T-shaped Steel Research Articles

Thermomechanical behavior of Glulam-beam connected to CLT-wall assemblies with steel doweled connections before, during and after fire

PurposeThermomechanical behavior of intermediate-size beam-to-wall assemblies including Glulam-beams connected to cross-laminated timber (CLT) walls with T-shape steel doweled connections was investigated at ambient temperature (AT) and after and during non-standard fire exposure.Design/methodology/approachThree AT tests were conducted to evaluate the load-carrying capacity and failure modes of the assembly at room temperature. Two post-fire performance (PFP) tests were performed to study the impact of 30-min (PFP30) and 60-min (PFP60) partial exposure to a non-standard fire on the residual strength of the assemblies. The assemblies were exposed to fire in a custom-designed frame, then cooled and loaded to failure. A fire performance (FP) test was conducted to study the fire resistance (FR) during non-standard fire exposure by simultaneously applying fire and a mechanical load equal to 65% of the AT load carrying capacity.FindingsAt AT, embedment failure of the dowels followed by splitting failure at the Glulam-beam and tensile failure of the epoxy between the layers of CLT-walls were the dominant failure modes. In both PFP tests, the plastic bending of the dowels was the only observed failure mode. The residual strength of the assembly was reduced 14% after 30 min and 37% after 60 min of fire exposure. During the FP test, embedment failure of timber in contact with the dowels was the only major failure mode, with the maximum rate of displacement at 51 min into the fire exposure.Originality/valueThis is the first time that the thermomechanical performance of such an assembly with a full-contact connection is presented.

Effects of core air gaps and steel inserts on thermal response of GFRP-balsa sandwich panels subjected to fire

Sandwich systems composed of combustible glass fiber-reinforced polymer (GFRP) face sheets and balsa cores must fulfill fire resistance requirements if used, for instance, in bridge or building construction. Air gaps and steel inserts in the balsa core, the latter to suspend external pipes below bridge decks for example, may therefore present critical zones where heat ingress is facilitated, and fire resistance is therefore reduced. The thermal responses of such GFRP-balsa sandwich panels comprising through-thickness air gaps or steel inserts, and subjected to a one-sided external fire, were thus investigated by furnace experiments and fluid-structure interaction simulations. Through-thickness air gaps and steel inserts between the face sheets cooled the surrounding zones close to the hot face and heated those located towards the cold face. In T-shape steel inserts penetrating the bottom face sheet, the fire-exposed flange collected the heat and the whole section around the insert was significantly heated. The results revealed that the remaining cross section might be considerably reduced by char formation around the air gaps and steel inserts. Although the effect is quite local, it may be significant if slabs are unidirectional or if it occurs at critical locations, e.g., in the vicinity of supports.

Cyclic tests and parametric analyses of steel grid shear walls

This study proposed a novel steel grid shear wall (SGSW) composed of bidirectional diagonal steel grid members and a boundary frame, in which the steel grid members are connected to the boundary frame through fishplates. The lateral resistance performances of the steel plate shear wall (SPSW) and SGSWs were compared. Subsequently, three 1:2 scale specimens were tested under lateral cyclic loading, and the mechanical properties of the SGSWs were investigated. The failure modes of the specimens corresponded to the destruction of steel grid members. A finite element analysis (FEA) model of the SGSW was established, and the FEA model was confirmed to be able to accurately simulate the behaviors of SGSWs by comparing the numerical results with test data. Parametric analyses were then conducted through FEA to determine the influence of the T-shape steel section, vertical loads, and boundary column stiffness on the mechanical properties of SGSWs. The results demonstrated that SGSWs exhibited excellent stiffness, ductility, and bearing capacity. The changes in the T-shape steel web area and stiffness of the boundary column had a significant influence on the mechanical properties of the SGSWs.

Axial compression behavior of core-steel tube with T-shaped flanges reinforced concrete column

A novel core-steel tube with T-shaped flanges reinforced concrete (CSTRC) column is proposed. The steel skeleton of CSTRC columns consists of a core-steel tube with T-shaped steel welded around the steel tube. Ten CSTRC column specimens and one contrast specimen without core-steel tube are tested to examine their axial compression behavior. The effects of the cross-section form of core-steel tubes, the steel flange width, steel flange thickness, steel web height, and volume ratio of stirrups on the failure mode and bearing capacity of CSTRC column are also methodically investigated. Furthermore, finite element models are developed to conduct parametric studies to determine how the strength of both the concrete and the steel skeleton affects the bearing capacity and ductility. Finally, a calculation formula to predict the axial compression bearing capacity of CSTRC columns is established. The test results reveal that: (1) compared with the contrast column, all CSTRC columns exhibit good bearing capacity, with a better deformation regime; (2) the cross-section form of core-steel tubes has little influence on the bearing capacity of CSTRC columns, but demonstrates great impact on its ductility. Additionally, growing the width and thickness of the steel shape flange and lessening the stirrup spacing enhances the ductility of CSTRC columns; (3) increasing the strength of both the concrete and the steel skeleton improves the bearing capacity of columns, but decreases the ductility; (4) the prediction results calculated by the proposed approach agree well with the experimental results, which confirms the suitable accuracy of the proposed method.

Study on dynamic behavior of tubular T-joints subjected to out-of-plane impact loading

In this study, the failure mode, impact resistance, and other key factors affecting the deformation of T-shaped circular steel tubular joints subjected to out-of-plane impacts are studied using a combination of numerical and analytical methods. The finite element (FE) analysis for circular hollow section (CHS) tubular T-joints subjected to in-plane impact is carried out. The simulation results are in good agreement with the test results, and the error is <6%. For common joint sizes in engineering, 63 FE models of CHS tubular T-joints subjected to out-of-plane impacts are created, and the deformation patterns and impact force development processes are described. In particular, following previous research into the deformation laws of steel tube structures, this study proposes a modified equal area axis method and utilizes it to distinguish the bending displacement and local indentation. Using the displacement changes and research results for T-joint failure modes, the criteria for judging the failure modes of the specimen are proposed, and the failure mode is categorized into three types. By discussing the influence of four parameters [length-to-diameter ratio of the chord (α), diameter ratio of the brace-to-chord (β), impact energy (Ek), and length-to-diameter ratio of the brace (αh)] upon the joint deformation of the specimen, a prediction formula for the global and local deformation of a T-shaped steel tube joint under out-of-plane impact loads with respect to the four abovementioned parameters is obtained via data fitting, and the accuracy of the formula is verified via error analysis.

Investigation of the punching shear behaviors of reinforced concrete slab–steel reinforced concrete L-shaped column connections

To study the punching behaviors of reinforced concrete (RC) slab–steel reinforced concrete (SRC) L-shaped column connections, four slab–column connection tests were designed and completed, and a new punching shear resistance measure proposed. The test variables were column section shape, slab thickness and column cap. The test results show that the failure mode of L-shaped column was mainly two-way shear. Meanwhile, increasing slab thickness and installing column cap can effectively improve the ultimate bearing capacity of the slab–column connection. The punching angles formed by the punching cone and horizontal direction at the final failure of the connection were between 23.5° and 49.5°. In addition, a numerical simulation analysis was carried out using ABAQUS software, and the effects of various parameters on the performance of slab–column connections were studied. It was found that the change of column section shape will lead to more complex shear stress distribution and stress concentration phenomenon. However, the punching capacity of the special-shaped column was higher than that of the equivalent square column with the same section area. As a new punching shear resistance measure, inverted T-shaped steel can effectively improve the ultimate bearing capacity of the connections. In addition, when the ratio of slab thickness to web width of inverted T-shaped steel was less than 0.75, the failure mode of the connection changed from brittle punching failure to flexural failure.

Experimental and theoretical study on concrete-filled T-shaped steel tubular columns under uniaxial eccentric compression

This paper presents an experimental and theoretical study on concrete-filled T-shape steel tubular (CFTST) beam-columns. Four full-scale slender beam-columns with slenderness ratio of 33.7–39.1 were tested under uniaxial eccentric compressive loads. In addition, three stub columns with the same cross-sections were axially compressed to investigate the confinement effect. Failure mode, axial displacement, lateral deflection, axial strain and hoop strain were obtained to understand the structural behavior of CFTST beam-columns. For beam-columns bended about the symmetric axis, torsion was not observed but a slight rotation of the neutral axis that was no longer parallel to the centroid axis was found by analyzing the experimental results. A fiber element model for CFTST beam-columns was developed and verified for parametrical analysis. The effects of key parameters, such as material properties, cross-section dimensions, loading angle and slenderness ratio, on the behavior of stub and slender beam-columns were investigated. Finally, theoretical models were proposed to estimate the interaction curve and the load-carrying capacity of CFTST beam-columns. The prediction matches well with the experimental results.

Finite element analysis of static performance of new fabricated double-layer upper flange composite beam

A new type of fabricated double-layer upper flange composite beam section is proposed to meet the requirements of greater structural headroom. The influence of the strength of cast-in-place concrete on the static performance of composite beams was studied by using finite element analysis method. The static performance of the new fabricated double-layer upper flange composite beam with the strength of cast-in-place concrete is obtained. Numerical simulation results show that with the increase of concrete strength, the bearing capacity of composite beams will increase to a certain extent. At the same time, there will be obvious stress concentration at the openings of the T-shaped steel web on the upper part of the section. In the actual design process, the distribution and shape of the openings still need to be optimized. In addition, the influence of span-to-height ratio and aspect ratio on the bearing capacity of new cross-section composite beams is also studied. The results show that the best span-to-height ratio and aspect ratio of the new section beam proposed in this paper are 15 and 4/9, respectively.

Seismic behavior of 3-D beam to L-shaped concrete encased steel composite column joint: An experimental study

Experimental investigations were conducted on the behavior of three-dimensional (3-D) beam to L-shaped concrete encased steel (CES) composite column joint under seismic loading. A total of nine corner joints, including eight joint specimens with steel beam and one joint specimens with CES beam, were designed and tested. Test variables included the configuration of encased steel, axial compression ratio, loading angle and beam type. Failure patterns, hysteretic relations, deformation and strain distribution of these joints were recorded and analyzed. The seismic behavior was evaluated from peak load, stiffness and strength degradation, ductility and energy dissipation for these specimens. Test results indicated that the mixed failure mode acted on 3-D L-shaped CES column joint, including compression-shear failure in the joint core and bending failure at the beam-column connection. Seismic behavior of specimen with solid-web steel and T-shaped steel truss was much better than that of specimen with U-shaped steel truss. As the loading angle decreased from 45° to 0°, the peak load of joint specimen decreased continuously. Although reasonably increasing the axial compression ratio improved the bearing capacity and energy dissipation capacity of joint specimen, it also degraded the ductility and collapse resistance. Moreover, the joint with CES beam had better seismic behavior compared with joint with a steel beam. In this study, the ultimate drift ratio of all joint specimens exceeded the minimum limit of 1/50 in Chinese and American codes, indicating that 3-D L-shaped CES column joint had excellent collapse resistance.

Axial and hysteretic behavior of T-shaped steel–concrete composite shear walls

Multi-partition steel tube formed T-shaped composite shear wall is a new type of composite wall which enhances the structural performance compared to a traditional composite shear wall. To clearly understand the behavior of such shear walls, eight half-scaled specimens were tested to study their axial and seismic behavior. The failure mechanism, structural behavior and energy dissipation ability were observed according to the experiments. The axial experiments showed that the strength of such cross-section was higher than the sum of capacities of concrete and steel tube as the multi-partition steel tube could confine the concrete well. Meanwhile, the ductility of specimens was good. For seismic experiments, the specimens exhibited high strength, good ductility and excellent energy dissipation ability. When the axial load ratio increased, the lateral load resistance capacity and energy dissipation capacity increased obviously. Although the axial load ratio was beyond the limitation of the current Chinese standard, the drift angle could still satisfy the requirement of the standard. The experimental results were used to compare with those calculated results according to some codes including EC4, CECS and AISC.

Seismic performance of bolted double-web T-stub connections with T-shaped steel column

Bolted connections are convenient for construction, but traditional bolted end-plate joints require gaps for construction, which may cause construction difficulties and installation stress. Bolted T-stub joints could avoid the installation stress, but use more bolts. Improving the traditional bolted T-stub joints, a bolted beam-to-column joint configuration using double-web T-stubs and pallets, with less bolts required, was proposed. Cyclic tests and finite element analysis were conducted to analyze the effect of stiffeners, the column web thickness, the end plate thickness of T-stubs and L-stubs, and the beam flange bolt quantity on the performances of the novel joint, e. g. the deformation characteristics, the hysteresis curve, the skeleton curve, the slipping resistance, the yield resistance, the ultimate resistance, the ductility and the rotational capacity. According to the results, the joint could be designed as rigid under small earthquakes or wind loads, and may dissipate the energy mainly through slipping under moderate and large earthquakes to reduce the plastic deformation demand of the beams. Stiffeners of the double-web T-stubs and pallets can increase the joint stiffness and energy dissipation capacity, and more bolts on the beam flanges can increase the joint energy dissipation capacity and resistance. Formulas to calculate the slipping resistance, the yield resistance and the ultimate resistance are derived, providing results are in good agreements with the experimental and finite element results.

Behavior of T-shaped CFST column and U-shaped steel-concrete composite beam joints

This paper intends to study the seismic and shear behavior of joints for T-shaped concrete-filled steel tubular (CFST) column and U-shaped steel-concrete composite beam (USCB). In the joint details, the C-shaped slots cut in the T-shaped steel tube allowed the double-C channels used to connect the thin-walled U-shaped steel (USS) passing through the panel zone directly. A total of six full-scale specimens constructed according to the concept of strong column-weak beam were tested: two specimens were tested under the monotonic loading to obtain the load-carrying capacity and the other four specimens under cyclic loading to evaluate the seismic performance . The variables included the details of USCB, the axial load level, and the beam-column linear stiffness ratio . Test results demonstrated that the proposed joint details exhibited good seismic and shear performance. Three typical failure modes, i.e. welding fracture between the double-C channels and the steel tube, local buckling of the steel tube, and fracture of the double-C channels were observed. Some indexes of seismic performances, such as load-carrying capacity, deformability , degradation of load-carrying capacity, stiffness degradation , and energy dissipation capacity were evaluated. Finally, the joint shear resistance of the specimens was discussed according to the ASCE design guidelines. • An innovative joint details for T-shaped concrete-filled steel tubular column and U-shaped steel-concrete composite beam was proposed. • Some indexes of seismic performances for the joints, such as load-carrying capacity, deformability, degradation of load-carrying capacity, stiffness degradation, and energy dissipation capacity were evaluated. • The joint shear capacity was evaluated according the methods given by the ASCE Task Committee and by the previous findings of the authors.

Experimental Study and Analysis on Rotational Behavior of Bamboo Scrimber Beam-to-Column Bolted Connections

This paper studies the rotational behavior of beam-to-column bolted connections in bamboo scrimber structures. Three types of beam-to-column connections, including bolted connections with outer-clamping steel plates, bolted connections encased with T-shaped steel plates, and bolted connections encased with double L-shaped steel plates, were designed and tested under monotonic or reversed cyclic loads. The influence of bolt arrangement on the mechanical properties was also studied. Failure of the connections was mainly caused by cracking of the adhesive interface near the bolt at the tensile side of the beam, which was a weak point that needs further attention. The elastic stiffness, capacities, ductility coefficient, and energy dissipation capacity of the T-steel connections improved compared with the I-steel connections. The load-carrying capacities of the connections were calculated according to common standards. Results showed that for the I-, T-, and double L-steel connections, the different standards had different safety margins.

Mechanical properties of modular prefabricated steel-concrete composite internal joints under cyclic loading

To investigate the influence of the key parameters on the mechanical properties of modular prefabricated steel-concrete composite internal joint (MPCIJ), finite element model (FEM) of MPCIJ under cyclic load was established by using the finite element analysis (FEA) software ABAQUS, based on test results. FEA results were then compared with the test hysteresis curves, skeleton curves, and failure mode. Based on the verification of reliability of the numerical model, the influence of different parameters on the structural performance was analyzed. According to test and FEA results, the MPCIJ shear mechanism and bearing capacity calculation formula were proposed. Results showed that MPCIJ bearing capacity and deformation performance increased with increasing axial compression ratio (n < 0.45), however, the increase was within 5%. With the increase of concrete strength, the joint bearing capacity and fire resistance and corrosion resistance of joint modules were effectively improved. The recommended width/thickness ratio of the square steel tube should not be less than 17. Reducing the distance between the bolt edges could improve the plastic deformation of the joint module with the recommended value of 25–35 mm. The bolt hole diameter increase should be between 1.5 and 2 mm. MPCIJ bearing capacity increased with increasing thickness of joint cover plate and the peak load increased by about 17%; however, the shear deformation inside the joint module also increased. The shear mechanism of MPCIJ is the ‘steel plate shear wall’ and ‘T-shaped steel frame’. The correctness and reliability of the MPCIJ shear capacity formula were verified.

Numerical analysis of damping behaviors for T-shaped steel structures with acoustic black hole using FEM

Numerical analysis of damping behaviors for T-shaped steel structures with acoustic black hole using FEM

Strength gains of the axially and laterally loaded composite columns based on the concrete confinements provided by steel cores encased in structural concrete

ABSTRACT Most of the design codes for the composite columns including American Concrete Institute do not account for the concrete confinements offered by the steel cores encased in the concrete section. However, the flexural capacities of the axially and laterally loaded composite columns were substantially underestimated as the axial load increases if the concrete confinement provided by a steel core is not considered. The aim of this study was to identify the structural gains of the composite columns with the cross-, H- and T-shaped steel cores encased in the concrete when the concrete confinement provided by the steel cores is taken into consideration. The formulation of the flexural strength considering the confining effects provided by the transverse reinforcements and cross-shaped steel cores for the maximum load limit state was presented with a 50% axial load of the nominal column capacity. The formulation for an ultimate load limit state with a 40% axial load of the nominal column capacity is listed in the Appendix. The design charts were presented for the strain ranges between 0.001 and 0.01, leading to gaining the strengths of the composite columns that have been lost when the confining effects provided by the steel cores were ignored.

Experimental study on the dynamic behavior of T-shaped steel reinforced concrete columns under impact loading

This paper reports an experimental investigation into the behavior of axially loaded steel reinforced concrete (SRC) columns subjected to impact loads. A total of seven SRC columns with T-shaped steel skeleton were prepared and tested using a drop hammer impact system. The testing variables include the impact height, stirrup spacing and the axial compression ratio. The impact force time histories and lateral displacements at mid-span and quarter-span were recorded and analyzed. The experimental results indicated that the decrease of stirrup spacing resulted in a smaller lateral deflection. Axial load was also found to have a strong influence on the residual deflection of columns subjected to impact loading. In addition, the finite element analysis models, which considers the effects of strain rate of steel and concrete as well as the axial loads, were established to simulate the experiment. The FEA results are proved to agree well with that of experiment. The findings obtained from this study can facilitate the application of SRC columns in improving the impact-resistant performance of bridge and building columns.

Comparison of four different internal fixation methods in the treatment of distal clavicle fractures

This study compared the clinical efficacy of four internal fixation methods in the treatment of distal clavicle fractures, in an effort to guide appropriate selection and application in the clinic. Eighty-four patients with distal clavicle-comminuted fractures were treated with a distal clavicle anatomic plate (group A), clavicular hook plate (group B), double-plate vertical fixation (group C), or T-shaped steel plate internal fixation (group D). The Constant-Murley scoring system was used to evaluate the shoulder joint function. The fracture healing time, VAS, and postoperative complications were compared and analyzed among the four groups. According to the Constant-Murley evaluation standard, the excellent and good rates of the four groups were 94.4, 73.1, 95 and 80% in groups A-D, respectively. The excellent and good rates of Constant-Murley evaluation standard in groups A and C were significantly better than those in groups B and D (P<0.05). VAS in the distal clavicle anatomic plate group (group A), double-plate vertical fixation group (group C), and T-shaped steel plate internal fixation group (group D) were significantly better than the clavicular hook plate group (group B) (P<0.05). The incidence of postoperative complications in the clavicular hook plate group (group B) was 15.4% and in the T-shaped steel plate internal fixation group (group D) was 15%, which were significantly higher than those of the distal clavicle anatomic plate group (group A) and double-plate vertical internal fixation group (group C) (P<0.05). The treatment of distal clavicle fractures using either one of the four internal fixation techniques can obtain better clinical results. The distal clavicle anatomic plate and double-plate vertical internal fixation techniques are associated with a decreased incidence of shoulder pain, an increase in the range of motion of the shoulder, and a reduction in complications, and thus, are preferable for the early functional recovery of limbs.

Controlling the in-service welding parameters for T-shape steel pipes using neural network

One of the most common practices in petrochemical and power generation industries is “in-service welding,” and the possibility of a catastrophic event known as “burn-through” in this process may lead to financial or even human losses. To reduce the risk of burn-through, it is necessary to simulate the process and study the effects of controlling parameters. In this paper; firstly, a finite element based numerical model is developed using a model updating method and experimental data. The model is employed to simulate the in-service welding of a T-shape steel pipe connection. Then, the effects of the main parameters on this process such as heat input, welding speed, pipe thickness, fluid flow and especially material properties are investigated. Finally, the experimental data together with a large set of results produced by the numerical simulation are used to compose a user-friendly computer code based on the neural network algorithms to predict the temperature levels in the critical points for different welding conditions. The output of this code can be used in the industrial environment to prevent burn-through accidents during the in-service welding.

RESEARCH ON THE SEISMIC BEHAVIOR OF FRAME STRUCTURES WITH T-SHAPED STEEL REINFORCED CONCRETE COLUMNS AND STEEL BEAMS

To study the seismic behavior of frames with T-shaped steel reinforced concrete columns and steel beams, a pseudo-static test of a 1/3 scaled, 3-story 2-bay specimen was carried out. The main results such as the failure pattern, hysteretic and skeleton curves were obtained. The ductility, energy dissipation capacity and degradation of stiffness and strength of the specimen were analyzed. Numerical simulations were conducted with the fiber model to study the effects of different design parameters such as the axial compression ratio, steel ratio and concrete strength on the seismic performance of the frame. It was demonstrated that the specimen exhibited a beam-hinge failure mode under the condition of horizontal cyclic loading. The specimen had good ductility and energy dissipation capacity and it met the seismic design requirements of strong column-weak beam, strong shear-weak bending and strong joint-weak pole. The axial compression ratio has great influence on the performance of the specimen after yielding. With the increase of the axial compression ratio, the strength and ductility of the structure will decrease. It is necessary to control the axial compression ratio in a reasonable range in the design. The steel ratio mainly affects the initial stiffness and ultimate strength, while its increase can effectively improve the seismic performance of the frame. The increase of concrete strength can increase the ultimate strength of the structure, but reduce the ductility slightly. It is of great significance to consider concrete strength comprehensively in the design. The research results can provide reliable support for the design of this kind of structures.