体外预应力混凝土简支梁-索组合单元受力性能研究

Study of mechanical behavior of external pre-stress concrete simply supported girder beam-cable composite element

基于伸缩斜腹杆施加体外预应力的新加固技术,以三腹杆体外预应力技术加固的简支梁为研究对象,应用积分原理和变形协调原理,建立了加固后简支梁的理论模型,推导了挠度与体外索内力增量关系的表达式以及荷载-挠度关系的表达式;通过数值模拟方法建立ABAQUS有限元模型,研究了索截面面积、索垂度、索初始内力等因素对加固后简支梁结构性能的影响规律;后又做了三组试验,对理论分析和数值模拟的研究结果进行了验证。研究表明：一般地,加固后梁的内力以及截面应力均发生重分布,随着体外索三影响因素（索截面面积、索垂度、索初始内力）设计值的提高,加固后简支梁的刚度、开裂荷载、极限荷载、结构延性均得到改善,比如在试验结果中开裂荷载提高24%~40%、极限荷载提高15%~42%、结构延性提高14%~40%。需要强调的是体外索设计参数的高初始内力、小截面、大垂度各工况下,结构发生脆性破坏的概率会增大,在加固设计时应当避免。理论结果、试验结果与模拟结果仅在弹性阶段吻合,而试验结果与模拟结果始终吻合,表明理论推导的体外索内力增量公式及弹性阶段的承载力公式可靠,能用于工程实践。

Based on the new reinforcement technology of external pre-stress with stretch tilted belly poles,the simply supported beam reinforced by the external pre-stress technology of the three titled belly poles was taken as the research object. The integral principle and deformation coordination principle were used to establish a model of reinforced simply supported beam. The expression of the relation between the deflection and the internal force increment of the extra-corporeal cable and the expression of the relationship between the load and deflection were deduced. The ABAQUS finite element model was established by numerical simulation to study the influence rule of the cross-sectional area,cable sag,initial cable internal force and other factors on the structure of reinforced simply supported beams. Then three groups of experiments were organized,and the theoretical analysis and numerical simulation results of the study were validated. The results show that the internal force and the cross-section stress of the beam are redistributed after the reinforcement. With the increase of the design value of the three external factors,the stiffness,cracking load,ultimate load and structural ductility of the simply supported beam are all improved. For example,in the test results,the cracking load increases by24% ~ 40%,the ultimate load increases by 15% ~ 42% and the structural ductility increases by 14% ~ 40%. Need to be emphasized is that under the high initial internal force of the design parameters of extra-corporeal cable,small section,big cable sag various conditions,the probability of brittle failure of the structure will increase,should be avoided in the reinforcement design. The theoretical results,experimental results and simulation results are in good agreement only in the elastic phase anastomosis,and the experimental results and simulation results always consistent with each other. It indicates that the theoretical derivation of the extra-cordial force increment formula and the elastic stage of the bearing capacity formula is reliable,which can be used in engineering practice.