• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.193-203
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• 2022

In this study, in order to compare the seismic performance of steel structure beam-column connection details and non-scallop connection details mainly used in Korea, a full-scale static cyclic loading test and FEM analysis were conducted through the same modeling as the experiment. For quantitative numerical comparison, the strain concentration ratio and moment transfer efficiency used in previous studies were cited. As the welding area of the beam web decreased, the deformation rate of the beam flange increased, and the plastic deformation capacity according to the rotation angle decreased or brittle fracture occurred. Comparing the analysis results with the experimental results, the possibility of brittle fracture tended to increase when the web welding ratio for the total cross-sectional area of H-shaped fell below 60%.

• Steel and Composite Structures
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• v.15 no.3
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• pp.343-355
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• 2013

Shear failure and core concrete crushing at plastic hinge region are the two main failure modes of bridge piers, which can make repair impossible and cause the collapse of bridge. To avoid the two types of failure of pier, a composite pier was proposed, which was formed by embedding high strength concrete filled steel tubular (CFT) column in reinforced concrete (RC) pier. Through cyclic loading tests, the seismic performances of the composite pier were studied. The experimental results show that the CFT column embedded in composite pier can increase the flexural strength, displacement ductility and energy dissipation capacity, and decrease the residual displacement after undergoing large deformation. The analytical analysis is performed to simulate the hysteretic behavior of the composite pier subjected to cyclic loading, and the numerical results agree well with the experimental results. Using the analytical model and time-history analysis method, seismic responses of a continuous girder bridge using composite piers is investigated, and the results show that the bridge using composite piers can resist much stronger earthquake than the bridge using RC piers.

• Earthquakes and Structures
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• v.12 no.3
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• pp.271-284
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• 2017

This paper presents a multimodal adaptive nonlinear static method of analysis that, differently from the nonlinear static methods suggested in seismic codes, does not require the definition of the equivalent Single-Degree-Of-Freedom (SDOF) system to evaluate the seismic response of structures. First, the proposed method is formulated for the assessment of r.c. plane frames and then it is extended to 3D framed structures. Furthermore, the proposed nonlinear static approach is re-elaborated as a displacement-based design method that does not require the use of the behaviour factor and takes into account explicitly the plastic deformation capacity of the structure. Numerical applications to r.c. plane frames and to a 3D framed structure with inplan irregularity are carried out to illustrate the attractive features as well as the limitations of the proposed method. Furthermore, the numerical applications evidence the uncertainty about the suitability of the displacement demand prediction obtained by the nonlinear static methods commonly adopted.

• Earthquakes and Structures
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• v.14 no.5
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• pp.379-388
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• 2018

This study aims to identify the effect of both longitudinal reinforcement details and damage level on making a decision of repairing pre-damaged bridge columns using basalt fiber reinforced polymer (BFRP) jackets. Two RC bridge columns with improper details of the longitudinal and/or transverse reinforcement were tested under the effect of a constant axial load and increasing lateral cyclic loading. Test results showed that the lap-splice column exhibited an inferior performance where it showed rapid degradation of strength before achieving the theoretical strength and its deformation capacity was limited; however, quick restoration is possible through a suitable rehabilitation technique. On the other hand, expensive repair or even complete replacement could be the decision for the column with the confinement failure mode. After that, a rehabilitation technique using external BFRP jacket was adopted. Performance-based design details guaranteeing the enhancement in the inelastic performance of both damaged columns were addressed and defined. Test results of the repaired columns confirmed that both reparability and the required repairing time of damage structures are dependent on the reinforcement details at the plastic hinge zone. Furthermore, lap-splice of longitudinal reinforcement could be applied as a key design-tool controlling reparability and restorability of RC structures after massive actions.

• Tribology and Lubricants
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• v.30 no.4
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• pp.199-204
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• 2014

Various heat-treated and surface coating methods are used to mitigate abrasion in sliding machine parts. The most cost effective of these methods involves hard coatings such as diamond-like carbon (DLC). DLC has various advantages, including a high level of hardness, low coefficient of friction, and low wear rate. In practice, a supporting layer is generally inserted between the DLC layer and the steel substrate to improve the load carrying capacity. In this study, an indentation and sliding contact problem involving a small, hard, spherical particle and a DLC-coated steel surface is modeled and analyzed using a nonlinear finite element code, MARC, to investigate the influence of the supporting layer thickness on the coating characteristics and the related coating failure mechanisms. The results show that the amount of plastic deformation and the maximum principal stress decrease with an increase in the supporting layer thickness. However, the probability of the high tensile stress within the coating layer causing a crack is greatly increased. Therefore, in the case of DLC coating with a supporting layer, fatigue wear can be another important cause of coating layer failure, together with the generally well-known abrasive wear.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1132-1139
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• 2010

The steel pipe of steel-concrete composite piles increases the pile strength and induces the ductile failure by constraining the deformation of the inner concrete. In this research, the load-movement relations and the reinforcement effect by the outer steel pipe in the steel-concrete composite pile were analyzed by performing three-dimensional numerical analyses, which can simulate the yielding behavior of pile material and the elasto-plastic behavior of soils. The parameters analyzed in the study include three pile materials of steel, concrete and composite, pile diameter, pile distance and loading direction. As the results, the axial capacity of the composite pile was about 73% larger than that of the steel pipe pile and about 14% larger than that of the concrete pile. In addition, the horizontal movement at the pile head of the composite pile was about 51% of that of the steel pile and about 19% of that of the concrete pile.

• Steel and Composite Structures
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• v.21 no.3
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• pp.605-628
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• 2016

The energy absorption characteristics of diamond core sandwich cylindrical columns under axial crushing process depend greatly on the amount of material which participates in the plastic deformation. Both the single-objective and multi-objective optimizations are performed for columns under axial crushing load with core thickness and helix pitch of the honeycomb core as design variables. Models are optimized by multi-objective particle swarm optimization (MOPSO) algorithm to achieve maximum specific energy absorption (SEA) capacity and minimum peak crushing force (PCF). Results show that optimization improves the energy absorption characteristics with constrained and unconstrained peak crashing load. Also, it is concluded that the aluminum tube has a better energy absorption capability rather than steel tube at a certain peak crushing force. The results justify that the interaction effects between the honeycomb and column walls greatly improve the energy absorption efficiency. A ranking technique for order preference (TOPSIS) is then used to sort the non-dominated solutions by the preference of decision makers. That is, a multi-criteria decision which consists of MOPSO and TOPSIS is presented to find out a compromise solution for decision makers. Furthermore, local and global sensitivity analyses are performed to assess the effect of design variable values on the SEA and PCF functions in design domain. Based on the sensitivity analysis results, it is concluded that for both models, the helix pitch of the honeycomb core has greater effect on the sensitivity of SEA, while, the core thickness has greater effect on the sensitivity of PCF.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.6
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• pp.1-10
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• 2001

In this study, the horizontal loading tests of 10ton and 200ton capacity of LRB(lead-rubber bearing) were performed for the evaluation of the dynamic properties of the LRB. It is noted from the test results that dynamic properties of the LRB are dependent on the loading frequency, vertical load and shear strain. A Slender bearing subjected to large deformation will tend to develop plastic hinges in the end regions of the lead plug which will cause the failure of the lead plug. It is recommended that the appropriate mechanical properties of LRB considering the level of structural response and input ground motion should be used in the design of base isolated structures.

• Journal of Industrial Technology
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• v.19
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• pp.75-79
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• 1999

Rotary bending fatigue tests were performed to investigate the effects of 2-phase matrix structure on fatigue limit with prepared specimens in high strength ductile irons. Two types of the specimens with different microstructures have been used. Series A has sorbite and series B has bainite. Fatigue limits of both specimens are improved comparing with as cast specimen. The fatigue limit is higher in series B than in series A. The reason why the fatigue limit of series A shows inferiority to that of series B is due to the transition of micro fatigue cracks to mesocrack occurs very rapidly, so increased stress intensity factor drives the fatigue crack growth. The higher fatigue limit of series B which has bainite is caused by the ${\gamma}$ layer contained in microstructure impede the rapid growth of micro fatigue crack to mesocrack and ${\alpha}$ layer around graphite has the higher capacity for the absorption of plastic deformation energy than sorbite.

• Steel and Composite Structures
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• v.25 no.5
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• pp.545-556
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• 2017

The tubed steel reinforced concrete (SRC) column is a composite column in which the outer steel tube is mainly used to provide confinement on the core concrete. This paper presents experimental and analytical studies on the behavior of circular tubed SRC (TSRC) columns subjected to axial compression. Eight circular TSRC columns were tested to investigate the effects of length-to-diameter ratio (L/D) of the specimens, diameter-to-thickness ratio (D/t) of the steel tubes, and use of stud shear connectors on the steel sections. Elastic-plastic analysis on the steel tubes was used to investigate the mechanism of confinement on the core concrete. The test results indicated that the tube confinement increased the strength and deformation capacity for both short and slender columns, and the effects on strength were more pronounced for short columns. A nonlinear finite element (FE) model was developed using ABAQUS, in which the nonlinear material behavior and initial geometric imperfection were included. Good agreement was achieved between the predicted results using the FE model and the test results. The test and FE results were compared with the predicted strengths calculated by Eurocode 4 and the AISC Standard. Based on the analytical results, a new design method for this composite column was proposed.