• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.257-264
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• 2010

Generally, estimations on the displacement as an important factor in evaluating the safety of large structures could be a barometer assessing whether the condition of the structure is deteriorating. Practically, it is not easy how to measure the displacement response to large structures like suspension bridges. In this study, as a method for estimation displacement response from strain signals, mode decomposition technique is proposed. Total displacement response is estimated by superposing quasistatic displacement response and modal displacement responses in dominant modes with larger contributions after estimating the modal displacement responses. If foiled strain gauges are used to measure strain signals, there would likely to generate electric noise, what's more, the more measuring points there are the more economic burden it could be. In order to solve such problems, fiber optic bragg-grating(FBG) sensors were used, which have multi-point measurements with no effect on electric noises. Therefore, the experiment was performed through dynamic load test of suspension bridge and plate-girder bridge to review the possibility for using mode decomposition technique.

• Geomechanics and Engineering
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• v.34 no.3
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• pp.233-250
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• 2023

This paper investigates the flexural analysis of isotropic, transversely isotropic, and laminated composite plates using a new higher-order normal and shear deformation theory. In the present theory, only five unknown functions are involved compared to six or more unknowns used in the other similar theories. The developed theory does not need a shear correction factor. It can satisfy the zero traction boundary conditions on the top and the bottom surfaces of the plate as well as account for sufficient distribution of the transverse shear strains. The thickness stretching effect is considered in the computation. A simply supported was considered on all edges of the plate. The plate is subjected to uniform and sinusoidal distributed load in the static analysis. Laminated composite, isotropic, and transversely isotropic plates are considered. The governing equations are obtained utilizing the virtual work principle. The differential equations are solved via Navier's procedure. The results obtained from the developed theory are compared with other higher-order theories considered in the previous studies and 3D elasticity solutions. The results showed that the proposed theory accurately and effectively predicts the bidirectional bending responses of laminated composite plates. Several parametric studies are presented to illustrate the various parameters influencing the static response of the laminated composite plates.

• Steel and Composite Structures
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• v.44 no.4
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• pp.451-471
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• 2022

In the present paper, the static bending and buckling responses of functionally graded carbon nanotubes-reinforced composite (FG-CNTRC) beam under various boundary conditions are investigated within the framework of higher shear deformation theory. The significant feature of the proposed theory is that it provides an accurate parabolic distribution of transverse shear stress through the thickness satisfying the traction-free boundary conditions needless of any shear correction factor. Uniform (UD) and four graded distributions of CNTs which are FG-O, FG-X, FG- and FG-V are selected here for the analysis. The effective material properties of FG-CNTRC beams are estimated according to the rule of mixture. To model the FG-CNTRC beam realistically, an efficient Hermite-Lagrangian finite element formulation is successfully developed. The accuracy and efficiency of the present model are demonstrated by comparison with published benchmark results. Moreover, comprehensive numerical results are presented and discussed in detail to investigate the effects of CNTs volume fraction, distribution patterns of CNTs, boundary conditions, and length-to-thickness ratio on the bending and buckling responses of FG-CNTRC beam. Several new referential results are also reported for the first time which will serve as a benchmark for future studies in a similar direction. It is concluded that the FG-X-CNTRC beam is the strongest beam that carries the lowest central deflection and is followed by the UD, V, Λ, and FG-O-CNTRC beam. Besides, the critical buckling load belonging to the FG-X-CNTRC beam is the highest, followed by UD and FG-O.

• Structural Engineering and Mechanics
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• v.88 no.5
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• pp.481-492
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• 2023

The past earthquakes revealed the importance of the design of moment-resisting reinforced concrete framed structures with ductile behavior. Due to seismic activity, failures in framed structures are widespread in beam-column joints. Hence, the joints must be designed to possess sufficient strength and stiffness. This paper investigates the effects of fibers on the ductility of hybrid fiber reinforced self-compacting concrete (HFRSCC) when subjected to seismic actions; overcoming bottlenecks at the beam-column joints has been studied by adding low modulus sisal fiber and high modulus steel fiber. For this, the optimized dose of hooked end steel fiber content (1.5%) was kept constant, and the sisal fiber content was varied at the rate of 0.1%, up to 0.3%. The seismic performance parameters, such as load-displacement behavior, ductility, energy absorption capacity, stiffness degradation, and energy dissipation capacity, were studied. The ductility factor and the cumulative energy dissipation capacity of the hybrid fiber (steel fiber, 1.5% and sisal fiber, 0.2%) added beam-column joint specimen is 100% and 121% greater than the control specimen, respectively. And also the stiffness of the hybrid fiber reinforced specimen is 100% higher than the control specimen. Thus, the test results showed that adding hybrid fibers instead of mono fibers could significantly enhance the seismic performance parameters. Therefore, the hybrid fiber reinforced concrete with 1.5% steel and 0.2% sisal fiber can be effectively used to design structures in seismic-prone areas.

• Steel and Composite Structures
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• v.48 no.1
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• pp.103-111
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• 2023

The caving property of top coal is a key factor to the success of top coal caving mining. The influence law of cyclic loading and unloading of hydraulic support on top coal caving is of great significance to improve the recovery rate of top coal. The similar simulation methods were used to study the dynamic evolution of the top coal cracks under the multi-cycle action of the support, and the parameters of top coal cracks were analyzed quantitatively in this paper. The results show that the top coal cracks can be divided into horizontal cracks and vertical cracks under the cyclic loading and unloading of the support. With the increase of the times of the support cycles loading and unloading, the load on the support decreases, the fractal dimension of the cracks increases, the number and total length of the top coal cracks increases, and the top coal caving is getting better. With the increase of the times of multi-cycle loading and unloading, the fractal dimension, total crack length and crack rate of top coal show a trend of rapid increase first and then increase slowly. Both the total length of the top coal cracks and the crack rate basically show linear growth with the change of the fractal dimension. The top coal caving can be well improved and the coal resource recovery rate increased through the multi-cycle loading and unloading.

• The Journal of the Convergence on Culture Technology
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• v.10 no.1
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• pp.363-368
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• 2024

Steel structures used in marine environments, such as ships, offshore structures or sub-structures in wind power generation facilities are prone to corrosion. In this study, the corrosion fatigue crack propagation characteristics due to the environmental load are examined by experiment at -1050 mV vs. SCE, which is equivalent to the anti-corrosion potential of zinc anodes that are widely used as sacrificial anodes. In this study, for this purpose, an experimental study is conducted on the effect of cathodic protection on the propagation of fatigue cracks in the seawater environment under the condition of -1050 mV vs. SCE, considering the wave period in synthetic seawater. Cathodic protection prevents corrosion; however, excessive protection generates hydrogen through chemical reactions as well as calcareous deposits. The fatigue crack propagation rate appeared to be faster than the rate in a seawater corrosion environment at the early stages of the experiment. As the crack length and stress intensity factor K increased, the crack propagation rate became slower than the fatigue crack propagation rate in seawater. However, the crack growth rate was faster than that in the atmosphere.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.4
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• pp.87-96
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• 2006

A ship collision analysis by finite element method is performed considering the effects of mass and speed of ship and material and shape of structures to analyze the dynamic characteristics by ship collision. From this analysis, collision load-time history and damage of ship and structures are obtained. In this study, results of finite element analysis are compared with previous studies in USA, Japan and some countries of Europe. Dynamic characteristics are different from each other according to interaction between ship and structures. It seems that there are lots of factor to have effects on the ship-structures interaction. Because little information is available on the behavior of the inelastic deformation of materials and structures during the type of dynamic impacts associated with vessel impact, assumptions based on experience and sound engineering practice should be substituted. Therefore more researches on the interaction between ship and structures are required.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.5
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• pp.197-211
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• 2007

The deteriorated PSC Beam bridge is necessary improved reinforcement method. In the study, it is proposed the box reinforcing method which could make the stiffness of the PSC Beam bridges increase more stably through the secondary composition effect of open type PSC Beam bridge's girder which is converted into the consolidation box type and the half panel is formed between the lower flange of the PSC Beam about the deteriorated PSC Beam bridge suffering the capacity decline. In case the proposed reinforcement method combine with the existed external prestressed method, the close analysis depending on the time is conducted by the construction stage because of searching the effect of reinforcement quantitatively. The reinforcement method of the box type which is proposed an efficiency improvement in objective in application case, by a reinforcement method after proposing the whole and bend sectional reinforcement method, against a each reinforcement method evaluated the upward camber which it follows in secondary composite effect and a member stress characteristics. Also, the structural safety of PSC Beam bridge is evaluated quantitatively by examining of rating factor through load carrying capacity evaluation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.4 s.56
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• pp.170-179
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• 2009

Channel-type lining board(CLB) is a welded steel structure used in the field of open cut subway excavation and building basement construction. Lining board is generally installed at the underground environment which is exposed to corrosion factors such as humidity, temperature and corrosive gases. This study evaluates reusability of the corroded lining board by experimental and analytical method. Static loading tests were performed to know serviceability of corroded CLB after checking thickness loss of the used CLB parts. Strain of the plates and middle point deflection was measured simultaneously. According to experimental test results and comparison with numerical analysis, the thickness loss of the plates by corrosion makes more vertical displacements and stresses in members under the DB vehicle load considering impact factor. As a result, this paper is proposed a way to evaluate used and corroded CLB by checking the plates thickness and it makes construction engineers easy to know optimal time to replace their old CLBs with new one.

• Journal of the Society of Disaster Information
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• v.10 no.4
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• pp.583-597
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• 2014

Fire caused by heater has various causes as many as the types of heater. also, lots of damage of human life and property loss are caused, since annually continuous fire accident by heater in traditional market is frequently occurring. There are not many cases of fire due to heater in most of residential facilities such as general house, apartments, etc., because they are supplied with heating boiler, however the restaurant, store and office of the market, sports center, factory, workplace, etc. still use heater, e.g. oilstove, electric heater, etc., so that they are exposed to fire hazard. Also, when investigating the number of fire due to heater, it was analyzed to occur in order of home boiler, charcoal stove, oilstove, gas heater/stove, electric stove/heater, the number of fire per human life damage was analyzed in order of gas heater/stove, oil heater/stove, electric heater/stove, briquette/coal heater. Also, gas and oil related heater were analyzed to have low frequency, however, with high fire intensity. Therefore, this research aimed at considering more scientific fire inspection and identification approach by reenacting and reviewing fire outbreak possibility caused by combustibles' contact and conductivity under the normal condition and abnormal condition in respect of ignition hazard, i.e. minimum ignition temperature, carbonization degree and heat flux along with it, due to oilstove and electric stove, which are still frequently used in public use facility, traditional market, and, of which actual fire occurrence is the most frequent. As the result of reenact test, ignition hazard appeared very small, as long as enough heat storage condition is not made in both test objects(oilstove/electric stove), however carbonization condition was analyzed to be proceeded per each part respectively. Eventually, transition to fire is the ignition due to heat storage, so that it was analyzed to ignite when minimum heat storage temperature condition of fire place is over $500^{\circ}C$. Particularly, in case of quartz pipe, the heating element of electric stove, it is rapidly heated over the temperature of $600^{\circ}C$ within the shortest time(10sec), so that the heat flux of this appears 6.26kW/m2, which was analyzed to result in damage of thermal PVC cable and second-degree burn in human body. Also, the researcher recognized that the temperature change along with Geometric View Factor and Fire Load, which display decrease of heat, are also important variables to be considered, along with distance change besides temperature condition. Therefore, the researcher considers that a manual of careful fire inspection and identification on this is necessary, also, expects that scientific and rational efforts of this research can contribute to establish manual composition and theoretical basis on henceforth fire inspection and identification.