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Modelling of tall shear walls for nonlinear analysis of RC buildings under cyclic lateral loading
Abstract
The shear walls constitute the primary lateral load resisting system in a reinforced concrete building with such walls. Hence, a wall needs to be modelled adequately in an analysis of the building for seismic loads. In this paper, a typical reinforced concrete multi-storeyed building with a centrally located tall shear wall was investigated for three approaches of modelling the nonlinear flexural behaviour of the wall. First, the wall was modelled using column elements with lumped plasticity at the ends (Model 1). Model 2 was developed using layered shell elements for the wall. Finally, fibre-based wall elements based on spread plasticity, was adopted to model the wall (Model 3). Cyclic pushover analysis, non-linear time-history analysis and incremental dynamic analysis were performed using the models. It was observed that for the cyclic pushover analysis, the fibre-based approach of modelling the wall gave better estimate of the hysteresis behaviour, as compared to the model based on column elements. For the non-linear time-history analysis, the higher frequency components in the variations of the moment and rotation at the base of the wall were captured only in the fibre-based approach. However, the results from the incremental dynamic analysis were comparable for the three models.
... Because of the consequent excitations of an earthquake or lateral imposed loads on a structure, the stiffness of some elements of structure reduced and the structure started to fail and lose its performance; although failure happened either in small parts of structure or at the whole. In this study thirteen reinforced concrete (RC) frame buildings with 2, 3,4,5,6,7,8,9,10,11,12,16 and 20 stories, having 3 and 4 bays were designed using seismic force levels obtained from the Iranian Seismic Code 2005 and proportioned using the ACI 318-99 building code and then were modeled by IDARC. Pushover analysis with increasing triangular loading was used. ...
Earthquake, a natural fury cannot be ignored as far as the stability of a structure is concerned. All structures should be made seismic resistant to prevent loss of life and infrastructural damage. The Pushover Analysis is conducted to find out the seismic response of the structure In performance based seismic analysis evaluates how building is likely to perform. It is an iterative process with selection of performance objective followed by development of preliminary design, an assessment whether or not the design meets the performance objective; In the present study pushover analysis has been done an two multistoried R.C. frame building; In which plan of 2 buildings was taken symmetrical 10 storey and it consist of 5 bays in x direction & 5 bays in y direction and second building having 15 storey. The shear wall is providing for studying their resisting lateral forces. The building has an overall plan dimension of 20m x 20m.The M25 grade of concrete and Fe 415 grade of steel is considered for design. In this highlight the effect of shear wall on R.C frame building when shear wall providing along the longer and shorter side of the building Pushover analysis is carried out using commercially available software ETABS and behaviour of RC frames is studied.
Constitutive formulations are presented for concrete subjected to reversed cyclic loading consistent with a compression field approach. The proposed models are intended to provide substan- tial compatibility to nonlinear finite element analysis in the context of smeared rotating cracks in both the compression and tension stress regimes. The formulations are also easily adaptable to a fixed crack approach or an algorithm based on fixed principal stress directions. Features of the modeling include: nonlinear unloading using a Ramberg-Osgood formulation; linear reloading that incorporates degradation in the reloading stiffness based on the amount of strain recovered during the unloading phase; and improved plastic offset formulations. Backbone curves from which unloading paths originate and on which reloading paths terminate are represented by the monotonic response curves and account for compression softening and tension stiffening in the compression and tension regions, respectively. Also presented are formulations for partial unloading and partial reloading.
While currently existing modelling approaches of reinforced concrete (RC) behaviour allow a reasonably accurate prediction of flexural response, the determination of its shear counterpart needs further developments. There are various modelling strategies in the literature able to predict the shear response and the shear–flexure coupling under monotonic loading conditions. However, very few are the reported models that have demonstrated successful results under cyclic loading, as in the seismic load case. These considerations lead to this research work focused on the development of a flexure–shear model for RC beam–column elements. A reliable constitutive model for cracked RC subjected to cyclic loading was implemented as bi-axial fibre constitutive model into a two-dimensional Timoshenko beam–column element. Aim of this research work is to arrive at the definition of a numerical model sufficiently accurate and, at the same time, computationally efficient, which will enable implementation within a finite element package for nonlinear dynamic analysis of existing non-seismically designed RC structures that are prone to shear-induced damage and collapse. Copyright © 2009 John Wiley & Sons, Ltd.
Well designed and detailed reinforced concrete shear walls in a building can provide the required lateral stiffness and strength, as well as ductility, for resisting seismic loads. A pushover analysis is preferred to an equivalent static analysis to estimate the non-linear behaviour of a building under seismic loads. The present study investigated the different options for modelling a tall and solid shear wall in a pushover analysis of a regular multi-storeyed building. Two approaches were adopted for modelling the non-linear behaviour of a shear wall. The first one was based on lumped (point) plasticity, where the shear wall was modelled using column elements (Model 1). The second one was based on spread (distributed) plasticity, where the wall was modelled using fibre-based wall elements (Model 2). The analyses of Models 1 and 2 were compared based on the pushover curves, demand and capacity spectra plots, and formation of hinges. The observed non-linear behaviours of the two models were very similar. It is concluded that the modelling of a tall and solid shear wall using column elements is adequate for pushover analysis, provided the hinge properties are defined properly.
In order to utilize results obtained from quasi-static cyclic load tests on structural components for a general performance evaluation, the need exists to establish loading histories that capture critical issues of component capacity as well as seismic demands. In inelastic seismic problems capacity and demands cannot be separated since one may strongly depend on the other. Because of cumulative damage issues the capacity depends on the number of inelastic excursions and the magnitude of each excursion (not just the largest one). These two parameters depend on the frequency content of the ground motion, the period(s) of the structure, and the strength and inelastic deformation characteristics of the structure. The paper presents procedures how these characteristics can be considered in the selection of suitable loading histories.