Mechanical Property Study on Cap Beam of Single-column Pier with Small Width-thickness Ratio Based on Topology Optimization and Scale-down Test
Since the cap beam of single-column pier with small width-thickness ratio belongs to the typical stress disturbance zone members,its complicated internal forces make it unapplicable to the design method for ordinary cap beam of single-column pier.The topology optimization was performed on the model of cap beam of single-column pier with small width-thickness ratio,and its spatial force characteristics were analyzed.The basic configuration of spatial strut-and-tie model of cap beam of single-column pier with small width-thickness ratio was established based on the topology optimization results.The method for determining optimal configuration was proposed according to the minimum strain energy criterion.In view of limited experimental studies on cap beam of single-column pier with small width-thickness ratio,a scale-down model test was conducted to investigate the force characteristics under vertical static loading.The result indicates that in the transverse direction,the top of cap beam has the maximum tension stress under double support loads.In the longitudinal direction,the middle of cap beam has the maximum tension stress,the top of cap beam has lower tension stress than the middle of cap beam,and the bottom of cap beam shows a tendency of being subjected to compression.Since the force diffusion in longitudinal direction is not considered,the internal forces calculated according to strut-and-tie model design method in the relevant specification differed greatly from test result,indicating that the method in specification is not applicable to the design of cap beam of single-column pier with small width-thickness ratio.The stress distribution of test result is consistent with that of spatial strut-and-tie model proposed based on topology optimization result.The stress values of strut-and-tie calculated with spatial strut-and-tie model are more reasonable compared with those obtained with the method in specification.It proves the reasonableness of basic configuration of spatial strut-and-tie model and the method for determining optimal configuration proposed in this study.
bridge engineeringcap beam of single-column pier with small width-thickness ratiospatial strut-and-tie modeltopology optimizationscale-down model test
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