【作者】 黄文雄；

【导师】 张海龙；

【作者基本信息】 华中科技大学 ， 桥梁与隧道工程， 2012， 博士

【摘要】 折线配筋预应力混凝土先张梁采用了与结构受力特点相适应的布筋方式,解决了先张梁跨度较小的不足,避免了后张法在施工工艺和耐久性能等方面的缺憾,是一种同时具备先张法与后张法结构优点的新型结构。本文基于折线配筋先张梁本身力学特性,采用非线性有限元法详细分析了其折点部位局部应力分布状况,针对性的研制了改善并适应局部应力特点的新型先张折线预应力筋弯起器,并采用试验方法研究对比了新型弯起器与传统弯起器对预应力钢绞线力学性能的影响以及弯起器摩阻预应力损失的变化规律；同时采用理论分析、数值仿真、试验研究相结合的方法,对采用新型弯起器与传统弯起器的折线配筋先张梁整体力学性能与局部受力特点进行了详细分析与对比,多方面证实了新型弯起器对先张梁局部力学状态与整体力学性能的改善作用。本文主要工作如下：1、折线配筋先张梁局部应力分析与折点半径优选：以非线性有限元理论为基础,以ANSYS大型通用有限元分析软件为平台,详细分析了折线配筋预应力混凝土先张梁折点部位的局部力学性能与应力分布特点,得出折线预应力筋折点半径是影响折点部位应力分布规律与应力集中现象的主要因素的结论；进而对其进行优选,得出折线预应力筋合理折点半径。2、新型弯起器的研制及其对钢铰线力学性能影响的试验研究：基于优选的折点半径,设计研制了构造简洁、拼装灵活的新型折线配筋先张梁弯起器；并采用试验方法研究了新型弯起器与传统弯起器对预应力钢绞线力学性能的影响,证实了新型弯起器的科学性；同时以试验数据为基础,提出了考虑不同导向半径R影响的弯起器摩阻预应力损失的统一计算公式。3、折线先张试验梁的设计制作与施工监测：根据研究目的对8根试验梁的结构与配筋进行了设计与制作,并对其各项力学参数进行施工监测,为后期试验提供了测试初值；同时监测了折线预应力钢绞线的各项预应力损失,讨论了考虑反向摩擦阻力影响的锚具变形钢筋回缩预应力损失的计算方法,验证了考虑不同导向半径R影响的弯起器摩阻预应力损失统一计算公式的科学性与适用性。4、静力荷载作用下折线先张梁力学性能研究：完成了5根折线配筋先张梁的单调静力荷载作用下力学性能试验,通过试验实测数据、有限元分析结果、理论计算结果的对比,分析了试验梁承载能力、变形能力、延性性能等力学性能,以及荷载—挠度、荷载—应变等发展规律,观测了试验梁裂缝、挠度发展规律及试验梁破坏形态；着重对比了相同结构采用不同弯起器的先张梁力学性能之间的异同,得出新型弯起器将大大改善折线配筋先张梁的极限变形能力与延性性能的结论。5、折线配筋先张梁局部应力的监测与精细化有限元分析：基于折线先张梁本身力学特性,以ANSYS大型通用有限元分析软件为平台,采用子模型法建立了折线配筋先张梁弯起器部位精细化有限元分析模型,详细分析了采用新型弯起器与传统弯起器的先张梁其弯起器所在部位的局部应力分布状态,对比了采用不同弯起器时先张梁局部应力分布的异同,验证了新型弯起器对先张梁局部应力状态的改善作用；同时基于自主设计的混凝土局部应变测试元件,对静载试验过程中先张梁局部应变进行了监测与分析,着重对比了相同结构采用不同弯起器的先张梁局部力学性能之间的异同,证实了新型弯起器对先张梁局部应力状态的改善作用。6、等幅疲劳荷载作用下折线先张梁力学性能研究：完成了2根相同结构采用不同弯起器的折线先张梁等幅疲劳荷载试验及后期静载破坏试验,分析了疲劳荷载重复作用对试验梁承载能力、挠度、延性,以及混凝土、钢绞线、普通受拉钢筋、弯起器部位混凝土局部应变的影响规律,着重对比了疲劳荷载重复作用对采用不同弯起器先张梁力学性能影响之间的异同,结果表明新型弯起器将大大改善折线先张梁的抗疲劳性能,再次证实了新型弯起器对先张梁局部应力状态与整体力学性能的改善作用。更多还原

【Abstract】 The polyline pretensioned beams (PPSCB) is a new structure which combine the advantages of pre-tensioned and post-tensioned structure. It adopts the reasonable arrangement of prestressed reinforcement, solved the deficiency in span of the traditional pre-tensioned structure, avoided the shortcomings in construction technology and durability of the post-tensioned structure. Based on the peculiar mechanical properties of PPSCB, the local stress distribution in some key position is analyzed by the nonlinear finite element method, and the new bend component is developed by optimization corner radius which can adapt and improve the local stress characteristics. Then the law and mechanism of steel strand mechanical properties and prestressing loss due to friction affected by the new and traditional bend component is analyzed and compared by experimental method. Then, combined the experimental study with theoretical analysis and numerical simulation, the overall mechanical properties and local stress states affected by the new and traditional bend component is studied and compared. The significant improvement on the local stress states and overall mechanical properties by the new bend component is confirmed in difference ways. The main works of this paper is as follows:1. The analysis of local stress and optimization of corner radius. Based on the nonlinear finite element theory and the general FEM software ANSYS, the local mechanical properties and stress distribution at the polyline prestressed reinforcement inflection point is analyzed detailedly. The results show that the main influencing factor of the complicated local stress states and stress concentration phenomenon is the corner radius of the polygonal line prestressed reinforcement. Then the corner radius is optimized, and the reasonable radius is obtained.2. The development of new bend component and the experimental study of its effection on the mechanical properties of steel strand. Based on the optimization corner radius, the new bend component is developed which is simple structure and easy to assemble flexibility. Then the law and mechanism of steel strand mechanical properties and prestressing loss due to friction affected by the new and traditional bend component is analyzed and compared by experimental method, and the scientificity and practicability of the new bend component is confirmed. The uniform formulas of prestressing loss due to friction is presented based on test data, which take the affection factor of R into account. It provides some design reference and test basis to further research and application of the polyline pretensioned beams.3. The design of the test beams and the monitoring of construction. According the research purpose, the8test beams are designed and constructed, and the various mechanical properties parameter are monitored to provide the test data and analytical initial value for the later experimental study. Meanwhile, the prestressed loss is monitored and the practical formulas of prestressed loss due to anchorage deformation and retractation of steel strand is discussed clearly. The scientificity and practicability of the uniform calculating formulas of prestressing loss due to friction is confirmed too.4. The mechanical properties research of PPSCB under static loads. To research the mechanical properties of PPSCB and the influence of new bend component, the static load test of5PPSCB is designed and implemented. Combined the experimental study with theoretical analysis and numerical simulation, the mechanical properties of PPSCB, such as the ultimate loading capacity, deformation ability and ductility property, is analyzed clearly, as well as the load-deflection relationship, load-strain law, etc. The law of the crack formation and expansion is discussed and the failure pattern is observed carefully. Similarities and differences of the mechanical properties on the PPSCB with the new bend component and the traditional bend component are compared. The results show that the new bend component will significantly improve the ultimate deformation ability and ductility property of the PPSCB.5. The monitoring of local stress and the refined finite element analysis. Based on the peculiar mechanical properties of PPSCB and the general FEM software ANSYS, the refined FEA model of PPSCB is established by the sub-model technology which the bend component is simulated accurately. The local stress states at the bend component part is analyzed clearly and the similarities and differences on the PPSCB with the new bend component and the traditional bend component are compared. The simulation results verified the improvement of local stress states in PPSCB by the new bend component. Meanwhile, the local strain at the bend component part is monitored and analyzed based on self-designed local strain test component, and the test results is compared on the PPSCB with the new bend component and the traditional bend component. The test results confirmed the improvement of local stress states in PPSCB by the new bend component.6. The mechanical properties research of PPSCB based on fatigue test. The fatigue test of2PPSCB is designed and implemented to research the mechanical properties of PPSCB and the influence of new bend component. The effective laws of various mechanical properties by the fatigue load, such as the ultimate loading capacity, deformation ability and ductility property, is analyzed clearly, as well as the stain of steel strand, common reinforced, concrete on middle span and bend component part. Similarities and differences of the mechanical properties on the PPSCB with the new bend component and the traditional bend component are compared, and the results show that fatigue restraint ability of PPSCB will be improved significantly by he new bend component. It reconfirmed the improvement on the local stress states and overall mechanical properties of the PPSCB by the new bend component.更多还原