木结构螺栓连接可靠度分析

Strength design values of wood and wood products in GB 50005—2017‘Standard for design of timber structures’have already been determined via the reliability analysis. Yet the design values for load-carrying capability of bolted connections are determined by calibration against the values from the old design code GB 50005—2003，which is an expedient measure without conducting the reliability analysis. This makes the design of wood members and bolted connections disjointed in both the design principles and methods. To overcome the situation，the statistical parameters of the random variables，such as the model uncertainty factor，which affect the performance of the bolted connections，were derived from the results of the related dowel-bearing tests and bolted connection tests. The performance functions of the bolted connections were developed，and the systematic reliability analysis was conducted. The variations of the material property partial factor for the dowel-bearing strength were thus revealed. It is shown that the material property partial factor γ_w for dowel-bearing strength mainly varies with the type of load combinations，the live to dead load ratio ρ and dowel-bearing parallel or perpendicular to grain，whilst it varies little with the connection form of single-shear or double-shear and the yield mode of the connections. Furthermore，the suggestions for the design of the bolted connections were proposed. The combination of dead load and residential floor live load with a live to dead load ratio ρ of 1. 0 is taken as the reference point for determining the material property partial factor γ_w for dowel-bearing strength，with a value of 1. 38 when dowel-bearing is parallel to grain，and 1. 70 when dowel-bearing is perpendicular to grain. When it is under sole dead load，the reference dowel-bearing strength is multiplied by a modification factor of 0. 75. For the combination of dead load and residential floor live load with ρ< 1. 0，the reference dowel-bearing strength is multiplied by a factor of K_D（K_D=0. 75+0. 25ρ）. For the combination of dead load and office floor live load with ρ<1. 0，the reference dowel-bearing strength is multiplied by a factor of 1. 15K_D，and with ρ≥1. 0，the reference dowel-bearing strength is multiplied by a factor of 1. 15. For the combination of dead load and snow load，the reference dowel-bearing strength is multiplied by a factor of 0. 75. For the combination of dead load and wind load，the reference dowel-bearing strength is multiplied by a factor of 0. 85.