• Steel and Composite Structures
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• 제27권2호
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• pp.217-227
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• 2018

This paper utilizes 3D FEM to provide deeper insights about the structural behaviour of a 6.1 m span steel culvert, which was previously tested under extreme loading. The effect of different input parameters pertaining to the backfill soil has been investigated, where the structural response is compared to field measurements. The interface choice between the steel and soil materials was also studied. The results enabled to realize the major influence of the friction angle on the load effects. Moreover, the analyses showed some differences concerning the estimation of failure load, whereas reasons beyond this outcome were arguably presented and discussed.

• 한국구조물진단유지관리공학회 논문집
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• 제2권1호
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• pp.129-135
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• 1998

The characteristic of load-distribution is investigated by using nonlinear analysis with a field loading test of existing bridge In this study, nonlinear load-distribution technique for quantitative analysis was adopted. The results were compared with linear solution technique with data from failure test at existing RCT-girder bridge and examine the adequacy of the failure mode. The results of this study showed that the linear solution technique and the proposed nonlinear solution technique agreed well in linear region but did not matched well in nonlinear region because of load-redistribution, and that the effect of load-redistribution was considered to analysis of nonlinear region by linear solution.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.4146-4158
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• 2023

This paper proposes a combined plastic and creep constitutive model of A533B1 pressure vessel steel to simulate progressive deformation of nuclear pressure vessels under severe accident conditions. To develop the model, recent tensile test data covering a wide range of temperatures (from RT to 1,100 ℃) and strain rates (from 0.001%/s to 1.0%/s) was used. Comparison with experimental data confirms that the proposed combined plastic and creep model can well reflect effects of temperature and strain rate on tensile behaviour up to failure. In the companion paper (Part II), the proposed model will be used to simulate OECD lower head failure (OLHF) test data.

• Steel and Composite Structures
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• 제38권5호
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• pp.563-582
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• 2021

The present study experimentally and analytically investigated the push-out behaviour of H-shaped steel section embedded in ultrahigh-performance fibre-reinforced concrete (UHPFRC). The effect of significant parameters such as the concrete types, fibre content, embedded steel length, transverse reinforcement ratio and concrete cover on the bond stress, development of bond stress along the embedded length and failure mechanism has been reported. The test results show that the bond slip behaviour of steel-UHPFRC is different from the bond slip behaviour of steel-normal concrete and steel-high strength concrete. The bond-slip curves of steel-normal concrete and steel-high strength concrete exhibit brittle behaviour, and the bond strength decreases rapidly after reaching the peak load, with a residual bond strength of approximately one-half of the peak bond strength. The bond-slip curves of steel-UHPFRC show an obvious ductility, which exhibits a unique displacement pseudoplastic effect. The residual bond strength can still reach from 80% to 90% of the peak bond strength. Compared to steel-normal concrete, the transverse confinement of stirrups has a limited effect on the bond strength in the steel-UHPFRC substrate, but a higher stirrup ratio can improve cracking resistance. The experimental campaign quantifies the local bond stress development and finds that the strain distribution in steel follows an exponential rule along the steel embedded length. Based on the theory of mean bond and local bond stress, the present study proposes empirical approaches to predict the ultimate and residual bond resistance with satisfactory precision. The research findings serve to explain the interface bond mechanism between UHPFRC and steel, which is significant for the design of steel-UHPFRC composite structures and verify the feasibility of eliminating longitudinal rebars and stirrups by using UHPFRC in composite columns.

• Asian-Australasian Journal of Animal Sciences
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• 제18권10호
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• pp.1403-1406
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• 2005

The present study was undertaken to study the effect of thermal stress on sexual behaviour of superovulated ewes. Fourteen adult Bharat Merino ewes with an average body weight of 29.4${\pm}$2.34 kg were randomly allocated into two groups of 7 each. All the animals were grazed on natural pasture in the morning and evening hours and housed in shed during night. Animals of Group-1 were housed in shed from 10:00 to 16:00 h while the animals of Group-2 were exposed to thermal stress in a hot chamber ($40^{\circ}C$ /6 h/day). All the animals were offered drinking water once a day at 16:30 h. Meteorological observations i.e. dry bulb, wet bulb, minimum and maximum temperature were recorded daily inside the shed as well as in hot chamber throughout the experimental period. For superovulation of animals, standard protocol developed at the Institute, using FSH (Ovagen 5.4 mg in eight injections) and PMSG (200 IU) was followed. Various sexual behaviour parameters (circling, tail fanning, head turning, standing and approaching to ram) and estrus incidence (onset of estrus and estrus duration) were observed in both the groups. The different estrus symptoms were graded subjectively on arbitrary scale of 0-5 where 0 representing no sexual behaviour (0%) and 5 representing maximum intensity in sexual behaviour (100%). Estrus was detected with the help of a marked aproned ram of proven vigor at six hourly intervals. The average percent values for sexual behaviour parameters recorded in Group-1 and Group-2 animals were 53.7${\pm}$3.76 vs. 41.1${\pm}$2.18 for circling, 71.8${\pm}$5.42 vs. 49.0${\pm}$4.41 for tail fanning, 64.7${\pm}$3.30 vs. 44.5${\pm}$4.34 for head turning, 90.1${\pm}$3.16 vs. 75.8${\pm}$4.02 for standing and 63.8${\pm}$4.8 vs. 41.9${\pm}$4.58 for approaching to ram. Animals exposed to thermal stress had significantly lower values of these sexual behaviour parameters. The animals kept in shed exhibited estrus earlier (25.4${\pm}$1.12 h) and duration was higher (37.7${\pm}$1.59 h) as compared to animals exposed to thermal stress i.e. 30.6${\pm}$1.16 h and 31.7${\pm}$3.57 h, respectively. The findings of the study indicate that thermal stress reduces the intensity of sexual behaviour in ewes and may result in failure of the animal to mate and conceive.

• Structural Engineering and Mechanics
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• 제71권3호
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• pp.211-221
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• 2019

To study the eccentric compression behavior of ultra-high performance fiber reinforced concrete (UHPFRC) columns, six UHPFRC columns and one high-strength concrete (HSC) column were tested. Variation parameters include load eccentricity, volume of steel fibers and stirrup ratio. The crack pattern, failure mode, bearing capacity, and deformation of the specimens were studied. The results showed that the UHPFRC columns had different failure modes. The large eccentric compression failure mode was the longitudinal tensile reinforcements yielded and many horizontal cracks appeared in the tension zone. The small eccentric compression failure mode was the longitudinal compressive reinforcements yielded and vertical cracks appeared in the compressive zone. Because of the bridging effect of steel fibers, the number of cracks significantly increased, and the width of cracks decreased. The load-deflection curves of the UHPFRC columns showed gradually descending without sudden dropping, indicating that the specimens had better deformation. The finite element (FE) analysis was performed to stimulate the damage process of the specimens with monotonic loading. The concrete damaged plasticity (CDP) model was adopted to characterize the behaviour of UHPFRC. The contribution of the UHPFRC tensile strength was considered in the bearing capacity, and the theoretical calculation formulas were derived. The theoretical calculation results were consistent with the test results. This research can provide the experimental and theoretical basis for UHPFRC columns in engineering applications.

• Structural Engineering and Mechanics
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• 제67권5호
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• pp.493-504
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• 2018

In this paper, the tensile failure behaviour of transversally bedding layers was numerically simulated by using particle flow code in two dimensions. Firstly, numerical model was calibrated by uniaxial, Brazilian and triaxial experimental results to ensure the conformity of the simulated numerical model's response. Secondly, 21 circular models with diameter of 54 mm were built. Each model contains two transversely bedding layers. The first bedding layer has low mechanical properties, less than mechanical properties of intact material, and second bedding layer has high mechanical properties, more than mechanical properties of intact material. The angle of first bedding layer, with weak mechanical properties, related to loading direction was $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $75^{\circ}$ and $90^{\circ}$ while the angle of second layer, with high mechanical properties, related to loading direction was $90^{\circ}$, $105^{\circ}$, $120^{\circ}$, $135^{\circ}$, $150^{\circ}$, $160^{\circ}$ and $180^{\circ}$. Is to be note that the angle between bedding layer was $90^{\circ}$ in all bedding configurations. Also, three different pairs of the thickness was chosen in models; i.e., 5 mm/10 mm, 10 mm/10 mm and 20 mm/10 mm. The result shows that In all configurations, shear cracks develop between the weaker bedding layers. Shear cracks angel related to normal load change from $0^{\circ}$ to $90^{\circ}$ with increment of $15^{\circ}$. Numbers of shear cracks are constant by increasing the bedding thickness. It's to be note that in some configuration, tensile cracks develop through the intact area of material model. There is not any failure in direction of bedding plane interface with higher strength.

• Structural Engineering and Mechanics
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• 제65권6호
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• pp.679-687
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• 2018

In composite materials technology, the fiber-reinforced polymers (FRP) have opened up new horizons in infrastructural engineering field for strengthening existing structures and components of structure. The Carbon fiber reinforced polymer (CFRP) sheets are well suited for RC columns to this application because of their high strength to weight ratio, good fatigue properties and excellent resistance to corrosion. The main focus of present experimental work is to investigate effect of shapes on axial behavior of CFRP wrapped RC columns having same cross-sectional area and slenderness ratio. The CFRP volumetric ratio and percentage of steel are also adopted constant for all the test specimens. A total of 18 RC columns with slenderness ratio four were cast. Nine columns were control and the rest of nine columns were strengthened with one layer of CFRP wrap having 35 mm of corner radius. Columns confined with CFRP wrap were designed using IS: 456:2000 and ACI 440.2R.08 provisions. All the test specimens were loaded for axial compression up to failure and failure pattern for each shaped column was investigated. All the experimental results were compared with analytical values calculated as per the ACI-440.2R-08 code. The test results clearly demonstrated that the axial behavior of CFRP confined RC columns is affected with the change in shapes. The axial deformation is higher in CFRP wrapped RC circular column as compared to square and rectangular columns. Stress-strain behaviour revealed that the yield strength gained from CFRP confinement was significant for circular columns as compare to square and rectangular columns. This behaviour may be credited due to effect of shape on lateral deformation in case of CFRP wrapped circular columns at effective confinement action.

• Structural Engineering and Mechanics
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• 제65권3호
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• pp.315-325
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• 2018

This paper predicts the flexural behaviour of reinforced concrete (RC) beams strengthened with a precast strip of ultra-high performance fiber-reinforced concrete (UHPFRC). In the first phase, ultimate load capacity of preloaded and strengthened RC beams by UHPFRC was predicted by using various analytical models available in the literature. RC beams were preloaded under static loading approximately to 70%, 80% and 90% of ultimate load of control beams. The models such as modified Kaar and sectional analysis predicted the ultimate load in close agreement to the corresponding experimental observations. In the second phase, the famous fatigue life models such as Papakonstantinou model and Ferrier model were employed to predict the number of cycles to failure and the corresponding deflection. The models were used to predict the life of the (i) strengthened RC beams after subjecting them to different pre-loadings (70%, 80% and 90% of ultimate load) under static loading and (ii) strengthened RC beams after subjecting them to different preloading cycles under fatigue loading. In both the cases precast UHPFRC strip of 10 mm thickness is attached on the tension face. It is found that both the models predicted the number of cycles to failure and the corresponding deflection very close to the experimental values. It can be concluded that the models are found to be robust and reliable for cement based strengthening systems also. Further, the Wang model which is based on Palmgren-Miner's rule is employed to predict the no. of cycles to failure and it is found that the predicted values are in very good agreement with the corresponding experimental observations.

• Steel and Composite Structures
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• 제42권1호
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• pp.1-22
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• 2022

In cold-formed steel (CFS) structures, such as trusses, transmission towers and portal frames, the use of back-to-back built-up CFS unequal angle sections are becoming increasingly popular. In such an arrangement, intermediate welds or screw fasteners are required at discrete points along the length, preventing the angle sections from buckling independently. Limited research is available in the literature on axial strength of back-to-back built-up CFS unequal angle sections. The issue is addressed herein. This paper presents an experimental investigation reported by the authors on back-to-back built-up CFS unequal angle sections with intermediate stiffeners under axial compression. The load-axial shortening behaviour along with the deformed shapes at failure are reported. A nonlinear finite element (FE) model was then developed, which includes material non-linearity, geometric imperfections and modelling of intermediate fasteners. The FE model was validated against the experimental test results, which showed good agreement, both in terms of failure loads and deformed shapes at failure. The validated finite element model was then used for the purpose of a parametric study comprising 96 models to investigate the effect of longer to shorter leg ratios, stiffener provided in the longer leg, thicknesses and lengths on axial strength of back-to-back built-up CFS unequal angle sections. Four different thicknesses and seven different lengths (stub to slender columns) with three overall widths to the overall depth (B/D) ratios were investigated in the parametric study. Axial strengths obtained from the experimental tests and FE analyses were used to assess the performance of the current design guidelines as per the Direct Strength Method (DSM); obtained comparisons show that the current DSM is conservative by only 7% and 5% on average, while predicting the axial strengths of back-to-back built-up CFS unequal angle sections with and without the stiffener, respectively.