Abstract: SUMMARY Smart materials such as shape memory alloys (SMAs) are recently being used in earthquake engineering applications to control the response of structures. In this paper, a shape-memory alloy damper device made up of austenite wires (e.g. Nickel Titanium wires) is used as a passive energy absorber. NiTi wires are very attractive for passive vibration control as they have a pseudo-elastic property and can sustain large amounts (upto 10% strain) of inelastic deformation. Moreover, in contrast to regular metallic materials they can recover that deformation. The damper device is designed, fabricated and tested. Validity study is made using a thermo-mechanical model of SMA taking into account the residual martensite accumulation irreversibly due to cyclic forward/reverse martensitic transformation. Further an analytical study of a supporting steel structure of dump tanks with and without SMA dampers subjected to design wave earthquake loading is carried out. Performance of the structure with SMA dampers is compared with that of the same structure with yielding dampers. Copyright © 2010 John Wiley & Sons, Ltd.

Abstract: Nano technology is an emerging field of interest for civil engineering application. Among the nano materials presently used in concrete, nano-silica possess more pozzolanic nature. It has the capability to react with the free lime during the cement hydration and forms additional C-S-H gel giving strength, impermeability and durability to concrete. Present paper investigates the eects of addition of nano silica in normal strength concrete. Three types of nano-silica in the form of nano suspension having dierent amount of silica content have been investigated. Mix design has been carried out by using particle packing method. X-Ray diraction (XRD) analysis has been carried out to find the chemical composition of control concrete and nano modified concrete. Further, experimental investigations have been carried out to characterize the mechanical behaviour in compression, tension and flexure. It has been observed that the addition of nano-silica in normal strength concrete increased the compressive strength and decreased the spilt tensile strength and flexural strength. Also, Rapid chloride permeability test (RCPT) has been conducted to know the chloride permeability of control concrete, nano modified concrete, and nano coated concrete. It has been observed that the chloride permeability is less for nano coated concrete.

Abstract: Assessing the capacity of existing building as per the present codes of practice is an important task in performance-based evaluation. In order to enhance the performance of existing buildings to the present level of ductile design prescribed by present codes and find the retrofit or design a rehabilitation system, there is an urgent need to assess accurately the actual lateral load resistance and the potential failure modes. In this paper, a typical 6-storey reinforced concrete (RC) building frame is designed for four design cases as per the provisions in three revisions of IS: 1893 and IS: 456 and it is analysed using user-defined (UD) nonlinear hinge properties or default-hinge (DF) properties, given in SAP 2000 based on the FEMA-356 and ATC-40 guidelines. An analytical procedure is developed to evaluate the yield, plastic and ultimate rotation capacities of RC elements of the framed buildings and these details are used to define user-defined inelastic effect of hinge for columns as P-M-M and for beams as M3 curves. A simplified three parameter model is used to find the stress–strain curves of RC elements beyond the post yield region of confined concrete. Building performance of structural components in terms of target building performance levels are studied with the nonlinear static analysis. The possible differences in the results of pushover analysis due to default- and user-defined nonlinear component properties at different performance levels of the building are studied.

Abstract: Normal 0 MicrosoftInternetExplorer4 According to existing provisions, large separation distance has to be maintained between two conventional explosive storage structures to prevent sympathetic detonation. In this paper, reduction of the separation distance with the use of earth covered laced reinforced concrete (LRC) storage structure is demonstrated, which will result in saving of land cost. Details of blast resistant design of 75T (NEC) storage structure based on unit risk principle are presented. Performance of the storage structure is evaluated in an actual blast trial. Strain and deflection profiles are obtained from the trial. Based on these, the storage structure is found to be re-usable after the blast trial. Defence Science Journal, 2012, 62(5), pp.284-289 , DOI:http://dx.doi.org/10.14429/dsj.62.820

Abstract: To evaluate the strength hierarchy, three different types of exterior beam-column joint, i.e., gravity load designed, non ductile and ductile, following two different codes are considered. Strength of different components of beam-column joint, i.e., column, beam, and joint core, is individually calculated from different failure criteria. Shear strength of the joint is evaluated from softened strut and tie model. Strength hierarchy, ultimate strength, and critical failure modes of the specimens are analytically estimated and found to be well corroborated with the experimental results. The study will help in designing the earthquake resistant RC structures in a more rational way.

Abstract: This paper presents the methodologies for damage tolerant evaluation of stiffened panels under fatigue loading. The two major objectives of damage tolerant evaluation, namely, the remaining life prediction and residual strength evaluation of stiffened panels have been discussed. Concentric and eccentric stiffeners have been considered. Stress intensity factor for a stiffened panel has been computed by using parametric equations of numerically integrated modified virtual crack closure integral technique. Various methodologies for residual strength evaluation, namely, plastic collapse condition, fracture toughness criterion and remaining life approach have been described. Effect of various stiffener sizes and stiffener type (concentric and eccentric stiffeners) on remaining life and residual strength has been studied under constant amplitude load. From the studies, it has been observed that the predicted life is significantly higher with concentric and eccentric stiffener cases compared to the respective unstiffened cases. The percentage increase in life is relatively more in the case of concentric stiffener compared to that of eccentric stiffener case for the same stiffener size and moment of inertia. From the studies, it has also been observed that the predicted residual strength using remaining life approach is lower compared to other methods, namely, plastic collapse condition and fracture toughness criterion and hence remaining life approach will govern the design. It is noted that residual strength increases with the increase of stiffener size.

Abstract: Purpose – The purpose of this paper is to present integrated methodologies based on multilevel modelling concepts for finite element analysis (FEA) of reinforced concrete (RC) shell structures, with specific reference to account for the nonlinear behaviour of cracked concrete and the other associated features.Design/methodology/approach – Geometric representation of the shell is enabled through multiple concrete layers. Composite characteristic of concrete is accounted by assigning different material properties to the layers. Steel reinforcement is smeared into selected concrete layers according to its position in the RC shell. The integrated model concurrently accounts for nonlinear effects due to tensile cracking, bond slip and nonlinear stress‐strain relation of concrete in compression. Smeared crack model having crack rotation capability is used to include the influence of tensile cracking of concrete. Propagation and change in direction of crack along thickness of shell with increase in load and defo...

Abstract: This paper presents methodologies for residual strength evaluation of concrete structural components using linear elastic and nonlinear fracture mechanics principles. The effect of cohesive forces due to aggregate bridging has been represented mathematically by employing tension softening models. Various tension softening models such as linear, bilinear, trilinear, exponential and power curve have been described with appropriate expressions. These models have been validated by predicting the remaining life of concrete structural components and comparing with the corresponding experimental values available in the literature. It is observed that the predicted remaining life by using power model and modified bi-linear model is in good agreement with the corresponding experimental values. Residual strength has also been predicted using these tension softening models and observed that the predicted residual strength is in good agreement with the corresponding analytical values in the literature. In general, it is observed that the variation of predicted residual moment with the chosen tension softening model follows the similar trend as in the case of remaining life. Linear model predicts large residual moments followed by trilinear, bilinear and power models.

Abstract: This article proposes a simple isotropic damage model within damage mechanics framework to represent the behavior of concrete in tension. Macroscopic evolution of tensile crack is considered as dam...

Abstract: From the analysis of experimentally observed variations in surface strains with loading in reinforced concrete beams, it is noted that there is a need to consider the evolution of strains (with loading) as a stochastic process. Use of Markov Chains for modeling stochastic evolution of strains with loading in reinforced concrete flexural beams is studied in this paper. A simple, yet practically useful, bi-level homogeneous Gaussian Markov Chain (BLHGMC) model is proposed for determining the state of strain in reinforced concrete beams. The BLHGMC model will be useful for predicting behavior/response of reinforced concrete beams leading to more rational design.

Abstract: A simple technique is proposed to compute interface slip of stud connected steel-concrete composite (SCC) girders based on the results of a flexure test. The technique makes use of relative longitudinal displacement of the concrete slab and steel beam to calculate the interface slip. In the flexure test of a SCC girder, a cost-effective instrumentation arrangement consisting of mechanical dial gauges is used to measure the relative longitudinal displacement. Responses measured from experiments on SCC girders conducted by the authors are used for numerical implementation and validation of the technique. Alternatively, interface slip is also evaluated by applying an analytical model which is based on first principles of mechanics. The values of interface slip computed by using the proposed technique are found to have close correlation with those of the analytical model. The effect of edge restraint on slip due to friction between steel and concrete is also studied.

Abstract: Need for developing efficient non-destructive damage assessment procedures for civil engineering structures is growing rapidly towards structural health assessment and management of existing structures. Damage assessment of structures by monitoring changes in the dynamic properties or response of the structure has received considerable attention in recent years. In the present study, damage assessment studies have been carried out on a reinforced concrete beam by evaluating the changes in vibration characteristics with the changes in damage levels. Structural damage is introduced by static load applied through a hydraulic jack. After each stage of damage, vibration testing is performed and system parameters were evaluated from the measured acceleration and displacement responses. Reduction in fundamental frequencies in first three modes is observed for different levels of damage. It is found that a consistent decrease in fundamental frequency with increase in damage magnitude is noted. The beam is numerically simulated and found that the vibration characteristics obtained from the measured data are in close agreement with the numerical data.

Abstract: Abstract This paper presents the results of experimental investigations on six reinforced concrete beams, with three different shear span-to-depth ratios, which were tested under two-point loading. The aim of the work was to study the efficacy of Carbon Fibre Reinforced Polymer (CFRP) strips in enhancing shear capacity and/or changing the failure mode from brittle shear failure to ductile flexural failure. The results of the study indicate that while there is a marginal increase in first crack and ultimate loads, it is possible to achieve a change in the failure mode, and the monitored strain gauge data can be used to explain the failure pattern observed.