T-shaped Section Research Articles

Residual stress tests and predictive model of friction stir welded normal-strength aluminium alloy H-shaped sections

To address the challenges of difficult extrusion for super-large cross-section aluminium alloy members, pairs of T-shaped sections were proposed to be longitudinally friction stir welded (FSW) to form the H-shaped sections widely used in structural engineering. It was significantly different from the previous member forming method that one web plate and two flange plates were welded at the flange-web junctions. To understand the novel FSW-induced residual stress distributions and magnitudes in the H-shaped sections, six specimens made of 6061-T6 and 6013-T6 normal-strength aluminium alloys, including various width-to-thickness ratio and plate thickness, were tested using the sectioning method, leading to over 4000 original readings of compressive and tensile residual stresses. The analysis results showed that great tensile residual stresses were clearly concentrated within the web weld, and then rapidly descended to lower compressive stresses near the weld region, followed by approximately linear regression to zero state from the weld edge to the flange-web junction, while the flange data points were relatively scattered. The compressive and tensile residual stresses in each flange and web plate were observed to be slightly associated with the width-to-thickness ratio and plate thickness. A simplified multi-linear residual stress distribution model, including the magnitudes and ranges of constant and linear variation curves, was proposed for the FSW aluminium alloy H-shaped sections, and good accuracy and consistency were observed between the test and predicted results.

Analysis of the Effect of Slenderness Ratio on Axial Force in T-Section

This study extensively investigates T-shaped axial compression members with varying wing-flange width-to-thickness ratios, focusing primarily on the influence of section width-to-thickness ratio and effective width on the sectional resistance. Based on the AISC 2017 specifications, assuming the overall component is a stable member, the study analyzes the impact of varying the wing-flange width-to-thickness ratio on the sectional stability and resistance of the structure. Especially for slender sections that exceed the width-to-thickness ratio limits specified in AISC 2017, it is necessary to consider the sectional resistance affected by local buckling. Therefore, the concept of reduced section is proposed - effective width constraint, which accurately reflects the actual resistance of the component. As the T-shaped section is a singly symmetric profile, a detailed analysis will be conducted on flexural buckling (FB) and flexural-torsional buckling (FTB) under various wing-flange width-to-thickness ratio conditions. Through the analysis of these two buckling behaviors, a more comprehensive understanding of the stability and resistance of T-shaped section members under different wing-flange width-to-thickness ratio conditions can be achieved. This study contributes to the understanding of the stability and cross-sectional solid of T-shaped members, providing insights for the design analysis of AISC2017-specified T-shaped section components. Particularly, it focuses on research related to section width-to-thickness ratio, slender section considerations, and sectional resistance. Further research is conducted on the issue of reduced resistance due to excessively slender cross-sections. This not only aids in better understanding the resistance of cross-sections but also provides practical design references. Therefore, this study holds research value regarding the analysis of the width-to-thickness ratio design for T-sections in the AISC 2017 specification, particularly when considering factors related to slender sections and cross-sectional resistance.

Cyclic behavior of improved low-yield point steel plate shear walls with T-shaped stiffeners

Based on the demand for high-performance lateral force-resistance systems for high-rise buildings, a new stiffened low-yield point (LY) steel plate shear wall (SPSW) structure is proposed. The infill plate is made of LY steel, and the stiffeners adopt a T-shaped section with greater flexural stiffness. Quasi-static tests are conducted on one unstiffened low-yield point steel plate shear wall (L-SPSW) and two stiffened L-SPSWs (using T-shaped cross and diagonal stiffeners). The cyclic behaviors of the L-SPSWs are compared through failure mode, damage development, hysteresis performance, and deformation performance. Numerical models are established and validated through experimental results. Finally, the performance of L-SPSWs with T-shaped and plate-type stiffeners is analyzed. The results show that the T-shaped cross stiffeners have the greatest enhancement in energy dissipation capacity (EDC) and stiffness, as well as the strongest suppression of the out-of-plane deformation (OPD) of the whole plate. T-shaped diagonal stiffeners have the greatest impact on enhancing the bearing capacity. It is suggested to strengthen the weld quality or select a steel material with LY for the diagonal stiffeners to ensure ductility. The use of T-shaped stiffeners can maximally improve the restraining effect on the OPD of the infill plate by 38.1 % compared with plate-type stiffeners.

An Investigative Study for the Seismic Performance of Composite-Reinforced Masonry Wall with Prestressing Technology

Prestressing technology is an effective way to improve the seismic performance of masonry structures such as concrete masonry wall. Therefore, bonded prestressing technology applied to integrated concrete masonry wall (ICMW) was proposed in this study, and a cyclic loading test on specimens with different section types was conducted. It was found that the prestressing technology rendered thinner and denser cracks on the load-bearing component of the specimens, while the failure mode remained unchanged. The prestressing technology increased the initial stiffness of the specimens and accelerated their stiffness degradation. Although the prestressing technology advanced the yield displacement of the specimens, it had a positive influence on the displacement ductility of the specimens. Additionally, the energy dissipation of the specimens increased with the deepening of the damage state, while the influence of the prestressing on the energy dissipation of the specimens decreased with an increased in the drift ratio. Furthermore, the equivalent viscous damping of the specimens with a rectangular and T-shaped section finally converged at 8% and 14%, respectively. Overall, the aforementioned findings indicate that the prestressing technology proposed in this study is a useful method for improving the damage propagation and seismic performance of ICMW, which could be used to construct low-rise masonry structures in the future.

Seismic performance of bolted connection between T-shaped section column and I-section beam with L-stubs

Bolted beam-to-column connections can reduce the construction period and are proper for prefabricated structures. Based on the traditional bolted connections, a beam-to-column bolted joint with L-stubs was proposed to connect the I-section beam and T-shaped section column using only bolts on site. Changing the parameters of L-stub end plate thickness, stiffener layouts, friction coefficient, column web thickness and the quantity of the beam flange bolts, experimental and numerical investigations were conducted on the cyclic performances of the proposed joint, and the hysteretic curve, skeleton curve, deformation characteristics, ductility and rotational capacity, as well as the slipping, yield and ultimate resistances, were analyzed. According to the results, the proposed joint can perform as a rigid joint without slipping under small earthquakes, and develop considerable ductility and energy dissipation ability under moderate or large earthquakes by slipping and plastic deformations. Increasing the friction coefficient can improve the slipping moment, and the stiffeners can improve the joints stiffness. The joint energy dissipation capacity could be increased by adding bolts. Based on the analysis, recommended parameter values for the joints were provided, and simplified formulas were proposed to calculate the slipping, yield and ultimate moment resistances, providing satisfactory accuracy when compared to the test and finite element results.

Study and Numerical Analysis on Seismic Performance of Concrete U-Shaped Shear Wall

Rectangular, L-shaped, and T-shaped section concrete shear walls in high-rise buildings are more frequently used in engineering and are widely studied. However, there are few studies related to the load-bearing performance of concrete shear walls with U-shaped sections. In this article, the seismic performance and damage mechanisms are analyzed in a systematic manner. In addition, a finite element model was developed using ABAQUS software, and numerical simulation was carried out. The damage forms and load-carrying capacity of shear walls with U-shaped sections were validated. Finally, reasonable suggestions and construction measures are given for the design of shear walls with U-shaped sections, and a benchmark is provided for relevant engineering applications.

Study on seismic performance of honeycomb stiffened rib shaped concrete filled steel tube columns

This paper presents concrete columns with inclined honeycomb stiffened rib steel tubes and proposes three special shaped cross-section columns to improve the overall force capacity of steel tube concrete columns on the basis of saving steel. Variables (type of section, direction of load application, honeycomb opening, strength class of concrete and steel) are set in this paper to investigate the seismic performance of inclined honeycomb stiffened rib concrete columns. The effect of honeycomb ribs on the seismic performance of shaped columns with different cross-sectional forms varies, and the improvement in cross-sectional performance is more obvious for T-shaped sections; the effect of load application direction is more obvious for asymmetric sections; the installation of honeycomb openings in stiffened ribs has a weak effect on the overall mechanical performance of the specimen, but the seismic performance in both directions is improved; the results are consistent when modeled using ABAQUS software and compared in tests. The setting of honeycomb holes in the stiffening ribs improves the bonding capacity of the stiffening ribs to the concrete, and the welding of the honeycomb stiffening ribs to the outer steel pipe improves the joint working capacity of the outer steel pipe and the concrete; the diagonal placement of the stiffening ribs improves the two-way seismic capacity of the shaped column. The new structural form of oblique honeycomb stiffening rib steel pipe concrete column is conducive to promoting the development of steel pipe concrete column.

Concept and analysis of resilient frictional shear connector for coupled system

Buildings designed using current seismic codes typically undergo significant structural damage and residual deformations under a design-level earthquake. To avoid this drawback in coupled structural systems, a novel resilient frictional shear connector (RFSC) that can improve both the energy dissipation capacity and structural resilience was proposed in this study. The RFSC is comprised of two T-shaped sections and two cover plates, which are clamped together by two arrays of pre-stressed high-strength bolts and disc springs. The equations governing the hysteretic loop of the coupled system using RFSC are first derived. Then three-dimensional finite element models were developed in Abaqus software for validating the RFSC and predicting the hysteretic response of the RFSC in the coupled system, respectively. Finally, a group of computational investigations of the RFFC in the coupled system subjected to static cyclic load are conducted to analyze the effect of varying key design variables such as the slope angle, the bolt preload, the spring stiffness and the friction coefficient. The parametric analysis confirmed the expected resilient behavior of the RFSC and explored the sensitivity of different parameters on the system responses such as stiffness, strength and equivalent damping ratio.

Buckling analysis and experimental study of simply-supported single-corrugation steel plates subjected to compression

High-strength steels (HSSs) have been increasingly used in construction, resulting in a more thin-walled component plate of steel members. In order to restrain local buckling in high-strength steel tubular columns, an innovative type of corrugated steel plates is proposed in this paper, which is named as the single-corrugation steel plate (SCSP). By utilizing the principle of minimum potential energy, a theoretical derivation is conducted to provide simplified formulas for calculating the elastic buckling stress of simply-supported SCSPs subjected to compression. Based on the parametric analysis, the optimal value of repeating number, trough angle, width and depth of the corrugation are recommended. Then, axial compressive tests are conducted on both L-shaped and T-shaped sections to investigate the buckling behavior of tubular columns composed of the SCSPs. The theoretical formulas are compared with the finite element results (ABAUQS/Buckle), as well as experimental results. The proposed formulas can make reasonable estimation on the buckling resistance of the SCSPs.

Damage and quantitative indexes for steel reinforced concrete column with T-shaped section

This paper presents an experimental investigation on damage performance of nine steel reinforced concrete (SRC) columns with T-shaped section under different loading paths. The monotonic loading, low cyclic reversed loading and mixed loading were applied to specimens along the flange of specimen. Furthermore, different axial compression ratios and steel ratios were used to study the damage of specimen. The failure modes were observed and the load-displacement curves were analyzed. The results indicate that the specimens mainly showed the feature of bending failure accompanied by bond failure characteristic at the end of loading. The load-displacement curve was plump and symmetrical without obvious pinch under the low cyclic reversed loading. The ductility coefficient lied within the range of 5.34–9.41, which indicates that these columns had better deformation capability. Based on the experimental results, a modified damage model considering deformation and energy dissipation was proposed, where the effects of concrete cracking, loading path and effective energy dissipation on damage were studied. Moreover, the damage index at each loading stage was calculated. Meanwhile, the level of seismic performance of SRC T-shaped column was divided into five levels, namely the normal use, the basic normal use, the temporary use, the post-repair use, and the near serious damage. Many SRC T-shaped columns were chosen as the analysis samples to obtain the displacement angles under different loading stages. Based on statistic results, the corresponding relationship between quantitative index of displacement angle and the damage index was established.

Compact Configured 5G Dual-Band MIMO Loop Antenna System

This paper presents a compact configured 5G dual-band MIMO loop antenna system for laptop computers. The antenna system consists of two identical 95 × 2 mm2 four-antenna units that are arranged on the top edge of the display ground plane and are 10 mm away from the left and right sides. The four-antenna unit, each being a two-dimensional loop antenna of the same structure and size, are constructed on the on a 0.4 mm-thick FR4 substrate. The loop antenna with only 23 × 2 mm2 size is composed of a T-shaped feed-in section and a double short-circuit loop. In addition, the four loop antennas are arranged in the same direction and side by side with only 1 mm space to form a high-isolation four-antenna unit. The two sets of four-antenna units can cover 5G dual-band operation at 3300–3600 MHz and 4800–5000 MHz. The measured isolation between eight antennas is all better than 15 dB, the measured antenna efficiency is between 35% and 62%, and the measured envelop correlation coefficient ECC calculated from the electric-field radiation pattern is all less than 0.2. This compactly configured eight-antenna system is only 2 mm high in profile, making it ideal for use in 5G laptops with a high screen-to-body ratio.

QUASI-STATIC CYCLIC TESTS ON THE HYSTERETIC BEHAVIOR OF BUCKLING-RESTRAINED BRACES WITH A T-SECTION CORE

An all-steel assembled buckling-restrained brace is proposed, in which both the core and the restraining members are made of section-steel. The brace has the advantages of assembly, replaceable core, easy fabrication, low cost and can be used for strengthening existing members. The steel core is composed of two angle steels and stiffening plates to form a T-shaped section. The restraining members are formed by bolting plates and angle steels through mat strips. Quasi-static cyclic tests for six specimens were carried out to investigate the hysteretic performance, seismic performance and failure modes. The effects of adding filler plates in the core, the gap between the core and the restraining members, the spacing between the two angle steels of the core, and the stopper configuration on the hysteretic performance were analyzed. The results show that the actual performance of the brace was basically consistent with the design performance. The brace specimens exhibited stable hysteretic performance. Adding filler plates in the middle of the core shows little influence on the hysteresis performance. An excessive gap between the core and the restraining member and excessive spacing between the two steel angles of the core reduced the hysteresis performance. The hysteretic performance of the braces with middle stoppers were better than the brace with end stoppers. The analysis of the seismic performance of the specimens shows that the braces have satisfactory ductility and cumulative plastic deformation capacity, which can be used as dampers in structures. By analyzing the failure modes, the stress concentration of the welding at the end of the stiffening plates will make the failure position move from the yielding segment to the stop of the weld. The middle stopper of the core can reduce the adverse effects of friction.

Experimental study of in-plane flexural behavior of screen-grid insulated concrete form rectangular and T-shaped walls

Screen Grid Insulated Concrete Form (SGICF) walls are gaining popularity in the construction of low and mid-rise buildings due to their unique constructability and insulation properties. In order to validate and ensure the safety of this novel construction system in the face of seismic loads, experimental testing aimed to provide information regarding its nonlinear behavior is of significant relevance. This paper aims to describe analytically and experimentally the in-plane flexural behavior of SGICF panels. An analytical model is presented to estimate the design parameters considering the material properties and the element geometry. Ten test specimens were constructed and tested under monotonic and cyclic in-plane lateral loading to assess the model's effectiveness. Test units were divided into two groups, each constructed using different prefabricated forms made of expanded polystyrene. The first group comprised six rectangular-shaped section walls whereas group two comprised four T-shaped section walls. All specimens were designed and detailed to obtain a flexure-controlled response, considering the presented analytical model. Results showed a ductile and stable response for all test specimens, with yielding of the longitudinal reinforcement and compression crushing of the extreme concrete fibers. This study shows that SGICF walls can reach large inelastic deformations, as well as a stable response, similar to that of conventional reinforced concrete (RC) walls with similar geometric properties. Furthermore, it was verified that flexural resistance models for solid cross-section RC members are applicable to Insulated Concrete Form (ICF) walls, taking into account section discontinuities.

Dimensioning of partially prestressed concrete beams, optimization of T-shaped section with heels

The present article addresses the structural optimization of partially and fully prestressed concrete bridge girders. For this purpose, an optimization-oriented dimensioning approach for prestressed concrete is proposed in accordance with the Eurocode 2 provisions, it combines all service and ultimate limit states verifications in a coherent manner. An optimization procedure, based on Genetic Algorithms, is conducted on a T-shaped section with heels, with the total cost as the objective function. The design variables are the cross-sectional dimensions, the steel reinforcement and quantity and configuration of prestressing tendons. The constraints include geometrical restraints and verifications under ultimate and service limit states. Numerical examples are implemented to demonstrate the performance and effectiveness of this method, and the results obtained are discussed with final remarks and conclusions.

Research on Carrying Capacity of T-Shaped Stiffened Concrete-Filled Steel Tubular Columns Subjected to Eccentrically Compressive Load

In this paper, in order to further study the mechanical behavior of T-shaped stiffened concrete-filled steel tubular (CFST) columns, numerical programs of eccentrically compressive T-shaped stiffened CFST columns were developed to calculate moment M-ϕ curvature curves of cross section and column. The calculated curves with the numerical programs agree well with the experimental results. A parametric analysis was carried out to calculate M-N correlation curves of cross section and column to investigate influence of concrete strength fck, steel yielding strength fy, steel tube thickness t, slenderness ratio λ, and loading angle θ. On the basis of parametric analysis, simplified resistance models of T-shaped CFST section and column were proposed and verified by the numerical analysis results. The simplified resistance models are reliable to predict the mechanical behavior for engineering application.

A new method for bearing design in the metal extrusion of profiled sections

Bearing design is a major issue in controlling material flow and producing high-quality extruded products. Adjusting the bearing length is often performed using costly trial and error approaches in the extrusion industry. This is true even when using finite element analysis. The purpose of this study is to optimize the bearing length of forward extrusion dies using an analytical approach for metal extruded sections. This method is based on a generalized kinematically admissible velocity field to obtain uniform velocity at the die exit. The deformation zone contains the dead metal zone (DMZ) and bearing channel which is assumed to be non-linear. Based on this assumption, a new formulation was developed to define the geometry of the deformation zone. The response surface methodology was employed to optimize the relative extrusion pressure, deviation of the mean value for the velocity at die exit, and subsequently the bearing length for the extrusion die. Using this theoretical method, extrusion of rectangular and L and T-shaped sections was investigated and compared to previous work. Physical modelling experiments and finite element simulations were carried out to validate the suggested analytical method. The proposed analytical method gave a unique answer for the required bearing design in a few seconds contrary to finite element method which required many timely and costly trials. This method would be useful for die designers to get the appropriate bearing length.

Experimental Investigation into the Seismic Performance of Fully Grouted Concrete Masonry Walls Using New Prestressing Technology

In recent years, traditional masonry structures have been widely used in rural areas of China. However, they were found to have a poor seismic performance during earthquakes. In this study, a new prestressing technology was proposed and described in detail, and it was used in fully grouted concrete masonry wall systems to improve its seismic performance. The experimental work involved investigating the seismic response of four fully grouted reinforced concrete masonry wall systems, consisting of two symmetrically arranged reinforced block masonry walls, with different section types and prestressing technologies, when subjected to cyclic lateral force. Based on the test results, a flexure and ductile failure occurred in the specimens with a rectangular section, while a shear and brittle failure occurred in the specimens with a T-shape section. The prestressing technology had no significant effect on the failure state of the specimens, but it influenced the crack propagation, making cracks fine and densely covered. A symmetrical and obvious pinching effect was observed in the hysteretic response of all specimens. The average displacement ductility of the specimens varied within a range of values between 3.34 and 6.92, according to the section type of the specimens, and the prestressing technology improved the displacement ductility of the specimens. Moreover, the prestressing technology significantly improved the initial stiffness of the specimens, and the specimens with prestressing technology experienced a greater fall in the degradation of the normalized stiffness than the specimens without this technology throughout the loading process. In addition, the equivalent viscous damping of the specimens ranged between 8.2% and 10.8%, according to the section type. It could be concluded that the prestressing technology improved the energy dissipation of the specimens at the ascending stage, although it had no marked influence on the equivalent damping ratio of the specimens.

General design equations for 3‐way unequal‐split Bagley power dividers

In this study, general design equations for 3-way unequal-split Bagley power dividers (BPDs) are systematically derived. The proposed design procedure allows for obtaining power dividers with the same split ratio but with different solutions for design parameters. Conditions are firstly derived to achieve a perfect input port matching, then, taken into consideration to divide the power unequally between the output ports. A technique to compensate the resulting impractical high-impedance transmission lines is presented, where such lines are replaced by their equivalent single- and dual-frequency T-shaped sections. To validate the derived equations, different dividers with different split ratios, specifically, 1:3:1, 1:10:1, 3:1:3 and 10:1:10 are designed and simulated. Furthermore, 3-way dual-band 10:1:10 BPDs are designed, fabricated and tested. Very good agreement between simulated, theoretical and experimental results is found.

Biomechanical behavior of an implant system of carbon fiber-reinforced polyether ether ketone (PEEK) bars with different designs: finite elements analysis

We used finite elements analysis to assess the biomechanical behavior of lower protocol bars made of Polyether Ether Ketone (PEEK) reinforced by carbon fiber, with different designs on All-on-four® system, subjected to physiological occlusal loads. The models were built to have an I-shaped or an inverse T-shaped section. We also assessed the stress distribution on the peri implant bone, implants, prosthetic intermediates, prosthetic intermediate screws, and prosthetic screws. In the simulations, strength peaks were similar for both inverse T and I shaped models; however, the I-shaped bars showed larger resistance in comparison with the inverse T shape. Since it is a new material in dentistry, further research is necessary for a better assessment of PEEK's mechanical and clinical performance.

Experimental Research on Static Behavior of Stiffened T-Shaped Concrete-Filled Steel Tubular Stubs Subjected to Concentric Axial Loading

Eight stiffened T-shaped concrete-filled steel tubular (CFST) columns and one non-stiffened T-shaped CFST column were tested subjected to axial compressive load in this paper. The mechanical property and failure mode of the specimens were studied. The influences of steel ratio, concrete strength and sectional size were investigated on the axial compressive performance of the specimens. A numerical program was developed to calculate concentric load-shortening curves of T-shaped CFST columns based on experimental results. The confined concrete distribution in T-shaped section and the stiffened tube’s local buckling were considered in the numerical program. A good agreement between calculating results and experimental results was obtained. Besides, a design formula of bearing capacity of stiffened T-shaped CFST columns was put forward by considering favorable effect of stiffeners.