Study on axial compression behavior of pre-stressed circular concrete columns confined by bolted steel tube
Bolted steel tube(BST)confined concrete columns offer the advantage of easy disassembly and replaced of the steel plates,better recoverability than the concrete columns confined by steel tube.Taking the BST confined concrete column as the research object,the method of applying pre-compressive stress to it by reserving a gap between two assembled steel plates and tightening the bolts was proposed.Axial compression tests were conducted on six BST confined concrete columns and one unconfined concrete column,with parameters including the magnitude of applied pre-compressive stress and the diameter-to-thickness ratio.The results indicate that the method of reserving a gap and tightening the bolts can effectively apply pre-compressive stress to the core concrete,thereby steel plate can form effective confinement to core concrete prior to loading.Compared to unconfined concrete columns,the peak stress of BST confined concrete columns with pre-compressive stress under the same condition can increase by up to 74.5%,while the residual strength after the peak can be maintained at 92.3%of the peak stress.Compared to BST confined concrete columns without pre-compressive stress,the larger the pre-compressive stress of BST confined concrete columns with pre-compressive stress,the higher the peak stress,which can be increased by a maximum of 18%.The smaller the diameter-to-thickness ratio is,the higher the peak stress of the BST confined concrete columns is,but the magnitude of the peak stress increase decreases with the increase of the pre-compressive stress.
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