Structural response of stainless steel composite bridge beams with welded shear studs

This thesis investigates the structural response of stainless steel-concrete composite bridge beams with a focus on welded shear studs. Unlike carbon steel, the durability of stainless steel prevents corrosion of the beams, significantly reducing maintenance and life-cycle costs. Stainless steel exhibits non-linear material behaviour with significant strain hardening and its design therefore differs from carbon steel. Codified design guidance for stainless steel-concrete composite beams is limited, and generally yields over-conservative predictions. The high cost of stainless steel necessitates efficient design to minimise material consumption, which in turn reduces environmental impacts.Due to the protection offered by the concrete slab, both stainless steel and carbon steel welded shear studs were considered. Tensile coupon and double shear tests were performed on austenitic EN 1.4301 stainless steel SD3 shear studs and carbon steel SD1 shear studs. Tensile tests were carried out on five austenitic EN 1.4301 stainless steel and five carbon steel shear studs welded to lean duplex EN 1.4162 plates, alongside X-ray computerized tomography and microstructure analysis to assess the weld quality. Eight push-out tests according to Eurocode 4 were conducted; three with carbon steel studs, and five with austenitic EN 1.4301 studs, welded to lean duplex EN 1.4162 beams. A validated numerical model was used to conduct a parametric study on stainless steel welded shear studs in solid slabs. Stud capacities from experimental and numerical studies were compared with predicted capacities from international design codes. Validated numerical models of composite stainless steel-concrete beams under four-point bending were used to assess the accuracy of rigid-plastic analysis methods as well as alternative methods incorporating the effect of strain-hardening for predicting the flexural capacity of stainless steel-concrete composite beams. The investigations concluded that welding carbon steel studs to stainless steel beams is not viable due to poor quality of the weld leading to unpredictable brittle behaviour. Stainless steel studs exhibited 32% higher load capacity and 262% greater slip capacity than carbon steel studs. Existing design codes under-estimate stainless steel stud resistance, and the height-to-diameter ratio limit in Eurocode 4 can be relaxed from 3 to 2. A new resistance equation for stainless steel and carbon steel shear studs is proposed, based on regression and reliability analyses. Furthermore, rigid-plastic analysis was found to give conservative results for predicting the flexural capacity of stainless-steel concrete composite beams. Newly proposed strain hardening methods are up to 15% more efficient, while still giving safe predictions.