A vehicle test was carried out on Hythe End bridge shortly before its demolition. The bridge consisted of two spans, each of which contained four cast iron beams supporting transverse jack arches. The deck was tested using the rear bogie of an articulated trailer loaded with concrete blocks. The maximum load used represented about 46% of the full assessment loading, expressed in terms of mid-span moment. The main objectives of the test were to investigate the accuracy of the composite action provision in BD 21/84 and the efficacy of the simple method of load distribution contained in BA 16/84. It was also proposed to investigate a more rigorous method of analysis (grillage) and provide evidence of the value of vehicle loading tests for bridge assessment. The main conclusions are: The effect of composite action was greater than BD 21/84 suggested; The simple method of load distribution given in BA 16/84 is reasonably accurate, but can over-estimate the stress in the external beams when the loaded lane does not lie over them; Grillage analysis can be used to model the bridge with reasonable accuracy; The load test effectively demonstrated that it can be advantageous to carry out a load test as an aid to assessment.
Abstract