• Advances in concrete construction
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• v.10 no.6
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• pp.537-546
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• 2020

Exterior walls in buildings are exposed to various forms of thermal loads, which depend on the positions of walls. Therefore, one of the efficient methods for improving the energy competence of buildings is improving the thermal properties of insulation plaster mortar. In this study, lightweight fine aggregate (LWFA) and micro rubber ash (MRA) from recycled tires were used as partial replacements for sand. The flow ability, unit weight, compressive strength, tensile strength, thermal conductivity (K-value), drying shrinkage and microstructure scan of lightweight rubberized mortar (LWRM) were investigated. Ten mixtures of LWRM were prepared as follows: traditional cement mortar (control mixture); three mixes with different percentages of LWFA (25%, 50% and 75%); three mixes with different percentages of MRA (2.5%, 5% and 7.5%); and three mixes consisting both types with determined ratios (25% LWFA+5% MRA, 50% LWFA+5% MRA and 75% LWFA+5% MRA). The flow ability of the mortars was 22±2 cm, and LWRM contained LWFA and MRA. The compressive and tensile strength decreased by approximately 64% and 57%, respectively, when 75% LWFA was used compared with those when the control mix was used. The compressive and tensile strength decreased when 5% MRA was used. By contrast, mixes with determined ratios of LWFA and MRA affected reduced unit weight, K-value and dry shrinkage.

• Steel and Composite Structures
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• v.38 no.5
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• pp.599-615
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• 2021

The ultimate strength behaviour of sandwich composite beams with J-hooks and normal weight concrete (SCSSBJNs) are studied through two-point loading tests on ten full-scale SCSSBJNs. The test results show that the SCSSBJN with different parameters under two-point loads exhibits three types of failure modes, i.e., flexure, shear, and combined shear and flexure mode. SCSSBJN failed in different failure modes exhibits different load-deflection behaviours, and the main difference of these three types of behaviours exist in their last working stages. The influences of thickness of steel faceplate, shear span ratio, concrete core strength, and spacing of J-hooks on structural behaviours of SCSSBJN are discussed and analysed. These test results show that the failure mode of SCSSBJN was sensitive to the thickness of steel faceplate, shear span ratio, and concrete core strength. Theoretical models are developed to estimate the cracking, yielding, and ultimate bending resistance of SCSSBJN as well as its transverse cross-sectional shear resistance. The validations of predictions by these theoretical models proved that they are capable of estimating strengths of novel SCSSBJNs.

• Advances in aircraft and spacecraft science
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• v.9 no.3
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• pp.263-278
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• 2022

The time-varying structural reliability of an aeroelastic launch vehicle subjected to stochastic parameters is investigated. The launch vehicle structure is under the combined action of several stochastic loads that include aerodynamics, thrust as well as internal combustion pressure. The launch vehicle's main body structural flexibility is modeled via the normal mode shapes of a free-free Euler beam, where the aerodynamic loadings on the vehicle are due to force on each incremental section of the vehicle. The rigid and elastic coupled nonlinear equations of motion are derived following the Lagrangian approach that results in a complete aeroelastic simulation for the prediction of the instantaneous launch vehicle rigid-body motion as well as the body elastic deformations. Reliability analysis has been performed based on two distinct limit state functions, defined as the maximum launch vehicle tip elastic deformation and also the maximum allowable stress occurring along the launch vehicle total length. In this fashion, the time-dependent reliability problem can be converted into an equivalent time-invariant reliability problem. Subsequently, the first-order reliability method, as well as the Monte Carlo simulation schemes, are employed to determine and verify the aeroelastic launch vehicle dynamic failure probability for a given flight time.

• Geomechanics and Engineering
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• v.32 no.6
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• pp.567-581
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• 2023

Enhanced vertical load capacity of the ground reinforced with the stone columns drew great attention by the researchers as it deals with many of the geotechnical difficulties associated with the weak ground. Recently, it has been found that the stone columns are also prone to fail under the shear load when employed beneath the embankments or the foundations susceptible to lateral loads. In this study, the effect of various encasement conditions on the lateral deflection of stone columns is investigated. A method of dual layers of encasement has been introduced and its the effect on lateral load capacity of the stone columns has been compared with those of the single encased stone column and the un-encased stone columns. Large shear box tests were utilised to generate the shear deformation on the soil system under various normal pressure conditions. The stiffness of the soil-stone column combined system has been compared for various cases of encasement conditions with different diameters. When subjected to lateral deformation, the encased columns outperformed the un-encased stone columns installed in loose sand. Shear stress resistance is up to 1.7 times greater in dual-layered, encased columns than in unencased columns. Similarly, the secant modulus increases as the condition changes from an unencased stone column to single-layer encasement and then to dual-layer encasement, indicating an improvement in the overall soil-stone column system.

• Steel and Composite Structures
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• v.47 no.2
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• pp.289-296
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• 2023

The failure of a thin-walled tube was studied in this paper based on three failure models. Both proportional and non-proportional loading paths were applied. Proportional loading consisted of combined tension-torsion. Cyclic non-proportional loading was also applied. It was a circular out-of-phase axial-shear stress loading path. The third loading path was a combination of a constant internal pressure and a bending moment. The failure models under study were equivalent plastic strain, modified Mohr-Coulomb (Bai-Wierzbicki) and Tearing parameter models. The elasto-plastic analysis was conducted using J2 criterion and nonlinear kinematic hardening. The return mapping algorithm was employed to numerically solve the plastic flow relations. The effects of the hydrostatic stress on the plastic flow and the stress triaxiality parameter on the failure were discussed. Each failure model under study was utilized to predict failure. The failure loads obtained from each model were compared with each other. The equivalent plastic strain model was independent from the stress triaxiality parameter, and it predicted the highest failure load in the bending problem. The modified Mohr-Coulomb failure model predicted the lowest failure load for the range of the stress triaxiality parameter and Lode's angle.

• Journal of Ocean Engineering and Technology
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• v.37 no.4
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• pp.164-171
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• 2023

Vibration and noise must be considered to maximize the efficiency of a yaw system and reduce the fatigue load acting on a wind turbine. This study investigated a method for analyzing yaw-system vibration based on the change in the load-duration distribution (LDD). A substructure synthesis method was combined with a planetary gear train rotational vibration model and finite element models of the housing and carriers. For the vibration excitation sources, the mass imbalance, gear mesh frequency, and bearing defect frequency were considered, and a critical speed analysis was performed. The analysis results showed that the critical speed did not occur within the operating speed range, but a defect occurred in the bearing of the first-stage planetary gear system. It was found that the bearing stiffness and first natural frequency increased with the LDD load. In addition, no vibration occurred in the operating speed range under any of the LDD loads. Because the rolling bearing stiffness changed with the LDD, it was necessary to consider the LDD when analyzing the wind turbine vibration.

• Geomechanics and Engineering
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• v.33 no.3
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• pp.243-259
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• 2023

Turkey is one of the most important earthquake regions in Europe. This region has been exposed to many earthquakes of different magnitudes from past to present. It is of great importance to determine the dynamic properties of the soils for structures to be built in earthquake zones. In order to minimize the damages that may occur, the behavior of the soils under repeated loads should be known and taken into consideration in the design. In this study, 4 different point borings were taken near active fault lines in the North Anatolian fault zone (NAFZ). In order to determine the dynamic parameters of soils, both dynamic triaxial (TRX) and resonant column (RC) tests were carried out on undisturbed samples at every 5 m. As a result of the experiments, V_s and G_max values were obtained from the field and differences were determined. The dynamic behavior of the soil was examined at varying depths with the comparison of reference models in the literature and compatible results were obtained. Finally, the behavior at the transition region is highlighted. As a result, three shear modulus and dumping ratio models have been proposed for clay soils to be used in different soil conditions.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.21 no.4
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• pp.503-516
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• 2023

A transfer cask serves as the container for transporting and handling canisters loaded with spent nuclear fuels from light water reactors. This study focuses on a cylindrical transfer cask, standing at 5,300 mm with an external diameter of 2,170 mm, featuring impact limiters on the top and bottom sides. The base of the cask body has an openable/closable lid for loading canisters with storage modules. The transfer cask houses a canister containing spent nuclear fuels from lightweight reactors, serving as the confinement boundary while the cask itself lacks the confinement structure. The objective of this study was to conduct a structural analysis evaluation of the transfer cask, currently under development in Korea, ensuring its safety. This evaluation encompasses analyses of loads under normal, off-normal, and accident conditions, adhering to NUREG-2215. Structural integrity was assessed by comparing combined results for each load against stress limits. The results confirm that the transfer cask meets stress limits across normal, off-normal, and accident conditions, establishing its structural safety.

• Structural Engineering and Mechanics
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• v.88 no.4
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• pp.379-387
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• 2023

Wind and earthquake loads may cause strong vibrations in large-span cable-stayed bridges, leading to the inability of the bridge to operate normally. An improved Pounding Tuned Mass Damper (PTMD) system was designed to improve the safety of the large-span cable-stayed bridge. The vibration control effect of the improved PTMD system on the large-span cablestayed bridge under the combined action of earthquake-wind-traffic was studied. Furthermore, the impact of different parameters on the vibration suppression performance of the improved PTMD system was analyzed. The numerical results indicate that the PTMD system is very effective in suppressing the displacements of the bridge caused by both the traffic-wind coupling and traffic-earthquake coupling. Moreover, the number, mass ratio, pounding stiffness, and gap values have a significant influence on the vibration suppression performance of the improved PTMD system. When the number of PTMD is increased from 3 to 9, the vibration reduction ratio of the vertical displacement is increased from 25.39% to 48.05%. As the mass ratio changes from 0.5% to 2%, the vibration reduction ratio increases significantly from 22.23% to 53.30%.

• Structural Engineering and Mechanics
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• v.90 no.2
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• pp.177-187
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• 2024

In this study, compared two distinct estimation methods (stress charts and regression equations) proposed by the Indian road congress design guideline (IRC:58-2015) to determine flexural stress in Jointed Plain Concrete Pavement (JPCP). The occurrence of critical flexural stresses in pavement slabs is due to the combined effects of wheel loads and temperature. These stresses depend on various factors such as material properties of concrete, soil-subgrade strength, loading, and geometric properties of the slab. In order to account for the practical variability of these factors, critical edge stresses are determined using both methods and compared considering tied concrete shoulder. IRC:58 (2015) suggests, the stresses calculated by both the procedures should provide the same results. However, when these stresses are compared for the same configurations and same loading conditions, large variations are observed. The effect of tied concrete shoulder on reduction in critical edge stress is observed. Based on the study, certain important conclusions and recommendations are presented.