【作者】 肖刚；

【导师】 欧进萍；

【作者基本信息】 哈尔滨工业大学 ， 土木工程， 2021， 硕士

【摘要】 钢筋混凝土内部钢筋锈蚀问题一直以来都较为严峻,对于桥梁结构,特别是沿海、跨海桥梁,由于所处位置的自然环境会加速钢筋锈蚀,因此面临着很多此类病害,处于潮差区的桥墩尤为明显。纤维增强复合材料(FRP)具有轻质高强和耐腐蚀等诸多优点,而且GFRP性价比高,于是国内外学者提出将GFRP筋或GFRP-钢复合筋替换钢筋并进行了相应的研究,包括材性、筋材与混凝土的粘结性能及混凝土构件的受弯和受压性能研究。经过多年的研究积累,目前材性和粘结性能已经基本明确,而对于梁和柱的承载力设计计算,仍需进一步完善,包括构件抗弯、轴压和偏压承载力。主要研究内容和成果如下:(1)根据GFRP筋和GFRP-钢复合筋的本构及现有规范要求确定出两者的设计强度分别为应变0.005对应下的应力和屈服应力;按照钢筋混凝土梁的设计原理得到了复合筋混凝土梁的相对界限受压区高度、最小配筋率及屈服和极限弯矩,与试验结果相比,屈服弯矩略微偏小,极限弯矩吻合较好;提出复合筋混凝土梁基于强度等效的截面设计计算方法。(2)通过已有试验数据得到了轴压矩形构件峰值荷载下的GFRP筋应变为混凝土峰值应变的1.2倍,混凝土强度为其轴心抗压强度的1.08倍;根据钢筋混凝土柱的稳定系数验证了切线模量理论的准确性,然后通过该理论得到了GFRP筋混凝土柱的稳定系数计算公式;为得到GFRP螺旋箍筋约束混凝土本构模型,提出了箍筋等效弹性模量这一新的变量,然后根据已有试验数据并结合Mander模型得到了约束混凝土峰值应力及应变计算公式;最后得到了GFRP筋混凝土矩形和圆形截面柱的轴压承载力计算公式,与试验结果吻合较好;同理对GFRP-钢复合筋混凝土柱进行了分析,得到了轴压承载力计算公式,与已有试验结果吻合较好。(3)结合平衡方程和曲率法,分析推导得到了GFRP筋混凝土矩形偏压柱的破坏形态判别式,判别结果与试验结果均相同,然后通过理论分析和已有试验数据的趋势构造并拟合了考虑相对偏心距、长细比和强度配筋率的矩形和圆形截面偏压柱的偏心距增大系数计算公式,另外根据钢筋混凝土柱的原理推导了考虑相对偏心距和长细比的偏心距增大系数简化计算公式,都与已有试验结果吻合很好;最后得到了GFRP筋混凝土矩形和圆形截面柱的偏压承载力设计计算方法,与试验结果吻合较好,为便于计算必要时可以忽略纵筋承受的压力;同理对GFRP-钢复合筋混凝土柱进行了分析,得到了偏压承载力设计计算方法,与已有试验结果吻合较好,为便于计算必要时可以忽略纵筋的二次刚度和采用等刚度方法进行设计。(4)基于本文的研究,对典型的混凝土简支梁桥进行了承载能力极限状态设计,包括GFRP-钢复合筋混凝土简支桥面梁、GFRP筋和复合筋混凝土桥墩,为将来的工程应用奠定了基础。更多还原

【Abstract】 The problem of steel corrosion in reinforced concrete has always been serious.For bridges,especially those coastal or sea-crossing,the natural environment will accelerate the corrosion of steel bars,so they are confronted with many such issue,especially for piers in tidal zone.Fiber reinforced Polymer(FRP)has many advantages,such as light,high strength and corrosion resistance.In addition,GFRP is cost-effective,and therefore,scholars at home and abroad proposed to replace steel bars with GFRP bars or GFRP-steel composite bars,and carried out corresponding research,including material properties,bond behavior between reinforcements and concrete,flexural and compressive behavior of concrete members.After years of research and accumulation,the material properties and bond behavior had been basically clear,but the design and calculation of bearing capacity of beams and columns still need to be further improved,including the flexural,axial and eccentric capacity of members.The main research contents and achievements were as follows:(1)According to the constitutive models of GFRP reinforcements and GFRP-steel composite reinforcements and the requirements of existing codes,the design strength of them was determined as the stress corresponding to the strain of0.005 and yield stress.According to the design principle of reinforced concrete beam,the balanced relative depth of compressive area,minimum reinforcement ratio,yield and ultimate bending moment of composite reinforced concrete beam s were obtained.Compared with the test results,the yield bending moment was slightly smaller and ultimate bending moment coincided well.Based on the strength equivalence,the design and calculation method of concrete beams reinforced with composite bars is proposed.(2)According to the existing test data,under the peak load of axial compression members,the strain of GFRP reinforcements was 1.2 times of the peak strain of concrete,and the strength of concrete was 1.08 times of its axial compressive strength.According to the stability coefficient of reinforced concrete columns,the accuracy of tangent modulus theory was verified,and then the stability coefficient formula of concrete columns reinforced with GFRP bars was obtained through the theory.In order to obtain the constitutive model of concrete confined by GFRP spiral stirrup,a new variable,equivalent elastic modulus of stirrup,was proposed,and then based on the existing test data and Mander model,the peak stress and strain formulas of confined concrete were obtained.Finally,the calculation formulas of the axial capacity of concrete rectangular and circular section columns reinforced with GFRP bars were obtained,which were in good agreement with the test results.Similarly,for concrete columns reinforced with GFRP-steel composite bars,the calculation formulas of axial capacity was obtained,which were in good agreement with the existing test results.(3)Based on the equilibrium equation and curvature method,the discriminant of failure modes of concrete columns reinforced with GFRP bars under eccentric compression was analyzed and derived,the results of which were the same as the experimental ones.Then,the eccentricity increase factors,considering relative eccentricity,slenderness ratio and strength reinforcement ratio,of rectangular and circular eccentric columns were constructed and fitted by theoretical analysis and the trend of existing test data.In addition,according to the principle of reinforced concrete column,the simplified calculation formula of eccentricity increase factor,considering relative eccentricity and slenderness ratio,was derived,which was in good agreement with the existing test results.Finally,the design and calculation methods of eccentric capacity of concrete rectangular and circular section columns reinforced with GFRP bars were obtained,which were in good agreement with the test results,and in order to facilitate the calculation,the bearing capacity provided with GFRP reinforcements could be ignored when necessary.In the same way,concrete columns reinforced with GFRP-steel composite bars were analyzed,and the design and calculation methods of eccentric capacity were obtained,which were in good agreement with the existing test results,and in order to facilitate the calculation,it was necessary to ignore the secondary stiffness of longitudinal reinforcement and adopt the equal stiffness method for design.(4)Based on the research of this paper,the design of ultimate limit state of typical concrete simply-supported beam bridge was carried out,including concrete simply-supported beams reinforced with GFRP-steel composite bars,concrete piers reinforced with GFRP or GFRP-steel composite bars,which laid the foundation for future engineering application.更多还原