【作者】 蒋明；

【导师】 曾令宏；

【作者基本信息】 湖南大学 ， 结构工程， 2014， 硕士

【摘要】 高性能复合砂浆钢筋网(HPFL)加固混凝土结构是一种有效实用的加固技术,在修补火灾后RC梁时表现出了良好的性能。本文对采用HPFL加固受火RC梁二次受力抗弯力学性能进行了分析和研究,本文的主要研究内容如下:1.总结了国内外已有的混凝土和钢筋的热工参数和高温后的材料性能,包括强度、弹性模量、应力-应变关系曲线,以及高温后钢筋和混凝土之间的粘结强度。对比发现,混凝土的热工性能受温度影响很大,随着温度升高,强度和弹性模量下降厉害,当温度超过800℃后残余量不足20%,应力-应变关系曲线逐渐变缓,峰值点向下和向右移动;钢筋的热工性能受温度影响较混凝土小,当不超过800℃时,强度和弹性模量的折减系数一般不超过0.8,应力-应变曲线表现为斜率逐渐减小,钢筋的塑形变形增加,伸长率逐渐增大。这两类材料高温冷却后热工性能恢复不明显。钢筋和混凝土之间的粘结强度随着温度升高而降低。2.介绍了 ANSYS模拟HPFL加固受火RC梁的基本理论,对二维状态下的RC梁截面温度场进行了模拟,受火时间和截面尺寸对截面温度分布影响最大,并给出了不同尺寸在不同受火时间下的截面温度场分布。采用ANSYS建立了HPFL加固受火RC梁的三维模型,详述了材料特性和建模过程,并分析了有限元模拟受火RC梁加固后的抗弯承载能力和抗弯刚度。3.在已有试验的基础上,以截面应变保持线性分布的假定和内力平衡为基础建立力学方程,对高温后RC梁抗弯剩余承载力和HPFL加固受火RC梁二次受力抗弯承载力进行了分析与计算,分析了 RC梁的破坏形态,提出了钢筋网和复合砂浆滞后应变的计算公式以及RC梁抗弯承载力的计算公式,将计算结果与试验值进行比较,结果表明,理论值与试验值吻合较好。4.结合工程实例对受火RC梁剩余刚度和HPFL加固受火RC梁短期刚度进行了研究,表明HPFL加固技术除了提高构件承载力外,还可修补受火RC梁裂缝、修复外观,并可提高其抗弯刚度和改善开裂性能。同时采用刚度解析法对HPFL加固受火RC梁短期刚度进行了理论分析,提出了具体的计算公式,讨论了公式中变量的取值,计算结果表明加固后构件挠度满足规范要求。更多还原

【Abstract】 High performance ferrocement laminate(HPFL)is a practical method of structural reinforcement with good performance in repairing RC beams after fire.Analysis and tests on bending mechanical properties of reinforced concrete beams which are strengthened by HPFL after fire on second load are put forward.The main contents and conclusions are as follows:1.Thermal parameters and material properties after fire of concrete and steel at home and abroad were summarized,such as strength,elastic modulus,stress-strain curve and bonding strength between steel and concrete.The thermal properties of concrete were affected by temperature.As the temperature increasing,the strength and elastic modulus decreased much and the residual amount would less than 20%after temperature exceeded 800’C.At the same time,stress-strain curve gradually slowed and the peak point moved down and right.The temperature effect on steel was smaller than on concrete.Reduction coefficient of strength and elastic modulus was not over 0.8 when the temperature didn’t exceeded 800℃.Decreasing slope of steel stress-strain curve,increasing plastic deformation and elongation were also showed.These thermal properties were not recovered obviously after materials cooled.Bond strength between steel and concrete went down with increasing temperature.2.The basic theory about ANSYS simulating RC beams reinforced by HPFL after fire was introduced.Through simulating the two-dimensional section temperature field of RC beams,it found fire duration and sectional dimension were the most important influence factors and also presented pictures about section temperature field at different sectional dimension under different fire duration.Material properties were described in detail during establishing the three-dimensional model,and flexural bending capacity and stiffness were also showed at last.3.On the basis of existing experiments,stress plain section assumption and internal forces balance,mechanical equations were created.It put forward a series of theoretical analysis on residual flexural capacity of RC beams after fire and flexural strengthening of RC beams with ferrocement,such as failure modes.The formulas of initial strain of strengthened elements were obtained,as well as the formulas of flexural capacity.It gets a good matching between theoretical values and experimental values when the calculated results were compared with trial values.4.Combined with project,residual stiffness of RC beams after fire was researched,as well as RC beams reinforced by HPFL.The test shows HPFL reinforcement technique can repair cracks and appearance for RC beams,and also improve their bending stiffness and anti-cracking property.The theoretical analysis about short-term stiffness of RC beams after fire with ferrocemen was introduced through stiffness analytic method.It put forward formulas and discussed the variables in them.The result shows that deflection of RC beam meet norm requirement.更多还原