Experimental study on bond splitting strength of ultra-high performance concrete with steel bars
As a novel composite material,ultra-high performance concrete(UHPC)could reduce the bond length and significantly enhance the bond behavior with reinforcement.Currently,the research on the bond performance of UHPC often uses pull-out tests or lap-shear tests,which makes it difficult to simulate the actual bond situation of bending components such as beams and columns.Therefore,it is necessary to study the bond behavior of UHPC with steel bars under bending stress conditions.In this paper,a four-point loading test was carried out on 17 lap-spliced beams.The test parameters included UHPC compressive strength,cover depth,fiber volume fraction,splice length and stirrups in the spliced region.Test results indicate that the specimens are dominated by splitting failure.The bond strength is improved by increasing the UHPC strength and cover depth and decreases with increasing lap length.The configuration of stirrups in the splice region can effectively improve the bond strength of the specimen,but there is a threshold for the improvement of the bond strength of the stirrups.When the threshold is reached,the improvement of the bond strength will no longer be obvious with the increase of the number of stirrups.In addition,the existing bond strength calculation models are evaluated,and existing calculation models are found to be more conservative in predicting the UHPC splitting bond strength,and the degree of discretization is larger.On this basis,an improved expression for UHPC splitting bond strength calculation is proposed,which can accurately reflect the influence of various design parameters on the splitting bond strength,and the average ratio of calculated results to experimental results in this paper and related literature is 1.076,with a coefficient of variation is 0.149.
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