懸臂式擋土牆受震穩定性之可靠度分析

Seismic Reliability Analysis for the Stability of Cantilever Retaining Wall

黃富國(Fu-Kuo Huang) ； 王淑娟(Grace S. Wang)

《中國土木水利工程學刊》 21卷4期 (2009/12) Pp. 365-381

https://doi.org/10.6652/JoCICHE.200912_21(4).0001

摘要

本文旨在探討懸臂式擋土牆受震穩定性之可靠度，研究中採用擬靜態（pseudo-static）分析法考慮地震引致之動態土壓力，並利用蒙地卡羅模擬（Monte-Carlo simulation, MCS）評估牆體受震穩定性之可靠度。所考慮之因素，除包括一般靜態條件下各分析參數之變異性與不確定性，亦納入台灣地區之地震特性，採用與地震危害度諧和（hazard consistent）之震力參數來進行可靠度分析。其成果係以牆體危險係數（安全係數的倒數）之年超越機率曲線，以及破壞機率與擋土牆設計服務年限之關係來呈現，不但呼應「性能地震工程」（performance-based earthquake engineering，簡稱PBEE）之發展趨勢，也提供了與其他工程結構受震之破壞機率一個共同的比較基準，可作為擬定震害防治決策之參考。另外，從本研究案例探討之分析結果顯示，擋土牆之基礎支承力安全係數（FS（下標 b））對分析參數之變異性及不定性相當敏感，將其納入分析考慮後，FS（下標 b）降低幅度相當明顯，亦可能成為設計控制因素。在進行牆體受震穩定性之可靠度分析時，須謹慎評估其影響。

關鍵字

擬靜態分析 ； 蒙地卡羅模擬 ； 可靠度 ； 性能地震工程

並列摘要

In this study, the seismic reliability for the stability of cantilever retaining wall is explored, where the dynamic earth pressure due to earthquake is analyzed by the pseudo-static method, and the seismic reliability of the stability of wall is evaluated by the Monte Carlo simulations. The effects of variability and uncertainty of evaluation parameters are all included in the analysis model accompanied by the hazard-consistent ground motion parameters of Taiwan area. The reliability for the stability of the wall is expressed by the annual probability of exceedance for the factor of danger of the wall, and the failure probability versus the exposure time of the wall, which meet the objective of the performance-based earthquake engineering (PBEE). The results thus obtained give the risk-based failure potential of wall which is consistent with the seismic hazard of the site, and constitute a common standard for comparing annual probability of failure modes among different structures. The decision of countermeasures against failure of wall is also easy to make by the methods established here. From this research, it is also shown that the factor of safety against bearing capacity failure (FS(subscript b)) of the wall is very sensitive to the uncertainties of the parameters in analysis model. It will result in a greatly decreased extent of FS(subscript b), which may also become a critical factor governing the design, if the uncertainties are included in the analysis. Therefore, it is recommended that more attention should be paid to this issue for analyzing the seismic reliability of the stability of retaining wall.

並列關鍵字

pseudo-static analysis ； Monte-Carlo simulation ； reliability ； performance-based earthquake engineering