| Ultra-high-performance concrete(UHPC)is expected to provide a solution for the development of segmented prefabricated bridges towards lightweight,high-strength,and rapid construction due to their excellent material properties,but for segmented prefabricated spliced beams Due to the discontinuity of the non-prestressed rebar,the splicing joint becomes a weak point.The type of teeth at the joint and the pre-stress of the component will affect the bending performance of the prefabricated beam.In this paper,the bending performance of UHPC segment beams is studied through five beams.The main contents and conclusions are as follows:(1)The comparative analysis of the cast-in-place beam and the spliced beam is completed,and the results show that the flexural capacity of the cast-in-place beam is 9%-15% lower than that of the cast-in-place beam under the same conditions;When the test beam reaches the ultimate failure,the maximum compressive strain of the compressed edge can reach more than 7200 ??;The joint structure has a small effect on the load-deflection curve but will affect the ductility of the members.Although the UHPC test beams have good ductility,the test results show that the ductility of the joint beam is better than that of the cast-in-place beam;Regardless of whether or not the splicing joint strain is distributed along the cross-section height,it basically meets the assumption of flat section,and the failure mode of the cast-in-place beam and the splice beam is that the concrete in the compression zone is crushed,but there is a difference in the crack distribution.The characteristics of "fine and dense" are different.The bending cracks of the splicing beam are mainly concentrated on the position of the splicing joint.(2)The effects of the type of teeth at the joint and the pre-stress on the bending performance of the test beam are analyzed.The analysis results show that the pre-stress mainly affects the ductility of the test beam and has a small effect on its bearingcapacity;The fracture morphology and crack distribution of spliced beams with different numbers of teeth are similar.However,the number of healthy teeth has a certain effect on the bending bearing capacity of the segment splicing beam.The bearing capacity of multi-toothed members is 4.5% lower than that of single-toothed members under the same conditions.(3)Using the finite element analysis software ABAQUS to numerically simulate the bending performance of UHPC segment prefabricated assembled beams,After verifying the selected unit type,contact relationship,and boundary conditions with the test results,the concrete strength,preload stress,and key tooth depth parameters of the test beam are analyzed.The results show that: The three parameters of tooth depth all have an influence on the flexural capacity of the test beam;With the increase of concrete strength,the bending bearing capacity of the test beam also increases;the number of key teeth has a small effect on the bending bearing capacity,and the single tooth testing beam has the largest bending bearing capacity and good ductility;Due to the conical action of the key teeth,the greater the depth of the key teeth,the greater the bending load capacity of the test beam.(4)Based on experimental data and finite element simulation data,it is shown that the joint reduction factor proposed by the American AASHTO-PCI-ASBI S B G segment beam design code is basically suitable for UHPC segment assembled beams,but the reduction factor should also be related to the type of key teeth.Through the verification of the test data and other literature data in this paper,the bond strength of epoxy resin to concrete is considered,and it has good applicability to the calculation of the bending capacity of UHPC segment precast beams,and the form of the proposed formula is Calculation also has good applicability. |
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