• PNF and Movement
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• v.18 no.3
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• pp.415-424
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• 2020

Purpose: This study aimed to compare changes in abdominal muscle thickness in different standing postures with a handheld load between subjects with and without chronic low back pain (CLBP). Methods: Twenty subjects with CLBP and 20 controls participated in this study. Ultrasound imaging was used to assess the changes in the thickness of the transverse abdominis (TrA), internal oblique (IO), and external oblique (EO) muscles. Muscle thickness in three different standing postures (standing at rest, standing with loads, standing with lifting loads) was compared with the muscle thickness at rest in the supine position and was expressed as a percentage of change in the thickness of the muscle. Results: While standing with loads, the change in IO muscle thickness in the CLBP patients increased more significantly than in the pain-free controls (p < 0.05). The standing with lifting loads posture showed a significant increase in the change in thickness of the TrA compared with the standing with loads posture (p < 0.05). In addition, the standing with lifting loads posture showed a significant decrease in the change in the thickness of the EO when compared with the standing with loads posture (p < 0.05). Conclusion: The automatic activity of the IO muscle in subjects with CLBP increased more than that of the pain-free controls in the standing with loads posture. These findings suggest that IO muscle function may be altered in those with CLBP while standing with loads. Additionally, TrA the activation level was found to be associated with increased postural demand caused by an elevated center of mass.

• Geomechanics and Engineering
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• v.36 no.6
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• pp.575-587
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• 2024

The contact pressure between the surrounding rock and the support is an important indicator of the surrounding rock pressure. There has been a bottleneck in the prediction of contact loads between surrounding rock and primary support in deep-buried mountain tunnels. The main reason is that a reliable method wasn't existed to quantify the contact loads. This study had been taken into account the flexible support role of the primary support, and the fitting curve of surrounding rock deformation for dynamic tunnel construction was proposed. New formulas for the calculation of contact loads between surrounding rock and primary support were obtained by inversion. Comparative analysis of the calculation results with numerical simulation verified the reliability of the calculation method in this study. It can be seen from the analyses that the contact load between surrounding rock and primary support increases, remains unchanged and decreases during acceleration, uniform velocity and deceleration, respectively, and the deformation of the surrounding rock in the acceleration and deceleration stages cannot completely converted into contact loads. The contact loads between surrounding rock and primary support of medium-strength and weak surrounding rock tunnels are generally within 150 kPa and 1 MPa, respectively. For tunnels with weak surrounding rock, advanced support can be installed to reduce the unique release coefficient λ₀ and the value of the constant D, with the purpose of reducing the contact loads between surrounding rock and primary support. Changes in support parameters have a small effect on the contact loads between surrounding rock and primary support, but increase or decrease the safety factor, resulting in a waste of resources or a situation that threatens the safety of the support. The results of this research provide guidance for the prediction of contact loads between surrounding rock and primary support for dynamic tunnel construction.

• Structural Engineering and Mechanics
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• v.50 no.3
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• pp.287-304
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• 2014

A computer based iterative numerical procedure has been developed to analyse reinforced high strength concrete columns subjected to horizontal wave loads and eccentric vertical load by taking the material, geometrical and wave load non-linearity into account. The behaviour of the column has been assumed, to be represented by Moment-Thrust-Curvature relationship of the column cross-section. The formulated computer program predicts horizontal load versus deflection behaviour of a column up to failure. The developed numerical model has been applied to analyse several column specimens of various slenderness, structural properties and axial load ratios, tested by other researchers. The predicted values are having a better agreement with experimental results. A simplified user friendly hydrodynamic load model has been developed based on Morison equation supplemented with a wave slap term to predict the high frequency non-linear impulsive hydrodynamic loads arising from steep waves, known as ringing loads. A computer program has been formulated based on the model to obtain the wave loads and non-dimensional wave load coefficients for all discretised nodes, along the length of column from instantaneous free water surface to bottom of the column at mud level. The columns of same size and material properties but having different slenderness ratio are analysed by the developed numerical procedure for the simulated wave loads under various vertical thrust. This paper discusses the results obtained in detail and effect of slenderness in resisting wave loads under various vertical thrust.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.3
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• pp.421-425
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• 2018

The icebreaking research vessel ARAON performed ice field tests during her 2016 Arctic voyage. The ship is subjected to ice loads through ice-ship interaction processes. Local ice load acting on ARAON's bow section was measured by using stain gauges installed on the inner hull plates and transverse frames of bow section. In this paper the local ice loads at transverse frames estimated from shear strain data were compared to ice loads from hull plate pressures by using the influence coefficient method. In addition to the analysis of local ice loads, the characteristics of peak ice loads with the ship speed is also discussed. It is recommended that the local ice loads estimated by calculating shear forces acting on transverse frames may be useful in estimating local ice loads on the hull of ship.

• Steel and Composite Structures
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• v.25 no.3
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• pp.287-298
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• 2017

The present study aims to determine the structural response of full scaled rectangular columns under both of vertical and lateral loads using numerical methods. In the study, the composite columns considering full concrete filled circular steel tube (FCFRST) and concrete filled double-skin rectangular steel tube (CFDSRST) section types are numerically modelled using ANSYS software. Vertical and lateral loads are applied to models to assess the structural response of the composite elements. Also similar investigations are done for reinforced concrete rectangular (RCR) columns to compare the results with those of composite elements. The analyses of the systems are statically performed for both linear and nonlinear materials. In linear static analyses, both of vertical and lateral loads are applied to models as only one step. However in nonlinear analyses, while vertical loads are applied to model as only one step, lateral loads are applied to systems as step by step. The displacement and stress changes in some critical nodes and sections and contour diagrams are reported by graphs and figures. At the end of the study, it is demonstrated that the nonlinear models reveal more accurate result then those of linear models. Also, it is highlighted that composite columns provide more and more safety, ductility compared to reinforced concrete column.

• Computational Structural Engineering
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• v.5 no.3
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• pp.113-118
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• 1992

The live loads acting on structures are generally computed in terms of equivalent uniformly distributed loads for the simplicity in design process. The loads, therefore, tend to decrease with increasing influence area in both load intensity and variance. Since multi-story column loads result from accumulation of loadings action on several different floors, its influence area becomes wider and lifetime maximum decreases. In the design codes proposing the design loads according to types of structural members(i.e., slabs, beams, columns), rather than the change of influence area, some proper reduction factors are given for columns which support more than one floor. Using the live load models developed for columns supporting single floor, in this study, the probabilistic characteristics of multi-story column loads are analyzed. In addition reduction factors given for multistory columns in current practice are calibrated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.1
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• pp.48-54
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• 2004

Generally, structural optimization is carried out based on external static loads. All forces have dynamic characteristics in the real world. Mathematical optimization with dynamic loads is extremely difficult in a large-scale problem due to the behaviors in the time domain. In practical applications, it is customary to transform the dynamic loads into static loads by dynamic factors, design codes, and etc. But the optimization results with the unreasonably transformed loads cannot give us good solutions. Recently, a systematic transformation has been proposed as an engineering algorithm. Equivalent static loads are made to generate the same displacement field as the one from dynamic loads at each time step of dynamic analysis. Thus, many load cases are used as the multiple loading conditions which are not costly to include in modem structural optimization. In this research, the proposed algorithm is applied to the optimization of flexible multibody dynamic systems. The equivalent static load is derived from the equations of motion of a flexible multibody dynamic system. A few examples that have been solved before are solved to be compared with the results from the proposed algorithm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.8
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• pp.1291-1296
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• 2017

Single-phase and three-phase load can be used together in 3-phase 4-wire system. Single-phase and three-phase loads can be classified as linear loads without harmonics and nonlinear with harmonics. Single-phase linear loads are linear loads such as lamps and heat, and single-phase nonlinear loads are power converters such as rectifiers. It is recommended that the distribution of loads in the 3-phase, 4-wire distribution lines be evenly distributed within a certain range. However, harmonic currents generated in a nonlinear load flow on the neutral line and affect the phase current magnitude. The difference in the magnitude of the individual phase current due to the influence of the harmonic current present in the neutral line can produce a difference in current and load unbalance. In this study, current unbalance ratio and load unbalance ratio which can occur when a combination of linear and nonlinear loads are applied to 3-phase 4-wire distribution line are calculated.

• Structural Engineering and Mechanics
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• v.54 no.1
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• pp.149-168
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• 2015

In the bolted connections, bolt placements are generally described and are generally made in the direction of design effects and in the perpendicular direction to design effects. In these both directions, the reliability of the distance of bolts to the edges of connection plate and the distance of bolts to each other is investigated for high strength steel connections built up with high strength bolts in this study. For this purpose, simple SL (bearing type shear connection) and SLP (bearing type shear connection for body-fit bolts) type steel connections with St 52 grade steel plates with 8 different thicknesses and with 8.8D grade high strength bolts (HV) were constituted and analyzed under H (Dead Loads+Live Loads+Snow Loads+Roof Loads) and HZ (H Loads+Wind Loads+Earthquake Loads) loadings. Geometric properties, material properties and design actions were taken as random variables. Monte Carlo Simulation method was used to compute failure risk and the first order second moment method was used to determine the reliability indexes of those different distances describing the placement of bolts. Results obtained from computations have been presented in graphics and in a Table. Then, they were compared with some values proposed by some structural codes. Finally, new equations were constituted for minimum and maximum values of distances describing bolt placement by regression analyses performed on those results.

• Wind and Structures
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• v.26 no.6
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• pp.343-354
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• 2018

A realistic FEM structural model is developed to predict the behavior, load transfer, force distribution and performance of a riverine platform under earthquake and environmental loads. The interaction between the transfer plate and the piles supporting the platform is investigated. Transfer plate structures have the ability to redistribute the loads from the superstructure above to piles group below, to provide safe transits of loads to piles group and thus to the soil, without failure of soil or structural elements. The distribution of piles affects the distribution of stress on both soil and platform. A materially nonlinear earthquake response spectrum analysis was performed on this riverine platform subjected to earthquake and environmental loads. A fixed connection between the piles and the platform is better in the design of the piles and the prospect of piles collapse is low while a hinged connection makes the prospect of damage high because of the larger displacements. A fixed connection between the piles and the platform is the most demanding case in the design of the platform slab (transfer plate) because of the high stress values developed.