Abstract：The design of latticed shell is governed by the global instability requirements for gravity load and specified shape and amplitude of maximum initial geometric imperfection (IGI). The assigned shape and maximum IGI is unknown. In the present study, IGI is modelled using the simultaneous autoregressive model. By using this model, the effect of the spatially correlated IGI on the probability distribution of the load capacity for global instability and the reliability of spherical and cylindrical latticed shell is assessed. Furthermore, the effect of Young’s modulus on the probability distribution of the load capacity and the reliability under different load combinations are assessed. Under permanent load and snow load, the effect of Young’s modulus can be ignored. A critical load factor of 2 implemented in the code leads to a failure probability less than about 6.5×10-5if the specified maximum IGI defined in the code equals about two to three times the standard deviation of IGI. This failure probability becomes less than about 5.1×10-4 if a critical load factor of 1.5 is used. Under permanent load and live load, a critical load factor of 2 leads to negligible failure probabilities for two latticed shells if the specified maximum IGI equals about two to three times the standard deviation of IGI. This failure probability becomes less than about 10-7 for spherical latticed shell and 10-6 for cylindrical latticed shell if a critical load factor of 1.5 is used. It is suggested that the critical load factor may be reduced to 1.5 while achieving target reliability index often adopted for design code, and different critical load factors can be determined for different regions.
