Experimental and numerical analyses on the behavior of civil and marine steel structures

Abstract

Bolts and welds in combination occur most commonly during the construction phase of a building when the design load changes, when there are unforeseen difficulties in make-up or matching of bolt holes, or in retrofit of existing structures. Due to the different load-displacement behavior of the bolts and welds, the behavior of the combination connections may change in different conditions. Pretensioned high-strength bolts and longitudinal fillet welds in combination has been studied both experimentally and numerically. Slip-dependent surface frictional and ductile fracture models have been incorporated in the numerical analysis to address the strain compatibility between bolts and welds. Effects of critical variables, e.g., bolt pattern, faying surface, weld size, weld location, and weld/bolt strength ratio have simulated and discussed. Similarly, the fatigue behavior of stiffened panels under variable amplitude loading has been investigated. These panels are commonly found in steel structures, such as naval vessels and bridges subjected to random variable loading. An experimental fatigue test was conducted for the stiffened box girder under variable amplitude loading. An XFEM-based fatigue crack prediction approach was proposed based on the crack closure concept. Prediction were made using the proposed approach considering the loading history effect as well as stiffener effect, and residual stresses due to welding.