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为了准确评估带裂缝工作混凝土结构的耐久性能，针对氯离子在带裂缝混凝土中的扩散过程进行研究。提出了无损制备裂缝的方法，可高效易行地在混凝土侧面及内部产生裂缝。对带裂缝的水泥砂浆试件进行氯盐溶液浸泡试验，深入研究了单缝和双缝试件中氯离子的扩散作用，修正了氯离子的扩散系数，并对带裂缝混凝土的氯离子扩散过程进行了数值模拟。研究结果表明：氯离子会沿裂缝发展方向及垂直于裂缝发展方向扩散，随着水灰比的减小，砂浆试件的抗氯离子扩散性能明显提高，在一定范围内，当裂缝间距增大，双缝间的氯离子扩散交互影响作用明显减小，ANSYS软件的模拟结果与试验数据吻合良好。 相似文献
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剪力连接件是保证GFRP混凝土组合梁/板中两种不同材料共同工作的重要构造,设计了矩形肋和T形肋两类GFRP肋式剪力连接件,进行了3组共8个GFRP肋式剪力连接件的推出试验,包括：矩形肋开孔、T形肋开孔、T形肋不开孔3组GFRP肋式剪力连接件,得到了其破坏形态、极限承载力、荷载滑移曲线及荷载应变变化规律,重点研究肋内开孔及肋的截面形式对GFRP肋式剪力连接件受力性能的影响。试验结果表明：GFRP肋式剪力连接件的破坏形态均为混凝土劈裂破坏;对比矩形肋开孔试件,T形肋开孔试件强度高、延性好;对比T形肋不开孔试件,T形肋开孔试件强度与延性均能提高。基于试验结果,建立了考虑肋内开孔及肋截面形式影响的GFRP肋式剪力连接件极限承载力计算公式,拟合得到了GFRP肋式剪力连接件的荷载滑移曲线上升段的理论模型,建立了其抗剪刚度计算公式。 相似文献
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为了研究钢箱-砼组合结构中PBH剪力键在反复荷载作用下的疲劳性能,设计制作了PBH剪力键试验模型,进行了24万次疲劳推出试验。在疲劳破坏形态和试验滑移及应变数据分析的基础上,利用数值工具开展肋板开孔孔径、穿入钢筋直径、混凝土强度3个参数的PBH剪力键疲劳寿命影响因素分析。研究表明：PBH剪力键的疲劳破坏形态与静载破坏相似,表观表现为混凝土面多处斜向劈裂裂缝、内部榫孔混凝土压碎、穿入钢筋局部屈服;疲劳破坏演化过程分为疲劳损伤开始、发展、破坏3个阶段,其中疲劳发展阶段占整个疲劳阶段的91.7%,结构刚度在疲劳损伤开始和发展阶段退化较慢,在疲劳破坏阶段退化较快;肋板开孔孔径、穿入钢筋直径、混凝土强度3个参数对PBH剪力键疲劳寿命影响均有明显影响,其中穿入钢筋直径对疲劳寿命的影响尤为突出。 相似文献
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为了从材料细观非均质角度揭示混凝土强度尺寸效应机理,建立了混凝土细观单元等效非均质力学模型,开展了立方体抗拉、抗压强度尺寸效应细观数值模拟研究。研究结果表明：混凝土强度尺寸效应根源于材料细观非均质性,随着模型尺寸的增加,混凝土材料细观单元弹性模量变异系数增大,材料细观非均质性增强,大尺寸模型内部存在更多的低强度单元或缺陷,导致混凝土立方体抗拉、抗压强度降低,极限应变减小,脆性增大;混凝土损伤破坏由少量集中区域,发散扩展形成多条非贯通的裂纹带;数值模拟结果与尺寸效应实验数据相吻合。 相似文献
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进行了大跨径预应力混凝土刚构桥腹板开裂机理研究,基于弹性力学平面问题分析方法,推导了集中荷载作用下的板件应力函数表达式,绘制了不同受压边长与集中荷载长度比（d/a）下的横向应力曲线,拟合了集中荷载作用下构件的横向应力求解函数,构造了混凝土刚构桥腹板在预应力集中荷载作用下等效压力矩形的选取方法,并基于平面应力的表达式提出了在三维情况下沿预应力轴线的横向应力计算方法。通过建立某预应力混凝土刚构桥0~3#段实体有限元模型,分析施工过程中刚构桥混凝土腹板在不同等级预应力作用下的开裂情况。结果显示：有限元裂缝模拟与实桥腹板开裂范围一致,有限元应力分析结果下限值与推导的横向应力求解函数计算结果接近,变化趋势一致,印证了横向应力函数求解方法的正确性。 相似文献
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为了防止联肢剪力墙中小跨高比连梁发生低延性剪切破坏,在单连梁中部设置一条通缝,形成开缝连梁改善其抗震性能。试验完成了3个小跨高比带板开缝连梁的低周反复加载,通过与其他配筋形式连梁对比,分析了开缝连梁的破坏形态、滞回特征、承载力退化、刚度退化、延性、耗能等一系列抗震性能。利用软件ABAQUS对试件滞回曲线的骨架曲线进行模拟,并将模拟结果和试验结果相对比。结果表明,小跨高比开缝连梁具有良好的承载能力及变形能力,施工较为方便且经济,能有效防止小跨高比连梁延性较差的剪切破坏,具有较好的抗震性能,可在实际工程中推广。 相似文献
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为准确分析单箱双室组合箱梁的剪力滞效应，考虑钢混凝土的界面滑移效应和钢腹板的剪切变形，针对顶底板和翼板定义不同的剪力滞翘曲位移函数，基于能量变分法推导出单箱双室组合箱梁剪滞效应的控制微分方程及其闭合解。以单箱双室组合箱梁算例为基础，利用该方法分析其剪力滞效应的规律，结果表明：在同时考虑滑移和剪切变形时，组合箱梁的挠度比初等梁理论解大，且其挠度随界面滑移刚度的增大而减小；组合箱梁在均布荷载作用下，滑移量与荷载值近似成正比关系；在相同条件下，钢箱梁底板的剪力滞效应较混凝土顶板显著。 相似文献
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页岩烧结保温砌块砌体基本力学性能试验研究 总被引：1，自引：0，他引：1
通过对页岩烧结保温砌块砌体轴心抗压、沿通缝抗剪、剪压复合抗剪性能试验研究,分析其破坏特征和破坏机理。试验结果表明:页岩烧结保温砌块砌体受压破坏时,在竖向灰缝附近形成主裂缝,接近极限荷载时砌体出现表皮剥落现象;沿通缝抗剪破坏模式主要为单剪破坏,脆性明显;剪压破坏有剪磨、剪压和斜压3种类型;实测轴心抗压强度平均值高于规范值,沿通缝抗剪强度、复合抗剪强度平均值低于计算值,并分别给出砌体轴心抗压强度平均值、抗剪、剪压复合受力抗剪强度平均值建议公式;剪压复合抗剪强度随着压应力的增大而增大;建立了页岩烧结保温砌块砌体受压应力应变关系表达式;给出该类砌块的弹性模量和泊松比的建议值。 相似文献
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宁夏引黄灌区低洼地区地下水位较高,导致土壤出现严重盐渍化现象,而添加土壤改良剂是解决土壤盐渍化问题的一种有效途径。为研究不同改良剂对宁夏引黄灌区低洼区域盐渍化土壤改良效果,在位于银北地区南梁农场的一块地势低洼的盐渍化耕地,选用不同改良剂进行改良试验。设置对照组、单一施用糠醛渣、单一施用脱硫石膏、复合施用糠醛渣+脱硫石膏及不同用量,共10个处理组,将研究区域分成若干小区,每个小区施用不同处理组改良剂,并种植油葵作物,比较分析不同处理组下油葵生长指标和产量及油葵收获后土壤全盐量、各盐分离子、pH,探究该区域盐渍化土壤的最优改良方案。结果表明,在表层土壤,施用糠醛渣+脱硫石膏复合改良剂后全盐量下降较为明显,低、中、高3种不同施用量下与对照组相比盐分含量降低了10.44%、10.14%、0.88%,单一施加脱硫石膏和糠醛渣一种改良剂盐分降低不明显。总体而言,施用糠醛渣+脱硫石膏复合改良剂对降低土壤全盐量、钠吸附比和提高作物产量效果较为显著,糠醛渣与脱硫石膏的最佳配合比为7:3,最佳施用量为17960 kg/hm2。 相似文献
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Based on concepts of mechanics, a mechanical model of novel type of steel plate composite shear wall is presented. The novel type of structure is formed by steel plate shear wall and T-shaped solid-web composite columns. Flexural stiffness of steel beams, lateral stiffness of the T-shaped solid-web composite columns, shear stiffness of steel plate composite shear wall and shear stiffness of beam-column connection are taken into account in the mechanical model. And the equivalent damping between steel plate and boundary is considered. Based on the deformation features of structures and the calculation hypothesis, the lateral stiffness model and the energy dissipation model of structures are developed. Meanwhile, the calculation equations of elastic ultimate and plastic ultimate of shear strength of structures are set up. The theoretical analysis results inosculate better with the results of experiment. The comparison between the result calculated from the formula and the experimental result shows that the calculation precision is high enough to meet the demand of theoretical analysis. The difference, including equivalent model, stress states, manufacturing defect and installation error, between the formula and the experiment has been further discussed. 相似文献
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The accurate calculation of the deformation capacity of structures is very important to performance-based seismic design, which satisfies the explicit deformation demands. The method to evaluate drift capacity of fiber reinforced polymer (FRP) confined reinforced concrete circular columns under simulated seismic loading is focused. Firstly, the moment-curvature relationship of FRP confined sections of reinforced concrete (RC) circular columns is simulated by numerical analysis. It is found that the calculated ultimate curvature is significantly less than the test result, and the difference is controlled by the axial load ratio of the tested columns. According to the numerical and the test results, an equation is proposed to modify the calculated ultimate curvature. Based on this, the drift capacity can be predicted with the equivalent plastic hinge method. The calculated result agrees well with the test result when FRP amount is low, but it is significantly larger when FRP amount increases. Finally, the main parameters exerting influences on the drift capacity of the FRP-confined RC circular column are analyzed. 相似文献
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Pseudo-static tests of three one-storey spatial RC frame-shear wall structures with floor slabs were conducted to investigate their failure modes and hysteretic behaviors. The test results were compared with those of pushover analysis. It is shown that: 1) damage of the frame beams occurs later and is less than that of the shear wall and the frame columns; 2) damage of the floor slabs under lateral loading is significant in regions close to the shear wall, and tensile stresses of slabs' steel bars in these regions are much larger; 3) in comparison with the case that the floor slabs are neglected, the maximum lateral load that a frame-shear wall structure can bear is larger in the case that the floor slabs are taken into account, and the contribution ratio of the shear wall also increases; 4) shear forces carried by the frame columns with identical cross sections and reinforcement details but located at different positions are close to each other on the whole. 相似文献
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The aim is to evaluate the seismic properties of ancient timber structure after strengthening and analyze the failure process and corresponding failure state. Based on the hysteretic behavior and energy dissipation principle of the dovetail column-frame strengthened with CFRP and Arches Brackets under the low reversed cyclic loading, the “potential of destruction-resisting” of the two energy-consuming components is obtained. The dissipated energy of each energy-consuming component under the various earthquake conditions is calculated combining with the shaking table test of ancient timber structure. The model of seismic damage evaluation of the two energy-consuming components is established on the basis of the “potential of destruction-resisting” and the dissipated energy. By means of the energy distribution coefficient, the relationship of the failure state between energy-consuming components and overall strengthened structure is discovered, and the model of seismic damage evaluation of the overall structure under the various earthquake conditions is presented. With the derived model of seismic damage evaluation, the failure coefficient of the energy-consuming components and the overall strengthened structure is quantitatively calculated. According to the failure state, the corresponding damage grade of overall strengthened structure is obtained. The results can provide a reliable theoretical basis for predicting the destruction before earthquake and re-reinforcement to the strengthened ancient timber structures after earthquake. 相似文献
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Earthquake induced dynamic axial force in reinforced concrete (RC) bridge bent columns will not only change the yield strength of the columns but also change their stiffness, which is seldom considered by the common lumped plasticity line model. Based on the fiber element model results that taking into account the influence of dynamic axial force on strength and stiffness simultaneously, the axial force stiffness interaction effect on the seismic responses of RC double column bridges was analyzed. The results show that, axial force stiffness interaction has a large effect on the seismic responses of the double column bridge in the elastic range, and it does not alter the ultimate capacity of the columns. Since the stiffness of the columns under compression and tension dynamic axial forces offset each other, the global displacement of bridge bent with equal columns is relatively unaffected by the axial force stiffness interaction, however, the differences of the column member forces are manifest. For the short column controls the global stiffness, the axial force stiffness interaction has significant influences on both the global displacement and member force responses. The influences become larger as the irregularity of the bridge bent increases, so the interaction between axial force and member stiffness should be sufficiently considered in seismic analyses. 相似文献
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A fiber beam-column element in conjunction with zero-length elements attached to its ends was proposed to simulate the flexural and shear mechanism respectively. Based on the Limit State Material model and the Shear Limit Curve model provided by OpenSees, the nonlinear shear effect of reinforced concrete column and its coupling with the flexural effect were defined. The reliability of the proposed model was validated by means of comparisons with existing test results. Finally, a plane frame from in-situ pushover test was simulated. It is shown that the proposed method, by taking the nonlinear shear effect into account, produces satisfactory results for frame columns with shear strength and stiffness degradation, while the conventional fiber beam-column element can hardly simulate actual flexure-shear failure mechanism for columns characterized by insufficient transverse reinforcement. The proposed method is applicable for nonlinear analysis of reinforced concrete frame structures with shear deficiencies. 相似文献
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The mechnical characteristics of concrete is sensitive to the strain rate and it is crucial to consider the effect of load rates on the behavior of reinforced concrete (RC) structures subjected to dynamic loads such as severe earthquakes. In this study, numerical simulations on the dynamic behavior of typical RC column specimens under dynamic loadings with different load rates were performed. Concrete constitutive model considering the strain rate effects proposed by the CEB code was employed with a fiber model to characterize the nonlinear strain rate dependent behavior of RC columns. The developed dynamic fiber element model was validated by comparing the simulated results of four RC column specimens with the fast loading test results. Results show that the developed fiber element model can predict the behavior of RC columns with acceptable accuracy. After valiating the proposed fiber elemen model considering the strain rate effect, the load carrying capacity of different RC columns with various longitudinal reinforcement ratios and volumetric stirrup ratios were simulated. Results show that the trends of the influences of longitudinal reinforcement ratios and volumetric stirrup ratios on the load carrying capacity of the RC columns under dynamic loadings are different. 相似文献
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Under seismic action, the damage of critical regions in ductile reinforced concrete structures can be regarded as combined results of cumulative damage caused by positive/ negative displacements with different displacement levels after yielding. On the basis of symmetric low-cyclic fatigue experiments on eight half-scale RC columns under different displacement levels, the development of cumulative damage and relationships between low-cyclic fatigue life and symmetric displacement amplitude are investigated. It is hoped that on this ground, more rational damage criteria for RC structures can be put forward. 相似文献
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Based on the principle of interactive analysis,the deformation equation of hybrid structure which contains rigid character value is established using the analysis of the frame - shear wall structure for reference, considering the rigid zone between concrete beam and concrete - tube, the shear deformation of concrete - tube, axial deformation of steel frames and semi - rigid connection between steel columns and concrete beams. Assuming the hybrid structure to be a continuous elastic structure with infinite degree of freedom, a free vibration equation has been built and the formula for calculating free vibration period has been deduced. The influences of various parameters to the coefficient of free vibration period relating to rigid character value are discussed according to some diagrams. It is shown that the rigid zone can lessen the free vibration period but the shear deformation of concrete - tube, axial deformation of steel frames, and the semi -rigid connection between steel columns and concrete beams can enhance the free vibration period. 相似文献
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HDPF加固钢筋混凝土柱抗震性能试验研究 总被引：2，自引：0，他引：2
为了研究高延性聚酯纤维加固钢筋混凝土柱的抗震性能，共进行了7根柱的低周反复试验，其中，3根在未加固状态下进行试验，4根柱粘贴高延性聚酯纤维加固后进行试验，针对位移延性系数、等效粘滞阻尼系数、总耗能、承载力和纤维带的应变进行了研究与分析。研究结果表明：未加固柱的承载力、耗能能力和延性都比较低，采用高延性聚酯纤维加固后的试件裂缝发展缓慢，加固后柱的承载能力、耗能能力、延性均有不同程度地提高；在塑性铰区域内增加局部配筋，能够提高纤维布的约束效果。 相似文献