• Steel and Composite Structures
• /
• v.51 no.6
• /
• pp.697-712
• /
• 2024

In this paper, the dynamic flexural stiffness of concrete-filled steel tubular (CFST) members is investigated based on vibration modal testing and a Bayesian model updating procedure. To reflect the actual service states of CFST members, a 3-stage modal testing procedure is developed for 6 circular CFST beam-columns, in which the modal parameters of the specimens under varying axial load levels are extracted. In the model updating procedure, a Timoshenko beam element model is first established, in which the influence of shear deformation and rotational inertia are incorporated. Subsequently, a 2-round Bayesian model updating strategy is proposed to calculate the dynamic flexural stiffness of the specimens, which could effectively consider the influence of physical constraints in the updating process and achieve reasonably well results. Analysis of the updating results shows that with the increase of the axial load level, degradation of the flexural stiffness is significantly influenced by the load eccentricity. It shows that the cracking of the core concrete is the primary reason for the flexural stiffness degradation of CFST beam-columns. Finally, based on comparison with equations proposed by several design standards, the calculation methods for the dynamic flexural stiffness of CFST members is recommended.

• Journal of Korean Society of Steel Construction
• /
• v.17 no.2 s.75
• /
• pp.139-149
• /
• 2005

Post-local buckling behavior is a very important consideration in plastic and seismic design of steel structures. It describes the structural behavior up to the final collapse state. In order to assess the actual reliability of structures under severe repeated loading, such as strong earthquakes, it is necessary to evaluate the progressive cyclic deterioration of stiffness as well as the strength and energy dissipation capacity of the structures after local buckling happens. In this study, a simple analytical model developed for predicting post-local buckling behavior for cyclic and non-proportional loading histories, has been proposed. This analytical model uses the stress resultant model based on the two surface model. Analytical moment-curvature relationship using this model compare well with the experimental results in constant amplitude cycling, and linearized energy deterioration which is very important in seismic design can be predicted from the proposed model.

• Computers and Concrete
• /
• v.25 no.5
• /
• pp.383-400
• /
• 2020

Due to higher stiffness to weight, higher corrosion resistance, higher strength to weight ratios and good durability, concrete composite structures provide many advantages as compared with conventional materials. Thus, they have wide applications in the field of concrete construction. This research focuses on the structural behavior of steel-tube CFRP confined concrete (STCCC) columns under axial concentric loading. A nonlinear finite element analysis (NLFEA) model of STCCC columns was simulated using ABAQUS which was then, calibrated for different material and geometric models of concrete, steel tube and CFRP material using the experimental results from the literature. The comparative study of the NLFEA predictions and the experimental results indicated that the proposed constitutive NLFEA model can accurately predict the structural performance of STCCC columns. After the calibration of NLFEA model, an extensive parametric study was performed to examine the effects of different critical parameters of composite columns such as; (i) unconfined concrete strength, (ii) number of CFRP layers, (iii) thickness of steel tube and (iv) concrete core diameter, on the axial load capacity. Furthermore, a large database of axial strength of 700 confined concrete compression members was developed from the previous researches to give an analytical model that predicts the ultimate axial strength of composite columns accurately. The comparison of the predictions of the proposed analytical model was done with the predictions of 216 NLFEA models from the parametric study. A close agreement was represented by the predictions of the proposed constitutive NLFEA model and the analytical model.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.22 no.4
• /
• pp.363-370
• /
• 2009

We simulated large deformation and inelastic behavior of API-X80 steel linepipes using nonlinear finite element method. Gurson-Tvergaard-Needleman(GTN) model is employed for the development of the constitutive model of the steel. The GTN model is implemented in the form of the user-supplied material subroutine(UMAT) for the commercial software of ABAQUS. To calibrate the model parameters, we simulated the behavior of the uniaxial tension test using ABAQUS equipped with the developed GTN model. Using the set of the model parameters, we were able to capture the characteristics of the plastic buckling of API-X80 steel linepipes.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.21 no.3
• /
• pp.253-263
• /
• 2008

Extension of IFC data model for steel bridge members is proposed to represent detailed design information. First of all, the design data items and their representation method are classified by analyzing primary references such as design specification, structural calculation documents and shop drawings. Some of the classified items are enough to be represented by the existing IFC model. However, the need of additional model is noted to systematically represent the design information for other items such as stiffener, diaphragm, joint system, and shear connector. An inheritance relations and properties for added model are also defined. The application program based on the proposed data model is developed. In the end, by loading the application program on the AutoCAD 2002 program, end-users can input the design information of steel bridge members. The applicability and efficiency of the proposed data model and the program are verified by checking the section area, intervals, and interferences.

• Journal of Korean Society of Steel Construction
• /
• v.20 no.2
• /
• pp.313-321
• /
• 2008

Recently in Japan, fracturing was observed on the diagonal member of a through truss bridge at the boundary region with the concrete slab. Local corrosion damage where the diagonal member was enclosed in the concrete slab is an important factor in the fracture. In this study, accelerated exposure tests were carried out on concrete-steel model specimens simulating steel members at the boundary with concrete. Fatigue tests were then performed on the corroded model specimens. Accelerated exposure tests of the S6-cycle, which is carried out on the model specimens for 150, 300, 450 and 600 da ys. Their surface geometry was then measured. From the accelerated exposure test results, change in maximum and mean corrosion depths was determined according to the testing periods. The effect of local corrosion on fatigue strength was also presented based on the fatigue test results.

• Steel and Composite Structures
• /
• v.35 no.3
• /
• pp.415-437
• /
• 2020

Circular concrete filled steel tube (CFST) columns have an advantage over all other sections when they are used in compression members. This paper proposes a new approach for deriving a new empirical equation to predict the axial compressive capacity of circular CFST columns using the Artificial Neural Network (ANN). The developed ANN model uses 5 input parameters that include the diameter of circular steel tube, the length of the column, the thickness of steel tube, the steel yield strength and the compressive strength of concrete. The only output parameter is the axial compressive capacity. Training and testing the developed ANN model was carried out using 219 available sets of data collected from the experimental results in the literature. An empirical equation is then proposed as an important result of this study, which is practically used to predict the axial compressive capacity of a circular CFST column. To evaluate the performance of the developed ANN model and the proposed equation, the predicted results are compared with those of the empirical equations stated in the current design codes and other models. It is shown that the proposed equation can predict the axial compressive capacity of circular CFST columns more accurately than other methods. This is confirmed by the high accuracy of a large number of existing test results. Finally, the parametric study result is analyzed for the proposed ANN equation to consider the effect of the input parameters on axial compressive strength.

• Journal of Korean Society of Steel Construction
• /
• v.16 no.5 s.72
• /
• pp.695-703
• /
• 2004

In this paper, the results of monotonic loading analysis with four steel models and one composite model were shown. The effect that moment transfer efficiency of a web and strain concentration at a steel beam-to-column connections was investigated. Analysis results showed that the moment transfer efficiency of the analytical model with box-column was poor when comparing to model with H-column due to out-of-plane deformation of the box-column flange. The presence of scallop, thin plate of box column and floor slabs was also a reason of the decrease of moment transfer efficiency, which would result in a potential fracture of the steel beam-to-column connections. Analytical results were compared with experimental results based on previous test. As a result, the deformation capacity of connections with a box-column or a floor slab decreased due to the poor moment transfer efficiency and the strain concentration of beam flange in the vicinity of the steel beam-to-column connections based on the experimental data.

• Steel and Composite Structures
• /
• v.19 no.6
• /
• pp.1403-1419
• /
• 2015

When precast concrete infill panels are connected to steel frames at discrete locations, interaction at the structural interface is neither complete nor absent. The contribution of precast concrete infill panels to the lateral stiffness and strength of steel frames can be significant depending on the quality, quantity and location of the discrete interface connections. This paper presents preliminary experimental and finite element results of an investigation into the composite behaviour of a square steel frame with a precast concrete infill panel subject to lateral loading. The panel is connected at the corners to the ends of the top and bottom beams. The Frame-to-Panel-Connection, FPC4 between steel beam and concrete panel consists of two parts. A T-section with five achor bars welded to the top of the flange is cast in at the panel corner at a forty five degree angle. The triangularly shaped web of the T-section is reinforced against local buckling with a stiffener plate. The second part consists of a triangular gusset plate which is welded to the beam flange. Two bolts acting in shear connect the gusset plate to the web of the T-section. This way the connection can act in tension or compression. Experimental pull-out tests on individual connections allowed their load deflection characteristics to be established. A full scale experiment was performed on a one-storey one-bay 3 by 3 m infilled frame structure which was horizontally loaded at the top. With the characteristics of the frame-to-panel connections obtained from the experiments on individual connections, finite element analyses were performed on the infilled frame structures taking geometric and material non-linear behaviour of the structural components into account. The finite element model yields reasonably accurate results. This allows the model to be used for further parametric studies.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.5
• /
• pp.130-138
• /
• 2023

In this study, experimental and analytical studies were conducted on the structural performance of permanent steel formed wide beams in construction stage. Four specimens were fabricated with different rib spacings of the side steel formwork and fixing plate depths, and experimental tests were performed to investigate the effects of variables on the structural performance. Also, an finite element analysis model of the steel permanent formwork wide beam was proposed based on the test results. Using the proposed model, parametric studies were performed with variables including rib spacing of the bottom and side steel formwork, spacing, depth, and thickness of the fixing plate to derive optimized details. Furthermore, an artificial neural network model was developed to easily estimate the deformation of the steel permanent formwork wide beam with various details.