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This book comprises select proceedings of the National Conference on Advances in Structural Technology (CoAST 2019). It brings together different applied and technological aspects of structural engineering. The main topics covered in this book include solid mechanics, composite structures, fluid-structure interaction, soil-structure interaction, structural safety, and structural health monitoring. The book also focuses on emerging structural materials and the different behavior of civil, mechanical, and aerospace structural systems. Given its contents, this book will be a useful reference for researchers and practitioners working in structural safety and engineering.



Seismic Control and Performance of Passive Hybrid Damper Under Near-Field Earthquakes

In structural engineering aspect, the inherent structural property of the building is not sufficient to control the structural response when it comes to strong earthquakes. The common control strategy used by researchers makes use of energy dissipating devices that absorb the energy imparted to the structure due to earthquake and dissipate the energy by their hysteresis nature. In this study, seismic response of a G + 4 storey building installed with a hybrid damper has been investigated. The hybrid damper system comprises of Viscous Fluid Damper (VFD) and Shape Memory Alloy (SMA). The performance of the building under near-field earthquakes, Tabas, Kobe, and Gebze earthquakes has been evaluated. The dampers have been installed at the base of the superstructure. SMA exhibits a good self-centering capability and is known for its superior super-elasticity properties. It is capable of dissipating energy through its hysteresis nature while maintaining a low level of residual displacement. VFD dissipates energy through the movement of fluid inside it, which minimizes both stress and displacement the structure due to seismic effect. The time history analysis result shows the effectiveness of hybrid damper for controlling the seismic forces acting on the structure. In this present study, there is a significant reduction in base shear and displacement by about 16% and 8% by using Hybrid damper when compared to VFD and SMA dampers. A comparative study is made showing the effect of the Hybrid damper in reducing the seismic responses for the selected near-field earthquakes.
Swabarna Roy, Swagato Das, Purnachandra Saha

Wall Effects on Terminal Velocity of Test Fuel Bundle in the Fuel Test Loop of High Flux Research Reactor

Fuel Test Loop (FTL) is a self-contained independent experimental loop which is designed for testing of nuclear fuel materials under simulated power reactor conditions in the High Flux Research Reactor being developed at BARC. It is a high-pressure loop with maximum operating pressure up to 17.5 MPa and maximum operating temperature up to 330 °C. The In-Pool Test Section of the FTL consists of a series of concentric tubes with different thicknesses and functionality. The test fuel bundle resides within the innermost Fuel Tube which is further enclosed within an internally insulated Pressure Tube which acts as a pressure boundary enclosure to the test fuel bundles. The present work deals with the investigation of wall effects on the terminal velocity of test fuel bundles falling under gravity within the In-Pool Test Section. While loading/unloading of the test fuel bundle, accidentally the fuel bundle may fall under the influence of gravity within the fluid filled Fuel Tube. The minimum gap between the fuel bundle and the fuel tube is 2 mm. Thus, the wall effects on the velocity of the falling fuel cannot be neglected. The purpose of the present work is to estimate this wall effects on the terminal velocity of the falling fuel in terms of Drag Coefficient. This involves, initially estimating drag characteristics and terminal velocities with wall effects for different geometries, and finally predicting the overall characteristics with the test fuel bundle as the geometry of interest. To fulfill this objective, an analytical methodology is established which has been validated through a commercial code.
G. Verma, S. Sengupta, S. Mammen, P. Mukherjee, P. V. Varde

Comparison of Seismic Performance of Composite (RCS) Frame with RC Frame Using Pushover Analysis

In this paper, comparison of seismic performance has been investigated between RCS (Reinforced Concrete column-Steel beam) composite frame and RCC (Reinforced cement concrete) frame using SAP2000 software. Nonlinear static analysis (pushover) is employed for evaluation of the seismic performance of both RCS and RC frames. Both the RCS and RC frames are similar in geometry, as well as sectional members used except the beams in RCS frame are replaced by steel member of the equivalent flexural capacity of beams in RC frame. Seismic performances of both RCS and RC frames in terms of base shear, spectral displacement, etc., are investigated. It has been observed that the RCS frame is more cost-effective than the RC frame of equivalent seismic performance.
Manoranjan Singh Oinam, S. S. Ningthoukhongjam

Investigating Load Withstand by L-Shape Concrete Cube, RCC Slab and to Safeguard Reinforcement of RCC Slab in Saltwater Environment Using Cathodic Protection

Structures constructed in reinforced cement concrete (RCC) are currently at risk when exposed to saltwater conditions. Eventually, RCC structure fails after the corrosion of reinforcement, reducing strength and its life. The investigation focuses on load-carrying capacity of slab specimen (RCC) and shear strength of L-shape concrete cubes after exposure to saltwater. The concrete of M20 mix was prepared using 53 grade cement to cast L-shape concrete cubes and reinforced slab specimen having 10 mm bar diameter. The size of RCC slab was 300 × 300 × 100 mm and L-shape cubes were prepared after cut of 90 × 150 × 60 mm in regular concrete cube with M-20 mix. After casting and curing of L-Shape cube and slabs, these specimens are exposed to 0.1 M NaCl water for curing. The L-Shape cubes after regular curing gave 12.21 MPa at 7 days and 19.11 MPa at 28 days of shear strength. Furthermore, shear strength increased from 13.42 MPa at 7 days to 21.07 MPa at 28 days after curing in 0.1 M NaCl water for 30 h. A D.C. power supply was used to accelerate the corrosion of steel in the slab at 0.02 mA/mm2. Slab specimens tested for 30 h were as follows: slab reinforcement as anode (P1), slab coated with sodium silicate and reinforcement as anode (P2) and slabs reinforcement as cathode (P3) in 0.1 M NaCl water with iron plate as anode. The failure loads of slabs were 41.75 kN for P1, 75.35 kN for P2 and 78.5 kN for P3 type. This study indicates L-shaped cubes after curing in NaCl environment can increase shear strength. In addition, cathodic protection to reinforcement in slab increases load-carrying capacity, ultimately increasing the life of RCC specimen.
C. F. Rajemahadik, M. M. Kulkarni, R. S. Durge, A. R. Kamble, S. B. Babar, P. A. Bansode

Performance Evaluation of Two-Way RC Slab Subjected to Blast Loading Using Finite Element Analysis

Recently, blast and impact have gained more importance in research work owing to the fact that these high-intensity events can completely destroy any structure, causing tremendous casualties and property loss. Therefore, for any structure to withstand such extreme events, it is important to consider the effect of blast and impact loading in their design. Research works on response and damage analysis of reinforced concrete structural components such as slabs, columns, beams and walls subjected to blast and impact are limited in the literature and are essential for assessing its vulnerability. The current work investigates the performance of two-way reinforced concrete (RC) slabs subjected to blast loading. To simulate the field blast tests on different slabs, initially, a numerical model is established in a finite element preprocessor (HyperMesh). Later on, with the help of a commercial simulation software package (LS-DYNA), the numerical analysis is carried out. The developed numerical model is validated with the results of an experimental work done on an RC slab subjected to air blast from previous research. The results of the developed model are found in close agreement with actual experimental results. The numerical parameters of the validated model are used to develop a probabilistic model to investigate the blast response of the slab designed in current work. The probabilistic model developed in this research is able to capture the damage phenomena and also capable enough to reproduce the dynamic response.
Kasturi Bhuyan, Kiran Kumar Jujjavarapu, Hrishikesh Sharma

Development of Fragility Curves for Different Types of RC Frame Structures

In this paper, seismic behaviors of different types of reinforced concrete (RC) frames conforming and non-conforming to strong column-weak beam (SCWB) design principles have been investigated using SAP2000. Nonlinear static (pushover) analysis has been employed to obtain the capacity curves of different RC frames. The fragility curves are then plotted from the capacity curves obtained from pushover analysis. The guidelines given in the HAZUS manual have been referred to for developing fragility curves. The performance points of RC frames conforming to SCWB design principles have been obtained at IO levels whereas those non-conforming to SCWB design principles have been obtained at LS levels. This shows that the damage of RC frames non-conforming to SCWB design principles will be severe than that of the RC frame conforming to SCWB design principles. Moreover, from the fragility curves, it has been observed that the RC frame non-conforming to SCWB design criteria frame has a higher probability of damage than that of the RC frame conforming to SCWB criteria at a particular value of spectral displacement.
Neeva Ahanthem, S. S. Ningthoukhongjam

Smart Lightweight MR Damper for the Enhancement of Seismic Mitigation

Magnetorheological (MR) fluids with exceptional rheological properties are skilled in exhibiting quick performance to control vibrations during earthquakes. The significant damping properties of MR fluids were effectively controlled with the help of externally applied magnetic field and current. Currently, MR fluids with nano Fe3O4 iron particles are used in the preparation of MR fluid to reduce sedimentation. Fabrication of MR damper consists of nylon material to reduce the weight and resist high-temperature distortion. The weight of the proposed MR damper was about 445 g with the magnetic core. The MR fluid of proportions 30% (MRF30), 45% (MRF 45) and 60% (MRF 60) of iron particle is prepared, and the cyclic load test frequency is 0.5 Hz and amplitude, ± 5 mm. The maximum damping force was found to be 1.032 kN obtained from the MR fluid containing 60% Fe3O4 particles in magnatec oil. For variable frequency, the time history loading test was done with El Centro ground acceleration data where the maximum damping force for MRF 60 is 1.3 kN.
C. Daniel, G. Hemalatha, L. Sarala, D. Tensing, S. Sundar Manoharan

Rheological Behavior of Geopolymer Mortar with Fly Ash, Slag and Their Blending

In the present paper, an attempt has been made to study the rheological behavior of geopolymer mortar made with fly ash, ground granulated blast furnace slag (slag) and their blending (1:1) as source materials. NaOH solution was used as an alkaline activator. The molar concentrations of the alkaline activator used in the present study were 4, 8, 12 and 14.5 M. For the preparation of mortar, the ratio of source material to sand was kept constant at 1:3. Three different ratios of activator to binder were considered in the present experimental investigation. Experiments were conducted by a rotational viscometer. It was observed that the degree of thixotropy of the slag-based geopolymer mortar reduces after the addition of fly ash. Down curve of geopolymer mortar followed the Bingham model with good accuracy with and without blending. Rheological parameters of slag-based mortar reduced significantly after blending with fly ash.
Biswajit Roy, Aminul Islam Laskar

Effect of Pile Spacing and Raft Thickness on the Behaviour of Piled-Raft Foundation—A Parametric Study Using FEM

This paper presents a parametric study of piled-raft foundation under static loading in homogenous soft clay and loose sand. 3D finite element analyses have been carried out for conventional unpiled raft as well as piled rafts with 4 and 9 number of piles underneath the raft. A three-dimensional finite element package for soil and foundation is used for plane strain, linear elastic modelling of piled-raft system, and Mohr–Coulomb yield criterion is used to represent the two soil types as elastic-perfect plastic material. The loading parameters, length and diameter of circular piles, Poisson’s ratio and elastic moduli of raft, piles and soil are kept constant throughout the analyses. Focus is thereby on two parameters—pile spacing, i.e. S/D ratio and raft thickness. Variation in the peak values of settlements, bending moments, torsion, axial forces and shear forces are investigated in both raft and piles due to varying pile spacing and raft thickness in clay and sandy soil. The general conclusion of this study for providing a piled-raft foundation is to design a flexible/semi-flexible raft of optimum thickness and S/D ratio so that the deflections and force parameters on the raft and the piles are within permissible limits and the piles can effectively act as settlement reducers in addition to sharing of loads.
Mukul Kalita, Utpal Kumar Nath, Palash Jyoti Hazarika

Removal of VOCs and Improvement of Indoor Air Quality Using Activated Carbon Air Filter

Volatile Organic Compound (VOC) is one of the most common air pollutants emitted from industries like Chemical, Petrochemical, as well as when plastics are burned. It is very harmful to our environment which affects climate change, the life cycle of plants, and the health of all living beings. So, it is necessary to control its emission for improvement of air quality which is beneficial to the indoor environment. The objective of the study is to review the performance of different activated carbon-based air filters. Various activated carbon-based techniques are the use of coconut shells, photocatalyst TiO2, Polystyrene foam, sorption-type, and granular activated carbon. Several aldehydes and ketones have been removed effectively using activated coconut shell. Removal of nitrogen oxide was possible by using TiO2-based activated carbon. It is observed from this study that activated carbon-based techniques are effective for the removal of VOCs and enhancing the indoor air quality.
Sujon Mondal, Soham De, Purnachandra Saha

A Comparative Study of Normal and Self-compacting Concrete

In this paper, the experimental results of both Normal Concrete (NC) and Self-Compacting Concrete (SCC) are presented. Both the fresh and hardened properties were investigated. The SCC was developed by replacing 20% of Ordinary Portland Cement (OPC) by Fly ash (FA), so that the amount OPC is almost same in both NC and SCC. The workability of the mix increases with the inclusion of FA and the mix becomes cost-effective. For workability, the slump test was conducted on NC while for SCC, slump flow, T50 time, V-funnel, L-box, U-box and J-ring tests were conducted. The water/binder (w/b) ratio was kept constant for both the NC and SCC. For M25 grade concrete, cubes of size 100 mm, cylinders of size 100 mm × 200 mm and beams of size 100 mm × 100 mm × 500 mm were cast to find the compressive, split tensile and flexural strengths, respectively. The samples were tested after curing in tap water for 7, 28, 56 and 90 days. The water absorption of both NC and SCC was also studied up to 90 days. The XRD analysis of both the concrete samples was also carried out to investigate the microstructural changes.
Deep Tripathi, Rakesh Kumar, P. K. Mehta, Amrendra Singh

Evaluating Toughness as a Parameter to Determine the Fatigue Life of Wollastonite Microfiber Reinforced High Flow Pavement Quality Concrete

Rigid pavements are designed on the basis of flexural strength, since the concrete is brittle and supposed to show little strains post-peak stress. The stress ratio, which is the ratio of flexural stresses to flexural strength generally determines the fatigue life of the pavement. Under service load, pavements face a continuous reduction in flexural strength on account of propagating cracks, which causes fatigue damage. But the evolution of cracks in quasi-ductile concrete is different, which is somehow anticipated to depend upon the toughness of concrete. Toughness is the area under load deflection curve and indicates the energy possessed by concrete. Under repetitive loading, there is continuous reduction in strength of concrete but the total energy possessed by concrete should not vary. This paper, thus tries to find the relationship of fatigue life with stress ratio, and fatigue life with toughness and stress ratio together to check for the validity of stress ratio-fatigue life equation in case of quasi-ductile concrete. Equations have been generated for normal pavement quality concrete (PQC), flyash admixed and wollastonite microfiber reinforced PQC. Results proved that even though the toughness affects the formation of flexural stresses in any kind of concrete, stress ratio is singularly effective for finding out the fatigue life, since it reflects both toughness (through flexural stresses) and flexural strength. Quantitatively, WMF-reinforced concrete has very high fatigue life than normal PQC and flyash admixed PQC, respectively.
Shashi Kant Sharma, K. P. Marisarla Chaitanya

Response of Single and Multilayered Flexible Base for Static and Earthquake Loading Under Framed RC Structure

As it is well known that, if the effect of Soil–Structure Interaction (SSI) is to be assessed, then structure must be placed on physical soil mass with actual properties to get the perfect behavior of soil and structure rather than Winkler’s Spring Model. In case of non-interaction analysis problem, the structure is to be placed on non-yielding support; hence, it is assumed that there will be zero displacement beneath the footing or displacement is considered less than the permissible limits as stated by standards. However, the actual condition is totally different and settlement due to soil properties can be seen by naked eyes. In non-interaction analysis, the footings are design based on Safe Bearing Capacity (SBC) of soil, but as per literature review and SSI analysis done in this paper, it is observed that the footing deformation is more than permissible value and stress value just below the footing is also higher than SBC. To demonstrate the actual nature of the ground response, a multi-storey frame is analyzed with four different cases. The SSI system modeling is done using finite element method ANSYS Software program. The portal frame is modeled as elastic (linear), whereas the ground is modeled as both elastic–plastic (linear elastic and non-linear). The study gives insight into the variation of deformation and stress intensities in soil mass while considering linear and non-linear behavior of ground. In the analysis of soil, the deformation in soil mass is plotted along with depth and discussed, whereas stresses are plotted along the width with a variation for different types of soil and different loadings. Thus, after complete analysis, it is observed that both the stresses and deformations are out of permissible limit after considering the actual stiffness of soil.
Gaurav D. Dhadse, G. D. Ramtekkar, Govardhan Bhat

Analysis of Moment and Torsion in Skew Plates Using ABAQUS

The increased utilization of skew plates in thin-walled structural components of aircrafts, submarines, automobiles, and other high-performance application areas have necessitated a strong need to understand their characteristics. This paper presents the bending analysis of isotropic skewed plates using the finite element software ABAQUS Simulia. Modeling was done in ABAQUS Simulia using the SC8R element as it gave better results for shell structures. An analysis is done on skew plates of various skew angles and aspect ratios with all end clamps subjected to uniform pressure and the results are generated. The effect of skew angle, aspect ratio, and thickness of the plate on various parameters like bending and torsional moments, support shear, and deflection are separately presented which may serve as a benchmark for further research. From the results, it is observed that the maximum central deflection decreases with an increase in skew angle. The negative reaction was found to develop at the acute angle corners and it increased as the skew angle increased. Bending moments were found to decrease and torsion was found to increase with an increase in skew angle.
Anjani Kumar Shukla, Vishal Koruthu Philip, P. R. Maiti

Behavior of Liquid Storage Tank Under Multidirectional Excitation

By revoking the effect of vertical component in the analysis of different response quantities of LST may differ from the true response of structure during a seismic event. This paper aims to study the effect of the vertical component of an earthquake on various response quantities, namely tank wall displacement, surcharge at the free surface of the water, overturning moment, and base shear. The study is compiled with the help of nonlinear time history analysis in an explicit finite element module on ABAQUS platform. For illustration, a 10-m long-rectangular liquid storage tank has been modeled by using a solid element with fluid medium modified by the arbitrary Lagrangian and Eulerian (ALE). Investigation for response is done first with bidirectional and then with the vertical component is considered. Some notable conclusions of the study include vertical component alone, which increases the responses to an order of about 30%.
Sourabh Vern, Mahendra Kumar Shrimali, Shiv Dayal Bharti, Tushar Kanti Datta

Osdag: A Software for Structural Steel Design Using IS 800:2007

This paper discusses the research and development undertaken to develop a free and open-source software called Osdag® (Open Steel Design and Graphics) for the design and detailing of steel structures, at the Indian Institute of Technology Bombay. Osdag is a model-based platform-independent software having several modules of structural steel design following the specifications of IS 800:2007 and other relevant standards. It is being developed on interpreted, high-level, general-purpose object-oriented programming (OOP) language Python, and other Python-based tools. An interactive graphical user interface (GUI) is provided with proper validations of user input and maintenance of log files. The log messages provide the user with valuable information on the failure of trial design and suggest required modification(s). The software also features the inclusion of graphics for real-time 3D visualization of the structural component details. The CAD files developed from Osdag can be exported to conventional CAD manipulation software. Osdag generates a design report, showing details of all the inputs, design considerations, fabrication drawings, and—most importantly—details of each design and detailing checks according to the Indian Standards with reference to the appropriate clause number. The current version of Osdag (Release: 2018-06-21) contains connection design modules for shear connections (fin plate, end plate, cleat angle, and seated angle) and beam-to-beam moment connections, namely cover plate and extended end plate connections.
Siddhartha Ghosh, Danish Ansari, Ajmal Babu Mahasrankintakam, Dharma Teja Nuli, Reshma Konjari, M. Swathi, Subhrajit Dutta

Experimental and Analytical Investigations on Two-Way Flexural Capacity of Biaxial Voided Slab

The rise in urbanisation and subsequent demand for infrastructure accelerates the use of concrete as a construction material. Conventional design practices need large member sizes to fulfil architectural and structural requirements. Hence, the size of structural members such as slab, beam, column, etc., significantly affects the quantity of concrete used. This calls for the need to optimise the use of concrete to reduce the self-weight of structure. The present study explores the possibility of biaxial voided slabs as a substitute for conventional reinforced concrete slabs. A typical biaxial voided slab eliminates concrete from the middle of the floor slab by introducing voids and it leads to a significant reduction in self-weight, about 30–50%. However, these voids reduce the sectional area of slab concrete, which leads to a reduction in flexural stiffness and shear resistance. The behaviour of the biaxial voided slab subjected to two-way flexure is discussed. Experiments are carried out to determine two-way flexural behaviour of the two-way slab with sphere shape voids by adopting 16-point loads. The obtained experimental results of strength and serviceability criteria are compared for slabs with and without voids. It is found that the flexural capacity of the two-way slab with biaxial voids is the same as a solid slab, with a minor reduction in its flexural stiffness. Furthermore, an analytical study is carried out based on the yield line analysis to predict the flexural capacity of the slab and compared with experimental results. It is evidenced that 16-point load is equivalent to 89% of uniformly distributed load and the flexural capacity of void slabs can be predicted by using yield line analysis as used in the conventional solid slab.
R. Sagadevan, B. N. Rao

A Comparative Study of Seismic Response of Structure Isolated with Triple Friction Pendulum Bearing and Single Friction Pendulum Bearing Under Different Hazard Levels of Earthquake

The Triple Friction Pendulum (TFP) bearing is highly adaptive in nature that contains three effective pendula with four spherical sliding surfaces. By considering desirable displacement capacity with effective damping and period, TFP systems are to be designed. A comparative response of the building isolated by the Single Friction Pendulum (FPS) and Triple Friction Pendulum (TFP) with same effective damping, effective time period, and displacement capacity under different hazard levels of earthquake along with its mathematical models. It shows that the performance of TFP is superior over the FPS. Owing to its multiple sliders, which dissipate seismic energy and distribute sliding displacement over the multiple surfaces. It is also found that the TFP bearing stiffens at low level of input, softens with increasing input, and then stiffens again at higher levels of input. Hence, it behaves adaptively in nature under different hazard levels of earthquake.
Ankit Sodha, Sandip Vasanwala, Devesh Soni, Shailendra Kumar

Assessment of Important Parameters for Seismic Analysis and Design of Confined Masonry Buildings: A Review

Confined masonry (CM) building is emerging as a popular building construction system in many earthquake-prone countries including India. This building type has performed really well in several destructive earthquakes, even though it started as an informal construction. A finished CM building looks like a reinforced concrete (RC) infilled structure, however, the structural behavior of both the systems is quite different. Apart from excellent performances in seismic events, it is very cost-effective and easier to construct. But the design methodology for CM buildings is yet to be standardized for Indian conditions due to lack of research. Therefore, it is important to study the various factors affecting the performance of CM building in comparison to other building types. The objective of this study is to identify the parameters influencing the seismic performance of CM buildings. The dependency of seismic response of CM buildings on different key parameters such as material and geometric properties, gravity loads, amount of longitudinal steel present in tie-columns, and aspect ratio of the wall is discussed in this paper.
Bonisha Borah, Vaibhav Singhal, Hemant B. Kaushik

Design and Performance Criteria for Fire-Resistant Design of Structures––An Overview

Concrete, despite being inherently fire resistant, cannot be considered as a fire-proof material. It undergoes substantial variation in its characteristics during exposure to elevated temperatures. These variations may become hazardous for structural stability and serviceability depending upon the type and extent of exposure. Moreover, high-strength concrete, which is commonly used in tall buildings, may perform poorly against fire due to its high binder content and very low permeability. Despite all the aforementioned factors, fire resistance design of structural members has been given very restricted consideration in the current Indian practice. Although several standards provide guidelines to achieve fire safety in structures, the provisions for high-strength concrete and spalling prevention are not specifically available in the major international and national standards. This paper attempts to compare the provisions corresponding to fire-resistant design in Indian standard with the respective provisions of other country standards, e.g., ACI 216 [3], NZS 3101 [4], EN 1992–2 [8], etc. Comparison parameters primarily include the design requirements for various structural members to improve their fire resistance. Furthermore, suitable recommendations for Indian Codal provisions are attempted in the latter part of the paper to achieve superior performance under elevated temperatures.
Nitant Upasani, Mansi Bansal, Ashirbad Satapathy, Sanket Rawat, G. Muthukumar

Wear Behavior of Marble Dust Filled Aluminum Metal Matrix Structural Composite

In the present work, the stir-casting method for the preparation of Al-6063 composites was adopted. Samples were prepared with the reinforcing different weight % of marble dust (2%, 4%, 6%wt) and fixed wt % of graphite (Gr) (2%wt), glass fiber (2%wt), and boron carbide (B4C) (4%wt) by stir casting setup. The present work has provided the descriptions of the wear characteristics of the marble dust filled Al-6063 composites. A series of erosion experiments were conducted on the composites under various test conditions using an air jet erosion machine. It was seen that with the incorporation of marble dust powder, the wear resistance property of composites was significantly improved.
Hariom Tripathi, Sandeep Kashyap

Quantifying Uncertainty in Structural Responses of Polymer Sandwich Composites: A Comparative Analysis of Neural Networks

The manufacturing and fabrication of complex polymer sandwich composite plates involve various processes and parameters, and the lack of control over them causes uncertain system parameters. It is essential to consider randomness in varying parameters to analyse polymer sandwich composite plates. The present study portrays uncertainty quantification in structural responses (such as natural frequencies) of polymer sandwich composite plates using the surrogate model. The comparative study of artificial neural network (ANN) and polynomial neural network (PNN) for uncertain structural responses of the sandwich plate is presented. The proposed ANN as well as PNN algorithm is found to be convergent with intensive Monte Carlo simulation (MCS) for uncertain vibration responses. The predictability of PNN is observed to be more efficient than that of ANN. Typical material properties, skew angle, fibre orientation angle, number of laminate and core thickness are randomly varied to quantify the uncertainties. The use of both the surrogate models (PNN and ANN) results in a significant saving of computational time and cost compared to that of full-scale intensive finite element-based MCS approach.
R. R. Kumar, T. Mukhopadhyay, K. M. Pandey, S. Dey

Buckling Analysis of Braced Frames under Axial and Lateral Loadings: The Effect of Bracing Location

In this study, buckling analyses of two-dimensional steel frames are carried out considering various combinations of 3 bays and 3 stories, with and without braces under lateral and vertical loads separately. The main objective of the study is to investigate the effect of a particular bracing location on the overall buckling behavior of frames incorporating a single diagonal brace or an X (cross) brace in either of the bays of first story or in the other closed loops of the frame, individually. The effects are compared for bare frames, fully braced frames, one other bracing type and for the diagonal braces having the same slenderness as that of beams and columns. Such type of analysis is useful for the safe design of framed structures against buckling.
Narayan, Krishna Kant Pathak

A Study on Moment–Curvature Relationships for REINFORCED CONCRETE BEAMS with Varying Fire Loading Conditions

In this paper, a numerical study by three-dimensional modeling is done for reinforced concrete beam exposed to fire conditions with various boundary conditions. Both geometric and material properties are taken into account in this formulation because of the changes in material properties and the large variations experienced in fire. The three stages associated with the numerical procedure for evaluating fire resistance of RC beams, namely fire temperature calculation, thermal analysis, and strength analysis are modeled using a finite element (FE) model. The FE model is prepared in ABAQUS software to study the response of an RCC beam under fire during loading conditions. The RCC beams are analyzed for different end conditions and fire loading surfaces. Initially, it is kept at 25 °C. Then the uniform loading of one-third of the compressive strength of concrete is applied as a pressure loading in the beam (3D solid element). The other faces of RCC beam have temperature boundary conditions. The temperature boundary condition is governed by temperature–time curve as per ASTM E119. The moment–curvature (M–k) relationships are developed for the beam at few critical positions of the RCC beam for various end conditions as well as temperature boundary conditions. These M–k relationships may be used to carry out the strength analysis of the beam member and draw significant conclusions.
Ankit Borgohain, Sriman Kumar Bhattacharyya

Effect of Slab Thickness on Period of the Vibration of Reinforced Concrete Building

The fundamental time period of vibration of reinforced concrete (RC) moment resisting frame (MRF) buildings can be calculated using empirical expressions of Indian codes of seismic design to derive design base shear. Indian code IS1893 (Part-1)–2016 provides empirical expression to estimate the approximate natural time period of vibration which widely depend on some basic parameters such as a number of storeys or height of the building. The consideration of the effects of some other parameters of the structures also seems to be required. There is the scope of further improvisation in these equations. It can be observed that there is wide use of fundamental period obtained using these expressions. It is, therefore, in the seismic design of the structures, it is in favour of more accuracy in design to use realistic values of the time period. This study deals with the estimation of the fundamental period of vibration of symmetrical RC MRF buildings which incorporates the parameters like slab thickness, stiffness (referring to column sizes) of the structure in addition to its height. In the paper, different values of the time period have been obtained by performing dynamic analysis on building/structural configurations for different parameters of the building and earthquake zone III as per the provisions are given in the Indian seismic code. The results have been presented with comparative analysis. Computer software STAAD has been used to analyse the building model.
Prabhat Kumar Soni, S. K. Dubey, Prakash Sangamnerkar

Sampling-Based Techniques for Finite Element Model Updating in Bayesian Framework Using Commercial Software

Finite element (FE) model updating in Bayesian framework, using sampling-based techniques like Markov chain Monte carlo (MCMC), is observed to be investigated by many researchers. The present work is focussed on FE model updating using MCMC techniques where modelling is performed using commercial FE software to avoid the difficulties with writing computer program for FE modelling. In this present work, two prominent MCMC techniques based on Metropolis–Hastings (MH) algorithm, viz. enhanced-MCMC and transitional MCMC are primarily used, while FE modelling is performed using a well-known FE software, viz. SAP2000. A reasonably complex structure in the form of a cantilever plate is considered in this study and modelled using shell elements. Besides, damage is simulated in this plate structure by decreasing the Young’s modulus of few of the elements of the discretized plate structure. Modal data in the form of frequencies and incomplete mode shapes, evaluated from the damaged structure, are taken as the measured modal data. The technique of error localisation and an improved parameter selection method are adopted for limiting the number of updating parameters to facilitate better performance. Moreover, Gibbs sampling which is an effective algorithm of MCMC technique is also demonstrated using SAP2000. All the MCMC techniques for FE model updating are performed using a computational framework based on interactions between MATLAB and SAP2000 with the help of SAP2000 open application programming interface (OAPI). It is observed that level of performances in FE model updating is most satisfactory while using enhanced-MCMC in comparison with others.
Ayan Das, Nirmalendu Debnath

Stochastic Structural Optimization of Multiple Tuned Mass Damper (MTMD) System with Uncertain Bounded Parameters

This study deals with the optimization of parameters of multiple tuned mass damper (MTMD) system for seismic vibration control considering uncertain bounded structural parameters. An approach based on Taylor expansion of objective function along with subsequent interval extension is taken into account in this study. The objective function involving the uncertain bounded parameters is transformed into two independent deterministic sub-problems leading to the lower and upper bound solutions with the help of interval extension. The optimization strategy investigated in this optimization framework is the stochastic structural optimization (SSO) where the root mean square displacement of the primary–secondary coupled system is minimized. A numerical study is performed to observe the effect of uncertainties on the optimization of MTMD parameters where the primary system is coupled with MTMD system with two, three, five and ten mass units. The performance of these MTMD systems is also compared under various levels of uncertainties. Fundamental mode of the system is considered for vibration control, where natural frequency and damping ratio associated with the fundamental mode are found to be nearly 10 rad/s and 0.03, respectively. In this study, natural frequency and damping ratio of the primary system, natural frequency and damping ratio of elastic filter, intensity of the power spectral density of white noise excitation at the bed rock are taken as the uncertain parameters. It is observed that SSO is suitable for higher levels of uncertainties associated with structural parameters. It may be mentioned that such observations are found for various numbers of mass-units of MTMD system.
Kamalesh Bhowmik, Nirmalendu Debnath

Hearth Monitoring of Blast Furnace Using Finite Element Analysis and Artificial Intelligence

Hearth wear profile determines the life of a blast furnace, which is generally monitored by an inverse heat conduction analysis. Numerous thermocouples are embedded in the refractory lining and the temperature readings are used to access the wear profile of the hearth, which provides warnings about the infiltration of liquid iron through the refractory mass to the shell of the blast furnace. Because of the fatal nature of the consequences, accurate predictions about the profile of the inner refractory of the blast furnace are useful for initiating corrective action. This paper describes a method whereby the left out refractory lining profile is estimated as well as the thickness of the protective skull using finite element analysis and artificial intelligence. It serves as a guide to continue the operation of the furnace, to direct repair work to the critical areas, as well as to suggest the replacement of faulty sensors. In the effect, this method serves to increase the working life of blast furnaces.
Debi Prasad Ghosh, Bhaskar Sengupta, Shyam Krishna Maitra

Fatigue Resistance of Recycled Steel Fibers (Discarded Vehicle Tyre Steel Fibers) Concrete Pavement

Concrete pavements are exposed to repetitive (cyclic traffic) loads throughout its lifespan resulting in the instigation of cracks. Propagation of cracks implies to permanent damage of rigid pavement owing to fatigue damage. From inception, cause of the creation of cracks in the rigid pavement is less resistance of the rigid pavement against bending, tension, and cracking. Market available (Industrial) steel fibers are incorporated in plain concrete to enhance its post-cracking flexural behavior and fatigue performance. Even though industrially manufactured steel fibers help concrete pavements by restricting cracks, these are not preferred due to the higher cost of material. An alternative to using recycled steel fibers recovered from discarded vehicle tyres is a cheaper fiber solution with notable environmental benefits. Research work aligned to the adaptability of recycled steel fibers has been reported, but there is the lack of studies on exploring fatigue performance of recycled steel fibers reinforced concrete pavement with reference to IRC 58:2015 guidelines. Experimental findings recommend the use of ‘Hybrid fibers’ a mix of waste tyre steel fiber and industrial steel fiber in a definite proportion which enhances mechanical properties of concrete. Temperature study and fatigue analysis warranty the use of hybrid fibers in pavement construction as it provides cost-effective, environment-friendly solutions.
M. V. Mohod, K. N. Kadam
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