考虑失效准则和沉降控制条件的基桩可靠度分析

Reliability Analysis of Foundation Piles Considering Different Failure Criteria and Settlement Control Requirements

研究了失效准则和沉降控制条件对基桩可靠度分析结果的影响.以s-lgt失效准则为基准,定义了搜集到的7种失效准则的偏差系数,并结合承载能力极限状态和正常使用极限状态模型因子给出了考虑失效准则、模型不确定性和沉降控制条件等因素的可靠度综合分析方法.最后,研究了桩顶容许沉降随机性对可靠度分析结果的影响.研究表明:沉降控制条件的变化对可靠度指标影响较大,但不改变由7种失效准则计算的可靠度指标排列次序.可靠度指标随容许沉降的增大而增大,但增长幅度逐渐降低,该结果不受失效准则影响.基桩承载能力极限状态与正常使用极限状态的可靠性评价机理之间存在关联性.因此,建议将失效准则和沉降控制条件结合起来综合评价基桩的可靠性.

The effect of different failure criteria and settlement control requirements on the reliability a-nalysis of foundation piles was studied.The bias factor defined with respect to the s-lgt failure criterion was introduced to each of the seven failure criteria collected.The synthetic reliability analysis method with consideration of different failure criteria,model uncertainties and settlement control requirements was presented by using model factors for ultimate limit state （ULS）and serviceability limit state （SLS）.Final-ly,the impact of the randomness of limiting tolerable settlement of pile head on reliability analysis was studied.The following conclusions are drawn.First,variation of settlement control requirements has a great influence on reliability index while does not create a change of the ranking of reliability levels based on seven failure criteria.Second,reliability index increases with the limiting tolerable settlement although the increase rate gradually diminishes,which is independent of failure criterion.Third,there is a close cor-relation between the evaluation principles of foundation pile reliability for ULS and SLS.Therefore,this study recommends the combination of failure criteria and settlement control requirements for the compre-hensive assessment of foundation pile reliability.