【作者】 张伟；

【导师】 邓明科；

【作者基本信息】 西安建筑科技大学 ， 结构工程， 2023， 博士

【摘要】 混凝土空心砌块砌筑方便,具有较好的保温隔热性能,因此在砌体结构中得到了广泛的应用,其中村镇地区的混凝土空心砌块自建房所占比重较大。这类房屋一般未进行抗震设计,并且所采用的混凝土空心砌块生产工艺不规范,存在抗压强度低等特点,致使该类结构的力学性能较差。地震作用下,此类建筑房屋的损伤严重并容易倒塌。因此,开展加固该类结构的试验及理论研究具有重要的工程意义。高延性混凝土(HDC)是一种水泥基复合材料,具有高抗拉强度、高韧性、多裂缝开展以及拉伸应变硬化特性。本文将玄武岩织物网格与HDC相结合(TR-HDC),研究了其拉伸性能,并且系统开展了HDC及TR-HDC加固混凝土空心砌块砌体的受压、受弯、受剪及拟静力试验研究,探究了该加固方法对于砌块砌体结构的增强机理,建立了加固砌块砌体构件的抗压、抗弯及抗剪承载力计算公式。文章的主要研究成果如下:(1)分析了PVA短纤维掺量、织物网格层数与基体种类对玄武岩织物HDC拉伸力学性能的影响。研究结果表明:网格层数的增加,试件的强度及应变均有所提高,但织物网格的强度利用率减小;短纤维的加入可有效改善试件的破环形态,提高织物网格的强度利用率;基体类型对于试件拉伸强度的影响较小,对峰值应变有一定影响。(2)基于单轴拉伸试件的试验结果,考虑短纤维掺量与织物网格层数的耦合作用,通过回归分析,建立了TR-HDC的抗拉强度计算方法。通过分析TR-HDC的应力-应变曲线,建立了TR-HDC(破坏模式为织物拉断)的简化双线性应力-应变关系表达式。(3)分析了不同加固方式以及高厚比对于HDC加固混凝土砌块砌体轴压性能的影响,包括承载力以及变形能力。结果表明:单面加固试件的面外弯曲效应较为明显,导致变形较大;双面加固试件的承载力提高幅度较大,但变形相对较小;对拉螺栓的设置可提高双面加固试件加固层的强度利用率。通过理论分析,建立了加固试件的轴压承载力计算公式。(4)根据HDC及TR-HDC加固混凝土砌块砌体的四点弯曲试验,研究了剪跨比及不同加固方式对加固试件承载力、变形、延性和弯曲韧性的影响。结果表明:随着加固层强度的提高,试件由弯曲破坏转为弯剪破坏,而剪跨比增大时,加固试件容易发生弯曲破坏;双面加固试件的正截面高度增加,使其承载力及韧性提高。建立了加固试件的承载力计算公式,以预测加固试件在不同剪跨比时的受弯及受剪承载力。(5)根据对角剪切试验,分析了HDC及TR-HDC加固层对于加固试件的破坏形态、承载力、变形、延性及韧性的影响。结果表明:边框条带及单面加固试件的变形较大,承载力提高幅度相对较小;十字条带及双面加固试件的承载力提高幅度较大,但变形较小。试件的变形较大时,其延性及韧性较好。基于ECC梁的抗剪计算模型,建立了加固试件的受剪承载力计算公式。(6)通过6片无筋混凝土砌块砌体墙的拟静力试验,研究了HDC的不同布置方式(条带及面层)对加固试件的破坏形态、承载力、位移延性、刚度退化及耗能等的影响。结果表明:采用HDC加固砌体墙,可明显减小墙体的损伤,提高其抗震性能。基于加固试件的破坏形态(剪切滑移、弯曲摇摆与对角剪切),建立了相应的承载力计算公式。更多还原

【Abstract】 Concrete hollow blocks have convenient masonry techniques and good heat insulation performance.Therefore,these blocks have been widely used in masonry structures,and the self-built concrete block masonry buildings in village and town areas accounted for a relatively large part of the building stock.These houses are generally not designed to withstand earthquakes,and the production process of concrete blocks used is not standardized,with low compressive strength and other characteristics,resulting in the poor mechanical properties of this type of structure.Under the earthquake,the damage to such buildings is severe and easy to collapse.Therefore,it is engineering meaningful to conduct experimental and theoretical research on strengthening such structures.High ductile concrete(HDC)is a cementitious composite material with high tensile strength,toughness,multiple-cracking,and tensile strain-hardening properties.This paper has investigated the tensile properties of basalt fabric mesh combined with HDC(TR-HDC)and systematically conducted the compressive,bending,shear,and static cyclic loading tests of HDC-and TR-HDC-based retrofitted concrete block masonry.The aims are to study the strengthening mechanism of this retrofitting configuration for concrete block masonry structures and to establish the formulas for calculating the compressive,bending,and shear-bearing capacity of the retrofitted specimens.The main research contents and results are as follows:(1)The study focused on the tensile properties of basalt fabric-grid high ductile concrete(TR-HDC);the test parameters included PVA short fiber volume fraction,the number of fabric grid layers,and matrix type.The results showed that the stress and strain of the specimens improved with the increased number of textile grid layers,but the strength utilization of the fabric grid decreased.The addition of short fibers could effectively improve the failure mode of the specimens and increase the strength utilization of the fabric grid;the matrix type showed less effect on the tensile strength of the test specimens while significant on the peak strain.(2)Based on the test results of uniaxial tensile specimens,the tensile strength calculation method of TR-HDC was provided by regression analysis considering the coupling effect of short fiber volume fraction and the number of fabric grid layers.A simplified bilinear stress-strain curve expression for TR-HDC(with the damage mode of fabric pull-off)was established by analyzing the stress-strain curve of TR-HDC.(3)Analyzing the effects of the HDC retrofitting configurations and height-to-thickness ratios on the compression behaviors of HDC-based retrofitted concrete block masonry including the bearing capacity and deformation.The results show that:the out-of-plane bending effect of single-sided reinforced specimen leads to high deformation;double-sided retrofitted elements showed high bearing capacity,but the relatively small deformation.The setting of tensile bolts can improve the strength utilization of retrofitting layer of double-sided retrofitted members.Finally,the paper provided the computing method of bearing capacity for the retrofitted specimens.(4)Based on the four-point flexural test of HDC and TR-HDC strengthened concrete block masonry,the paper showed the effects of shear-to-span ratio and different reinforcement measures on the bearing capacity,deformation,ductility and bending toughness of the retrofitted specimens.The results show that the higher strength of the strengthened layer contributed to the flexural-shear failure of the test specimens.The increased shear-to-span ratio led to the retrofitted members being prone to bending damage.The increased height of the crossed section could improve the bearing capacity and toughness for the double-sided retrofitted specimens.The formulas were established to evaluate the flexural and shear capacity of retrofitted members with different shear-to-span ratios.(5)Based on the diagonal shear test,the paper analyzed the effects of HDC and TR-HDC overlay on the damage pattern,bearing capacity,deformation,ductility and toughness of the retrofitted concrete block masonry wallette.The results show that the deformation of the edge strip and single-sided strengthened wall is high,and the increase of bearing capacity is relatively small.The cross-strip and double-sided retrofitted specimens showed a higher bearing capacity while the lower deformation.The specimens with higher deformation generally showed higher ductility and toughness.Based on the shear calculation model of ECC beams,the formula was provided for calculating the bearing capacity of retrofitted specimens.(6)Based on the cyclic loading tests,this paper exhibited the responses of concrete block masonry walls strengthened using HDC.The test results showed the influence of the retrofitting configuration(HDC strip and layer)on the failure mode,bearing capacity,displacement ductility,stiffness degradation,and energy dissipation of the retrofitted specimens.It also indicated that the HDC-based retrofitting technique could reduce the damage and improve the seismic performance of concrete block masonry walls.Based on the failure mode of the retrofitted specimen,including shear sliding,rocking,and diagonal shear,the paper proposed the corresponding formulas to calculate the bearing capacity,respectively.更多还原