【作者】 曾翔；

【导师】 许斌；

【作者基本信息】 湖南大学 ， 结构工程， 2014， 博士

【摘要】 地震和冲击荷载等强动力荷载作用造成钢筋混凝土结构破坏,从而导致大量的人员伤亡和巨大的财产损失。钢筋混凝土结构在地震和冲击荷载等强动力荷载作用下存在的应变率效应使其动力性能与静态性能存在较大差异。在冲击荷载下受复杂的应力波传播和惯性效应的影响,结构行为更加复杂。在地震作用的应变率范围内,钢筋混凝土柱的轴向受压动力行为及考虑箍筋约束效应和应变率效应的钢筋混凝土柱的动力行为的试验资料和数值分析研究十分缺乏。在混凝土结构抗冲击性能研究方面,少见无腹筋梁和深梁的抗冲击行为研究的文献,配箍筋钢筋混凝土梁的在冲击荷载下的剪切行为的试验研究数量仍十分有限,对冲击过程中梁的加速度响应及其分布变化未进行详细探讨,影响梁的冲击响应的相关因素(比如配箍率、剪跨比等)的探讨还不够全面。基于此,本文采用试验和数值分析研究相结合的方法,在地震作用的应变率范围内对钢筋混凝土柱的动力行为以及冲击荷载下钢筋混凝土梁和深梁的动力行为进行研究。本文的主要研究工作如下：(1)开展了两种不同长细比的钢筋混凝土长柱快速轴心受压加载试验和动力有限元模拟研究,分析了快速加载对不同长细比的柱动态承载力及其对应的变形的影响,阐述了不同长细比的轴心受压柱动态承载力提高的机制,即快速加载下应变率效应和惯性效应在不同长细比下的影响规律。(2)提出了同时考虑应变率效应和箍筋约束效应的混凝土塑性模型等效单轴受压本构模型,并基于此利用ABAQUS建立了分析约束钢筋混凝土轴压短柱在快速加载下动力行为的有限元模型。算例分析表明,模拟结果与试验结果吻合良好。通过有限元模型参数分析,得到了配置箍筋构形、箍筋间距和纵筋配筋率对约束钢筋混凝土短柱在地震作用应变率范围内的动态力学性能的影响规律。(3)开展了简支无腹筋钢筋混凝土梁的落锤冲击试验研究和有限元分析。通过试验研究重点关注冲击锤重、冲击速度和冲击能量对梁在冲击荷载下梁的破坏过程、典型破坏模式和剪切破坏面的影响,并研究了冲击力、钢筋与混凝土应变时程特点。基于应变数据,推断出梁在冲击过程中的弯矩分布及惯性力分布特点,并在此基础上对单自由度等效模型进行了讨论。采用LS-DYNA建立了分析无腹筋钢筋混凝土梁抗冲击行为的有限元模型,分析了剪跨比、梁顶是否配置纵筋对无腹筋梁的冲击响应的影响规律。(4)开展了简支配箍钢筋混凝土梁的落锤冲击试验和有限元模拟。试验研究了不同冲击速度、冲击能量及二次冲击效应对冲击荷载下的梁抗剪行为的影响,得到了不同参数影响下梁的破坏过程、破坏模式特点,详细分析了冲击响应(包括冲击力、支座反力和位移时程曲线以及冲击力-位移曲线和支座反力-位移曲线)的特征。基于实测加速度响应,分析了冲击过程中梁的惯性力分布特点,进而讨论了不同冲击荷载作用下梁斜裂缝开裂模式差异的机理和梁的抗冲击承载力评估方法。采用LS-DYNA建立了分析冲击荷载作用下配箍钢筋混凝土梁动力行为的有限元模型,并分析了配箍率对钢筋混凝土梁的冲击响应的影响规律。(5)首次开展了简支钢筋混凝土深梁的落锤冲击试验研究和有限元分析。通过试验研究了两种静载破坏特性的钢筋混凝土深梁在不同冲击速度及二次冲击效应下的动态行为,针对破坏过程和破坏形态、冲击力、跨中位移响应的特点进行了分析,并讨论了深梁的抗冲击承载力的评估方法。采用LS-DYNA建立了分析深梁抗冲击行为的有限元模型,并用试验数据进行了验证,进而研究了配箍率对钢筋混凝土深梁在冲击荷载下的动态响应的影响规律。更多还原

【Abstract】 Strong dynamic loads such as earthquake action and impact loading destroy the reinforced concrete (RC) structures, and then lead to a great of casualties and economic loss. Under the strong dynamic loads, the behaviors of RC structures are very different from the behaviors under static load because the strain rate effect of materials is induced in RC structures. Under impact loadings, stress wave propagation and inertia effect exist in the structures and make the behavior more complicated. By now, the experimental and numerical studies on the dynamic behavior of RC columns subjected to rapid concentric compressive loadings and the dynamic behavior of RC columns considering the strain rate effect and the confined effect of stirrups together within the range of strain rate corresponding to earthquake action are very limited. For the studies on the behavior of RC structures subjected to impact loadings, little literature reports the studies on the impact-resistant behavior of RC beam without stirrups, deep RC beam and the RC beam with stirrups in shear failure. Little study investigates the response and distribution of acceleration of the RC beam in details and all-around discussion on the influence parameters such as shear span ratio and stirrup ratio is not conducted. So in this study, the dynamic behaviors of RC columns subjected to rapid loading with the strain rate corresponding to earthquake action and the impact-resistant behaviors of RC beams and deep RC beams are investigated experimentally and numerically. The main contents of this study are summarized as follows:(1) Experimental study and finite element analysis of slender RC columns with two slenderness ratios under concentric rapid loading are carried out. The effects of rapid loading on the axial compressive load-carrying capacity and the corresponding axial deformation of columns with different slenderness ratios are analyzed according to the experimental and numerical results. Finally, the mechanism for dynamic increase in the strength of the slender RC columns under axial rapid loading is investigated, namely the effect laws of strain rate and inertia effect on the behavior of columns with different ratios.(2) An equivalent stress-strain relationship of concrete considering both strain rate sensitivity of concrete materials and confinement effect of stirrups is proposed for the concrete plastic constitutive model in ABAQUS and a FEA model is established to analyze the dynamic behaviour of laterally confined short columns under rapid loadings. With the validation of relative examples, the calculated results using the FEA model are on the whole in good agreement with the experimental results. Based on the proposed analysis model, the influence laws of the following three parameters including the configuration, spacing of stirrups and the ratio of longitudinal reinforcement on the dynamic behaviour of laterally confined short columns considering different strain rate corresponding to earthquake action is studied.(3) Falling-weight impact tests and finite element analysis of RC beams without shear-resistant bars are carried out. In the tests, main attentions are paid to the effect of parameters including the weight of impact mass, impact velocity and impact energy on the failure procedure, crack patterns, the characteristics of shear failure surface, also the characteristics of the time histories of impact force and the time histories of strain of concrete and steel rebar. From the data of strains measured, the distribution characteristic of moments and inertia forces along the beams under impact loading are obtained and then discussion on the single degree of freedom system model for analyzing the behaviors of RC beams subjected to impact load is made. For further study, a FEA model for impact analysis of RC beam without shear rebar is established using LS-DYNA and is validated by the test results. Based on the validated FEA model, the effect of parameters referred to shear span ratio, symmetrical reinforcement and impact velocity is analyzed.(4) Falling-weight impact tests and finite element analysis on a group of RC beams with stirrups are carried out. In the experiment, the effects of impact velocity, impact energy and the impact times on the shear resistant behavior of RC beams under impact loading are investigated. The crack initiation, propagation and the failure patterns, the characteristics of time histories of impact force, reaction forces and displacement, impact force versus displacement curves, reaction force versus displacement curves are described and analyzed in details. Based on the measured response of acceleration at different positions along the length of the beams, the distribution and effect of the inertia force are analyzed, and further analysis is conducted on the mechanism of the diagonal crack forming under different impact level and discussion on evaluation methods of impact-resistant capacity of RC beams is made. Finally, A FEA model for impact analysis of RC beam is established using LS-DYNA and the effect of the stirrup ratio on the impact response of RC beam is investigated.(5) Falling-weight impact tests on simply supported deep RC beams are carried out for the first time and the effects of impact velocity and impact times on two groups of RC deep beams with different static behavior are investigated. The crack initiation, propagation and the failure process, the crack patterns, the characteristics of time histories of impact force and displacement and impact force versus displacement curves are analyzed in details. The evaluation methods of the impact-resistant capacity of RC deep beams under impact loadings are discussed. To investigate the effect of more parameters, a FEA model is established using LS-DYNA to predict the behavior of deep RC beam under impact loading and is validated by the test data. Then the effect laws of stirrup ratio on the impact response of deep RC beams are investigated.更多还原