Flange Of Steel Beam Research Articles

Axial behavior variation of 72-story concrete-filled steel tubes with different joint connections due to interface debonding considering long-term deformation of concrete core

Long-term concrete deformation including shrinkage and creep occurring seriously threats the longevity, safety and serviceability of concrete-filled steel tube (CFST) structures. In this study, numerical simulation on the variation of axial behavior of 72-story CFST structures with different joint connection details due to interface debonding considering shrinkage and creep of concrete core is carried out. Three connection details including connections with inner horizonal diaphragms only, two-direction through-beams only, and inner horizontal diaphragms combined with two-direction through-beam, are considered, respectively. Vertical loading from floors is treated as centralized vertical force applied on steel tube directly. The shrinkage of concrete core is simulated by decreasing concrete temperature. A cohesive constitutive law and a Coulomb friction model are employed to describe the interface behavior in tangential direction before and after debonding, respectively. The interaction between concrete core and steel tube in normal direction is treated as a hard contact. The concrete plastic-damage (CPD) constitutive model is used for concrete core and a plastic constitutive law is employed for the steel tube. The initiation of the interface debonding between steel tube, H-shaped steel beam flanges, inner diaphragms and concrete, the variation of the force transfer path, stress redistribution, steel tube yielding and the final failure are described in detail. Results show that the axial load-carrying capacity of each CFST structure has a decrease of 26-28% when compared with that determined by the current design code where the confinement effect is considered, and a decrease of 9-10% when compared with that determined by the current design code where the confinement effect of steel tube is not considered. Moreover, the axial stiffness decreases to 76-78% of their theoretical values when debonding is not considered. Numerical results show that the interface debonding negatively affects the long-term axial load-carrying capacity and stiffness obviously, which has not been considered in current design codes. Some comments on the design of CFST members are proposed based on the numerical simulation results.

Seismic behavior of exterior joint of CFDST column to steel beam with RC slab

To investigate the seismic performance of an exterior joint connecting concrete-filled double-skin steel tubular (CFDST) column to steel beam with reinforced concrete (RC) slab, four scaled-down joint specimens were designed at a ratio of 1:2. Quasi-static tests were conducted with different axial compression ratios were performed, and the failure mode, hysteresis curve, skeleton curve, bearing capacity, energy dissipation capacity, strength and stiffness degradation, and strain analysis of the composite joint were analyzed. A finite element method (FEM) model of the joint was constructed and validated against the obtained experimental results. Additionally, a parametric study was carried out to investigate the influence of various factors, including the hollow ratio of the CFDST column, the concrete strength of the slab, the thickness of the slab, and the width-to-thickness ratio of the outer steel tube on joint. Based on experimental studies and finite element analysis (FEA), a theoretical calculation method was proposed to evaluate the flexural capacity of the composite joints. The test results showed that the composite exterior joint specimens with RC slab failed at the beam end. Typical failure phenomena of fracture at the steel beam and horizontal end plate interfaces, steel beam flange buckling, and concrete crushing at the RC slab were observed in the experiments. While the interior joint specimen experienced significant plastic deformation and buckling at the column flange. The hysteresis curve of the specimen is elliptical and full without pinching. The presence of RC slab can effectively improve the ultimate bearing capacity, initial stiffness and energy dissipation capacity of the specimen. The FEA results show that the bearing capacity of the composite joints was improved significantly with the increase of the thickness of the slab and the width-thickness ratio of the outer steel tube. The theoretical calculation results of the flexural capacity of the joint are 86 %–112 % of the results of the finite element calculation. The stability and accuracy of the calculation method are excellent and can be effectively applied to calculate the flexural capacity in CFDST composite structural systems.

Optimization study of strengthened T-shaped concrete-filled steel tubular (CFST) column-steel beam joint

In this paper, a strengthened T-shaped concrete-filled steel tubular (CFST) column-steel beam joint is proposed. The joint is strengthened in the core region of the column wall as well as the beam, to avoid buckling of the column wall and outward displacement of the plastic hinge at the beam end. To study the damage modes and seismic performance of the joint, low-cycle loading experiments on two full-scale specimens of the joint were carried out. The results show that each specimen was damaged by plastic hinging of the steel beam flanges, the column walls did not buckle, and all had a good seismic performance. In addition, Abaqus finite element software was utilized to optimize the joints by analyzing the effects of changing the dimensions of the strengthened column and modifying the structure of the beam-column connection. Simulation results show that increasing the thickness and height of the strengthened column wall enhances the joint's load capacity, stiffness, and energy dissipation. it is recommended that the width-to-thickness ratio of the strengthened columns should be at most 0.08 and the beam-to-column height ratio should be kept at least 1.3. Additionally, two optimization methods, reducing the wall thickness of the steel corbel and weakening the steel beam flange, can effectively reduce weld tearing at the beam-to-column connections, while guaranteeing a good seismic performance. It is suggested that the slope of the steel corbel is not less than 1:6.25, and the weakening ratio of the steel beam flange is not greater than 0.267.

Study of Panel Zone Behavior in Interior Beam–Column Joints with Reduced Beam Section (RBS)

Based on the post-earthquake investigation of the Beiling and Hanshen earthquakes, many welded rigid beam–column joints were found to exhibit brittle failure. The failure modes of the joint region and the overall steel frame structure under the action of the earthquake need to be studied. The seismic performance of different types of weakened beam-end interior joints was investigated. The finite element method was verified by high-strength steel beam–column joint tests conducted by our research team. Finite element modeling of weakened steel beam flanges and weakened steel beam web joints was carried out based on the validated finite element modeling method. The joints were studied and analyzed using seismic parameters such as joint stress clouds, equivalent story shear–inter-story displacement ratio curves, panel zone bending moment–shear ratio curves, ductility, stiffness, and energy dissipation. The results of this study showed that honeycomb open hole-type joints exhibit a better deformation and energy dissipation capacity compared to open circular web hole-type joints. However, their load carrying capacity is reduced, which is mainly due to the larger area of the web openings. Additionally, double reduced beam section (DRBS) joints exhibit superior seismic performance and plastic hinge outward movement characteristics compared to single reduced beam section (RBS) joints. It was also found that the deformation and energy dissipation of DRBS joints and steel beam honeycomb hole-type joints are mainly borne by the beams, with the panel zone’s participation in energy dissipation accounting for a smaller proportion of the energy.

The Concrete Effective Width of a Composite I Girder with Numerous Contact Points as Shear Connectors

Due to the shear strain in the plane of the slab, the parts of the slab remote from the steel beam lag behind the part of the slab located in its proximity. This shear lag effect causes a non-uniform stress distribution across the width of the slab. As a result, several standards have introduced the concept of an effective flange width to simplify the analysis of stress distribution across the width of composite beams. Both the computed ultimate moment and serviceability limit states are directly impacted by the effective width. The effect of using a large number of contact points as shear connectors on the effective width of a steel beam flange has not been investigated. A three-dimensional finite element analysis is carried out in this paper. The ABAQUS software (version 6.14) is used for this purpose, where several variables are considered, including the surface area connecting the steel beam and concrete slab, the transverse space, and the number of shear connectors. It was discovered that the number of shear connectors on the steel beam flange has a major impact on the effective width. The many connectors work together to provide a shear surface that improves the effective width by lowering the value of the shear lag.

The Effect of Opening Size and Expansion Ratio on the Flexural Behavior of Hot Rolled Wide Flange Steel Beams with Expanded Web

In some design cases, such as in castellated beams, cellular beams, or steel beams with expanded web, it is advantageous to strengthen and enhance the performance of steel beams by increasing the web depth. However, expanding the web of a steel beam is a unique engineering strategy. This modification not only enhances its ability to bear heavy loads but also reduces any bending or flexing while enabling longer distances between supports. The expanded steel beams can be achieved by making a horizontal cutting in the steel beam web and then adding an increment plate (with the same web thickness), called spacer plate, between the two halves of the web sections, thus improving stiffness and strength. To evaluate the behavior of such beams, nine specimens of HEA steel beams with expanded web ratios of 150%, 200%, and 250%, and one specimen as a reference beam, were fabricated. The specimens were evaluated under two-point load over a clear span length of 280 cm. From the experimental work it was found that for steel beams with expanded web that have 18 openings with 80 mm, the beams with an expansion ratio of 150% had the best performance according to load-deflection behavior with a reduction in load capacity by only 11%. Additionally, the beams with expansion ratios of 200% and 250% had no economic viability according to the analysis of load-deflection behavior with a reduction in load capacity by 49% and 62%, compared with the solid expanded steel beam with the same expansion ratio. For the second type of steel beam with expanding web with 9 openings of 160 mm width, the beams with expansion ratios of 200% and 250% were observed to perform better than the first type with a reduction in load capacity by 28% and 50%. Using larger opening width and a smaller opening number is considered the best option for beams with expansion web ratios of 200% and 250%, while on the contrary, using smaller opening width and higher numbers seems to be a better option for beams with 150% expansion web ratio. Expanding the depth of a steel beam provides design flexibility, reduces deflections, and allows for longer spans. These benefits enhance material efficiency and open up new architectural possibilities.

Experimental and numerical study on seismic behavior of partially steel-reinforced concrete beam-to-steel tube column joint

Steel-reinforced concrete (SRC) beams are commonly used in the transfer structures of high- and super-high-rise buildings since concrete-encased steel elements have good resistance to buckling and seismic performance. However, the full-length steel shapes utilized in SRC beams are ineffective and pose many construction challenges. This study proposes a new steel-reinforced concrete beam-square steel tube (SST) column joint in which the SRC beam is embedded with a partial-length steel shape. Experimental tests are conducted on three joint specimens with varying cross-sectional dimensions of the SRC beam and lengths of the steel shape. The experimental results show that all the specimens exhibit good deformation, load-carrying capacity, and stable hysteresis responses. The three specimens demonstrate a considerable strength drop at drifts exceeding 5%. Besides, significant plastic deformation occurred at the column base region and in a limited region of the steel beam flange near the beam-column joint. Finite element models are developed to study the effects of single-side steel length, shear stud spacing, and thickness of beam concrete cover on the seismic performance of the proposed joint. The elastic deformations that caused the total column drift were theoretically analyzed. The predicted joint initial rotational stiffness using the proposed equation agrees well with the test and numerical results. The study’s limitations are also discussed.

Evaluating pod-based unsupervised damage identification using controlled damage propagation of out-of-service bridges

The effectiveness of Proper Orthogonal Decomposition (POD) for damage identification on out of service, rural bridges is examined using field data. Three similar, out of service, simply supported bridges, consisting of steel beams supporting a concrete deck, were tested prior to demolition and replacement. Strain time histories were recorded using optimal sensor networks with a vehicle of known weight crossed each bridge in different transverse locations and directions, and at varying speeds. The effectiveness with which the developed POD based methodology for damage identification was evaluated by progressively flame cutting select steel beam flanges and webs on each bridge. Snapshot matrices of structural response as measured by the sensors were used to create Proper Orthogonal Modes (POMs), and were obtained for each damage level and test, with the POMs being used to identify if changes in structural response were detected. The accuracy with which the POMs identified damage locations and their sensitivity to vehicle location and direction were evaluated. In addition, a previously developed novelty detection framework proposed by some co-authors was applied to identify changes after damage. It is shown that POD and the developed novelty index can effectively identify certain levels of imposed damage in tested bridges under known loads.

Numerical studies on the behavior of cold‐formed double‐channel shear connector

AbstractThe longitudinal shear forces are transferred through mechanical shear connectors at the steel beams and concrete slab intersection in composite beams. The shear connectors can be directly welded to the hot rolled steel beam, which is difficult in thin, cold‐formed steel beams. Thus, a cold‐formed double‐channel shear connector is proposed, and its suitability is investigated in this study. The double channel shear connector is a channel shaped shear connector formed from a flat plat and it is mounted on the flange of steel beam in pairs. The finite element model of the experimental Pushout test assembly was developed with the equivalent numerical constraints and interaction commands in a finite element software (ABAQUS). The developed models were fed with initial imperfection, load slip response, and material nonlinearity to achieve the proper experiment simulation. Initially, the developed models were validated against nine experimental test data reported by authors in the previous study. The parametric study was conducted to assess the behavior of cold‐formed channel shear connectors. The key parameters adopted in this study are the length of the shear connector, the grade of concrete and the grade and thickness of the steel connector. Three common failure patterns were witnessed among 107 numerical models. In this study, the factors influencing the control of failure patterns are presented, along with the factors influencing the shear connector's ultimate capacity.

Study on anti-progressive collapse performance of assembled steel frame joints with Z-type cantilever beam splices

A new type of joint with Z-type cantilever beam splices was proposed for assembled steel frame structures in this study. The basic specimen was designed based on the theory of bolt sliding energy dissipation, and three groups of specimens were obtained by changing key parameters. That is, there is no section weakening (Z-BASE), flange weakening of cantilever beam near column (Z-RBS), flange weakening of steel beam near splicing (Z-SRBS), and flange and web weakening of steel beam near splicing (Z-RBS-RWS). The effects of reducing beam section and beam web on the anti-progressive collapse performance of assembled steel frame joints with Z-type cantilever beam splices were studied. The test results were described in detail in general behavior, failure modes, deflection shapes, limit displacements, and resistance mechanisms. According to the test results, specimen Z-RBS had the best anti-progressive collapse performance, and its ultimate load and initial failure displacement were 116% and 114% higher than specimen Z-BASE, respectively. In addition, specimens Z-SRBS and Z-RBS-RWS also had better anti-progressive collapse performance than specimen Z-BASE. Moreover, the validity of the results was verified and study parameters were analyzed using ABAQUS. The assembled steel frame joints with Z-type cantilever beam splices had better anti-progressive collapse performance than ordinary cantilever beam assembled steel frame joints. And the bearing capacity and ductility of the structure were improved by increasing the distance from the cantilever beam splices to the failed middle column, a, and reducing the aperture of the bolt on the cantilever beam splices, b. However, reducing the number of bolts on the cantilever beam splices, c, exhibited the opposite influence. Based on the above comparisons, the proposed design details of assembled steel frame joints with Z-type cantilever beam splices are given.

Seismic behavior of exterior-diaphragm CFSST connections with or without PBL

The exterior-diaphragm connection to concrete-filled square steel tubular columns with perfobond ribs (i.e., exterior-diaphragm CFSST connection with PBL) is an innovative connection formed by arranging PBL in steel tube of the small-sized-exterior-diaphragm CFSST connection. To explore the seismic behavior of this type of connection, cyclic tests of exterior-diaphragm connections with or without PBL were carried out. The failure modes, P-Δ hysteretic curves, stiffness degradation, energy dissipation capacity, shear deformation of joint region, strain distribution in diaphragm and panel zone of different specimens were compared and analyzed. On this basis, the tensile force transfer paths in different connections were compared by FE numerical simulation quantitatively. It is found that PBL carry a considerable portion of the tensile forces from steel beam flanges and transmit them to core concrete in joint regions, and enable the core concrete to participate in tensile load transferring and then in horizontal shear resisting of the novel connections, which greatly alleviates the stress concentrating at corners of steel tubes and exterior-diaphragm, and decreases the shear deformation and strain in joint regions. So, the stiffness, ductility, load carrying and energy dissipating capacity of exterior-diaphragm connections with PBL are improved a lot. Higher axial load level reduces the shear stiffness and strength of concrete dowels, and then deteriorates the stiffness degradation, energy dissipation capacity and shear deformation of panel zone. Even if the dimension of exterior-diaphragm is much smaller than that specified in codes, the innovative connections under common and high axial load level have good seismic behavior and fail as the yielding of steel beam flanges without obvious damage in exterior-diaphragm and steel tubes.

Numerical investigation of steel-concrete composite (SCC) beam subjected to combined blast-impact loading

Existing literatures on combined effects of blast-impact loadings on steel-concrete composite beams are limited. In this study, behavior of steel-concrete composite beam subjected to combined blast-impact loading was investigated using LS-DYNA nonlinear FEA software program. The accuracy and reliability of developed FEA model was validated using experimental data reported in literature. Parametric studies were performed on impacting speed, concrete strength, various characteristics of H-structural steel, yield strength of studs and steel rebars to get insight into performance of composite beam subjected to combined blast impact loading. FEA results revealed that increase in specified cylindrical compressive strength of concrete, yield stress, flange and web thicknesses of H-type structural steel beam significantly improved dynamic response of a steel-concrete composite beam under combined impact-blast load case whereas yield stress of studs, and reinforcement steel bars showed insignificant contribution. Moreover, increasing impactor’s initial velocity significantly affects dynamic response of a SCC beam under combined blast-impact loading.

Torsional behavior ofI‐steel–concretecomposite beam considering the composite effects

AbstractTo investigate the mechanical behavior of composite beams under pure torsion, considering the torsional contribution of the steel beam flanges, we established finite element models of I‐steel–concrete composite beams. The nonlinear material constitutive relationship of concrete and steel was adopted in the model, and we validated the relationship by tests. Afterward, parametric analyses were carried out to study the main factors affecting the torsional performance of the composite beam. Our primary investigation focused on the composite effects and load sharing ratio of the steel beam and the concrete slab under pure torsion. We established the formulas for obtaining the maximum shear stresses in the concrete slab and the steel beam based on the composite effects and superposition principle. From these tests and our calculations, we proposed a model defining the torsional bearing capacity and the torsional stiffness of the I‐steel–concrete composite beam; thus, the torsional contribution of the concrete slab and the steel beam were a primary concern in this research. Bearing capacity formulas are also proposed herein and are comparable with those in the literature, demonstrating that our formulas, with simple forms, are highly reliable when predicting the torsional behavior of the composite beam.

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.

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.

Dynamic performance of retrofitted steel beam-column connections subjected to impact loadings

In this paper, three steel beam-column connections (welded flange-bolted web (WFB) connection, welded flange plate (WFP) connection and reduced beam section (RBS) connection) were experimentally examined under impact loadings. The impact tests using drop-hammer were carried out to simulate the dynamic behaviour of structural progressive collapse. The influence of strengthening or reducing methods on the impact resistance of steel frame substructure was discussed. The failure modes and the dynamic responses of the impact load and deformation time histories as well as the dynamic rotation and energy dissipation of the substructures were investigated. Test results showed that the upper flange of all specimens experienced local buckling near the plastic hinge section, while no welding seam cracked. For retrofitted connections, the out-of-plane and distortional deformation of steel beam flange and web at the plastic hinge section were measured. All the three connections with weld access holes recommended by American Federal Emergency Management Agency (FEMA) had good rotation abilities and impact loading resistances, and their ultimate rotations were not less than the FEMA350 design limits. The ductility and energy dissipation of two retrofitted beam-column connections were improved, which were better than those of un-retrofitted connections. The finite element analysis (FEA) models of steel beam-column connections were also established using ABAQUS software. The internal force development of connections during the impact loading was examined and the results showed that the strengthening or reducing methods had a profound influence on the formation of catenary action of beam-column connections under the dynamic progressive collapse scenario.

Study on seismic performance of prefabricated self-centering steel frame

Unexpected plastic damage and residual drift can be usually observed in traditional rigid-connection steel frames (RCSFs) after severe earthquakes. To enhance seismic performance of the RCSFs, this paper proposes a novel prefabricated self-centering steel frame (PSCSF) that incorporates pre-pressed composite combination disc spring (CCDS) installed in the column bases to provide satisfactory re-centering capability and eliminate residual deformation along with buckling restrained braces (BRBs) set at the bottom flange of steel beam to dissipate seismic input energy and reduce structural damage. Firstly, configuration details and design methodology of the PSCSF are introduced. A quasi-static loading test was conducted on the PSCSF specimen to investigate cyclic hysteretic response of the proposed innovative frame. Secondly, finite element analyses were performed with the aid of software ABAQUS to reveal seismic mechanism of PSCSF. Finally, the restoring force model of PSCSF was established based on mechanical analyses and theoretical calculation results were compared with experimental results to validate the correctness of the proposed model. The research results indicate that the PSCSF specimen exhibits full double flag-shaped hysteresis curves subjected to cyclic loading, demonstrating that the PSCSF possesses favorable self-centering capability and desirable energy dissipation capacity as well as stable mechanical behavior for the predefined target displacement. The beam and column maintain elastic and plastic damage is confined to the BRBs during entire loading process. The simulation results agree well with the test results, demonstrating that the established finite element model can capture cyclic response of the PSCSF under cyclic loading. The theoretical results calculated by restoring force model are in good accordance with the test results, confirming that the established restoring force model can reasonably predict the hysteretic behavior of the PSCSF under low cycle reversed loading.

Design method for the relocation of plastic hinges in prefabricated steel beams with corrugated webs.

The plastic hinge is a key factor in the ductile and plastic design of structures and an important basis for the seismic strengthening of structures. The formation and behavior of plastic hinges is critical for the seismic performance of an entire structure. The relocation of plastic hinges away from the beam end is an effective way of addressing brittle failure. In this paper, the cause of the shear buckling failure of prefabricated steel beams with corrugated webs and the strain variation at the flanges of steel beams are theoretically analyzed through structural tests. Based on the analysis results, a local strengthening method is proposed, and the effects of the beam sizes and the strengthening steel plate on the plastic hinges are obtained. In addition, a calculation method for determining the size of the strengthening steel plate that promotes the relocation of the plastic zone away from the beam end is given, a design method for plastic hinge relocation is proposed based on the test data, and its validity is verified.

Analysis of a more ductile connection between steel beams and concrete-filled tube columns

To resolve the problem of ductile fracturing of beam flanges in traditional connections with concrete-filled steel tube columns using site-welded side plates, an alternative connection design requiring minimal site welding was designed and studied. An explicit analysis method, considering the fracture strain criterion developed by the stress triaxiality path, was adopted to study the seismic performance and fracture resistance of the proposed connection. The results of a verified finite-element model indicated that the steel beam flange in the connection never fractured. The connection exhibited a notably higher maximum bending moment and ductility than the traditional connection. The side plates in the proposed connection were tension-bending or compression-bending elements, unlike in the traditional connection. The failure modes, maximum bending moment, ductility and stress distribution of the side plates were compared and analysed parametrically. Based on the stress distribution of the side plates according to the finite-element results, a fitting formula related to the width and thickness of the side plates was obtained. A formula to calculate the flexural capacity was also developed according to the force model of the proposed connection. The calculations and finite-element results were in good agreement.