6. Conclusions
An analysis based on the reliability of seismic bearing capacity of strip foundation subjected to a vertical load with pseudo-static seismic loading is presented in this paper. The main conclusions are drawn as follows:
(1) The use of GA is very effective in optimizing the unknown parameters of the performance limit function. A quadratic polynomial function with crossed terms between the parameters makes it possible to obtain a satisfactory approximation of the limit performance state in the previous analyses.
(2) Assumption of negatively correlated shear strength parameters (c, 4) was found conservative with respect to uncorrelated variables. For uncorrelated shear strength parameters values, the design point value c* slightly exceeds the average value of c, which gives partial safety coefficients Fc less than 1 and large values of F4 and Fkh . For this reason, a case with Fc less than 1 does not necessarily indicate failure, as long as the value of F4 is high.
(3) For the higher values of the minimum seismic bearing capacity, the reliability index bHL is low and induces a very high failure probability value, indicating the vulnerability of this structure.
(4) The simplified assumption considering a normal variable is safer compared to more complex probabilistic models (nonnormal variables). This can lead to uneconomical designs.
