压型钢板-混凝土组合楼板纵向受剪承载力试验研究

针对组合楼板主要的破坏模式——纵向剪切破坏进行分析,对8块U76型压型钢板-混凝土组合楼板进行了静力试验。试验结果表明:组合板越厚、剪跨越小、剪力横向钢筋越多,组合板纵向受剪承载力就越高。通过与无栓钉组合板的试验结果比较分析,表明组合板中剪跨区的栓钉,能极大地提高受剪承载力;并通过试验得到组合板的荷载-纵向相对滑移关系曲线图,采用欧洲规范4的建议公式,以试验数据为依据,回归得出组合楼板的剪力粘结系数m、k,为该种楼板的工程设计提供参考依据。     

Analysis of longitudinal shear behaviour for composite steel and concrete slabs

The strength of composite slabs depends mainly on the strength of contact between the steel sheeting and concrete. In the article a method of analyses for strength of the horizontal section of the composite slabs based on the theory of built-up bars, which gives one an opportunity to assess strength and the rigidity of contact is presented. The proposed method evaluates the influence of both plastic deformations of the concrete layer and cracks in the concrete on the rigidity of this layer and of the whole slab as well. Performed investigations in deformations and strength of the contact between steel sheeting and concrete allowed one to explore the behaviour of the contact from the start of loading up to the failure. During contact testing, influence of pre-compression forces on deformations and strength of the contact were investigated. The strength of horizontal section in 6 fragments of composite slab with ‘Holorib’ type profiled steel sheeting was investigated experimentally. In tests the thickness of concrete layer of the slab and concrete strength varied. Theoretical calculations for the strength of a horizontal section of experimental slabs were made in this investigation. Calculations were performed according to the method proposed by us with the application of the method of built-up bars. In calculations, rigidity of the contact between steel profiled sheeting and concrete as well as equivalent rigidity of a concrete layer with cracks were evaluated. Experimental and theoretical results of the strength of the horizontal section in composite slabs were compared. Comparison of results revealed that their agreement was sufficiently good.     

考虑剪切效应的钢筋混凝土厚板的纵向裂缝研究

试验表明,钢筋混凝土简支厚板在中置集中荷载作用下的双向弯曲很明显.特别是当板的宽跨比较大、集中荷载的面积较小时,其双向作用更为明显.按常规设计,往往只计算Mx方向配筋,而My方向则按构造配筋.因此,工程上经常出现沿板跨度方向的裂缝,即板的纵缝,并且由于My方向配筋过少,板纵向裂缝的宽度远大于横向裂缝的宽度.本文首先对简支厚板在集中荷载下的裂缝形态进行了试验研究,然后,将厚壳单元引入板的有限元分析,进而讨论了钢筋混凝土双向厚板的剪跨比、厚宽比、宽跨比对板横纵向弯矩比值的影响,提出了适用于控制不同厚度的厚板纵缝的纵向弯矩比简化计算公式,为设计提供参考.     

钢筋局部钢纤维高强混凝土板冲切挠度计算

根据钢筋局部钢纤维高强混凝土冲切板的试验结果,讨论了钢纤维体积率、钢纤维掺加范围和混凝土强度对试验板冲切变形的影响,建立了试验板开裂荷载及荷载—挠度曲线上升段挠度计算公式,并进行了数值计算.结果表明,钢纤维的掺入对钢筋高强混凝土板冲切变形性能的改善比较显著;试验板挠度计算值与试验值吻合较好.     

Capacities of headed stud shear connectors in composite steel beams with precast hollowcore slabs

In steel-concrete composite beams, the longitudinal shear force is transferred across the steel flange/concrete slab interface by the mechanical action of the shear connectors. The ability of the shear connectors to transfer these longitudinal shear forces depends on their strength, and also on the resistance of the concrete slab against longitudinal cracking induced by the high concentration of shear force. Most of the research in composite construction has concentrated on the more traditional reinforced concrete and metal deck construction, and little information is given on shear capacity of the headed studs in precast hollowcore slabs. In this paper, a standard push test procedure for use with composite beams with precast hollowcore slabs is proposed. Seven exploratory push tests were carried out on headed studs in solid RC slabs to validate the testing procedures, and the results showed that the new test is compatible with the results specified in the codes of practice for solid RC slabs. Once a standard procedure is established, 72 full-scale push tests on headed studs in hollowcore slabs were performed to determine the capacities of the headed stud connectors in precast hollowcore slabs and the results of the experimental study are analysed and findings on the effect of all the parameters on connectors’ strength and ductility are presented. Newly proposed design equations for calculating the shear connectors’ capacity for this form of composite construction are also be given.     

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.     

New evaluation and modeling procedure for horizontal shear bond in composite slabs

A new method for modeling the horizontal shear bond in steel deck-concrete composite slabs is proposed. The method considers the slab slenderness as the strength parameter that affects the accuracy of horizontal shear bond modeling. A calculation procedure called the Force Equilibrium method is developed to generate shear bond stress versus end slips relationship (shear bond property) from bending tests. An interpolation procedure is also presented to estimate the shear bond property curves for slabs of varying slenderness using two sets of bending test data. The shear bond property curves are applied to connector elements of finite element models to model the horizontal shear bond behavior in composite slabs. The results of this study show that the shear bond of composite slabs under bending varies with the slenderness parameter, and hence influences the slab strength and behavior, as well as affecting the accuracy of the finite element analyses. The finite element analyses conducted on slabs with different slenderness utilizing a single shear bond property, which are not varied according to the slenderness parameter, may lead to either safe or unsafe results, depending on the geometry of the slabs.     

按部分剪力连接计算压型钢板-混凝土组合板承载力的简化方法

提出多种荷载作用下,简支压型钢板-混凝土组合板承载力的部分剪力连接简化计算方法。分析组合板纵向剪切破坏的部分剪力连接理论模型,阐明组合板纵向剪切破坏的机理,以及控制截面位置和极限荷载的求解思路。通过公式推导,分别得到了组合板在两点对称荷载和均布荷载作用下的承载力计算公式。在此基础上,提出点荷载和均布荷载共同作用下的组合板承载力计算方法,通过参数分析,对该方法进行简化,得到多个荷载作用下组合板承载力的简化计算公式。结合12个简支组合板的静力试验结果,进行公式验证,计算结果与试验值吻合良好。通过小比例滑块试验得到压型钢板与混凝土的界面强度参数,即可用该方法计算组合板的承载力。     

装配式剪力墙结构住宅叠合板精细化设计探讨

在装配式剪力墙结构住宅中,叠合板的应用非常广泛,技术也日趋成熟.住宅高质量发展及装配化精益建造等新需求对装配式建筑设计也提出了更高的要求.针对叠合板常见的预制底板接缝、局部降板等设计内容,在工程实践经验总结的基础上,以提高建造全过程的标准化、易建性与经济性等为目标,在叠合板的技术策划、设计选型、接缝形式及接缝宽度确定、复杂叠合板补充有限元计算分析及构造措施等方面提出了相关的精细化设计方法.实践证明该精细化设计方法是有效的、可行的,可供同类工程的设计参考借鉴.     

纵筋配筋率变化时十字形短肢剪力墙弹塑性分析

运用FORTRAN语言编写非线性分析程序,对5个钢筋混凝土十字形短肢剪力墙结构进行单调荷载作用下的弹塑性分析,比较了纵筋配筋率变化时,剪力墙的承载能力、刚度和延性变化情况,分析结果表明,随纵筋配筋率的提高,结构的承载力有所提高,而延性在一定范围有所降低,结构设计中应充分考虑该因素的特殊性,同时考虑承载力和变形能力的变化。     

水泥复合砂浆钢筋网应用于抗剪加固钢筋混凝土梁技术

用水泥复合砂浆钢筋网加固钢筋混凝土构件,是一种新的加固方法,该方法施工简单,施工便捷,施工工效高,湿作业少,不需大型施工机具,施工占用场地少,施工质量容易保证,经济效益好,价格便宜,具有极佳的耐腐蚀性能、耐久性能和耐火性能,适用面广,可以广泛地适用于各种类型、各种形状、各种结构部位的加固修补,其本身可以起到对内部混凝土结构的保护作用,达到双重加固修补的目的,节省了大笔维修费用,而且解决了碳纤维加固中因使用有机界环氧化物而产生的问题.试验表明水泥复合砂浆钢筋网能改善梁的抗剪性能,加固效果良好.总结和讨论了水泥复合砂浆钢筋网抗剪加固钢筋混凝土梁的施工工艺及质量控制.     

钢-超高性能混凝土组合板冲切性能试验研究和承载力计算

钢-超高性能混凝土(UHPC)组合板是将钢板与UHPC通过连接件组合成整体,具有高强、高延性、抗开裂、施工便利等特性,可应用于桥面板、防护工程等结构中.由于钢-UHPC组合板相对较薄且往往承受集中荷载,因此需要对其抗冲切性能进行重点研究.通过变化连接件参数、UHPC厚度、钢板厚度和加载区边长,完成了14块板件在集中荷载...     

轻骨料预应力混凝土板冲切强度的研究

鉴于我国规范对轻骨料预应力混凝土板冲切强度计算未作明确规定,根据所进行的轻骨料(珍珠岩系人造轻骨料ASL)预应力混凝土板冲切特性试验结果,对我国现用规范计算公式的结果精度进行了评估。并结合文献资料对国外研究者已提出的预应力混凝土板计算方法进行了评估完善,提出了符合设计实践的轻骨料预应力混凝土板冲切强度的计算模式。     

Modelling of heated composite floor slabs with reference to the Cardington experiments

This paper describes a method of modelling composite floor slabs in fire conditions using a stress-resultant approach. The FEAST suite, which consists of two main computer programs is described. The first, SRAS, is designed to model the behaviour of arbitrary orthotropic plate sections at elevated temperatures. The second program, FEAI, interfaces with the finite element package ABAQUS, allowing realistic models of the behaviour of whole structures in fire conditions to be obtained. The paper describes how SRAS was used to analyse the floor slab of the Cardington fire tests and results showing the behaviour of the slab under a variety of loading conditions are presented. The suitability of FEAI as a key component in the analysis of redundant structures under fire conditions is briefly demonstrated.     

Punching shear tests on flat concrete slabs exposed to fire

Underground parking structures often consist of flat slabs connected by columns, for which punching shear is often the most critical design criterion. In fire conditions, the punching load can increase due to restraint of the thermal curvature of the slab or due to the expansion of the columns. This increase of the punching load is discussed in the paper by means of a literature review. On the other hand, during fire the punching resistance of the slab decreases due to a gradual reduction of the material properties. This reduction in bearing capacity is studied by means of real scale fire tests, consisting of 6 slabs measuring 3.2×3.5×0.25 m with a connected column stub and tested for punching shear with a specially designed loading frame. Two reference tests are executed at ambient temperature conditions and four slabs are submitted to ISO 834 curve for 120 min. Comparison of the test data with the expected increased axial load due to thermal restraint found in the literature, shows a potential danger for premature punching failure of flat slab-column connections exposed to fire.     

Minimum volume of curtailed reinforcement in rectangular slabs

It is well recognized that the bottom reinforcement in rectangular slabs subjected to uniformly distributed load may be curtailed near the edges. Such reinforcement arrangements are naturally more economic than those in which the bottom reinforcement is continued to the supports. Most of the minimum reinforcement solutions for rectangular slabs deal with the latter type of reinforcement arrangement. In this paper, minimum reinforcement solutions for rectangular slabs having curtailed bottom reinforcement are presented. The solution is based on the theory of optimal plastic design for piecewise constant reinforcement. Solutions are presented for slabs with all edges fixed, and with two opposite edges fixed and the other two simply supported, for different aspect ratios of the slab. The minimum moment capacity volumes of the slab are found to be about 10–25% less than those of the slabs in which bottom reinforcement is not curtailed.     

考虑纵筋率及加载面边长比影响的板受冲切承载力试验研究

纵筋率及冲切加载面边长比是影响混凝土板受冲切承载力的重要因素.对12块钢筋混凝土板试件进行了竖向冲切承载力试验研究,板尺寸为2200 mm×2200 mm×200 mm混凝土立方体抗压强度为39～46.9 MPa,板底纵筋率有0.5%和1.3%两种,加载面边长比分别为1.0、2.0和4.0.试验结果表明:配置纵向受拉钢筋可显著提高板的受冲切承载力,但纵筋率高于2.5%时,提高作用已不明显;随着加载面边长比的增大,板的抗冲切承载能力有所降低.根据试验结果得出了试验板的荷载-挠度曲线、冲切破坏面及裂缝分布等;根据试验结果及相关文献的数据,研究分析了纵筋率及加载面边长比对板抗冲切性能的影响,得到板受冲切承载力的近似计算公式,该公式的计算值与试验值符合良好.研究结果可为我国相关规范的修订提供参考.     

Strengthening of two-way concrete slabs with FRP composite laminates

This paper presents an experimental and analytical investigation for evaluating the ultimate response of unreinforced and reinforced concrete slabs repaired and retrofitted with fiber reinforced polymer (FRP) composite strips. A uniformly distributed pressure was applied to several two-way large-scale slab specimens using a high-pressure water bag. Both carbon/epoxy and E-glass/epoxy composite systems were used in this study. In predicting the behavior of the repaired slabs, the finite element method was used. Comparison between the experimental and the analytical results indicated the validity of the computational models in capturing the experimentally determined results for both the control and the rehabilitated slabs. For repair applications, test results indicated that both FRP systems were effective in appreciably increasing the strength of the repaired slabs to approximately five times that of the as-built slabs. For retrofitting applications, use of FRP systems resulted in appreciable upgrade of the structural capacity of the as-built slabs up to 500% for unreinforced specimens and 200% for steel reinforced specimens.     

考虑纵筋率及加载面边长比影响的板受冲切承载力计算分析

按刚塑性冲切计算模型,运用虚功原理及双剪应力强度准则,建立了考虑钢筋混凝土板纵向受拉钢筋配筋率及加载面边长比影响的受冲切承载力计算公式.与试验数据进行计算比较,所建议公式的计算值与试验值符合良好.通过可靠度分析,证明建议公式的可靠指标满足我国规范对脆性破坏不应小于3.7的要求.所建议的计算公式可为我国有关规范的修订提供参考.     

连续组合板的塑性设计

针对国际上大多数关于连续组合板的规范在设计过程 都都限制使用塑性分析 现状,介绍了对连续板正向,负向受弯的定量研究以及负弯曲条件下实验结果,从这些研究中推导出了在连续设计中使用塑性分析确定弯矩和剪力分布的可能性。