Rectangular Steel Research Articles

Proposing New Standard and ANFIS Calculation Approaches for Precast Concrete Connections with Steel Tube Elements: Lessons from Experimental Studies

The importance of establishing a proper method for calculating newly studied structural elements and primarily translating the results of experimental and numerical analyses into practical standards poses a significant challenge for structural researchers. In this study, which focuses on the importance of previously studied connections for the precast industry as a case study, two approaches are proposed for calculating the capacity of elements connected by rectangular steel tubes. The first approach involves a step-by-step calculation for analyzing the forces and capacities of different steel tube or concrete section parts under bending and shear, aiming to establish a standard calculation approach. Despite its complexity, the standard calculation approach has proven its accuracy by successfully solving examples with features similar to those of the experimental tests describing the process. The second approach relies on a look-up table generated from experimental data, developing an Adaptive Neuro-Fuzzy Inference System (ANFIS) for interpreting the data. ANFIS not only facilitates the evaluation of the capacity of non-experimentally tested elements but also resembles the calculation process. Evaluating ANFIS’s performance concerning the original results underscores its remarkable capacity to analyze experimental data. With a maximum calculation error of only 13% when compared to the experimental tests, ANFIS demonstrates considerable accuracy and user-friendliness. Following the initial internal force evaluations, the proposed standard calculation method requires eight specific control inputs, and comparing these inputs with experimental tests further confirms the effectiveness and safety of this approach for connection design.

Experimental investigation on axial compressive performance of rectangular multi-cell stocky concrete-filled steel tubes stiffened with PBL

An experimental investigation on the structural performance of rectangular multi-cell stocky concrete-filled steel tubes (CFSTs) stocky stiffened with perfobond leiste (PBL) under compression. Compression tests were conducted on 12 stocky CFSTs, varying concrete strengths, number of cells, and cross-section shapes. The tests discussed the failure process, load-deformation behaviours, section capacities, ductility factors, and core concrete enhancement factors of the specimens. It was found that all the 12 tested CFSTs experienced local bucking, and owing to the inclusion of PBL, the short sides of the steel tubes exhibited double-wave bulging, while the long sides showed multiple-wave bulging. With the enhancement of concrete strength from 29.4 to 65.1MPa, the section capacity exhibited a significant increase of 18–30%. As the cell number increased from 1 to 3, the section capacity increased by 1.35–1.59 times. When the cross-section of triple-cell CFSTs changed from the I-shape to the L-shape, the section capacity only increased by 3–9%. Moreover, the enhancement factor of the core concrete and the confinement factor showed a significant correlation. The comparison between test capacities and predicted capacities using the methods given in design codes ANSI/AISC 360-16, EN 1994-1-1, and GB 50936-2014, as well as proposed by Zhang, revealed that the capacity ratios of predicted values to experimental values ranged from 0.63 to 0.89, indicating an overly conservative prediction. Considering the confinement factor, a modified design method, based on Zhang’s method was proposed, to more accurately predict the section compressive capacity of rectangular multi-cell stocky CFSTs stiffened with PBL.

Research on multi-objective topology optimization of unmanned sightseeing vehicle frame based on Analytic Hierarchy Process

To optimize the frame of a sightseeing vehicle, this paper proposes a multi-objective topology optimization method combining Analytic Hierarchy Process (AHP) and topology optimization. Firstly, the edges of the unmanned sightseeing car are statically analyzed. The rectangular steel frame structure of the original frame is replaced with square plates, the basic model of the unmanned sightseeing car frame is established, and a single-objective topology optimization mathematical model of the frame is established to optimize the topology design of the frame. Then, in order to design a frame structure that meets all the working conditions at the same time, a mathematical model of multi-working condition topology optimization is established, and the weights of each working condition are determined by using AHP, and the multi-working condition topology optimization design of the frame is carried out. Finally, a comparison of the comprehensive performance of the frame before and after optimization shows that the proposed method enables the optimized frame to meet the strength requirements under various working conditions, resulting in a weight reduction of 16.5 kg.

Behavior of CFRP confined rectangular high-strength concrete-filled steel tubular columns under eccentric compression

This paper presents an experimental study on the eccentric compression behavior of rectangular high-strength concrete-filled steel tubular columns confined with carbon fiber reinforced polymer (CFRP- CFST). Seventeen specimens were tested under eccentric compression, examining key parameters involving eccentricity, number of transverse CFRP layers, slenderness ratio, corner radius, CFRP partial wrapping scheme, and CFRP orientation. The effects of these parameters on failure mode, load-displacement relationship, strain development, and ultimate mechanical properties were analyzed and discussed. The ultimate bearing capacity (Nu) of CFRP-CFST columns improved with an increase in transverse CFRP layers, corner radius, and CFRP wrapping proportion, while it decreased with increasing eccentricity and slenderness ratio. Partial wrapping schemes reduced the effectiveness of CFRP confinement, with the outward local buckling of the steel tube primarily occurring in areas without CFRP confinement. Longitudinal CFRP provided less improvement to Nu compared to transverse CFRP under small eccentricity conditions. A theoretical model based on the fiber element method was developed to predict the ultimate bearing capacity and implemented through a custom program to facilitate calculations. The model was validated using a test database comprising results from this study and previous research. Additionally, axial force-bending moment (N-M) interaction curves were rapidly generated, providing a theoretical basis for the design and practical application of CFRP-CFST columns in practical engineering.

Study on shear performance of BMSCC prefabricated shell and square steel tube composite permanent formwork beam

A novel type of permanent formwork (PF) concrete beam has been proposed with the aim of reducing carbon footprint, conserving energy, and enhancing construction efficiency. Specifically, the U-shaped PF is constructed using basic magnesium sulfate cement mortar, and square steel pipes with holes are utilized in place of traditional vertical and horizontal reinforcements. During on-site construction, the composite beam can be easily completed by pouring ordinary concrete into the PF. Shear failure tests were conducted on two PF beams and a reinforced concrete (RC) contrast beam with varying strip spacing. It was observed that the remaining rectangular steel strips, resulting from opening holes on both sides of the square steel pipe, acted as shear stirrups. The results indicate that the PF beam demonstrates typical shear and compression failure, and the precast shell is securely bonded to the core concrete without any peeling phenomenon. When comparing to an equivalent RC beam with the same transverse steel yield strength and dosage, the cracking load of the inclined section is increased by 28.3 % and the ultimate load is increased by 21.4 %. Compared to RC beams, PF beams exhibit an increased number of cracks but reduced width. And The ductility of PF beams were improved. Decreasing the distance between steel strips on both sides of the PF beam results in an 10.3 % increase in cracking load and a 9.4 % increase in ultimate load. By introducing the concrete constraint coefficient and the steel tube web resistance coefficient, the formula for calculating the shear capacity of the PF beam was established.

STEAM INDUCED SHOCKWAVE INTERACTION WITH A SUBMERGED PLATE CONFIGURED AT A RANGE OF INCLINATIONS FROM VERTICAL

Interaction of shock wave and the shear induced vortex across the steam-water layer has been vital in several transportation and chemical industrial processes. Experiments were conducted using a facility including a rectangular chamber, which housed a shock tube in it. Steam was injected into the tube to induce shock wave by bursting the Aluminum diaphragm disk and the shock wave surrounding by the steam-water shear layer induced vortex, exited the shock tube and struck the rectangular steel plate. PIV setup along with the pressure and acoustic emissions sensors were used to characterize the propagation and impingement of the shock wave on the plate as well as the behavior of the reflected shock wave and the vortex ring. In case of a vertical rectangular steel sheet stationed in front of the exit of the shock tube, the central part of the shock wave was found to interact with the central part of the vortex structure and the external part of the shock wave came into contact with the outer part of the vortex structure. Whereas in case of inclined sheet, the shockwave reflected from the sheet, came into collision with the rebound shockwave as well as with the lower portion of the vortex ring largely. However, with the further variation in the angle of inclination (i.e. 30o and larger) fromvertical axis, no further appreciable change was observed in the flow profile except the vortex ring interacted earlier with the rebounded shockwave in the lower region within the neighborhood of the plate than the interaction of the vortex ring with the rebounded shock wave in the upper region of the inclined plate. The pressure and acoustic emission measurements were symmetric with the vertical plate, however, the pressure data was asymmetric when the plate was inclined from vertical. When the angle of inclination changes to 30 degrees from the vertical, the flow becomes more asymmetric as the shockwave and the consequent vortices impinged on the surface of the plate much earlier than the 15 degrees’ inclination case.

Fire Behaviour of Rectangular Steel Tubed-Reinforced-Concrete Columns with End Restraints

Fire Behaviour of Rectangular Steel Tubed-Reinforced-Concrete Columns with End Restraints

Advancements in light-gauge steel rectangular CFST columns: A comprehensive experimental study

This research examines the structural performance of rectangular Concrete-Filled Steel Tube (CFST) columns produced from light-gauge steel tubes. The study aimed at improving their strength, stiffness, and ductility via a combination of external confinement, internal stiffeners, and hybrid fiber-reinforced concrete (HFRC) infill. An axial compression test was carried out on a total of 18 samples, comprising of unconfined hollow steel tubes, bracing-confined tubes, ring-confined tubes, unconfined CFST, bracing-confined CFST, and ring-confined CFST columns. To restrict lateral expansion, external restraints including bracing and ring-type steel rods, were spot-welded to the outer steel tube. To optimize the column’s load carrying capacity and mitigate buckling effects, the spacing of the confinements were systematically designed. HFRC infill and alterations in the inner profile with and without vertical strips and studs, were also taken into consideration. The experimental results plus the failu re modes, axial load-deflections and load-deflection curves were analyzed to understand the behavior of the CFST columns. Performance indicators such as strength and stiffness ratios, and confinement effect ratio, were assessed for the various sample types. This research accentuates the efficiency of external confinement techniques in improving strength and ductility. Existing design codes were adopted for the theoretical estimations of the axial compression capacity, highlighting variations in predictions. This study significantly contributed beneficial understandings of the structural performance of rectangular CFST columns, stressing the importance of both internal and external confinements and HFRC infill.

Effect of web holes on web crippling capacity of rectangular hollow steel sections under two flange loadings

This paper presents experimental and numerical investigations on web crippling behavior of hot rolled rectangular hollow section (RHS) with web holes. A total of 20 rectangular hollow sections, subjected to interior-two-flange (ITF) and end-two-flange (ETF) loading conditions undergoing web crippling, were experimentally tested. The experimental program was designed to obtain web crippling of specimen having slenderness (h/t) value of 21.32, by varying size and offset distance of web holes under two flange loading conditions. Finite element models of experimentally tested beams were developed, and results of finite element analysis showed good agreement with experimental results. A parametric study was then conducted using finite element analysis on different cross section sizes, to demonstrate the effect of size and position of web holes on web crippling capacity of rectangular hollow sections. It was demonstrated that ratio of diameter of web hole to the depth of flat portion of web (a/h) and ratio of offset distance of web hole to the flat portion of web (x/h) are the primary parameters affecting the web crippling strength. Design recommendations in the form of reduction factors for both loading conditions are proposed, that are conservative to both experimental and finite element results. To assess the reliability level of design recommendations, reliability analyses were undertaken.

Effect of Cross-Section Stiffness on Strength of Rectangular Steel

Concrete-filled steel tubes (CFSTs) have better application in the application of beams and columns. This application form has obvious advantages, mainly because they are not restricted by the forming process, and the filled concrete does not need long-term maintenance. However, the design and analysis of steel-concrete beam-columns is a complex task involving many factors. In the design of CFSTs, it is essential to understand the influence of these factors on the behavior of steel-concrete members. In particular, the cross-sectional shape of the member has a significant impact on its bearing capacity, stiffness, and buckling behavior. However, there is relatively little research on the influence of member slenderness on the strength of CFSTs. Therefore, this study conducted an in-depth analysis of the stability of the member, and explored in detail the influence of the member slenderness ratio on the section properties and the overall bending strength of the beam. This study provides a basis for the application of CFSTs in beam-column design and analysis. In the bending strength analysis, the member slenderness ratio has an important influence. Smaller slenderness ratios have better strength performance, but the attenuation is also relatively significant. The larger the slenderness ratio, the slower and more stable the strength change becomes. In terms of section properties, when the slender section is reached, the influence of effective section reduction will be greater, and the strength reduction may exceed the engineering allowable error range. Therefore, special attention should be paid when using slender sections.

The Seismic Behavior of Rectangular Concrete-Encased Steel Bridge Piers: A Review

This paper proposes a review of the previous research work and the representative publications regarding the seismic behavior of the concrete-encased steel (CES) columns. Concrete-encased steel sections are composed of steel sections encased in reinforced concrete members. The research work recently showed increased attention to this type of column due to its advantages compared to conventional reinforced concrete columns. Firstly, the analytical studies of the behavior of the CES columns under axial loads, including comparative studies between different research works, are presented. Then, the behavior of the CES columns under combined axial and flexural loads is also highlighted. An overview of the analytical confinement material models is addressed. In addition, the discussion and summary of the seismic behavior of the CES columns and the important parameters affecting the seismic behavior of these types of columns are included. Although important progress has been made by the previous studies in the CES columns under the axial load and the combination of axial and seismic loads, they fundamentally focused on the building columns, and little attention was paid to the impact of lateral reinforcement and their configuration in bridge piers. Due to the lack of studies on the parameters affecting the seismic behavior of the bridges, more studies should still be made to better understand the behavior of the CES bridge piers. This paper provides a reference for the research and engineering practice of concrete-encased steel bridge piers. It also concludes with suggestions for future studies to integrate the seismic requirement of the CES bridge piers in Canada.

Analysis of damage characteristics of the rectangular steel container under near-earth explosion loading

In this study, the dynamic response of a semi-buried steel vessel under a near-surface explosion shock load was investigated through full-scale model tests. A three-dimensional precise numerical simulation model of the semi-buried steel vessel structure was established, and the dynamic response and damage consequences under different load conditions were analyzed. The influence of the thickness of corrugated steel on the dynamic damage and antiknock properties of the structure was studied. The results show that the weak part of the rectangular steel vessel structure is mainly located at the connection between the blast-facing panel and the beam column under near-surface explosion conditions. The peak stress and displacement of the blasting surface decrease with the increase in the horizontal angle of the incident wave, whilst/while increase with the height of the explosion. Under the same explosive yield, the main failure mode of the structure is the tearing of the plate and beam under plastic deformation. Increasing the thickness of the corrugated steel can significantly restrain the plastic deformation and acceleration of the plate. When the thickness is increased from 2 mm to 6 mm, the antiknock performance is significantly improved. However, when the thickness is increased from 6 mm to 8 mm, the improvement in antiknock performance slows down. Increasing the height of the enclosing soil can also effectively improve the explosion-proof performance of the structure, with full burial providing the best effect. The research results provide a theoretical basis for the application of rectangular steel vessel structures in the field of protection engineering.

Behaviour of eccentrically loaded concrete-filled rectangular ferritic stainless steel tubular slender columns: Numerical modelling and design

Ferritic stainless steel achieves a lower and steady price level due to low nickel content compared to duplex and austenitic stainless steels. Accordingly, the combination of ferritic stainless steel tube and concrete will have better application prospects in corrosive marine environments. However, the structural application of concrete-filled ferritic stainless steel tube (CFFSST) members is still limited due to the absence of performance data and design guidelines. Accordingly, this paper aims to comprehensively investigate the behaviour of eccentrically loaded concrete-filled rectangular ferritic stainless steel tubular (CFRFSST) slender columns using the nonlinear finite element (FE) method, and develop a suitable design method. Two different material models were introduced to simulate corner and flat regions of rectangular ferritic stainless steel tube. Good consistency was found between the simulation and experimental results against the failure mode, ultimate load and moment, and axial load versus mid-height deflection curves for eccentrically loaded CFRFSST slender columns. This is followed by the mechanism analysis and parameter study of the studied CFRFSST columns, which revealed that the longitudinal stress and Mises stress show significant changes perpendicular to the loading line direction, while there is almost no change along the loading line direction. In addition, the initial stiffness and ultimate load increased by increasing the cross-sectional aspect ratio, yield stress and concrete strength, while they decreased as the eccentricity ratio, slenderness ratio and width-to-thickness ratio increased. The outputs of the FE analysis and existing experimental results were used to examine the applicability of current design codes for designing the studied CFRFSST columns. The results demonstrated an unexpected deviation generated in the design predictions. At the end, a new design method for eccentrically loaded CFRFSST slender columns was proposed which achieved better predictive consistency.

Hybrid particle swarm optimization and group method of data handling for the prediction of ultimate strength of concrete-filled steel tube columns

This study presents a hybrid model coupling particle swarm optimization (PSO) with group method of data handling (GMDH) for predicting the ultimate strength of rectangular concrete-filled steel tube (RCFST) columns. A large database of 490 data samples collected from the existing literature was used to construct the model. Compared with the optimal model among the nine existing models, the coefficient of variation (COV), mean absolute percentage error (MAPE) and root relative squared error (RRSE) values of all datasets of the PSO-GMDH model were decreased by 58.38 %, 69.22 % and 64.27 %, respectively; while the coefficient of determination (R2) and a20-index values were increased by 34.32 % and 8.65 %, respectively. The results show that the predicted results of PSO-GMDH model are in good agreement with the experimental results and can accurately predict the ultimate strength of rectangular RCFST columns. In addition, a graphical user interface (GUI) has been developed to facilitate the application of the PSO-GMDH model.

Behaviour of rectangular concrete-filled steel tube beams under monotonic and cyclic loadings

Concrete filled steel tube (CFST) has been extensively explored for columns but limitedly explored for beams. This current study investigates the behaviour of rectangular CFST beams under monotonic and cyclic loadings. Experiments were conducted for 12 CFST beams with depth-to-thickness (D/t) ratios of 66.7–111.1, followed by theoretical analyses. The experimental results indicated that tensile yielding and compressive local buckling of steel tubes governed the plastic behaviour of the tested CFST beams. The buckling significantly degraded the strength of CFST beams. When the D/t ratio decreased from 111.1 to 66.7, the stiffness, yield load, and ultimate load increased by 33.2%, 49.4%, and 40.0%, respectively, but the ultimate deflection was reduced by ∼19.5%. The effect of cyclic loading induced a degradation of stiffness of 0.85–2.85%/cycle, depending on the increment of the peak cycle deflection. The buckling negatively affected the ultimate state, significantly reducing the ductility. Investigations into solutions to delay the buckling of steel tubes should be encouraged. Three approaches based on concepts of composite sections, fully plastic sections of steel tubes, and the proposed decoupling were applied to compute the ultimate strengths of the tested beams. The calculation results indicated that the model of fully plastic sections of steel tubes exhibited the best agreement with the test results. The fully plastic and proposed decoupling models provided reasonable results, while the composite model slightly overestimated the ultimate load of CFST beams. The results provide some technical information for structural engineers in designing rectangular CFST beams.

Broadening Bandwidth in a Semi-Active Vibration Absorption System Utilizing Stacked Polyvinyl Chloride Gel Actuators.

Plasticized polyvinyl chloride (PVC) gel is a new soft and smart material, whose potential in electroactive variable stiffness can be used for vibration control in soft robotic systems. In this paper, a new semi-active vibration absorber is developed by stacking PVC gel actuator units. The absorption bandwidth of a single PVC gel absorber covers the range of three natural frequencies (76.5 Hz, 95 Hz, 124 Hz) of a rectangular steel plate in vibration attenuation. The maximum reduction percentage in acceleration amplitude is 63%. With stacked PVC gel actuator units, the absorption bandwidth can be shifted and obviously broadened.

Analysis of Rectangular Plate with Opening by Finite Difference Method

Steel plates are commonly used to support lateral or vertical loads. Before the design of such a plate, analysis is performed to check the stability of plate for the proposed load. There are several methods for this analysis. In this research, a finite difference method (FDM) is proposed to analyze a rectangular steel plate. The plate is considered to be subjected to an arbitrary transverse uniformly distributed loading and is considered to be clamped at the two opposite edges and free at the other two edges. At first the plate is analyzed considering it to be completely solid and then it was re-analyzed considering a rectangular opening at its centre. The ordinary finite difference method is used to solve the governing differential equation of the plate deflection. The proposed method can be easily programmed to readily apply on a plate problem. The work covers the determination of displacement components at different points of the plate and checking the result by software (STAAD.Pro) analysis.

Resilience-based seismic design and cyclic behavior of assembled joints between self-compacting concrete-filled rectangular steel tube frame columns and H-shaped steel beams

The overall stability of prefabricated steel structures depends significantly on the strong seismic resilience exhibited by the connections between beams and columns. This paper introduces a novel beam–column connection approach, referred to as the welded upper and lower flanges and two diagonal web plates (WULF-TDWP). Unlike conventional methods, this approach replaces bolted connections with butt-welded joints between steel beams and employs short cantilever beams to achieve plastic hinge displacement. The steel-column cross-section was designed with a larger aspect ratio to better absorb and distribute energy. Six full-scale specimens were subjected to cyclic loading tests to investigate the seismic performance of the WULF-TDWP system. The main test parameters included the axial load ratio, welding configuration in the node region, and presence of reinforcement plates. The specimens exhibited two distinct failure modes: plate buckling deformation and beam–column end weld tearing. The experimental results included the hysteresis curves, skeleton curves, ductility coefficients, stiffness degradation curves, and strength degradation curves of the specimens. The experimental findings highlighted the favorable hysteresis performance, load-carrying capacity, and deformation capacity of all the nodes. Additionally, the plastic hinges were observed to shift, thereby delaying the premature failure of the node region. Notably, the omission of welding between the cantilever short beam flange and steel column significantly reduced the initial stiffness of the node. Through finite element analysis, the seismic performance of the beam-column joints with upper and lower flange welded connections and cantilever short beams was elucidated. The reliability of the finite element model for assessing the seismic performance of the nodes was confirmed through validation using experimental findings. Furthermore, this paper categorizes the nodes and introduces a simplified calculation model based on the moment–rotation method.

Axial compressive behavior of T-shaped welded multi-partition composite members

T-shaped welded multi-partition composite members, which are made of several rectangular concrete-filled steel tubes, are proposed to speed up the fabrication procedure. Seven half-scale T-shaped specimens were tested by considering the section height-to-width ratio and slenderness ratio. In the test, a slight torsion angle was measured when the instability failure along the asymmetric axis occurred, indicating the specimens had good torsion resistance. When the relative slenderness ratio of the specimen was larger than 0.44, the specimens failed due to the instability along the asymmetric axis. Parametric numerical analysis is conducted by considering the slenderness ratio, cross-section dimension, steel ratio, and material strength. The results show that the strength of concrete negatively impacts the ductility of the specimens, leading to a decrease of 43%, while the strength of the material positively influences the stability of the specimens. The formulas from different traditional codes are verified by the parametric numerical analysis results, indicating most codes can conservatively predict the sectional bearing capacity, but overestimate the stability coefficient of the specimens by neglecting the reduction effect of the excessive height-to-depth ratio. Recommendations are provided for calculating the stability coefficient under axial compression applicable to T-shaped welded multi-partition composite members.

Structural Behaviour of Concrete-Filled Steel Tubular Stub Columns-Comparative Study

This paper presented details of a research to investigate the structural behaviour of Concrete-Filled Steel Tubular (CFST) stub columns through axial load strength. Three series distinguished were chosen depending of the steel X-sectional area of the tubes for each series of different shape are compared: circular, rectangular and square steel sections considering the parameters of the different types of concrete infill, i.e. normal strength concrete (NSC) or high strength concrete (HSC). It is found from these comparisons that all the codes (Eurocode part 4 (EC4), AISC-360-10 and BS5400-5) predicted conservative column strengths compared to the test results and published theoretical method with an average ratio (0.75 for EC4,0.656 for AISC-360-10 and 0.6 for BS5400-5). the main advantages of the ABAQUS software program are it gave closer predictions to the published experimental study results with an average ratio 0.96, simplicity and the savings in test time. circular CFST stub columns strength was higher than square CFST stub columns when compare rectangular and square in same series the column have higher area of concrete have higher strength.