Experimental and numerical study of S700 high strength steel double shear bolted connections in tension

This paper presents a thorough experimental and numerical study of the structural behaviour and resistance of S700 high strength steel double shear bolted connections subjected to tension. A total of 38 S700 high strength steel double shear bolted connections were adopted in the tests, and included seven 1-bolt connections (with each containing one bolt), ten 2-pe-bolt connections (with each containing two bolts arranged perpendicular to the load transfer direction), eight 2-pa-bolt connections (with each containing two bolts arranged parallel to the load transfer direction) and thirteen 4-bolt connections (with each containing four bolts arranged in two rows). The specimens were carefully designed with a series of geometric parameters, including the end distance, the edge distance, the longitudinal spacing and the transverse spacing, varied and examined. The test setup, procedures and key results, including the failure loads and modes as well as the load–elongation curves, were fully reported. Two types of failure modes, namely net section fracture and bearing failure, were observed from the tests, with their underlying mechanisms discussed. The effects of various geometric parameters on the failure loads and modes of the S700 high strength steel double shear bolted connection specimens were studied. It was generally found that the net section fracture behaviour and resistance are sensitive to the edge distance and transverse spacing, while the bearing behaviour and resistance are more dependent on the end distance and longitudinal spacing. The experimental programme was supplemented by a numerical modelling programme, where finite element models were initially developed and validated against the test results, and then used for conducting parametric studies to generate further numerical data over a wide range of geometric dimensions. The experimentally and numerically obtained failure loads and modes were then adopted to assess the accuracy of the relevant design rules for high strength steel double shear bolted connections in tension, as given in the European code, American specification and Australian standard. The results of the assessment revealed that (i) the American specification yields the most accurate failure load predictions on average, but with many over-predicted failure loads and inaccurate failure mode predictions, (ii) the Australian standard leads to less accurate but more consistent and safe predictions of failure load than the American specification, and (iii) the European code results in the most conservative and scattered failure load predictions among the three considered design codes, but with the best failure mode predictions. The development of improved design approaches for S700 high strength steel double shear bolted connections is underway.