GFRP/CFRP 混凝土界面剪切性能

设计GFRP/CFRP 混凝土搭接双剪试验,研究了界面糙化方式、界面剂种类以及界面形成过程中的压力和温度对GFRP/CFRP层间混杂纤维复合材料混凝土界面剪切性能的影响,并分析了各种因素的影响机理.结果表明：界面化学糙化（酸化）方式可提高界面的机械锚固性能,但降低了固化剂活性,界面剪切强度较物理糙化方式降低29%;15%（质量分数）KH550（硅烷偶联剂）界面剂能显著改善GFRP/CFRP 混凝土界面粘接性能,用其粘接的界面剪切强度较用普通E44环氧树脂界面剂提高66%;GFRP/CFRP 混凝土界面剪切强度随固化压力的增加先增加后减少,005MPa固化压力下界面剪切强度最优;常温范围内（15～45℃）,固化温度对GFRP/CFRP 混凝土界面剪切强度影响不大,但当温度低于15℃时界面的剪切性能急剧降低,且升温后界面剪切强度仍较常温固化试件差.     

土工膜/GCL界面剪切强度特性的试验研究

土工复合膨润土垫(GCL)是一种新型复合材料,其良好的防渗隔气功能以及抗张拉的能力使其与HDPE土工膜(GM)的联合使用在填埋场具有广泛的应用前景,但GM/GCL界面较低的剪切强度易导致填埋场衬垫系统等失稳。利用大尺寸界面直剪仪进行三种不同土工膜与GCL界面的剪切试验,重点研究GCL不同加载水化顺序对膨润土挤出及界面强度的影响。试验结果表明:干燥状态下,粗糙土工膜/GCL界面的峰值强度较大于光滑土工膜/GCL界面的峰值强度,但粗糙土工膜/GCL界面表现出强烈的应变软化特性,其残余强度接近于光滑土工膜/GCL界面的强度;不同加载水化顺序是影响膨润土挤出的重要因素,并严重影响界面剪切强度;膨润土挤出造成粗糙土工膜/GCL界面的峰值摩擦角降低3.5°,大位移摩擦角降低7.6°,接近光滑土工膜/GCL界面的摩擦角。     

粗糙度对硅质板岩–泥岩界面强度与变形特性影响试验研究

为探讨粗糙度对硅质板岩–泥岩界面强度与变形特性影响,利用界面剪切仪开展软–硬岩界面剪切力学特性试验研究,分析界面试样剪切破坏模式、变形特征、强度演化规律,并探讨粗糙度对软–硬岩界面强度影响机制。结果表明：(1)硅质板岩–泥岩界面剪切破坏模式分为界面间剪断、泥岩内剪断以及界面与泥岩混合剪断三类。界面粗糙度越大,试样剪切破坏模式越趋于泥岩内剪断;(2)粗糙度对硅质板岩–泥岩界面剪切变形影响显著,随界面粗糙度增大,其剪切刚度降低、峰值强度点位移增大,表明界面试样剪切破坏前更易变形、剪切破坏时产生的塑性变形量越大;(3)粗糙界面存在显著提升了硅质板岩–泥岩界面抗剪强度,且界面粗糙度越大,其峰值强度与残余强度提高幅度越高;粗糙度大幅提升了界面试样的黏聚强度,但对其摩擦强度提升幅度有限;(4)剪切过程中泥岩不断被硅质板岩粗糙界面铲刮挤密形成“硬化剪切带”,且界面糙度越大,“硬化剪切带”越厚,试样剪断面越趋于泥岩内部。而泥岩抗剪强度大于界面强度,因此界面强度随粗糙度增大而不断提高,且提高幅度受控于剪断泥岩的黏聚强度。     

温度对硅树脂基复合材料力学性能和热性能的影响

研究了硅树脂复合材料高温下力学性能的变化。结果表明在温度高于500℃时层间剪切强度和拉伸强度降低明显,这是由于硅树脂热裂解和重组造成的。利用SEM分析了硅树脂复合材料室温和800℃时树脂与纤维的界面变化。研究了硅树脂基复合材料在不同温度下热膨胀系数,结果表明500℃是它的机械性能和热性能的转折点。     

高应力作用界面剪切性质的试验研究

通过在DRS-1型微机高压直残剪试验系统上所进行的不同土质与不同基底的界面剪切特性试验研究表明：高应力作用下不同结构接触面的峰值强度、残余强度与正应力之间符合库伦强度准则：基底性质对标准砂的抗剪峰值强度准则影响较小，但对其抗剪残余强度准则影响较大：混凝土界面下残余抗剪强度准则的选择与法向应力的大小有关，法向应力较低时剪切破坏发生在砂土中，法向应力较高时剪切破坏发生在界面上，而对于其他基底的剪切破坏始终发生在界面上：标准砂在剪切过程中的体积应变-剪切位移关系，呈现出应变硬化现象整体符合双曲线模型，表现为剪缩性。试验数据的直观分析和方差分析表明：对于残余强度和初始剪切刚度，法向应力是第一影响因素，其次是土体的性质，第三是界面的基底性质，剪切速率的影响最小。     

带植筋新旧混凝土粘结界面剪切强度试验研究

新旧混凝土粘结界面的剪切强度是衡量界面粘结性能的最重要指标。基于Z形粘结试件直剪试验,研究植筋情况下新旧混凝土粘结界面的剪切强度。采用统计方法,分析植筋直径、植筋深度及植筋率对粘结界面剪切强度的影响,结果表明:为保证新旧混凝土界面的粘结性能,植筋深度需不小于10倍的植筋直径,且界面剪切强度随植筋率的增大而增大。利用试验结果,对已有新旧混凝土粘结界面剪切强度的主要计算公式进行了对比分析,分析结果表明:吻合度较高的计算公式,可供实际加固工程参考。     

钢板、高聚物、土不同材料界面剪切特性试验研究

为了研究高聚物与不同介质界面的剪切特性,基于直剪试验,研究了土体含水率、法向应力、界面类型、高聚物密度和成型方式等因素对界面剪切强度的影响。研究结果表明：钢板-高聚物界面破坏形式与其它界面存在差异,呈现脆性破坏。不同界面的剪切强度与高聚物密度、法向应力和土体含水率存在关系。界面的剪应力值随高聚物密度和法向应力的增大而逐渐增大,随含水率的增大而减小。当法向应力和土体含水率一定时,非预成型高聚物-土体界面剪切强度大于预成型高聚物-土体界面,但随着含水率的增大,高聚物成型方式对高聚物-土体界面剪切强度的影响逐渐减小。当其它条件一致时,钢板-高聚物界面、高聚物-土体界面、土体自身和钢板-土体界面的剪切强度依次减小,使用高聚物后,界面抗剪强度分别提高了73%,108%,125%和115%,钢板-高聚物-土体界面的抗剪强度明显优于单纯钢板-土体界面。     

非水反应高聚物与土工材料的界面剪切特性

基于单调直剪试验,研究了竖向应力、剪切速率对非水反应类高聚物-土工布界面及高聚物-砂土界面的剪切应力、剪切位移、抗剪强度和剪切模量等剪切特性的影响.结果表明:在给定竖向应力和剪切速率下,随着剪切位移的增加,高聚物-土工布界面、高聚物-砂土界面均表现出剪切软化的特性;竖向应力对高聚物-土工布界面抗剪强度及剪切模量的影响显著,在剪切速率v=2mm/min下,随着竖向应力由50kPa增加至150kPa,高聚物-土工布界面的抗剪强度由15kPa增至46kPa;在给定竖向应力下,剪切速率v=1~3mm/min时,剪切速率对高聚物-土工布界面的抗剪强度以及高聚物-砂土界面的抗剪强度和剪切模量的影响均较小.     

带剪切销钉的复合砂浆加固砌体界面抗剪性能研究

通过对16个复合砂浆加固砌体试件进行砌体-复合砂浆界面的抗剪试验,得到了界面的破坏形态、抗剪强度和荷载-滑移曲线。试验结果表明：剪切销钉能显著提高粘结面的抗剪强度,并且随剪切销钉植筋面积增加界面抗剪强度也随之增大;剪切销钉能改变界面的破坏模式,增大界面破坏时的滑移变形;剪切销钉植筋深度是影响界面抗剪强度和破坏形式的另一个主要因素,砌体中剪切销钉的最小植筋深度应取10倍销钉直径;水泥基界面剂对界面抗剪强度有负面影响,因此用水泥复合砂浆加固砌体结构时不宜使用水泥基界面剂。在试验研究基础上,拟合了考虑剪切销钉植筋面积的砌体-复合砂浆界面抗剪强度公式。图10表3参10     

尼龙束捻度对水泥砂浆界面粘结的影响

通过织物拔出试验、抗折强度试验和扫描电镜对水泥基体微观破坏形貌的分析，研究了织物中尼龙束捻度对其增韧水泥砂浆界面粘结的影响。研究结果表明：存在着1个尼龙束捻度范围，在该范围内，捻度的增加有助于复合材料的界面粘结，且界面粘结强度随之提高；超出这一范围，捻度的增加反而不利于复合材料的界面粘结，界面粘结强度随之下降。     

钢-混凝土组合梁加宽混凝土旧桥技术中组合横梁界面受力性能研究

在钢-混凝土组合梁加宽旧桥技术中,旧桥混凝土边梁与新加宽的钢-混凝土组合梁间的横向连接采用钢-混凝土组合横梁的形式,这种横梁形式较为新颖,目前相关试验研究尚未有报道。对6个钢-混凝土组合横梁进行试验研究,通过采用目前已有的新老混凝土植筋界面承载力计算方法对试验结果进行对比计算。研究结果表明:组合横梁界面的破坏模式为新老混凝土界面破坏,钢-混凝土界面没有任何破坏特征;新老混凝土界面黏结破坏以前,新老混凝土之间几乎没有滑移,整体性很强;新老混凝土界面黏结破坏以后,界面剪力主要由植筋承担,试件延性良好。针对钢-混凝土组合梁加宽旧桥技术中组合横梁的破坏模式,采用合理的材料本构关系,提出三阶段界面受力模型,理论方法计算结果与试验值吻合良好。通过理论分析确定界面的破坏机理:新老混凝土界面的极限抗剪强度由混凝土强度,界面粗糙程度和摩擦系数共同确定,界面正应力的存在有利于极限抗剪强度的提高;新老混凝土界面的残余抗剪强度主要由界面植筋提供,植筋率和植筋屈服强度是主要影响因素。最后,提出适用于实际工程的设计方法。     

部分预应力陶粒砼叠合板的试验研究

本文通过三块叠合简支板和五块叠合连续板的试验,研究了部分预应力普通砼薄板叠合陶粒砼楼板的基本性能。从极限强度、内力重分布规律、使用荷载下的变形性能、构件的廷性以及叠合面的抗剪强度、与普通砼叠合板进行了对比。试验结果表明,部分预应力陶粒砼叠合连续板跨中取用较低的预应力度,不仅能满足正常使用极限状态的要求,而且具有较好的延性。叠合面采取无筋结合面的措施,具有足够的抗剪能力,是安全可靠的。     

Failure mechanisms of geosynthetic clay liner and textured geomembrane composite systems

The objective of this study was to evaluate shear behavior and failure mechanisms of composite systems comprised of a geosynthetic clay liner (GCL) and textured geomembrane (GMX). Internal and interface direct shear tests were performed at normal stresses ranging from 100 kPa to 2000 kPa on eight different GCL/GMX composite systems. These composite systems were selected to assess the effects of (i) GCL peel strength, (ii) geotextile type, (iii) geotextile mass per area, and (iv) GMX spike density. Three failure modes were observed for the composite systems: complete interface failure, partial interface/internal failure, and complete internal failure. Increasing normal stress transitioned the failure mode from complete interface to partial interface/internal to complete internal failure. The peak critical shear strength of GCL/GMX composite systems increased with an increase in GMX spike density. However, the effect of geotextile type and mass per area more profoundly influenced peak critical shear strength at normal stress > 500 kPa, whereby an increase in geotextile mass per area enhanced interlocking between a non-woven geotextile and GMX. Peel strength of a GCL only influenced the GCL/GMX critical shear strength when the failure mode was complete internal failure.     

Behavior of channel shear connectors, Part I: Experimental study

In composite beams, shear connectors are commonly used to transfer longitudinal shear forces across the steel-concrete interface. This paper presents an experimental study on the behavior of channel shear connectors embedded in a solid concrete material slab under monotonic and low-cycle fatigue loading. The latter would be applicable to composite structures subjected to seismic events. Of specific interest are the behavior and effects of different concrete materials. A series of push-out specimens made of plain concrete, reinforced concrete (RC), fiber reinforced concrete (FRC) and engineered cementitious composite (ECC) were tested for this evaluation. The results show that the reversed cyclic shear strength of most specimens is 10%-23% lower than their monotonic strength. Also, using the polypropylene fibers (FRC specimens) has a slight effect on the shear strength and load-displacement behavior of the specimens; however, using the polyvinyl alcohol fibers (ECC specimens) causes considerable increase in ultimate strength and ductility of channel shear connectors. Finally, the experimental load capacities are compared with that suggested by North American design codes.     

水化状态对含针刺GCL复合衬里抗剪强度的影响分析

针刺GCL和HDPE土工膜(GM)在防渗工程中应用广泛,含多层界面的复合衬里整体抗剪强度是边坡稳定性分析的关键。介绍了含针刺GCL复合衬里的大单剪试验方法,并且对比分析了针刺GCL初始状态分别为干燥和完全水化两种情况下的复合衬里抗剪强度。结果表明,复合衬里的剪切破坏不会发生在干燥针刺GCL内部界面,而GCL干燥状态下的复合衬里单剪强度未必高于GCL完全水化状态下的复合衬里单剪强度。结合含GCL复合衬里的剪切破坏机理,阐述了针刺GCL的水化状态对复合衬里抗剪强度的影响。含GCL复合衬里在不同水化状态下的界面滑移稳定性都应引起工程人员的重视。     

高温后钢筋混凝土叠合梁抗剪承载力可靠度分析

提出了一种钢筋混凝土叠合梁在高温后斜截面和叠合面抗剪承载力可靠度的分析方法。选取钢筋混凝土（RC）梁的热工参数,应用ABAQUS进行热传导分析。基于热分析结果和RC叠合梁高温后抗剪承载力计算方法,得到斜截面和叠合面的剩余承载力。基于MATLAB应用蒙特卡洛法进行可靠度分析。结果表明,受热时间对可靠度的影响显著,可靠度指标随着混凝土强度、配箍率的增大而增大,随着荷载比的增加先增大后变化不明显。常温下RC叠合梁斜截面承载力可靠度大于叠合面,但随着加热时间的增加,叠合面的抗剪能力优于斜截面。该方法可以用于火灾高温作用后RC叠合梁承载力可靠度分析,具有较高的精度和准确性。     

水化针刺GCL+GM复合衬里的单剪破坏特征

针刺GCL和HDPE土工膜(GM)广泛应用于填埋场防渗衬里,GCL的内部剪切强度和GCL/GM界面剪切强度是填埋场复合衬里边坡滑移稳定性的控制因素。通过开展不限定剪切破坏面的水化针刺GCL+GM复合衬里大单剪试验,获得了剪切过程中GCL/GM界面位移和GCL内部位移发展规律,分析了GM的糙面分别与GCL的有纺面和无纺面接触时的峰值强度,揭示了GCL+GM复合衬里的整体剪切破坏特征。试验结果表明:大单剪试验能够正确和合理地模拟GCL与GM间的相互作用,GCL+GM复合衬里中的极限破坏面不仅会随着法向应力的增加而发生转移,甚至出现GCL内部和GCL/GM界面同时成为剪切破坏面的临界状态。     

Dynamic shear behavior of GMB/CCL interface under cyclic loading

The dynamic shear behavior of composite liner interface is of great importance for landfill seismic analysis. In this study, an experimental investigation of the shear behavior of the interface between smooth high density polyethylene (HDPE) geomembrane (GMB) and compacted clay liner (CCL) is presented. A series of displacement-controlled cyclic shear tests were conducted to investigate the effects of displacement amplitudes, normal stress levels and number of cycles on the GMB/CCL interface shear behavior. Cyclic loading with higher displacement amplitude will produce greater vertical contraction and lower interface initial shear stiffness. Also, significant shear strength degradation was observed within the first 5 shearing cycles, then followed by slight interface reinforcement in subsequent cycles. The dynamic shear modulus of GMB/CCL interface is dependent on both normal stress levels and displacement amplitudes, while the damping ratio is only affected by displacement amplitudes. Finally, a method considering the GMB/CCL composite liner as an equivalent soil layer was proposed, which is useful for landfill seismic analysis.     

Shear strength of interfaces between unsaturated soils and composite geotextile with polyester yarn reinforcement

Composite geotextiles with polyester yarn reinforcement have been commonly used in combination with unsaturated soils. Both unsaturated and saturated shear strength of the interfaces were investigated between a composite geotextile and three major types of materials: silty sand (SM), low-plasticity silt (ML) and high-plasticity clay (CH) in a direct shear box. The interfaces were formed using two methods (A and B) to reflect the wide range of possible contact conditions in practice. Method A involved statically compacting the soil directly on top of the composite geotextile, while for Method B, the soil was statically compacted in a separate mold and later brought into contact with the composite geotextile. Type B interfaces required a larger displacement to mobilize the shear strength than Type A interfaces. The ultimate failure envelopes of SM and ML soils were similar to those of their interface shearing. Notably, the failure envelopes for the clay-geotextile interface of both types were higher than that of clay alone. The unsaturated soil-only shearing had a higher peak strength and tended to dilate more than saturated soil-only shearing, while unsaturated soil-interface shearing appeared to be more contractant than saturated interface shearing. The strength variations with suction for all tested soils and interface shearing were clearly non-linear. A new model that takes account of the condition of soil-geotextile contact intimacy is proposed for predicting the variation of interface strength with suction, based on the variation of the soil's apparent cohesion with suction and the geotextile-water retention curve.