新型超高性能混凝土湿接缝连续T梁抗弯性能试验及有限元分析

Test and Finite Element Analysis on Flexural Performance of Continuous T-beams with New Type Ultra-High Performance Concrete Wet Joint

为提高普通混凝土连续梁桥负弯矩抗裂性能,以30 m预应力混凝土简支转连续T梁为原型和设计一个1∶5的缩尺试验模型梁,对其进行抗弯试验,具体对试验梁的破坏形态、跨中荷载-挠度关系、跨中截面应变、裂缝分布、刚度折减进行分析研究。采用有限元软件ABAQUS建立试验梁的有限元模型,利用有限元模型分析不同湿接缝材料、预制部分混凝土强度等级、纵向钢筋配筋率和超高性能混凝土(UHPC)抗拉强度对梁抗弯性能的影响。试验结果表明,新型构造湿接缝设计具有合理性,能提高梁的整体刚度、耐久性和安全性,满足工程实际要求。超高性能混凝土的引入能够有效地减小裂缝宽度,显著提高普通混凝土(normal concrete,NC)截面的刚度;实际试验值与模型模拟值拟合程度良好,所建立的有限元模型具有一定的准确性和适用性。参数分析表明,提高配筋率能够显著提高梁的极限承载力和开裂后的刚度,但是对开裂荷载和开裂前的抗弯性能影响较小;采用UHPC代替普通混凝土C30作为湿接缝材料明显提高了梁的承载能力和刚度,验证了此设计方案的合理性;预制部分的强度等级,能够提高梁的极限承载能力,但影响较小,对梁开裂前的受弯性能影响很小,而UHPC抗拉强度对梁整体的承载能力、刚度和破坏挠度几乎没有影响。

In order to improve the crack resistance of ordinary concrete continuous girder bridges in the negative moment,the 1∶5 scale model girder was designed and subjected to the flexural test as a prototype of a 30 m prestressed concrete simple supported-continuous T-beam.The failure mode,mid-span load-displacement relationship and strain,crack distribution,and stiffness degeneration were investigated.The finite element model of the test beam was established using the finite element software ABAQUS,which was used to analyze the effect of different wet joint materials,concrete strength grades in the precast section,longitudinal reinforcement rates and UHPC tensile strength on the flexural performance of the beam.The test results showed that the new structural wet joint design was reasonable and can improve the overall stiffness,durability and safety of the beam to meet the actual requirements of the project.The introduction of UHPC could effectively limit the crack width,significantly increase the rigidity of normal concrete(NC)sections.The test values were well fitted with the model simulation values,indicating that the finite element model established had certain accuracy and applicability.The parameter analysis showed that improving the reinforcement ratio could significantly increase the ultimate bearing capacity and post-cracking stiffness of the beam,but had little effect on the cracking load and pre-cracking flexural properties.The use of UHPC instead of plain concrete C30 as the wet joint material obviously improved the load carrying capacity and stiffness of the beam,which verified the reasonableness of this design scheme.The tensile strength of UHPC could improve the ultimate load carrying capacity of the beam by a small margin,and had little effect on flexural capacity before cracking.While the tensile strength of UHPC had almost no effect on the load carrying capacity,stiffness and damage deflection of the whole beam.