螺栓灌胶节点对螺栓钢板加固钢筋混凝土连梁抗震能力影响的试验

为了提高小跨高比既有连梁的抗震性能,提出了一种新型的螺栓钢板加固法和一种新型的钢板屈曲控制装置。按照1∶2比例制作3个钢筋混凝土连梁试件,通过低周往复荷载试验研究了螺栓灌胶节点对钢板加固钢筋混凝土连梁的影响。结果表明:未采用螺栓钢板法加固的连梁呈现出脆性剪切破坏;采用螺栓钢板法进行普通高强螺栓加固的连梁,其强度和延性并没有提高;采用螺栓钢板法进行螺栓灌胶节点加固的连梁,其强度、延性和耗能能力得到大幅度提高。     

Experimental study of plate‐reinforced composite deep coupling beams

An experimental study was conducted to investigate the behavior of deep coupling beams of span‐to‐depth ratio (1·17) fabricated according to the newly proposed plate‐reinforced composite (PRC) coupling beam design. Three PRC coupling beams of small span/depth ratio fabricated based on different approaches for load transfers between steel plates and reinforced concrete (RC) were tested under reversed cyclic loading. This paper presents the experimental results and compares the overall performance of these three specimens with two geometrically identical RC coupling beam specimens, one with diagonal reinforcement and the other with conventional reinforcement details, tested by previous researchers. It was found that the performance of PRC deep coupling beams of small span‐to‐depth ratio with properly designed plate anchorage in the wall regions can be comparable to that of diagonally reinforced coupling beams while being able to achieve a higher shear capacity without causing the problem of steel congestion. The proper design approach for the plate anchorage of PRC coupling beams was also identified. Copyright © 2007 John Wiley & Sons, Ltd.     

Behaviour of embedded steel plate in composite coupling beams

Plate-reinforced composite (PRC) coupling beam is fabricated by embedding a vertical steel plate into a conventional-reinforced concrete coupling beam to enhance its strength and ductility. Shear studs are welded on the steel plate surfaces to allow for proper load transfer between the concrete and steel plate. The present study focuses on the evaluation of internal load distributions and load sharing on the embedded steel plate as well as at the shear studs in composite coupling beams using the nonlinear finite element package ATENA. The proposed two-dimensional finite element model is able to simulate the overall load-deflection behaviour and internal load distributions of coupling beams subjected to bending and shear forces. The reliability of the model is demonstrated by comparisons with the available experimental results. This is followed by an extensive and carefully planned parametric study using the calibrated finite element model. Numerical results on the effects of steel plate geometry, span-depth ratio of beams and steel reinforcement ratios at beam spans and in wall regions are presented and discussed in this paper. The finite element model provides a better understanding of the behaviour of shear studs as well as plate anchorage in the wall regions and embedded beam region. Based on the numerical results, equations for quantifying the shear stud forces are established and a set of non-dimensional design charts for determining the internal forces of the embedded steel plates is constructed. Both of them are useful for engineers to design PRC coupling beams.     

考虑混凝土贡献的修正变角桁架模型

为提高有腹筋RC（钢筋混凝土）浅梁抗剪承载力的预测准确性和稳定性,提出一种考虑混凝土贡献的修正变角桁架模型。首先,基于变角桁架模型得到箍筋的抗剪贡献值计算公式,并结合塑性下限定理确定斜裂缝倾角的取值|其次,通过混凝土浅梁受压区的劈裂破坏模式得到混凝土项的抗剪贡献值计算公式,并利用尺寸效应系数考虑了混凝土项的脆性破坏特征|最后,将箍筋项和混凝土项提供的抗剪承载力进行叠加,建立有腹筋RC浅梁抗剪承载力计算公式。基于有腹筋RC浅梁抗剪承载力试验数据库ACI-DAfStb对本文、GB50010、ACI及AASHTO规范中抗剪计算公式的预测准确性进行对比评估,结果表明：文中抗剪承载力公式不仅能够体现配筋率、剪跨比和混凝土强度等主要抗剪参数的影响规律,还能考虑尺寸效应和斜裂缝倾角对抗剪承载力的修正|同时,在抗剪承载力预测准确性和稳定性方面,相对规范方法有所较高。     

Experimental study on shearing capacity of concrete beams longitudinal reinforced with steel fiber composite bars and BFRP bars

为了研究纵筋分别采用钢-纤维复合筋（SFCB）和玄武岩纤维复合筋（BFRP筋）的混凝土梁受剪性能，以普通钢筋混凝土梁作为对比，设计并开展了46根梁的受剪承载力试验，变化参数为剪跨比、纵筋配筋率和有无箍筋。试验结果表明:三种纵筋梁的受剪承载力均随着剪跨比的减小而增大；SFCB梁的受剪承载力随着纵筋配筋率的增大也增大。此外，提出广义销栓作用影响系数的概念，推导其计算式，用于评价复合纵筋和玄武岩纵筋对混凝土梁受剪承载力的贡献，并据此建立受剪承载力计算式。经与国内外共223组混凝土梁(纵筋为钢筋、BFRP筋和SFCB等)受剪试验数据对比，验证所提广义销栓作用受剪承载力计算式的正确性。在此基础上，采用与钢筋混凝土梁受剪承载力规范公式相近的安全度，建议了适用于纵筋为复合筋和玄武岩筋的混凝土梁受剪承载力设计公式。     

薄壁U形钢板加固受火后钢筋混凝土梁受力性能研究

采用外套薄壁U形钢板、内灌无收缩灌浆料加固受火后钢筋混凝土梁,该加固技术能有效避免灌浆材料脱落,具有长效的加固功能。为验证该加固方法的有效性,进行了14根混凝土梁的静载试验,研究了U形钢板厚度和受火时间对加固RC梁受弯性能的影响,以及U形钢板厚度和剪跨比对加固RC梁受剪性能的影响。借鉴常温下组合梁承载力的计算方法,给出了薄壁U形钢板加固受火后RC梁受弯和受剪承载力的计算公式。结果表明：受火1.0、1.5h后混凝土梁的受弯承载力分别降低了9.4%、10.4%,剪跨比为1.74、2.58的混凝土梁受火1.5h后受剪承载力分别降低了19.5%、10.6%。薄壁U形钢板加固受火后RC梁的受弯、受剪承载力相比未受火RC梁分别提高了127.4%~151.7%、21.3%~56.7%。在薄壁U形钢板内侧和上翼缘焊接角钢形成的内隔环能保证薄壁U形钢板和混凝土共同工作,加固后试件可作为完全剪切连接的组合梁。加固试件发生受弯破坏时内隔环承受的纵向剪力较大,而发生受剪破坏时内隔环承受的纵向剪力较小。     

钢-纤维复合纵筋和玄武岩纤维复合纵筋混凝土梁受剪承载力试验研究

为了研究纵筋分别采用钢-纤维复合筋(SFCB)和玄武岩纤维复合筋(BFRP筋)的混凝土梁受剪性能,以普通钢筋混凝土梁作为对比,设计并开展了46根梁的受剪承载力试验,变化参数为剪跨比、纵筋配筋率和有无箍筋。试验结果表明：三种纵筋梁的受剪承载力均随着剪跨比的减小而增大;SFCB梁的受剪承载力随着纵筋配筋率的增大也增大。此外,提出广义销栓作用影响系数的概念,推导其计算式,用于评价复合纵筋和玄武岩纵筋对混凝土梁受剪承载力的贡献,并据此建立受剪承载力计算式。经与国内外共223组混凝土梁(纵筋为钢筋、BFRP筋和SFCB等)受剪试验数据对比,验证所提广义销栓作用受剪承载力计算式的正确性。在此基础上,采用与钢筋混凝土梁受剪承载力规范公式相近的安全度,建议了适用于纵筋为复合筋和玄武岩筋的混凝土梁受剪承载力设计公式。     

外粘整块钢板加固钢筋混凝土梁受剪试验研究

通过 1 1根混凝土强度等级为C1 4的简支梁试件在集中荷载作用下的试验研究 ,得到外粘整块钢板后梁的受剪承载力。随粘钢规格的不同 ,粘钢混凝土梁发生不同的破坏形态。根据试验结果 ,建立了粘钢部分承担的受剪承载力理论计算公式和受剪斜截面限制条件。     

细晶粒高强钢筋混凝土梁受弯性能试验与参数分析

为研究配置了细晶粒高强钢筋混凝土梁的受弯性能,制作了HRBF400、HRBF500级钢筋混凝土矩形截面梁各4根进行静力抗弯试验。研究表明HRBF筋混凝土梁在短期荷载作用下的最大裂缝宽度实测值满足规范要求,但计算值不满足。HRBF400级钢筋混凝土梁在正常使用条件下的挠度能满足规范要求,HRBF500级钢筋混凝土梁不能够满足规范要求。推导了HRBF筋混凝土梁在裂缝/挠度控制条件下的承载力计算公式,提出了构件承载力利用系数的概念,分析了钢筋强度、钢筋直径、混凝土强度、配筋率、混凝土保护层厚度、高跨比对构件承载力利用系数的影响。在经济配筋率范围内,HRBF筋混凝土梁的延性基本满足要求。HRBF筋混凝土梁的耗能能力在较低配筋率时与普通钢筋混凝土梁相近,但随着配筋率的提高,其耗能能力较普通钢筋混凝土梁降低的快。同配筋率下,HRBF筋混凝土梁在弹性阶段的耗能能力较普通钢筋混凝土梁要高,且随着配筋率的增大而提高。     

Strengthening of RC beams in shear using GFRP inclined strips – An experimental study

Though there have been a number of studies on shear strengthening of RC beams using externally bonded fiber reinforced polymer sheets, the behaviour of FRP strengthened beams in shear is not fully understood. This is partly due to various reinforcement configurations of sheets that can be used for shear strengthening and partly due to different failure modes a strengthened beam undergoes at ultimate state. Furthermore, the experimental data bank for shear strengthening of concrete beams using FRP remains relatively sparse due to which the design algorithms for computing the shear contribution of FRP are not yet clear. The objective of this study is to clarify the role of glass fiber reinforced polymer inclined strips epoxy bonded to the beam web for shear strengthening of reinforced concrete beams. Included in the study are effectiveness in terms of width and spacing of inclined GFRP strips, spacing of internal steel stirrups, and longitudinal steel rebar section on shear capacity of the RC beam. The study also aims to understand the shear contribution of concrete, shear strength due to steel bars and steel stirrups and the additional shear capacity due to glass fiber reinforced polymer strips in a RC beam. And also to study the failure modes, shear strengthening effect on ultimate force and load deflection behaviour of RC beams bonded externally with GFRP inclined strips on the shear region of the beam.     

Formulation of shear strength of slender RC beams using gene expression programming,part I: Without shear reinforcement

In this study, a new design equation is derived to predict the shear strength of slender reinforced concrete (RC) beams without stirrups using gene expression programming (GEP). The predictor variables included in the analysis are web width, effective depth, concrete compressive strength, amount of longitudinal reinforcement, and shear span to depth ratio. A set of published database containing 1942 experimental test results is used to develop the model. An extra set of test results which is not involved in the modeling process is employed to verify the applicability of the proposed model. Sensitivity and parametric analyses are carried out to determine the contributions of the affecting parameters. The proposed model is effectively capable of estimating the ultimate shear capacity of members without shear steel. The results obtained by GEP are found to be more accurate than those obtained using several building codes. The GEP-based formula is fairly simple and useful for pre-design applications.     

钢纤维混凝土无腹筋梁抗剪强度的回归分析

通过对大量试验结果的回归分析 ,总结了剪跨比、混凝土强度、钢纤维含量和纵筋配筋率对钢纤维混凝土无腹筋梁抗剪强度的影响 ,并指出这些因素在影响程度上的不同 .分析结果表明 ,剪跨比对钢纤维混凝土无腹筋梁抗剪强度的影响最大 .提出了预测钢纤维混凝土无腹筋梁抗剪强度的回归计算公式 .     

锈蚀钢筋混凝土梁抗弯承载力计算方法

目前对锈蚀钢筋混凝土梁抗弯承载力的研究主要考虑锈蚀程度的影响,忽视了构件本身参数不同对承载力退化的影响,导致不同学者提出的锈蚀钢筋与混凝土的协同工作系数差异较大。为合理评估既有锈蚀钢筋混凝土梁的剩余承载力,首先对锈后无黏结钢筋混凝土受弯构件进行模拟试验与有限元分析,系统分析严重锈蚀混凝土构件钢筋应力水平的主要影响因素,发现截面配筋指标可综合反映混凝土强度和截面配筋率对受拉钢筋应力水平的影响,并确定基于截面配筋指标的锈后无黏结混凝土梁受拉钢筋强度利用系数;对一般锈蚀钢筋混凝土梁抗弯承载力的退化机理进行深入分析,综合考虑钢筋锈蚀程度和截面配筋指标的影响,建立一般锈蚀混凝土梁钢筋强度利用系数计算公式;提出概念明确、通用性强的锈蚀钢筋混凝土梁抗弯承载力计算方法;与大量的试验结果进行对比验证,计算方法的吻合性较好。     

矩形开孔钢筋混凝土伸臂梁受剪性能试验研究

为方便设备管线通过,采用腹部开孔梁可有效降低楼层高度,但开孔会削弱梁的整体刚度,导致孔洞附近的应力及内力重分布十分复杂。为研究腹部矩形开孔的钢筋混凝土伸臂梁的受力性能,以正反弯矩比、孔洞位置、剪跨比及孔侧斜筋作为主要变量,对12根钢筋混凝土开孔伸臂梁和1根钢筋混凝土实腹伸臂梁试件进行了两点加载下的受剪性能试验。研究了各种参数对开孔伸臂梁的裂缝开展及破坏形态、应变分布、变形和受剪承载力等受力性能的影响。试验结果表明：正反弯矩比和孔心剪跨比改变了伸臂梁在孔洞附近的受力状态,导致破坏时孔侧呈现出不同的裂缝形态。配置孔侧斜筋后,孔侧混凝土和箍筋更好地发挥协同抗剪作用,试件的受剪承载力显著提高,裂缝开展和变形均得到有效的控制。利用混凝土开孔简支梁发生孔侧剪压破坏的受剪承载力公式对开孔伸臂梁的受剪承载力进行计算,并和试验数据进行对比可知,按开孔简支梁的算式对开孔伸臂梁的受剪承载力进行计算,计算结果与试验结果的平均比值为0.96,方差为0.07,结果偏于安全。     

混杂纤维HPC深梁受剪承载力计算方法

采用正交试验法设计钢聚丙烯混杂纤维高性能混凝土(简称HPC)深梁试件,通过静力试验研究混杂纤维HPC深梁受剪承载力计算方法。正交试验中考虑的因素主要有钢纤维特征参数(类型、体积率、长径比)、聚丙烯纤维体积率、水平及竖向分布钢筋配筋率等。结果表明:混杂纤维能改变无腹筋HPC深梁的受剪破坏形态;混杂纤维的掺入使得HPC深梁的剪切初裂强度和抗剪极限强度明显提高,其平均提高幅度分别为45.2%和25.6%。将塑性理论应用于混杂纤维HPC深梁受剪承载力计算得到了很好的结果,分析表明水平及竖向分布钢筋配筋率的大小对混杂纤维HPC深梁抗剪强度的影响不显著,但水平分布钢筋的作用大于竖向分布钢筋。分析了混杂纤维的增强机理,提出了基于"拉杆拱"模型和劈裂破坏计算模式的混杂纤维HPC深梁受剪承载力计算式。     

Prediction of shear strength of steel fiber RC beams using neural networks

This paper presents the development of artificial neural network models for predicting the ultimate shear strength of steel fiber reinforced concrete (SFRC) beams. Two models are constructed using the experimental data from the literature and the results are compared with each other and with the formula proposed by Swamy et al. and Khuntia et al. It is found that the neural network model, with five input parameters, predicts the shear strength of beams more closely than the network with four input parameters. Moreover, the neural network models predict the shear strength of SFRC beams more accurately than the above-mentioned formulas. Further, the accuracy of predicted results is found not biased with concrete strength, shear span to depth ratio and the beam depth. Limited parametric studies show that the network model captures the RC beam’s underlying shear behavior very well.     

配置600MPa高强钢筋混凝土梁跨中挠度试验研究及计算方法

为研究配置600MPa高强钢筋混凝土梁的跨中挠度及其计算方法,设计了6组12根受弯梁,主要变化参数为配筋率和混凝土强度,对其进行静力受弯试验。分析了正常使用阶段各级荷载下的截面高度方向混凝土应变与纵向受力钢筋应变、荷载-跨中挠度全过程曲线等。试验结果表明：配置600MPa级高强钢筋的混凝土梁混凝土的应变变化符合平截面假定,荷载-跨中挠度全曲线为三折线。基于已有的配置335、400、500MPa钢筋混凝土梁的跨中挠度试验结果的分析,结合600MPa试验研究,对国内外现行的规范中钢筋混凝土梁跨中挠度计算公式的适用性进行了比较分析,表明现行规范公式适用于配置335~400MPa钢筋的混凝土梁。建立了适用于配置不同强度(335~600MPa)钢筋及不同强度(C40~C60)混凝土梁跨中挠度的统一计算方法。     

The composite effect of steel fibres and stirrups on the shear behaviour of beams using self-consolidating concrete

Based on the investigation of the influence of steel fibre on the workability of fresh self-consolidating concrete (SCC), this paper presents the experimental results carried out on a series of simply supported SCC rectangular beams, using steel fiber reinforcement with and without stirrups, and subjected to four-point symmetrically placed vertical loads. The major test variables are the steel fibre content and stirrup ratios. The current study on the shear strength of conventional reinforced concrete (RC) beams verifies the shear strength of SCC beams with steel fibres. The investigation indicates that the shear strength significantly increases by increasing the fibre content; the addition of steel fibres in an adequate percentage can change the failure mode from a brittle shear collapse into a ductile flexural mechanism. The stirrups can be partially replaced by steel fibres. The combination of steel fibres and stirrups demonstrates a positive composite effect on the mechanical behaviour. The shear strength recorded experimentally is compared with the value obtained from the proposed formula, and the correlation is satisfactory.     

基于试验数据的高强混凝土梁抗剪承载力计算方法Ⅰ.无腹筋梁

为了研究高强混凝土无腹筋梁抗剪承载力的计算方法,收集国内外关于高强混凝土无腹筋梁抗剪试验的抗剪承载力、混凝土强度、剪跨比、截面有效高度、受拉纵筋配筋率等试验数据,整理成包含291组数据的数据库。利用数据库中的实测数据对中国《混凝土结构设计规范》（GB 50010—2010）、美国混凝土结构设计规范ACI 31-14和Zsutty提出的混凝土梁抗剪承载力公式用于高强混凝土梁的适用性进行评价,并分情况进一步研究中国规范公式,修正中国规范公式中的参数,得到一个新的公式。结果表明:3个公式用于高强混凝土梁时,Zsutty公式的预测结果最精确,中国规范公式的预测结果准确性次于Zsutty公式但好于美国规范公式;所得出的新公式较原规范公式更加适用于高强混凝土无腹筋梁。     

基于粘结强度变化的锈蚀无腹筋梁承载能力的研究

基于锈蚀钢筋混凝土梁内钢筋与混凝土间粘结强度随锈蚀量的变化,对锈蚀梁承载能力和破坏模式进行了研究。首先,基于梁内粘结强度的变化,计算锈蚀梁的抗弯承载力。其次,基于“拉、剪临界破坏”的概念和“梁-拱”共同作用的混凝土抗剪抵抗机制,计算锈蚀无腹筋梁的抗剪承载力。较小钢筋锈蚀量时,与粘结强度有关的“梁作用”因粘结强度的增加而增加;随锈蚀量的增加和粘结强度的退化,与粘结强度有关的“梁作用”不断降低,“拱作用”则有所增加。再次,对锈蚀梁随钢筋锈蚀量变化破坏模式的变化进行了分析。最后,对文中提出的模型进行了试验验证。