Effect of Lintel Beam on Seismic Response of Reinforced Concrete Buildings with Semi-Interlocked and Unreinforced Brick Masonry Infills

The primary focus of this study is to evaluate the nonlinear response of reinforced concrete (RC) frames with two types of brick infills viz., unreinforced brick masonry infill (URM) and semi-interlocked brick masonry infill (SIM) together with lintel beams, subjected to seismic loads. The seismic response is quantified in terms of response reduction factor and base shear. Infill walls are modeled using double strut nonlinear cyclic element. Nonlinear static adaptive pushover analysis is performed in the finite element program SeismoStruct. The response reduction factor (R) is computed from adaptive pushover analysis and performance for all models is obtained. The results showed that the average R factor of the RC framed structure with semi-interlocked masonry (SIM) is 1.31 times higher than the RC frame with unreinforced masonry (URM) infill. The R value of the bare frame with the lintel beam is found to be less than the corresponding value recommended in the Indian Standard Code. The results obtained in this study highlight that if the impacts of lintel beams and various brick infill scenarios are considered in the RC frames then the R values used for the design of RC frame buildings with infills would be underestimated (i.e., the evaluated R values are greater than the R values used for the design purpose).

Applying Adaptive Pushover Analysis to Estimate Incremental Dynamic Analysis Curve

To estimate seismic demand and capacity of structures, it has been suggested by researchers that Incremental Dynamic Analysis (IDA) is one of the most accurate methods. Although this method shows the most accurate response of the structure, some problems, such as difficulty in modeling, time-consuming analysis and selection of the earthquake records, encourage researchers to find some ways to estimate the dynamic response of structures by using static nonlinear analysis. The simplicity of pushover analysis in evaluating structural nonlinear response serves well as an alternative to the time-history analysis method. In this paper, based on the concepts of the displacement-based adaptive pushover (DAP), a new approach is proposed to estimate the IDA curves. The performance of the proposed method has been investigated using 3- and 9-story moment-resisting frames. In addition, the results were compared with exact IDA curves and IDA curves developed by the modal pushover analysis (MPA) based method. For evaluation, IDA curves with 16%, 50% and 84% fractile were estimated. Using the results, [Formula: see text] capacities corresponding to Collapse Prevention (CP) limit state were calculated and assessed. Finite element modeling of the structures has been carried out by using ZEUS-NL software. Based on the achieved results, the proposed approach can estimate the capacity of the structure accurately. The significant advantage of the applied approach is the low computational cost and desirable accuracy. The proposed approach can be used to develop the approximate IDA curves.

Seismic Performance Assessment, Retrofitting and Loss Estimation of an Existing Non-Engineered Building in Nepal

<p>The non-engineered building built before 2004 remained after Gorkha earthquake although such structures demonstrate seismic deficient. Therefore, the present study aims to carry out detail seismic performance of such building to investigate as-built seismic performance and its performance after intervention of retrofit measures. Two in situ tests were performed, which includes Schmidt hammer test and ambient vibration test. The adaptive pushover analysis and dynamic time history analyses were performed for as-built and retrofitted building. The retrofit measures increase the stiffness and maximum base shear capacity of the buildings. In addition, such retrofit measures improved single storey drift concentration in existing building such that uniform drift profile can be attained. Furthermore, the probability of exceeding damage states can be significantly reduced and mainly found to be more effective in minimizing higher damage states, such as partial collapse and collapse states. The maximum expected annual loss occurs between 0.1 g and 0.2 g PGA (Peak Ground Acceleration). It was revealed that the steel braced building was found to be relatively more effective in enhancing the seismic performance, whereas reinforced concrete shear wall found more economic feasible retrofit measure for this particular building.</p>

Adaptive Pushover Analysis of Irregular RC Moment Resisting Frames

Researchers and engineers certainly prefer to use nonlinear static methods over complicated nonlinear time-history methods. However, in nonlinear static procedure both predetermined target displacement and force distribution pattern are based on a false assumption that the structural behavior and its responses are dominated by the fundamental vibration modes. Therefore, over the past decades, there have been a great number of studies on considering higher mode contribution in nonlinear static results. The Displacement-based Adaptive Pushover Analysis (DAP) is one of the performance assessments tool for improving the accuracy of the obtained results of nonlinear static analysis in estimating the seismic demands of the structures. In this paper, 5 storey L- shaped RC frame is analyzed for seismic Zone IV and designed as per provisions of IS codes. Performance evaluation is carried out by nonlinear static analysis as well as adaptive pushover analysis and results are compared.

Single-Run Adaptive Pushover Procedure for Shear Wall Structures

This chapter proposes a new single-run adaptive pushover method for the seismic assessment of shear wall structures. This method offers two main advantages: it does not require decomposing the structure in nonlinear domain and it avoids the pitfall of previous single-run adaptive pushover analyses in utilizing the modal combination in the determination of the applied loads instead of combining the response quantities induced by those loads in individual modes. After a brief review of the main adaptive pushover procedures, the proposed method is presented as well as its numerical implementation. The predictions of this method are compared to those of other recent adaptive pushover methods and as well as to the rigorous non-linear time history analysis. Analyses show the efficiency of the proposed method.