T形肋开孔玻璃纤维增强材料抗剪键受力性能试验

为提高玻璃纤维增强材料GFRP与混凝土的界面黏结性能,提出了一种新型T形肋开孔GFRP抗剪键,可应用于受力复杂的组合梁、板设计。通过推出试验测试了这种新型抗剪键的基本力学性能,得到了其破坏形态、裂缝分布规律及荷载-相对滑移曲线。试验结果表明:界面出现滑移后,T形肋开孔GFRP抗剪键能提供较好的抗剪变形能力;最终混凝土突然出现剪切破坏,GFRP抗剪键基本完整;对于孔内无穿孔钢筋的T形肋开孔GFRP抗剪键呈现出与开孔钢板连接件相似的破坏机理,其承载力取决于左右两边混凝土块的抗剪能力与穿过T形肋孔洞的混凝土榫所提供的抗剪销栓力。基于试验得到的破坏机理建立了T形肋开孔GFRP抗剪键的极限承载力计算公式,计算结果表明:该公式具备足够的安全富余系数,可供工程设计参考。     

GFRP型材与混凝土湿粘结界面力学性能研究

文章进行了湿粘结界面条件下GFRP型材与混凝土粘结界面力学性能的推出式试验研究,试验变量为混凝土浇筑时间、界面形式以及GFRP型材的形式;对比分析了带T形肋和不带T形肋GFRP型材与混凝土界面的抗剪能力,探究了环氧树脂胶体养护时间与界面形式对界面抗剪性能的影响,获得了相应的荷载-滑移曲线、应变分布、剥离和极限荷载及破坏形态。结果表明:不带T形肋和带T形肋的试件的破坏形态明显不同;胶体养护时间为30 min试件的极限荷载和界面剪切刚度均强于胶体养护时间为0 min试件;在粘结界面中加入粗砂,增大有效粘结面积,适当增加胶体养护时间,可以显著提高界面剥离承载力。     

GFRP肋式剪力连接件受力性能对比试验研究

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。     

PBL连接件在长期荷载作用下的试验研究

为了研究PBL连接件在长期荷载作用下的受力性能,对6个PBL连接件试件进行了6个月的长期加载试验及极限承载力破坏试验,考虑的影响参数为钢板开孔直径、厚度和孔洞个数。试验考察了试件变形发展过程及破坏形态,得到了试件荷载-滑移曲线以及荷载-横向贯通钢筋应变曲线,并建立了钢梁与混凝土板相对滑移、横向贯通钢筋和孔洞周边应力与加载时间关系曲线;最后,在试验的基础上,对比总结了长期荷载和短期荷载作用对PBL连接件力学性能的影响。研究结果表明:增加开孔钢板直径、厚度和孔洞个数可以有效提高PBL连接件抗剪刚度,减小其相对滑移;与短期荷载作用下的试验结果相比,长期荷载作用下PBL连接件试件的抗剪刚度下降了16%~30%,但其破坏形态、荷载-横向贯通钢筋应变曲线、荷载-滑移曲线变化特点基本相同,且其极限抗剪承载力无显著差异。     

PBL加劲型矩形钢管混凝土界面粘结-滑移性能

对开孔钢板连接件（PBL）加劲型钢管混凝土构件界面粘结性能进行研究,以PBL加劲肋的开孔间距、开孔孔径、混凝土粗骨料粒径为参数,进行了该类试件抗剪性能的推出试验,并与普通钢管混凝土试件进行了界面粘结强度、抗剪刚度等参数的对比分析,提出了钢管混凝土内PBL加劲肋承载力受混凝土粗骨料含量影响的修正计算方法。结果表明:通过设置PBL加劲肋可以明显提高钢管混凝土的界面抗剪承载力和刚度,其粘结强度受加劲肋开孔参数的影响;引入的PBL抗剪承载力公式修正系数与开孔板内混凝土榫的粗骨料面积比呈线性关系。     

钢管与管外混凝土界面粘结抗剪能力试验研究

为研究并揭示钢管混凝土叠合柱的钢管与管外混凝土界面的粘结抗剪能力,完成了10个试件的推出试验,其中3个试件的钢管外壁未焊接抗剪连接件,4个试件的钢管外壁焊接钢筋环、3个试件的钢管外壁焊接栓钉作为抗剪连接件。试件的破坏形态为钢管混凝土被推出,钢筋环的焊缝及栓钉的栓杆被剪断;未焊接抗剪连接件试件的实测界面抗剪粘结强度略大于1.0MPa;钢筋环直径由6mm增大为8mm、或由1根增加为2根、或栓钉直径由10mm增大为16mm,界面的受剪承载力增大;1根直径8mm的钢筋环的受剪承载力大于4根直径16mm的栓钉的受剪承载力。钢筋环及栓钉的受剪承载力试验值大于公式计算值。提出了钢管与管外混凝土界面抗剪粘结设计建议。     

预制夹芯墙体中新型复合式连接件受力性能试验研究

为使预制混凝土夹芯墙体的内叶与外叶之间通过连接件具有良好的整体工作性能,针对新型复合式连接件,对其抗拉、抗剪性能开展试验研究,通过15个抗拉试验和12个剪切试验,获得了该连接件的抗拉及抗剪能力、破坏过程与现象,分析了墙体中分布钢筋与连接件位置关系及混凝土强度等级对连接件抗拉性能及剪切性能的影响。结果表明:复合式连接件的受拉破坏形式为混凝土的锥形体破坏,而剪切试验呈现连接件穿心钢筋的弯剪破坏;复合式连接件的抗拉承载力及抗剪承载力与实际工程中连接件所受的拉力及剪力实测值相比,具有较大的安全储备,可在实际工程中应用推广;墙体内分布钢筋与连接件的位置关系对极限承载力大小及破坏现象基本没有影响,但外叶墙中的钢筋网片以及十字形钢筋能够延缓连接件的拔出过程;混凝土强度对连接件的抗拉承载力有显著影响,而对抗剪承载力无影响;最后,基于试验现象及分析,提出了新型复合式连接件抗拉承载力计算方法。     

开孔板式抗剪件受力性能试验研究

组合楼盖中钢与混凝土之间的剪力传递是通过设置在钢与混凝土之间的剪力连接件实现的。开孔板式抗剪件具有抗剪承载力大、抗疲劳性能好、施工简单的特点。根据剪力传递的方式设计出适用于建筑领域的开孔板式抗剪件。采用静力推出试验方法,通过11个模型试验,研究分析出该种抗剪板的破坏形态以及抗剪钢板厚度、高度、开孔直径、孔内钢筋直径、穿孔钢筋的有无等因素对抗剪板抗剪承载能力和抗滑移特征的影响。结果表明:该种抗剪件具有良好的力学性和经济性,特别是在开孔中穿钢筋时,可大幅度提高试件的抗剪承载力和延性性能。     

开孔板连接件受剪性能试验研究

开孔板连接件是钢-混凝土组合梁中常用的一种抗剪连接件。通过21个开孔板连接件试件在单调静力荷载作用下的推出试验,研究了开孔板的开孔直径、混凝土强度等级、孔中横向贯通钢筋的直径和数量等对开孔板连接件的破坏形态、荷载-滑移特性和受剪承载力等的影响。研究表明:开孔板连接件的荷载-滑移曲线(P-S曲线)大致可分为弹性阶段、塑性发展阶段和下降段;提高混凝土强度等级、增大开孔直径可提高开孔板连接件的受剪承载力,横向贯通钢筋直径由16mm增大至20mm时,试件的受剪承载力提高了21.8%,配置横向贯通钢筋2 16的试件受剪承载力比相应的未配置横向贯通钢筋的试件高19.1%;随着混凝土强度等级的提高,试件抗剪刚度增大,而开孔直径及横向贯通钢筋直径则对抗剪刚度无明显影响。最后,基于试验结果提出了开孔板连接件受剪承载力的计算方法。研究成果可为编制《钢-混凝土组合桥梁设计规范》提供依据和参考。     

Experimental study on mechanical behavior of shear studs in assembled monolithic steel-concrete composite beam

为研究装配整体式钢-混凝土组合梁中栓钉抗剪连接件的受力性能,设计了10个栓钉抗剪连接件,对其进行推出试验,得到了现浇混凝土板和预制混凝土板中栓钉抗剪连接件在单调和重复荷载作用下的界面剪力-滑移曲线以及破坏形态。结果表明：预制混凝土板中栓钉受剪承载力比现浇混凝土中栓钉受剪承载力略低,均为栓杆剪断和栓钉根部焊缝破坏;重复荷载作用下峰值界面剪力对应的界面滑移明显大于单调荷载作用下峰值界面剪力对应的界面滑移;重复荷载作用下的峰值界面剪力与单调荷载下的峰值界面剪力相当,其界面剪力-滑移曲线基本一致。     

开孔板连接件受剪承载力研究

为研究开孔板（PBL）连接件的受剪承载力,在已有试验和理论研究的基础上,分析了单孔PBL连接件的破坏模式及受剪承载力的主要影响因素,并建立开孔钢板厚度不小于9mm时,单孔PBL连接件考虑侧向约束力的受剪承载力模型。该模型考虑了开孔钢板周围的混凝土包裹、贯通钢筋和试件底面摩擦对PBL连接件提供的较强约束作用,以及由此导致的单孔PBL连接件受剪承载力的提高。通过大量的单孔PBL连接件的受剪试验数据拟合得到单孔PBL连接件的受剪承载力计算公式。该计算公式和已有计算公式的计算值与试验值的对比分析表明,未设置贯通钢筋的试件受剪承载力的离散性较大,而设置贯通钢筋的试件受剪承载力的离散性相对较小;该计算公式能合理考虑混凝土包裹、贯通钢筋和试件底面摩擦对PBL连接件受剪承载力的影响,其计算结果与试验值总体吻合得较好。     

Structural behavior of multifunctional GFRP joints for concrete structures

A multifunctional all-FRP joint has been developed for the transfer of bending moments and shear forces in thermal insulation sections of concrete slab structures used in building construction. Tensile forces from moments are transferred by horizontal GFRP bars, while a pultruded cellular GFRP element transfers the compression forces. The shear forces are transferred by inclined GFRP bars and the webs of the GFRP element. The new joint considerably increases energy savings for buildings due to the low thermal conductivity of GFRP materials. The quasi-static behavior of the joint at the fixed support of cantilever beams was investigated. Two parameters were studied: shear- or moment-dominated loading mode and concrete strength. Results show that the all-FRP joint does not play a critical role at the ultimate limit state. Ductile failure occurs through concrete crushing. The GFRP bars lead to a significant improvement in joint performance compared with similar joints comprising steel bars. Higher concrete strength does not, however, significantly improve the ultimate load.     

Flexural and shear capacities of concrete beams reinforced with GFRP bars

This paper reports test results of 12 concrete beams reinforced with glass fibre-reinforced polymer (GFRP) bars subjected to a four point loading system. All test specimens had no transverse shear nor compression reinforcement and were classified into two groups according to the concrete compressive strength. The main parameters investigated in each group were the beam depth and amount of GFRP reinforcement. Two modes of failure were observed, namely flexural and shear. The flexural failure is mainly occurred due to tensile rupture of GFRP bars either within the mid-span region or under the applied point load. The shear failure is initiated by a major diagonal crack within the beam shear span. This diagonal crack extended horizontally at the level of the GFRP bars indicating bond failure.Simplified methods for estimating the flexural and shear capacities of beams tested are presented. The flexural capacity is estimated based on the compatibility of strains and equilibrium of forces. Comparisons between the flexural capacity obtained from the theoretical analysis and that experimentally measured in the current investigation and elsewhere show good agreement. To predict the shear capacity of the beams tested, four methods recently proposed in the literature for GFRP-reinforced concrete beams are used. These methods have been developed by modifying the ACI 318-99 shear capacity formula for steel-reinforced concrete beams to account for the difference in the axial stiffness of GFRP and steel bars. It has been shown that the theoretical predictions of the shear capacity obtained from these methods are inconsistent and further research needs to be carried out in order to establish a rational method for the shear capacity calculation of GFRP-reinforced concrete beams.     

Shear resistance mechanism and load-slip curve features of perfobond rib connectors during plastic stage

为保证单孔PBL连接件在塑性阶段仍具备较高的残余受剪承载力和较好的延性,对22组未设置贯通钢筋和21组设置贯通钢筋的单孔PBL连接件的荷载-滑移曲线进行了统计分析,研究了板厚不小于9mm的单孔PBL连接件进入塑性阶段后的受剪机理。在此基础上,根据荷载-滑移曲线的延性特征将其进行分类,并给出了判别条件。研究表明：单孔PBL连接件塑性阶段的残余受剪承载力由混凝土榫沿剪切破坏面的黏结力、侧向约束力提供的受剪承载力以及贯通钢筋的销栓作用组成。根据塑性阶段的侧向约束力情况,将单孔PBL连接件荷载-滑移曲线分为Ⅰ类、Ⅱ类与Ⅲ类曲线。可通过控制约束强度比,避免未设置贯通钢筋和设置贯通钢筋的单孔PBL连接件的荷载-滑移曲线出现延性较差的第Ⅲ类曲线,并可通过控制贯通钢筋比,避免设置贯通钢筋的单孔PBL连接件的荷载-滑移曲线出现经济性较差的第Ⅱ类曲线;可通过联合控制约束强度比和构造钢筋比,避免荷载-滑移曲线出现峰值点处荷载突变。     

Evaluation on the behavior of abutment-pile connection in integral abutment bridge

Integral abutment bridges can reduce the amount and cost of construction and maintenance work since they do not have expansion joints and shoes in order to increase stability and durability of the bridges’ system. Integral abutment bridges normally have single-row H-pile systems to resist the behaviors under service loading conditions such as thermal loading. In order to transfer member forces between abutments and H-pile, the abutment-pile connection in the integral abutment bridge should have rigid behavior. Therefore, the installation of reinforcing bars and minimum installed length of the piles in the concrete abutment are required to resist bearing force and deformation caused by shear forces and bending moments. This study examines the abutment-pile connections in the integral abutment bridge to improve the shear and bearing resistance of concrete abutment and constructability of abutment-pile connections for the single-row H-pile system with weak axis. Three types of new abutment-pile connections are proposed in this study. They feature transverse reinforcing bars perforated in H-pile, stud connectors, and perfobond rib connectors on the flange of H-pile, respectively. They are intended to increase the stiffness and strength so that they will better resist the bearing force caused by deformations and rotations at abutment H-pile concrete. Loading tests and FE analysis were conducted to evaluate the stiffness and behaviors of proposed connections for half scale abutment-H-pile connection specimens. From the test results, proposed abutment-H-pile connections were evaluated to secure sufficient stiffness, rotational stiffness, and bearing strength.     

重复荷载下高强钢筋与混凝土黏结性能的试验研究

随着预应力钢筋强度的提高及钢筋外形的变化,加之抗震设计必须考虑的黏结退化,钢筋与混凝土之间的黏结锚固问题愈显突出。通过光圆钢棒、异形钢棒和螺旋肋钢丝拉拔试件在重复荷载作用下的拔出试验,比较了3种不同外形高强预应力钢筋的黏结特性,研究了螺旋状预应力钢筋与混凝土界面间的黏结锚固机理,并讨论了影响黏结锚固性能的主要因素。根据试验结果,给出3种高强预应力钢筋在等幅重复荷载作用下的特征荷载值与应力水平上限的关系式。结果表明光圆钢棒在重复荷载作用下与混凝土的黏结性能较差;而异形钢棒和螺旋肋钢丝具有较好的黏结性能,且螺旋肋钢丝的黏结性能优于异形钢棒。研究成果为承受重复荷载的此种高强预应力钢筋混凝土结构的设计提供了依据。     

双层钢板混凝土组合剪力墙滞回性能研究

为研究双层钢板混凝土组合剪力墙的滞回性能,对4个剪跨比为2.5的组合剪力墙试件进行了拟静力加载试验;通过改变约束拉杆和加劲肋的间距,研究其在往复水平荷载作用下的破坏机理、滞回性能;选用地震分析软件OpenSees建立了双层钢板混凝土组合剪力墙的纤维模型,进行了低周反复荷载作用下的非线性分析。结果表明:该种剪力墙的破坏形态为墙底部截面钢板被压曲,核心混凝土被压碎的弯曲型破坏;在轴压比相同条件下,设置加劲肋试件的抗震性能优于设置约束拉杆的试件,且随着约束拉杆和加劲肋间距的减小,试件的变形能力增加,表现出较好的耗能能力;纤维模型计算得到的抗弯承载力、延性系数与试验值之间误差较小,纤维模型能较好地模拟剪力墙的抗震性能;随着轴压比的增大,剪力墙的极限承载力有所提高,而变形能力有明显的下降;随着混凝土强度的增加,剪力墙的承载力提高,变形能力减小;随着钢板厚度的增加,剪力墙的承载力和变形能力都明显增加。     

设置界面构造锚筋的新老混凝土粘结性能试验研究

新老混凝土良好结合是混凝土修补成功的关键,提出设置界面构造锚筋来增强新老混凝土粘结性能,通过采用劈拉试验和剪切试验综合分析有无构造锚筋的新老混凝土试件以及新、老混凝土整体试件的劈拉强度与抗剪强度特性。试验结果表明：无界面构造锚筋时新老混凝土水平粘结面试件的劈拉强度高于具有竖直粘结面的试件;采用构造锚筋的新老混凝土试件比不加锚筋试件的劈拉强度增长了24.1%;采用锚筋的新老混凝土试件的剪切破坏面均发生在结合面处,且试件两个结合面的剪切破坏不是同时产生;采用锚筋试件的剪切强度为无锚筋试件剪切强度的3.49倍,为新混凝土整体剪切试件强度的115.5%;构造锚筋能明显增强新老混凝土粘结性能。图10表4参10