Back Issues 11-20

AN IMPORTANT FACTOR NEGLECTED IN THE SEISMIC REINFORCEMENT PERFORMANCE DESIGN OF SCHOOL BUILDINGS: SHEAR BANDING

Ching-Chang Lin, Tsai-Fu Chuang, Da-Jie Lin

Associate Professors, Feng-Chia University, Taiwan

Kuan-Tang Shen, Cheng-Chieh Ho, Chun-Yi Su

Directors, Institute of Mitigation for Earthquake Shear Banding Disasters, Taiwan.

Tse-Shan Hsu

President, Institute of Mitigation for Earthquake Shear Banding Disasters

Retired Professor, Feng-Chia University, Taiwan.

Abstract

The performance design goal of seismic reinforcement of school building structures is to ensure that they do not collapse in a severe earthquake, thus safeguarding teachers and students. However, in the design process and design content, only areas with ground vibration energy, which accounts for less than 10% of earthquake energy, are fortified, and areas with shear bands, where more than 90% of earthquake energy is involved, are not fortified. Therefore, the substantive significance of the results obtained from pushover analysis and a test method based on the results of the earthquake-resistant reinforcement plan for school building structures in Taiwan are explored. There are four main findings. (1) The proposed conditions for maintaining stability of school buildings during an earthquake are that the rigid stratum remains rigid, the horizontal stratum surface remains horizontal, and the continuous stratum surface remains continuous; and if the stable conditions cannot be maintained, the school buildings will collapse. (2) In traditional pushover tests and analysis, the conditions of the school building and the structural analysis model are consistent with the proposed conditions for maintaining the stability of the school building during an earthquake. Therefore, in the traditional pushover test and analysis, the results do not truly reflect what actually happens during an earthquake leading to the collapse of school buildings because the shear banding effect is ignored. (3) After the first edition of the seismic design code for buildings in Taiwan was promulgated in 1974, the ground vibration fortification level was continuously increased after successive earthquakes without certification. As a result, the cross-sectional area and the number of ribs of structural elements on the upper part of the buildings have unnecessarily increased. (4) Although the Ministry of Education of Taiwan has spent a considerable amount of money on earthquake-resistant reinforcement of school buildings, the reinforcement is limited to improving the fortification level against ground vibration, so that the buildings could still collapse due to shear banding in a future earthquake. Based on the above results, it is suggested that future revisions of the code be based on the actual need for separate protection to ensure the stability of school buildings in shear banding zones and non-shear banding zones. This is the best way to avoid excessive ground vibration fortification in non-shear banding zones and to avoid under-fortification against shear banding in shear banding zones.

Keywords: seismic reinforcement, performance design, school building, shear banding, ground vibration, pushover.

Attachments:

1222 Final.pdf

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816 kB