• Steel and Composite Structures
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• v.44 no.3
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• pp.437-450
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• 2022

When the vertical load-bearing members in high-rise structures fail locally, the beam-column joints play an important role in the redistribution of the internal forces. In this paper, a static laboratory test of three full-scale flush flange beam-reinforced connections with side and cover plates (CP-FBSP connection) with double half-span steel beams and single L-shaped columns composed of concrete-filled steel tubes (L-CFST columns) was conducted. The influence of the side plate width and cover plate thickness on the progressive collapse resistance of the substructure was thoroughly analyzed. The failure mode, vertical force-displacement curves, strain variation, reaction force of the pin support and development of internal force in the section with the assumed plastic hinge were discussed. Then, through the verified finite element model, the corresponding analyses of the thickness and length of the side plates, the connecting length between the steel beam flange and cover plate, and the vertical-force eccentricity were carried out. The results show that the failure of all the specimens occurred through the cracking of the beam flange or the cover plate, and the beam chord rotations measured by the test were all greater than 0.085 rad. Increasing the length, thickness and width of the side plates slightly reduced the progressive collapse resistance of the substructures. The vertical-force eccentricity along the beam length reduced the progressive collapse resistance of the substructure. An increase in the connecting length between the beam flange and cover plate can significantly improve the progressive collapse resistance of substructures.

• Steel and Composite Structures
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• v.42 no.1
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• pp.91-106
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• 2022

Concrete-filled square stainless steel tubes (CFSSST), which possess relatively large flexural stiffness, high corrosion resistance and require simple joint configurations and low maintenance cost, have a great potential in constructional applications. Despite that the use of stainless steel may result in high initial cost compared to their conventional carbon steel counterparts, the whole-life cost of CFSSST is however considered to be lower, which offers a competitive choice in engineering practice. In this paper, a comprehensive experimental and numerical program on 24 CFSSST stub column specimens, including 3 austenitic and 3 duplex stainless steel square hollow section (SHS) stub columns and 9 austenitic and 9 duplex CFSSST stub columns, has been carried out. Finite element (FE) models were developed to be used in parametric analysis to investigate the influence of the tube thickness and concrete strength on the ultimate capacities more accurately. Comparisons of the experimental and numerical results with the predictions made by design guides ACI 318, ANSI/AISC 360, Eurocode 4 and GB 50936 have been performed. It was found that these design methods generally give conservative predictions to the ultimate capacities of CFSSST stub columns. Improved calculation methods, developed based on the Continuous Strength Method, have been proposed to provide more accurate estimations of the ultimate resistances of CFSSST stub columns. The suitability of these proposals has been validated by comparison with the test results, where a good agreement between the predictions and the test results have been achieved.

• Structural Engineering and Mechanics
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• v.90 no.4
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• pp.371-390
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• 2024

Investigating the impact of openings on the structural behavior of ferrocement I-beams with two distinct types of reinforcing metallic and non-metallic meshes is the primary goal of the current study. Up until failure, eight 250x200x2200 mm reinforced concrete I-beams were tested under flexural loadings. Depending on the kind of meshes used for reinforcement, the beams are split into two series. A control I-beam with no openings and three beams with one, two, and three openings, respectively, are found in each series. The two series are reinforced with three layers of welded steel meshes and two layers of tensar meshes, respectively, in order to maintain a constant reinforcement ratio. Structural parameters of investigated beams, including first crack, ultimate load, deflection, ductility index, energy absorption, strain characteristics, crack pattern, and failure mode were reported. The number of mesh layers, the volume fraction of reinforcement, and the kind of reinforcing materials are the primary factors that vary. This article presents the outcomes of a study that examined the experimental and numerical performance of ferrocement reinforced concrete I-beams with and without openings reinforced with welded steel mesh and tensar mesh separately. Utilizing ANSYS-16.0 software, nonlinear finite element analysis (NLFEA) was applied to illustrate how composite RC I-beams with openings behaved. In addition, a parametric study is conducted to explore the variables that can most significantly impact the mechanical behavior of the proposed model, such as the number of openings. The FE simulations produced an acceptable degree of experimental value estimation, as demonstrated by the obtained experimental and numerical results. It is also noteworthy to demonstrate that the strength gained by specimens without openings reinforced with tensar meshes was, on average, 22% less than that of specimens reinforced with welded steel meshes. For specimens with openings, this value is become on average 10%.

• Journal of Korean Society of Steel Construction
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• v.21 no.1
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• pp.63-70
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• 2009

Failure modes result in fracture or tearing, which may cause deterioration of resistance and reduction of inelastic deformation capacity. The potential failure modes for Special Concentrically Braced Frames (SCBFs) include fracture or tearing of the brace, net section fracture of the brace or gusset plate, fracture of the gusset plate welds, shear fracture of the bolts, block shear, excessive bolt bearing deformation, and buckling of the gusset plate. HSS tubular braces are commonly used in SCBFs, and net section fracture of the tubular brace may also occur through the brace net section at the end of the slot cut into the tube to slip over the gusset plate. This failure mode is categorized as a tension failure mode, and may cause dramatic loss of resistance and brittle behavior. Net section reinforcement is required according to AISC design specifications (AISC 2001). In this paper, the need to reinforce the net section area was discussed. Initially, the results of the net section fracture tests done by the University of California in Berkeley were presented with the modeling of these tests using FE models. To investigate the possibility of net section fracture in an actual frame, the slot end hole model was adapted to the frame FE model, and alternate near-fault histories were applied with tension-dominated cycles, since previous analyses showed that loading history was the most critical factor in net section fracture. The need for this reinforcement (cover plate) and the tension-dominated near-fault history were investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1337-1345
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• 2011

In pressurized water reactors (PWRs), the reactor pressure vessel (RPV) upper head contains numerous control rod drive mechanism (CRDM) nozzles. In the last 10 years, the incidences of cracking in alloy 600 CRDM nozzles and their associated welds has increased significantly. Several axial and circumferential cracks have been found in CRDM nozzles in European PWRs and U.S. nuclear power plants. These cracks are caused by primary water stress corrosion cracking (PWSCC) and have been shown to be driven by welding residual stresses and operational stresses in the weld region. Therefore, detailed finite-element (FE) simulations for the Korea Nuclear Reactor Pressure Vessel have been conducted in order to predict the magnitudes of the weld residual stresses in the tube materials. In particular, the weld residual stress results are compared in terms for nozzle location, geometry factor$r_o$/t, geometry of fillet, and adjacent nozzle.

• Journal of Biomedical Engineering Research
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• v.25 no.6
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• pp.519-523
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• 2004

This study investigates micro-structural and mechanical properties of trabecular bone in human femoral head with and without osteoporosis using Micro-CT and finite element-model. 15 cored trabecular bone specimens with 20min of diameter were obtained from femoral heads with osteoporosis (T-score > -2.5 ) resected for total hip arthroplasty, and 5 specimens were removed from femoral head of cadavers, which has no history of musculoskeletal diseases. A high-resolution micro-CT system was used to scan each specimen to obtain histomorphometry indices. Based on obtained micro-images(pixel size=21.31㎛), a FE-model was created to determine mechanical property indices. While non-osteoporosis group had increases trabecular thickness, bone volume, bone volume fraction, degree of anisotropy and trabecular number compared with those of non-osteoporotic group, the non-osteoporotic group showed decreases in trabecular separation and structure model index. Regarding the mechanical property indices, reaction force, apparent stress and young's modulus were 1ower in osteoporotic group than in non-osteoporotic group. Our data shows salient deteriorations in trabecular micro-structural and mechanical properties in human femoral head with osteoporosis.

• Journal of the Society of Disaster Information
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• v.17 no.4
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• pp.747-754
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• 2021

Purpose: Seismic safety evaluation of a curved bridge must be performed since the curved bridges exhibit the complex behavior rather than the straight bridges, due to geometrical characteristics. In order to conduct the probabilistic seismic assessment of the curved bridge, Seismic fragility evaluation was performed using the uncertainty of the steel material properties of a curved bridge girde, in this study. Method: The finite element (FE) model using ABAQUS platform of the curved bridge girder was constructed, and the statistical parameters of steel materials presented in previous studies were used. 100 steel material models were sampled using the Latin Hypercube Sampling method. As an input ground motion in this study, seismic fragility evaluation was performed by the normalized scale of the Gyeongju earthquake to 0.2g, 0.5g, 0.8g, 1.2g, and 1.5g. Result: As a result of the seismic fragility evaluation of the curved girder, it was found that there was no failure up to 0.03g corresponding to the limit state of allowable stress design, but the failure was started from 0.11g associated with using limit state design. Conclusion: In this study, seismic fragility evaluation was performed considering steel materials uncertainties. Further it must be considered the seismic fragility of the curved bridge using both the uncertainties of input motions and material properties.

• Structural Engineering and Mechanics
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• v.76 no.6
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• pp.687-708
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• 2020

Openings in steel plate shear walls (SPSWs) are usually used for decorative designs, crossing locations of multiple utilities and/or structural objectives. However, earlier studies showed that generating an opening in an SPSW has a negative effect on the cyclic performance of the SPSW. Therefore, this study proposes tripling or doubling the steel-sheet-plate (SSP) layer and stiffening the opening of the SPSW to provide a solution to undesirable opening effects, improve the SPSW performance and provide the infill option of potential strengthening measures after the construction stage. The study aims to investigate the impact of SSP doubling with a stiffened opening on the cyclic behaviour, expand the essential data required by structural designers and quantify the SPSW performance factors. Validated numerical models were adopted to identify the influence of the chosen parameters on the cyclic capacity, energy dissipation, ductility, seismic performance factors (SPF) and stiffness of the suggested method. A finite Element (FE) analysis was performed via Abaqus/CAE software on half-scale single-story models of SPSWs exposed to cyclic loading. The key parameters included the number of SSP layers, the opening size ratios corresponding to the net width of the SSP, and the opening shape. The findings showed that the proposed assembly method found a negligible influence in the shear capacity with opening sizes of 10, 15, 20%. However, a deterioration in the wall strength was observed for openings with sizes of 25% and 30%. The circular opening is preferable compared with the square opening. Moreover, for all the models, the average value of the obtained ductility did not show substantial changes and the ultimate shear resistance was achieved after reaching a drift ratio of 4.36%. Additionally, the equivalent sectional area of the SSP in the twin and triple configuration of the SPSWs demonstrated approximately similar results. Compared with the single SSP layer, the proposed configuration of the twin SSP layer with a stiffened opening suggest to more sufficiency create SSP openings in the SPSW compared to that of other configurations. Finally, a tabular SPF quantification is exhibited for SPSWs with openings.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4D
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• pp.485-492
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• 2008

This study presents a viscoelastic characterization of flexible pavement subjected to moving loads. A series of field tests have been conducted on three pavement sections (A2, A5, and A8) at the Korea Expressway Corporation (KEC) test road. The effect of vehicle speed on the responses of each test section was investigated at three speeds: 25 km/hr, 50 km/hr, and 80 km/hr. During the test, both longitudinal and lateral strains were measured at the bottom of asphalt layers and in-situ measurements were compared with the results of finite element (FE) analyses. A commercial FE package, ABAQUS was used to model each test section and a step loading approximation has been adopted to simulate the effect a moving vehicle. For viscoelastic analysis, relaxation moduli of asphalt mixtures were obtained from laboratory test. Field responses reveals the strain anisotropy (i.e., discrepancy between longitudinal and lateral strains) and the amplitude of strain normally decreases as the vehicle speed increases. In most cases, lateral strain was smaller than longitudinal strain, and strain reduction was more significant in lateral direction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.815-826
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• 1994

Skew bridges are found frequently in new bridge construction due to geographical conditions when new constructing bridges are put across the existing highways, railroads or rivers. This study is to investigate the static behaviors of the steel deck plates of skew bridges which are increasingly used in bridges due to outstanding quality of structural steels, development of welding techniques, in order to reduce dead loads and period of constructions. The static behaviours of steel deck plates are analyzed using general purpose FE code SAP90 by modeling the skewed deck plates with rigorous finite elements, as the skew angles vary. The results of finite element analysis for the behaviors of steel deck plates and concrete slabs in acute, obtuse corners and center of decks are compared and discussed as the skew angles vary from $90^{\circ}$ to $30^{\circ}$. Two types of decks are treated, as isotropic plates and orthotropic plates, respectively. From the results of finite element analysis, it is found that more moments, reactions, and deflections occur at the obtuse corners than at the center of skewed decks regardless of isotropy or orthotropy. Especially, in case of the skewed deck plates with skew angles less than 45 degrees, significantly large discrepancies for the values of those internal forces are shown between the skewed and right deck plates. This study estimates the characteristics of deck behaviors according to skew angles, and proposes limitations of skew angles and the ciritical regions of decks.