Design Of Columns Research Articles

Predicting axial compression capacity of CFDST columns and design optimization using advanced machine learning techniques

Concrete-filled double-skin steel tubular (CFDST) columns are fundamental in civil engineering, known for their exceptional mechanical properties. Their load-bearing capacity, influenced by factors such as geometry, material properties, and loading conditions, is a critical aspect of CFDST column design. This study introduces an innovative approach that leverages the synergy between gradient-boosting regression (GBR) and three metaheuristic optimization algorithms: sine-cosine-based swarm optimization (SCSO), grey wolf optimization combined with whale optimization (GWO_WOA), and artificial rabbits optimization (ARO). Its primary aim is to accurately predict the axial compression capacity (ACC) of CFDST columns for optimal design. Using a comprehensive database of 153 empirical results from CFDST columns subjected to axial loads, the proposed model is rigorously compared with eight alternative machine learning models, three established design standards, and two empirical equations to validate its robustness. The results highlight the superiority of the finely tuned GBR model, optimized with the ARO algorithm, over peer models and conventional benchmarks. This framework also serves as the foundation for optimizing the CFDST column design by identifying the optimal dimensions that maximize ACC while meeting the design constraints. Clearly, this model can significantly improve CFDST column design, thereby benefiting structural engineers and designers striving to enhance the safety and efficiency of CFDST structures.

Numerical analysis of high-strength centrifugal precast RC hollow pipe columns using grouted corrugated duct connection: Confinement effect and ductility evaluation

High-strength centrifugal precast (HSCP) reinforced concrete (RC) hollow pipe columns using grouted corrugated duct connection (GCDC) is a novel structure form in accelerated bridge construction (ABC). Nevertheless, the confinement effect of the HSCP hollow column core concrete provided by single-layer transverse rebar and its impact on ductility is not clear. Therefore, in this paper, the confinement effect and the ductility of hollow columns is studied using finite element analysis (FEA) method. A modified model is established to evaluate the constitutive relation of the core concrete confined by single layer transverse rebar. Based on the modified model, a simplified fiber model for predicting the hysteric response of HSCP hollow pipe column using GCDC, which considers bond-slip effect in GCDC joint was developed. The results indicate that the confinement effect of HSCP hollow pipe column is sensitive to the wall thickness ratio. When the wall thickness ratio decreases, the ultimate strain of the core concrete significantly decreases, while the effect on strength is not significant. The simplified model which considers confinement effect is more accurate in predicting the ductility of HSCP hollow columns. It proves that the weak confinement effects can lead to early cracking of the inner wall of hollow columns, which leads a significant impact on the ductility of HSCP hollow columns. Based on the parametric analysis, the peak load of the hollow column increases by 16.7% when the wall thickness ratio rises from 0.1 to 0.2, but only slightly changes when the wall thickness ratio is increased beyond 0.2. The wall thickness ratio of HSCP hollow pipe columns should be set above 0.2 to ensure the strength and ductility. In addition, a ductility evaluation method and a design example were developed to guide preliminary ductile design of HSCP hollow columns.

Investigating the fire resistance of corrugated steel columns

This research paper focuses on investigating the fire resistance of axially restrained Corrugated Plate Steel columns (CRG) exposed to hydrocarbon fire conditions. Key parameters, including corrugation depth, plate thickness, axial load percentage, and column length, were analyzed to assess their impact on the fire resistance performance of CRG columns. A comprehensive analysis involving 80 finite element (FE) models was conducted using ABAQUS software. The analysis process encompassed studying temperature distribution within the columns, observing buckling modes, and determining the durations of buckling and failure fire resistance. The adopted FE model has been verified by comparing it to experimental data presented in the relevant literature. Findings reveal that corrugated CRG columns exhibit superior resistance to buckling and structural failure compared to circular cross-section columns. Corrugation depth minimally affects fire resistance but influences axial deformation and generated axial force due to increased structural stiffness. Increasing plate thickness improves fire resistance, particularly at lower axial load levels, while increasing axial load percentage decreases fire resistance. Doubling the column length has no significant effect on fire resistance, but columns with smaller plate thicknesses exhibit lower resistance under high axial load conditions. These insights inform the design and construction of CRG columns in structures exposed to hydrocarbon fire risks, aiding in enhancing fire safety and performance.

Testing and design of cold-formed high strength steel square hollow section columns

An experimental and numerical investigation into the flexural buckling behaviour of cold-formed (CF) high-strength steel (HSS) square hollow section (SHS) members is reported in this paper. A series of 12 flexural buckling tests were conducted on S700 and S900 CF SHS columns. Finite element (FE) models were developed to simulate the experimental observations, which were utilized in a parametric study encompassing a broader range of steel grades and specimen geometries. Subsequently, the current buckling curves in European, North American, and Australian codes was evaluated through reliability analyses. Meanwhile, the effective width method (EWM) and the modified generalized slenderness-based resistance method (GRSM) were compared for slender cross-sections. According to the results of reliability analyses, the modified buckling curves were proposed for CF HSS SHS columns.

Bracing requirements and design for a single column considering semi-rigid connections and initial curvature

The use of bracing has been widely recognized as an effective technique to increase the strength of columns by reducing their effective length. This paper presents an assessment of the bracing requirements for a semi-rigidly connected column, which is laterally braced at the mid-height. By utilizing the proposed half-length column model, the effects of column stiffness and initial curvature on the brace strength and stiffness requirements are investigated. The results indicate that the column’s initial curvature coefficient increases with a higher applied load, but decreases with increased column end connection stiffness. The required brace stiffness requirement stipulated in AISC 360-22 should be increased when considering the effect of column’s initial curvature. Following the design concepts of AISC 360-22 and CSA S16-19, equations for assessing the bracing requirements for a semi-rigidly connected column are proposed. These equations are validated against the finite element analysis results, demonstrating their ability to accurately assess the bracing requirements for semi-rigidly connected columns. These equations can be adopted in current engineering practice.

Effect of Eccentricity of Connection on Design of RC Columns

Effect of Eccentricity of Connection on Design of RC Columns

Data-driven prediction and optimization of axial compressive strength for FRP-reinforced CFST columns using synthetic data augmentation

Fiber-reinforced polymer (FRP) sheets can be used as additional confinement to improve the load-bearing capacity and durability of concrete-filled steel tubular (CFST) columns. This study presents a data-driven approach aimed at accurately predicting the strength and optimizing the design of FRP-CFST columns under axial compressive loading. To overcome the limited database size (only 287 samples), a synthetic data augmentation technique was developed with recourse to the tabular generative adversarial networks (TGAN). Four machine learning (ML) models were rigorously trained using two distinct schemes “Trained with synthetic - Tested with real” (TSTR) and “Trained with real - Tested with real” (TRTR) to seek out the best strength prediction model. Then the winner model was integrated with the metaheuristic optimization algorithm—nondominated sorting genetic algorithm II (NSGA-II), to optimize both the axial strength and material cost of FRP-CFST columns. This fusion enabled a dual-objective optimization via generating the Pareto front, providing designers with a spectrum of optimal design solutions. It turned out that the categorical gradient boosting model trained with the TSTR mode (CATB-Syn) showed superior performance than the other ML models. Its accuracy also surpassed that of existing design equations. The combination of CATB-Syn with NSGA-II provided a reliable Pareto front, and the interpretability of CATB-Syn was also verified. Thus, the proposed framework opens a new avenue for the efficient design of such double-jacketed columns.

Estimation and analysis of the cumulative energy damage model for precast concrete nonrectangular column frame structures

A detailed characterization of structural damage progress is essential to performance-based seismic design for precast concrete nonrectangular column (PCNC) frame structures. The paper presents an experimental investigation into the damage behavior of the PCNC frame structures under reverse cyclic loading, including specimens PCFS1 and PCFS2 in bay and specimen PCFS3 in depth of a new precast residential building. Based on the experimental results, the damage mechanism of the PCNC frame structures was further discussed with the cumulative energy damage model proposed in this paper, and the influence of key structural parameters on the damage of the PCNC frame structures was examined, including energy dissipation adjusted factor, the residual deformation rate and the stiffness degradation rate. Available results indicated that the experimental damage curves of test specimens increased with the loading progress and acted with nonlinear damage characteristics, and PCNC frame structural damage behavior was sensitive to the axial compression ratio. For the proposed damage model, the calculation results were in good agreement with the experimental results. On the basis, the damage degree of the PCNC frame structures was divided into five performance levels including normal use, temporary use, use after repair, life safety and prevent collapse in the defined damage range of (0, 1). Elastic layer drift ratio limit was suggested to relax for PCNC frame structures. Final test results could provide a basis for the aseismic design and damage assessment of such structures after earthquake.

Strength prediction and stochastic analysis of ultra-high performance concrete columns under the explosive blast load

The performance research based on numerical and experimental studies on ultra-high performance concrete (UHPC) generally considers it as an isotropic material, which is obviously different from what it really is in practical engineering. A database of UHPC compressive strength was investigated, having the same UHPC mix proportion as the field blast experiment, to show how the strength of UHPC varies in compression. It is found that Weibull distribution is the best fit of its probability model. A combination of Monte-Carlo and Finite Element method is used, adopting the available UHPC compressive strength, to reproduce the field blast test on UHPC columns. Both the non-spatial and spatial variability of material properties of the UHPC columns are under consideration to conduct the UHPC column strength prediction under blast loads. The residual loading capacity, damage index and failure mode of UHPC columns with different sizes damaged by different explosion severities are obtained by non-spatial simulation and spatial simulation respectively. It can be concluded that compared with the non-spatial model, the numerical simulation results of the spatial model are closer to the experimental situation. Therefore, inclusion of spatial variability is recommended for reliability-based blast-resistant design for UHPC column.

Snow Geese Algorithm: A novel migration-inspired meta-heuristic algorithm for constrained engineering optimization problems

This paper proposes a novel nature-inspired meta-heuristic algorithm, named Snow Geese Algorithm. It is inspired by the migratory behavior of snow geese and emulates the distinctive “Herringbone” and “Straight Line” shaped flight patterns observed during their migration. The algorithm is structured into three main phases for benchmark testing. In the first phase, the Snow Geese Algorithm's numerical results are compared with those of several classical meta-heuristic algorithms using the same test functions and original data from these algorithms. In the second phase, in order to minimize potential variations during the comparison, all algorithms undergo evaluation on a standardized testing platform. In the third phase, this paper applies the Snow Geese Algorithm to solve four widely recognized engineering optimization problems: the tubular column design, piston lever optimization design, reinforced concrete beam design and car side impact design. These real-world engineering problems serve as test cases to assess Snow Geese Algorithm problem-solving capabilities. The primary objective of the Snow Geese Algorithm is to provide an alternative perspective for tackling complex optimization problems. Please note that the complete source code for the Snow Geese Algorithm is publicly available at https://github.com/stones3421/SGA-project.

Local–flexural interactive buckling behaviour and design of press-braked stainless steel slender Z-section columns

The present paper reports an experimental and numerical study on the local–flexural interactive buckling behaviour and resistances of press-braked stainless steel slender Z-section columns. A testing programme adopted two press-braked stainless steel slender Z-sections and included material testing, initial geometric imperfection measurements and twelve fixed-ended column tests, with the experimental setups, procedures and results fully reported. The testing programme was accompanied by a numerical modelling programme, with finite element models developed and validated against the fixed-ended column test results; upon validation, parametric studies were conducted to generate additional numerical data over a wide range of cross-section dimensions and member lengths. The obtained test and numerical data were adopted to evaluate the relevant design rules for press-braked stainless steel slender Z-section columns susceptible to local–flexural interactive buckling, as set out in the American specification and European code. It was revealed from the evaluation results that the American specification led to accurate interactive buckling resistance predictions, while the European code resulted in relatively conservative interactive buckling resistance predictions. Finally, a revised Eurocode design approach was developed and provided more accurate and consistent interactive buckling resistance predictions for press-braked stainless steel slender Z-section columns than its original counterpart.

Design and operation of a packed pilot scale distillation column for tire pyrolysis oil: Towards the recovery of value-added raw materials

This work describes the key features involved in the design and operation of a pilot scale distillation column for the recovery of value-added products from tire pyrolysis oil (TPO), as part of the BLACKCYCLE project. The distillation unit was designed using engineering heuristic rules, simulated distillation (SimDist) data and Aspen Hysys ® modeling. The distillation plant consists of a packed column with a nominal throughput of 20 kg/h, and is classified at the fifth technology readiness level (TRL-5). The commissioning and results of long-term experimental campaigns for validation purposes are also presented. In this way, important information is gathered for the design of larger plants. The distillation unit was tested and validated using TPO produced from a pilot scale continuous single-auger pyrolysis plant. A first distillation was performed yielding a heavy fraction (HF-1) with properties suitable for carbon black production, while the light fraction (LF-1) includes the presence of value-added chemicals such as benzene, toluene, ethylbenzene and xylenes (BTEX) and limonene. The LF-1 was also used for a second distillation, producing a stream high in limonene at the bottom (HF-2), and another one high in BTEX compounds at the top (LF-2), which are valuable raw materials for polymer production and petrochemicals, respectively. The key results obtained here are expected to provide an outstanding impetus for the circular economy of complex streams such as end-of-life tires (ELTs) by combining pyrolysis and distillation technologies.

Global buckling investigation of T-shaped built-up columns composed of two hot-rolled H-shapes

Hot-rolled H-forms are used sparingly in the building industry in China, and there is a vast supply of these shapes. In Chinese academic circles, the utilization ratio of hot-rolled H-shapes has been proposed as one of the criteria for evaluating high-performance steel structures. Academics in China have proposed a built-up column comprising structural T-shapes and hot-rolled H-shapes. However, the market's low output of structural T-shapes limits the technological applications of this built-up column. This study proposes a new T-shaped built-up columns column (NTBC) design in which the columns are connected using two hot-rolled H-shapes. Based on the test, the global buckling of the NTBC is numerically evaluated under an axial compression load, and the findings are compared with the present national design specifications in line with the comprehensive defects suggested by the Chinese design standard GB 50017. The global buckling mode of NTBCs is identical to that of the classic welded T-shaped column, according to a comparison of 72 specimens of Q345 and Q460 steel. Local buckling is not evident. Finally, through data comparison and reliability analysis, compression column curves that can be used for the global buckling design of NTBCs were recommended in the GB50017 and EN1993-1-1, respectively.

Economic comparison of reactive distillation (RD) to a benchmark conventional flowsheet: Regions of RD applicability and trends in column design

A novel methodology for the techno-economic assessment of Reactive Distillation (RD) is presented. The developed methodology benchmarks reactive distillation (RD) to a conventional reactor + distillation train flowsheet (R+D) on a cost-optimized basis, with the optimization being performed on the process unit level (reactor sizing, number of stages, feed point(s)) and the internals level (reactive tray design). This methodology is applied to the ideal quaternary system A+B↔C+D with the conventional boiling point order of TC < TA < TB < TD (αAD = 4, αBD = 2, αCD = 8). From this pool of data, a regime map of RD vs. R+D is established in which the attractive regions of either flowsheet option are identified in terms of the chemical reaction rate and chemical equilibrium. It is found that RD can arise as the cost optimal option for a large range of residence time requirements by virtue of overcoming the external recycle requirements of R+D. This is achieved through optimized reactive tray design. Contrary to conventional distillation design practices, it was found that the preferred use of bubble-cap trays over sieve trays to allow elevated weir heights and designing the column diameter below 80% of flooding become relevant design choices when accommodating high liquid holdup.

Liquid-Liquid Equilibria for Ternary Systems Citronellal + Ethanol + Water and Citronellol + Ethanol + Water at 303.15 and 323.15 K

The liquid-liquid equilibria (LLE) for the ternary systems citronellal + ethanol + water and citronellol + ethanol + water are reported. The LLE of the systems have been measured at 303.15 and 323.15 K under atmospheric pressure as a reference for citronella oil production using solvent extraction method. The experimental data obtained were correlated using NRTL and UNIQUAC equations. The non-randomness parameter (αij) of the NRTL model is 0.2-0.47 and fits the experimental data satisfactorily. Both the NRTL and UNIQUAC models gave relatively good results for the systems investigated with the average Root Mean Square Deviation (RMSD) are 0.92% and 0.85% respectively. Based on the ternary diagram obtained in this work, it was found that the system followed the type I classification by Treybal [19]. The binary interaction parameters generated in this study can also be used for LLE calculation in the design of extraction columns.

Reliability of Rack Columns Designed by the Direct Strength Method

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 ϕ = 0.85 does not meet the safety requirements.

Methodology of load effect analysis and ultimate limit state design of semi-submersible hulls of floating wind turbines: With a focus on floater column design

A main challenge in the design of hull structures of floating wind turbines (FWTs) is to properly estimate the load effects and resistance to perform the safety design check. While great efforts have been devoted to the load effects in terms of global motions, there is a lack of effective methods to calculate internal loads and lateral pressures of hulls in a fully coupled aero-hydro-servo-elastic environment, which should serve as the basis for the assessment of load effects in hulls. Moreover, very limited knowledge and experience exist in the current guidelines and research publications to deal with the detailed design of hull structures of FWTs. This study outlines an effective methodology and procedure to determine load effects for structural design of semi-submersible hulls, and demonstrates their application in a case study of column design based on the ultimate limit state (ULS) criteria. First, a novel multi-body floater model is established in a fully coupled FWT numerical system, which is capable of calculating floater internal loads. Second, the environmental contour approach is employed to initially choose load cases for ULS design, based on important wind speed conditions and criterial wave periods. Next, a screening of the critical load cases is made based on Von Mises stress analysis of columns considering global loads. Then, lateral pressure on columns is calculated, and a detailed design check is made based on combined global loads and lateral pressure as well as relevant safety factors for loads and resistance. Furthermore, the relative influence of global loads and lateral pressure on ULS performance of columns is investigated, which serves as the basis to reset the critical load cases for ULS design check. Subsequently, sensitivity analysis of ULS performance with respect to column design parameters, extreme value estimation, and shell buckling design checks, are performed to determine the plate thickness and ring stiffener distances of central and outer columns. Finally, optimized ring stiffener dimensions are estimated for different design cases based on panel buckling design criteria, and detailed design parameters for the central and outer columns are obtained. The methodology and procedure established and applied in a case study in this work, contribute to improving engineering practice and establishing improved design standards.

An improved constitutive model for steel tube-confined ultra-high-strength concrete

This study aims to accurately simulate the compressive behavior of ultra-high-strength concrete (UHSC) under various confinement conditions through conventional triaxial and equi-biaxial compressive tests. The triaxial compressive tests revealed that the stress and dilation angle of the concrete varies with changes in axial plastic strain and confining pressure, which is not well-considered in existing mechanical models for UHSC material. To address this limitation, an improved constitutive model based on the concrete plastic damage (CDP) model is proposed in this paper. The improved model incorporates the confining pressure in the flow rule and the hardening/softening rule, in addition to the axial plastic strain. The tensile and compressive meridians of the yield surface are calibrated based on the triaxial and biaxial compressive test results. Furthermore, the study proposes formulas for expressing the stress–strain relation and the lateral-to-axial plastic strain relation of UHSC under different confining pressures. These formulas help generate the hardening/softening rule and the dilation angle evolution of the flow rule, respectively. To verify the proposed constitutive model, the study simulated tests on UHSC-filled steel tube (UHSCFST) stub columns under compression using the finite element method. The simulated results of the peak bearing capacity of the tested UHSCFST stub column specimens are satisfactory, and the interaction between the steel tube and the concrete is reasonably predicted. The proposed improved constitutive model has the potential to accurately simulate the compressive behavior of UHSC under different confinement conditions, which can aid in the design of composite columns made with UHSC materials.

Enhancing Techno Economic Efficiency of FTC Distillation Using Cloud-Based Stochastic Algorithm

A liquefied petroleum gas plant facility (LPGPF) is a series of binary distillation columns used to separate natural gas into four alkanes: ethane, propane, butane, and pentane. The conventional distillation column design consists of three binary distillation columns and six heat exchangers to perform the process. Each heat exchanger consumes immense energy to heat up the reboiler and condense the distillate. There are several process technologies that can minimize distillation column energy consumption. In this research, a fully thermally coupled distillation column (FTCDC) was proposed to minimize energy consumption by reducing the number of heat exchangers and tray columns. An FTCDC has the capability to reduce capital expenditure, operational expenditure, and total annual cost (TAC). The complexity of the FTCDC arises from its process integration. In each column, the intersection composition depends on complex mass and energy balances at the column inlet and outlet and each tray. Process integration, including material recycling and heat recovery, increases the complexity significantly. Moreover, the decision variables are multi-intersection composition for each column to achieve optimum objective function, increasing the number and complexity of the computational load such that effective stochastic optimization algorithms are required. The proposed method was designed using a rigorous vapor liquid equilibrium (VLE) FTCDC model and incorporated with recent stochastic optimization algorithms, such as a genetic algorithm, particle swarm optimization (PSO), an imperialist competitive algorithm, and a duelist algorithm, to determine hydrocarbon composition in the FTCDC intersection. To increase the efficiency and effectiveness of the FTCDC optimization design, cloud computing was utilized. The result was compared with conventional methods such as Fenske-Underwood-Gilliland, a Fenske-Underwood-Gilliland modification, and VLE. The optimization objective function is to minimize TAC with hydrocarbon composition in the FTCDC intersection as decision variables. The optimization using the VLE-PSO method reduces TAC up to 26.28%. All designs were validated using a rigorous model with Aspen HYSYS commercial software. This study's primary goal is to improve the performance of FTCDCs using stochastic algorithms and cloud-based computing capacity. The large amount of computation is handled by cloud-based computing resources, enabling reliability and durability.

Behavior of longitudinal-seam steel tubular columns with crack defect in weld

An experimental investigation was conducted to investigate the axial compressive behavior of square longitudinal-seam steel tubular (LSST) stub columns with artificial crack defect in weld. The axial compression tests were carried out on 108 square LSST stub columns with crack defect and 3 square LSST columns without crack defect as control groups. The effect of design parameters such as thickness of tube, length and width of crack defect, location of crack defect on axial compressive behavior of square LSST columns were analyzed. Test results involved failure modes, load-displacement behavior, ultimate strength, initial stiffness, and ductility coefficient of all specimens were presented. The corresponding FE models of square LSST columns with crack defect are established and validated by comparison with experimental results. Test results have demonstrated that crack defect often led to stress concentration, causing significantly higher strain intensity at the position of crack defect compared to other areas. Square LSST columns with crack defect exhibited a 26% lower ultimate strength at T = 2.5 mm. The ductility coefficient enhanced with the decrease of length and width of crack defect. However, the location of crack defect had limited effect on axial behavior of LSST columns. In addition, parametric formulae of ultimate strength for square LSST columns with crack defect are proposed, which achieved high accuracy. The research results could provide evaluation reference in design and construction of LSST column.