【作者】 刘阳；

【导师】 吴智敏；

【作者基本信息】 大连理工大学 ， 结构工程， 2018， 硕士

【摘要】 众所周知,钢筋混凝土材料已广泛应用于现代建筑中,钢筋混凝土构件在使用过程中,都是带裂缝工作的。分析研究三点弯曲梁的断裂过程时,前人计算极限荷载的方法多以平截面假定为基础,建立力平衡方程求解,但是并不符合实际情况,在跨中裂缝位置处并不能满足平截面假定。本文在前人研究的基础上,对跨中预制裂缝的三点弯曲钢筋混凝土梁断裂过程进行分析,建立解析模型,计算断裂全过程。模型中考虑了钢筋与混凝土粘结滑移的影响,粘结滑移取用三线性本构关系,并以应力强度因子平衡方程作为控制方程,最后结合变形协调进行求解。Matlab编程计算可以得到荷载-裂缝口张开位移曲线,理论曲线与试验曲线吻合良好。分析裂缝-裂缝口张开位移曲线可知,跨中预制裂缝的三点弯曲钢筋混凝土梁断裂过程主要分为四个阶段,裂缝扩展荷载增加;增至第一峰值荷载,混凝土软化,荷载减小;裂缝继续扩展,荷载增大,直至第二峰值荷载;荷载缓慢减小。用本模型计算分析各种影响因素对峰值荷载的影响,有以下结论:在加载初期,梁的承载能力主要受混凝土性能影响,加载后期主要受钢筋性能影响;第一峰值荷载会随梁高、混凝土强度等级和钢筋半径的增大而增大,随初始缝高比、保护层厚度的增大而减小;第二峰值荷载会随梁高、钢筋半径的增大而增大,随保护层厚度的增大而减小。计算分析钢筋混凝土梁阻力曲线可知,起裂韧度对K_R阻力影响不大,加载初始阶段,阻力主要受粘聚力作用的影响,加载后期,阻力主要受钢筋作用的影响。更多还原

【Abstract】 As is known to all,reinforced concrete members are widely used in buildings nowadays.In the process of use,the members are all working with cracks.Taking the simplest three-point bending beam as an example,the previous calculation of ultimate load was based on the plane section assumption and solved the force balance equqtion.But the reality is that it doesn’t satisfy the plane section assumption in the mid-span.On the base of previous studies,this thesis focuses on the analysis of fracture process of reinforced concrete beam with precast crack in mid-span.Considering the bond-slip between steel bar and concrete and taking that the net stress intensity factor was zero as the contral equation,combining the deformation coordination,this paper establish a new theoretical calculation model.The local bond-slip model is triliner.It can get the P-CMOD curves to use Matlab to program calculation.And the theoretical curves fit well with the experimental curves.Acording to the P-CMOD curves,we can knew that there are four stages of beam fracture.Firstly,the load increase.Secondly,the load increase to the first peak and begin to decrease.Then,with the expansion of the crack,the load increase again and it will increase to the second peak load.Finally,the load decrease slowly.Use the theoretical calculation model in this paper to analyze the different influence of various factors on the peak load.At the beginning of loading,the bearing capacity of the beam is mainly affected by the performance of concrete.In the late loading period,the bearing capacity of the beam is mainly affected by the performance of reinforcement.The first peak load will increase by increasing the height of beam,the strength grade of concrete and the radius of reinforcement.And it will decrease by increasing the initial crack-height ratio and the cover depth.The second peak load will increase by increasing the height of beam and the radius of reinforcement,and decrease by increasing the cover depth.Calculate and analyze the crack growth resistance of reinforced concrete beams.K_inini has little effect on K_R.At the beginning of loading,the cohesive force has more effect on K_R.And in the late loading period,the steel tensile has more effect on K_R.更多还原