In this study, an innovative composite shear wall, comprised of boundary Concrete Filled Steel Tubular (CFST) columns, and Reinforced Concrete (RC) walls embedded with multiple steel plates has been developed. Seven specimens were investigated by cyclic loading tests. The parameters were the type of the boundary CFST columns, the number of multiple steel plates and the axial force ratio. There were two loading stages for the tests. During stage 1, the specimens were tested until a 2.0% drift ratio was attained. After stage 1, damaged specimens were retrofitted and tested in stage 2. The failure characteristics, hysteretic behavior, strength and deformation, strains, energy dissipation capacity and stiffness were studied. The results show that the hysteresis curves of the innovative shear walls were stable. The embedded multiple steel plates had a considerable effect on the seismic behavior of the innovative shear walls, and the strength increased with increasing number of steel plates. There was no considerable difference in the effect on seismic behavior for the different types of the boundary CFST columns. The developed shear walls, after retrofitting, were shown to satisfy seismic requirements. Finally, an evaluation method for the ultimate strength of the shear walls was developed with adequate accuracy.

Introduction

Reinforced concrete (RC) shear walls are commonly used in highrise buildings as they are important components for resisting earthquakes [1,2]. However, in most cases, the axial force ratio of the shear walls is limited according to the seismic design codes of different countries [3–۵]. In high-rise buildings, the axial force in the low stories is usually very large. As a result, the wall needs to be designed with dense reinforcing bars and thick sections. The consequences are that it will be more difficult to layout the reinforcing bars, and it also amplifies the earthquake action due to the increase in weight of the structure. Furthermore, increasing the wall thickness reduces the available area. Hence, in high-rise buildings, the design and construction of RC shear walls is very difficult. Sometimes, it is even impossible. To overcome the RC shear walls’ problems mentioned above, Steel Plates Embedded Reinforced Concrete (SPE-RC) shear walls have been developed in recent years [6], and the design provisions are specified in the Chinese code [7]. Fig. 1(a) shows the schematic view of a traditional SPE-RC shear wall. Usually, for an SPE-RC shear wall, the main components are the embedded single full-size steel plate, RC wall and boundary CFST columns [8–۱۱]. However, traditional SPE-RC shear walls have the following disadvantages: (1) The embedded single steel plate is continuous and the size of the entire wall, as such, it is difficult to hoist, to place into its desired location, and to weld. (2) As the embedded single steel plate separates the concrete into two parts, when the shear wall is under a large axial force, the concrete wall may be split into two. In order to prevent the wall from splitting and to improve integration, shear studs or bolts are welded on both sides of the steel plate. However, the cost of welding the shear studs is high and the construction is difficult. In this study, an innovative shear wall with boundary CFST columns and embedded multiple steel plates has been developed based on the traditional SPE-RC shear wall. Fig. 1(b) shows the schematic view of the innovative composite shear wall. As shown, instead of the single fullsize steel plate in the traditional SPE-RC shear wall, multiple steel plates are embedded inside the walls. As compared to a single steel plate, the merits of the multiple steel plates are as follows: (1) Less steel required. (2) As the multiple steel plates are smaller and lighter than the single full-size steel plate, they are easier to hoist, to place into the desired locations and to weld, leading to an easier construction. (3) The integrity of the concrete wall is improved because concrete on the two sides is connected through the gaps between the multiple steel plates. (4) The construction work is simplified because there is no need for welding shear studs or bolts to the steel plate.