INFLUENCE OF ANCHORAGE DETAILING ON SEISMIC BEHAVIOR OF PRECAST CONCRETE WALLS REINFORCED WITH SBPDN REBARS

1.INTRODUCTION Earthquake is one of the most devastating natural hazards that cause great loss of human life and property. An average of 10,000 people is killed by earthquakes each year, while annual economic losses are in the billions of dollars and often constitute a large percentage of the GDP of the affected country [1]. In earthquake-prone regions such as Japan and China, ductile reinforced concrete (RC) structures have been adopted as the favorite seismic resistance solution in the last decades [2, 3]. However, the earthquake engineering community has recently begun to reassess the seismic design procedures, in the wake of several devastating earthquakes such as the Hyogo-ken Nanbu earthquake (17 January, 1995; $150 billion loss and 6,000 deaths), the Wenchuan earthquake (12 May, 2008; $150 billion loss and 69,000 deaths), and the Gorkha earthquake (25 April, 2015; $20 billion loss and 9,000 death) [4-6]. From these major earthquakes, structural engineering community has learnt that though most of ductile concrete buildings did not collapse during major earthquake, many of them might be left unrepairable due to the large residual deformation caused by stronger earthquakes than the code-prescribed level. RC shear walls have been recognized as cost-effective way of providing lateral force resistance to buildings in seismic areas around the world. On the other hand, as observed by Wood et al [7], ductile RC shear walls tend to experience large drift under design level earthquakes in order to absorb the input earthquake energy, which leads to significant residual drift and damage tends to accumulate at the wall base plastic hinge region after the earthquake. Furthermore, structural components with large residual drifts were difficult to be repaired after earthquakes, which inevitably leads to high reconstruction cost and business downtime [8]. Therefore, from the viewpoint of reducing the cost of recovery and reconstruction, and making sure that the buildings and infrastructures still maintain sufficient resistance to intense aftershocks after a major earthquake, a new solution is urgently necessary. One of the authors and his colleagues have proposed an alternative solution, referred to as drift-hardening structures [9, 10]. The core point of the drift-hardening concrete components lies in the utilization of weakly bonded high-strength SBPDN rebars as the primary tensile reinforcement of concrete columns and walls instead of soundly bonded deformed rebars. As shown in Fig. 1, the drift-hardening components have two advantages over the conventional ductile components: (1) drift hardening capability and (2) significantly reduced residual deformation. The former implies stable response without degradation in lateral resistance up to large drift, while the latter means high reparability and low repairing cost. After verifying effectiveness of the use of SBPDN rebars in enhancing drift-hardening capability of concrete columns [9-11], Sun et al have applied the SBPDN rebars to concrete walls with rectangular section in the light of the revision of AIJ Standard for RC Buildings [12], which permits the use of rectangular shear walls without boundary columns.