Journal of Constructional Steel Research最新文献

Tapered concrete filled double skin tubular (CFDST) member has great potential to be employed in wind turbine structures for catering to the increasing height and output power of wind turbine. However, wind turbine was often subjected to fluctuating wind loads, causing the cyclic lateral force acted on the wind turbine tower. Currently, there is still lack of related research on tapered CFDST under lateral cyclic loading. In this paper, the finite element model (FEM) of tapered CFDST was established and verified by the test results. Detailed failure mechanism of tapered CFDST with various tapered degrees were discussed, and the contributions of sandwiched concrete, inner and outer tubes and the interactions between them were analyzed in detail. It noticed that the failure position of tapered CFDST was not always near the bottom and significantly affected by the tapered degree, which induced an appreciable effect on the hysteretic performance. Subsequently, parametric analyses were performed based on the FEM considering various parameters including slenderness ratio, tapered degree and hollow ratio. Finally, a simplified hysteretic model was proposed. Three-line model was employed to describe the skeleton curve, in which the failure position was properly considered. Typical hysteretic rules were developed to simulate the hysteretic shape of tapered CFDST under various stages. The accuracy of the proposed model was validated by the numerical results. The analytical results in this paper provide a reasonable method to predict the hysteretic performance of tapered CFDST in wind turbine structures.

The presented research aims to develop global and local buckling reduction factors that account for the impact of amplified geometrical imperfections and the variability of residual stresses on the buckling resistance. The improved buckling coefficients might be necessary for analysing existing structures, which often have larger imperfections than the manufacturing tolerances. Advanced GMNI analyses are employed to investigate pure local and global buckling resistances of I- and box-section columns, incorporating accurate non-amplified local and global imperfections. A parametric study is conducted to systematically investigate the impact of enlarging the imperfection factors and varying residual stresses. The local and global buckling formulas specified in EN1993-1-5 and EN1993-1-1 are calibrated against laboratory test results and/or GMNI analyses to account for the influence of imperfections and residual stresses. Similar calibration process is performed within the current study by modifying the imperfection factor $\alpha$ in the buckling formulas taking into account the enlarged imperfection magnitude. The result of the current study enables designers to refine the estimation of the buckling capacity when actual imperfections and residual stresses deviate from those employed during the design phase.

This study performed an indoor experiment to examine the failure mechanism of a catenary CFST truss arch under a mid-span single-point load. A parametric analysis of a finite element model, validated with literature and experimental data, was conducted, taking into account material strength, rise-span ratio, arch axis coefficient, and steel ratio. A new buckling strength verification formula is proposed, which integrates stability coefficients for pre-buckling deformation and the rise-span ratio, as well as correction coefficients for varying bending moments and axial forces. The results indicate that in-plane failure modes in CFST truss arches typically initiate with the yielding of the web members before the chord tubes, contrasting with truss column failures. The buckling strength showed a direct correlation with material strength, rise-span ratio, and steel ratio, though with diminishing returns. The rise-span ratio and arch axial coefficient had minimal impact. The proposed verification formula, which includes pre-buckling deformation, arch axis coefficient, and the rise-span ratio, provides a precise and conservative method for evaluating the in-plane buckling strength of catenary CFST arches, enhancing engineering design practices.

This paper presents the experimental and numerical analysis of an innovative plate girder geometry with variable web thicknesses. An idea proposed in this research is to increase the stability of the girder web by increasing its thickness in the compressed zone. This solution can replace commonly used longitudinal stiffeners which are designed to prevent web local loss of stability. Moreover, such an innovative approach requires only one additional butt weld along the entire element, which is technologically a simpler, cheaper and faster operation (due to the possibility of full automation of production) compared to manual welding of individual stiffeners. The experimental and numerical study shows that application of a web with variable thickness in I-shaped plate girder geometry subjected to four-point bending results in a change in failure mechanism from local to global one. Moreover plate girders with single and double-sided longitudinal stiffeners have been tested numerically. The result of the study clearly shows that values of ultimate load estimated for plate girders with longitudinal stiffeners were smaller than those obtained for innovative ones. It confirms that the proposed solution may prevent web from local stability loss and increase plate girder stability due to bending. This innovative method can be also considered as an effective procedure of strengthening the web in its compressive zone compared to commonly used longitudinal stiffeners.

Crack initiation and propagation behaviors are the dominant characteristics of ductile fracture for structural steels. This study aims to predict the strength degradation of steel connections caused by ductile crack and the effect of element size in FE simulation. Tensile fracture tests were conducted on notched specimens to study the crack behavior of structural steel. An improved micromechanics-based fracture model which considers crack initiation and propagation was proposed, and the parameters involved in the model were calibrated. The micro void growth and coalescence inside the material were numerically investigated using the void-cell model. The fracture process of bolted connections under tension was studied with the aid of the proposed model. Results show that a higher stress triaxiality leads to an increase in the yield and ultimate strengths. The proposed fracture model is applicable to different element sizes of numerical models, and its effectiveness was verified by the experimental results. Stress triaxiality has a great influence on the micro void grow rate, and the void grows faster at a higher stress triaxiality state. The ductile fracture process of bolted connections can be predicted very well using the proposed model. For the multi-bolt connection, the load carrying capacity decreases as the load angle increases.

A novel steel beam-column joint with a replaceable bio-inspired hinge (RBHJ) was developed to simplify the prefabricated beam-column joint structure in this paper. The replaceable bio-inspired hinge (RBH) consists of a connection system providing rotational capacity and an energy dissipation system offering flexural capacity. To evaluate the seismic performance and repairability, three RBHJ specimens were designed to conduct the three hysteretic and three remediation experiments. The influence parameters (whether to add rubber, the diameters of the curved panels, and the thicknesses of the energy dissipation plates) on the RBHJ performance in terms of failure process and modes, hysteretic and skeleton curves, ductility coefficient, and energy dissipation behavior were explored. It was found that the RBHJ damages emerged at the weakening location of the energy dissipation plates, and there was no visible deformation observed in other components. The RBHJ specimen still exhibited a stable hysteresis curve after three repeated repairs. The hysteresis curve of RBHJ exhibited a complete shuttle-like form, with its peak viscous damping ratio attaining 38.14 %. The maximum interlayer displacement angle of the RBHJ reached 8.70 %, and the ductility coefficient of all specimens exceeded 3 except for the specimen D270-T10-W30-R. Based on the working mechanism and mechanical model, a corresponding formula for calculating the yield flexural bearing capacity of the RBH was derived.

This paper represents a comprehensive numerical analysis of a reusable column base connection previously proposed by the authors. The energy dissipator utilised in the proposed connection was investigated from the aspect of the design procedure, experimental study, and numerical simulation. The test specimens were designed following the design procedure and served as a reference for comparison with the finite element (FE) models in ABAQUS. The findings indicate that the energy dissipator behaves in accordance with expectations, affirming the feasibility of the modelling approach. To investigate the impact of key design parameters on the global and local behaviours of the proposed connection, an advanced FE model was developed and sufficiently validated against the experimental data from prior research by the authors. Three sets of FE models were constructed corresponding to three design parameters, including the global slenderness of the reduced section, the strength factor, as well as the deflection angle of the dissipative plate. The parametric study focuses on the energy dissipation capacity and reusability. The outcomes contribute to a deeper comprehension of the assumptions and constraints of the design process, offering practical suggestions to enhance the seismic performance of the proposed connection.

In this paper, the design calculations of axially loaded CFST slender columns with latticed annular steel parts (SRCFST) are proposed based on the separated model. Finite Element (FE) analysis is conducted to predict the axial compressive performance of circular CFST slender columns with latticed annular steel parts. The test data are used to validate the FE model and to assess the suitability of design guidelines given in AISC 360–10, Eurocode 4, and DL/T 5629–2021. The validated FE model extensively analyzes the composite interaction between the concrete and the latticed annular steel parts as well as investigates the effect of different configurations of the latticed annular steel on compression performance. The influence of various parameters, including the constraint coefficient (ξ), steel reinforcement ratio (ρ), and slenderness ratio (λ), on the lateral confinement stress and ultimate bearing capacity of the latticed annular steel parts were assessed and quantified. Additionally, using the results of numerical simulations performed in this study, design procedures were proposed by modifying the separation model. The predictions from proposed design rules have demonstrated good agreement with the strengths of test and numerical specimens.

Under the influence of random loads such as those from vehicles, the welded details in steel bridges tend to gradually develop into macrocracks, typically originating from manufacturing defects or stress concentration points. As the service life of the steel bridge increases, the continuous generation and propagation of fatigue cracks lead to a decline in the bridge's service performance, potentially resulting in catastrophic failures such as bridge collapse. Accurately analyzing the fatigue crack growth patterns at welded joints is a prerequisite for reliably assessing the structural service performance. The analysis of fatigue crack propagation depends on both the crack growth step size and the cyclic stress–strain response at the welded joint under loading. Considering the complexity of the material properties and stress concentration at the welded joint, which leads to a lack of analytical solutions for the cyclic stress–strain characteristics at the crack tip, numerical analysis was employed to obtain the cyclic stress–strain response at the crack tip of the welded joints. Using the size of the cyclic plastic zone at the crack tip as an adaptive crack growth step size, a model for fatigue crack growth was developed based on the plastic strain energy of the cyclic plastic zone. Fatigue test specimens extracted from the welded toe of cruciform welded joints were tested, providing cyclic stress–strain (Ramberg-Osgood material parameters) and fatigue damage characteristics (Manson-Coffin material parameters) of the material at the welded toe. High-cycle fatigue tests using cruciform welded joint specimens determined a good correlation between the crack propagation characteristic dimensions obtained from the adaptive numerical analysis model and the experimental results. The experimental findings confirmed the applicability of the established adaptive numerical analysis model for studying fatigue crack growth in cruciform welded joints. The parameters introduced in this model are physically meaningful, easy to obtain, and suitable for engineering applications.

In this study, an analytical model was developed and predictive equations were proposed to estimate the maximum temperature of steel bridges in the event of a fire originating from complex facilities beneath the bridge. Based on statistical data, a representative shape of steel bridges in South Korea was selected. A representative Heat Release Rate (HRR) curve for the complex facility was selected, and a parametric study was conducted, including variables such as Heat Release Rate Per Unit Area (HRRPUA), fully developed time, vertical clearance, and the area of the complex facility. Through correlation analysis, key parameters influencing the maximum temperature in steel bridges were examined. Based on the results, both linear and non-linear temperature prediction equations were suggested. The non-linear equation demonstrated higher predictive performance than the linear equation. This study provides foundational data for enhancing the accuracy of fire analysis methods and temperature prediction models for steel bridges.