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Based on the elaborate 3D solid finite element (FE) model established by ABAQUS software, a pseudo-static analysis was conducted on a special-shaped concrete-filled steel tubular column composite frame structure. The FE model considers the confinement effect of both the steel tubes and the tensile bars exerting on the core concrete. The results of the numerical analysis concerning failure modes, load-displacement hysteretic curves, load-displacement skeleton curves and stiffness degradation-displacement curves demonstrate a strong correlation with the existing quasi-static test data. Furthermore, an in-depth analysis was conducted on the impact of the axial compression ratio of column on the plastic energy dissipation distribution mechanism. With an axial compression ratio of the column ranging from 0.1 to 0.55, the composite frame structure primarily relies on the energy dissipation of beams, while the columns serve as supplementary support, thereby exemplifying the principle of "strong column-weak beam." As the axial compression ratio rises to the range of 0.6–0.8, the composite frame structure transitions a "strong beam-weak column" structural system. Combined with the longitudinal compressive strain of the steel tube at the bottom of the column, a quantitative evaluation method for seismic damage is proposed, grounded in indexes of "stiffness damage" and "energy damage." Then, the threshold values of energy damage and stiffness damage are determined across four distinct levels: "elastic stage in small earthquake," "elasto-plastic stage in medium earthquake," "plastic stage in heavy earthquake" and "failure stage." The proposed method effectively evaluate the damage severity of special-shaped CFT column composite frame structure subjected to seismic events. Highlights: The FE model in this paper has high accuracy, which can reasonably simulate the pseudo-static behavior of special-shaped CFT column composite frame structure. A seismic energy dissipation analysis method of special-shaped CFT column composite frame structure is proposed, and the influence of axial compression ratio on the energy dissipation distribution mechanism of beams and columns is further analyzed. This paper propose two indexes, namely "stiffness damage" and "energy damage," which can reflect the internal properties of composite frame structure and can accurately evaluate the damage degree of composite frame structures. [ABSTRACT FROM AUTHOR]

Hybrid fiber-reinforced polymer (FRP)–concrete–steel double-skin tubular columns (DSTCs), which consist of an inner steel and an outer FRP tube, with the space between the two tubes filled with concrete, are a promising form of hybrid columns for structural and durability performance. Extensive research has been conducted on the short-term mechanical behavior of hybrid DSTCs. However, in practice, most columns are subjected to long-term sustained loading; therefore, the creep behavior of these novel columns should be deeply understood before they are widely applied. No research has been conducted on DSTCs under long-term sustained loading, to the best of the authors' knowledge. This paper reports the first experimental program on the creep behavior of hybrid DSTCs under sustained loading to explore the effects of important parameters, such as the concrete, FRP and steel tube thickness, sustained compressive load ratio, and shear studs, on the creep behavior of the hybrid DSTCs. After the sustained loading, axial compression tests on the hybrid DSTCs were conducted to evaluate the effect of sustained loading on the compressive behavior (e.g., load-carrying capacity) of these columns. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tube (CFST) columns are widely employed in high-rise buildings, long-span bridges, and seismic-resistant structures due to their superior load-bearing capacity, structural efficiency, and resilience under extreme loading conditions. This study uses symbolic regression with structural design code provisions to predict the eccentric strength of concrete filled-steel tubular columns with circular shape (CCFST) and rectangular shape (RCFST). Previous studies have used two distinct approaches for estimating eccentric strength: explainable models based on theoretical derivations and black-box models derived from machine learning (ML) methods. This study proposes a hybrid model derived from the design code standards, with performance enhanced by the symbolic regression technique. This model is based on a comprehensive experimental database of 464 tests for CCFST columns and 313 tests for RCFST columns under eccentric loading from various research papers. The developed code-based symbolic regression (C-SR) displays both robust and interpretable, demonstrating high prediction accuracy with mean values of the prediction-to-actual ratios of 1.006 and 0.997 and coefficient of variation (CoV) values of 0.117 and 0.098 for CCFSTs and RCFSTs, respectively, while providing explainable mathematical expressions that align with the mechanical principles of code provisions. The developed C-SR model is benchmarked against EC4 and AISC360 standards and evaluated against the various ML techniques, demonstrating acceptable performance. The results highlight the C-SR model's effectiveness in providing reliable predictions and valuable insights for practical engineering applications. [ABSTRACT FROM AUTHOR]

During seismic events, reinforced concrete (RC) columns play a crucial role in maintaining buildings' structural integrity. This motivated engineers and practitioners to search for key parameters that influence the load-carrying capacity and failure mechanisms of such columns. However, the complexity and nonlinearity of seismic effects along with the intricate nature of RC columns as a composite system challenge the capabilities of analytical and empirical approaches to accurately capture the response of RC columns. Subsequently, the present study utilizes Machine Learning (ML) techniques to identify the failure modes and predict the corresponding capacities of RC columns based on both their geometrical and material properties. Decision trees and different ensemble methods were employed to predict both the columns' failure mode and ultimate capacity. A multivariate dataset consisting of 486 cyclically loaded rectangular and circular columns was used to develop and validate the models. In addition, different embedded variable selection techniques were employed to evaluate the significance of input parameters in predicting the performance of columns. Moreover, partial dependence plots and accumulated local effects were employed to uncover the interrelationships between the input features and the modelled outputs. The developed models yielded an average accuracy of 90% and 95% for predicting the failure mode and ultimate capacity of RC columns, respectively. Given such high accuracy, it can be inferred that, ML techniques have the potential to provide efficient and reliable prediction tools to support seismic design and assessment decisions - mitigating seismic risks and empowering resilience planning in the face of extreme events. [ABSTRACT FROM AUTHOR]

AbstractIn web-tapered columns, the taper ratio (or nonuniformity index) is a key parameter that must be carefully evaluated as it significantly affects stability. The aim of this study is to investigate the effect of taper ratio on the critical buckling load, flexural displacement, post-buckling behavior, and the bifurcation point when columns are subjected to axial compressive loads and experience in-plane flexural buckling, since in the design of many structures, out-of-plane buckling is restricted, and lateral restraints effectively control buckling about the weak axis. For this reason, the analysis in this study is conducted along the strong axis, and the stability of ideal and imperfect web-tapered I-shaped steel columns with various taper ratios and different support conditions is studied. The results are obtained based on linear and nonlinear analysis using the finite element method (FEM). For better understanding, the results of linear and nonlinear analysis considering the taper ratio are compared in various diagrams, providing valuable insights that should be considered in the design of steel columns with web-tapered I-sections. [ABSTRACT FROM AUTHOR]

The axial compression capacity of steel reinforced concrete (SRC) stub columns with unsymmetrical steel sections (USSs) was investigated in this study. Axial compression tests were conducted on four SRC stub columns with USSs, and internal force analyses were conducted on a total of 22 finite-element models. The failure modes, load–displacement curves and internal forces were used to analyse the mechanical behaviour and bearing capacity of the columns under axial compression. Furthermore, the variables that influence the axial compression capacity comprising different width-to-thickness ratios of the steel flange, area ratio of the steel section to the confined concrete, web eccentricities and steel eccentricities were investigated in a parametric analysis. The results showed that, compared to SRC stub columns with symmetrical steel sections (SSSs), the columns with USSs showed slightly flexural failure. Steel eccentricity was the main factor that affected the axial compression capacity of SRC stub columns with USSs. An equation was proposed for calculating axial compression capacity of an SRC stub column with a USS considering steel eccentricity. Results calculated by the proposed formula showed better agreement with the experimental value than that calculated by the codes, and the formula is also applicable to SRC stub columns with SSSs. [ABSTRACT FROM AUTHOR]

Roof truss systems and wall panels are two examples of popular structural components made by cold-formed steel (CFS) which is classified as a steel-based building material available in a wide range of shapes, and thicknesses. The use of CFS is increasing due to its many desirable properties, including a high strength-to-weight ratio, low weight, resistance to corrosion, and fast installation. In contrast, the thin-surfaced and opened section of CFS buckles easily when utilised as a beam or column. When the load is applied directly, the CFS section fails in modes such as web crippling, torsion, and buckling. As a result, the new I-section with top and bottom flange elements was produced by using CFS channel section, and timber board from the type of oriented strand board (OSB) as a web element. The study aimed to determine the initial structural characteristics of the built-up I-section CFS with OSB short column. A single or double web element made by yellow and dark brown OSB was used to construct the I-section for determining the initial structural characteristics. The Isection with a double web of yellow OSB showed the highest value of ultimate load and compressive strength as compared to other specimens in the range of 8.00% to 14.00%. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Metallurgical industrial buildings, particularly those over 10 years old, frequently experience increased vibrations in their latticed columns due to prolonged dynamic loads from cranes, affecting both structural safety and usability. To enhance the strength and stiffness of these structures in a cost-effective way, a novel composite latticed column made from concrete-filled steel tubes and corrugated steel plates is proposed. An analytical study on its axial compression behavior has also been conducted. The analytical parameters included the yield strength of steel tube and compressive strength of concrete, the waveform of corrugated steel plate, as well as the thickness, yield strength, and configuration of steel lacing tubes. Results show that compared to specimens with C30 concrete, the bearing capacity and initial axial stiffness of specimens with C50 concrete can increase by 35% and 33%, respectively. Compared with the steel specimen with yield strength of 235 MPa, the peak bearing capacity of the steel specimen with yield strength of 400 MPa can be increased by 28%. Additionally, increasing the wave height reduces the concrete cross section, resulting in a decrease in axial stiffness and ductility. Compared to specimens with horizontal lacing tubes, those with diagonal lacing tubes exhibit increases in ductility and axial stiffness of 33% and 12%, respectively. Therefore, diagonal lacing tubes should be considered for the optimal axial compression behavior of latticed columns. Furthermore, a model for predicting the axial compression bearing capacity of latticed columns with CFST tubes and corrugated steel plates was proposed. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tube (CFT) columns are widely used as structural systems because of their high load-bearing capacity and material efficiency. However, under fire conditions, elevated temperatures degrade the mechanical properties of both steel and concrete. When combined with initial geometric imperfections, these factors significantly affect the load distribution and the fire resistance of the structure. Understanding how material properties and geometric factors change in CFT columns at elevated temperatures is essential for ensuring safe and efficient design. This study used the ASTM E119-88 fire curve to establish the relationship between the surface temperature of the structure and the fire resistance duration of the CFT column. Heat transfer and mechanical analyses of the structure were conducted using ABAQUS 2024 software. A comparison of simulation and experimental data showed that the numerical model was highly accurate. The study also addressed the effects of initial geometric imperfections, considering amplification factors of L/1000 and L/500, and compared the simulation results with the experimental data. The results demonstrated that initial geometric imperfections significantly influenced the fire resistance of the columns. Additionally, this study examined the material properties under high-temperature conditions as specified in the AISC 360-22 standard. The study compared the simulation results with the Eurocode standards and experimental data. The findings suggested that utilizing the material properties specified in the AISC 360-22 standard resulted in more conservative predictions of fire resistance for CFT columns, compared to the Eurocode standards. Furthermore, Appendix 4 of the AISC 360-22 standard was used to calculate the fire resistance rating of the CFT column. These calculations were compared with the simulation and experimental results to evaluate the reliability of using ABAQUS 2024 simulation software. [ABSTRACT FROM AUTHOR]

The frame column of Xiong'an Hub Station supporting the bearing rail layer adopts section steel concrete column. Due to the need of seismic fortification requirements, the section of the steel concrete column is huge. In order to reduce excessive buried footing depth resulted from the traditional embedded steel and concrete column base design and the construction risk hereafter, a new type of semi-buried column base scheme is proposed with the footing steel embedded in the bearing platform about 1.35 times the height of the section of steel, the footing moment reliably transferred to the foundation by using the cross-shaped arrangement of the boot beams, anchor bolts, U-shaped reinforcement, prestressing tendons combination of the structural method so as to reduce the thickness of the foundation bearing platform. In order to verify the reliability of the design scheme, the column base scheme is simplified, and a column base joint model with a scaled-down ratio of 1:6 is designed and fabricated, and a static test is carried out to obtain the mechanical response and damage of the column base joint under complex loading. Test results exhibite that only cracks appear in the tensile zone of the column base and the steel members of both specimens do not yield under one times of design load, and cracks appear in the compression zone of the column base and bearing platform of both specimens under two times of design load, but the reinforcement bars, the steel boot girders and the steel bones do not yield, which proves that the column base joint has sufficient safety reserve. In addition, the application of prestressing increases the ultimate bearing capacity of the column base joint by 32.9%, and improves the deformation capacity of the column base joint, in which the maximum vertical displacement of the beam end is increased by 92.1%, and the maximum horizontal displacement of the column end is increased by 98.0%; moreover, the application of prestressing could improve the punching shear capacity, and reduce the strain level and the width of the crack at the junction of the bearing platform and the lower level. The structural test results have been applied to the design of Xiong'an Hub Station, and the proposed column base construction form has high safety reserve and good implementability, which can be popularized and applied in the design of similar projects to provide solutions for similar engineering problems. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Architecture & Civil Engineering is the property of Chang'an Daxue Zazhishe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, a new connection between the H‐beam and rectangular concrete‐filled hot‐rolled‐steel tubular column (CFHRSTC) was proposed to prevent the steel beam‐column joint protruded from the inside wall in residential buildings. The quasi‐static test and finite element analysis were conducted on four new joints to study the influence of the haunch stiffener configuration, internal steel plate thickness, and axial force on the failure mode, load‐carrying capacity, ductility, energy dissipating capacity, and stiffness degradation of the joint. The results revealed that the hysteretic curve of every joint was full. The damage to the joint was concentrated in the H‐beam, and the CFHRSTC remained elastic. The joint configuration could realize a weak beam‐strong column and joint core connection. Using the haunch stiffener on two sides of the H‐beam flange could effectively optimize load transfer at the end of the H‐beam and joint core. As the axial force increased, the ultimate load‐carrying capacity and ductility gradually decreased. Reducing the thickness of the internal steel plate did not significantly influence the seismic performance of the joint. Compared with the use of cover plate joints, the use of haunch stiffeners can effectively enhance the seismic performance of joints. [ABSTRACT FROM AUTHOR]

Based on the ribbed rebar with direct rolling thread and hot‐forged double‐lock nut mechanical sleeve connection technology, a construction method for prefabricated reinforcement cage‐cast‐in‐situ concrete (PRC‐CISC) column using this connection is proposed. This method contributes to improving the construction efficiency and engineering quality of reinforced concrete columns. Four PRC‐CISC columns and four control specimens were designed with rebar strength, rebar ratio, and rebar connection method as analysis parameters. A comparative study was conducted on their failure modes, axial compression performance, and rebar connector (coupler) working mechanisms. The results show that compared to the control specimens, the crack morphology of PRC‐CISC columns has no significant difference. However, the apparent yielding position of the reinforcement cage may occur on the cross‐sections where the rebar is located on both sides of the sleeve. The partial carrying capacity of the specimens may increase or decrease (≤4.08%), and the maximum deviation of the displacement ductility coefficient is 0.14, indicating that its strength and deformation differences are relatively small. Furthermore, the study reveals the random migration behavior of the control section of PRC‐CISC columns. When the specimens fail, the strain of the sleeve is significantly smaller than the rebar strain in the control specimens, while the concrete strain shows no significant difference. This is because the increase in the effective area of the sleeve shares the vertical load it bears. Finally, based on the test results, sleeve constitutive relationship, and random migration behavior of the control section, the compressive load capacity range of the positive section of PRC‐CISC columns is proposed. This method can effectively estimate their actual carrying capacity and is consistent with the force characteristics. [ABSTRACT FROM AUTHOR]

The ultimate load-carrying capacity of concrete-filled steel tubular (CFST) columns exposed to monotonic loadings can be greatly increased by strengthening those columns, and the occurrence of the steel tube's outward buckling can be postponed. The current research aims to study the possibility of improving the structural characteristics of CFST columns exposed to cyclic loadings in terms of lateral load capacity and absorbed energy by strengthening them with different patterns of fiber-reinforced polymer (FRP) sheets. The ABAQUS software was used to create a three-dimensional (3D) non-linear finite element model (FEM) to simulate the behavior of FRP-strengthened CFST columns exposed to monotonic and cyclic loadings. After ascertaining the accuracy of the proposed model's results in successfully predicting failure patterns and lateral loads compared to the experimental results of tested specimens available in the literature, the model was used to create a parametric study. The parametric study focused on the impacts of the thickness, location, and length of the strengthening sheets on the failure pattern, lateral load-carrying capacity, stiffness, cumulative energy, absorbed energy, and viscous damping factor of the CFST columns exposed to cyclic loadings. The results revealed that the un-strengthened specimen displayed a maximum lateral load of 185 kN and a viscous damping factor of 45.2% at a lateral drift of 5.7%. On the other hand, strengthening the CFST column using five layers of FRP sheets exhibited the highest lateral load of all investigated columns (50% more than the un-strengthened specimen). Additionally, at a lateral drift of 5.7%, the decrease in viscous damping factor of CFST specimens due to strengthening using 1, 2, 3, 4, and 5 layers of FRP sheets with respect to the control specimen was 7.9%, 14.9%, 20.8%, 27.7%, and 30.3%, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a modified finite element analysis (FEA) model for predicting the axial compression strength of large-diameter concrete-filled steel tubular (CFST) stub columns, addressing the gap in research that has often focused on smaller diameters. The size effect, which significantly impacts the structural performance of large-diameter CFST columns, is a key focus of this study. The goal is to validate the accuracy and reliability of the modified FEA model by comparing its predictions with experimental data from the literature, specifically examining ultimate axial load capacity, failure modes, and deformed shapes. In addition to validating the model, this study includes a comprehensive parametric analysis that explores how critical geometric parameters such as the diameter-to-thickness (D/t) ratio and length-to-diameter (L/D) ratio affect the axial compressive behavior of CFST stub columns. By systematically varying these parameters, the research provides valuable insights into the load-bearing capacity, deformation characteristics, and failure mechanisms of CFST columns. Furthermore, the material properties of the steel tube—particularly its yield strength—and the compressive strength of the concrete core are investigated to optimize the design and safety performance of these columns. The results indicate that the FEA model shows excellent agreement with experimental results, accurately predicting the axial load-strain response. It was observed that as the diameter of the steel tube increases, the peak stress, peak strain, strength index, and ductility index tend to decrease, underscoring the size effect. Conversely, an increase in the yield strength and thickness of the steel tube enhances the ultimate strength of the CFST columns. These findings demonstrate the reliability of the modified FEA model in predicting the behavior of large-diameter CFST columns, offering a useful tool for optimizing designs and improving safety margins in structural applications. [ABSTRACT FROM AUTHOR]

This study comprehensively investigates the self‐compacting alkali‐activated slag concrete‐filled cold‐formed steel tubes (SACFST) stub columns under axial compression. The innovative combination of alkali‐activated slag concrete (AASC) with concrete‐filled steel tubes (CFST) enhances both sustainability and structural performance. AASC, known for its eco‐friendly benefits compared to conventional concrete, was developed using industrial wastes, contributing to green construction practices. Based on Taguchi's L‐9 orthogonal array, nine mixes of self‐compacting alkali‐activated slag concrete (SASC) were developed, achieving impressive flowability exceeding 700 mm and compressive strengths ranging from 48 to 69 MPa. Additionally, split‐tensile strengths between 3.8 and 5.7 MPa, flexural strengths from 6.3 to 8.2 MPa, and a modulus of elasticity between 27.6 and 32.9 GPa were observed. Nine circular CFSTs containing SASC mixes were tested under axial compression, and a finite element model was developed to simulate their results. The experimental results were compared with standards from ACI 318, AIJ‐97, AISC‐360, AS 5100, and EC‐4, to evaluate the accuracy of axial capacity predictions. Among these standards, EC‐4 and AS 5100 provided the closest estimates, with mean PTest/PEC4 and PTest/P5100 ratios of 1.03 and 1.04, respectively, indicating a high level of accuracy. These findings highlight the potential of SACFST in advancing sustainable and resilient construction practices, laying the groundwork for future applications in structural engineering. [ABSTRACT FROM AUTHOR]

Steel tube–reinforced concrete (STRC) columns are composite members consisting of an inner concrete-filled steel tube (ICFST) component and an outer reinforced concrete (ORC) component. These columns are commonly used in the bottom columns of high-rise buildings and bridge piers to withstand significant axial loads. However, the stress state of the components in a STRC composite column differs from that of a single confinement component. As a result, the existing lateral strain model and concrete constitutive model cannot be directly applied to describe the stress–strain development of each component. To address this issue, this study combines the existing confined concrete models with the stress balance condition and strain development characteristics of the cross section of a STRC composite column. Theoretical models are proposed to simulate the development of lateral strain and confining stress in both the ICFST component and ORC component. Additionally, the biaxial stress state of the steel tube is considered based on the generalized Hooke law and Prandtl-Reuss theory in the theoretical model. Consequently, an incremental iterative calculation model for the whole axial load–strain curve is proposed. The effectiveness of the proposed models is verified by comparing the calculation results with the experimental results. [ABSTRACT FROM AUTHOR]

In order to meet the bearing requirements of prefabricated composite slab‑column joints, two types of connection joints between steel‑concrete‑steel sandwich slab and structural column are proposed. Using ABAQUS finite element software, the numerical calculation model of composite slab column joint is established, and the bearing capacity of precast joint under punching load and the influence of main design parameters on its mechanical and deformation properties are analyzed. The results show that, compared with the cast‑in‑place joints under the same condition, the prefabricated connection joints can significantly increase the punching shear capacity while ensuring good ductility. These indicate that the connection components can make a positive contribution to the punching shear resistance of the joints. In addition, it is recommended to use a 16 through bolts radial arrangement and choose a square or cross shaped external diaphragm in the external diaphragm‑thru bolt connection. The diaphragm’s strength grade is consistent with the composite slab, which is taken as Q345. For the cantilever composite slab‑circumferential flange connection, it is suggested that the flange thickness should be controlled at about 20 mm, so as to make the joint own a higher cost performance. [ABSTRACT FROM AUTHOR]

This paper experimentally investigates the behavior of innovative sustainable Low-Cost Bamboo Composite (LCBC) structural columns under compressive loading. The LCBC columns are manufactured from bamboo culms in combination with bio-based resins to form composite structural columns. Different LCBC cross-sectional configurations are investigated in this study, including the Russian doll (RD), Big Russian doll (BRD), Hawser (HAW), and Scrimber (SCR). Two bio-based resins, including one bio-epoxies and one furan-based resin, in addition to a soft bio-based filler and a synthetic epoxy resin, are applied. The bamboo species used as the cast-in-place giant bamboo for all configurations include Moso, Guadua, and Tali. Slender LCBC columns showed maximum stress equal to 60 MPa at failure. The study found that the samples with bio-epoxy resin (BE2) exhibited enhanced material stiffness when compared to synthetic epoxy (EPX) and furan-based resin (PF1), while PF1 specimens demonstrated increased ductility. Among the specimens with Moso bamboo and BE2 resin, those with SCR and HAW configurations achieved the highest compressive strengths. [ABSTRACT FROM AUTHOR]

This comprehensive review paper delves into the utilization of Glass Fiber-Reinforced Polymer (GFRP) composites within the realm of concrete column reinforcement, spotlighting the surge in structural engineering applications that leverage GFRP instead of traditional steel to circumvent the latter's corrosion issues. Despite a significant corpus of research on GFRP-reinforced structural members, questions about their compression behavior persist, making it a focal area of this review. This study evaluates the properties of GFRP bars and their impact on the structural behavior of concrete columns, addressing variables such as concrete type and strength, cross-sectional geometry, slenderness ratio, and reinforcement specifics under varied loading protocols. With a dataset spanning over 250 publications from 1988 to 2024, our findings reveal a marked increase in research interest, particularly in regions like China, Canada, and the United States, highlighting GFRP's potential as a cost-effective and durable alternative to steel. However, gaps in current knowledge, especially concerning Ultra-High-Performance Concrete (UHPC) reinforced with GFRP, underscore the necessity for targeted research. Additionally, the contribution of GFRP rebars to compressive column capacity ranges from 5% to 40%, but current design codes and standards underestimate this, necessitating new models and design provisions that accurately reflect GFRP's compressive behavior. Moreover, this review identifies other critical areas for future exploration, including the influence of cross-sectional geometry on structural behavior, the application of GFRP in seismic resistance, and the evaluation of the size effect on column strength. Furthermore, the paper calls for advanced studies on the long-term durability of GFRP-reinforced structures under various environmental conditions, environmental and economic impacts of GFRP usage, and the potential of Artificial Intelligence (AI) and Machine Learning (ML) in predicting the performance of GFRP-reinforced columns. Addressing these research gaps is crucial for developing more resilient and sustainable concrete structures, particularly in seismic zones and harsh environmental conditions, and fostering advancements in structural engineering through the adoption of innovative, efficient construction practices. [ABSTRACT FROM AUTHOR]

Featured Application: The strengthening of the columns and the connections of the columns with the beams for reinforced concrete buildings designed and constructed according to older codes is crucial for regions prone to seismic activity. Herein, the application of the innovative C-FRP ropes for the strengthening of these structural elements is featured. The experimental results yielded from testing real-scale columns demonstrated that this strengthening technique is both highly effective and easy to implement. Moreover, it is emphasized that the C-FRP ropes technique can easily be applied by the practicing engineer in structures with complex configuration without any geometrical restraints. The application of the innovative C-FRP ropes for the strengthening of reinforced concrete columns is experimentally examined. Two real-scale specimens with the same geometrical characteristics and the same steel reinforcements were constructed for the needs of this investigation. The primary objective of the study is to investigate the efficacy of the use of C-FRP ropes as externally mounted reinforcement for the strengthening of deficient external columns. In this direction, (a) C-FRP ropes are applied as longitudinal reinforcement of the column for the increase in the flexural strength, (b) C-FRP ropes are applied as external confining stirrups in the critical end parts of the column for the improvement of the concrete strength and the development of local element ductility, and finally (c) C-FRP ropes are applied as external stirrups in the form of diagonal X-shaped reinforcement for the increase in the capacity of the part of the column connected with the beam (joint panel). Both specimens are tested under the same cyclic loading procedure that comprises seven steps and each step includes three full loading cycles. The maximum loads of the strengthened specimen at the three loading cycles of the seventh step were 40%, 72% and 87% higher than the corresponding ones of the unstrengthened specimen. On the other hand, the measured shear deformations of the joint panel of the pilot (unstrengthened) specimen at the sixth and the seventh steps were 43% and 44% higher than the corresponding ones of the strengthened specimen. In general, it is concluded that the strengthened column exhibited improved hysteretic response and the whole behavior was apparently improved compared to the pilot specimen without strengthening in terms of maximum loads per loading step, dissipated energy, and shear deformations of the joint panel. In particular, it is stressed that the measured shear deformations of the joint panel and strain gauge measurements have substantiated that the column and the connection panel of the strengthened specimen remain almost intact, whereas damage and eventually failure have been located in the column and the joint panel of the pilot specimen. Additionally, it is emphasized that the C-FRP ropes can easily be applied in structures with complex configuration without any geometrical restraints. [ABSTRACT FROM AUTHOR]

To solve the problem of a large amount of fly ash accumulation and study the axial compression and bearing capacity prediction of the self-compacting fly ash concrete filled circle steel tube (SCCFST) columns, eight specimens are designed to explore the impact of concrete strength grade, internal structural measures, and additional parameters. The stress, progression of deformation, and failure mode of each specimen are observed during the loading process. The load–displacement curves, load-strain curves, characteristic load and displacement, ductility, and stiffness degradation are analyzed. The findings revealed that shear deformation occurred predominantly in the middle and upper portions of the steel tubes. Enhancing the strength of the concrete or adopting internal structural measures could increase the bearing capacity and ductility of the specimens. The peak load and ductility could be increased by up to 17.6 and 53.6%, respectively. The proposed unified calculation equation for the axial compression bearing capacity of SCCFST columns demonstrates notable reliability and precision. Furthermore, these tests offer valuable references for the engineering application of various forms of SCCFST columns, which are of significant importance in practical engineering. [ABSTRACT FROM AUTHOR]

Progressive collapse is a phenomenon where initial local failure of a component spreads to surrounding components, resulting in the collapse of the entire structure or most of it. This research is based on the component method (joint simplification model) and the hierarchical shell element macromodeling approach (composite floor simplification model). A three-dimensional spatial composite structural model was established using the finite-element (FE) software ANSYS/LS-DYNA. Experimental results were used to validate the reliability of the FE model. Based on these methods, a typical prototype structural model designed by the National Institute of Standards and Technology (NIST) was established, and a computational analysis of progressive collapse due to component removal was conducted. The results showed that the occurrence of structural collapse depends on the type of beam-column connection, floor level, and type of component removed. Also, it was found that structural collapse is more likely to occur when interior columns, gravity columns (nonresisting lateral column), and low-floor columns are removed. After column failure, the path of vertical loads is mainly transmitted to the columns within the area of direct collapse effect. The area within the potential collapse effect is also exposed to a severe impact phenomenon due to falling floors. Based on the collapse modes and internal force transfer path, an innovative collapse-prevention design method (structural response-based design, or SRBD) is proposed. The SRBD method predicts the collapse response of structure at a theoretical level and avoids redundant modeling and nonlinear calculations in collapse-prevention design. A comparison with collapse response of the NIST model shows that the prediction accuracy is approximately 90%. The SRBD method provides guidance for structural engineers in progressive collapse-prevention design. [ABSTRACT FROM AUTHOR]

This study evaluates gravity‐induced progressive collapse performance and damage mitigation strategies in modular steel buildings (MSBs) A typical three‐dimensional six‐story structure was modeled and analyzed using the finite element method, focusing on the instantaneous removal of a corner module. The study includes a parametric evaluation of the influence of beam moment capacity on progressive collapse and investigates the effect of using concrete as an infill for square hollow section columns. Additionally, the effectiveness of short K‐shaped braces in limiting gravity‐induced collapse was assessed. A response/damage index (DI) was proposed to quantify the overall structural response. The findings indicate that semirigid beam‐column connections outperform fully rigid connections. Both concrete‐filled columns and K‐shaped braces mitigate structural damage, with K‐shaped braces proving more effective in preventing collapse. Although increasing the beam moment‐resisting capacity reduced the DI, improvements were marginal beyond 50% of the fully rigid connection capacity. Higher beam moment capacities reduced local vertical displacement at the corner joint but led to undesirable lateral deformations. Reducing beam rigidity/capacity by 25% mitigated global structural deformations. The optimal beam moment capacity was identified as 75% of the total section capacity when using concrete‐filled columns. K‐shaped braces applied at the column midpoint entirely prevented progressive gravity‐induced collapse and no lateral deformations were observed in braced structures with fully rigid beam‐column connections, unlike unbraced structures. Concrete‐filled columns offer a cost‐effective solution for preliminary production of MSBs, while K‐shaped braces are suitable for retrofitting existing buildings. Further research is necessary to address other parameters influencing the mitigation of progressive collapse in MSBs. [ABSTRACT FROM AUTHOR]

In this paper, the aim is to discuss the applicability of polyethylene terephthalate fiber-reinforced polymer (PET FRP) in DSTC structures. PET FRP can improve the strength and stability of structures by providing constraints for concrete. Herein, experimental and response surface analyses of the axial compressive properties of PET FRP–concrete–steel double-skin tubular stub columns (DSTCs) based on 26 DSTC specimens subjected to axial compression testing are presented. The height of each DSTC specimen is 600 mm, the outer diameter is between 305 and 315 mm, and the thickness of the added concrete is 43 mm. The main parameters are the number of layers on the PET FRP, the compressive strength of the concrete, and the thicknesses of the steel tubes. The experimental results show that the ultimate load and ultimate axial strain can be significantly increased by increasing the number of PET FRP layers, reaching 27.34% and 28.79%, respectively. When the compressive strength of the concrete increases from C30 to C40, the ultimate load and ultimate axial strain values of the DSTCs increase by 12.54% and 8.99%, respectively. In addition, as the thickness of the steel tube increases from 6 to 8 mm, the ultimate load and ultimate axial strain increase by 34.95% and 118.90%, respectively. These results indicate that the introduction of PET FRP significantly improves the overall performance of DSTCs. Increasing the number of PET FRP layers helps to limit the circumferential strain of DSTCs. P6-S8-C40 has the best ultimate load-bearing capacity and ultimate axial strain capacity, which reach 3356.18 kN and 0.1992, respectively. The main purpose of this paper is to study the influences of the PET FRP thickness (in different layers), steel tube thickness, and concrete strength on the properties, damage mode and damage process of DSTCs. [ABSTRACT FROM AUTHOR]

Summary: This study aims to develop an algorithmic approach to obtain optimum designs for tall buildings having composite columns and investigate the material cost advantages of these buildings over steel structures. The social spider optimization (SSO) algorithm, a new meta‐heuristic optimization method that has shown promising results in optimizing frame structures, was used to obtain the optimum designs. Concrete‐filled steel tube sections were chosen for composite columns. To define the optimization problem, we considered the material cost of the structure as the objective function, the size of columns (strength, deflection, drift, and geometric limitations) as the constraint functions, and ready steel sections as the design variables. We tested eight different frame structures of varying heights and irregularities to analyze how cost varied according to these parameters. Our results demonstrate that composite columns are a more cost‐effective option than steel structures, even for buildings that are not considered high rises. We found that the difference in cost between the two types of structures increases with building height and irregularity. Additionally, our optimization algorithm was unable to find feasible designs for steel structures taller than 180 m using ready steel profiles. [ABSTRACT FROM AUTHOR]

The L-shaped partially encased steel–concrete composite (PEC) stub column, composed of profile steel, concrete, and transverse links, tends to occupy less space than the rectangle-shaped PEC column when used as side or corner columns. In this study, an axial compression test involving three L-shaped PEC stub columns was conducted to investigate the influence of critical factors on axial compression performance. The test results indicated that the axial compression capacity can be effectively enhanced with an increase in material strength. Furthermore, finite element (FE) analysis was carried out with parameters such as material strength, steel thickness, transverse link spacing, transverse link diameter, transverse link distribution, and longitudinal rebar diameter. The results revealed that the primary failure modes of L-shaped PEC columns were concrete spalling and local buckling of the flange. Additionally, it was found that the increase in steel strength, steel thickness, and transverse link diameter, as well as the decrease in transverse link spacing, significantly improved the axial compression capacity and concrete confinement effect. However, an increase in concrete strength diminished the concrete confinement effect. Additionally, the accuracy of the axial compression capacity calculation methods in the Eurocode 4 and T/CECS719-2010 specifications for L-shaped PEC stub columns was verified. Finally, a calculation method based on the superposition principle incorporating the concrete confinement effect was proposed, and validated by comparing with experimental and FE results. Overall, this study could provide a theoretical basis for the engineering application of L-shaped PEC columns. [ABSTRACT FROM AUTHOR]

Columns in traditional timber structures are commonly seen resting on stone bases and are very important in resisting lateral loads. This paper numerically modeled the lateral resistance of the columns combined with experimental investigation. Different numerical models were developed, based on which sensitivity analyses were performed. A practical numerical modelling strategy was further proposed and verified. The analysis results indicated that instead of material properties and contact area, the columns' lateral performance was much more sensitive to the variation of surface curvature at bottom surface. Without consideration of the surface curvature, the modeling error in the initial stiffness and peak load of a column was more than 607% and 8%, respectively. By best matching the load–displacement curves of tested column specimens, the optimal surface curvature was identified as 1/20306.5 mm−1. Then, a practical finite numerical model, characterized by the optimal curvature at the bottom surface, was proposed. This modelling method was validated by use of existing test results of traditional timber columns with different diameters and vertical compression loads. The modelling load–displacement curves agreed well with experimental curves both in terms of the initial lateral stiffness and peak load. Detailed simulation results based on the practical modelling strategy were presented and discussed. [ABSTRACT FROM AUTHOR]

An innovative composite structural element, the dune sand concrete-filled circular steel tube (DS-CFCST) column combines the mechanical performance of concrete-filled steel tube (CFST) columns with the environmental and economic benefits of dune sand (DS) concrete. However, current experimental investigations into DS-CFCST columns' axial compressive behavior are limited. This study conducts a numerical analysis to examine the effects of varying DS replacement ratios and the influence of confinement on DS-CFCST stub columns. Finite element (FE) analysis reveals that DS-CFCST stub columns exhibit reduced ultimate bearing capacity compared to CFST columns, primarily due to weakened confinement effects at higher DS replacement ratios. A parametric study investigated the impacts of various design parameters on the ultimate axial bearing capacity of DS-CFCST stub columns. A practical design formula, based on equilibrium principles and the FE model, was developed. This formula simplifies the prediction of the ultimate load-bearing capacity of DS-CFCST stub columns using the superposition method. Its accuracy was validated by comparing it with experimental data and FE results. Lastly, a reliability analysis was performed, showing the DS-CFCST columns' reliability index sensitivity to variations in concrete strength, steel yield strength, steel content ratio, load effect ratio, load combination factor, and DS replacement ratio. [ABSTRACT FROM AUTHOR]

Purpose: Urban excavations are a cause for concern in terms of the probability of damage to nearby structures. In this study, various structural and excavation parameters were investigated to determine the probability of building damage during excavations. Design/methodology/approach: Finite-element analysis software was used to develop a set of valid three-dimensional models. Models were developed to assess the effects of structural parameters (building height and position relative to the excavation site) and excavation parameters (depth and support system type) on the responses of the adjacent buildings. Findings: The new design charts estimated the damage to reinforced concrete frame buildings during excavation by focusing on the angular distortion of the building, additional shear strain on the masonry walls and additional strain and stress on columns. This study showed that the probability of damage decreased as the distance between the building and the excavation increased. By contrast, it increased when the building was located at a distance equal to the excavation depth at its edge. According to this study, the axial stress caused by the excavation of building columns does not exceed 10.9% of the compressive strength of the concrete. Originality/value: The proposed design charts can replace comparable charts and provide a deeper understanding of damage potential based on key parameters. These charts are more practical than previous charts with limited parameters. [ABSTRACT FROM AUTHOR]

This research offers an in-depth exploration of the mechanical behavior of square steel tubular columns reinforced with concrete under axial compression. The study particularly focuses on how initial conditions, including initial stress and structural defects, influence the columns' performance. By employing ABAQUS for finite element analysis, the investigation covers a broad spectrum of slenderness ratios, systematically assessing how these factors affect the structural integrity of the columns. The analysis reveals that while initial stress tends to reduce the peak load-bearing capacity, it paradoxically enhances the ductility of the columns, a critical aspect of their performance under load. Conversely, initial defects, particularly in slender columns, exacerbate instability, leading to significant reductions in load-bearing capacity. These findings highlight the pivotal role of initial conditions in shaping the mechanical behavior and overall safety of steel-reinforced concrete columns. The study's insights contribute to a deeper understanding of the load-bearing mechanisms and provide a robust framework for improving the precision and dependability of structural design. By integrating considerations of initial conditions into the design process, engineers can significantly bolster the safety and durability of composite columns, especially in high-risk applications such as high-rise buildings and bridges. [ABSTRACT FROM AUTHOR]

A column is a critical member in a reinforced concrete framed building. It transfers lateral shear during an earthquake, in the presence of gravity loads. Failure of short wall-type shear-critical columns in the soft and weak open ground story (OGS) of a building during an earthquake can trigger pancake-type collapse. To avoid these types of failures, the weak columns in the OGS can be strengthened locally, in addition to a global retrofit strategy applied to the entire structure. This research focuses on the seismic strengthening of such short columns using the concrete jacketing technique. The study presented in this paper demonstrates a methodology to model the shear behavior of short columns before and after jacketing. This pertains to the nonlinear static analysis of a building under lateral loads, such as a static pushover analysis. The development of shear hinge properties for as-built and jacketed short columns is presented in this paper. These were based on a proposed generalized truss analogy, which was validated based on the tests of column specimens conducted as part of this research. Pushover analyses of a building model without and with jacketed columns in the OGS were conducted. Selected results of the analyses are presented in this paper. The modeling of the shear hinge properties for the short columns in the OGS demonstrated the brittle behavior under lateral loads before jacketing and the improvement in ductility after jacketing. The proposed method can be used in professional practice for evaluating buildings with short columns strengthened by concrete jacketing. Since all the columns in a story cannot be jacketed due to economic and functional considerations, the effect of selective jacketing of the columns on the behavior of the building under lateral loads is illustrated. Practical Applications: An existing reinforced concrete framed building can be retrofitted to mitigate the damage expected during a future earthquake. The effect of retrofit on the structure should be justified preferably by a nonlinear method of analysis such as pushover analysis. The primary input in such an analysis is the nonlinear behavior of each structural member under increasing lateral loads, modeled as the hinge property. The presented study discusses the pushover analyses of a building, before and after strengthening its short wall-type columns in the open ground story by concrete jacketing. A method to develop the shear hinge properties of as-built and jacketed short columns is explained in this paper. The method is based on extending the truss analogy for modeling the shear deformation of a short frame member after the diagonal cracking of concrete in the web. The procedure does not need any special purpose program for calculation and can be implemented using a spreadsheet. Also, a parametric study on optimum strengthening is presented, showing the effect of jacketing selected columns, as all the columns need not be intervened, to reduce the cost as well as the disruption to the users. [ABSTRACT FROM AUTHOR]

Warping not only one of the most important phenomena in steel section it is also considered as the most complicated phenomena. Ductility, bearing capacity and serviceability of steel sections may affect by increasing stress concentration of the normal stresses due to warping. In the present work, simulation of steel beam section under effect of warping is studied. Two cantilevers connected to two columns in opposite sides with a middle steel beam-column connection to create different moments on the beam to investigate the behavior of steel section under warping using building information modeling. It is found that the stress strain relationship has four groups depending on the load intensity and the angle of rotation induced due to warping. [ABSTRACT FROM AUTHOR]

In this paper, structural columns with cross-section sizes of 100 mm × 100 mm, 75 mm × 150 mm, and 85 mm × 121 mm are designed based on the same notional size of member. The acceleration signals of each column at axial compression ratio of 0.1, 0.2 and 0.3 were obtained by impact hammering. The corresponding frequency and damping ratio are obtained by half power wideband method. Based on the statistical method, the variation rules of acceleration signal characteristics, frequency characteristics and damping characteristics in different thickness directions under different axial compression ratios were analyzed. The correlation between frequency and damping ratio in different thickness directions with different axial compression ratios is discussed. The results show that under the same axial compression ratio, the damping ratio and frequency tend to decrease with the increase of the thickness in the tapping direction. Under the same thickness, the frequency decreases with the increase of the axial compression ratio. The damping ratio of the column decreases with increasing stress ratio when the thickness in the knocking direction is less than 100 mm. The damping ratio of the column increases with the increasing stress ratio when the thickness in the knocking direction is equal to 100 mm. The damping ratio of the column increases slightly with the increasing stress ratio when the thickness in the knocking direction is greater than 100 mm. By fitting the discrete data, the frequency variation range is 229.65–511.07 Hz, and the range of the damping ratio variation is 0.1–0.5%. [ABSTRACT FROM AUTHOR]

AbstractThis study aims to investigate the crashworthiness performance of a novel hierarchical multi-cell double circular tubes (HMDC) structure under axial impact. Various dual-tube structures of different cross-sections were designed. The effects of hierarchical order, peak number of the core column, and inner circle diameter on the structure were analyzed using Abaqus finite element analysis. The results indicate that in dual-tube structures, replacing the traditional multi-cell structure with a hierarchical multi-cell structure in the interlayer significantly improves energy absorption (EA) characteristics. With the inner circle diameter of the HMDC fixed at 20 mm, the ratio of mean crushing force (MCF) to peak crushing force at the third order increased by 70.70% and 35.68% compared to the first and second orders, respectively. Experimental results and finite element results show that the initial peak value differed by 1.47%, indicating a close match between the experimental and simulation results. The parametric study shows that the inner circle diameter and the peak number of the core column significantly affect EA. The findings of this study provide effective guidance for designing multi-cell dual circular tubes with high EA efficiency. [ABSTRACT FROM AUTHOR]

Concrete-filled hollow section (CFHS) columns with a solid steel core have gained popularity in the construction of tall buildings due to their robust load-bearing capacity, slender design, ease of prefabrication, and exceptional structural fire resistance. In this research paper, we introduce an innovative approach aimed at enhancing the structural performance of these columns. Our method involves replacing the solid steel core with high-strength bar bundles and substituting concrete with grout to achieve superior fire resistance. These modified columns are referred to as "bar-bundle columns." The paper presents the results of extensive fire tests conducted on three bar-bundle columns, each with different bar-bundle sizes, quantities, and configurations. Additionally, we determine the temperature-dependent material properties of the high-strength steel used for reinforcing bars and the thermal properties of the grout used as a filler through standard experimental tests, which are crucial for numerical simulations. An advanced nonlinear finite element model is describe which is capable of predicting the fire behavior of bar-bundle columns. Finally, this numerical model is employed to conduct parametric analyses and propose a simplified design model for bar-bundle columns under fire conditions.Our findings indicate that the bar-bundle configuration and using grout as a filler significantly delays the heating of the steel core, resulting in enhanced fire resistance when compared to CFHS columns with a solid steel core. The simplified method proposed in this study can be used to estimate the fire resistance of slender bar bundles, but further experimental testing could further refine and improve its accuracy. [ABSTRACT FROM AUTHOR]

Ferrochrome slag (FCS), a type of industrial solid waste, has promising properties that make it a viable alternative aggregate for concrete production. This can be a partial solution to reduce the pressure on natural aggregates. However, the usage of this solid waste in concrete or composite structures is not documented well. As a result, the purpose of this study is to evaluate experimentally the effect of employing FCS concrete in the concrete-filled steel tube (CFST) on strength and its fire-resistant capabilities. The influence of heating temperatures ranging from 200 to 800 °C and the level of FCS fine aggregate substitution on load–displacement behaviour, ultimate load, and failure mechanism was examined. The CFST stub columns were filled with three different concrete mixtures: one with 100% natural fine aggregate and the other two with 50% and 100% FCS fine aggregate. The findings demonstrate that the ultimate load and stiffness of the CFST stub columns increased as the amount of FCS fine aggregate in the concrete increased. Similar results were found for residual strength and stiffness after high-temperature exposure. The fine natural aggregate can be fully replaced by the FCS fine aggregate without compromising any strength properties of concrete, as well as CFST columns at room and high temperatures. The Eurocode 4 and ACI codes show a conservative estimation of ultimate strengths for the CFST stub columns at room and elevated temperatures compared to the experimental results for all three concrete mixes. However, Eurocode 4 provides a closer estimation for the ultimate load for all concrete mixes than the ACI recommendation. [ABSTRACT FROM AUTHOR]

Significant advancements have been made in the area of composite structures. Aligned with an innovative design, the motivation behind this research is, first, to make efficient use of timber as an environmentally friendly material and, second, to employ steel alongside timber effectively to prevent buckling of the steel. This research aims to bridge this knowledge gap by exploring the integration of steel, carbon fiber–reinforced polymer (CFRP), and timber. The objective is to create innovative composite column structures that leverage the unique properties of each material to enhance structural performance and efficiency. The authors conducted tests on a set of 24 columns under compression conditions. The results of the structural tests demonstrated significant compression capacities relative to their mass, highlighting the significant advantages of material synergy within these elements. The study thoroughly quantifies these benefits, shedding light on the potentially transformative impact of these innovative composite columns in the field of structural engineering. A significant finding was the influence of the timber section's geometry on preventing column buckling. Furthermore, the positioning of steel within the sandwich columns played a vital role, with steel elements having a greater area with timber exhibiting enhanced structural performance and reduced likelihood of debonding. This paper introduces a new parameter, the inelastic transition area denoted as INT±70% peak , which characterizes the smoothness or abruptness of the transition once the inelastic region begins and the graph descends. This parameter bears significance in risk analysis for structures susceptible to progressive failure. All specimens displaying substantial energy absorption featured larger timber sections, highlighting the pivotal role of timber in absorbing higher levels of energy during structural loading. The findings contribute to the growing body of knowledge on composite materials and their applications in modern construction. [ABSTRACT FROM AUTHOR]

In recent years, Concrete-Filled Double-Skin Tube (CFDST) columns have become a promising structural system, demonstrating improved strength, ductility, and sustainability when compared to conventional column designs. CFDST columns comprise two steel tubes placed concentrically infilled with concrete. Square and circular hollow steel sections are commonly used in CFDST. The higher strength-to-weight ratio is a primary factor in preferring CFDST columns over Concrete-Filled Steel Tube (CFST) columns. In this study, a circular CFDST column is modeled and validated using the Finite Element Analysis-based software ABAQUS. The response of the CFDST column under blast loading is explored. The influence of variables such as axial loading, outer steel tube thickness, hollowness ratio, angle of incidence, and scaled distance on blast resistance is determined through the parametric study. The study also explores the effectiveness of the introduction of steel reinforcement in the concrete infill of the CFDST column for enhancement of blast resistance. The results highlight that increasing the outer steel tube thickness and incorporating steel reinforcement lead to an enhanced blast resistance of structures. However, the study does not find definitive evidence indicating that the hollowness ratio affects the behavior of the CFDST column. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Education, Technology & Society (BRAJETS) / Cadernos de Educação Tecnologia e Sociedade (CETS) is the property of Brazilian Journal of Education, Technology & Society - BRAJETS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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In this research, the cyclic behavior of concrete-filled thin tube (CFTT) columns with bidirectional moment connections was numerically studied within the context of thin-walled structures. Novel considerations in the design of CFTT columns with slenderness sections are proposed through a parametric study. A total of 70 high-fidelity finite element (FE) models are developed using ANSYS software v2022 calibrated from experimental research using similar 3D joint configurations. Furthermore, a comparison of different width-to-thickness ratios in columns was considered. The results showed that the models with a high slenderness ratio reached a stable cyclic behavior until 0.03 rad of drift, and a flexural strength of 0.8 Mp was reached for 4% of the drift ratio according to the Seismic Provisions. However, this effect slightly decreased the strength and the dissipated energy of the moment connection in comparison to columns with a high ductility ratio. Moreover, an evaluation of concrete damages shows concrete cracked for cyclic loads higher than 3% of drift. Finally, the joint configurations studied can achieve a good performance, avoiding brittle failure mechanisms and ensuring the plastic hinges in the beams. [ABSTRACT FROM AUTHOR]

Special-shaped partially encased steel–concrete composite (PEC) columns could not only improve the aesthetic effect and room space use efficiency, but also exhibit good mechanical performance under static load when used in multi-story residential and office buildings. However, research on the seismic performance of special-shaped PEC columns is insufficient and urgently needed. To investigate the seismic performance of cross-shaped partially encased steel–concrete composite (CPEC) columns, three CPEC columns were designed and tested under combined constant axial load and lateral cyclic load. The test results show that the CPEC columns had good load capacity and ductility, and that the columns failed because of concrete crushing and steel flange buckling after the yielding of the steel flange. The plump hysteresis loops indicated that the CPEC column also had good energy dissipation capacity. Due to the constraint of hydraulic jacks, increasing the load ratio would decrease the effective length, thereby increasing the load capacity of the CPEC column and decreasing the ductility. A finite element model was also established to simulate the response of the CPEC columns, and the simulated results agree well with the experimental results. Thereafter, an extensive parametric analysis was performed to study the influences of different parameters on the seismic performance of CPEC columns. For the CPEC column with an ideal hinged boundary condition at the top, its lateral load capacity gradually decreases with the growth of the load ratio and link spacing and increases with the rise of the steel yield strength, concrete compressive strength, flange and web thickness, and sectional aspect ratio. This research could provide a basis for future theoretical analyses and engineering application. [ABSTRACT FROM AUTHOR]

This paper aims to study lateral behavior of the semi-mortise-tenon (SMT) jointed frame with free-standing columns with elastic-plastic deformations in the traditional timber building. The frictional and compressive forces at contact interfaces of SMT connection are calculated through the volumes of elastic and yielding deformations perpendicular-to-grain, and the compressive force is analyzed considering the elastic and yielding deformations parallel-to-grain at the bottom of column. The elastic-plastic behavior of timber frame with SMT and column foot (CF) connections under different vertical loads is assessed. The results reflect that the main plastic deformation of the timber frame occurs at SMT connections perpendicular-to-grain, and the effect of the plastic deformations parallel-to-grain at CF of the timber frame on its lateral resistance is relatively small, the lateral resistance of the wood frame shows a trilinear characteristic. Moreover, the gravity load of the upper structure does not directly affect the plastic deformation perpendicular-to-grain at SMT connections—the SMT connection of the timber frame with a larger gravity load of an upper structure is more likely in the plastic stage than that of a smaller gravity load of an upper structure. [ABSTRACT FROM AUTHOR]

For the new type of steel-concrete inclined column transfer structure (NSCICTS) with better lateral stiffness and ductility, the existing damage model and hysteresis model are difficult to accurately express the asymmetry of its test restoring force curve and the serious pinching phenomenon of the hysteresis curve, respectively. In this paper, an asymmetric damage model is firstly established according to the asymmetry of the curve, and the comparison with the existing symmetric damage model shows that the asymmetric damage model proposed can reflect the actual damage of the component or structure. Then, a simplified hysteresis loop model with a longer slip segment is established, and the damage formulas of the stiffness and residual deformation are established. Finally, the hysteresis rules are given, and the comparison with the test hysteresis curve shows that the proposed model can better simulate the structural mechanical properties. The model provides a theoretical basis for the overall nonlinear seismic analysis of the NSCICTS and other similar structures. [ABSTRACT FROM AUTHOR]

This paper attempts to utilize lower order harmonics and modes of vibration consisting of "square ratios of frequency variations" as structural damage susceptibility characteristics. This is followed by the development of the frequency-based method. Firstly, this paper derives the theoretical formulation of the square ratio of frequency variation method. Secondly, a finite element model of a single column platform is established. Then the damage is simulated using the reduced modulus of elasticity to localize the damage. The result is shown to be feasible. Thirdly, a model of the offshore single column platform is constructed, and the damage is simulated using cracks on the column. The "frequency variation square ratio" is valid, so the method can be used in reality. This method is applied to the single column platform model, suitable for a beam structure. It is very effective for the single column damage identification at different damage levels, and can also initially locate the damage. This method has high practical application value and reference value for future studies. [ABSTRACT FROM AUTHOR]

The specifications of AISC 360 and Eurocode 4 for the design of composite columns limit the maximum steel tube yield stress and concrete compressive strength. In this study, the limitations mentioned in the design codes are evaluated, and a new simplified relation for the nominal compressive capacity of square high-strength concrete-filled high-strength steel tube (HsCHsST) stub columns is proposed. The present study was carried out in three parts. The first part involves compiling a test database of square-filled composite columns with high-strength materials to achieve the aptest relation. The second part consists of developing a simplified relation for determining the effects of material strength on the nominal compressive strength of columns ( P n ) based on the compiled database using a hybrid gene expression programming-invasive weed optimization algorithm. Finally, a new resistance factor ( ϕ c ) for axially loaded HsCHsST columns is determined in the third part. The predicted results for nominal compressive strength were compared with specifications of AISC 360 and Eurocode 4 in terms of various performance parameters based on measured results to validate the proposed relation. This study's findings can be used as a suitable tool in the design compressive strength of square HsCHsST members. [ABSTRACT FROM AUTHOR]