• 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.

• Structural Engineering and Mechanics
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• v.85 no.1
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• pp.105-118
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• 2023

The present work is an attempt to develop a simple and accurate finite element formulation for the assessment of thermal shock/thermally induced vibrations in pretwisted and tapered functionally graded material thin (FGM) blades obtained from Voigt and local representative volume elements (LRVE) homogenization models, based on neutral surface approach. The neutral surface of the FGM blade does not coincide with its mid-surface. A finite element model (FEM) is developed using first-order shear deformation theory (FSDT) and the FGM turbine blade is modelled according to the shallow shell theory. The top and the bottom layers of the FGM blade are made of pure ceramic and pure metal, respectively and temperature-dependent material properties are functionally graded in the thickness direction, the position of the neutral surface also depends on the temperature. The material properties are estimated according to two different homogenization models viz., Voigt or LRVE. The top layer of the FGM blade is subjected to high temperature and the bottom surface is either thermally insulated or kept at room temperature. The solution of the nonlinear profile of the temperature in the thickness direction is obtained from the Fourier law of heat conduction in the unsteady state. The results obtained from the present FEM are compared with the benchmark examples. Next, the effect of angle of twist, intensity of thermal shock, variable chord and span and volume fraction index on the transient response due to thermal shock obtained from the two homogenization models viz., Voigt and LRVE scheme is investigated. It is shown that there can be a significant difference in the transient response calculated by the two homogenization models for a particular set of material and geometric parameters.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2A
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• pp.149-159
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• 2010

This paper presents an experimental study on the structural behavior of composite CFT truss girder bridge with full depth precast panels. The length of span is 20,000 mm. The CFT truss girder is a tubular truss composed of chord members made of concrete-filled and hollow circular tubes. To determine fundamental structural characteristics such as the strength and deformation properties of composite CFT truss girder bridge, static and dynamic tests were conducted. The natural frequencies calculated by the FEM are in good agreement with experimental results obtained from dynamic test. Bracing have only a small effect on the natural frequencies of composite CFT truss girder bridge as indicated by the FEM results. The yield strength and deformation of the composite CFT truss girder bridges were investigated through a static bending test. Besides, the test results showed that uniform distribution of shear connectors can be applicable in composite CFT truss girder bridges.

• Restorative Dentistry and Endodontics
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• v.47 no.4
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• pp.43.1-43.13
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• 2022

Objectives: This study compared the surface gloss (SG), gloss retention (GR), and color stability (CS) of 2 universal resin composites after chemical (CA) and mechanical (MA) aging. Materials and Methods: Twenty disc-shaped samples of G-ænial A'Chord (GC-Europe) and Filtek Universal (3M-ESPE) were polished with sequential abrasive papers. For CA, specimens were stored in 1 mL of 75% ethanol for 15 days at 37℃, and readings (SG, GR, and CS) were obtained at baseline and 5, 10, and 15 days. For MA, specimens were subjected to 10,750 simulated brushing cycles. SG and CS were evaluated after every 3,583 cycles. SG was measured with a glossmeter (geometrical configuration: 60°), and values were expressed in gloss units. Color was measured with a spectrophotometer using the CIE-L^*a^*b^* color system. The Student's t-test, 1-way analysis of variance, and Scheffé test were used for statistical analysis (α = 0.05). Results: G-ænial presented significantly higher SG values than Filtek (p = 0.02), with GR reductions of 5.2% (CA) and 5.3% (MA) for G-ænial and 7.6% (CA) and 7.2% (MA) for Filtek. The aging protocol had no statistically significant effect on SG or GR (p = 0.25) from baseline to the final readings. G-ænial-MA presented the lowest color difference (ΔE = 1.8), and G-ænial-CA and Filtek-CA had the largest changes (ΔE = 8.6 and ΔE = 11.8, respectively). Conclusion: G-ænial presented higher SG values and better CS. Both restorative materials demonstrated acceptable GR and CS. Aging protocols impacted these properties negatively.

• Advances in aircraft and spacecraft science
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• v.10 no.4
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• pp.303-315
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• 2023

The primary goal of this research is to investigate flow separation phenomena using various turbulence models. Also investigated are the effects of free-stream turbulence intensity on the flow over a NACA 0018 airfoil. The flow field around a NACA 0018 airfoil has been numerically simulated using RANS at Reynolds numbers ranging from 100,000 to 200,000 and angles of attack (AoA) ranging from 0° to 18° with various inflow conditions. A parametric study is conducted over a range of chord Reynolds numbers for free-stream turbulence intensities from 0.1 % to 0.5 % to understand the effects of each parameter on the suction side laminar separation bubble. The results showed that increasing the free-stream turbulence intensity reduces the length of the separation bubble formed over the suction side of the airfoil, as well as the flow prediction accuracy of each model. These models were used to compare the modeling accuracy and processing time improvements. The K- SST performs well in this simulation for estimating lift coefficients, with only small deviations at larger angles of attack. However, a stall was not predicted by the transition k-kl-omega. When predicting the location of flow reattachment over the airfoil, the transition k-kl-omega model also made some over-predictions. The Cp plots showed that the model generated results more in line with the experimental findings.

• Computers and Concrete
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• v.33 no.3
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• pp.251-264
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• 2024

The present study pertains to the effects of variations in the location and size of drilled web openings on the behavior of fixed-fixed reinforced concrete (RC) beams. For this purpose, a reference bending beam with a transverse opening in each half span was tested to failure. Later, the same beam was modeled and analyzed with the help of finite element software using ABAQUS. Upon achieving close agreement between the experimental and numerical results, the location and size of the web opening were altered to uncover the effects of these factors on the shear strength and load-deflection behavior of RC beams. The experimental failure mode of the tested beam and the numerical results were also verified by theoretical calculations. In numerical analysis, when compared to the reference (D0) specimen, if the distance of the opening center from the support is 0 or h or 2h, reduction in load-bearing capacity of 1.5%-22.8% or 2.0%-11.3% or is 4.1%-40.7%. In other words, both the numerical analyses and theoretical calculations indicated that the beam behavior shifted from shear-controlled to flexure-controlled as the openings approached the supports. Furthermore, the deformation capacities, energy absorption values, and the ductilities of the beams with different opening diameters also increased with the decreasing distance of the opening from supports. Web compression failure was shown to be the predominant mode of failure of beams with large diameters due to the lack of sufficient material in the diagonal compression strut of the beam. The present study indicated that transverse openings with diameters, not exceeding about 1/3 of the entire beam depth, do not cause the premature shear failure of RC beams. Finally, shear damage should be prevented by placing special reinforcements in the areas where such gaps are opened.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.4
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• pp.371-382
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• 2008

The objective of this study is to develop the laboratory testing method for evaluating the loading capacity of lattice girder used for support in tunnel structure. 3-point flexible strength test and 4-point flexible strength test were performed on three types of lattice girder, such as $LG-50{\times}20{\times}30$, $LG-70{\times}20{\times}30$, and $LG-95{\times}22{\times}32$, mainly used in Korea. Two types of loading position for each flexible strength test were used to analyze the behavior of load-deformation. The loading distribution in the lattice girder was analyzed by means of strains measured by strain gauges attached on chords and diagonal bars. In 3-point flexible strength test, the difference of the average of maximum flexible strength according to loading position had the range from 10% to 33%. In 4-point flexible strength test, the average of maximum flexible strength according to loading position was almost no difference. The difference between the average of maximum flexible strengths obtained from 3-point and 4-point flexible strength tests was from 13.56 to 31.55%. The load applied on the lattice girder was concentrated to the main chord in 3-point flexible strength test. The load applied on the lattice girder in 4-point flexible strength test was distributed to three chords and diagonal bars.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.5
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• pp.616-627
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• 2014

The Lanyu is a miniature pig breed indigenous to Lanyu Island, Taiwan. It is distantly related to Asian and European pig breeds. It has been inbred to generate two breeds and crossed with Landrace and Duroc to produce two hybrids for laboratory use. Selecting sets of informative genetic markers to track the genetic qualities of laboratory animals and stud stock is an important function of genetic databases. For more than two decades, Lanyu derived breeds of common ancestry and crossbreeds have been used to examine the effectiveness of genetic marker selection and optimal approaches for individual assignment. In this paper, these pigs and the following breeds: Berkshire, Duroc, Landrace and Yorkshire, Meishan and Taoyuan, TLRI Black Pig No. 1, and Kaohsiung Animal Propagation Station Black pig are studied to build a genetic reference database. Nineteen microsatellite markers (loci) provide information on genetic variation and differentiation among studied breeds. High differentiation index ($F_{ST}$) and Cavalli-Sforza chord distances give genetic differentiation among breeds, including Lanyu's inbred populations. Inbreeding values ($F_{IS}$) show that Lanyu and its derived inbred breeds have significant loss of heterozygosity. Individual assignment testing of 352 animals was done with different numbers of microsatellite markers in this study. The testing assigned 99% of the animals successfully into their correct reference populations based on 9 to 14 markers ranking D-scores, allelic number, expected heterozygosity ($H_E$) or $F_{ST}$, respectively. All miss-assigned individuals came from close lineage Lanyu breeds. To improve individual assignment among close lineage breeds, microsatellite markers selected from Lanyu populations with high polymorphic, heterozygosity, $F_{ST}$ and D-scores were used. Only 6 to 8 markers ranking $H_E$, $F_{ST}$ or allelic number were required to obtain 99% assignment accuracy. This result suggests empirical examination of assignment-error rates is required if discernible levels of co-ancestry exist. In the reference group, optimum assignment accuracy was achievable achieved through a combination of different markers by ranking the heterozygosity, $F_{ST}$ and allelic number of close lineage populations.

• Journal of the Korea Concrete Institute
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• v.13 no.6
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• pp.610-618
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• 2001

This paper investigates the relationships between dynamic elastic modulus and static elastic modulus or compressive strength according to curing temperature, aging, and cement type. Based on this investigation, the new model of the relationships we proposed. Impact echo method estimates the resonant frequency of specimens and uniaxial compression test measures the static elastic modulus and compressive strength. Type I and V cement concretes, which have the water-cement ratios of 0.40 and 0.50, are cured under the isothermal curing temperatures of 10, 23, and 50$\^{C}$ Cement type and aging have no large influence on the relationship between dynamic and static elastic modulus, but the ratio of dynamic and static elastic modulus comes close to 1 as temperature increases. Initial chord elastic modulus which is calculated at lower strain level of stress-strain curve, has the similar value to dynamic elastic modulus. The relationship between dynamic elastic modulus and compressive strength has the same tendency as the relationship between dynamic and static elastic modulus according to cement type, temperature and aging. The proposcd relationship equations between dynamic elastic modulus and static elastic modulus or compressive strength properly estimates the variation of relationships according to cement type md temperature.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.735-746
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• 2002

The task of plastic theory is twofold: first, to set up relationships between stress and strain that adequately describe the observed plastic deformation of metals, and second, to develop techniques for using these relationships in studying of the mechanics of metal forming processes, and the anlaysis and design of structures. One of the major problems in the theory of plasticity is to describe the behavior of work-hardening materials in the plastic range for complex loading histories. This can be achieved by formulating constitutive laws either in the integral or differential forms. To adequately predict the response of steel members during cyclic loading, the hardening rule must account for the features of cyclic stress-strain behavior. Neithe of the basic isotropic and kinematic hardening rules is suitable for describing cyclic streess-strain behavior, although a kinematic hardening rule describes the nearly linear portions of the stabilized hystersis loops. There is also a limited expansion of the yield surface as predicted by the isotropic hardening rule. Strong ground motions or wind gusts affect the complex and nonproportional loading histories in the inelastic behavior of structues rather than the proportional loading. Nonproportional loading is defined as externally applied forces on the structure, with variable ratios during the entire loading history. This also includes the rate of time-dependency of the loads. For nonproportional loading histories, unloading may take place along a chord instead of the radius of the load surface. In such cases, the shape of the stress-strain curve has to be determined experimentally for all non-radial loading conditions. The plasticity models including two surface models ae surveyed based on a yield surface and a bound surface that represent a state of maximum stress. This paper is concerned with the improvement of a plasticity models of the two-surface type for structural steel. This is follwed by an overview of plasticity models on structural steel. Finally the need for further research is identified.