Search

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

As a sustainable solution, employing recycled tire rubber aggregates in the production of concrete is of considerable interest. However, the applicability of rubberized concretes in construction is restricted due to their relatively low mechanical performance. Using rubberized concrete as a filling material in a steel tube provides a suitable solution for overcoming this issue and for using it effectively as a load‐bearing element. The objective of this study is to examine the impact of the material characteristics of the sustainable rubberized concrete‐filled steel tube (Ru‐CFST) and develop a design model based on ultimate strength prediction for the axially loaded Ru‐CFST stub columns with varying contents of tire rubber aggregate. The model was developed through the gene expression programming (GEP) technique by employing the experimental test results to determine the ultimate compressive strength of Ru‐CFST columns. Based on the principal component analysis, the sectional properties of the load‐bearing element (such as outer diameter, thickness, and length), material strengths (such as rubberized concrete and steel tube strengths), and rubber content were determined as statistically significant parameters affecting the ultimate axial strength of Ru‐CFST stub columns and thus, they were considered in the stage of the model generation. Furthermore, the proposed model's performance was compared to that of available models suggested for traditional CFST columns by commonly employed design codes, namely, ACI, AIJ, AISC, CSA, EC4, and GB. Based on the statistical analysis of the results, it can be concluded that the existing formulations have a relatively acceptable randomness and scatter of observations within the distribution, while the proposed design model gives a more accurate prediction for the ultimate bearing capacity of axially loaded Ru‐CFST columns with the highest R‐squared value of about 0.99 and the comparatively lowest mean absolute percent error of 7.54. It can be stated that the proposed GEP‐based design model will encourage engineers to use such sustainable structural members in their designs and constructions. [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]

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]

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]

Copyright of Latin American & Latinx Visual Culture is the property of University of California Press 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 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]

Concrete-filled double steel tubes (CFDSTs) are a load-bearing structure of composite materials. By combining concrete and steel pipes in a nested structure, the performance of the column will be greatly improved. The performance of CFDSTs is closely related to their design. However, existing codes for CFDST design often focus on how to verify the reliability of a design, but specific design parameters cannot be directly provided. As a machine learning technique that can simultaneously learn multiple related tasks, multi-task learning (MTL) has great potential in the structural design of CFDSTs. Based on 227 uniaxial compression cases of CFDSTs collected from the literature, this paper utilized three multi-task models (multi-task Lasso, VSTG, and MLS-SVR) separately to provide multiple parameters for CFDST design. To evaluate the accuracy of models, four statistical indicators were adopted (R2, RMSE, RRMSE, and ρ). The experimental results indicated that there was a non-linear relationship among the parameters of CFDSTs. Nevertheless, MLS-SVR was still able to provide an accurate set of design parameters. The coefficient matrices of two linear models, multi-task Lasso and VSTG, revealed the potential connection among CFDST parameters. The latent-task matrix V in VSTG divided the prediction tasks of inner tube diameter, thickness, strength, and concrete strength into three groups. In addition, the limitations of this study and future work are also summarized. This paper provides new ideas for the design of CFDSTs and the study of related codes. [ABSTRACT FROM AUTHOR]

• OCR-detected characters or words in an image require line segmentation to reunite into word or sentence. • Projection based line segmentation cannot be applied to Chinese historical texts. • Columns in Chinese historical texts exhibit a sub-divided column format. • Adjacent character detection (ACD) algorithm can deal with the unique column structure. • Performance of ACD algorithm as a post-processing of OCR is discussed. In recent times, the advent of AI-based optical character recognition (OCR) has garnered significant attention in the realm of digital text conversion. However, it is imperative to note that OCR solely identifies individual characters or words, and lacks the ability to reunite them into cohesive units such as words or sentences. Consequently, the manual sorting of them to establish the appropriate reading order has emerged as a bottleneck. In this paper, we present an algorithm termed adjacent character detection (ACD), designed to serve as a post-processing of OCR, facilitating automatic digital text conversion. The algorithm involves line segmentation through a quad-ACD scan (up-down-down-up), allowing it to consecutively discern characters within a column based on their adjacency relations. Conventional projection profile analyses have struggled to effectively partition the distinct internal structure of Chinese historical text, where two annotation columns often subdivide from a single body column. In contrast, our ACD algorithm employs an approach, reuniting adjacent characters rather than fragmenting the entire text into isolated entities. Additionally, ACD algorithm enabled body/annotation classification for OCR-detected characters based on the pattern analysis of its quad scan. This cumulative information empowers the conversion of digital text in a desired reading order. To assess the efficacy of the proposed algorithm, a set of ground-truth OCR result was subjected to rigorous testing, culminating in a reading order accuracy of 98.6%. Noteworthy robustness was also demonstrated in the face of misaligned columns, experimentally induced by applying tilt, warp, and wavy noises to the original digital images. Lastly, the algorithm was integrated with two pre-developed OCR models, resulting in a reading order accuracy of 97.7%. [Display omitted] [ABSTRACT FROM AUTHOR]

Beam–column connections with corbels supporting the beams and continuity reinforcement protruding from the columns, also known as composite connections, are often used in construction as an alternative to monolithic cast-in-place connections. Since they are halfway between fully rigid and pin connections, these semirigid composite systems require more in-depth investigation, especially concerning their behavior at high temperatures and in fire. Compared with fully rigid connections, the primary advantage of semirigid systems is that they allow the use of precast beams. Unlike pin connections, semirigid systems allow a certain degree of fixity at beam ends after the in-place casting of the top of the beams. This study focused on the designs of two full-size specimens representing the region of the connection comprising the column stub, corbel, and beam extremity cast and tested in ambient conditions and under standard fire exposure to compare their performance with two monolithic specimens tested under the same conditions. The study also develops a numerical model of the connection using a finite-element discretization (ANSYS software) to conduct a sequential analysis of the thermal and static behavior of the connection. The numerical results are shown to satisfactorily fit the deflection curves, crack patterns, and actual conditions of the specimen after failure. The semirigid connection is stiff at ambient and medium temperatures but behaves as a pin connection at high temperatures. Further, the moment redistribution with a decreasing hogging moment at the beam ends and higher sagging moment at the midspan shows that semirigid beam–column connections are more vulnerable at high temperatures than monolithic connections. [ABSTRACT FROM AUTHOR]

Cold-formed rack profiles are produced mainly for use in industrial storage systems. Their complex geometry and the presence of hole patterns along their length make the strength prevision of these structural elements difficult. This article evaluates the safety presented in the design of rack columns by adaptations of the Direct Strength Method (DSM), the original formulation of which does not address perforations. The safety parameters used here are the reliability indexes, calculated by the First Order Second Moment (FOSM) method, used in the calibration of the AISI S100 current standard, the First Order Reliability Method (FORM) and Monte Carlo Simulation. Only methodologies that applied the reduced thickness method in cross-section modelling produce results close to the target reliability indexes suggested for cold-formed columns. The target indexes are met for all load combinations when only distortional buckling failure is considered. However, the DSM adaptations are still imprecise when considering failure with local buckling. New professional factors were calibrated for these cases, as the design using the current $\phi =0.85$ ϕ = 0.85 does not meet the safety requirements. [ABSTRACT FROM AUTHOR]

Accurate identification of the failure modes of Reinforced Concrete (RC) columns based on the design parameters of the structural members is critical for earthquake-resistant design and safety evaluation of existing structures. Existing identification methods have some problems, such as high cost, incomplete consideration of influencing factors, and low precision or recall in identifying shear or flexural-shear failure. In this paper, the main factors for the failure modes of RC columns are first analyzed and studied. Then, the problem of class imbalance in data samples is investigated. To identify the failure modes of RC columns, oversampling of data (BSB-FMC), model ensembling (RFB-FMC), cost-sensitive learning (CSB-FMC) and a fusion model of three strategies (BSFCB-FMC) are proposed. And finally, the SHapley Additive exPlanations (SHAP) method is used to provide a better interpretation of the designed model. The results show that the developed strategies can improve the accuracy of identifying the failure modes of RC columns compared to the models using a single Artificial Neural Network (ANN), a Support Vector Machine (SVM), a Random Forest (RF), and Adaptive Boosting (AdaBoost). The overall accuracy of the developed BSFCB-FMC model reaches 97%, and the precision and recall for the three failure modes are both above 90%. The designed model provides a solution for fast, accurate and cost-effective identification of the failure modes of RC columns. • We develop the models for identifying the failure modes of RC columns considering class imbalance problem. • The BSFCB-FMC model is developed by considering data oversampling, model ensembling, and cost-sensitive learning. • The designed model provides engineers with an interpretable, fast and stable model for identifying failure modes. [ABSTRACT FROM AUTHOR]

A circular, hollow tubular steel column is introduced for experimental and analytical analysis in this study. A series of axial compression tests for the variation of static schemes are reported in this study. All theoretical, numerical, and experimental analyses are based on the European Standards for the steel structure, respectively EN 1993-1-1. The experimental models of steel columns are conducted on actual steel columns with a length of 3000 mm and a circular hollow section of 114.3/2.8 mm. To assess the behavior and stress values of the columns, various schematically supported systems are modeled, starting from the axial-centered columns to the symmetrical eccentric load and asymmetrical loaded columns. 3D modeling of the steel columns using the finite element program SEISMOSOFT is also developed for such elements. The accuracy of the model is compared with the experimental results using numerical analysis by the finite element method. Finally, the numerical comparison of the results provides a recommendation for the engineers regarding the design and construction of such columns. [ABSTRACT FROM AUTHOR]

This paper focuses on the experimental investigation of the axial load capacity of CFT (concrete-filled steel tube) columns under actual construction conditions during building reconstruction. A total of four samples were loaded up to failure. The varied parameters were the column length and absence/presence of the concrete infill within the steel tube. Further, the analysis is extended to developing a numerical model in the finite element-based software ABAQUS version 6.9. This numerical model includes material and geometrical nonlinearities and was validated with the experimental results. The contribution of the concrete core to the column capacity and the concrete core confinement effect are discussed. Finally, the column capacity was calculated according to several design codes: the Eurocode 4 with and without considering the confinement effect, American specifications, Australian standards, the American Institute of Steel Construction, and the Architectural Institute of Japan. The Eurocode 4 considering the confinement effect provides the closest results to those obtained in the tests. [ABSTRACT FROM AUTHOR]

In this study, three artificial intelligence models, namely group method of data handling, gene expression programming and random forest, are proposed to predict the ultimate bearing capacity of concrete filled steel tube stub columns. A total of 220 data samples collected from the literature was used to construct the three models. Five statistical indices were used to evaluate the performance of the three models and the other five existing design codes and two reference models. Compared with the optimal model among the seven existing models, the coefficient of variation, mean absolute percentage error, root relative squared error and integral of absolute error values of all datasets of the three models (i.e., group method of data handling, gene expression programming and random forest) were decreased by 46.47%, 56.49%, 71.35% and 65.78%; 49.82%, 59.49%, 66.88% and 64.51%; 79.27%, 84.83%, 78.64% and 83.71%, respectively; while the determination coefficient values of all datasets of the three models were increased by 7.36%, 6.79% and 8.22%, respectively. The results show that the predicted results of the three models agree well with the experimental results, and the random forest model has the best comprehensive performance. [ABSTRACT FROM AUTHOR]

This work aims to investigate the behavior of textile‐reinforced concrete (TRC) members subject to compressive loads. An experimental program including concentric compression tests on I‐section columns with different lengths and simply‐supported ends was carried out. From compression tests, load versus lateral deflection curves obtained experimentally are reported along with maximum loads and apparent imperfections determined using the Southwell technique. Failure modes were characterized by excessive lateral deflections for longer columns, whereas concrete crushing failure due to combined bending and axial load occurred for shorter columns. Surrounding concrete was effective in restraining the textile reinforcement against buckling, allowing it to sustain the compressive loads. A single degree‐of‐freedom model accounting for normal‐moment‐curvature relation and tension stiffening behavior is validated against experiments and used to carry out a parametric study. Results show that the nonsway moment magnification method recommended by the ACI Code 440.11‐22 can be applied to TRC columns, although leading to overestimated second‐order effects. [ABSTRACT FROM AUTHOR]

Pillar restoration at the Alte Brücke Heidelberg Most people are probably familiar with the Alte Brücke Heidelberg as a photo motif. Built in 1788 as a masonry bridge made of sandstone, it spans the Neckar with seven arches with a view of Heidelberg Castle. However, what happened in the shadow of the bridge in recent years remained undiscovered by most people. During structural inspections in 2008 and 2016, damage was detected and documented on all pillars of the Alte Brücke Heidelberg, both in the water change zone and in the permanently dammed area. These were primarily foot washouts and damage to the natural sandstones. In addition, stone clamps were reworked and impact angles on the pillar tips were replaced and supplemented during these investigations. In order to carry out the necessary renovation work, the pillars had to be drained. Due to the adjacent shipping openings and the resulting tight space conditions, a slim caisson had to be constructed for this purpose, which could be placed exactly on the foundation base of the pillars and did not obstruct the ongoing shipping. The two‐part caisson had a total weight of almost 32 ts and was floated into place around the respective bridge pillars in short shipping blocks during the night using two specially assembled pontoons. The two halves of the caisson were then connected, lowered and anchored to the ground to create a closed, sealed working area around the bridge pillar. [ABSTRACT FROM AUTHOR]

The quality of being adaptable/deployable of tensegrity structures provides intriguing challenges for researchers and designers. In this work, the shape-change capabilities of a V-Expander tensegrity column are analyzed: a numerical investigation is carried out for the study of the cable-actuation process for a column composed of elementary V-Expander tensegrity cells sharing horizontal cables. The actuation is performed by considering suitable sets of active and passive cables among the whole set of cables of the column. The attention is focused on the following kinds of shape-changes: stretching/shrinking, flexure, shear and torsion. Moreover, a strategy for predicting the nonlinear response of the tensegrity column in the cable-actuation process is proposed. This strategy allows for estimating quickly, among all the possible choices of active and passive cable sets, those leading to maximum displacements or rotations and to the minimum ratio between the normalized work of active cables and the deformation of the column. Further numerical analyses are performed by varying the aspect ratio of the V-Expander cell, to evaluate the effects of changes in the geometrical parameters on the nonlinear actuation process of the column. Tensegrity structures have inspired artists, biologists, engineers, and architects. Many studies have been conducted in recent years, especially related to geometry, form finding, static analysis, and dynamic response. Their use is very encouraging in projects requiring adaptable and/or deployable structures. Indeed, a tensegrity system can provide the minimal mass structure required to sustain a given external load, an intriguing feature for uses as lightweight deployable systems, such as satellites, antennas, or robots. Tensegrity systems are reticulated structures composed of bars in compression maintained in equilibrium by a network of cables in tension. This work focuses on the shape-change capabilities of V-Expander tensegrity columns, a promising type of tensegrity system in this context. Shape change can be obtained by shortening some cables using actuators, while other cables lengthen elastically keeping the system in equilibrium during the process. A fast linear prediction strategy is proposed for evaluating the efficiency of any choice of actuated elements. This strategy allows to prefigure the choices of lengthening and shortening cables which lead to the most efficient shape-change processes of V-Expander columns, here presented for the first time. Such a strategy can be applied with minor adjustments to the other types of tensegrity systems. [ABSTRACT FROM AUTHOR]

As an effective measure to decrease the residual displacement under earthquakes, unbonded prestressed concrete (UBPRC) columns have been carefully investigated in previous research, while the influence of the complex characteristics of near-fault excitations on the residual displacement of UBPRC is less mentioned. This paper, therefore, focuses on the influence mechanism of the pulse effect and vertical effect of near-fault ground motions on the residual displacement of UBPRC columns. The residual displacement, at first, is formulated as a function of the coupled parameter T1-p (the ratio of the structural period to the pulse period). Then, the effect of near-fault vertical ground motion on the residual displacement is qualified based on the established mathematical model. Further, the model has been applied to investigate the effect of structural properties (dead load axial compression ratio, longitudinal reinforcement ratio, prestressing axial compression ratio, prestressing reinforcement ratio) on the residual displacement of UBPRC columns subjected to the joint action of horizontal and vertical ground motions. This research provides a quantitative methodology to quickly obtain the residual displacement spectra of the UBPRC columns under varying conditions combined with ground motion and structural parameters. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) columns, being axial-bearing components in buildings, are susceptible to damage and failure when subjected to blast loading. The failure of these columns can trigger a progressive collapse in targeted buildings. The primary objective of this study is to investigate the failure characteristics of laboratory-scale RC columns subjected to localized blast loading. The columns, with a length of 1500 mm and an outer diameter of 100 mm, are reinforced with 6 mm diameter longitudinal bars and 2 mm diameter steel ties. The blast loading is generated using an explosive-driven shock tube (EDST) positioned in front of the mid-span of the RC columns with a 30 g and 50 g charge. To capture the global response of the RC columns, high-speed stereoscopic DIC is used in addition to LVDTs. Furthermore, an FE model is developed using LS-DYNA R10.0 and validated against the experimental data. The results show that the proposed FE approach is able to reproduce the applied blast loading and the failure characteristics of the columns. The relative difference in column mid-span out-of-plane displacement between the FE model and the average measured data lies below 5%. Finally, the gray correlation method is conducted to assess the influence of various parameters on the blast resistance of the RC columns. [ABSTRACT FROM AUTHOR]

Pillar stability is of paramount importance in ensuring the safety of underground rock engineering structures. The stability of pillars directly influences the structural integrity of the mine and mitigates the risk of collapses or accidents. Therefore, assessing pillar stability is crucial for safe, productive, reliable, and profitable underground mining engineering processes. This study developed the application of decision intelligence-based predictive modelling of hard rock pillar stability in underground engineering structures using K-Nearest Neighbour coupled with the grey wolf optimization algorithm (KNN-GWO). Initially, a substantial dataset consisting of 236 different pillar cases was collected from seven underground hard rock mining engineering projects. This dataset was gathered by considering five significant input variables, namely pillar width, pillar height, pillar width/height ratio, uniaxial compressive strength, and average pillar stress. Secondly, the original hard rock pillar stability level has been classified into three types: failed, unstable, and stable, based on the pillar's instability mechanism and failure process. Thirdly, several visual relationships were established in order to ascertain the correlation between input variables and the corresponding pillar stability level. Fourthly, the entire pillar database was randomly divided into a training dataset and testing dataset with a 70:30 sampling method. Moreover, the (KNN-GWO) model was developed to predict the stability of pillars in hard rock mining. Lastly, the performance of the suggested predictive model was evaluated using accuracy, precision, recall, F1-score, and a confusion matrix. The findings of the proposed model offer a superior benchmark for accurately predicting the stability of hard rock pillars. Therefore, it is recommended to employ decision intelligence models in mining engineering in order to effectively prioritise safety measures and improve the efficiency of operational processes, risk management, and decision-making related to underground engineering structures. [ABSTRACT FROM AUTHOR]

This paper presents a computational model for determining the axial responses of short circular steel–reinforced concrete-filled steel tubular (SRCFST) columns. A novel confinement model is formulated for the concrete core, which is effectively confined by the external circular steel tube and the embedded steel section. The modelling scheme of the confinement is programmed using a mathematical model that utilises fibre-element discretisation of column cross-sections. The numerical predictions are verified by experimental measurements and results obtained from finite-element analysis, demonstrating the accuracy of the modelling technology. In addition, existing concrete confinement models for concrete in circular concrete-filled steel tubular columns are assessed. The new confinement model is shown to be superior in replicating the responses of SRCFST columns. The influences of the design parameters on the column's performance are numerically investigated and ranked in order of importance through a sensitivity analysis. In this study, not only is the validity of current design standards in determining the axial load capacity of SRCFST columns examined but a new design formula is also proposed. The proposed confinement model can be employed in numerical procedures for the inelastic simulation of SRCFST columns; the design formula is suitable for use in practical design. [ABSTRACT FROM AUTHOR]

This study introduces a novel concrete-filled tube (CFT) column system featuring a steel tube comprised of four internal triangular units. The incorporation of these internal triangular units serves to reduce the width-thickness ratio of the steel tube and augment the effective confinement area of the infilled concrete. This design enhancement is anticipated to result in improved structural strength and ductility, contributing to enhanced overall performance and sustainability. To assess the effectiveness of the newly proposed column system, a full-scale test was conducted on five square steel tube column specimens subjected to axial compression. Among these specimens, two adhered to the conventional steel tube column design, while the remaining three featured the new CFT columns with internal triangular units. The shape of the CFT column, the presence of infilled concrete and the presence of openings on the ITUs were considered as test parameters. The test results reveal that the ductility of the newly proposed CFT column system exhibited a minimum 30% improvement compared to the conventional CFT column. In addition, the initial stiffness and axial compressive strength of the new system were found to be comparable to those of the conventional CFT column. [ABSTRACT FROM AUTHOR]

• Terrestrial laser scanning of the column of Hera Lacinia Temple and its surroundings. • Polygonal modelling and survey of the column and basement. • CFD analysis of the column, subjected to the main winds in the area. The study presents the results of a multidisciplinary research that integrates terrestrial laser scanning (TLS) and computational fluid dynamics (CFD) to document and analyse an archaeological asset subject to natural hazards. The experimentation was conducted on the surviving column of the temple of Hera Lacinia, located in Capo Colonna near Crotone (Italy). The column, the fragments of the crepidoma and of the foundation constitute the most visible remains of the peripteral Doric temple (second quarter of the 5th century B.C.), belonging to the most important sanctuary of Magna Graecia. The temple, the sanctuary and the other ancient buildings, which are in the area of the Capo Colonna promontory, were destroyed over the centuries to obtain construction material. Today the column and the remains of the temple are located inside the National Archaeological Park of Capo Colonna, protected from human action, but subject to natural phenomena which are dangerous or potentially dangerous in the long term. The wind exerts a constant erosion of the surface of the column and wear of the lower part of the shaft due to the continuous oscillations to which it is subjected; moreover, the wind thrust could add up to a possible seismic action. On the other hand, the geomorphological evolution of the promontory (coastal erosion and subsidence) causes the coastline to recede, and is responsible for landslides affecting the column-basement system. Starting from the point cloud acquired by the TLS, a mesh of the column, basement and surrounding terrain was created, aimed both at documentation, graphic analysis and CFD. The survey enabled the description of the current state of the column-basement system, documenting and measuring the shapes of the column, as well as the different inclinations of the individual parts caused by instability of the ground. Furthermore, the CFD model of the Hera Lacinia column was developed. The model is based on the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with the k-ε closure turbulence model. The oncoming wind was modelled according to the results obtained from 70 years of statistics analysis (from 1950–2021) of wind hourly data (streamwise and spanwise components). The interaction between wind flow and the Hera Lacinia column geometry shows very complex phenomenona. The adopted numerical model was able to simulate correctly the main phenomena involved such as the flow separation occurring around the column as well as the wake behind it. Particular attention was paid to investigating the most damaged areas of the column, identified by analysing recent images of the column, where the values of the time-averaged drag and lift forces were obtained. In order to obtain the erosion-based damage prediction future research will focus on the analysis of air flow erosion of the Hera-Lacinia column, starting from the measurements in situ of the main air characteristics and using the latter as the fluid for the numerical simulation, and by also considering different values of wind speed and directions. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tubular (CFST) columns are frequently used as the main load-bearing components in engineering structures due to their excellent load-bearing capacity. However, the presence of steel tube makes it impossible to accurately detect the damage characteristics of concrete by only relying on traditional mechanical measurement methods. This article quantitatively investigates the concrete damage of circular CFST column during axial compression based on the acoustic emission (AE) technique. Through the cumulative AE parameters including amplitude, count, and energy, the axial compression process of the CFST column can be divided into five main stages (Stage I is divided into two substages) to represent the different damage degree. The damage characteristics of concrete at each stage were explained by combining AE results and mechanical phenomena. A sensitivity analysis of the axial compression process was carried out using the Historic Index (HI) and Severity (Sr) and found that the sudden rise in HI and Sr corresponded to the changes in the different loading stages. The Improved b (Ib) value analysis calculated from the AE amplitudes reflects the evolution mechanism of the crack and can be used for the identification of the final failure moment of the specimen. Finally, a new method for processing and analyzing AE parameters was proposed, which effectively enhanced the dimensionality of real-time monitoring information on the damage of concrete filled in the steel tube. [ABSTRACT FROM AUTHOR]