钢筋混凝土平板的抗剪强度

本文指出双向平板的冲切问题与单向板的抗剪问题是平板抗剪问题的特殊情况。提出了无剪切钢筋的钢筋混凝土平板在仅传递剪力时,其抗剪强度的计算方法。     

Experimental investigation of edge restraint on punching shear behaviour of RC slabs

Current codes of practice usually do not consider the effect of edge restraint on the punching shear capacity of flat plate type reinforced concrete structures. As the punching shear provisions incorporated in various codes of practice are a direct result of the empirical procedures, they do not usually provide an accurate estimation of the ultimate punching load capacity of a slab with its edges restrained against rotation. This is because no account is taken of the enhancement of punching capacity due to the in-plane restraint in many types of reinforced concrete slab systems. A total of 16 model slabs with restrained and unrestrained edges have been tested in an effort to ascertain the influence of boundary restraint, thickness of the slabs on their structural behaviour and punching load-carrying capacity. Edge restraint has been provided by means of edge beams of various dimensions in order to mimic the behaviour of continuous slabs. The cracking pattern and load-deflection behaviour of the slabs tested have also been monitored closely.     

集中荷载下FRP筋混凝土双向板的冲切受力性能

通过对7块中置和偏置集中荷载作用下纤维增强材料(FRP)筋混凝土双向板的受力试验,研究荷载位置、混凝土强度、FRP筋用量等因素对板冲切受力性能的影响。结果表明:集中荷载位置、混凝土强度、FRP筋配筋率是影响FRP筋混凝土双向板冲切受力性能的重要因素。随着混凝土强度的提高和FRP筋配筋率的增大,同等荷载水平下的混凝土和FRP筋应变逐渐减小,开裂后混凝土应变的增长逐渐加快;混凝土强度对板的抗裂荷载和极限冲切承载力影响较大,FRP筋配筋率的影响相对较小;FRP筋混凝土双向板在中置和偏置集中荷载作用下的破坏属于脆性的局部冲切破坏。     

Dünnwandige,mikrobewehrte Betonbauteile unter Querkraftbeanspruchung

Shear strength of thin‐walled, micro‐reinforced concrete members Within the second funding period of the DFG Priority Programme 1542 ”Concrete Light“ investigations on the load‐bearing behavior of ”Ultra‐lightweight, Thin‐walled Tubular Concrete Members“ are carried out at the IBMB, division of concrete construction of the TU Braunschweig. Due to the currently insufficient amount of investigations dealing with the shear strength of micro‐reinforced concrete (ferrocement) members, fundamental studies had to be performed. These include experimental and theoretical investigations on the shear strength of profiled, thin‐walled concrete beams with micro‐reinforced webs. The performed tests showed the improved cracking behavior and failure notice of micro‐reinforced specimens, when compared to conventionally reinforced specimens. Furthermore, the conservative and thus secure estimation of the shear strength of micro‐reinforced beams using the design approaches provided by EC2+NA or ACI 318 is proven.     

Untersuchungen zum Durchstanzverhalten von Stahlbetonfundamenten

Investigations on the Punching Behaviour of RC Footings. The punching shear capacity of footings varies significantly for different codes. The amount of the soil reaction to be deducted from the punching load differs from one code to another. The aim of the present investigation is to derive an advanced design model for footings taking into account the soil‐structure‐interaction. The results of five punching tests on reinforced concrete footings supported on soil are presented. The experimental results indicate that the angle of the shear failure plane is steeper than observed by punching tests on flat slabs, and the shear slenderness seems to affect the punching shear capacity significantly. In order to reach a better insight of the load carrying capacity, nonlinear finite element simulations are performed. Based upon the findings and a test data bank an advanced design model is derived, which is based upon the DIN 1045‐1 provisions.     

钢筋钢纤维高强混凝土板冲切承载力

通过对6块尺寸为1 800 mm×1 800 mm×150 mm钢纤维高强混凝土板的冲切试验,研究混凝土强度等级和钢纤维体积率对板冲切极限承载力的影响。结果表明:钢纤维高强混凝土板冲切破坏之前的变形主要是弯曲变形,钢纤维的掺入提高了钢筋混凝土板的冲切承载力。在试验结果的基础上,运用统一强度理论和塑性极限分析方法,建立钢筋钢纤维高强混凝土板冲切极限承载力的计算公式。     

Effects of openings on the punching shear strength of RC flat‐plate slabs without shear reinforcement

Openings in RC flat‐plate slabs are one of the critical factors that influence the punching shear strength of the slab and determine its thickness in the vicinity of the slab‐column joint. This study experimentally investigates the effects of openings on the punching shear strength of flat‐plate slabs without shear reinforcement. Tests were performed on eight flat‐plate slab specimens considering the layout and number of openings as test variables. The failure characteristics of each specimen are examined, and the effects of the test variables on the punching shear strengths of the test specimens are investigated. The measured punching shear strengths of the test specimens are compared with the predictions of several concrete design codes, including the American Concrete Institute (ACI), Comité Euro‐International du Béton and Fédération Internationale de la Précontrainte (CEB‐FIP) model and fédération internationale du béton (fib) model codes. This indicates that the reductions in punching shear strength due to the existence of openings are generally proportional to the loss of effective critical sections, and an L‐shaped opening layout around the corner of the column may further reduce the punching shear strength and may contribute to the loss of effective critical sections due to the existence of openings. Copyright © 2015 John Wiley & Sons, Ltd.     

Punching shear strength of interior slab–column connections strengthened with carbon fiber reinforced polymer sheets

In this paper, punching shear strengthening of flat slabs using Carbon Fiber Reinforced Polymer (CFRP) sheets is studied. Fifteen specimens of reinforced concrete slabs were tested. Thirteen of them were strengthened by CFRP sheets and two specimens were kept as control specimens. Four of these strengthened specimens were tested under cyclic vertical loading. The width of CFRP sheets varied in different specimens. The CFRP sheets were located at the tension side of the slabs in two perpendicular directions. Vertical load was applied downward through a column stub using a hydraulic Jack. In all specimens, no rupture of CFRP sheets was observed. The test results showed that the use of CFRP sheet, in addition to steel reinforcing bars, as flexural reinforcement improves the punching shear strength of slabs. This improvement can be significant for the slabs made of high strength concrete and low steel reinforcement ratio. However, the improvement of punching shear strength due to FRP strengthening reduced under cyclic vertical loading. The test results were compared with the equations proposed by ACI 318 and BS 8110 Codes. The ACI Code underestimates the punching shear strength of slabs and this underestimation becomes more pronounced with the increase in the flexural reinforcement. The BS 8110 Code appropriately accounts for the effect of flexural reinforcement on punching shear strength of slabs. However, for the strengthened slabs, an equivalent reinforcement ratio should be used to include the effect of both steel and CFRP flexural reinforcement.     

基于抛物线形库仑-莫尔准则的钢筋混凝土板抗冲切承载力

在刚塑性冲切计算模型的基础上,采用二次抛物线形库仑 莫尔混凝土强度准则,运用虚功原理,建立考虑混凝土板中抗弯钢筋销栓作用的冲切承载力计算式。根据已有板冲切试验研究成果,如冲切角和破坏时刻抗弯钢筋应力等数据,对板冲切承载力计算式进行简化,给出简化计算式。与国内外混凝土板冲切试验数据进行计算比较后发现,简化计算式的计算结果较好地符合实测承载力;抗弯钢筋的销栓作用约占钢筋混凝土板总冲切承载力的6%～11%,而忽略抗弯钢筋的销栓作用会给计算结果带来较大影响。     

平板柱头抗冲切数值模拟和试验评估

采用非线性有限元法,对钢筋混凝土板冲切破坏建模。提出1种模拟冲切破坏的分析程序。通过1个大比例尺的无抗剪钢筋的钢筋混凝土板的冲切破坏试验,说明该程序的有效性。通过一组参数分析,得出影响板抗冲切能力的关键因素。该程序用于模拟在伦敦帝国理工大学进行的大比例尺混合钢筋混凝土平板的冲切破坏响应。试件包括1个管状钢柱柱头和1个ACI318结构钢柱头。分析结果基本可以预估剪切柱头对抗剪承载力的贡献,并且能评估现行的钢柱头的可靠性。     

考虑错动和转动复合影响的钢筋砼板的冲切承载力塑性解

本文用塑性极限方法对钢筋砼板的冲切承载力进行了研究。所采用的冲切破坏机构同时考虑了冲切锥与外围板之间的相对错动位移和转动位移的影响,比较符合实际的冲切破坏机理。得到的冲切承载力计算公式,形式简单,与试验结果较为符合,能反映出弯曲钢筋所作的贡献。     

部分预制装配型钢混凝土梁受力性能试验研究

结合国内外现有研究成果,提出部分预制装配型钢混凝土梁。结合2个系列7个梁试件的受弯性能静力试验及3个系列17个梁试件的受剪性能静力试验,对部分预制装配型钢混凝土（PPSRC）梁、空心部分预制装配型钢混凝土（HPSRC）梁的受弯性能以及处于正、负弯矩区段的部分预制装配型钢混凝土（PPSRC）梁和采用蜂窝型钢的部分预制装配型钢混凝土（PPCSRC）梁的受剪性能进行试验研究。结合与全现浇型钢混凝土（SRC）梁试件的比较分析,对制作方式、截面形式和现浇混凝土强度对PPSRC梁、HPSRC梁以及PPCSRC梁受力性能影响进行了分析。结果表明,文中提出的预制外壳能够很好地与现浇混凝土协同工作,浇筑方式及现浇混凝土强度对试件的承载力影响较小。基于试验结果提出适用于PPSRC梁及PPCSRC梁的实用抗剪公式,其计算结果与试验结果吻合较好。     

On the shear strength of reinforced concrete deep beam with web opening

An objective of this study is to establish the shear strength of reinforced concrete deep beam with web opening. Eighteen beams were tested with the variables of the steel ratio and strength of longitudinal bars, concrete strength, and shear span‐to‐depth ratio. It was observed that the opening is strengthened by longitudinal bars but the load‐carrying capacity of deep beams with openings can be largely improved by the increase in concrete strength. Modifying the softened truss model derived by Mau and Hsu and utilizing the results of this experiment carried out with the variables of concrete strength, cross‐section size, shear‐span‐to‐depth ratio, and the strength and steel ratio of longitudinal bars, this study proposes an improved model to predict the shear strength. Copyright © 2006 John Wiley & Sons, Ltd.     

折线螺旋束型布筋的PC框架边主梁的研究与设计

介绍了折线螺旋束型布筋的预应力混凝土框架边主梁及普通钢筋混凝土框架边主梁的对比荷载试验。试验数据分析表明,折线螺旋束型的预应力筋可以有效地提高边主梁的开裂扭矩,在出现斜裂缝后预应力抗扭筋仍然可以有效地工作。给出了折线螺旋束型布筋的预应力梁的抗扭极限承载力的计算公式,并通过工程实例,提出一种在框架边主梁中设置折线螺旋束型的预应力筋以承受次梁传来的协调扭矩的设计方法。     

Strengthening of reinforced concrete beams in shear by the use of externally bonded steel plates: Part 2 – Design guidelines

Existing concrete structures may require strengthening or stiffening in order to increase their structural performance. One method for providing this enhanced capacity is to adhesively bond steel plates to the concrete surface. The results from experimental tests conducted to investigate the transfer of stress through a steel–concrete adhesive bond by Barnes and Mays [The transfer of stress through a steel to concrete adhesive bond. Int J Adhes Adhes 2001;21:495–502] combined with the shear strengthening and testing to failure of 30 reinforced concrete beams (Part 1 of this paper) was examined. By combining the results from each section of work, values for shear crack angle, effective anchorage length and mean shear stress levels in strengthened reinforced concrete beams were determined. These values were then used to develop a design method. This method can be used to determine the contribution to shear strength of continuous externally bonded steel plates in both rectangular and ‘T’ section reinforced concrete beams.     

钢骨混凝土梁抗剪性能试验研究

通过3根钢骨混凝土梁和1根普通钢筋混凝土梁在单点集中荷载作用下的抗剪性能试验,研究了桁架式钢骨混凝土梁的斜截面破坏形态和抗剪承载力。试验结果表明:与普通钢筋混凝土梁相比,钢骨梁的开裂荷载和抗剪承载力都有较大的提高;在相同钢骨形式下,随着剪跨比减小,钢骨梁的极限抗剪承载力增大;加入水平分布筋后,延缓了剪区斜裂缝的开展,提高了钢骨混凝土梁的极限抗剪承载力。     

钢纤维钢筋混凝土无粘结部分预应力扁梁柱节点设计方法的研究

在四个扁梁柱节点试验的基础上,本文通过理论推导,得到一套考虑节点内、外核心区内的钢纤维和扁梁中配有的无粘结预应力筋作用的扁梁柱节点内、外核心区的设计方法;该方法充分利用了节点内、外核心区混凝土的强度,正确考虑了柱轴压力的作用,仔细检查了节点的竖向抗剪能力;所提出的设计方法的可靠性得到试验数据的验证.     

钢筋混凝土板柱节点受冲切承载力计算方法分析

钢筋混凝土板柱节点受冲切承载力是目前板柱结构存在的突出问题,对确保此类结构的安全性至关重要。在国内外大量研究的基础上,回顾了国内外学者提出的板柱节点受冲切承载力模型理论的发展过程,重点阐述了桁架模型、临界剪切裂缝理论、塑性理论、切向应变理论和临界截面应变理论等。针对板柱节点受冲切承载力的几种典型计算方法,深入分析了混凝土强度、板有效高度、配筋率、纵筋屈服强度和柱边长等参数对板柱节点受冲切承载力的影响,并利用试验数据分析了各种计算方法的适用性及局限性,提出对板柱节点受冲切承载力计算方法的认识并阐述其发展方向。     

轻骨料混凝土无腹筋梁受剪性能试验研究

为研究骨料种类对无腹筋梁受剪性能的影响,以剪跨比和纵筋配筋率为变量,进行了16根集中荷载作用下的无腹筋混凝土简支梁受剪性能试验,其中8根采用普通碎石混凝土,8根梁采用页岩陶粒（轻骨料）混凝土,对轻骨料和普通混凝土梁的裂缝发展、破坏形态、斜向开裂荷载、受剪承载力、跨中挠度、裂缝面相对位移等进行了观察和测量。对比分析表明：轻骨料混凝土梁的斜向开裂荷载和受剪承载力均低于普通混凝土梁,其裂缝面较普通混凝土的更加光滑;将轻骨料混凝土梁受剪承载力试验值与采用我国JGJ 12-2006《轻骨料混凝土结构技术规程》和美国规范ACI 318-11、加拿大规范CSA 23.3-04、欧洲规范EC 2方法的计算值进行对比分析,结合此次试验结果和从国内外文献中搜集的126组已有试验数据,对我国JGJ 12-2006的受剪承载力公式的准确性和安全性进行探讨,提出了无腹筋轻骨料混凝土梁受剪承载力计算的建议公式。     

玻璃纤维布加固的钢筋混凝土梁端部粘结剪应力试验研究及端部应力分析

进行了 7根玻璃纤维布加固的钢筋混凝土梁剥离试验研究。试验结果表明 ,玻璃纤维布加固的钢筋混凝土梁抗弯承载力显著提高 ,发生剥离破坏的试验梁极限荷载相对地有所降低。根据试验结果 ,建立了纤维布端部粘结剪应力的试验分析方法 ,并对粘结剪应力的分布进行了分析。建立了纤维布端部粘结剪应力、剥离正应力及剥离荷载的计算方法 ,分析了参数对剥离荷载的影响 ,并给出了简化计算公式。