Shyh-Jiann Hwang

Response of Reinforced Concrete Buildings in Concepción during the Maule Earthquake

Detailed observations are reported for eight shear wall buildings from the Concepción region that experienced severe damage during the 27 February 2010 Chile earthquake. The repetitive nature of some of the damage suggests that these field observations may be applicable to similar buildings elsewhere, whereas other damage may be unique. Several shear walls experienced failures that apparently started at the boundaries due to the high compression in these unconfined edges, and propagated into the wall web. Other walls, including horizontal and vertical wall segments in perforated walls, experienced shear failure. Damage also was observed in columns, beams, and coupling slabs. In most cases, the percentage of damaged elements was less than 10% of the lateral force-resisting elements of the building, suggesting that these structures were not capable of distributing damage. Several building indices are calculated, including vibration periods and regularity indices, for comparison with observed behavior.

Seismic Response of a Concrete Frame with Weak Beam-Column Joints

A reduced-scale, planar, two-story by two-bay reinforced concrete frame with weak beam-column joints was subjected to earthquake simulations on a shaking table. The beam-column joints did not contain transverse reinforcement, as is typical in older construction designed without attention to detail for ductile response. A series of linear and nonlinear analytical models of the frame were developed in accordance with American Society of Civil Engineers standards and subjected to the input base motions. The goodness of fit between analytical and measured results depended on the details of the analytical model. Reasonably accurate reproduction of the measured response was obtained only by modeling the inelastic responses of both columns and beam-column joints. The results confirm the importance of modeling nonlinear joint behavior in older concrete buildings with deficient beam-column joints.

Shaking Table Tests on Reinforced Concrete Frames without Seismic Detailing

Four reinforced concrete frame specimens were tested on a shaking table with the objective to observe the interaction of structural elements at the onset of collapse. Each specimen consisted of a 1/2.25 scaled model of a two-bay, two-story reinforced concrete frame without seismic detailing. The specimens were tested under moderate and high column axial loads to investigate the influence of axial load on the collapse vulnerability of nonductile columns in a structure. These tests enable study of the interaction of the beams, columns, and joints as collapse is initiated. This paper presents the observations during the tests and comparison of response of the specimens. In particular, the test results suggest that collapse of a concrete frame due to failure of unconfined beam-column joints is less likely compared with collapse due to failure of nonductile columns.

Dynamic Collapse Simulation of 3-Bay RC Frame under Extreme Earthquake Loadings

Collapse experiments are found very helpful in facilitating collapse analysis of new buildings and identification of older buildings that are at high risk of structural collapse during severe earthquake events. Experimental observations from dynamic global collapse of a single story 3-bay RC frame are presented in this paper. The frame is composed of shear-critical columns and ductile columns to allow for load redistribution. A near-fault record from the September 21 (local time) 1999 Chi-Chi Taiwan earthquake was employed. Preliminary investigation shows that existing empirical equations are able to predict hysteretic backbone until the point of structural collapse with satisfaction.

Seismic Assessment on In-situ School Testing in Taiwan Using Methodology of ASCE/SEI 41-06

ASCE/SEI 41, the standard for seismic rehabilitation of existing buildings, proposes seismic evaluation procedures for concrete buildings. In-situ test results of existing school buildings in Taiwan can be used to verify the evaluation methodology in ASCE/SEI-41 Supplement 1. This paper reports on one in-situ specimens, 2-story 2-classroom building frames, subjected to reversed-cyclic and pseudo-dynamic loading. The experimental program, test setup and test results will be presented in this paper. The methodology for seismic assessment in ASCE/SEI-41 Supplement 1 will be applied to evaluate the seismic capacity of the existing school building, and the results of the evaluation and in-situ tests will be compared. A methodology proposed for the seismic assessment of concrete school buildings in Taiwan will also be discussed.