【作者】 白崇喜；

【导师】 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】 碳纤维增强聚合物(Carbon Fiber Reinforced Polymer,简称CFRP)筋具有轻质、高强、耐腐蚀等优点。以CFRP筋作为无粘结预应力筋,以环氧涂层钢筋或镀锌钢筋作为非预应力筋的无粘结CFRP筋部分预应力混凝土梁板可避免因预应力钢筋锈蚀而引起的结构物承载力下降和耐久性降低。由于CFRP筋受拉应力-应变关系呈线弹性,其弹性模量也不同于预应力钢筋,因此无粘结CFRP筋部分预应力混凝土梁板受弯性能有别于常规无粘结部分预应力钢筋混凝土梁板。尽管无粘结CFRP筋部分预应力混凝土梁板具有突出优点,但梁板中无粘结CFRP筋在使用阶段和承载能力极限状态下的应力增长规律尚不清楚,难以准确计算裂缝开展宽度、变形和承载力。尽管CFRP筋受拉应力-应变关系呈线弹性,但无粘结CFRP筋部分预应力混凝土连续梁板配有一定数量的非预应力钢筋,从加荷至破坏存在一定的塑性内力重分布过程,考察这类连续梁板弯矩调幅规律有一定现实意义。为此本文开展了如下几方面工作:(1)通过引入梁板的整体变形协调条件来解决平截面假定不再适用这一问题,采用弯矩-曲率分析法,编制了可用于无粘结CFRP筋部分预应力混凝土简支梁板和连续梁板全过程非线性分析的程序。以跨中控制截面受压边缘混凝土达到极限压应变作为简支梁板正截面承载能力极限状态的标志,以中支座控制截面受压边缘混凝土达到极限压应变作为连续梁板正截面承载能力极限状态的标志。以逐级增加简支梁板和连续梁板相应控制截面受压边缘混凝土压应变,直至达到极限压应变的方法实现了梁板的全过程分析。采用该程序计算出的无粘结CFRP筋等效折减系数、无粘结CFRP筋极限应力增量和弯矩调幅系数等计算结果,总体上与试验结果吻合良好,这表明用该计算程序对无粘结CFRP筋部分预应力混凝土简支梁板和连续梁板进行全过程分析是可靠的。(2)定义了使用阶段下无粘结CFRP筋应力增量与控制截面有粘结非预应力筋应力增量的比值为无粘结CFRP筋等效折减系数。参数分析表明,简支梁板和连续梁板中无粘结CFRP筋等效折减系数均随CFRP筋弹性模量、非预应力筋配筋指标、预应力筋相对位置的增加而增加,预应力筋配筋指标对简支梁板中无粘结CFRP筋等效折减系数的影响程度明显大于对连续梁板,荷载作用形式和跨高比对简支梁板和连续梁板中无粘结CFRP筋等效折减系数的影响规律并不相同,简支梁板中无粘结CFRP筋为直线布筋时的等效折减系数比为曲线布筋时的要大,连续梁板中无粘结CFRP筋等效折减系数随中支座控制截面综合配筋指标与跨中控制截面综合配筋指标的比值的增加而增加;对于简支梁板和连续梁板,T形截面的无粘结CFRP筋等效折减系数小于矩形截面。以关键参数为自变量,建立了简支梁板和连续梁板中无粘结CFRP筋等效折减系数的计算公式,为合理的计算使用阶段梁板的裂缝开展宽度和变形提供了依据。(3)基于无粘结CFRP筋等效折减系数,可将无粘结CFRP筋折算成一定数量的有粘结钢筋,它与原有有粘结纵向受拉钢筋共同构成等效纵向受拉钢筋。在无粘结CFRP筋部分预应力混凝土梁板刚度计算公式中引入等效纵向受拉钢筋配筋率,在用于计算无粘结CFRP筋部分预应力混凝土梁板裂缝宽度的纵向受拉钢筋等效应力计算公式中引入等效纵向受拉钢筋面积。基于相关试验结果,推导了表达方式统一的无粘结CFRP筋部分预应力混凝土梁板刚度及裂缝宽度计算公式,二公式所得的计算结果与试验结果吻合良好,可用于工程设计。(4)参数分析表明,简支梁板和连续梁板中无粘结CFRP筋极限应力增量均随非预应力筋配筋指标、预应力筋配筋指标的增加而减小,随CFRP筋弹性模量的增加而增加;荷载作用形式对简支梁板和连续梁板中无粘结CFRP筋极限应力增量的影响规律并不相同;连续梁板和跨中单点荷载作用下的简支梁板中无粘结CFRP筋极限应力增量随跨高比的增加而减小;连续梁板中无粘结CFRP筋极限应力增量随跨中控制截面综合配筋指标的增加而减小;对于简支梁板和连续梁板,T形截面的无粘结CFRP筋极限应力增量大于矩形截面。以关键参数为自变量,建立了简支梁板和连续梁板中无粘结CFRP筋极限应力增量的计算公式,为正确计算梁板的正截面受弯承载力提供了依据。(5)连续梁板中跨中控制截面和中支座控制截面相对刚度的变化引起了内力重分布,进而产生了弯矩调幅现象。以中支座控制截面的外载弯矩与张拉引起的次弯矩之和为弯矩调幅对象,参数分析表明,弯矩调幅系数随跨中控制截面综合配筋指标的增加而增加,随中支座控制截面综合配筋指标的增加而减小。荷载作用形式和跨高比对弯矩调幅系数也存在一定影响。以关键参数为自变量,建立了连续梁和连续板的弯矩调幅系数计算公式,为进行连续梁板的塑性设计提供了参考依据。更多还原

【Abstract】 Carbon fiber reinforced polymer (CFRP) tendons have apparent advantages such as lightweight, high strength, corrosive protection, and so on. The load bearing capacity and durability of structures decline caused by the corrosion of prestressing tendons could be effectively avoided by CFRP tendons as prestressing tendons instead of high strength steel bars, and by epoxy coated or galvanized steel bars as non-prestressing reinforcements. However, since stress-strain relationship of CFRP tendon is linear elastic, and its modulus of elasticity is different from that of prestressing steel, so, the flexural performance of concrete beams and slabs partially prestressed with unbonded CFRP tendons is different from that of ordinary unbonded partially prestressed concrete beams and slabs. Although this kind of beam and slab has outstanding advantages, the law of stress increment of unbonded CFRP tendons at service stage and flexural load bearing capacity limit state is unclear, so it is difficult to accurately calculate crack width, deflection and load bearing capacity. Thus, this kind of continuous beam and slab with non-prestressing reinforcements still have the plastic redistribution process of internal force, it has some practical significance to research on the law of moment modification. The following works are carried out:Using deformation compatibility condition to solve the problem of plane-section assumption being not applicable, moment-curvature analysis method are used to compile nonlinear full-range analysis programs of this kind of simply supported and continuous beam and slab. The strain of compressive extreme fiber of concrete in critical section of mid-span reaching the ultimate compressive strain is the symbol of the flexural load bearing capacity limit state of simply supported beams and slabs, and the strain of compressive extreme fiber of concrete in critical section of intermediate support reaching the ultimate compressive strain is the symbol of the flexural load bearing capacity limit state of continuous beams and slabs. Full-range analysis of beams and slabs can be achieved by gradually increasing the strain of compressive extreme fiber of concrete in corresponding critical sections of beams and slabs. The computing results of equivalent reduced coefficient of unbonded CFRP tendons (ERCUCT), ultimate stress increment of unbonded CFRP tendons (USIUCT) and moment modification coefficient are in good agreement with the test results as a whole, so it indicates that the programs are reliable. The ratio of stress increment of unbonded CFRP tendons to that of bonded non-prestessing reinforcements of critical section at service stage is defined as ERCUCT. Parametric analysis shows that ERCUCT in simply supported and continuous beams and slabs increases with increasing of modulus of elasticity of CFRP tendons, non-prestressing reinforcement index or relative position of unbonded CFRP tendons. The influence of prestressing reinforcement index on ERCUCT in simply supported beams and slabs is greater than that in continuous structures. The laws of influence of load types and the ratio of span to depth on ERCUCT in simply supported flexural members and that in continuous members are different. ERCUCT in simply supported members with tendons being straight line are bigger than being parabola. ERCUCT in continuous members increases with increasing of the ratio of combined reinforcement index of intermediate support section to that of mid-span. For simply supported and continuous members, ERCUCT in T-section is less than in rectangle section. Making key parameters as independent variable, the calculation formulas of ERCUCT in simply supported and continuous beams and slabs are proposed. They provide the basis for reasonably calculating crack width and stiffness of beams and slabs in service stage.Unbonded CFRP tendons can be reduced to be a certain number of bonded tendons based on ERCUCT. The reduced unbonded CFRP tendons and the original bonded longitudinal tensile reinforcements compose the equivalent longitudinal tensile reinforcements. The ratio of the equivalent longitudinal tensile reinforcements is introduced in the stiffness formula of this kind of beam and slab, and the equivalent area of total longitudinal tensile reinforcements is introduced in equivalent stress formula in crack width formula of this kind of beam and slab. Based on corresponding experiment results, the stiffness formula and crack width formula of this kind of beam and slab unified in expressions are derived. The results following these two formulas are in good agreement with test results, so they can be used in the design of civil engineering.Parametric analysis shows that USIUCT in simply supported and continuous beams and slabs reduces with increasing of non-prestressing reinforcement index and prestressing reinforcement index, and increases with increasing of modulus of elasticity of CFRP tendons. The laws of influence of load types on USIUCT in simply supported flexural members and that in continuous members are different. USIUCT in simply supported members under single concentrated load and in continuous members reduces with increasing of the ratio of span to depth. USIUCT in continuous members reduces with increasing of combined reinforcement index of mid-span section. For simply supported and continuous beams and slabs, USIUCT in T-section is bigger than in rectangle section. Making key parameters as independent variable, the calculation formulas of USIUCT in simply supported beams and slabs and continuous beams and slabs are proposed. They provide the basis for correctly calculating flexural load bearing capacity of beams and slabs.Redistribution of internal force is caused by relative stiffness change of critical section of intermediate support and mid-span in continuous beams and slabs, so moment modification exists. Make modification target as the sum of external load moment and secondary moment. Parametric analysis shows that moment modification coefficient increases with increasing of combined reinforcement index of mid-span section, and reduces with increasing of combined reinforcement index of intermediate support section. There are some influence of load types and the ratio of span to depth on moment modification coefficient. Making key parameters as independent variable, the calculation formulas of moment modification coefficient in continuous beams and continuous slabs are proposed. They provide references for plastic design of continuous beams and slabs.更多还原