Proceedings of the Indian Structural Steel Conference 2020 (Vol. 1)

Exploration and production in deepwaters are dominated by compliant offshore structural systems due to the advantages that arise from their geometry and construction practices. Semi-submersibles are a class of floating offshore structures, which are widely preferred for deep and ultra-deepwater applications due to their better stability characteristics and lesser sensitivity to the harsh ocean environment. A semi-submersible is positioned-restrained using the spread mooring system with either a steel catenary geometry or taut-mooring. The present study highlights dynamic response analysis of a semi-submersible with the spread mooring system, and its fatigue life under cyclic environmental loads is estimated. Lateral loads that arise from waves, wind, and current cause dynamic tension variations in the moorings, influencing their fatigue life significantly, and it is observed that fatigue life of catenary mooring lines is higher than that of taut mooring lines. Lateral loads under different directions are considered to exhibit the influence of wave directionality on the semi-submersible response. The nonlinear coupled dynamic analysis between the semi-submersible and spread mooring system is carried out using commercially available tool ANSYS AQWA, and fatigue life of the mooring system is evaluated based on the S–N curve approach.

For Modularization projects in Oil and Gas industry, Transportation of Structures (i.e. Modules or Pipe Racks) through modular trailers is usually considered as an important activity. Two types of modular trailers, Self-Propelled Modular Trailer (SPMT) and Propelled Modular Trailers (PMT) are used for this purpose. As a part of structural analysis, Trailer deflections and stability are also checked. Excessive deflection of trailer can have adverse impact on transportation operation including effect on structural integrity and/or trailer stability. Power Pack Units (PPU) are considered as essential component of the trailers which provide motion and suspension power to SPMT and PMT. Typically those units are cantilevered from one end or both ends of trailer. Generally consideration of power pack weight in analysis results in lesser deflection of trailer, as effect of those load counteracts to the sagging deflection profile of the trailer. So in general, it is considered that exclusion of the power pack loads will yield conservative result. This chapter discusses how the weight of PPU can generate high trailer deflection and describes viable solution for reduction of such deflection and thus obtaining a favorable trailer profile necessary for safe modular transportation per given project parameters.

Guyed masts have unique structural behaviour among other civil engineering structures due to their height, slenderness, light weight and overall flexibility of mast. Wind is predominant on these structures, are very sensitive to dynamic excitation from gusty wind due to flexibility associated with both mast-slender and guy cables. As per IS 875 (Part 3)-2015, dynamic wind loading shall be considered for such flexible structure using gust factor (G) method which is based on spectral characteristics of wind velocities, first natural frequency and damping ratio of structure, assuming that dynamic response at every point is a simple multiple of its static response of steady winds. Gust factor method is valid for structures with one or two dominant vibration modes, and it is not appropriate for guyed mast where 15–20 vibration modes contribute significantly to the response of structure to turbulent wind. In lieu of dynamic analysis Sparling et al. (J Int Assoc Shell Spatial Struct 37(2):89–106, 1996, [6]) proposed patch load method of analysis that utilizes a series of static load pattern to replicate effects of wind gusts and systematically accounts for the characteristics of mast and wind using empirical scaling factors. In this paper, study of gust factor method and patch load method for 100 m high guyed mast is undertaken through load calculation using gust factor and patch load method with geometrically non-linear analysis using STAAD Pro Advanced Analysis software along with comparison statement presented. From the analysis, gust factor method heavily underestimate leg forces in upper spans and bracing forces in middle of each spans and concluded that patch load method gives better approximation compared to gust factor method for analysis of guyed mast.

The pressure hull is one of the main structures of underwater vehicle, mainly designed to withstand the compressive forces associated with hydrostatic pressure. The ring-stiffened cylindrical hulls have better structural performances and are widely used in underwater vehicles and submarines. Functionally Graded Material (FGM) may be characterized by the variation in structure and composition gradually over volume, resulting in corresponding changes in the material properties. FGM found its applications in marine, submarine industry and defence especially for pressure hull and bullet proof underwater vehicle. In this study, non-linear static and dynamic analysis on cylindrical pressure hull with FGM has been done using ANSYS Mechanical APDL. The study included modelling and analysis of cylindrical pressure hull with different materials such as Steel, Titanium, Steel-Aluminium FGM and Titanium-Aluminium FGM with fixed and pinned boundary conditions. Deflection, von-Mises stress and von-Mises strain of different models were compared.

In any power plant, Turbo Generator is the most dynamic as well as the most expensive equipment and placed inside the Turbo Generator building. TG substructure being a dynamic structure conventionally, the foundation system of Turbo Generator and TG building is kept separately. This leads to not only tedious design calculation of TG deck supporting structure and TG building supporting structure but also the extensive requirement of time for carrying out the construction work. Also, the supporting structure for the TG deck is generally made up of concrete columns, which adds more to the construction time. In one of the power plant projects having capacity 600 MW, the analysis and design of the TG substructure were carried out using a structural steel column framework for supporting the TG deck slab of Turbo Generator. The springs which act as a dampener were placed in between the TG deck slab and the steel columns. For the analysis and design, the TG substructure is integrated with TG building. Due to this the structural analysis and design become simple, more space is available compared to the concrete structure, construction time is less compared to the concrete structure and also sustainable when compared to the concrete structure. In this paper, a complete detail design approach has been presented. The 3-D model and analysis were done using STAAD software. The comparison between the supporting system of Turbo Generator with steel column and concrete column has also been presented to find the most desirable system.

Nonlinear time-history analysis is used to assess a structure’s ability to resist future earthquakes. The nonlinear behavior of the buildings is greatly affected by material nonlinearity considered during the analysis. This paper examines the nonlinear time-history analysis of steel frame by taking four different nonlinear steel material models into account, namely steel with elastic-perfectly plastic behavior which fails at yield strength, Menegotto and Pinto model with isotropic hardening, Menegotto and Pinto model with kinematic hardening and Ibarra–Medina–Krawinkler (IMK) model. Menegotto and Pinto’s model is used to simulate cyclic response. This is uniaxial material model and is used to describe the steel response in fiber-discrete cross-sections and under normal stress. IMK model is a deterioration model which takes degradation of material properties like strength and stiffness into account. In order to study the effect of material nonlinearity on the behavior of six-story building frame during an earthquake, the fragility analysis on these models is conducted by multiple stripe analysis.

The liquid storage tanks (LSTs) are the paramount structures in oil, nuclear and various chemical industries. The structural properties and sloshing of stored fluid can significantly alter the nature of the seismic response. Several failure incidences of LSTs are available in history because of earthquakes. Despite exhaustive research on this topic, the behavior of the rectangular steel LSTs under the near-field earthquake and long period far-field earthquakes demands more attention for a more stable design. The finite element (FE) analysis of LST is done on the ABAQUS platform. The behavior of the LSTs is studied by varying the angle of incidence of the earthquakes and the ratio between the different components of the earthquake. The resultant response due to bidirectional interaction and angle of incidence shows an increase in sloshing height; von Mises stress and top board displacement.

This paper deals with the study of the stress characteristics of isotropic and orthotropic plates under a uniform and non-uniform uniaxial tensile load. Numerical analysis of stress characteristics of both the plates has been performed, and a comparative study has been made. The obtained results are compared with the available results for validation. The stress results for two types of boundary conditions are presented for both the plates. The effect of the uniform and parabolic in-plane tensile pressure on the stress distribution has been studied. It is observed that the loading profile has significant effect of stress distribution of the plates. The effect of the orientation of the fibers has also been studied.

Braces in concentrically braced frame system dissipate majority of the seismic energy imparted to the structure through inelastic cyclic axial deformations. During the inelastic cyclic deformations, the braces might initiate fracture prematurely if the selection of the brace geometry is not decided properly. Hence, the main objective of the study is to couple the continuum-level study with micro-mechanical fracture model to decipher the localized mechanism behind the origin of brace fracture initiation phenomenon. Monotonic and cyclic notched bar test results available in the literature have been used to calibrate the numerical model for capturing the inelastic cyclic material response. The calibrated numerical model has then been used to model the braces across a wide range of brace geometries, using which the stress and strain histories for cyclic loading have been evaluated. The evaluated stress and strain histories with the help of micro-mechanical fracture model have been used to capture the ductile fracture initiation of braces. From the obtained results, it has been observed that the slenderness ratio and width to thickness ratio have a strong influence over the initiation of ductile fracture in braces.

Monitoring large structural systems for assessing the potential degradation of structural properties by identifying the dynamic characteristics is needed for assuring safety of the system. Measurements made at a single point in the structure can be used to detect, locate and quantify damage. In this work, a method for determining the damping characteristics of a structure from the measured modal characteristics is presented. This method uses the dynamic properties obtained from the vibration response of the structure. A three-storied aluminium base frame and 8 damage-induced frames were experimentally studied by horizontal shake table. Damage was induced on the base frame by reducing the cross section of the column. The experimental observations on frequency, displacement and acceleration were used to obtain the dynamic characteristics of the structure. By comparing both theoretical and experimental results of the storey-level deflection, damping ratio of the structure is identified.

The Plasco tower, built in 1962, was the tallest building with 17 storeys in Iran at the time of its construction and was considered as an iconic high-rise dominating the Tehran skyline. In January 2017, a fire started on the 10th floor which eventually led to its collapse and caused many deaths and injuries. The building was used as a residential and commercial building, with a major shopping centre on its ground floor, a restaurant on its upper floor, and several clothing workshops. It was a steel structure with built-up sections fabricated using standard European channels and angles without any fire protection. The tower had four strong core columns to transfer the load from primary beams to the foundation and relatively closely spaced interconnected columns along the periphery. This exterior framing is designed to be sufficiently strong to resist all lateral loads on the tower, thereby allowing the interior of the tower to be simply framed for gravity loads. For modelling, OpenSEES fibre-based sections and displacement-based beam-column elements are used. The thermal properties and elevated temperature mechanical properties are as recommended in the Eurocodes. As documented, the fire started at the 10th floor and then involved stories 11–14 as a result of a horizontally and vertically spreading fire. The thermo-mechanical analyses are performed assuming no variation of temperature across the thin sections. Based on the best available information, the floor in plan is believed to be structurally divided into nine individual blocks by two centrally running primary truss beams in both directions. This leads to an understanding that each block is structurally isolated except at the peripheral beams and central core columns, however, if the reinforced concrete floor slab is composite with steel beams of the floor system, this will not be the case. This paper presents the structural response of the tower over a single floor as a preliminary analysis.

This paper lays out a procedure to quantify the buckling loads of Greenhill shafts using variational iteration method. Lack of approximate methods for Greenhill shafts is attributed to the non-self-adjointness property of its governing differential equation. For a Greenhill shaft, a series solution is assumed for the displacement in terms of polynomials, and a correction functional is applied, which requires a Lagrange multiplier function. An exact general Lagrange multiplier is difficult to identify for a fourth-order differential equation as it requires solution procedures for quartic polynomials. Hence, simplified approximate formulae for Lagrange multiplier are chosen from the literature, and the effectiveness is demonstrated for a pinned–pinned shaft, subjected to a conservative axial load, and a non-conservative axial torque.

The destruction as loss of life and prosperity occurs due to several types of blast explosives. Explosive upon explosion produces a huge amount of pressure and gases, which moves in all directions from the source point, cause damage to structures and the structure may collapse. Models of a few structures have been designed and analyzed to resist the physical and chemical explosives. The effect of the blast on structures also depends on the ductility ratio of structures. Study contains three types of structures, viz. reinforced—concrete frame structure, masonry structure, and reinforced—concrete frame structure with masonry infill, respectively. The structural properties of models are such as the height, width, size of the column, size of the beam of structural models are 3.2 m, 4.5 m, 500 mm × 500 mm, and 400 mm × 400 mm respectively. The thickness of masonry wall, grade of concrete, and grade of steel of structural models are 250 mm, M30, and Fe-415 HYSD steel, respectively. Analysis of the response spectrum has been done for structural models. The force–time—history is considered as a linear—equivalent triangle and a dynamic analysis has been performed. Calculation of blast load parameters has been done using IS: 4991-1968. The response spectrum of structures has been found from analysis with respect to the variation of structural stiffness for blast load of 20 kg explosive placed at a distance of 5 and 25 m. The study of response spectrum characteristics for models subjected to blast loads have been made with the variation of damping 0 and 5%.

Industrial pallet racking system was the commonly used structure for storing palletized goods. They were built up from thin-walled cold-formed steel profiles. The upright (column of the rack) has perforations which ensure the typical functionality, adaptability and flexibility needed for accommodating the variability of dimensions of the stored goods. Connections were custom made, where in the beams were generally hooked on to the upright. These connections were significantly semi-rigid in behaviour. The complexity associated with the nonlinear moment-rotation behaviour of the joints in the design of cold-formed steel structure was to be accounted for a realistic capacity estimation. These racks when installed in seismic prone zones must be qualified for different levels of safety such as collapse prevention and immediate occupancy. To assess these performance levels, static and shake table tests were performed on full-scale racking system simulating earthquake conditions. An attempt has been made to quantify the dynamic behaviour of the structure based on the experimental results of both static and dynamic shake table tests. Based on the test results, it was seen that the requirements with respect to performance levels specified by FEMA 460 were met by the structures. With respect to the behaviour of the pallet under severe dynamic excitation, it was observed that the wooden pallets did not have relative body motion and were vibrating integrally with the structure. Therefore, in a full-scale test, the relative performance of pallet/rack system could be quantified for the first time.

Offshore structures are exposed to wide range of cyclic loadings which causes fatigue damage and hence it is an important design consideration which determines the durability of the structure. Due to the complexity of the random loading conditions, determination of fatigue life is a tedious task. Therefore, it is important to develop a reasonable loading spectrum for fatigue assessment using cumulative fatigue damage (CFD) theory. There are few methods by which we can predict fatigue life of a structure which include fatigue crack propagation (FCP) model, by using conventional empirical relations and by developing fatigue stress response spectrum. In this paper, fatigue life of a semi-submersible platform is determined by analyzing critical joints which are exposed to cyclic loading and also by considering random numbers of short-term wave conditions which follow Rayleigh distribution. Structure considered for the study is a sixth-generation semi-submersible platform known as COSL Prospector made in CIMC Yantai Raffles shipyard in China designed for North Sea. Firstly, a hydrodynamic diffraction analysis is carried out in order to understand the response of the structure under various wave directions and frequencies. Wave-induced pressure on the column-bracing connections are determined and these joints are considered as critical locations for fatigue analysis. Suitable wave spectrum is then developed for each sea state conditions. In order to determine the stress concentration factor of the column-bracing joint, a local geometrical model of the connection is created followed by generating a fatigue stress energy spectrum and complex fatigue stress transfer function which is later described to the model. The minimum fatigue life of the local model is determined, and the results are compared with the specification required.

Pre-engineered building is a new form of construction practice that is slowly emerging in Indian construction industry, which has large potential to replace conventional steel structure. The objective of this research paper is analogous examination of analysis and design of PEB structure with EOT crane, according to Indian Standards (Chia-Ming and Jong-Kook in J Constr Steel Res 70:248–255, 2011; Bureau of Indian Standards in Indian Standard General Construction in Steel Code of Practice (IS 800:2007), pp 1–143, 2007; Bureau of Indian Standards in Indian Standard Code of Practice for Design loads (other than earthquake) for Buildings and Structures Part-1 Dead Loads (IS 875 Part-1), pp 1–37, 1989; Bureau of Indian Standards in Indian Standard Code of Practice for Design loads (other than earthquake) for Buildings and Structures Part-2 Imposed Loads (IS 875 Part-2), pp 4–18, 1989; Bureau of Indian Standards in Indian Standard Code of Practice for Design loads (other than earthquake) for Buildings and Structures Part-3 Wind Loads (IS 875 Part-3), pp 1–56, 2015) and American Standards (Metal Building Manufacturers Association in Metal Building Systems Manual, pp 1–335, 2012; ANSI/AISC 360-10 Specification for Structural Steel Buildings. Chicago, IL: American Institute of Steel Construction, 2010; ASCE/SEI 7-10 in Minimum Design Loads for Buildings and Other Structures. Reston, VA: American Society of Civil Engineers, 2010). This paper presents comparative results of different clauses in each of the above-mentioned codes and its results in terms of economical aspect, percentage difference of member capacities and deflection criteria under same primary loading conditions and distinct impact factor considered for frames and Crane Gantry Beam design. This analytical study would further help for in-depth understanding of design philosophy used by Indian Standards and American Standards used for designing. The scope of our study is only with regards to gravity loading, crane loading, prevailing wind loading conditions and their combinations as per IS: 800-2007 and ASCE-7-10.

A 2MWe solar plant is proposed to be set-up. A 40.8 m diameter hyperboloid supported on three towers (60 m height), 118 heliostats of dimension 10 m × 10 m, 228 heliostats of dimension 5 m × 5 m and an 8 m diameter receiver are the major components of the proposed plant. Hyperboloid with tower assembly is one of the key components of the concentrated solar power plants based on central receiver concept. Hyperboloid reflects the reflected rays from the field heliostats to the receiver mounted at the ground. It consists of hyperboloid frame on to which aluminium-based reflector is fixed. Hyperboloid frame is made of carbon steel and aluminium tubes. Aluminium reflector (mirror) is made of 0.8 mm aluminium sheet. Hyperboloid structure along with reflectors is supported by tower structures. Towers are made of carbon steel tubes. Hyperboloid is fixed with three towers by bolting arrangement. Hyperboloid with tower assembly is designed against wind load of 39 m/s basic wind speed. Finite element analyses have been performed to optimize the design and estimate the deflections and stresses due to dead weight, imposed loads, earthquake loads and wind loads. Stresses due to various loads and their combinations have been checked against the allowable stresses as per IS 800. Buckling checks have been performed as per IS 800.

A 2MWe solar plant is proposed to be set-up. A 40.8 m diameter hyperboloid supported on three towers (60 m height), 118 heliostats of dimension 10 m × 10 m, 228 heliostats of dimension 5 m × 5 m and an 8 m diameter receiver are the major components of the proposed plant. Heliostat is one of the key components of the concentrated solar power plants based on central receiver concept. Large number of reflector assemblies (heliostats) that are capable of tracking the movement of sun, are installed in the field and are manipulated by computer programme to constantly focus the reflected rays of sun on to a centrally fixed receiver. The objective of heliostat is to accurately focus the reflected rays on to a calibrated target point. The positioning accuracy of heliostat is achieved through servo control drive system using gear drives. A 10 m × 10 m heliostat, made of carbon steel box and circular sections, is designed against wind load of 39 m/s basic wind speed. Finite element analyses have been performed to optimize the design and estimate the deflections and stresses due to dead weight, imposed loads, seismic loads and wind loads. Stresses due to various loads and their combinations have been checked against the allowable stresses as per IS 800. Buckling checks have been performed as per IS 800.

In construction industry, the usage of structural steel in the building has increased and it can also be recycled in the future. The structural members in tall industrial steel buildings like column occupies more space due to larger section size which causes obstruction. In order to achieve economical section size for tall industrial steel building, spacing of columns is ideal, to be chosen with trial and error method for assessing the distance of center to center of column. The bracings system is provided in vertical plane, which will be tied to the major axis of column above certain height in nonusable space and also bracings system in horizontal plane, where both the planes act as a diaphragm. Due to connection in the major axis of column, section reduction will be possible by distribution of forces equally. The members used in bracing system will be of higher section due to distribution of more forces. For this the members of different shapes are used, to find the optimum section for the bracing members. This helps in optimizing the section size of the tall steel building.

In this paper, a reference-free spectral correlation-based approach for enhanced breathing crack diagnosis is proposed using the acceleration time history responses measured under bitone harmonic excitation. Even though spectral correlation can effectively remove the stationary noise components overlapped with the nonlinear intermodulation components in the response, it is difficult to isolate the intermodulation components alone at a selected cyclic frequency, and careful choice of appropriate cyclic frequency has to be made for accurate damage diagnosis. Therefore, linear response subtraction is first applied on the actual response to isolate the breathing crack induced nonlinear intermodulations, and then, spectral correlation computed from modified response is used for breathing crack diagnosis. The proposed linear response scheme helps in enhanced breathing crack diagnosis using spectral correlation estimated at any cyclic frequency. The proposed scheme is verified through both numerical and experimental examples.

This paper aims at proposing a steel jacketing retrofitting scheme for severely damaged reinforced concrete frame. An experimental study conducted under slow cyclic displacement-controlled loading on a full-scale model of reinforced concrete (RC) frame has been adopted for this purpose. The reinforcement detailing of the frame was given according to IS 456:2000, i.e., without any ductile detailing. The tested frame suffered severe damages due to the formation of shear cracks and plastic hinges at the beam-column joint and at the column ends, respectively. A steel jacketing retrofitting scheme has been recommended and studied here for retrofitting the damaged frame. The retrofitting scheme basically focuses on the improvement of lateral strength and lateral stiffness of the frame with varying thickness of the steel plates along with their location to be applied to the RC frame. The results obtained from the numerical study clearly show the contribution of steel jacketing in regaining and improving the lateral strength and lateral stiffness of the frame.

To ensure the structural safety, efficient performance, and minimums disturbance to business operations after an earthquake, proper seismic design of buildings is of ample importance. Often, post- tensioned (PT) shear wall having self-centering capacity is used as one of the effective ways of resisting large lateral shear force during earthquakes. However, to keep the structural form in serviceable condition, the maximum energy that can be dissipated through PT shear wall is limited to energy dissipation through the elastic behavior of PT tendons and pure rocking of the wall. Hence, in situations having a higher force and limited drift demand, PT shear walls with internal energy dissipating reinforcements (IEDR) are being used in practice. Analysis of such shear wall configurations though experiments is a tedious job and also not feasible for the economic point of view. Hence, there is a requirement of a computationally efficient numerical model that can replicate the actual behavior of post-tensioned (PT) shear wall with IEDR. The computational efficiency of the numerical model is also needed to be checked. This paper investigates the behavior of the numerical model of a PT shear wall with internal EDR subjected to lateral cyclic loading whose computational efficiency has also been examined and modifications are tried to be introduced.

The continuity in the lateral connectivity offered by laced built-up columns enables them to perform better, particularly when the axial demands are large and under lateral loading. The configuration of lacing adopted is one of the important parameters that affects the peak resistance of built-up columns. This paper reports a numerical parametric investigation conducted to study the lacing slenderness influence on the strength variation of short built-up cold-formed steel (CFS) columns. ABAQUS was used to develop the numerical model, where concentric axial loading was applied to the built-up columns constructed from four plain CFS angle sections, fastened by lacing bars configured in N-type latticed pattern, with pin-ended supports. The experimental results of laced CFS built-up columns conducted by the authors earlier and that of on battened CFS built-up column conducted by EI Aghoury et al. were adopted for calibrating the numerical model for performing the numerical parametric study. Lastly, the design axial strengths of the built-up columns were computed by adopting various current standards on steel structures, which were later compared with the numerical results.

The design equations for the ultimate global buckling strength of cold-formed steel (CFS) compression members in different design standards were originally developed for hot-rolled steel (HRS) members which normally do not undergo flexural torsional buckling (FTB). The presence of post-buckling strength for CFS compression members undergoing FTB was reported in the literature which is not accounted for in design equations. There were a few attempts to incorporate the post-FTB strength to the global buckling strength equations available in North American Standard (NAS). One of the recent proposals is to introduce a modification to global buckling strength equations by introducing an additional parameter, β which represents the relative principal second moment of areas (Ix/Iy) of the cross-section. This paper demonstrates the limitations of using parameter β for modifying the global buckling equations to account for post-buckling strength.

Cold-Formed Steel (CFS) built-up beams are used widely in the construction industry. In the current study, an experimental investigation of simply supported built-up beams with intermediate web stiffeners was carried out under both three-point and four-point bending. The built-up sections were assembled from press-braked sigma-shaped open sections connected back-to-back and front-to-front by spot welding at flanges to form I-sections and hollow tubular sections respectively. A total of 30 specimens comprising of both I and hollow sections for various beam lengths and intermediate connection spacing were tested. The observed failure modes and the obtained moment capacities from experiments are presented along with a comparison of moment capacities predicted using the North American Specification’s Direct Strength Method (DSM). The findings indicate that the AISI’s DSM method of moment calculations was found to be conservative for few specimens and unconservative for the majority of the test specimens.

In the load-bearing wall frame system, built-up sections are utilized over single section to enhance the performance of Cold-Formed Steel (CFS) structural systems. Built-up CFS sections can be formed in different shapes by the use of intermittently connected fasteners in the longitudinal direction. The spacings of these intermittent fasteners can alter the global buckling behavior of built-up CFS columns, and hence, they are investigated in the present study. The change of global buckling load from a single section CFS column to a built-up section CFS column is studied with different fastener spacing. In this chapter, a numerical methodology using a compound spline finite strip method is developed to compute the elastic critical buckling load of CFS built-up columns. The results of buckling analysis are compared with FE-based software ABAQUS and results are found to be in good agreement. Parametric studies on back-to-back connected I section with different web to flange ratios have been carried out, and it is found that global buckling behavior of open built-up sections will move toward fully composite section buckling behavior with the reduction in the fastener spacing.

This chapter deals with the ultimate strength and buckling behaviour of cold-formed steel Zee-shaped section under combined axial and bending actions. The numerical model was developed using finite element software ABAQUS. The specimen dimensions are chosen based on the elastic buckling curve from the CUFSM and GBTUL to study the cross-sectional and global buckling behaviour of Zee-shaped section. The numerical models are made using the S4R element, with simply supported end condition. The non-linear analysis including material, geometric non-linearity, and geometric imperfections, is conducted to predict the ultimate strength of the beam-column members. The numerical model was validated with the experimental results from the literature. Based on the validated model, the study is extended to develop axial—Moment (P-M1-M2) strength interaction surface for the selected member. The numerical study is conducted on the Zee-shaped member subjected to major, minor, and bi-axial moment. The effect of stress distribution due to combined load on the ultimate strength is examined, which forms the basis for the new design formulation for beam-column using direct strength method. The numerically generated strength surface was compared with beam-column prediction based on North American standard AISI S100-2016 specification.

Pallet racking system made of cold-formed steel members is commonly used for storing palletized goods. To make the structure flexible to accommodate varied sizes of pallets, beams are hooked on to upright columns. The connection between upright column and beam is semi-rigid, and hence, the behavior of the system is nonlinear. Since uprights are made of cold-formed perforated sections, they are most vulnerable to local and torsional buckling under gravity as well as lateral load. To verify how the system responds to lateral earthquake loads, it is important to conduct full-scale experimental studies under monotonic and cyclic lateral loading conditions, for getting realistic nonlinear behavior. An attempt has been made in this study to bring out the behavior of the structure through an analytical model using STAAD PRO. To validate the model, a comparison has been made with full-scale experimental results involving static (monotonic and cyclic) load displacement behavior. The results were used to fine tune the moment rotation characteristics of upright-beam as well as upright-baseplate joint. The results from the analysis are found to be in good agreement with the respective experimental results.

The aim of this chapter is to evaluate the moment capacities of the partially restrained cold-formed purlin subjected to uniformly distributed transverse uplift loading. A linear and non-linear finite element model is used to investigate the buckling behavior of purlins in the purlin sheeting system. The effect of translational and rotational restraint provided by sheeting to the purlin is taken into account by using two equivalent spring in the numerical model. Available experimental results from the literature are used to validate the finite element analysis. The moment capacities obtained from the numerical investigation are compared with current cold-formed design specifications. The comparison of moment capacities shows that current design provisions are over-conservative to predict buckling strength.

The role of structural health monitoring (SHM) in detection of post-earthquake damage to buildings is well established, and the same is extended to seismically isolated buildings in this research. In this study, a steel structure was considered with the isolation system which consists of elastomeric bearings. Numerical models were developed using SAP2000. The damage in the building was introduced by reducing the stiffness of all isolators in both horizontal directions unequally. After nonlinear response history analysis, the responses at two different floor levels of the healthy and damaged isolated superstructure were obtained, which are filtered using singular spectral analysis (SSA) and reconstructed using the dominant time series. The reconstructed responses were used to form a matrix that is decomposed, and singular vectors are obtained. The difference in the angle made by the singular vector in two-dimensional space obtained for healthy and damaged cases is the parameter for damage detection. SSA has successfully filtered the output responses, and the proposed algorithm has efficiently used the reconstructed responses to identify the damage in the structure.

This paper reports the study on the behaviour and strength of built-up cold-formed steel battened columns. The pin ended built-up columns composed of two web-stiffened cold-formed steel lipped channel sections positioned face to face at differing spacing which have been connected by the batten plates. The nonlinear 3D-numerical modelling was developed using ABAQUS software. The numerical results were validated with the results reported in the literature. The parametric study was conducted by changing the overall slenderness ratio of the web-stiffened channel sections. The dimensions of two identical web-stiffened lipped channel cross-sections have been selected based on pre-qualified limitations of North American Specifications. The column design strength, load-axial shortening and their buckled shapes at failure were observed and reported in this paper. A theoretical investigation was conducted based on the AISI S100-2016 specification for cold-formed steel columns, and the ultimate load capacity was predicted. Thus, the results obtained from numerical study and the theoretical study are compared and the conclusion drawn from this study.

A numerical investigation on cold-formed ferritic stainless steel hollow columns with perforation at mid-height was accomplished using Finite Element (FE) Analysis. The cold-formed ferritic stainless steel hollow columns offer high resistance to compression, bending and torsion. Perforations help in optimizing the material utility effectively. ABAQUS software is used to carry out the FE modelling. The cross-sectional dimensions for the parametric study were selected in accordance with the sizes available in the market such that wide range of perforation diameter to flat width ratio for different cross-sections can be achieved. Different width to thickness ratio for various cross-sections shows noteworthy effects in the strength of the columns. In the estimation of the elastic flexural buckling stress, the effects of perforations was considered in accordance with the guidelines provided in the AISI S100-2016. The axial compression capacity of the specimens was also predicted by Direct Strength Method (DSM) adopted in North American Specification AISI S100-2016. The results computed by existing DSM equations were compared with the numerical analysis strengths and the conclusions were drawn.

Equations and values provided by the American Institute of Steel Construction (AISC 360–05) and literature using elastic analysis to determine the value of moment gradient factor (Cb) are used for beams that buckle in the inelastic range also. The effect of moment gradient is proved by the use of an equivalent moment gradient factor Cb whose value is always greater than unity. This factor depends on the type of loading, position of loading from the shear centre and support conditions for the beam in the unbraced length. This paper develops a 3D finite element model of a Castellated Beam (CB) in ABAQUS/CAE, to determine the effect of beam slenderness and position of loading from the shear centre on Cb in the inelastic range due to point load and uniformly distributed load. The variation in Cb given in AISC for Point Load (PL) and Uniformly Distributed Load (UDL) is found at the shear centre and the bottom flange in the inelastic range. This variation can be eliminated by introducing a reduction factor for Cb in the inelastic range of castellated beams.

The previous research on cold-formed-steel (CFS) built-up compression members has been dominated by-adopting channels as chord members. The use of channel sections as chord members limits the gap extension between the chord members to one direction only. This gives adoption of angle sections as chord elements a better edge over channel sections. However, the little research output available on CFS built-up compression members composed of plain angles indicated early local buckling formation at the initial steps of compressive axial loading. Lipped angle sections can substantially enhance the buckling strength of these columns by prolonging the early local buckling. This study reports a numerically performed on CFS built-up compression members formed with of edge-stiffened angles under concentric compressive loading. Based on global slenderness all the three categories of columns, were studied. Also, the compactness of the angle sections as well as the batten spacing was varied. Lastly, the numerical axial strengths were compared against the current North American Standard (NAS) strengths.

Cold-formed steel-sheathed shear wall panels are a reliable lateral force-resisting systems in low and mid-rise cold-formed steel buildings. The mechanics of shear wall behavior is highly complex due to nonlinear interaction of different components which are individually nonlinear in behavior. Due to the complexity in their behavior, especially, their dependence on various parameters, numerous experiments were conducted to understand their response. So, there is a need for a comprehensive understanding, bringing together the results of various experiments conducted on CFS shear wall panels using standard methods by researchers across the globe. This paper extracts the published experimental data (numbering more than 400 experiments) on laterally loaded CFS shear wall panels by different researchers to compare the effect of different parameters like type of sheathing, thickness, screw spacing, aspect ratio, stud dimensions, and so on. This analysis gives a fairly good understanding of the behavior of CFS shear walls and the influence of various parameters so that quick conclusions can be drawn on proportioning, dimensioning, choice of sheathing, and designing the CFS shear walls.

Cellular steel beams have proved to be one of the most significant developments in steel construction. The introduction of an opening in the web of a beam alters the stress distribution within the member and also influences its collapse behaviour under the thermal load developed during a fire attack. Behaviour of cellular beams under fire can be predicted by performing simplified coupled (thermal-structural) field analysis. This paper covers the effect of parameters, viz. the span of the beam, size and spacing of the openings (cellularity), and load ratio on the behaviour of cellular beams with hinge–hinge support conditions under a uniform moment and uniform elevated temperature. The present numerical study is based on finite element analysis (FEA) which covers the both geometrical and material nonlinearity. Moreover, in this study, the material degradation at elevated temperature is not considered, and hence, the temperature at which deformations increase rapidly indicates the upper limit of web yield temperature. The result from the present study shows that the cellularity, load ratio, and span of the beam have a significant effect on temperature-deformation behaviour and theoretical web yield temperature of beams.

Cold-formed steel (CFS) is a new constructional material. The CFS sections have advantages like light weight, remoulability, etc. when compared with hot-rolled steel sections. CFS sections are extremely thin walled. This configuration gives them advantageous post reserve strength when used as structural element and compared with hot-rolled sections. However, research is needed to develop firm basis for such sections in comparison with typically used hot-rolled sections. Direct strength method (DSM) is a novel method presented as an alternative to effective width method. The use of such sections on field has been started. Buckling analysis and behaviour is an important criterion in direct strength method. Here, buckling analysis is carried in CUFSM software. Parametric study such as effect of longitudinal stiffener in cold-formed steel cross section, behaviour of different configuration of cold-formed steel like folded-flange and sigma is carried out. This study showed that direct strength method can be used as an alternative to effective width method given in IS 801-1975. Also, the upgrade in capacity of the cross section through longitudinal stiffener is also proved through buckling analysis.

This work tries to study the flexural–torsional couplings in thin-walled composite beams having variable stiffness. Variable stiffness composites (VSC) are manufactured with curvilinear fibres. Compared with straight fibre laminates, variable angle tow sections have improved structural response as they redistribute the in-plane stresses. A generalized beam kinematic model which considers the effect of flexural, torsional and warping deformations is adopted and using the principle of minimum potential energy, governing set of equations are derived. The variable fibre angles are defined using a general Lagrangian polynomial and as a special case, linearly varied fibre angles are studied. The transverse shear deformation effects are neglected in the present model and through set of C1 continuity finite elements, governing equations are numerically solved. The results are validated for the constant fibre angle composites and further, important observations are drawn on the coupled response of thin-walled VSCs. The present kinematic model and the numerical scheme is capable of extending the problem to further study the vibration and stability response of these composites.

Cold-formed steel (CFS) members are extensively used in building construction industry both as primary members to achieve cost-effectiveness over their hot-rolled counterpart and as secondary elements between main frameworks. In this work, cold-rolled lipped channel beams (LCB) were studied for various end moment cases. A suitable finite-element (FE) model intended for this study was adopted. Accuracy of developed FE models involved in this study was validated with experimental and numerical results available in the literature, which were further used to perform parametric study to evaluate the critical buckling capacity of selected beam sections. An extensive FE parametric study was carried out using commercial software package ABAQUS. This paper reports on series of investigation done on available cross-sections from Indian standards to evaluate critical buckling strength and ultimate moment capacity of these beams with varying moment, cross-section, length, and material properties. The beams were subjected to end moment along the span generated by applying a series of tensile and compressive loads above and below neutral axis (NA) forming a triangular distribution. The study also includes effects of uniform and non-uniform bending moment distribution along the span on buckling capacity. Idealized simply supported end conditions with warping free ends were used.

A numerical investigation on steel I-beams with reinforced web openings failing in flexural and shear using the commercial finite element software, ANSYS is presented and discussed in this paper. Web openings in steel beams are of various shapes like hexagonal, circular, rectangular and octagonal, which they are prepared from standard hot rolled steel I section. The main benefit of these members is to monitor service ducts through the openings as well as cost saving by economic use of material. The existence of the web openings deviates the beam failure behaviour around the openings over the parent beam. The additional failure modes named as Vierendeel mechanism along with regular failure modes like local buckling of web and flange, lateral torsional bucking, shear buckling, etc. comes into existence. The present study emphasizes on improving the performance of the steel beam with reinforced web openings. All the models of specimens have been fabricated from an original I section. The parametric investigation shows that reinforced web opening beams by adding high strength steel stiffeners around the web opening was very much effective. As compared to original I section beam, there is a 30% increase in the ultimate strength capacity of web expanded beams. The failure modes found to be similar both in with and without reinforcement around the openings.

Castellated Element is a structural element made from the structural steel I section which has been used as a structural beam as well as a column for the past few decades in the construction field due to its high value of the moment of inertia. This paper is focusing on the determination of the ultimate load carrying capacity of the castellated beam for an irregular dodecahedron web opening and its results are compared with a castellated beam of hexagonal web opening. The criteria considered are deflection and the ultimate load carrying capacity of the beam by the varying parameters, like depth of the section, depth of opening and opening angle. ISMB 150 is considered as a parent beam for the creating the model of the castellated beam. The depth of the castellated beam (CB225, CB240 and CB255) is increased with an expansion ratio of 1.5, 1.6 and 1.7, respectively. The FEM software (ANSYS) is used for the numerical analysis of the castellated beam.

It’s been so long that hot rolled I-beams are being used across the world for construction. The stability of steel structure is certainly influenced by decreasing stiffness during heating and non-linear response of stress–strain at elevated temperature when subjected to fire. Temperature is one of the reasons for failure of the structure which makes the study of effect of temperature on steel structure important. This paper represents an analytical study of the performance of geometrically perfect steel section under the elevated temperature. The analysis is based on multi-linear isotropic material which uses finite element method and is functionally affected by temperature. A major spotlight of the paper is to compile the past studies on the material, stress–strain curve of steel and effect of temperature on it. The different parameters selected for the comparison are applied loads, deformation, maximum equivalent stress, plastic region, elastic region, respectively.

The gusset plates in steel buildings and bridges play vital role in transfer forces and maintaining the overall structural integrity, but are relatively overlooked in design. In this study, a typical case of corner gusset plate welded to the beam-column joint and connected to the tension brace by single row of two and three bolts is considered. A simple 2-D model of corner gusset plate is developed to perform geometric and material nonlinear analysis for various load ranges and brace angles, with the help of ANSYS—a commercial finite element software. The minimum thickness of the gusset plate required to prevent rupture for each case is noted. The required thickness of gusset plates as per Whitmore’s theory, Indian (IS 800:2007), European (EN 1993-1-1: EC3) and American (ANSI/AISC 360-16) standards are also calculated. In comparison, significant difference in the required thickness of gusset plates as per finite element analysis and the considered codal provisions is observed. The maximum thicknesses obtained is specified as the design thickness for each case, which may serve as a guide or design aid for structural engineers.

Steel moment resisting frames are one of the most popular structural systems, which are used extensively for low to high-rise buildings in varying seismic regions around the world. Even though the use of structural steel in India is quite less in comparison to reinforced concrete structures, steel moment resisting frames are used extensively in industrial as well as commercial projects. The special steel moment resisting frames are a special category of this system, which are specifically detailed to undergo large inelastic cyclic deformation in regions of high seismicity. This paper addresses the design of special moment resting frame mentioned in Indian steel code IS 800:2007 and provides suggestions in terms of improving the inelastic response of the system. The limitations in terms of qualified and efficient Indian steel sections available for use in moment frames have been highlighted explicitly. Additionally, the inelastic cyclic performance of steel special moment resisting frames designed using Indian design code has been assessed under design basis and maximum considered earthquake hazard levels. Performance in terms of inter-storey drift, failure mechanism, material consumption, etc. has been compared to assess the design efficiency.

When plate girders are made up using plates of different strength in flanges and web, they are called hybrid plate girders. Increased use of hybrid beams is a condensing cost of steel structure and enhances the load-carrying capacity. The flanges are made of high-performance steel (HPS) of grade 460 Mpa and a web of lesser grade 345 Mpa. The analytical test has been carried out on twelve I-shaped girders in which six with a hybrid and six with a homogenous section. The analysis has implemented three-dimensional nonlinear finite-element models. Finite-element modeling of steel girder with or without opening is studied using ANSYS 12.0. The high-performance steels (HPS) have excellent stiffness and weldability, crack resistance features with having high yield strength. The analytical models consist of steel girders with a hexagonal web opening, without opening reinforcement. Opening in the beam is adaptable for its high strength to weight ratio and increase in depth of section without any further weight. So, that lighter section can be considered with consequent cost saving. Results are presented in terms of load–deflection behavior, failure mode and von Mises stress concentration. From the analytical results, it has been observed that the hybrid girder has a higher load-carrying capacity when compared with homogenous specimens.

Steel columns subjected to fire are prone to significant variation of boundary restraints while being exposed to fire loading. This paper presents the effect of end restraints on the behavior of hot rolled steel columns under uniform temperature profile (ISO 834-1: 1999) studied numerically. Nonlinear finite-element analysis was done using ABAQUS. Typical slenderness ratio (39), pre-applied axial load ratio (0.2, 0.4 and 0.6) and pre-applied moment ratio (0.1, 0.15 and 0.2) were considered in the present study. In addition to the above, constant axial restraint ratio (0, 0.2, 0.4 and 0.6) within the range as reported in Broadgate phase-8 fire report (0.1–0.9) and varying rotational restraint ratio (0, 2.81, 5.45 and 20.66) with increase in temperature as observed from Cardington test (1998) are used in the analysis. Based on one hundred and forty four trials done, buckling and critical temperature was plotted to assess the interactive effect of various parameters mentioned above.

Several theories are available in the literature to predict the ultimate shear resistance of plate girders, generally known as tension field theories. It is already found out, by many researchers, that the prediction of the majority of the models is mostly over-conservative for non-rigid end post steel plate girders. So, there is a need for the development of accurate finite element models, which could predict the ultimate strength better than the available theoretical models. This paper makes a comparison between the ultimate shear resistance of 12 non-rigid end post girders, from experimental data available in the literature, and some of the prominent tension field prediction models, such as Basler’s model, the Cardiff model, and Hӧglund’s model. There are many factors which affect the ultimate shear resistance of girders such as geometric imperfections, material nonlinearity, and boundary conditions. All of these factors need to be addressed to arrive at an improved finite element analysis, which can accurately predict the ultimate shear resistance of the girder. This paper comprehensively describes the finite element analysis, which includes the selection of material model, initial imperfection, element type, meshing and analysis methodology, etc.

The responses of semi-rigid (SR) frames under earthquakes are different from the rigid frames. Earlier research work was focused on far-field earthquakes, whereas the near-field (NF) earthquakes are crucial for civil engineering structures. In this paper, an extensive study is carried out to investigate the response behavior of semi-rigid frames for NF earthquakes with fling step and directivity effects. For this purpose, a ten-story steel frame is analyzed for four different earthquakes, two with near-field with directivity effect and one with the fling step effect and far-field earthquake. The PGV-to-PGA ratio is varied for NF earthquakes with directivity effects. A nonlinear time-history analysis is carried out for four earthquakes. The response quantities of interest include the maximum top-floor displacement, maximum inter-story drift ratio, total number of plastic hinges, SRSS of the maximum plastic hinge rotations, and energy dissipation in SR frames. The results of the numerical study indicate that the response behavior for the NF earthquakes with the fling step and directivity effects is distinctly different both in nature and magnitude. The PGV-to-PGA ratio has a significant effect on the response behavior of the frame produced by the NF earthquake with the directivity effect.

Evaluation of the performance of semi-rigid (SR) frames for different types of earthquakes is a topical subject of research. In this paper, the seismic performance of SR frames is evaluated using the capacity spectrum method. One five-story rigid frame is analyzed in order to compare the relative performance with the semi-rigid frames. An ensemble of ten far-field earthquake ground motions is selected for determining the statistics related to the probability of exceedance (POE) of the performance criteria. The performance criterion for each seismic demand parameter (SDPs) is selected based on the engineering judgment. Assuming earthquake variability as a major source of uncertainty, the POE of the performance criterion of a seismic demand parameter is determined for each PGA level of the earthquake following a lognormal distribution. The SDPs, namely, the maximum inter-story drift ratio and maximum roof drift ratio at the performance point are obtained for a particular PGA. The results of the study indicate that the POE of the performance criterion considerably differs with the seismic demand parameter and the nature of the earthquake. Further, the POE values considerably vary with the stiffness parameter.

The paper presents an analysis of symmetrical steel moment-resisting framed (MRF) buildings to estimate the time period of vibration of the considered models of the buildings of varying height up to 5 storeys. The formula for the time period of the bare steel MRF building is given by the design code IS 1893(Part 1): 2016 in seismic analysis of the structures, but it is in the form of the height of the building as a primary factor. Many researchers have performed the studies to evaluate the time period of the steel MRF buildings and found that the different other parameters such as stiffness of the structure and base dimensions are also the influencing factors. It seems necessary to consider the effects of some other parameters of the structures also in the evaluation of the time period values. The paper presents the results of the analysis for the effects of the various parameters on time period of the building, i.e. stiffness of the structure, slab thickness for a particular number of bays in either direction, plan dimension, or plan area of the building. In the paper, different values of the time period have been obtained by dynamic analysis on considered building configurations for earthquake zone-III and presented the comparative analysis of period values concerning the code IS-1893.

The paper studies the designs of steel roof trusses under the effect of wind forces, illustrated in SP: 38–1987, which is a handbook for typified designs of structures with steel roof trusses. The review has been done as a comparative study, which compares the illustrated designs of SP 38 with the designs of the same trusses, taking the provisions of IS 875–1987(Part-III) into design considerations. The paper attempts to explore the scope of improvization of the handbook by updating the current designs and incorporating the revised factors (class of structure terrain specifications, permeability factor, height, and structure size) of wind force analysis as per IS 875 to create effective designs of steel trusses or industrial shed structures, providing these designs with updated provisions.

The objective of this paper is to review the illustrated designs of standard structural steel sections are given in Indian Standard Special Publications, SP 6(1):1964; ISI Handbook for structural engineers (Part-1)—Structural Steel Sections. The paper presents the analysis of different standard steel column sections using the provisions of IS 800: 2007 to evaluate the load-carrying capacity of axially loaded steel sections subjected to compression considering different parameters such as effective length, slenderness ratio, the radius of gyration, material yielding, and inelastic buckling. The paper presents a comparative study of the result of the load-carrying capacity of steel sections, obtained as per SP 6(1):1964 and calculated as per the provisions of IS 800:2007, to obtain optimum sections to fulfil the aspect of economic designs with the safety of the structure. It suggests that there is a need for improvization in illustrated designs of SP 6(1) to incorporate the design provisions of IS 800: 2007. The updated designs would be more useful for structural designers of the country for taking them as a reference.

In this investigation, effect of structural steel stiffening on the response of a simply supported reinforced concrete slab under air blast loading is examined. Herein, three different steel sections have been considered for the study, namely channel, I-section, and square tube. The sections are fixed on top of the concrete slab in two configurations. First configuration is developed by placing the steel beam such that its longitudinal axis is parallel to the slab surface, and in the second one, it is perpendicular to the slab surface. The dynamic response of the slab is analyzed with each combination based on the displacement at the center of the slab. The aim is to determine the steel section and configuration which mitigates the blast induced damage most efficiently. Concrete and structural steel are modeled using solid elements, while the reinforcement is modeled using beam elements. Karagozian & case concrete material model is used to define the non-linear and strain softening behavior of concrete. The results indicate that channel section with longitudinal axis parallel to the slab surface performs better than the other combinations of steel sections and configuration with all other parameters being same.

The construction of steel high rise building is proved to be more economical than those made of RCC. But one of the major drawbacks of steel is susceptible to fire as metals are good conductor of heat and electricity. On the other-hand, office buildings are equipped with so many accessories which are vulnerable to fire. When exposed to fire, commonly used steel section loses, some of its mechanical properties due to that elongation, deformation, buckling, or any other stresses are generated. Heavily loaded steel loses it designed safety margin at a temperature around 220 °C—regardless the grade of steel. Majority of the research works carried out in this field came out with different techniques to protect a steel structure from fire by means of making it fire resistant internally or externally. Some researches came up with different modelling and analysis tools to develop the fire resistance of structural steel. In this present paper, we presented the different alternatives discovered so far to improve the performance of steel on fire and behaviour of different structural members under various loading conditions are explained.

The process of soil response affecting structural deformations and vice-versa is termed as soil-structure interaction (SSI). Over last few decades, traditional belief of SSI being ever-beneficial to seismic response of structures has been challenged. There have been evidences of SSI induced damages in 1985 Mexico City, 1989 Loma Prieta, 1995 Kobe, and 2001 Bhuj earthquakes. Seismic structural response is a function of structural and foundation characteristics, underlying soil medium properties, and ground motion characteristics. This paper attempts to assess effects of SSI on performance of steel frames with semi-rigid connections during a seismic event. The rationale behind choosing this structural configuration is its gaining popularity and large potential drifts. Though semi-rigid frames offer advantages like adequate stiffness, strength, and economy as compared to rigid frames, large top displacements and inter-storey drifts can be of concern. Performance is assessed in terms of parameters such as natural period and inter-storey drifts. Substructure approach with dynamic impedance using simple physical models has been employed to consider SSI.

Buckling-restrained braced frames (BRBFs) are design for the seismic resisting purpose on the active seismic zones. The symmetrical hysteresis, high ductility, and large capacity to dissipate energy made this system superior to conventional concentrically-braced systems. Most of the past studies concluded that BRBFs might suffer from the excessive post-earthquake residual drift as compared to the other systems under the near-field earthquakes. The excessive residual drift in BRBFs is the main disadvantage, which is led us to the development of the self-centering buckling-restrained braced frames (SC-BRBFs). The better energy dissipation capacity, the absence of compressive buckling behavior of braces, high ductility, and reducing residual drift response make the SC-BRBs a preferred alternative over the conventional system like BRBFs. The study mainly focuses on the evaluation of the seismic response of SC-BRBFs under the near-field earthquakes. Three low, medium, and rise study frames, namely 3-story, 9-story, and 20-story SAC benchmark buildings (Ohtori in J Eng Mech 130:366–385, 2004), are considered for this study. The frames are designed based on AISC 341–2010 provisions. The SC-BRB is considered as the combine of buckling-restrained brace (BRB) and shape memory alloy (SMA) rods. These frames are modeled and analyzed using computer software OpenSees. A set of forty near-field ground motions are selected in the nonlinear dynamic (time history) analysis. The main parameters investigated are inter-story drift response and residual drift response. The analysis results for SC-BRBFs showed better performance as compared to conventional BRBs with the negligible residual drift response.

Trusses are commonly used in supporting roof structures, industrial building, auditorium, and warehouses. Trusses may be used efficiently in long distance span with minimum amount of material used. This is due to the internal loads of the members incurring only axial forces (in the direction of the member), i.e. either compression or tension. Sometimes, it creates difficulty to decide which truss configuration, span and rise would produce the most economical truss shape with minimum weight/mass. Thus, in this paper, thirty different conventional trusses of varying spans (10 m, 15 m, 20 m, and 25 m) and rise (1.5 m, 2.0 m, and 3.0 m) combinations have been analysed and designed with circular hollow section using STAAD. Pro V8i SS5. All the trusses have been designed as per IS 800:2007 (LSM). Moreover, all trusses are also studied for their practical weight as well as for optimum weight and compared to find out the economical truss profile.

Compression members buckle globally or locally, depending on the overall section slenderness and the local plate element slenderness. If plate elements buckle at a stress lower than the stress which would cause the section to buckle globally, the local buckling of the plate will control the overall section strength. When this occurs, the section is said to be composed of slender elements. There is extensive research on buckling of slender web, but hardly any research regarding behaviour of slender flanges have been undertaken. Therefore, to study the behaviour of beam with slender flanges, a group of I-sections were selected with varying flange width to thickness ratios ranging from slender to highly slender sections, different unbraced span lengths and end support conditions. The I-sections were modelled on ANSYS workbench with the aforementioned parameters and loading condition of uniformly distributed pressure over flange. The buckling load behaviour due to slender flanges w.r.t the changes in width, thickness, unbraced span lengths and end support conditions were obtained. Indian and American standard codes, IS 800–2007, IS 801 1975 and AISC 360–16 were referred.

Steel beam sections have mainly two failure modes: local buckling and lateral-torsional buckling, and interaction between these modes affects the critical load capacity of beams. Past case studies on structures such as World Trade Centre Tower 7 and large-scale fire experiments showed the vulnerability of steel buildings under elevated temperatures. In the case of the high-temperature gradient, floor beams suffer the local as well as global buckling collapse. Global failure at floor level leads to a progressive collapse of the steel structure buildings. In case of fire loading web of steel, section undergoes instability at the initial stage of fire loading. It leads to faster degradation of shear capacity and flexural capacity. This paper studies the inelastic lateral-torsional buckling behaviour, and moment capacities of the steel I-section beams. Beams are analysed under varying moment loadings with simply supported boundary conditions at elevated temperatures. A parametric study is presented to investigate the effect of loading cases and elevated temperature on the buckling capacity of the beam members. In this study, a total of 216 linear and nonlinear numerical model analysis are conducted using the finite element method (FEM) analysis with the help of a robust FEM-based ABAQUS software. It is observed from the numerical study that at elevated temperature the buckling capacity changes significantly compared to current design rules in Eurocode 3. It is also seen that the loading patterns have a vital effect on the buckling capacity of the beam.

In the present work, thermal blanket has been adopted as a thermal insulating material that is applied on the structural steel members as a thermal insulation measure, when the structural steel members are exposed to high temperature. In this work, a structural steel beam having an I section (ISMB450) having a span of 5 m is adopted with fixed end conditions exposed to a range of high temperatures (500ºC and 725ºC) separately. A heat transfer analysis in Abaqus is carried out to study the temperature distribution in the steel beam for different temperature exposures. The thermal blanket having different thicknesses is applied on to the surface of the steel beam along its entire span as thermal insulation. An optimum thickness of the thermal blanket is identified from this study that would insulate the steel beam from the temperature rise to take place on its surface, when exposed to high temperature based on the heat transfer analysis carried out such that, the thermally insulated steel beam is in stable condition when exposed to high temperature.

Steel braces are adopted in framed structures for providing adequate resistance to lateral loads like seismic loads. Under seismic loads, braces tend to buckle and under periodic loading, and they have less strength, stiffness, and resistance. All-steel buckling restrained braces are found to be excellent in dissipating energy caused due to catastrophic events. Recently, progressive collapse of framed structures has become an important topic of research since many buildings have collapsed due to this event. The structural designers require to design structural members to carry and dissipate huge stresses caused due to catastrophic loading. Although there exist different types of bracing systems like concentric bracing, eccentric bracing, and buckling restrained bracing, not many studies have been conducted to study the response of these bracing systems under progressive collapse scenario. In order to study the behaviour of all-steel buckling restrained braced frames towards progressive collapse, a brief review of literatures was conducted. Also, a review was conducted to determine the resistance offered by different types of braces when subjected to progressive collapse.

In this paper, Method of Initial Functions (MIF) has been applied to see the outcome of different types of loading on the behavior of steel beams. The MIF is an analytical process based on elasticity theory. This method gives the precise solution of problems without the use of hypothesis about the nature of stress and strain. A simply supported beam is analyzed for two different types of loading having the same intensity. Different loadings are uniformly distributed load and sinusoidal load. MIF results are equated with the bending theory, and salient conclusions are drawn.