【作者】 王钧；

【导师】 沈世钊； 郑文忠；

【作者基本信息】 哈尔滨工业大学 ， 结构工程， 2010， 博士

【摘要】 内置H型钢预应力混凝土组合梁是指在内置H型钢混凝土组合梁的H型钢上、下翼缘间合理布置并张拉预应力筋,产生预定量值的等效荷载,使得控制截面实际受到的净荷载效应明显减小的新型梁。这种新型梁与普通内置H型钢混凝土梁相比,当作用荷载和跨度相同时,截面尺寸可明显减小;当作用荷载和截面尺寸相同时,跨越的跨度可明显增大。这类梁可用于新建工程,也可用于套建增层工程。因此,对这种梁开展研究具有一定的现实意义。对普通内置型钢混凝土组合梁的刚度、裂缝及承载力的研究是有报道的,且也有工程建设标准。但未见有预应力及预应力筋(束)对这类梁裂缝分布及开展影响的报道,也未见预应力及预应力筋对这类梁刚度影响的报道。这类梁的受力性能也应有其自身特点。为此,设计制作了以内置H型钢、非预应力筋、预应力度为变量的5根内置H型钢预应力混凝土简支组合梁,其型钢含钢率为6.65%~7.24%之间,并完成了对其三分点加荷试验,考察了从开始加荷至破坏的全过程。试验结果表明,试验梁开裂对荷载—跨中变形关系曲线的走向影响不大,H型钢受拉翼缘或纵向受拉非预应力钢筋屈服点成为曲线的转折点,从加载到达到试验梁的正截面承载能力极限状态,荷载—跨中变形关系曲线呈双折线特征。试验梁破坏后仍具有一定的刚度和承载力,卸载后残余裂缝宽度和残余变形相对较小,这类梁具有良好的变形恢复能力。钢连续梁可进行充分的内力重分布,普通钢筋混凝土连续梁的弯矩调幅系数有表可查,预应力混凝土连续梁弯矩调幅的计算方法也有报道。对内置H型钢预应力混凝土连续梁,我们采用以支座控制截面达到承载能力极限状态时该截面荷载作用下弹性弯矩计算值与内置H型钢实际承担弯矩的差值为调幅对象,以塑性铰的塑性转角与梁截面有效高度比值(称为相对塑性转角)为自变量求解弯矩调幅系数的思路。设计制作了3根内置H型钢预应力混凝土连续梁,这三个试件以支座控制截面预应力度、支座控制截面相对受压区高度和跨中控制截面受弯承载力为关键参数。完成了这三个试件每跨跨中单点集中加荷试验,考察了从加荷到破坏的全过程。获得了这类连续梁等效塑性铰长度的计算公式,等效塑性铰长度随预应力度的增大而减小。应用弯矩—曲率非线性全过程分析方法,获得了9根模拟连续梁的极限荷载,丰富了样本空间。基于模型的试验结果和对模拟梁的非线性分析结果,建立了以支座控制截面相对塑性转角为自变量的弯矩调幅系数计算公式。提出了包括材料选择,截面选择,内力计算,型钢、预应力筋、非预应力筋选配,斜截面计算,变形验算及裂缝验算和施工方法等内容的内置H型钢预应力混凝土连续梁的设计建议。更多还原

【Abstract】 Prestressed concrete composite beam with encased H-steel (PCCBEH)refers to a kind of new beam, in which the presrtressing steel is rationally arranged and tensioned between the top flange and the bottom flange of H-steel, and the scheduled equivalent load is formed which can reduced the net load effect acted on the critical section. Compared with the common encased H-steel concrete composite beam, the dimension of the cross section of PCCBEH can be distinctly decreased with the same load and the same span; the span can be distinctly increased with the same load and the same cross section. This beam can be used in the new project, and it can also be used in the out-jacketing frame project for adding stories. So, it is of practical significance to do some research on this PCCBEH.For the common encased steel concrete composite beam, the research on the stiffness, the crack and the carrying capacity had been reported, and the construction standard can be used to guide the design and construction. But there is no report on the influence on of prestress and prestressing steel on the distribution of crack as well as their influence on stiffness. PCCBEH has its own characteristic on the mechanical performance. 5 PCCBEHs were designed and fabricated with the encased H-steel, non-prestressing steel and the prestressing degree as the variable and the steel ratio is 6.65%~7.24%. These 5 beams were tested with the two-point load test. The whole process from the beginning of loading to failure was investigated. Test results indicated: cracking of the beam affected little on the curve of load-deflection at the midspan. The yield point of the tensile flange of the H-steel and the tensile longitudinal non-prestressing steel bar become the turning point of the curve. Form the beginning of loading to reaching the strength ultimate limit state of the beam, the curve of load-deflection at the midspan was double broken line. The beam still had a certain stiffness and carrying capacity when it failed. The residual crack width and the residual deflection was relative small after unloading. PCCBEH had good ability on recovery of deflection.The sufficient redistribution of plastic internal force can occur in continuous steel beams, and the moment modification coefficient of the common concrete continuous beam has been listed in literature. There already have some reports on the calculation method of moment modification for prestressed concrete continuous beams. For PCCBEH, the idea for calculating the moment modification coefficient is put forward: the object can be modified is the deference between the elastic calculated moment caused by the load and the moment subjected by H-steel at the critical section at the intermediate support when reaching the ultimate limit state. The variable is the relative plastic rotation that is the ratio of rotation of the plastic hinge to the effective depth of the section. 3 continuous PCCBEHs were designed and fabricated with 3 key factors. They were: the prestressing degree of the critical section at the intermediate support, the relative depth of the critical section at the intermediate support and the carrying capacity of the critical section at the midspan. 3 beams were test with a single load on each midspan. The whole process from the beginning of loading to failure was investigated. The calculation formula for the length of the equivalent plastic hinge was got. It decreased with the increase of the prestressing degree. The ultimate load of 9 simulated continuous beams was obtained by using the moment-curvature nonlinear whole process analysis method, so the sample space is enriched. Based on the model test results and the simulated nonlinear analysis results, the calculation formula of the moment modification coefficient is established with the relative plastic rotation of the critical section at the intermediate support is the variable.Design proposals are presented for PCCBEH including selection of materials, selection of sections, calculation of internal force, selection and configuration of steel, prestressing steel, non-prestressing steel bar, calculation of the oblique section, control and check of crack, control and check of deflection, construction method and so on.更多还原