Experiment on flexural behavior of UHPC wet joints without formwork
According to the mechanical characteristics of wet joints of prefabricated steel-concrete structural deck slabs and the existing joint construction forms,a ultra high performance concrete(UHPC)wet joint without formwork was proposed.In order to test the mechanical behavior of this structure,five test beams were designed,including two overall beams,one joint beam with formwork and two joint beams without formwork,and the steel fiber content was used as the test parameter.The flexural behavior of the test beams was investigated by four-point loading,and the specimen's cracking load,crack distribution,damage mode and stress-strain state and other key test results were obtained.The results show that both the joint beams and the overall beams undergo bending failure,and the failure modes of each joint beams are basically the same.All of joint beams show cracks appeared in the UHPC-NC interface first.The width of the old cracks increases and the new ones appeare one after another with the load increase.When reaching the limit state,the main cracks penetrat through the webs,the reinforcement yield in tension,and the top plate collaps.The main cracks of the joint beams with formwork are concentrated in the normal concrete(NC)prefabricated section,while the main cracks of the joint beams without formwork are concentrated in the interface between old and new concrete and its adjacent joint area.Compared with the NC overall beam,the joint beams of the formwork free with prefabricated UHPC thin plates have reduced bending bearing capacity and enhanced crack resistance.The increase of the steel fiber content can enhance the bonding of UHPC-NC interface,and improve the cracking resistance and the bending bearing capacity of the specimens.The bending bearing capacity of the formwork free joint beam containing prefabricated UHPC thin plate with a steel fiber content of 1.0％is only slightly reduced,and its crack resistance is only second to that of UHPC overall beam,solving the problem of easy cracking of UHPC-NC interface,indicating that the application of this structure in practical engineering is feasible and reliable.This paper recommends using ultra-high performance concrete with a steel fiber content of over 1％as the joint material for this structure.5 tabs,11 figs,26 refs.
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