• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.5
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• pp.488-496
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• 2023

Ship and bridge structures are a type of long box-shaped structure, and resistance to vertical bending moment is a key factor in their structural design. In particular, because box girders are repeatedly exposed to irregular wave loads for a long time, the continuous collapse behavior of structural members must be accurately predicted. In this study, plastic collapse behavior, including buckling according to load changes of the box girder receiving pure bending moments, was analyzed using a numerical analysis method. The analysis targets were selected as three box girders used in the Gordo experiment. The cause of the difference was considered by comparing the results of the structural strength experiment with those of non-linear finite element analysis. This study proposed a combination of the entire and local sagging shape to reflect the effect of the initial sagging caused by welding heat that is inevitably used to manufacture carbon steel materials. The procedures reviewed in the study and the contents of the initial sagging configuration can be used as a good guide for analyzing the final strength of similar structures in the future.

• Steel and Composite Structures
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• v.44 no.2
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• pp.199-210
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• 2022

This study build finite element analysis (FEA) models describing the bending events of coiled tubing (CT) at the wellhead and trips into the hole, accurately provide the state of stress and strain while the CT is in service. The bending moment and axial force history curves are used as loads and boundary conditions in the diametrical growth models to ensure consistency with the actual working conditions in field operations. The simulation diametrical growth results in this study are more accurate and reasonable. Analysis the factors influencing fatigue and diametrical growth shows that the internal pressure has a first-order influence on fatigue, followed by the radius of the guide arch, reel and the CT diameter. As the number of trip cycles increase, fatigue damage, residual stress and strain cumulatively increase, until CT failure occurs. Significant residual stresses remain in the CT cross-section, and the CT exhibits a residual curvature, the initial residual bending configuration of CT under wellbore constraints, after running into the hole, is sinusoidal. The residual stresses and residual bending configuration significantly decrease the buckling load, making the buckling and buckling release of CT in the downhole an elastic-plastic process, exacerbating the helical lockup. The conclusions drawn in this study will improve CT models and contribute to the operational and economic success of CT services.

• Journal of Korean Society of Steel Construction
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• v.13 no.2
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• pp.201-210
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• 2001

A numerical analysis and experimental study were performed to investigate the behavior and strength of tube-gusset connection subjected to axial and lateral forces. To investigate the behavior of the connections, experiment was conducted by applying three directional loads. Local buckling and local plastic bending deformation of the connection were observed from the test. Analytical results were compared with test results for the limited cases. Primary interests here are the effect of eccentricity on the strength of the connection. To suggest a formula for the strength of tube-gusset connection, lateral forces were replaced with equivalent wall moment and eccenrtric vertical component force of lateral force. Ultimate strength formula for the each force was proposed. Finally, nondimensionalized ultimate strength interaction relationships between the wall moment of tube($M_w$), vertical axial force($P_v$), and eccentric vertical component of lateral force($P_e$) were formulated through parametric study.

• Geotechnical Engineering
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• v.3 no.3
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• pp.21-30
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• 1987

Some methods are presented to estimate the ultimate lateral resistance of single active piles subjected to lateral loads above the ground surface, considering the lateral soil reaction, the pile length and the fixity condition of a pile head. The lateral soil reaction acting on a single active pile embedded in soil due to pile movement can be estimated by use of a theoretical equation which is derived by considering especially the plastic state of ground surrounding the pile and the pile- section shape. The piles are named short or long depending upon the relative magnitude of the induced bending moment to the yielding moment. As for the fixity condition of a pile head, the free head and the unrotated head are considered. Comparison with other experimental results gives that the calculated ultimate lateral resistance obtained by the author's theory is closer to experimental results than the one obtained by Brom's theory.

• Steel and Composite Structures
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• v.17 no.3
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• pp.215-236
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• 2014

The flexural behaviour of steel beams significantly affects the structural performance of the steel frame structures. In particular, the flexural overstrength (namely the ratio between the maximum bending moment and the plastic bending strength) that steel beams may experience is the key parameter affecting the seismic design of non-dissipative members in moment resisting frames. The aim of this study is to present a new formulation of flexural overstrength factor for steel beams by means of artificial neural network (NN). To achieve this purpose, a total of 141 experimental data samples from available literature have been collected in order to cover different cross-sectional typologies, namely I-H sections, rectangular and square hollow sections (RHS-SHS). Thus, two different data sets for I-H and RHS-SHS steel beams were formed. Nine critical prediction parameters were selected for the former while eight parameters were considered for the latter. These input variables used for the development of the prediction models are representative of the geometric properties of the sections, the mechanical properties of the material and the shear length of the steel beams. The prediction performance of the proposed NN model was also compared with the results obtained using an existing formulation derived from the gene expression modeling. The analysis of the results indicated that the proposed formulation provided a more reliable and accurate prediction capability of beam overstrength.

• Computers and Concrete
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• v.31 no.6
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• pp.537-543
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• 2023

To study the seismic behavior of recycled aggregate concrete filled circular steel tube (RACFCST) frames, the seismic behavior experiment of RACFCST frame was carried out to measure the hysteresis curve, skeleton curve and other seismic behavior indexes. Moreover, based on the experimental study, a feasible numerical analysis model was established to analyze the finite element parameters of 8 RACFCST frame specimens, and the influence of different variation parameters on the seismic behavior index for RACFCST frame was revealed. The results showed that the skeleton curve of specimens under different axial compression ratios were divided into three stages: elastic stage, elastic-plastic stage and descending stage, and the descending stage was relatively stable, indicating that the specimen had stronger deformation capacity in the descending stage. With the increase of axial compression ratio, the peak bearing capacity of all specimens reduced gradually, and the reduction was less than 5%. With the decrease of beam-column linear stiffness ratio, the peak bearing capacity decreased gradually. With the decrease of yield bending moment ratio of beam-column, the peak bearing capacity decreased gradually, and the decreasing rate of peak bearing capacity gradually accelerated. In addition, compared with the axial compression ratio, the beam-column linear stiffness ratio and the yield bending moment ratio of beam-column had a more significant influence on the peak bearing capacity of RACFCST frame.

• Journal of Korean Society of Steel Construction
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• v.29 no.2
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• pp.135-145
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• 2017

This study is a secondary study that is a cyclic seismic test of High depth hybrid composite beam and column connection after the primary bending strength test of a high depth Hybrid composite beam. Total of 3 seismic test specimens were prepared to cyclic test. The bracket and beam web spliced by high strength bolt and the bracket and beam upper flange was spliced by welding. Test results showed that the seismic strength was higher than the plastic moment($M_p$) in the positive negative moment section, the requirement of composite intermediate moment frame wes satisfied. Therefore, the requirement of intermediate moment frame can be secured by applying the details of connection of this study results.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.67-79
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• 2008

In this study, a bending test with three encased composite beams were carried out and analyzed using FEM in order to find how chemical adhesion, interface interlock, friction and composite action by shear studs contribute to stiffness, strength and composite action in the interface of encased compo site beams. The test and results of the FEM analysis showed that the difference in the ultimate moment capacity of the composite beams with and without studs is under 10%. The reason is that the effect of chemical adhesion, interface interlock, and friction in the interface on the composite action is so high that the encased beams have a moment capacity above some defined magnitude. Also, the increment of moment capacity up to plastic moment is not large and the increase of linearly proportioned.

• Structural Engineering and Mechanics
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• v.85 no.5
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• pp.679-691
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• 2023

Many codes allow designers to use the bending moment diagram computed by elastic analysis and modify it by a certain amount of moment redistribution (MR) to account for plastic behaviour of continuous beams. However, several researchers indicated that the MR at the ultimate limit state (𝛽_u) for some beams deviate significantly from the specified values of various codes. This paper examines the applicability of the provisions on 𝛽_u in ACI 318-19 and Eurocode 2 through numerical investigations and comprehensively explores the influencing factors. The results show that some parameters not considered in those codes influence 𝛽_u to a certain extent, where the ratio of tensile reinforcement ratio at intermediate support to tensile reinforcement ratio at midspan (𝜌_s1/𝜌_s2) and load type are crucial parameters to consider. The specific combination of these two parameters may make the codes overestimate or significantly underestimate the 𝛽_u. On the other hand, the yield state of both critical sections is found to have an important influence on the influence degree of each parameter on 𝛽_u. The yield conditions are investigated, and an empirical judgment equation is proposed. In addition, the influence laws of the critical parameters on 𝛽_u have been further proved by theoretical derivation. Finally, due to 𝜀_t is found to have a better linear correlation with 𝛽_u than x_u/d, equations as a function of 𝜀_t for predicting the 𝛽_u of continuous beams under the two loads are proposed, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.105-117
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• 1994

A finite element procedure which can trace plastic collapse behavior of plane frame structures under small and large deformation is presented. The member is assumed to be prismatic and straight, and has the rectangular or I cross section. For the elasto-plastic analysis, the concept of plastic hinge is introduced and the incremental displacement method is applied. The limit state condition of the plastic hinge is considered under the combined condition of a bending moment and an axial force. Numerical examples are presented in order to demonstrate the validity and efficiency of the proposed procedure.