体外预应力钢丝绳加固RC梁受剪性能的研究

发布时间：2018-06-22 16:14

本文选题：体外预应力 + 钢丝绳　；参考：《东北林业大学》2014年博士论文

【摘要】：随着我国经济和社会的快速发展,大量旧有桥梁的维修加固问题日益突出,在诸多桥梁加固方法中,体外预应力加固技术以其中断交通时间短、施工简便、经济高效、加固效果好等有点,被广泛用于旧桥加固施工中。而在既有桥梁中,梁端受剪破坏是一种常见的破坏形式,主要表现为主拉应力裂缝数量多,宽度超限,斜裂缝向跨中发展,严重影响结构的安全。造成受剪破坏的原因主要有抗剪承载力不足、材料性能退化、车辆超载等。目前,对抗剪能力加固,主要有粘贴钢板、粘贴高强复合材料、增大截面、体外预应力等加固方法。其中前三种均属于被动加固,只有体外预应力法属于主动加固,经常与抗弯加固配合作用,效果良好,但需设置转向块,构造复杂,施工繁琐。钢丝绳体外预应力加固,采用分散的钢丝绳进行加固,预应力分散布置,吨位小,锚固简便,不需转向装置,施工方便,是抗剪加固的一种新的尝试,为旧有混凝土桥梁及部分大跨径预应力混凝土桥梁普遍存在的斜裂缝加固提供新的途径,以改善桥梁受力状况、保证桥梁运营安全、延长桥梁的使用寿命,带来明显的直接及间接经济效益。本文的主要内容和研究结果如下： (1)体外预应力筋加固效果的研究模拟旧桥使用损伤状态,设计3片基准梁和23片加固梁进行体外预应力钢丝绳加固试验,试验梁截面尺寸为20cm×40cm,梁长为300cm,对加固梁的抗剪效果进行了系统的试验研究,试验内容包括体外筋加固作用对加固梁的极限承载力、裂缝变化、箍筋应变的影响,试验结果表明,体外预应力筋加固方法能够有效提高钢筋混凝土梁的抗剪能力,推迟梁体开裂,提高箍筋屈服荷载。 (2)试验梁设计参数对加固效果的影响按照试验梁的设计参数建立非线性有限元计算模型,对设计模型进行抗剪承载力计算,并加密设计参数弥补试验梁的不足,通过非线性有限元方法对待加固梁的混凝土强度等级、体内配箍率、纵向配筋率等设计参数以及体外参数包括钢丝绳间距、预加力大小、加固梁带载水平等因素对抗剪加固效果的影响进行了理论研究,揭示了体外钢丝绳抗剪加固的机理,总结了原梁参数和体外参数对加固效果的影响规律。计算结果表明,有限元计算结果与试验结果吻合良好；抗剪承载力随着配箍率、纵筋配筋率、混凝土标号、体外筋预加力的增大而明显提高,随着剪跨比、带载水平、体外筋间距的增大而减小 (3)加固梁抗剪承载能力计算方法的研究综合分析了国内外现有的抗剪承载力计算方法,在此基础上采用遗传-回归的方法,利用Matlab计算软件对试验数据和有限元计算数据进行优化分析,建立了基于桁架-拱模型的抗剪承载力计算模型,提出了体外钢丝绳、带载水平和混凝土损伤三个系数η1、η2、η3。并根据本课题抗剪加固试验数据检验了所提公式的可靠性。本文的研究成果为体外预应力加固钢筋混凝土梁的加固设计、施工方案、承载力计算提供了理论依据,可供参考使用。
[Abstract]:With the rapid development of our country's economy and society, the problem of maintenance and reinforcement of a large number of old bridges is becoming more and more prominent. In the reinforcement methods of many bridges, the technology of external prestressing reinforcement is a bit short of traffic time, simple construction, economical efficiency and good reinforcement effect. It is widely used in the old bridge reinforcement construction. In the existing bridge, Liang Duan Shear failure is a common form of failure, mainly manifested as the number of tensile stress cracks, the width of the limit, the slanting cracks developing to the midspan, which seriously affects the safety of the structure. The main reasons for the shear failure are the lack of shear capacity, the degradation of material properties, the overload of vehicles, etc. The strengthening methods such as high strength composite material, enlarging cross section and external prestressing force are added. The first three kinds are passive reinforcement, only the external prestressing method belongs to the active reinforcement, and the effect is good, but the steering block is set up, the structure is complicated and the construction is complicated. The steel wire rope is strengthened by external prestressing force, and the dispersed wire rope is used. It is a new attempt to reinforce the shear strength of the old concrete bridges and some large span prestressed concrete bridges. It provides a new way for the reinforcement of the old concrete bridges and some large span prestressed concrete bridges, in order to improve the stress condition of the bridge, ensure the safety of the bridge operation, and prolong the bridge operation. The service life of bridges brings obvious direct and indirect economic benefits. The main contents and results of this paper are as follows:
(1) study on the reinforcement effect of external prestressing tendons
To simulate the damage state of the old bridge, 3 datum beams and 23 reinforced beams are designed to reinforce the external prestressed steel wire rope. The test beam section size is 20cm x 40cm and the beam length is 300cm. The shear effect of the reinforced beam is systematically tested. The test contents include the ultimate bearing capacity of the reinforcement beam and the crack change. The experimental results show that the reinforcement method can effectively improve the shear ability of the reinforced concrete beams, postpone the cracking of the beam and increase the yield load of the stirrup.
(2) the influence of the design parameters of the test beam on the reinforcement effect
According to the design parameters of the test beam, the nonlinear finite element calculation model is established. The shear bearing capacity of the design model is calculated, and the design parameters are encrypted to make up the shortage of the test beam. The concrete strength grade of the reinforced beam is treated by the nonlinear finite element method, the design parameters such as the stirrup rate in the body, the longitudinal reinforcement ratio, and the parameters including the steel in vitro include steel. The effect of wire rope distance, preloading size, reinforcing beam carrying level and other factors on the effect of shear reinforcement is theoretically studied. The mechanism of shear reinforcement of steel wire rope in vitro is revealed, and the influence laws of the parameters of the original beam and the external parameters on the reinforcement effect are summarized. The calculation results show that the results of finite element calculation are in good agreement with the test results; The shear bearing capacity increases with the ratio of stirrup, the reinforcement ratio of the longitudinal reinforcement, the concrete mark and the preloading of the external tendons. With the shear span ratio, the load level and the increase of the distance between the external tendons, the shear strength decreases.
(3) calculation method for shear bearing capacity of reinforced beams
The calculation method of shear bearing capacity at home and abroad is synthetically analyzed. On this basis, the method of genetic regression is adopted, and the Matlab software is used to optimize the test data and the finite element calculation data. The calculation model of the shear bearing capacity based on the truss arch model is established, and the steel rope in vitro, the carrying level and the concrete are put forward. Three damage coefficients 1, 2 and 3. are tested, and the reliability of the formula is verified according to the test data.
The research results in this paper provide a theoretical basis for reinforcement design, construction plan and bearing capacity calculation of external prestressed reinforced concrete beams, which can be used for reference.
【学位授予单位】：东北林业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U445.72;U441

【参考文献】