Evaluation of Ultimate Seismic Capacity of Existing Seismically Eccentric RC Buildings By Ambient Vibration Measurement

Abstract eng:
Story collapses of many RC buildings due to torsional response which were induced mainly by seismic eccentricity of buildings, were reported in the 1995 Kobe earthquake. Therefore, it is important to grasp the torsional response properties for evaluating ultimate seismic capacity of existing RC building. The modulus of eccentricity has been introduced in the Japanese current seismic design standards, which reflects spatial non-uniformity of mass and horizontal rigidity of seismic resistant elements such as columns and seismic walls. However, the modulus does not directly relate to the torsional response which depends on building vibrational behavior and input motions. Moreover, since the vibration behavior of existing buildings varies in time, in order to capture the vibrational behavior of existing buildings appropriately, the design conditions and original drawings are not sufficient to reflect the actual condition of the buildings which had experienced some damage from past earthquakes. In this paper, the torsional response properties, both the natural periods and the center of rotation of a target RC building which has strong motion accelerometers are identified using the Subspace State Space System IDentification (4SID) with an ambient vibration record and strong motion records, where the former can reflect the current condition of the building and the latter can reflect temporal change of building conditions due to past seismic reinforcements and past experience from earthquakes. The 4SID is one of the methods which can identify parameters of a system composed of Multi-Input and MultiOutput (MIMO) in time domain. With the parameters of the method chosen correctly, it is indicated that the torsional response properties with ambient vibration records and with strong motion records agree well with each other in reasonable range. In other words, it would be possible to evaluate seismic capacity of existing eccentric RC building by ambient vibration measurement. Moreover, the long-term change of the center of rotation on the target RC building is discussed. Lastly, for the purpose of evaluating ultimate seismic capacity, the ultimate behavior of the center of rotation is investigated by an elastoplastic seismic response analysis of a single-story model with biaxially seismic eccentricity. Finally, this paper proposes evaluation procedure for ultimate seismic capacity of existing eccentric RC building by ambient vibration measurement and the system identification techniques.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket