Modeling of Nonlinear Cyclic Load Behavior of I- Shaped Composite Steel-concrete Shear Walls of Nuclear Power Plants

Traditionally, reinforced concrete (RC) walls have long been adopted as an efficient lateral load resisting systems to enhance the stability and integrity of the buildings against dynamic actions such as wind, earthquakes etc. Later, steel plate walls were proposed as a promising alternative of concrete walls. Thin steel plate walls contributed in weight reduction of the structure with greater stiffness, higher ductility and enabled rapid constructions. Composite construction was then used for the structures requiring higher order of safety and reliability. RC shear walls with flanged cross sections have been theoretically, numerically and experimentally studied in the nuclear power plants. Asfur and Bruin [1] compared the analytical studies with the results of the test conducted by Nuclear Power Engineering Corporation (NUPEC) [2] to investigate the dynamic characteristics of RC shear walls. Mo and Chan [3] presented a softened concrete stress-strain relationship for the prediction of overall strength behavior of lowrise reinforced-concreteframed shear walls with flanged geometry under static loads. The softening parameters were found to be one of the main reasons in overestimating the ultimate strength values for high-strength concrete. Yoshio et al. [4] developed analytical methodology to predict the behavior of RC shear wall structures from elastic to collapse load with multi-axes seismic loading schemes using FEM technology. The methodology was proved significant for evaluating the strength margins of important structures in a nuclear power plant. Singh and Kushwah [5] determined the ultimate load capacity of reinforced concrete shear walls under static and dynamic loads using a three dimensional finite element. These wall units were considered to be used as safety class structures in nuclear power plants. The model was utilized to analyze a shear wall tested by NUPEC and the results have shown nice agreement [2]. A number of studies have been reported on the behavior of steel-concrete composite shear walls. Tong et al. [6] experimentally studied the cyclic response of a composite structural system consisting of partially restrained steel frames with reinforced concrete infill walls. The gravity loads and overturning moments were assumed to be resisted by steel components whereas shear was resisted In recent years steel-concrete composite shear walls have been widely used in enormous high-rise buildings. Due to high strength and ductility, enhanced stiffness, stable cycle characteristics and large energy absorption, such walls can be adopted in the auxiliary building; surrounding the reactor containment structure of nuclear power plants to resist lateral forces induced by heavy winds and severe earthquakes. This paper demonstrates a set of nonlinear numerical studies on I-shaped composite steel-concrete shear walls of the nuclear power plants subjected to reverse cyclic loading. A three-dimensional finite element model is developed using ABAQUS by emphasizing on constitutive material modeling and element type to represent the real physical behavior of complex shear wall structures. The analysis escalates with parametric variation in steel thickness sandwiching the stipulated amount of concrete panels. Modeling details of structural components, contact conditions between steel and concrete, associated boundary conditions and constitutive relationships for the cyclic loading are explained. Later, the load versus displacement curves, peak load and ultimate strength values, hysteretic characteristics and deflection profiles are verified with experimental data. The convergence of the numerical outcomes has been discussed to conclude the remarks.