【作者】 吴元周；

【导师】 吕恒林；

【作者基本信息】 中国矿业大学 ， 结构工程， 2018， 博士

【摘要】 煤矿安全生产及废弃矿区空间再利用都要求以钢筋混凝土(RC)结构为主的煤矿地面既有建(构)筑物保持较高的承载能力和可靠性,但煤矿地面RC结构服役10年左右即发生损伤劣化,需要修复加固。粘贴纤维复材加固方法在煤矿应用较多,应用纤维水泥基材料代替环氧树脂胶可以克服其耐久性方面的问题,但工程应用可行性和机理还不明确。本文基于前期基础,采用物理试验、数值计算与理论研究相结合方法,研究了煤矿环境与荷载耦合作用下RC材料力学性能退化规律及劣化混凝土与锈蚀钢筋复合作用机理和RC梁、柱力学性能退化规律及影响因素,研制出适用于劣化RC梁、柱加固用的碳纤维水泥基材料(CFRCM),研究了CFRCM粘贴碳纤维布或编织网与劣化混凝土界面粘结性能和粘结剪切力模型,探究了纤维复材增强水泥基材料加固劣化RC梁、柱力学性能增强规律及承载力模型,开展了一系列的试验和理论研究工作。主要内容和创新成果如下:1.揭示了煤矿环境与荷载耦合作用下RC材料性能退化规律及劣化混凝土与锈蚀钢筋复合作用机理,建立了劣化混凝土与锈蚀变形钢筋间粘结性能退化模型。拟合得到混凝土中性化深度、抗压强度、弹性模量的时间函数以及钢筋名义屈服强度和极限强度与锈蚀率函数关系;综合考虑劣化混凝土抗压强度、钢筋锈蚀程度、锈胀裂缝宽度及锈蚀钢筋与劣化混凝土间摩擦系数,建立了劣化混凝土与锈蚀变形钢筋间粘结力模型。2.揭示了煤矿环境与荷载耦合作用下RC梁力学性能退化规律,研究了混凝土强度退化和钢筋锈蚀对劣化RC梁力学性能的影响机理,建立了劣化RC梁抗剪承载力模型。劣化RC梁逐渐由压剪破坏转变为受弯破坏,极限承载力随劣化程度线性缓慢下降,延性则先快后慢降低。混凝土强度退化27.90%时,受拉钢筋锈蚀率达到7.22%,最大锈胀裂缝宽度达到0.761mm,劣化RC梁承载力下降28.90%,延性系数降低33.01%。拟合试验结果,建立了基于混凝土抗压强度损失的劣化RC梁抗剪承载力模型。3.得到了煤矿环境与荷载耦合作用下大偏心受压RC柱力学性能退化规律及影响机理,建立了劣化大偏心受压RC柱承载力模型。劣化大偏心受压RC柱逐渐由受拉钢筋屈服破坏转变为混凝土压碎破坏,极限承载力和延性随劣化程度先快后慢下降。混凝土强度退化32.94%时,受拉钢筋锈蚀率达到8.68%,最大锈胀裂缝宽度达到3.46mm,劣化大偏心受压RC柱承载力下降了17.66%,延性系数降低了29.21%。分析了混凝土劣化对保护层的影响、钢筋锈胀裂缝与混凝土剥落角度的关系,完善了劣化大偏心受压RC柱承载力模型,并对试验结果进行验证。4.研制出适用于修复加固用CFRCM,构建了CFRCM粘贴碳纤维布与劣化混凝土界面粘结剪切力模型。CFRCM抗压强度超过30MPa,抗折强度接近10MPa;给出了CFRCM粘贴碳纤维布或编织网与劣化混凝土界面正拉粘结强度和粘结剪切强度演变规律及影响因素,拟合粘结剪切强度与混凝土相对抗压强度函数关系,完善了CFRCM粘贴碳纤维布与劣化混凝土界面最大粘结剪切力模型。5.CFRCM粘贴碳纤维布或编织网较好地发挥了增强RC梁斜截面抗剪力、限制斜裂缝发展的效果。加固梁在极限荷载作用下发生正截面受弯破坏;仅做抗剪加固提升劣化RC梁承载力较弱,同时抗弯和抗剪加固RC梁承载力最大增幅超过30%,且CFRCM粘贴碳纤维布比粘贴编织网加固效果更好;粘贴纤维复材可以有效增强RC梁的延性和刚度。6.CFRCM粘贴碳纤维布或编织网加固劣化大偏心受压RC柱力学性能得到有效增强。在极限荷载作用下,CFRCM粘贴碳纤维布或编织网加固劣化大偏心受压RC柱发生纵向纤维复材拉断破坏,表现出很强的脆性,主裂缝都只有一条。CFRCM粘贴碳纤维布更好地提升了RC柱承载力,平均提高幅度超过17.50%,但限制了其延性,且延性随着粘贴层数增加而大幅下降;粘贴碳纤维编织网加固虽然提升RC柱承载力幅度不大,但可以大幅度提升其延性和刚度。7.揭示了碳纤维复材用量对加固RC梁变形能力和刚度的影响机理,建立了纤维复材增强水泥基材料加固劣化RC梁抗弯和抗剪承载力模型及加固劣化大偏心受压RC柱承载力模型,并通过试验结果验证了模型的可行性。更多还原

【Abstract】 It’s necessary to keep the high carrying capacity and reliability of buildings or structures existed on the mine ground mainly in reinforced concrete(RC)structure,for the safe production of coal or reuse of abandoned mine space.However,those structures are damaged and deteriorated after about ten years service,and need to be repaired or strengthened.Fiber reinforced polymer(FRP)is given more application in the coal mine.Fiber reinforced cementitious matrix(FRCM)can be utilized to replace epoxy resin and overcome its durability problems,while the feasibility and mechanism are not clear yet.Based on the previous foundation and combination method of physical experiments,numerical calculations,and theoretical research,the degradation regularity of RC materials and the compound action mechanism between the deteriorated concrete and corroded steel bar under the coupling effect of colliery environment and load is studied.And then the degradation of RC beam and column is studied together with the influence factors.A type of carbon fiber reinforced cementitious materials(CFRCM)suitable to the reinforcement of deteriorated RC beam and column is developed,thus the bond behavior between FRP reinforced CFRCM and deteriorated concrete is studied and the shear strength model is established.The enhancement of RC beam and column strengthened with FRP reinforced CFRCM is explored and the calculation models of carrying capacity are established.Further,a series of experimental investigation and theoretical research work have been carried,and the main contents and creative achivements are summarized as follows.1.Degradation mechanism of concrete and steel bar under coupling effects of colliery environment and load are revealed and the bond strength model between the deteriorated concrete and corroded steel bar is established.The time functions of neutralization depth,compressive strength and elastic modulus of concrete are established by numerical fitting,together with the nominal yield strength and ultimate strength of steel bar.Bond strength between deteriorated concrete and corroded deformed steel bar is established,with comprehensive consideration of compressive strength of concrete,corrosion of steel bar,crack width,and the friction coefficient between corroded steel and deteriorated concrete.2.Mechanical degradation of RC beam under coupling effect of colliery environment and load is reavled.The influence mechanism of concrete deterioration and steel bar corrosion on the mechanical behavior of RC beam is studied and then the shear carrying strength model is established.Failure mode of deteriorated RC beam changes from compression shear failure to a bending failure.The ultimate carrying capacity decreases linearly with deterioration degree,while the ductility desreases rapidly first and then slowly.As the compressive strength of concrete decreases 27.90%,the corrosion ratio of steel bar comes to 7.22% and the maximum width of expansion crack reaches 0.761 mm,thus the carrying capacity of deteriorated RC beam decreases by 28.9%,and the ductility coefficient decreases by 33.01%.Shear capacity model of degraded RC beams is established by numerical fitting,based on the compressive strength loss of concrete.3.Mechanical degradation of large eccentric compressed RC column under coupling effect of colliery environment and load is reavled together with the influence mechanism and then the carrying strength model is established.Failure mode of deteriorated RC column changes from yield of tensile steel bar to crushing of compressed concrete.The ultimate carrying strength and ductility decrease rapidly first and then slowly.As the compressive strength of concrete decreases 32.94%,the corrosion ratio of steel bar comes to 8.68% and the maximum width of expansion crack reaches 3.46 mm,thus the bearing capacity of large eccentric compressed RC column decreased by 17.66%,and the ductility coefficient decreased by29.21%.As the influence of concrete degradation on the protective layer,the relationship between corrosion cracks and peeling angle of concrete are considered,the model of bearing capacity of RC column degraded by large eccentric compression is improved,and the test results are verified.4.A type of CFRCM suitable for repair and reinforcement is developed,with the compressive strength over 30 MPa and the bending strength close to 10 MPa.The evolution law and influencing factors of tensile bond strength and shear strength at the interface of CFRP sheet or woven mesh reinforced CFRCM and deteriorated concrete are revealed.Thus,the relationship between shear strength of strengthening layer and the relative compressive strength of concrete is fitted and the maximum shear model between CFRP sheet reinforced CFRCM and deteriorated concrete is improved.5.CFRP sheet or woven mesh reinforced CFRCM increases the shear strength of RC beam and limits the development of oblique cracks effectively.Under the ultimate load,the normal section of strengthened beam is subject to bending failure.The carrying capacity of deteriorated RC beam is slightly improved with shear reinforcement only,while the maximum increase is more than 30% when the RC beam was bending and shear strengthened.The strengthening effect of CFRP sheet reinforced CFRCM is more effective than woven mesh.The ductility and stiffness of RC beams are both enhanced.6.The mechanical property of deteriorated RC column strengthened with CFRP sheet or woven mesh reinforced CFRCM is improved effectively.Under the ultimate load,longitudinal fiber composite material breaking breakage occurs to the deteriorated RC column strengthened with CFRP sheet or woven mesh reinforced CFRCM under large eccentric compression,showing a strong brittle with only one main crack.The carrying capacity of RC column strengthened with CFRP sheet reinforced CFRCM increases better,with an average increase of more than 17.50%,but the ductility is limited and decreased significantly with the increase in the number of CFRP sheets.The ductility and stiffness of RC column strengthened with CFRP woven mesh reinforced CFRCM are well improved though the carrying capacity is relatively lower.7.The mechanism of deteriorated RC beam and column strengthened with CFRP sheet or woven mesh reinforced CFRCM is analyzed,and the effect of CFRP sheet amount on the deformability and stiffness of the strengthened beam is revealed,thus the method to determine the effective utilization rate of the CFRP sheet is given.Based on deterioration of RC material and effective utilization of FRP,the models for flexural capacity of RC beam and carrying capacity of RC column under large eccentric compression strengthened with FRP reinforced CFRCM are improved.As the relationship between the effective coefficient of FRP shear reinforcement and the shear strength between the CFRP sheet and deteriorated concrete is revealed,the shear capacity model of deteriorated RC beam strengthened with FRP reinforced CFRCM is improved and verified through experimental results.更多还原