Beam Flange Research Articles

Seismic performance and analytical model of CFDST joint with endplates and long bolts

Developing the prefabricated structures is an effective way to reduce carbon emission. At present, the research on the prefabricated concrete-filled double-skin steel tubular (CFDST) joints is insufficient. In this paper, a prefabricated steel beam to CFDST column joint was proposed. In order to investigate the seismic behavior of the joint, a series of pseudo-static tests were performed on four 1/2 scale specimens with consideration of the endplate type and the inner steel tube shape. The failure modes included bending deformation of the endplate, warpage of the bolts, fracture of the weld seam, and buckling of the steel beam flange. Besides, all specimens exhibited better hysteretic behavior, ductility, strength, and stiffness. The ultimate strength and the energy dissipation capacity of the joint with the extended endplate were higher than the joint with the flush endplate. The inner steel tube shape had limited impact on the seismic performance except that the inner circular steel tube can distinctly increase the energy dissipation capacity of the extended endplate joint. According to the classification method in EC3, the proposed prefabricated joint was the semi-rigid and partial-strength joint. Moreover, the strain analysis indicated that the yield pattern was from the steel beam flange to the endplate. In addition, a prediction method of moment resistance was proposed and verified by test results. The research results of this paper provide a design basis for the prefabricated CFDST structures.

Improving anti-progressive collapse capacity of welded connection based on energy dissipation cover-plates

In view of the poor robustness of fully welded connections, energy dissipation cover-plates (EDCs) were proposed in this study with the aim of improving their anti-progressive collapse capacity. First, the stress law and failure modes of the EDCs were revealed through the study of 13 uniaxial tensile test specimens, and the calculation formulas for the collapse resistance and corresponding deformation of the EDC were determined by theoretical analysis. Then, a design method for a fully welded connection with EDCs was proposed according to the forming principle of the double plastic regions and the deformation coordination principle of the EDC and beam flange. The analysis results show that the design method verified by analyzing three series of numerical examples is reasonable. The collapse resistance and deformation of the substructures with EDCs were increased by 78%–120% and 140%–182%, respectively, compared with those of substructures without EDCs. Moreover, the substructures with EDCs formed an obvious resistance improvement stage. The beam members in the substructure with EDCs can yield completely before connection failure, which enhances the catenary mechanism and delays the failure of the connection. The energy generated by the vertical load dissipation in the structure with EDCs can be increased to approximately twice that of the original structure. Therefore, adding EDCs is conducive to the dissipation of the energy generated by vertical loads and to the improvement of the collapse resistance of a fully welded connection.

Reinforcement of steel beam-to-double column moment connection using side plates

One of the disadvantages of conventional steel structures in Iran is the common way of I-shaped beam to double column fixed connection that do not perform well against seismic loads. This article uses the side plate to modify and optimize the connection. Using this new geometry, the beam-to-column direct connection is eliminated, and there is no longer any concern about the brittle fracture of penetration weld of the beam-to-column connection and the weakness of panel zone that occur in the common fixed connections.
 In addition, by eliminating the direct transfer of beam flange force to the double column connection plate, the problem of deformation, complexity or buckling of the cover plate of the column is spontaneously removed. In this paper, in order to investigate the nonlinear behavior of beam-to-double column connection system, a number of three-dimensional finite element models under the effect of cyclic loading have been analyzed. The results show that the beam-to-double column connection using the side plates has good strength and ductility and can be used in special moment frames for seismic areas.

Steel rigid beam-to-column connections strengthened by buckling-restrained knee braces using round steel core bar dampers

This paper presents an innovative application of buckling-restrained knee braces (BRKBs) for spreading plasticity at the beam ends of rigid moment connections. A slender knee brace configuration consisting of a steel core bar and tube buckling restrainer is proposed. The benefit of adopting a steel bar is that it enables the downsizing of the knee brace connections between braces and beam flanges. The advantages of tube buckling restrainers include relatively simple implementation for ease of construction and reduced weight compared to mortar-filled buckling restrainers. Displacement-controlled cyclic loading tests were conducted to examine the spreading of the plasticity behaviors of rigid moment connections using the proposed BRKBs. Structural performance metrics such as hysteretic behavior, strength capacity under a given loading, and strain distributions at beam flanges were measured and analyzed in detail. Additionally, the optimal parameters for the proposed BRKBs were determined through an extensive numerical study. The results revealed that the optimal parameters of the proposed slender BRKBs significantly improve load-bearing capacity and reduce stress concentrations in the vicinity of the rigid beam-to-column connections. As a result, the plastic region on the beam is spread both inside and outside the knee brace area. Based on the research conducted thus far, it was determined that the proposed BRKB is a viable option for spreading plasticity along beams in rigid beam-to-column connections.

Parametric study on the structural behaviour of composite slim floors with hollow-core slabs

Steel-concrete composite structures and precast concrete elements have a common prefabrication process and allow fast construction. The use of hollow-core slabs associated with composite floors can be advantageous. However, there are few studies on the subject, impeding the application of such systems. In this paper, a numerical model representing the considered system using the FE (finite element)-based software DIANA is developed. The results of an experimental test were also presented in Souza (2016) and were used to validate the model. Comparisons between the numerical and test results were performed in terms of the load versus displacement, load versus slip, and load versus strain curves, showing satisfactory agreement. In addition, a wide parametric study was performed, evaluating the influence of several parameters on the behaviour of the composite system: The strength of the steel beam, thickness of the web, thickness and width of the bottom flange of the steel beam and concrete cover thickness on top of the beam. The results indicated a great influence of the steel strength and the thickness of the bottom flange of the steel beam on the capacity of the composite floor. The remaining parameters had limited influences on the results.

Artificial neural network and regressed beam-column connection explicit mathematical moment-rotation expressions

Steel flush endplate beam-column connections behavior is commonly described by the moment-rotation, M -φ, relationship, which is characterized by two essential terms; resistant moment, M j, Rd , and initial rotational stiffness , S j, init . A great amount of concerted effort has been invested worldwide to either experimentally or analytically describe these properties due to geometrical and material variations. However, these methods are either costly, laborious, or time-consuming. Therefore, acknowledging the wealth of literature information, this paper formulates a set of practically convenient mathematical M -φ expressions by means of artificial neural network (ANN) and multi-linear regression (MLR) approaches utilizing the MATLAB software. Differing from most existing machine learning variants, the paper offers explicit expressions for maximum moment, M max , and S j, init , which can be characterized through a simplistic insertion of input parameters in terms of beam depth, beam width, thickness of beam flange , thickness of beam web, column depth, column width, endplate depth, endplate thickness, and bolt capacity. The computed M max and S j, init can then be adopted to express the currently defined continuous M -φ relationship. By statistical evaluation, it is witnessed that the mean-absolute-percentage error (MAPE) and correlation coefficient ( R 2 ) of both ANN and MLR methods are of remarkable prediction vitality. Also, ANN outperforms slightly MLR model in the prediction of both M max and S j, init although both approaches agree closely with the source data. Therefore, both approaches are of high reliability in predicting M max and S j, init as well as in characterizing the M -φ relationship of the flush endplate beam-column connections for further engineering analysis and design purposes. • Equation for continual M-φ relation for flush endplate beam-column behavior. • Continuous M-φ relation is produced simply by plugging in connection properties. • M-φ relation is defined only by maximum moment M max & stiffness S j,init . • M max & S j,init are defined by connection geometrical & material expressions. • Proposed ANN & regression models predict statistically well the observed M-φ curve.

Web crippling design of modular construction optimised beams under ETF loading

In recent times, modular construction is considered as one of the most effective construction methods. It is necessary to understand the structural behaviour of modular construction elements for possible improvements. Modular Construction Optimised (MCO) beam is one of the innovative profiles and can be categorised into hollow flange Cold-Formed Steel (CFS) sections. The hollow flanges encourage bending stiffness and flexural performance, in contrast, slender web causes web crippling failure as these members are often subjected to concentrated loads and reactions. Even though research studies regarding MCO beams are very limited, the structural performance of other types of hollow flange beams has been covered in previous studies. However, to date, web crippling behaviour of MCO beams is still unknown and should be investigated to enhance the commercial aspects of MCO beams as this is an innovative section in the modular construction area. To address this research gap, this paper investigates the web crippling capacity of MCO beams under End-Two-Flange (ETF) load case with flanges unfastened to support condition using numerical analysis. Numerical models were developed and validated against the web crippling test results of hollow flange beams available in the literature. Subsequently, parametric numerical analysis (162 models) was conducted for MCO beams with varying key controlling parameters on web crippling capacity. The web crippling capacities of MCO beams were compared with existing codified (AISI S100, AS/NZ 4600) predictive equations and new design equations were developed to accurately predict the web crippling capacity of MCO beam under ETF load case with flanges unfastened condition. • Investigated web crippling behaviour of Modular Construction Optimised (MCO) beams under ETF load case. • The effect of section depth, web thickness, yield strength, bearing length, effective depth of the beam was identified. • Corner radius effect on web crippling behaviour of Modular Construction Optimised beams was investigated. • Web crippling design equations for Modular Construction Optimised beams under ETF load case are not available in standards. • Web crippling design equations for Modular Construction Optimised beams under ETF load case was proposed.

Shear behaviour of doubly symmetric rectangular hollow flange beam with circular edge-stiffened openings

Cold-Formed Steel (CFS) sections are evolved through the last two decades compromising various aspects of construction needs. Doubly symmetric Rectangular Hollow Flange Beam (RHFB) is one of the innovative CFS sections, which was introduced to eliminate the drawbacks of conventional open CFS sections such as prone to complex buckling and torsional effects. Edge-stiffened web holes are recently recommended and available for extensive usage in the floor beams. Even though previous studies conducted researches on various kinds of stiffeners, there is no definite design equation or findings that were presented on shear behaviour. Therefore, this study focuses on the effect of edge-stiffened circular web openings on the shear capacity of doubly symmetric RHFB. Non-linear numerical models were developed using the ABAQUS software package for validation purposes and then comprehensive parametric studies were carried out for doubly symmetric RHFB with edge-stiffened openings. A total of 558 models consisting of edge-stiffeners, un-stiffened openings and plain webs were analysed in this study. Parametric results of with edge stiffeners exhibited shear capacity increment (1–90%) compared to unstiffened web openings. Hence, new design equations were proposed in the form of reduction factor and based on Direct Strength Method (DSM). Finally, optimum edge-stiffener length of 15 mm was recommended regardless of web opening size.

Experimental and numerical investigation on seismic performance of extended stiffened end-plate joints with reduced beam section using high strength steel

The flexural behavior of bolted extended stiffened (ES) end-plate joints with high strength steel (HSS) is crucial in order to avoid brittle fractures in earthquakes. A total of three types of ES joints with different failure mode were carefully designed to cover commonly used types of joints, namely the full strength, equal strength, and partial strength joints. They were tested under cyclic loading to further investigate their seismic performance, and to evaluate the suitability of the design equations specified in European Code (EN 1993: 1-8 and EN 1998-1). Experimental results showed that the energy dissipation zone of the extended stiffened full (ESF) strength joints with HSS is mainly concentrated in the reduced section, while the one of the extended stiffened equal (ESE) strength joint using HSS is mainly distributed in the end-plate and the reduced section, both of them belong to ductile failure mode; the extended stiffened partial (ESP) strength joints with HSS only rely on the crack propagation and closure between the end-plate and the beam flange, and the limited plastic deformation of the end-plate to dissipate seismic energy, which presented brittle fracture; The failure mechanism and energy dissipation capacity of ES end-plate joints with HSS are closely related to the capacity design parameters αd, The capacity design calculation model of the ES joints based on the EN 1993: 1-8 code component method can accurately predict its failure mode, but the reasonable parameter αd needs to be further studied in European Code. Finite-element analysis was performed and showed good agreement with the experimental results. It was found that a higher likelihood of fracture in transition length rather than in the connection area was reconfirmed in both ESF and ESE joints, while for ESP joints, it is in the CJP weld of the beam flange end.

Mechanical properties of T-plate stiffened gusset joints for aluminum alloy single layer two-way grid shells

The mechanical performance of T-plate stiffened gusset (TSG) joints for aluminum alloy single layer two-way grid shells is presented in this paper. Firstly, a kind of TSG joints for aluminum alloy spatial structures is proposed to improve the mechanical behavior of gusset joints. Secondly, six full-scale specimens, including unstiffened gusset (USG) joints, plate stiffened gusset (PSG) joints in literatures and TSG joints, are tested under monotonic loads to investigate their flexural capacity. Thirdly, the design parameters of TSG joints, such as gusset plate thickness, beam height, beam width, beam flange thickness, beam web thickness, T-plate flange thickness and T-plate web thickness, are studied through numerical analyses. The experimental and numerical results indicate that TSG joints can show better out-of-plane mechanical properties than USG and PSG joints. Finally, the bearing capacity prediction methods for TSG joints are provided based on theoretical analyses.

Flexural performance of spliced composite slim beam with slotted web

The flexural performance of a spliced composite slim beam with a slotted web (SCSB-SW) was assessed and prediction formulae of flexural capacity and initial stiffness for the beam were deduced. Through a four-point bending test, the flexural performance of the SCSB-SW was preliminary studied. The experimental results indicated that the section of the SCSB-SW conformed to the plane section assumption in the elastic stage. The beam failed in a ductile failure mode while there was no obvious relative slip between the steel beam and concrete slab in the failure stage. Finite-element models were developed and validated using the test results. A parametric analysis revealed that even if the cross-sectional dimensions and the position of the neutral axis in the beam are changed, the results predicted by the formulae still matched the numerical results well. The material strength, the thickness of the bottom flange of the steel beam and the concrete slab dimensions were found to play key roles in the flexural capacity of the beam, whereas the compressive strength grade of the concrete, the depth of the steel beam web and the dimensions of the concrete flange have significant effects on the initial stiffness of the beam.

Shake Table Testing of Self‐Centring Concentrically Braced Frames

AbstractThe self‐centring system presented in this paper is a novel damage control technique designed to improve the resilience of concentrically braced frames (CBF) under seismic action. Namely, traditional CBFs can undergo large residual drifts following an earthquake event which can limit the opportunity for cost‐effective repair of the structure. Additionally, the gusset plates connecting the brace members to beams and/or columns can experience substantial rotations as a result of the compression buckling of the bracing members. Through the utilisation of post‐tensioning strands placed between flanges of beams, the novel self‐centring concentrically braced frame (SC‐CBF) system can return the frame to its original position after significant inelastic deformations experienced during large earthquakes, resulting in minimum residual drifts.In this paper, shake table testing of the aforementioned SC‐CBF system subjected to realistic earthquake loading is presented. The research is carried out as part of the H2020 “Seismology and earthquake engineering research infrastructure alliance for Europe” SERA project. Four sets of bracing configurations, incorporating varying square hollow section (SHS) braces and gusset plates were utilised in the shake table testing. Uniaxial loading with varying shake table accelerations was executed and the structural response evaluated using data from strain gauges (SG), load cells (LC), displacement transducers and accelerometers. The measured results provide information on the important parameters such as the tensile and compressive strength of the braces, post‐buckling capacity, gusset plate strains and post‐tensioning force. These findings are then presented and the crucial local and global response performance emphasised.

Comparison of HST and WO Shear Connector Behaviour in Composite Slim Floor

AbstractComposite steel‐concrete slim floor construction is an economical floor system proposing minimum floor depth and fast construction besides architecture requirements. In this system, the concrete slab is supported on the lower flange of the steel beam using either in‐situ or pre‐cast technique, which eliminates the use of the down‐stand beam, hence giving a flat look. Hollow steel tube (HST) shear connector is proposed to avoid premature failure that could occur in concrete and steel beam web when the web openings (WO) connectors were used. In this paper, the comparison of push‐out test results between HST and WO to evaluate their ultimate shear load and ductility performance of these type of connectors. The varied parameters were the concrete compressive strength and shape of the HST and WO; the circular, rectangular and square. The results showed that the circular and square HST connectors achieved shear capacities 6.3 and 8.0 times higher than those with the WO type, respectively. Furthermore, the ductility of the specimens increased by 3‐4 times when the HST was used compared to WO. It shows that providing the HST significantly improved its ultimate shear load and ductility performance compared to WO.

Numerical Study of Composite Steel Cellular Beam System Using Demountable Shear Connectors

AbstractSteel concrete composite beams have been increasingly adopted in practice due to their advantages with respect to their structural features and constructability. However, in conventional composite beam systems the composite action is applied via the shear connectors welded at the top flange of the downstand steel beam and embedded in the concrete slabs, making the disassembly of the beam system and reuse of any component impossible. This paper presents a numerical study of a new composite beam system with a steel cellular beam, metal deck flooring and using demountable shear connectors. According to the experimental study, this composite beam system made the demounting, reassembly and member reuse possible, and did not compromise the loading capacity. In the numerical study presented in the paper, the finite element model was developed and validated against the results obtained from the experimental study. The parametric study further examined the effects of concrete strength, shear connector arrangements etc. The comparison and analysis clarified the mechanism of the demountable shear connector and the effect of construction method on the load capacity of the composite beam system, and provided a deeper insight into the behavior of this type of shear connector. Through this numerical study, the structural merits of the composite beam system using demountable shear connectors were highlighted.

Stiffness of equal width welded I‐beam to RHS column connection

AbstractDespite some recent efforts, the use of mechanical approaches like the component method for the rotational stiffness of connections is still not present in the design codes for hollow sections. In addition, the easiest way to obtain semi‐rigid connections with high rotational stiffness or even rigid ones with I beams and RHS columns is to design both members with the same width. In this way, loads are transferred almost directly from the beam flanges to the side walls of the RHS, avoiding the high rotations due to the bending of the front face of the RHS. Considering all this, some experimental tests have been used by the authors to validate a finite element model that simulates equal width connections in which the component ‘lateral faces of RHS’ under transverse forces was the main source of beam rotation. This was selected as the most important component to be considered in the welded joints between I beams and RHS columns when they have the same width. Then, some different analytical approaches for its stiffness have been assessed by comparing them with the experimental and numerical results. This work finally proposes a design equation for the ‘lateral faces of RHS in tension or compression’ in order to be applied in a future unified proposal for the component method including hollow sections. In addition, a rotational stiffness approach for the equal width welded I‐to‐RHS connections has been directly derived from this.

Sliding corner gusset connections in concentrically braced frames using BRBs: Numerical analysis and practical design

In braced frames, the frame action, i.e. beam-column joint opening and closing, may cause premature rupture of the welded corner gusset connection and/or its adjacent framing members. To mitigate the detrimental frame action effect, a novel sliding gusset connection, in which the gusset plate is bolt connected to beam and column flanges through slotted end plates and sliding at the gusset-to-frame interfaces is permitted, has been proposed and experimentally studied for buckling-restrained braced frames (BRBFs) in previous research. To extend the findings of the experimental tests and develop a practical design procedure, high-fidelity finite element models for the sliding gusset connections were constructed, and their accuracy was validated against the experimental results. A series of numerical parametric studies were subsequently conducted. Firstly, the effect of different beam-to-column connection configurations was studied. With the strengthened beam end, the beam plastic hinge developed outside the gusset connection region, which reduced the plasticity in the gusset plate and the force demands on the bolts, due to the mitigated normal interaction at the gusset-to-frame interfaces. Secondly, for the design of bolts in the sliding gusset connection, the equivalent tensile force method was proposed. The acting position of the equivalent forces under brace tension action was quantified, considering different bracing angles and frame member sections. Thirdly, the behavior of the sliding gusset connection under the combined brace-frame action was studied. Based on the results, the design method for the gusset plate was validated, and recommended bolt design criterion was proposed. Lastly, based on all the results and discussion, a practical design procedure was proposed for the sliding gusset connection in BRBFs, which can be immediately used by engineers.

Lateral torsional buckling of steel beams strengthened by steel plate

A numerical study has been carried out to know the lateral torsional buckling of hot rolled steel I beam strengthened using steel plate at the bottom flange. A linear and non-linear analytical study has been carried out using Abaqus software to know the behaviour of beams. For this analysis, ISMB500 is strengthened using a steel plate by varying the thickness of the steel plate. Welded connection is used for connecting the steel plate and bottom flange of a steel beam. The research work aims to determine the ultimate bending strength of the unstrengthened and strengthened I beam. The load deflection behaviour of strengthened and unstrengthned beams was also studied in this research work. Strengthening of steel beam using a steel plate significantly increases the load carrying capacity of steel I beam between 6% and 22%. The percentage of increasing load carrying capacity is depend upon the thickness of plate.

Anti-collapse performance of composite frame with special-shaped MCFST columns

A spatial steel frame with concrete slab and special-shaped multi-partition concrete filled steel tubular columns was tested in a simulated scenario of progressive collapse. The load-deformation relationship of the frame with damaged middle column under vertical load is discussed. Parametric analysis is also conducted by using a validated FE model. The results show that the failure of the specimen resulted from the fracture of the bottom beam flange eventually. The configuration of side plate connection and multi-partition concrete filled steel tubular column both could provide a reliable load-redistribution path for additional loads due to single column loss. The designed frame exerts good robustness to resist the collapse resulting from middle column loss. The simulation shows that single-column removal would cause additional lateral force and moment on the adjacent columns, besides axial force. The length of side plate exhibits more influence on the performance of the frame than the thickness of side plate.

A Comparison Study between Asymmetrical Castellated Steel Beams Encased by Reactive Powder Concrete with Laced Reinforcement

The main objectives of this study are to study the enhancement of the load-carrying capacity of Asymmetrical castellated beams with encasement the beams by Reactive Powder Concrete (RPC) and lacing reinforcement, the effect of the gap between top and bottom parts of Asymmetrical castellated steel beam at web post, and serviceability of the confined Asymmetrical castellated steel. This study presents two concentrated loads test results for four specimens Asymmetrical castellated beams section encasement by Reactive powder concrete (RPC) with laced reinforcement. The encasement of the Asymmetrical castellated steel beam consists of, flanges unstiffened element height was filled with RPC for each side and laced reinforced which are used inclined continuous reinforcement of two layers on each side of the Asymmetrical castellated steel beam web. The inclination angle of lacing reinforcement concerning the longitudinal axis is 45. Four specimens with four different configurations will be prepared and tested under two concentrated loads at the mid-third of the beam span. The tested specimen's properties are the First model; unconfined, Asymmetrical castellated steel beam (Reference), while the second, third, and fourth models consist of Asymmetrical Castellated steel beam (web and flange) confined with (RPC) with 19.1, 38.2, and 57.3 mm gap, respectively, between the two beams sections (the upper and lower one). The results of the experimental tests show that the use of RPC enhanced the properties of the castellated beams in all selected conditions despite creating a gap between the castellated beams.

COMPOSITE ACTION OF STEEL-CONCRETE COMPOSITE BEAMS UNDER LATERAL SHEAR FORCE

The formulas for the shear capacity of steel-concrete composite beams either in current specifications or proposed by researchers do not consider the contribution of the shear resistance of the flanges of steel beams. Therefore, the calculation results are relatively high. Based on the reasonable material constitutive relations and ABAQUS, a full-scale finite element model of composite beams considering the stress characteristics of the bolts was established to study the shear properties. The accuracy of the model was verified by a comparison with existing test results in the literature. Through a parametric analysis, the boundary shear span ratio of composite beams was determined, and the redistribution rule of the internal force of the studs of composite beams under shear loads was revealed. The combination rule of the steel beam and the concrete wing plate and the sharing proportion of the shear load were also revealed. Based on the superposition principle, a formula for calculating the shear capacity of I steel-concrete composite beams considering the shear contribution of the concrete slabs, steel girder webs and flanges was presented. The comparison results show that the accuracy of the proposed formula is higher than those suggested by GB 50017−2017 and other researchers.