An investigation of the block shear strength of coped beams with a welded clip angle connection — Part II: Numerical study

An experimental study of the block shear capacity of ten full-scale coped beams with a welded clip angle connection was presented in Part I. The test results were compared with predictions using block shear design equations in several current design standards. In general, the results showed that the existing design standards did not provide consistent predictions of the block shear capacity of coped beams with welded clip angles. In addition, the equations provided by the standards cannot accurately reflect the failure mode of the specimens observed in the tests. In order to gain a better understanding of the connection behavior, such as the stress distribution in the web near the periphery of the clip angles and the failure mechanism of the connection, an analytical study of the block shear capacity of coped beams with welded clip angles was carried out using the finite element method. Based on the limited test data and the results of the finite element analysis (FEA), a strength model was established and a design equation was proposed to evaluate the block shear strength of coped beams with welded clip angles. It was shown that the proposed design equation gave better predictions of the block shear capacity of the specimens.     

Numerical investigation of the effects of connection rotational stiffness on block shear capacity of coped beams with a welded end connection

In order to investigate the effects of connection rotational stiffness on the block shear capacity of coped beams with welded end connections, a numerical investigation was conducted. Parametric study is conducted based on the validated finite element model. Based on the mechanical model of double angle connection, the pitch and the beam element length-to-angle thickness (L/t) ratio of the outstanding leg are selected as two important parameters to consider the effects of the connection rotational stiffness. The results of parametric study show that the connection rotational stiffness has a great influence on the block shear capacity of coped beams with double welded clip angle connection. The results of parametric study also show the pitch has no significant effect on the block shear capacity. Based on the results of finite element analysis, the design equation proposed by Yam et al. (2007) was modified to account for the effects of the connection rotational stiffness.     

基于神经网络的蜂窝钢梁的承载力研究

对腹板易发生后屈曲的简支蜂窝钢梁的承载力进行研究,讨论分析梁承载力和失效模型的非线性有限元法的准确性。由于非线性有限元计算量很大,故基于有限元进行参数研究,提出蜂窝钢梁腹板的后屈曲临界荷载的经验公式。另采用传统的反向传播神经网路和自适应神经模糊推理系统方法进行求解,并对比传统有限元分析结果,验证经验公式、反向传播神经网络法、自适应神经模糊推理系统法的准确性。结果表明:反向传播神经网络法和自适应神经模糊推理系统法比经验方程更准确。     

A numerical study of the strength and behaviour of reinforced coped beams

A numerical study of the strength and behaviour of reinforced coped beams is presented in this paper. Nonlinear finite element analysis was conducted to predict the structural behaviour and strength of the test specimens examined in a different research study by the authors. The finite element analytical results generally agreed well with the test results. Subsequently, a parametric study using the validated FE models was conducted to further examine the effects of various parameters on the strength and behaviour of reinforced coped beams. For all cases examined in the study, none of the reinforced coped beams experienced flexural failure at the coped section. The parametric results show that for the same beam section, the strength of the reinforced coped beams decreases with increasing cope depth to beam depth ratio (d_c/D), irrespective of the cope length to beam depth ratio (c/D) and types of stiffener. In addition, the strength of the beams generally decreases with increasing c/D ratio. It was also found that for the cope details examined in the study, coped beam sections with a web depth-to-thickness ratio (d/t_w) less than or equal to 52.7 and reinforced by a pair of longitudinal stiffeners are able to develop either the plastic moment capacity of the full beam section near the loading position or the shear yield capacity of the coped section. For a coped beam section with a larger d/t_w ratio, a stiffener arrangement consisting of longitudinal and transverse stiffeners is recommended.     

Performance of shear connection in composite beams with profiled steel sheeting

This paper describes the structural performance of shear connection in composite beams with profiled steel sheeting. An accurate and efficient nonlinear finite element model was developed to study the behaviour of headed stud shear connectors welded through-deck. The profiled steel sheeting had transverse ribs perpendicular to the steel beam. The material nonlinearities of concrete, headed stud, profiled steel sheeting, reinforcement and steel beam were included in the finite element model. The capacity of shear connection, load-slip behaviour of the headed stud, and failure modes were predicted. The results obtained from the finite element analysis were verified against experimental results. An extensive parametric study was conducted to study the effects on the capacity and behaviour of shear connection by changing the profiled steel sheeting geometries, the diameter and height of the headed stud, as well as the strength of concrete. The capacities of shear connection obtained from the finite element analysis were compared with the design strengths calculated using the American Specification, British Standard and European Code for headed stud shear connectors in composite slabs with profiled steel sheeting perpendicular to the steel beam. It is found that the design rules specified in the American and British specifications overestimated the capacity of shear connection, but the design rules specified in the European Code were generally conservative.     

Block shear strength of coped beams with single-sided bolted connection

Block shear is one of the major failure modes for coped steel I-beams. While focus of previous studies on the block shear capacity of coped steel I-beam was mainly given to the connections with double clip angles, single-sided connections, which induce out-of-plane loading eccentricity, have not been adequately considered. Ten full-scale coped steel I-beam tests were conducted to examine the effects of two main test parameters, namely, out-of-plane loading eccentricity and web block aspect ratio (ratio of shear area to tension area). It was found that nine test specimens failed with tension fracture along the bottom bolt row of the web, and the remaining one failed in a whole block tear-out manner. Twisting of the web near the cope was observed for specimens with single-sided connection. More importantly, the test results showed that the out-of-plane loading eccentricity due to the single-sided connection did not have a detrimental effect on the block shear capacity of the specimens. Moreover, increasing the connection rotational stiffness could increase the block shear capacity. These effects are further discussed via a finite element analysis and a preliminary parametric study. Finally, the test results are compared with four major design standards. It is found that the Canadian Standards CAN/CSA-S16-09, which gives a test-to-predicted ratio ranged from 0.93 to 1.17, provided relatively good predictions for the specimens with single bolt line layout, while the predictions by other codes are too conservative. For those specimens with double bolt line layout, the capacities are underestimated by all the considered standards.     

The effects of axial tension on the sagging-moment regions of composite beams

This paper studies the effects of axial tension on the sagging moment regions of steel–concrete composite beams. The study comprised an extensive experimental programme and nonlinear finite element analyses. Six composite beams were designed and tested under the combined effects of axial tension and positive bending moment. The beams were loaded to their ultimate capacity and the experimental moment-axial tension interaction diagram was constructed. Following the tests, a finite element model was used to simulate the nonlinear response of the composite beams. The validity of the model was thoroughly assessed against the available experimental data and a parametric study was conducted to study different beam sizes and the effect of partial shear connection on the interaction diagram. It was found that the moment capacity of a composite beam is reduced under the presence of an axial tensile force acting in the steel beam section. In addition, the use of partial shear connection does not affect significantly the shape of the interaction diagram. The tensile capacity of the composite section, however, is limited by the axial capacity of the steel beam alone. Based on the experimental results and the finite element analyses, a simplified equation is proposed for the design of composite beams subjected to positive bending and axial tension.     

Interaction of buckling modes in castellated steel beams

This paper investigates the behaviour of normal and high strength castellated steel beams under combined lateral torsional and distortional buckling modes. An efficient nonlinear 3D finite element model has been developed for the analysis of the beams. The initial geometric imperfection and material nonlinearities were carefully considered in the analysis. The nonlinear finite element model was verified against tests on castellated beams having different lengths and different cross-sections. Failure loads and interaction of buckling modes as well as load-lateral deflection curves of castellated steel beams were investigated in this study. An extensive parametric study was carried out using the finite element model to study the effects of the change in cross-section geometries, beam length and steel strength on the strength and buckling behaviour of castellated steel beams. The parametric study has shown that the presence of web distortional buckling causes a considerable decrease in the failure load of slender castellated steel beams. It is also shown that the use of high strength steel offers a considerable increase in the failure loads of less slender castellated steel beams. The failure loads predicted from the finite element model were compared with that predicted from Australian Standards for steel beams under lateral torsional buckling. It is shown that the Specification predictions are generally conservative for normal strength castellated steel beams failing by lateral torsional buckling, unconservative for castellated steel beams failing by web distortional buckling and quite conservative for high strength castellated steel beams failing by lateral torsional buckling.     

基于修正软化拉-压杆模型的型钢#br# 混凝土深梁受剪承载力研究

为研究型钢混凝土深梁的受剪承载力,完成7组型钢混凝土深梁的静力试验和有限元分析,主要考虑剪跨比、型钢腹板高度及翼缘宽度等影响因素。试件的破坏模式为斜压破坏和剪切破坏。剪跨比对破坏形态有较大影响,较大的型钢腹板高度和翼缘宽度显著提高试件受剪承载力。在试验研究和有限元分析的基础上,考虑钢筋混凝土部分的软化效应、非软化混凝土与型钢翼缘的协调变形作用及腹板部分的受剪贡献,建立修正软化拉-压杆模型,并采用叠加原理推导型钢混凝土深梁受剪承载力实用计算方法。结果表明：修正软化拉-压杆模型能较好地反映型钢混凝土深梁的破坏特征和受力机制,文中提出的受剪承载力计算方法与试验数据吻合较好,对受剪影响因素考虑更加全面,能较好地预测型钢混凝土深梁的受剪承载力。     

Effects of connection geometry on block shear failure of welded lap plate connections

Although block shear failure has predominantly been considered a potential failure mode for bolted steel connections, several recent experimental programs have revealed that block shear can also govern the design of certain arrangements of welded connections. The mechanics of block shear failure in welded connections are known to be different from the bolted case, although published research on the subject is limited. A nonlinear finite element model has been developed to study the capacity of concentrically loaded welded lap plate connections that fail in block shear. The accuracy of the model was verified by comparing analytical results to those from physical tests. A parametric study was then completed to quantify the effects of connection geometry and weld arrangement. The results of the study are used to describe the behaviour of welded lap plate connections failing in block shear and to evaluate the performance of block shear design equations for capacity prediction of welded connections with a variety of geometries.     

钢骨混凝土连梁联肢剪力墙抗震性能试验研究及有限元分析

国内已有部分超高层建筑结构采用钢骨混凝土连梁联肢剪力墙,但现行规范尚未对其钢骨含钢率等控制参数给予明确规定。为此,对不同含钢率的钢骨混凝土连梁联肢剪力墙进行了低周反复荷载试验研究、ABAQUS有限元模拟以及变参数分析。分析结果表明：钢骨混凝土连梁联肢剪力墙试件的破坏模式、水平承载力、变形能力和耗能能力明显优于钢筋混凝土连梁联肢剪力墙;由ABAQUS参数分析结果可知,钢骨含钢率应控制在4%~8%之间,且宜增加连梁钢骨腹板的面积。     

Shear strengthening of RC beams with web-bonded continuous steel plates

This paper presents the results of an experimental program and a parametric study conducted on RC beams strengthened in shear with web-bonded continuous steel plates. An experimental investigation was conducted to assess the effectiveness of web-bonded continuous steel plates for shear strengthening of RC beams having internal stirrups. A two-dimensional nonlinear finite element model was developed to simulate the overall behavior of beams with epoxy bonded steel plates. In order to develop a design methodology for beams with web-bonded steel plates, a parametric study was conducted. Main parameters considered were concrete strength, plate thickness, plate depth-to-beam depth ratio, yield strength of steel plates, beam size and the internal shear reinforcement ratio. A formula to compute the shear strength of such beams was proposed by adding up the concrete contribution, shear reinforcement contribution and the contribution of steel plates. The validity of proposed formula was checked against the results from parametric study and the experiments. It was found that the proposed formula predicts the ultimate shear strength of RC beams with web-bonded continuous steel plates very well.     

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.     

受负弯矩和压缩作用的组合梁的性能和设计

调查了受负弯矩和轴向压缩共同作用下钢-混凝土组合梁结构的性能。在这项研究中,对6个承受负弯矩作用的足尺寸的组合梁同时进行压缩。轴向压缩的等级由低到高变化。根据试验,构建并标定一个非线性有限元模型来对试验结果进行验证。该模型能够对试验所用梁的非线性响应和最终破坏模式做出预测。所构建的有限元模型对一些常在实际中使用的组合梁可进行一系列参数分析。分析发现,当压缩荷载作用于组合截面时,组合梁的负弯矩承载能力明显降低,钢梁的局部屈曲更显著,影响了截面的延展性。基于截面平衡的刚塑性分析可以合理地预测组合截面的复合强度,因此可适当地使用于设计原理中。在负弯矩区钢梁腹板处使用纵向加劲肋可消除腹板屈曲,并增加组合截面的转动能力。根据试验结果和有限元分析提出一个可应用于工程实践中的简化设计模型。     

Behaviour and design of composite beams subjected to negative bending and compression

This paper investigates the behaviour of steel–concrete composite beams subjected to the combined effects of negative bending and axial compression. For this study, six full-scale tests were conducted on composite beams subjected to negative moment while compression was applied simultaneously. The level of the applied axial compression varied from low to high. Following the tests, a nonlinear finite element model was developed and calibrated against the experimental results. The model was found to be capable of predicting the nonlinear response and the ultimate failure modes of the tested beams. The developed finite element model was further used to carry out a series of parametric analyses on a range of composite sections commonly used in practice. It was found that, when a compressive load acts in the composite section, the negative moment capacity of a composite beam is significantly reduced and local buckling in the steel beam is more pronounced, compromising the ductility of the section. Rigid plastic analysis based on sectional equilibrium can reasonably predict the combined strength of a composite section and, thus, can be used conservatively in the design practice. Detailing with longitudinal stiffeners in the web of the steel beam in the regions of negative bending eliminate web buckling and increase the rotational capacity of the composite section. Based on the experimental outcomes and the finite element analyses a simplified design model is proposed for use in engineering practice.     

Web buckling study of the behaviour and strength of perforated steel beams with different novel web opening shapes

This paper presents an experimental and analytical study on the behaviour of perforated steel beams with closely spaced web openings. Seven specimens including two typical cellular beams (i.e. circular web openings) and five perforated beams with novel web opening shapes were tested to investigate the failure mode and load strength of the web-post between two adjacent web openings. Fourteen numerical test specimens were developed and analysed by the finite element method and the results were compared with the full scale experiments. The effect of web opening spacing/web opening depth of web-posts was studied to investigate the effective ‘strut’ action of the web-post buckling. The effect of the web opening depth/web thickness was also studied to investigate the stability (slenderness) of the web-post subjected to vertical shear load. Two hundred and twenty-fine elastic-plastic finite element analyses were then employed in a comprehensive parametric study to propose an empirical formula which predicts the ultimate vertical shear load strength of web-posts formed from the particular web opening shapes.Perforated beams with standard circular, hexagonal and elongated web openings are mostly used nowadays. Various non-standard web opening shapes are introduced through this paper for first time. These new pioneering web opening shapes improve the structural performance of the perforated beams when examined under the web-post buckling failure mode. In addition, the manufacturing procedure of these non-standard web openings show great advantage in comparison with the manufacturing way of the more popular cellular beams.     

方钢管混凝土框架-十字加劲薄钢板剪力墙结构水平承载力研究

为研究方钢管混凝土框架-十字加劲薄钢板剪力墙结构的抗震性能和水平承载力,进行了一榀缩尺比为1∶3的2层单跨方钢管混凝土框架-十字加劲薄钢板剪力墙结构的拟静力试验,得到了其破坏形态、荷载-位移滞回曲线、骨架曲线、特征荷载和位移等。利用有限元软件ABAQUS对其进行了非线性数值模拟,分析了方钢管混凝土框架-十字加劲薄钢板剪力墙的抗震性能、受力机理和破坏机制。基于试验和数值模拟结果,结合理论研究,提出了方钢管混凝土框架-十字加劲薄钢板剪力墙的水平承载力的计算式,并将其计算结果与试验、数值模拟结果进行对比。结果表明：方钢管混凝土框架-十字加劲薄钢板剪力墙具有较高的水平承载力、初始刚度及良好的延性和耗能能力,水平承载力计算式的计算结果与试验、数值模拟结果吻合较好。     

横向腹板加劲肋的合理设计模型

腹板加劲肋的现行设计方法在概念和加劲肋尺寸上有很大差异。为了给横向加劲肋提出一个合理、适用的有效设计方法,考虑了加劲肋上由拉力和外力作用产生的轴向压力,加劲肋上有效分隔腹板所必需的横向力和加劲板的整体屈曲趋势。为保证加劲肋的屈服不会在板屈服前发生,建立了相应的设计标准。     

Finite element analysis of steel-concrete-steel sandwich beams

The static behaviour of Bi-Steel beams was simulated using a finite element model. The model was compared to test results showing good agreement. It was then used in parametric studies of transverse shear capacity and uniformly distributed load cases of Bi-Steel beams. It was possible to isolate the transverse shear failure mode and prevent other failure modes from using the FE model. This enabled the comparison and verification of the proposed design equations for transverse shear. Based on parametric studies, modifications to the design method were also proposed to accommodate udl cases.     

Assessment of load carrying capacity of castellated steel beams by neural networks

In this paper, load carrying capacity of simply supported castellated steel beams, susceptible to web-post buckling, is studied. The accuracy of the nonlinear finite element (FE) method to evaluate the load carrying capacity and failure mode of the beams is discussed. In view of the high computational burden of the nonlinear finite element analysis, a parametric study is achieved based on FE and an empirical equation is proposed to estimate the web-posts’ buckling critical load of the castellated steel beams. Also as other alternatives to achieve this task, the traditional back-propagation (BP) neural network and adaptive neuro-fuzzy inference system (ANFIS) are employed. In this case, the accuracy of the proposed empirical equation, BP network and ANFIS are examined by comparing their provided results with those of conventional FE analysis. The numerical results indicate that the best accuracy associates with the ANFIS and the neural network models provide better accuracy than the proposed equations.