Residual seismic capacity of ductile RC frame with wing walls based on full-scale loading test

Abstract

In order to use a damaged building continuously after earthquake, owners and/or stakeholders need to understand residual seismic capacity of the building. In Japan, a method to evaluate residual seismic capacity for damaged buildings had been developed. In order to evaluate residual seismic capacity of damaged building, the damage level of structural elements should be evaluated properly. This paper presents the results of damage analysis based on experimental data obtained from a full-scale static loading test [1] on a five-story reinforced concrete building tested at Building Research Institute. The damage rating for the specimens evaluated by the residual seismic capacity concept [3] was ”Moderate” or ”Heavy” at 0.5% and 1% building drift angle despite the structure maintaining horizontal load carrying capacity. This implies that the applied method gives a conservative result for ductile buildings, such as relatively new moment resisting frames designed after 1981. In order to apply the method used in this paper to new buildings, the damage evaluation method for structural elements should be advanced more in the future. INTRODUCTION When severe earthquake occurs, some buildings have several damages and the original seismic performance deteriorates. After earthquake, owners and/or users need to understand damage level of their damaged buildings to determine whether they can continuously use the building. In Japan, an existing standard describes a method to evaluate damage level of RC buildings using residual seismic capacity ratio which is defined as the ratio of the seismic capacity of the damaged building under earthquake to the original seismic capacity [1]. The evaluation method was developed based on the residual seismic capacity obtained from the damage data of actual damaged buildings due to past severe earthquake. However, investigations on residual seismic capacity of full-scale ductile RC frame specimens have never been carried out. This paper shows the results from damage rating of an entire building structure evaluated by the residual seismic capacity concept based on the standard in Japan and the validity of the method is discussed. LOADING TEST A static loading test on a full-scale reinforced concrete building was carried out as described in the past paper [2]. The specimen is a full-scale five story reinforced concrete building with 2 bays in the loading direction and one bay in the transverse direction, and was constructed in a laboratory of Building Research Institute at Tsukuba. The elevation of the specimen is shown in Fig.1. The story height is 3.5 m and the total height of the specimen is 17.5 m (Fig.1). The span length is 6.0 m in both directions. There are two types of openings (2.0m×1.8m and 1.0m×1.8m) symmetrically positioned on the walls along the loading direction. There are structural gaps provided at the end of the openings as shown in Fig.2 (a). The vertical walls between openings are completely separated from the main frame by those gaps. Figure 1: Panoramic view of the 5 story specimen. The beam cross-section is 500×700 mm with eight D25 bars (2 to 4 floor), or six D25 bars (5 and top floor) as longitudinal reinforcement shown in Fig.3. Stirrups are D13 at 100 mm or 150mm spacing. All slab thickness is 200 mm, the top and bottom of the slab reinforcement are D10 bars at 150 mm spacing, but D13 is arranged alternatively with D10 bars for the top reinforcement in the transverse loading direction. The lap splice of the reinforcement is provided in the middle of the span, and the end of the top reinforcement is anchored to the transverse beams with 90-degree hooks. The anchorage length of the bottom reinforcement is 250 mm from the side surface of the transverse beam.