Fatigue performance of hybrid FRP-concrete-steel double-skin tubular beams incorporating PBL connectors

Experimental study on axial compressive capacity of oil-filled steel pipe

A theoretical model for circular concrete filled steel tubes under compression considering the effect of stress path

Behavior of eccentrically loaded recycled brick aggregate geopolymer concrete-filled corrugated steel tube columns

Bond behavior of ultra-high performance concrete with coarse aggregate filled circular steel tube columns

Lightweight Kolmogorov-Arnold Network with dual-objective optimization for axial capacity prediction of square coal gangue concrete-filled steel tube stub columns based on finite element simulation

Experimental investigation into seismic performance of self-centering rocking piers of concrete-filled steel tubes with bottom encasements

ABSTRACT Tube hydroforming (THF) is widely employed for manufacturing hollow components with complex geometries for automotive and aerospace applications. In the present study, austenitic stainless steel (SS 304) tubes, fabricated by TIG welding of rolled sheets, were hydroformed into bulged geometries using a hydraulic press coupled with a water intensifier system. Tubes of different lengths were deformed under distinct boundary conditions, namely, axial feed and fixed end conditions. The evolution of microstructure and crystallographic texture resulted from hydroforming was systematically characterised using electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) techniques. The influence of deformation on boundary conditions, grain-scale orientation characteristics, texture components, and phase-specific microstructural features were analysed and correlated with the imposed strain paths. The results demonstrate that boundary conditions played a critical role in governing deformation behaviour, strain accommodation mechanisms, and the resultant microstructural and texture evolution in hydroformed austenitic stainless steel tubes.

Concrete-Filled Steel Tube (CFST) columns often encounter challenges such as insufficient compressive capacity, susceptibility to local buckling, and limited ductility. To mitigate these issues, a combined reinforcement approach using Carbon Fiber Reinforced Polymer (CFRP) and Engineered Cementitious Composites (ECC), termed Composite Enhanced Steel-Confined (CESC), is proposed. This paper investigates the axial compressive behavior of CESC through numerical simulation. A refined finite element model is developed and validated against experimental load-displacement curves, failure modes, and ultimate capacities. Based on this validation, a parametric study is conducted to examine the effects of CFRP mesh size, steel tube width-to-thickness ratio, and core concrete strength on the axial compression performance of CESC. Results show that reducing the CFRP mesh size from 40 to 10mm enhances ultimate capacity by 42.1% and effectively suppresses local buckling. Increasing the width-to-thickness ratio from 31.5 to 80.4 improves bearing capacity by 54.1% and the ductility coefficient by approximately 30%. Raising concrete strength from C30 to C70 increases capacity by 48.8%, though ductility improvement remains limited. Furthermore, multiple linear regression is employed to develop a predictive model for bearing capacity, and a modified theoretical formula is proposed for practical design of CESC columns.

ABSTRACT The accurate prediction of the yield strength (Py) of L-shaped and square concrete-filled steel tube (CFST) column frame buckling-restrained steel plate shear walls (BRSPSW) walls are important for safeguarding the structures. In this study, six machine learning (ML) models, including Random Forest (RF), Support Vector regression (SVR), XGBoost, Gaussian Process Regression (GPR), AdaBoost, and Artificial Neural Network (ANN), were employed to predict peak strength of the L-shaped- CFST frame-BR composite using 405 dataset from experimental results. The predictive consistency and robustness of each ML model were evaluated using Error distribution analysis. The RF models demonstrated high prediction accuracy with an R2 -value of 0.9953, the lowest RMSE (11.81kN) and MAPE (1.347), followed by GPR with R2 : 0.9946, RMSE (13.46kN) and MAPE (1.55) at the training phase. However, GPR outperformed others with the highest R2 (0.9601) and lowest RMSE (45.16kN) and MAPE (6.081) in the testing phase, demonstrating superior generalization and predictive reliability. SHAP analysis identified yield stiffness (Ky) as the most influential feature, followed by column Area (Ac) and span length (B). This study provides a robust framework for predicting the yield strength of an L/Squre-section- CFST frame BRSPSW using standalone ML models

ABSTRACT For the elucidation of the shear capacity and energy dissipation characteristics of composite specimens of carbon fiber reinforced polymer (CFRP) and concrete filled steel tubular (CFST), and the clarification of the evolution law of hysteretic behavior of CFRP-CFST specimens under combined compression and shear stress, nine compression and shear specimens were designed and fabricated for systematic tests. The shear-displacement hysteretic curve. According to the test results, the circumferential constraint of the steel tube coupled with the transverse reinforcement of CFRP could effectively complement each other, jointly limit the lateral expansion of concrete, and improve the shear stiffness and ductility of specimens. Hence, the effects of two key parameters, axial compression ratio and transverse restraint coefficient of CFRP, on the specimens’ mechanical properties were further studied. ABAQUS was adopted for simulating the V-Δ curve. Under the dual support of test and simulation, the whole stress process of the component materials is analyzed theoretically, and the stress transfer path and damage evolution law of each material in different stress stages are revealed. In addition, the coupling effects of transverse CFRP layers, yield strength of reinforcement, strength grade of concrete, steel ratio and axial compression ratio on hysteretic behavior of specimens are discussed.

A Comparative Study on Normal- and High-Strength RC Beams with Vertical Openings Strengthened by Steel Tubes: An Experimental Study

Experimental and theoretical study on the flexural mechanical properties of GFRP-wrapped steel tube in marine environments

Numerical investigations on axial compression performance of square coral aggregate concrete-filled duplex stainless steel tube columns

Using deep generative-based machine and ensemble learning framework for predicting ultimate bending capacity of circular steel tubes

• Experimental assessment of punching shear behavior in RC slabs supported by embedded square CFST columns. • Evaluation of multiple strengthening techniques including steel bolts, welded bars, hybrid systems, and prestressing. • Strengthening methods increased punching capacity up to 5.47 times and energy absorption up to 10.49 times. • Strengthened connections exhibited a clear transition from brittle punching to ductile failure modes. • A validated nonlinear finite element model accurately predicts the behavior of strengthened CFST–RC slab connections. The increasing use of concrete-filled steel tube (CFST) columns in modern construction highlights the critical need to understand and enhance punching shear resistance at RC slab-column connections. This study presents an experimental and numerical investigation into the punching shear behavior of square RC slabs supported by embedded square CFST columns, focusing on novel and adapted strengthening techniques. Thirteen RC slab specimens were subjected to concentrated loading from a central embedded CFST column stub. The study systematically evaluated the effectiveness of various strengthening methods, including embedded steel bolts with varying lengths, welded steel bars around the column perimeter, combined bolt and welded bar configurations, and the application of a prestressing system. The experimental results demonstrate that these techniques significantly enhance the punching shear capacity and modify the failure characteristics compared to the control slab. Strengthening methods successfully transitioned the behavior towards more ductile and energy-dissipating modes, characterized by more extensive crack patterns. Quantitatively, the ultimate punching load was increased by up to 5.47 times (achieving 75.53 kN), elastic stiffness by up to 2.24 times, and absorbed energy by a remarkable up to 10.49 times. Complementing the experimental program, a sophisticated finite element model is proposed to simulate the behavior of these strengthened connections. The numerical predictions show excellent correlation with the experimental results.

Quantitative assessment of interfacial debonding in large-span concrete-filled steel tube arch bridges via interpretable deep hybrid learning and ultrasonic inspection

Large-span Concrete-Filled Steel Tube void defect identification with imbalanced datasets using a novel interpretable BO-DRGC framework

Integrated experimental and numerical study with design code comparison for stiffened UHPC-filled steel tube columns under axial compression

Conservative fire resistance design equation for rectangular concrete-filled steel tube columns in accordance with AISC 360­22