共查询到17条相似文献,搜索用时 250 毫秒
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随机载荷下碳纤维薄板增强RC梁试验研究 总被引:2,自引:0,他引:2
桥梁等钢筋混凝土结构在运营期所受活载为随机载荷。研究随机载荷作用下碳纤维薄板(Carbon Fiber Laminate简称CFL)片材增强钢筋混凝土构件的疲劳性能,对于采用碳纤维薄板技术加固桥梁等混凝土结构有重要的指导意义。本文通过随机载荷作用下碳纤维薄板增强RC梁的三点弯曲疲劳试验,得到了增强梁的S-N曲线和跨中挠度的演化规律,揭示了随机载荷下增强梁的疲劳破坏机理。随机载荷下碳纤维薄板增强RC梁的破坏模式包括钢筋断裂、碳纤维薄板剥离、混凝土压坏等破坏形态,疲劳破坏过程具有明显的损伤成核、稳定扩展、失稳扩展的三阶段发展规律。 相似文献
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循环载荷下碳纤维薄板增强RC梁的疲劳性能试验研究 总被引:5,自引:2,他引:5
以碳纤维薄板(CFL)增强RC梁为研究对象,通过对循环载荷作用下增强梁的三点弯曲疲劳试验研究,得到了增强梁的线性对数疲劳寿命曲线和跨中挠度的演化规律,外推得到了极限疲劳强度和抗弯刚度的演化规律,揭示了增强梁的疲劳破坏机理。循环载荷下CFL增强RC梁的破坏模式包括混凝土开裂、碳纤维薄板与混凝土界面剥离、主筋屈服等模式,疲劳破坏过程具有明显的损伤成核、稳定扩展、失稳扩展三阶段发展规律。与普通RC梁相比较,CFL增强RC梁的裂缝分布较均匀、密集,粘贴CFL对增强梁的初始抗弯刚度提高幅度较小,对疲劳损伤阶段的抗弯刚度则提高了约一倍。根据CFL增强RC梁的疲劳寿命曲线得到其极限疲劳强度为25.42 kN,为三点弯曲静载下极限承载力的58.5%。 相似文献
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预应力CFRP加固混凝土结构技术由于具有显著优势,越来越多地被应用在桥梁加固中,本文针对冻融循环作用下预应力CFRP板加固钢筋混凝土梁的耐久性能进行了实验研究。通过12片加固梁试件的实验研究了不同次数冻融循环作用下预应力CFRP板加固梁的破坏形态和承载性能,分析了混凝土强度等级、冻融循环次数、CFRP初始应力水平等因素对加固梁耐久性能的影响。实验结果表明:经历冻融循环后试件的开裂荷载和极限承载能力都有了不同程度的下降,冻融侵蚀对CFRP加固混凝土结构产生了明显的不利影响;随着冻融循环次数的增加,加固试件的破坏模式逐渐由混凝土保护层剥离转变为界面剥离的破坏形态;冻融循环作用对预应力加固试件的整体不利影响要大于非预应力试件;混凝土强度为C60的预应力CFRP加固试件在冻融侵蚀作用下的退化要较强度为C30的加固试件显著。 相似文献
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针对T梁桥横隔板开裂、破损的问题,采用预应力钢棒对T梁横隔板进行加固。本文根据T梁桥的结构特点,提出了预应力钢棒的张拉位置及张拉力大小的确定原则,对横隔板的受力进行了分析。加固过程对横隔板裂缝宽度、张拉力进行了监测;对加固前后相同位置的受力情况进行了对比分析。结果表明:预应力钢棒加固T梁后,横隔板储备的压应力可以抵消活载产生的拉应力,横隔板裂缝宽度大大减小,且在荷载作用下裂缝不再扩展;桥梁横向分布性能大大改善,主梁挠度最大可以减少20%以上。采用预应力钢棒加固T梁横隔板效果良好。 相似文献
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ESPI技术对外贴纤维混凝土加固承载的实验研究 总被引:2,自引:0,他引:2
采用电子散斑干涉技术,对外贴碳纤维加固混凝土梁的外贴材料位移的分布特征,进行了全场实时测量,通过实验获得的散斑干涉条纹图可以得到外贴材料与混凝土梁的粘结传力长度随粘结长度及初始载荷之间的关系;了解用于加固的碳纤维材料的应变分布特点和产生梁侧剥离破坏时的碳纤维表面位移(应变)的演化过程。实验还说明了电子散斑干涉技术不仅可用于位移的测量,而且也可用于结构安全监测和破坏预报。文中给出了对C20D、C25A和C60C侧贴碳纤维板加固在不同载荷作用直到构件破坏前的位移测试及对试件C60C轴线上的剪应力分析结果。 相似文献
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Peiyan Huang Guangwan Liu Xinyan Guo Hao Zhou Xiaohong Zheng 《Acta Mechanica Solida Sinica》2013,26(1):46-52
The application of prestressed carbon reinforced polymer(prestressed CFRP)in reinforced concrete(RC)members can improve the mechanical properties of strengthened structures and strengthening efficiency.This paper proposed a semi-empirical prediction formula of fatigue lives of the RC beams strengthened with prestressed CFRP under bending loads.The formula is established based on the fatigue life prediction method of RC beams and fatigue experimental data of non-prestressed CFRP reinforced beams done before.Fatigue effect coefficient of the formula was confirmed by the fatigue experiments of the RC beams strengthened with prestressed carbon fiber laminate(prestressed CFL)under cyclic bending loads.Fatigue lives of the strengthened beams predicted using the formula agreed well with the experimental data. 相似文献
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In Florida, pre-stressed concrete bridges with a hybrid structural configuration, consisting of simply supported girders and
continuous deck units providing composite action, are prevalent. In this study, an actual bridge with this configuration is
instrumented with embedded vibrating wire strain gages during construction. The axial strain data are utilized to determine
the time-dependent pre-stress loss variation and distribution in the pre-tensioned concrete girders used for the bridge. In
this paper, however, we discuss the bridge instrumentation and monitoring technique used, and the deduced pre-stress losses
obtained from field-measured strains up to 150 days, before placement of the composite slab. A comparison of the measured
loss with the estimates of the Precast/Prestressed Concrete Institute (PCI) and the American Association of State Highway
and Transportation Officials (AASHTO) indicates that the field-measured pre-stress loss is non-uniform across the girder depth,
opposed to a uniform distribution implicitly assumed in most codes. The measured pre-stress variation is used in computing
the concrete stress distribution in the girder at different depths within the given cross-section. When compared to the concrete
stress from using the PCI and AASHTO suggested losses, the stress distribution resulting fron using the field-measured loss
is found to be non-linear, and in most cases higher. 相似文献
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Rongwei Lin Peiyan Huang Chen Zhao Xinyan Guo Xiaohong Zheng 《Acta Mechanica Solida Sinica》2008,21(4):359-363
The investigation on fatigue lives of reinforced concrete (RC) structures strength- ened with fiber laminate under random loading is important for the repairing or the strengthening of bridges and the safety of the traffic. In this paper, two methods are developed for predicting the fatigue lives of RC structures strengthened with carbon fiber [aminate (CFL) under random loading based on a residual life and a residual strength model. To discuss the efficiency of the model, 12 RC beams strengthened with CFL are tested under random loading by the MTS810 testing system. The predicted residual strength approximately agrees with test results. 相似文献
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在侧限约束条件下,混凝土材料的抗侵彻性能可得到较大提高,在此基础上施加预应力围压,其抗侵彻性能可进一步提高,但现有预应力方法对约束混凝土施加预应力较为困难。基于此,提出了一种相对简便的锥台嵌挤预应力约束方法,采用楔形块楔紧的原理,将锥面倾角为3°和直径微大于约束环的锥台形混凝土靶体挤入与之匹配的约束钢环内,通过锥面配合契紧的方式对混凝土靶体沿径向施加预应力,以锥台靶体的下压深度、盈差以及压入力的大小等指标控制预应力大小。采用LS-DYNA软件验证了该方法施加预应力的可行性,并通过重启动算法开展了预应力约束混凝土靶的抗侵彻性能研究。数值计算结果表明,靶体预应力随着其下压深度或盈差的增大近似线性增加,且混凝土靶体的抗侵彻性能随预应力增大而提高,但预应力过大时靶体内部发生损伤,导致其抗侵彻性能反而快速下降。对钢环强度、混凝土强度、含钢率和弹体速度等参数进行敏感性分析,结果表明,合理匹配钢环强度和混凝土强度,并选择合适的靶体含钢率,可有效提高靶体的预应力、抗侵彻性能以及钢材利用率;且弹体初速度越高,预应力对提高靶体抗侵彻性能的作用越明显。提出的锥台嵌挤预应力约束方法可为提高混凝土等脆性材料的抗侵彻性能提供一种新思路和方法。 相似文献
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《International Journal of Solids and Structures》2006,43(6):1372-1387
Six reinforced concrete beams strengthened in flexure using carbon fiber reinforced polymer (CFRP) laminates subjected to different sustaining loads were tested. The main goal of the test is to examine the effects of initial load and load history on the ultimate strength of strengthened reinforced concrete beams by externally bonded CFRP laminates. The main experimental parameters include different levels of sustaining load at the time of strengthening and load history. To explain the experimental results in quantitative terms, a theoretical model for flexural behavior of the strengthened reinforced concrete beam is also developed. Test results in the current study show that sustaining load levels at the time of strengthening have important influence on the ultimate strength of strengthened reinforced concrete beams. If the initial load is basically same, the ultimate strength of reinforced concrete beams strengthened with CFRP laminates is almost same regardless of load history at the time of strengthening. 相似文献
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根据碳纤维加固梁的构造、加固机理和材料性能,将粘贴在梁体下侧的碳纤维视作一系列的链杆约束,用力法求解链杆的内力,从而确定了加固梁各部分的受力关系.并提出反映受力关系的系数Kf进一步探讨,说明系数Kf具有丰富的内涵,能够反映受力关系和碳纤维的加固作用. 相似文献
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断裂能是定量表征混凝土断裂韧性的重要指标,但其实验结果显著依赖于混凝土试件断面面积评价方法的有效性和准确性。因测定困难,通常情况下只能由截面面积代替,造成断裂能计算结果存在较大误差。本文以碳纤维混凝土为研究对象,采用数字处理技术对混凝土断面形貌进行量化分析、重构,结合分形计算方法得到混凝土的真实断面面积,并将其用于碳纤维混凝土的断裂能计算,分析讨论了纤维掺量和长度对混凝土断裂能的影响规律。实验结果表明:碳纤维的引入显著提高了混凝土断面的粗糙度,表现为断裂面分形维度的明显提高,实际断面面积随之增大,以此为依据计算出的混凝土断裂能及其增益比随碳纤维掺量和长度的变化规律与韧度系数测试数据(按ASTM C1018)的一致性良好。 相似文献