预应力活性粉末混凝土叠合梁设计关键技术试验研究

Good tensile property, high elastic modulus, high durability of a new kind of Ultra High Performance Reactive Powder Concrete were ultilized to build the composite beams in this program with reinforced concrete or prestress concrete so that the beams would have such advantages as smaller size of cross section, lower height, higher crack resistance ability, better protect from corrosion of steels, higher durability of the structure, a increase of stiffness, a decrease of deformation. Decrease of deformation became more critical especially for post creep deformation so that it would improve the performance of the structure and reduce maintenance. So, the promotion of the use of the reactive powder concrete in bridge construction was of great significance..In this program, shearing slip test for the joint section of the two different materials, based on the former study by our group, was designed in order to find out the constitutive relationship of the shear slide behavior and bearing capacity of the structure in different load case. Flexural-shear test was also designed in order to find out the mechanism and the manner of the flexural-shear failure, the changing relationship between the stiffness and the strain (the stress). Further on, a comprehensive research on the theoretical analysis and the nonlinear finite element analysis was conducted to find out the law of the main influence factors of the composite beams. Finally, basing on the comparison among the datum collected from the measured value of the experiment and the theoretical analysis, practical calculation method and formula of the stress, stiffness, flexural and shearing capacity of the cross section would be given for laying a foundation for the application in engineering design in the future.

本项目利用新型超高性能活性粉末混凝土的高抗拉性能、高弹模、高耐久性，与混凝土、钢筋（或预应力钢筋）组合成叠合梁，使梁体具有减小截面尺寸、降低梁的高度、提高截面抗裂性、保护钢筋免遭锈蚀、增加结构的耐久性、增加截面刚度、减小变形，特别是对于减小后期徐变引起的梁体变形更为明显，达到改善结构使用性能，减少维护等优点。因此，对活性粉末混凝土在桥梁中的推广应用具有重要的意义。.本项目在本课题组对活性粉末混凝土前期研究的基础上，对两种材料的结合面进行剪切滑移试验，建立不同竖向压力作用下，剪力与滑移的关系，及其承载能力；进行模型梁的弯剪试验，确定其抗弯、抗剪破坏机理和形态，截面刚度、应变（应力）变化；进一步进行系统的理论和非线性有限元计算分析，了解对叠合梁主要影响因素的影响规律。最后通过模型试验梁的实测值与理论计算值的对比分析，提出截面应力、刚度、抗弯、抗剪承载力算方法及计算公式，为工程设计应用奠定基础。

本项目将活性粉末混凝土与普通进行结合形成一种新型叠合梁，该梁将高性能活性粉末混凝土放置在梁的下部，将普通混凝土放置在梁的上部。该新型叠合梁与普通混凝土梁和预应力混凝土梁相比具有以下优点：首先，能够充分利用活性粉末混凝土的高抗拉性能、高弹模、高耐久性等优异性能，更有效的保护梁底的纵向钢筋，从而大大提高梁的使用寿命，减少梁结构的维修成本；其二，能够充分利用普通混凝土的高抗压性能和价格低廉的特点，从而在发挥活性粉末混凝土高性能的同时降低了梁结构的造价；其三，能够有效减小梁结构的截面尺寸、降低梁结构的高度、提高抗裂强度（耐久性）、提高刚度、减小梁结构自身的收缩变形等优点，对于混凝土大跨度桥梁的设计有重要意义；此外，还能够充分利用活性粉末混凝土和普通混凝土同为水泥基材料之间的粘结性能，提高叠合面之间的粘结强度。该新型叠合梁结构的研究对于高性能活性粉末混凝土在桥梁结构中的推广应用有重要意义。.本项目为充分研究活性粉末混凝土与普通混凝土叠合梁的力学性能，先后进行了四方面的试验及理论研究，第一：通过剪切试验和理论方法研究了活性粉末混凝土与普通混凝土叠合面之间的粘结性能，确定了叠合面抗剪滑移关系；第二：设计并制作了钢筋活性粉末混凝土与普通混凝土叠合梁模型，进行了力学性能试验，研究了叠合梁荷载位移关系及其裂缝形态、破坏机理、截面刚度等性能，为研究预应力叠合梁奠定了基础；第三：设计并制造了预应力活性粉末混凝土和普通混凝土叠合梁，进行了预应力叠合模型梁抗弯试验，研究了其抗弯力学性能；第四，进行了预应力叠合梁的的疲劳试验，初步探索其疲劳性能，为全面和进一步研究叠合梁的力学性能及适用性做了有益探索。最后以试验数据和理论为基础，提出模型梁截面应力、刚度、抗弯、抗剪承载力计算方法及计算公式，为工程设计应用奠定基础。