中文摘要：

考虑承载力计算模型和荷载不确定性,利用可靠度分析方法和概率统计理论,推导出承载能力极限状态（ULS）和正常使用极限状态（SLS）下可靠度指标的计算公式,给出了两种极限状态下可靠度指标间的线性关系式,研究了桩顶容许沉降lts随机性对正常使用极限状态可靠度分析结果的影响。研究结果表明,土体类别和桩型对正常使用极限状态模型因子影响很小;正常使用极限状态下基桩可靠度指标随承载力计算模型和荷载不确定性的增大而减小,但减小幅度逐渐降低,且可靠度指标总变化量不大,工程应用中可忽略承载力计算模型和荷载不确定性在可靠度分析中的影响;lts随机性对正常使用极限状态可靠性分析结果的影响很大,随lts的增加,正常使用极限状态模型因子和可靠度指标逐渐增大,而模型因子变异性逐渐减小,但桩本身性质并没有任何改变,只是所允许的沉降条件不同。研究结果可为规范修订和工程应用提供参考。

英文摘要：

Taking into account the uncertainties of the calculation model of bearing capacity and the load, with the reliability analysis method and the theory of probability and statistics, the calculation formulas of reliability indices for ultimate limit state （ULS） and serviceability limit state （SLS） are obtained respectively. Meanwhile, the linear relationship between reliability indices for ULS and SLS is presented. Finally, it is studied that the impact of stochastic behaviors of limiting tolerable settlement of pile head （ sit ） on reliability analysis for SLS. The following conclusions can be drawn from this study. First, the influences of soil type and pile type on the model factor for SLS are slight. Second, the reliability index for SLS decreases with an increase of the uncertainties from the bearing capacity calculation model and the load, although the decrease rate gradually diminishes. And the total variation in the reliability index for SLS is limited, which means that it is reasonable to ignore the influences of the uncertainties from the bearing capacity calculation model and the load on the reliability analysis for SLS in engineering practice. Third, the stochastic behaviors of sL, have significant effect on reliability analysis for SLS. The model factor and reliability index for SLS both increase with an increase of s~t. However, the variability of model factor for SLS decreases with increase of sit. The appearance of these conclusions is simply because the requirements of stt are different, but is not the result that the pile own properties have run into some changes. The research results would provide a reference for code amendment and engineering applications.