HRB500钢筋预应力超高性能混凝土梁受力性能研究

发布时间：2018-06-07 00:19

本文选题：超高性能混凝土 + HRB500　；参考：《北京工业大学》2015年博士论文

【摘要】：超高性能混凝土(Ultra High Performance Concrete,简称UHPC)是一种新型水泥基复合材料,具有较高的力学性能和良好的耐久性,在土木工程领域具有广阔的应用前景,然而目前对其结构受力性能缺乏足够的研究。HRB500级钢筋是一种新型热轧带肋钢筋,具有较高的强度和良好的延性,工程中采用HRB500钢筋具有节省钢筋用量、方便钢筋布置等优点。将UHPC和HRB500钢筋结合起来,可以充分发挥二者的优良性能,达到减轻混凝土结构的自重、简化钢筋布置、增大结构跨越能力、增加结构耐久性的目的。本文对HRB500钢筋UHPC梁进行了系列试验研究和理论分析,探讨了HRB500钢筋和UHPC材料的适配性,对UHPC梁的受力性能和设计计算理论进行了研究。主要研究内容如下:(1)完成了UHPC抗压强度、抗拉强度、抗折强度等基本力学性能试验,分析了养护方法、振捣方法对UHPC基本力学性能的影响,获得了UHPC轴心受压应力—应变关系曲线的上升段,并拟合了轴心受压应力—应变曲线上升段的方程。试验表明:UHPC的峰值压应力对应的压应变远高于普通混凝土,接近3000×10-6。UHPC开裂后裂缝间的钢纤维承担拉应力,轴拉应力随裂缝宽度的增大和裂缝间钢纤维的拔出而逐渐减小。(2)完成了6根后张法预应力UHPC简支梁的抗弯性能试验。对试验梁的受力过程、裂缝分布形态及发展情况、荷载—挠度曲线特征以及破坏模式进行了详细的阐述和分析。试验表明:HRB500钢筋与UHPC梁适配良好,UHPC梁弯曲裂缝细而密,正常使用极限状态下试验梁最大裂缝宽度不大于0.15mm,试验梁位移延性系数均大于3。根据试验建议了UHPC轴拉及轴压应力-应变关系曲线并给出了相应的方程;计算UHPC梁开裂弯矩时,考虑钢纤维对受拉区塑性发展程度的增强作用,引入抗裂修正系数对《预应力及钢筋混凝土桥涵设计规范》(JTG D62-2004)中开裂弯矩计算公式进行了修正,修正后计算结果与试验值吻合较好。计算裂缝宽度时,考虑钢纤维的增韧阻裂作用,引入裂缝修正系数对《混凝土结构设计规范》(GB50010-2010)中计算最大裂缝宽度的公式进行了修正,修正后计算值与试验值吻合良好;建立了UHPC梁极限承载力计算公式,理论计算值与试验值吻合良好,可作为UHPC梁理论分析和设计的参考。(3)完成了9根UHPC梁的抗剪性能试验研究。试验表明:随剪跨比的增大,试验梁破坏形式从斜压破坏逐渐转向剪压破坏、斜拉破坏;受剪斜裂缝细而密,正常使用极限状态下最大斜裂缝宽度不大于0.2mm;HRB500钢筋作箍筋时,其高强性能可以得到充分发挥;影响抗剪承载力的主要因素包括剪跨比、预加力、配箍率等。根据UHPC梁抗剪试验推导了UHPC梁开裂剪力和正常使用极限状态下最大斜裂缝宽度的计算公式;利用现有规范对UHPC的抗剪承载力进行了计算,计算结果表明现有规范计算结果过于保守;在修正压力场理论的基础上,考虑梁上部受压区混凝土和下部受拉区骨料咬合力、钢纤维有效拉力及箍筋共同提供抗剪承载力,推导了UHPC梁的抗剪承载力计算方法,并给出了简化的显示表达式,与本文试验的结果比较表明,采用该方法计算的抗剪承载力与试验结果吻合良好;最后考虑剪跨比、配箍率、预加力因素建立了超高性能混凝土梁的抗剪承载力的统计计算公式,计算值与试验值吻合较好,且变异系数较小。(4)为研究超高性能混凝土连续梁的内力重分布问题,利用非线性分析方法编制了计算弯矩调幅系数的计算程序。通过对22根HRB500钢筋超高性能混凝土连续梁的数值分析,得到了22根模拟梁在跨中集中荷载作用下达到极限承载力时的弯矩调幅系数,拟合了以截面相对受压区高度为自变量的弯矩调幅系数计算公式;最后以满足正常使用极限状态下最大裂缝宽度不大于0.2mm为条件,建议了HRB500钢筋超高性能混凝土梁的弯矩调幅系数取值方法。
[Abstract]:Ultra High Performance Concrete (UHPC) is a new type of cement based composite material. It has high mechanical properties and good durability. It has a broad application prospect in the field of civil engineering. However, the lack of sufficient research on the mechanical properties of its structure is a new type of hot rolled strip. Ribbed reinforcing bar, with high strength and good ductility, HRB500 steel has the advantages of saving steel and reinforcing bar arrangement in engineering. Combining UHPC and HRB500 steel, the excellent performance of two people can be fully played to reduce the weight of concrete structure, simplify the arrangement of steel bar, increase the structure leaping ability and increase the structure. The purpose of durability is to carry out a series of experimental research and theoretical analysis on HRB500 reinforced UHPC beams. The compatibility of HRB500 steel and UHPC materials is discussed. The stress performance and design calculation theory of UHPC beams are studied. The main contents are as follows: (1) the basic mechanical properties of UHPC, tensile strength, tensile strength and flexural strength have been completed. The effect of the curing method and vibration method on the basic mechanical properties of UHPC is analyzed. The rise section of the stress-strain relationship curve of the UHPC axle center is obtained, and the equation of the rising section of the axial compression stress-strain curve is fitted. The test shows that the compressive strain of the peak pressure stress on the UHPC is far higher than that of the ordinary concrete, close to 3000 x 10-6. The tensile stress of the steel fibers between cracks after.UHPC cracking, the axial tensile stress as the crack width increases and the steel fiber pullout between the cracks gradually decreases. (2) the flexural performance test of 6 post tensioned prestressed simple supported beams is completed. The stress process, the distribution and development of the crack, the load deflection curve and the characteristics of the load deflection curve of the test beam are made. The failure mode is elaborated and analyzed in detail. The test shows that the HRB500 bar is well suited to the UHPC beam, the bending crack of the UHPC beam is fine and dense. The maximum crack width of the test beam is not more than 0.15mm under the normal use limit state, and the displacement ductility coefficient of the test beam is more than 3.. The stress strain relationship curve of the axial tension and axial compression of the UHPC axis is proposed. The corresponding equation is given. When calculating the cracking moment of UHPC beam, considering the strengthening effect of steel fiber on the plastic development of the tensile zone, the formula of cracking bending moment in the code for design of "prestressed and reinforced concrete bridge and culvert" (JTG D62-2004) is amended by introducing the crack resistance correction coefficient, and the calculation results are in good agreement with the experimental values. In the crack width, considering the toughening and resistance cracking of steel fiber, the formula for calculating the maximum crack width in the design code for concrete structure (GB50010-2010) is amended by introducing the fracture correction coefficient, and the calculated value is in good agreement with the test value, and the formula of ultimate bearing capacity of the UHPC beam is established, the theoretical calculation value is in good agreement with the test value. Well, it can be used as a reference for the theoretical analysis and design of UHPC beams. (3) the experimental study on the shear performance of 9 UHPC beams has been completed. The test shows that the failure form of the test beam is gradually turned from baroclinic failure to shear stress failure, slanting failure, slanting cracks are fine and dense with the increase of shear span ratio, and the maximum slanting crack width is not more than 0.2mm under the normal use limit state. When HRB500 steel is used as stirrup, its high strength performance can be brought into full play. The main factors affecting the shear bearing capacity include the shear span ratio, the preloading force, the stirrup rate and so on. According to the shear test of the UHPC beam, the calculation formula of the cracking shear force of the UHPC beam and the maximum slanting crack width under the normal use limit state is derived. The shear bearing capacity of the existing standard on the shear bearing capacity of the UHPC is used. The load is calculated, and the calculation results show that the existing standard calculation results are too conservative. On the basis of the modified pressure field theory, the shear bearing capacity of the concrete and the lower part of the tensile zone in the upper part of the beam is considered, the effective tensile force and the stirrup of the steel fiber are jointly provided, and the calculation method of the shear bearing capacity of the UHPC beam is derived, and the calculation method of the shear bearing capacity of the beam is derived. The simplified display expression is compared with the results of the experiment in this paper. It shows that the shear bearing capacity calculated by this method is in good agreement with the test results. Finally, a statistical formula for calculating the shear bearing capacity of super high performance concrete beams is established by considering the shear span ratio, the stirrup rate and the preloading factors. The calculated values are in good agreement with the experimental values and the variation coefficients are in good agreement. (4) (4) in order to study the internal force redistribution of the continuous beam of super high performance concrete, a calculation program for calculating the amplitude coefficient of bending moment is developed by using the nonlinear analysis method. Through the numerical analysis of 22 HRB500 reinforced concrete continuous beams, the ultimate bearing capacity of 22 simulated beams under the central load of the middle span is obtained. The amplitude modulation coefficient of the bending moment is fitted to the formula of the moment modulation coefficient of the bending moment with the height of the section relative to the compression zone as the independent variable. Finally, the method of the moment adjustment coefficient of the bending moment of the HRB500 reinforced concrete beam is proposed to satisfy the condition that the maximum crack width is not more than 0.2mm under the normal operating limit state.
【学位授予单位】：北京工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU378.2

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