequently to accelerate the computation the method of stabilized conforming nodal integration is systematically implemented through the Lagrangian gradient smoothing operation. Both stability and efficiency are gained in the proposed nonlinear meshfree beam formulation. The effectiveness of the present method is validated by two typical numerical examples.

The objective of the presented paper is the ultimate limit state sensitivity analysis of a steel plane frame to input imperfections. The Sobol's variance based strategy was applied for the sensitivity analysis evaluation. The ultimate limit state was solved by the geometrical nonlinear finite element solution. The load-carrying capacity, solved on behalf of the Monte Carlo numerical simulation method, was the output random quantity. Input imperfections were measured, and their histograms have been applied in the Monte Carlo method. In the paper, there are demonstrated the changes of sensitivity coefficients in dependence on system lengths of columns.

This paper focuses on the multi-physical fields' evolution in early age concrete, which has great importance to the work performance and durability of concrete material. This paper presented some simple and comprehensible formulas to connect different multi-physical field of early age concrete. Then a simplified model is proposed to analyze the early age concrete after which the numerical analysis methods are built. We compared the simulated results with the passively confined concrete experiments data and find they agree well, which proved this method feasible and effective.

It's a most common dynamics phenomenon of subject to impact for the structural beam. The conclusions drawn from dead load status cannot be always applied to the circumstance directly when the structure is suffered to impact loads. The deformation models of structure beam caused from impact-load cannot be even explained by the analysis of dead load status. In this paper, by selecting the constitutive model—rigid plasticity, of cantilever beam with a main crack suffering to step load status, analyzes its deformation history. We can find that there is a quite different reactivity between defective beam and non-defective beam and the beam will have a counter movement when effected by strong impact load due to the existence of crack effect. In the end of the analysis, benchmark examples are provided respectively. This paper introduces the usual crack phenomena into impact dynamics, referring to previous research and obtains a primary research which is necessarily be verified by more experiments. However, the conclusion is drawn under the premises, such as the centralization of crack effect, and neglecting the subordinate effect.

The increasing competition on the international market requires intensified efforts of the machine tool manufacturers to further improve production accuracy and machining speed. Piezoelectric actuators can help to reach these goals by counteracting structural vibrations that impair the manufacturing process (e.g. chatter). By equipping production machines with piezo actuators, sensors, and a controller an adaptronical system is created. However, the application of these components requires high capital costs and engineering know-how. Likewise, it is difficult to predict the attainable manufacturing accuracies of adaptronically optimised machine tools. These facts impede the industrial use of this technical innovation. So far, a systematic and efficient integration of adaptronics into the design process of machine tools is missing. This paper deals with the development of a computational approach to the integration of adaptronical structures in machine tools. Hence, the machine tool manufacturer will be enabled to design an adap-tronical vibration damping system according to the process requirements of his customer.

In this paper, an adaptive finite element method is formulated based on the newly developed nearest-nodes finite element method (NN-FEM). In the adaptive NN-FEM, mesh modification is guided by the gradient of strain energy density, i.e., a larger gradient requires a denser mesh and vice versa. Mesh intensity is introduced to correlate gradient of strain energy density and mesh density. Relative error in the total potential energy is used to indicate when mesh modification should be stopped. Numerical examples are presented to demonstrate the performance of the proposed adaptive NN-FEM.

A new orthogonalization method is presented for the basic deformation modes. The inner products between basic deformation modes both including and excluding the element stiffness matrix are employed and the orthogonality within the orthogonal basic deformation modes is fully independent of the material properties so that they can serve as a uniformed tool to assess a given element. In the proposed approach, the arbitrary displacement field of deformation for different hybrid element can be easily decoupled into a linear combination of a series of basic modes. Thereafter their relating deformation energy, namely the element performance, can be directly studied. In the numerical examples the performances of several hybrid elements that are constructed by different assumed stress fields are provided using the proposed method. The results show that the method is very effective.

In order to meet the special demand of protection work, a new structure type of composite shell was put forward. The composite shell, which composed of spatial latticed shell structure and steel-concrete composite slab and the former is covered by the later, is a half-bred structure. With all merits of latticed shell and composite slab, the composite shell's structural performance is very excellent. To instruct structure design and test, the nonlinear property of new type of composite latticed shell, which based on spatial integral action is analyzed overall by FEM software ANSYS. The result of analyses shows that the new type of composite shell is a very excellent form of protection structure because of its prominent mechanical property.

Using finite strips of unit length and width, a rectangular membrane element with rotational degree of freedom is presented. This element can be used to solve planar stress/strain questions and combined with rectangular plate bending element to form plate-type shell element with six degrees of freedom at each node. With its linear interpolating function in the axial direction and cubic interpolating function in transverse direction, it can be coupled and superposed by beam element. Numeric analyses and comparison are carried out to verify the properties of this element, which show that this element has excellent precision and convergence.

Based on the postulate of the characteristics of fluid flow through joint networks of rock mass, the numerical simulation on coupled problem of seepage and stress in jointed rock tunnel was theoretically analyzed with the distinct element method. The theory of tunnel excavation and coupling effects between lining structure and groundwater seepage were studied. The numerical results show that the maximum stress of the wall rock increases but the maximum displacement decreases after the liner is applied. When considering the effects of seepage, the maximum stress and displacement of the tunnel wall rock have increased in varying degrees, the axial force and shear force of the liner decrease slightly, and the bending moment is large. The effects on the bending moment of the liner from the deformation are greater than that from the shear force in this condition.

This study proposes a simple but effective finite element method to simulate complex 3D crack propagation in quasi-brittle materials such as concrete. Cohesive interface elements, characterized by softening traction-separation constitutive laws, are embedded into initial meshes to model potential cracks. The method is implemented in connection with Abaqus. Various concrete structures under static and dynamic loadings were modeled with excellent results compared with experiments.

In this paper, a simple yet practical and direct method is presented for the determination of critical bending moments of bridge decks subject to traffic loads by taking the advantages of the concept of influence surfaces and the versatility of commercial FE software. The influence surfaces are obtained by putting unit loads across the region concerned and the corresponding computed results are exported to a spreadsheet. A least square fit to the classical thin-plate solution, based on the computed results can be easily obtained. Based on such a least-square solution, the locations and the corresponding critical moments for different types of designed loads can be calculated exactly by using a simple and readily available optimization tools in Excel. Comparing with conventional approaches in determining critical moments, the method is simple yet versatile and reliable, and it does not require any complicated mathematics or special software for practicing engineers to implement. Such an approach would lead to a more reasonable estimation of stresses in bridge decks or other plate-type structures which are subject to various moving loads with different arrangements.

This study develops a numerical method to simulate complex 2D crack propagation in quasi-brittle materials considering random heterogeneous fracture properties. Cohesive interface elements with softening traction-separation laws are inserted into the initial mesh to model potential cracks. The softening laws are modelled by spatially-varying Weibull random fields. Extensive Monte Carlo simulations of a concrete specimen under uni-axial tension were carried out. It was found that increasing the variance of the tensile strength random fields with increased heterogeneity led to reduction in the mean peak load and increase in the standard deviation. The developed method provides a simple but effective tool for assessment of structural reliability.

The behavior of short-term axially preloaded concrete columns with FRP confinement under axial loading is simulated by using finite element software ABAQUS, and the computing results are compared with the test ones. The comparisons show that proper analysis model can accurately simulate the axial compressive property of FRP-confined concrete columns. Then a parameter analysis is carried out to investigate the impact of longitudinal reinforcement ratio, volumetric lateral reinforcement ratio, concrete strength and restrain stiffness of FRP on the bearing capacity of columns and the load-strain curve under different preload stress levels. The results have indicated that, the confinement effect decreases as the preloading stress level increases. Under low preloading stress level, the reduction of load bearing capacity is less than 5 percent, and the deformation capacity can be greatly improved by enhancing the restrain stiffness of FRP. Under high preloading stress level, the reduction of load bearing capacity does not have the trend to decrease as the increasing of restrain stiffness of FRP.

The nonlinear response of the joints between concrete-filled steel tubular column and steel beams-covered concrete under low-cyclic reversed loading are simulated by using software ANSYS. Using a separated model, element concrete solid65 is used to model concrete material, element shell181 is used to model steel tubular, H-shaped steel beam and stiffened steel ring plate, element link8 is used to model steel bars. The numerical analysis results are compared with the data of the experimental research. The advantages and shortcoming of the finite element model are given. A better numerical simulation method and a use for reference to the similar case are expected to be afforded.

Firstly, analyzing the characteristic and shortage of the traditional evaluation methods such as fuzzy integrated evaluation, fuzzy inference and fuzzy inference network, combining the fuzzy integrated evaluation and fuzzy inference network, we have set up two improved weighted inference networks and shown the topological structures and algorithms. Secondly, applied the improved methods in high-rise building structural integrated performance evaluation, we presented the membership functions of the evaluation process, performance index system, weight and evaluation grade and structural anti-disaster performance, gave the engineering example. It is shown that: The methods provide a more intelligent and efficient methods for intuitive express and utilize the experts' evaluation knowledge and strategy.

The experimental program reported in this paper tested three inverted-tee girders with circular web openings strengthened with GFRP to failure to evaluate the openings' effect on girder behavior. Parametric study using response surface methodology through finite element analysis may form efficient approximation to deflection.

The 2-D model of plate with inner crack is simulated by ABAQUS finite element software. Three kinds of crack growth criterions (critical stress, crack opening displacement and crack propagation as a function of time) are applied to simulate crack growth process in this paper. The results indicate that the critical stress criterion, which is based on stress value near the crack tip, is applicable to brittle material crack growth. Crack opening displacement criterion, which is based on node displacement value near crack tip, is applicable to ductile material fracture. Crack length versus time criterion can be applied when the crack growth process is known in advance. As crack growth problem is with stress and strain singularities, the mechanical parameters near crack tip can be taken as crack growth criterion to simulate crack growth in finite element analysis.

The numerical analysis by using software ANSYS for shearing performance of rectangular reinforced concrete beams strengthened with steel wire mesh-polymer mortar formed U-shaped are studied. The numerical results are compared with experimental results. Two models, named separated model and composite model respectively in software ANSYS, are used to analyze the beams. In separated model, strains of longitudinal steel bars and stirrups are in good agreement with the test results. In composite model, strains of longitudinal steel bars are also in good agreement with the test results, while strains of stirrups are not. But both of steel wire deformations obtained by two models of software ANSYS are slightly different with the tests results. Cracks distribution in beams obtained by software ANSYS, comparing with test results, are not very obvious.

The present investigation focuses on the flexural behavior of HS steel-concrete composite beams using the commercial finite element (FE) software LS-DYNA. Herein, HS steel-concrete composite beams were constructed with a welded high strength steel I section beam and high strength concrete slab. The proposed three-dimensional FE model is able to simulate the overall flexural behavior, including load deflection behavior and failure modes, of simply supported composite beams subjected to two-point concentrated loads. The reliability of the model is demonstrated by comparisons with experiments results. The load-slip effects on the accuracy of the FE model analysis is also discussed in detail. The accuracy and simplicity of the proposed model make it suitable to predict and/or complement experimental investigations.

The bucket foundation offshore platform with two pillars is introduced in this paper. The structural outline, main dimensions and construction technology of the platform are discussed. The platform has many advantages, such as not needing piles, easy to be constructed, low cost and can be moved and used again. Static and dynamic analyses are carried out by means of space finite element model. The shell elements are used to establish the steel offshore platform and the spring element are used to imitate the interaction between the bucket and the soft soil in the model. Multiple disadvantageous loading conditions of wave and ice are considered in the static structural analysis, and dynamic modes and seismic responses of the platform are also researched in this paper. The results of the analysis show that this kind of platform has enough strength and stability when subjected to the loads of wave, ice and seismic. On the basis of the numerical results, some useful advices are presented to optimize the design of the platform.

In order to study hysteretic behavior of double angle framing connections, based on considering material, geometric and contact state nonlinearity, finite element analysis for steel double web angles framing connections under cyclic load is carried out. Three dimensional solid element is adopted in the connection models. Hysteretic behavior and failure mechanism of this type of connection are analyzed. Experiment study is conducted in order to investigate the seismic behavior of connection further and verify the reliability of the finite element model. The test consisted of subjecting four connection assemblages to increasing level of large cyclic displacements until failure occurred. The results of finite element and experiment indicate that specimens exhibit good ductile behavior; connection rotation exceeded 0.04 radians; the length of angles and the diameter and gage of bolts significantly affect the strength and ductility of connections. As the results of this investigation indicate, considerable moments can be developed in these connections. Therefore, to ensure safety and a realistic dynamic response analysis of steel frames with double angle connections, inclusion of realistic hysteretic characteristics of connection similar to those provided in this paper is essential.

Self-anchored suspension bridges are increasingly appreciated by engineers for their aesthetic look, low cost and more adaptive for geological environment than earth-anchored suspension bridges. Many self-anchored suspension bridges have been completed or are in construction in the world. For huge horizontal component of main cable in the stiffening girder and the different construction method, self-anchored suspension bridge has much less limit span than earth-anchored suspension bridges. In this paper, the limit span of three-span self-anchored suspension bridge with two towers is deduced. Some factors, such as ratio of rise to span of main cable, ratio of side-span to mid-span, second dead load and live load, are analyzed in this paper. Based on the common used material and considering the main factors, the limit spans of self-anchored suspension bridges with concrete stiffening girder and with steel stiffening girder, are discussed in detail, and the corresponding limit spans are given.

The large span underground water seal oil cavern not only need to rely on the natural conditions of the buried groundwater, but must also rely on the water curtain hole installed around the cavern in a certain pressure to provide a stable water injection pressure to prevent oil leakage. Taking a large domestic underground oil cavern as an example, seepage of fractured rock is analyzed under the three-dimensional stress field. Combining the relationship between the effective stress of infiltration formation and water pressure around the caverns, the analysis of different water curtain systems is done to get the proper ways to solve the seepage problems. The theory of flow closed loop is proposed and critical storage pressure according to the theory is given. Some suggestions are raised according to specific issues to meet the water closure effect and prevent oil leakage while reducing cavern inflow.

Drilling rig derrick is one of the most important equipment in hoist system of oilfield, which can be used to install crown block and hang tackle, hoisting hook and special tools, and also complete manipulations such as making a trip, casing running and so on. The static intensity and dynamic properties of derricks are the main parameters determining the safety of drilling rig derricks. A finite element model based on the non-linear beam element was built in this paper. The static stress and dynamic characteristics of the derricks was calculating by using FEM software ANSYS. Furthermore, optimization method and stability calculating method are using to improve the structural load-carrying capability of derricks. Results indicated that the load-carrying capability and stability of optimal structures have been improved greatly. It can give constructive guidance to structure design of derrick and safety production in oilfield.

The application of Fiber Reinforced Polymer (FRP) in civil engineering is a growing field worldwide. Many countries have different ideas and opinions on the applications of FRP. It includes general researches, standards design and specifications. Based on these key parameters, an exhaustive comparison between design standards of FRP-Strengthened reinforced concrete in the Chinese code and that of American Concrete Institute (ACI) is carried out in this paper. From a general viewpoint, the strategies of both codes for strengthening reinforced concrete structures are uniform. Nevertheless, the calculation methods of the bonded length, flexural capacity, and shear capacity are different from one another. The differences and sameness would deepen designers' understanding of FRP and illuminate them to pay more attention on these issues during calculation. This will contribute in making FRP an important material that could be effectively used and widely applied in the civil structures throughout the world.

The geometric reliability is usually applied in the structural analysis of the large projects. The structure-function is usually discrete or implicit. It is necessary to use penalty function to convert the constrained optimization problem into non-constrained optimization problem. We also analyze possible cheats of penalty in un-ultimate state (mostly happen in penalty safe sate). So it is proposed that only use structural fail regional variables by random sampling to solve the geometric reliability, obtain an non-constrained optimization problem and un-introduction penalty function. It proposed use discrete optimization (such as the GA, ACO, PSO and so on) to solve geometric reliability, the penalty is carried out on the variables in the safe state not in the structural fail and ultimate state. Through comparison of benchmarks from Monte-Carlo method, random sampling and GA in SFSCGR (Structural Fail State Calculation Geometric Reliability) and PSUUSCGR (Penalty Structural Un-Ultimate State Calculation Geometric Reliability), it is illustrated that SFSCGR is feasible, and it is very stable and accurate in geometric reliability solving.

Using lateral deflection calculation formula for frame-core structure with top horizontal outriggers, analysis of the optimum stiffness of outriggers in frame-core structure with strengthened story is carried out. The method that confirms the optimum stiffness of horizontal outriggers which base on reduced structure lateral deflection magnitude and precise parameters are presented. The result of case study shows that this method is creditable. The conclusion can be referenced for designing and especially for confirming structure scheme.

The PEM (Proton Exchange Membrane) fuel cell is a multi-layers structure which is constructed by different components in contact. In this work, we propose a 3D parametric numerical modeling which permits to investigate the mechanical effect of contact behavior concerned with the performance of a PEM fuel cell. Numerical results can help to increase the knowledge of fuel cell's performance and to determine the parameters for the structural design of a PEM fuel cell.

This paper discussed analytic models of frame-slit-wall system suggested by JGJ99-98 and pointed out the necessity of considering shear deformation of web of steel beams when determining the section of equivalent cross bracing or shear plate. The models suggested by JGJ99-98 cannot predict the actual shear forces in steel girders, its bending deformation have not be included either. This paper suggested a wall-column model, the rigidities of various parts in this model are proposed. A very low axial rigidity is assigned to the wall-columns modeling the slit-walls to implement the design philosophy of carrying no vertical loads by slit-wall. Comparison between three models is carried out and it is found that three models predict nearly the same lateral stiffness. But the wall-column model can correctly predict the internal forces and deformations of each member in the model, thus implies an improvement over the cross bracing or shear plate models.

In recent years, researchers identify the complete softening curve of concrete materials by employing inverse analysis method. The inverse analysis method based on fracture experiments of concrete is numerical simulations by using discrete approach of non-linear fracture mechanics. First, a softening curve is assumed and the load-displacement curve obtained by the numerical simulation is compared to the one determined experimentally by fracture experiment of concrete. By updating the assumed softening curve, the numerical results optimally fit the measured ones. When the best fit of the numerical and the experimental results is obtained, the assumed softening curve is viewed as the one for characterization of the material behavior. Load-crack mouth opening displacement curve (P-CMOD curve) is an important measured curve which characterizes fracture property of concrete in fracture experiment. For each group of fracture experiment specimens, there are three companion specimens tested in the group. The emphasis of this paper is as follows: Developed a processing program for the original test data which length is up to 30000~300000 lines for each specimen. The program can filter test data scattered far from the P-CMOD curve and remove the effect of fluctuation in the measurement of fracture experiment. A new test data processing method for fracture experiment of concrete was proposed based on crack propagation process of concrete materials. Thus a representative P-CMOD curve which characterizes the fracture property of the companion specimens for each concrete specimen group is achieved by averaging the above-mentioned test results of three companion specimens. Since the number of data points used in optimal fitting of inverse analysis have an effect on the computer running time observably, the minimum number of data points adequately representing P-CMOD curve is desirable. The minimum of data points were extracted from the averaged data for the companion specimens by an optimization procedure. This paper employed the proposed method to analyze the original test data of different sizes of wedge-splitting specimens made of dam concrete. The representative P-CMOD curves were obtained for companion specimens of different fracture specimen groups. The obtained representative P-CMOD curves were prepared for an inverse analysis to find the softening curves of dam concrete and were employed to investigate the fracture property of dam concrete.

In sheet forming process the springback after the tool withdraw often causes a deformed geometry. In order to obtain the desired geometry, the spring-back effect should be compensated by the modified tools, called “false” tools in this study. In the numerical simulation, the forming process simulation gives a FE part mesh which fits well the tools and then the springback simulation gives a “deformed mesh” which has the same nodes and element connectivity as the part mesh. A displacement adjustment of the nodes on the part mesh in the opposite direction of the springback deformation leads to a “false mesh”. This mesh defines the geometry of the “false” tools which will be used in the next forming and springback simulations until a part with desired dimensions is obtained. In this paper, we propose a technique of surface reconstruction in order to facilitate the parametric shape optimization and tool manufacturing. In our technique of surface reconstruction, we discritize the tools' surfaces one by one by a triangle mesh and move these nodes (sample points) onto the “false mesh” in keeping their local surface coordinates, then we project them on to a local quadratic surface, finally we reconstruct Nurbs surfaces using the moved nodes on the “false mesh”. The main idea is to take a surface of the initial design tools or a newly created Nurbs as the reference surface and move its control points in order to obtain a new surface (surface of “false” tool) that is very close to the “false mesh”. The surfaces of the “false” tools are created one by one by minimizing the gaps between the new surfaces and the moved sample points on the “false“ mesh in keeping the sample points' normal on the border of two surfaces. The Nurbs surface creation is fulfilled on the “Open CASCADE” platform and the numerical simulations are carried out in ABAQUS.

Xiamen Xiang'an Subsea Tunnel is the first subsea tunnel in Chinese mainland which is independently designed by the domestic experts. The design service life is 100 years. Drilling and blasting method is employed for excavation. One of the most difficulties during the process of construction is how to cross the deep weathering slots successfully and safely. In this paper BEM software BMP 2000 was used to simulate the surrounding rock displacement of F1 deep weathering slot, and uniform design and grey-correlation analysis method was applied to analyze the correlation between surrounding rock displacement and the influencing factors. The results show that lateral pressure coefficient is the most sensitive factor to horizontal convergence of surrounding rock, followed by the tensile strength of surrounding rock; but to the vault crown settlement of surrounding rock, Poisson's ratio is the most sensitive factor, followed by the internal friction angle. The research achievement has been using in the design and construction of Xiang'an Subsea Tunnel, and good results have been achieved.

Because of the complexity and variety of geotechnical material, the constitutive models put forward by existing FLAC

3D

software can't satisfy all the requirements of actual numerical analysis. In accordance with fundamental code-run-principle of FLAC

3D

software, the basic principle of the secondary development program is made, the modified Naylor constitutive model is developed in FLAC

3D

with VC++(7.0) environment. A series of simulations of triaxial tests are performed to verify the correctness of the compiled model. The Secondary development environment is more friendly and effective in support of object-oriented approach. Therefore, the design mode proposed in this paper can be served as references for secondary development of other constitutive models.

In this paper we handled the problems with several coexistent frictional contacts by finite element method, and checked the results of the numerical simulation by laboratory test. We simulated a spliced friction component and a steel frame joint with high strength bolts splicing, in which a number of frictional contacts such as the flange splicing to the beam flange; the web splicing to the beam web; the bolt head to the splicing and the bolt shank to the bolt hole were considered. By comparing and analyzing, we find that the predictions from the finite element simulation are proved to be in good agreement with experimental results. The applicability of finite element method on the solution of complex coexistent contact is affirmed.

As the stiffness of a circular hollow section tube in radius direction is generally much smaller than its stiffness in axial direction, failure occurs easily at the position close to the weld toe on the chord surface of a tubular joint. To improve the bearing capacity of a tubular joint, collar plate can be used. Using finite element (FE) modelling, the static strength of collar plate strengthened tubular joints is analyzed and the accuracy of the numerical results are evaluated. Furthermore, the influence of the joint & the collar geometries and the material property on the static strength of the tubular joints is investigated. And finally, some advice is proposed for design purposes.

With rigorous working condition, the seaport wharf is dilapidated more quickly than other structures, which havoc its security and applicability. For the lower durability, the health monitoring for the seaport wharf is necessary and urgent. In this paper, base on detection data and considering the different working ways of seaport wharfs, the effect factors for the security and durability of wharfs are researched. And indicators of the structural health monitoring for wharfs are proposed. Sensors, such as fiber optic sensors, which suit the health monitoring of seaport wharf, are introduced. Damage identification methods for gravity quay, quay wall of sheet pile and open wharf on piles are discussed. Finally, the current status of application of structural health monitoring for seaport wharf is presented and some suggestions are proposed.

In this research a computer program based on finite element method is used as a tool to study the effect of anisotropic permeability on the flow of water through an earth dam. The program has been checked with the typical solution of constant permeability of Dupuit solution, which is giving a good agreement with it. The program is used to compute the quantity of flow through a soil with an-isotropic permeability for different cases of upstream and downstream and length of flow. Relationships between normalized quantity of seepage through dam and downstream-upstream head ratio are presented for an-isotropic ratio K

x

/K

y

(20,10,5, 4,2,10,5,0.1,0.05). According to the obtained results, anisotropic permeability plays an important role in calculating an accurate value of the quantity of seepage, and should be considered in design.