• Geomechanics and Engineering
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• 제6권2호
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• pp.195-211
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• 2014

Stone columns (or granular column) have been used to increase the load carrying capacity and accelerating consolidation of soft soil. Recently, the geosynthetic reinforced stone column technique has been developed to improve the load carrying capacity of the stone column. In addition, reinforcement prevents the lateral squeezing of stone in to surrounding soft soil, helps in easy formation of stone column, preserve frictional properties of aggregate and drainage function of the stone column. This paper investigates the improvement of load carrying capacity of isolated ordinary and geotextile reinforced sand column through field load tests. Tests were performed with different reinforcement stiffness, diameter of sand column and reinforcement length. The results of field load test indicated an improved load carrying capacity of geotextile reinforced sand column over ordinary sand column. The increase in load carrying capacity depends upon the sand column diameter, stiffness of reinforcement and reinforcement length. Also, the partial reinforcement length about two to four time's sand column diameter from the top of the column was found to significant effect on the performance of sand column.

• Geomechanics and Engineering
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• 제19권1호
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• pp.71-78
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• 2019

Massive investments are going on to promote and build transportation infrastructure all across the globe with the challenges being more than budgetary. Sandy soils which are predominant in coastal and border areas in India have typical characteristics. The shear strength of such soil is very low which makes it difficult for any kind of geotechnical construction and hence soil stabilization needs to be carried out for such soil conditions. The use of geocells is one of the most economical methods of soil improvement which is used to increase strength and stiffness and reduce the liquefaction potential of the soil. The use of geocells in stabilizing desert sand and results from a series of plate load test on unreinforced soil and geocell reinforced homogenous sand beds are presented in the present study. It also compares the field results using various load class vehicles like heavy load military vehicles on geocell reinforced soils with the experimental results and comes out with the fact that the proposed technique increases the strength and stiffness of sandy soil considerably and provides a solution for preventing settlement and subsidence.

• Tribology and Lubricants
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• 제33권2호
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• pp.65-70
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• 2017

In vertical hydro/hydraulic power turbine-generator applications, traditionally, cylindrical turbine guide bearings (TGBs) are widely used to provide turbine runner shafts with smooth rotation guides and supports. All existing cylindrical TGBs with simple plain pads have drawbacks such as having no pressure generation and film stiffness at the no-load condition and in addition, at the low-load/low-eccentricity condition, having very low film stiffness values and lacking design credibility in the stiffness values themselves. In this paper, in order to fundamentally improve the low-load/low-eccentricity performance of conventional cylindrical TGBs and thus enhance their design-application availability and usefulness, we propose to introduce a rotation-directional leading-edge taper to each partitioned pad, i.e., a pad leading-edge taper. We perform a design analysis of lubrication performance on $4-Pad{\times}4-Row$ cylindrical TGBs to verify an engineering/technical usefulness of the proposed pad leading-edge taper. Analysis results show that by introducing the leading-edge taper to each pad of the cylindrical TGB one can expect a constant high average direct stiffness with a high degree of design credibility, regardless of load value, even at the low-load/low-eccentricity condition and also control the average direct stiffness value by exploring the taper height as a design parameter. Therefore, we conclude that the proposed pad leading-edge tapers are greatly effective in more accurately predicting and controlling rotordynamic characteristics of vertical hydro-power turbine-generator rotor-bearing systems to which cylindrical TGBs are applied.

• Smart Structures and Systems
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• 제13권2호
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• pp.219-233
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• 2014

In a companion paper, Pasala and Nagarajaiah analytically and experimentally validate the Adaptive Length Pendulum Smart Tuned Mass Damper (ALP-STMD) on a primary structure (2 story steel structure) whose frequencies are time invariant (Pasala and Nagarajaiah 2012). In this paper, the ALP-STMD effectiveness on a primary structure whose frequencies are time varying is studied experimentally. This study experimentally validates the ability of an ALP-STMD to adequately control a structural system in the presence of real time changes in primary stiffness that are detected by a real time observer based system identification. The experiments implement the newly developed Adaptive Length Pendulum Smart Tuned Mass Damper (ALP-STMD) which was first introduced and developed by Nagarajaiah (2009), Nagarajaiah and Pasala (2010) and Nagarajaiah et al. (2010). The ALP-STMD employs a mass pendulum of variable length which can be tuned in real time to the parameters of the system using sensor feedback. The tuning action is made possible by applying a current to a shape memory alloy wire changing the effective length that supports the damper mass assembly in real time. Once a stiffness change in the structural system is detected by an open loop observer, the ALP-STMD is re-tuned to the modified system parameters which successfully reduce the response of the primary system. Significant performance improvement is illustrated for the stiffness modified system, which undergoes the re-tuning adaptation, when compared to the stiffness modified system without adaptive re-tuning.

• Clinics in Shoulder and Elbow
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• 제26권4호
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• pp.390-396
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• 2023

Background: The subacromial (SA) space is a commonly used injection site for treatment of impingement syndrome. For shoulder stiffness, glenohumeral (GH) injections are commonly performed. However, in cases of impingement syndrome with mild shoulder stiffness, the optimal site of steroid injection has yet to be identified. Methods: This prospective, randomized study compared the short-term outcomes of ultrasound-guided GH and SA steroid injections in patients who were diagnosed with impingement syndrome and mild stiffness. Each group comprised 24 patients who received either a GH or SA injection of 40 mg of triamcinolone. Range of motion and clinical scores were assessed before and 3, 7, and 13 weeks after the injection. Results: GH and SA injections significantly improved the range of motion and clinical scores after 13 weeks of follow-up. Notably, targeting the GH joint resulted in an earlier gain of forward elevation, external rotation, and internal rotation in 3 weeks (P<0.001, P=0.012, and P=0.002, respectively) and of internal rotation and a Constant-Murley score in 7 weeks (P<0.001 and P=0.046). Subsequent measurements were similar between the groups and showed a steady improvement in all ranges of motion and clinical scores. Conclusions: GH injections may be more favorable than SA injections for treatment of impingement syndrome with mild stiffness, especially in improving the range of motion in the early period. However, the procedures showed similar outcomes after 3 months. Level of evidence: I.

• Structural Engineering and Mechanics
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• 제66권6호
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• pp.783-792
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• 2018

This paper presents a detailed theoretical study of the sleeved compression members based on a mechanical model. In the mechanical model, the core protrusion above sleeve and the contact force between the core and sleeve are specially taken into account. Via the theoretical analyses, load-displacement relationships of the sleeved compression members are obtained and verified by the experimental results. On the basis of the core moment distribution changing with the increase of the applied axial load, failure mechanism of the sleeved compression members is assumed and proved to be consistent with the experimental results in terms of the failure modes and the ultimate bearing capacities. A parametric study is conducted to quantify how essential factors including the core protrusion length above sleeve, stiffness ratio of the core to sleeve, core slenderness ratio and gap between the core and sleeve affect the mechanical behaviors of the sleeved compression members, and it is concluded that the constrained effect of the sleeve is overestimated neglecting the core protrusion; the improvement of ultimate bearing capacity for the sleeved compression member is considered to be decreasing with the decrease of the core slenderness ratio and for the sleeved compression member with core of small slenderness ratio, small gap and small stiffness ratio are preferred to obtain larger ultimate bearing capacity and stiffness.

• Tribology and Lubricants
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• 제34권6호
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• pp.307-312
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• 2018

Unlike a typical static seals, spring-energized static seals exhibit improvement in leak-tightness by reinforcing the spring inside the aluminum lining. Thus, spring-energized static seals are widely used in various industrial fields, such as aerospace, semiconductors, and petrochemical industries. The primary objective of this study is to develop design guidelines for spring-energized static seals in a wide range of temperatures, including that of cryogenic environments, by analyzing the required performance and influence of design variables through simulations. There are various parameters that can be controlled to design a leak-tight seal. In this study, the finite element analysis (FEA) is performed by controlling the parameters related to the spring and the thickness of the aluminum lining, and the result of the leakage between the seal and the casing is confirmed. Considering the influence of each parameters, all of them are found to be important. However, it is observed that the spring-related variables are more important than the aluminum lining or other variables when complexity is considered. We can identify the threshold value of spring stiffness that changes leak-tight performance of the seal by performing FEA. Simulation results, under the conditions that are considered in this study, show that spring stiffness should be at least 3.6 N/m to maintain leak-tightness caused by the sufficient contact force between the aluminum lining and the upper and lower casings.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.121-128
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• 2005

This study presents an effective stiffness-based optimal technique to control quantitatively lateral drift for shear wall structures subject to lateral loads. To this end the displacement sensitivity depending on behavior characteristics of shear wall structures is established. Also, the approximation concept that can preserve the generality of the mathematical programming and can efficiently solve large scale problems is introduced. Resizing sections in the stiffness-based optimal design are assumed to be uniformly varying in size and the technique of member grouping is considered for the improvement of construction efficiency Two types of 11-story shear wall structures are presented to illustrate the features of the quantitative lateral drift control technique proposed in this study.

• 소성∙가공
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• 제17권7호
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• pp.481-485
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• 2008

The subframe type rear suspension consisting of a side member and a front/rear cross member is widely used in a medium car and full car. In the small car case, the beam of tubular type without independent suspension system is used to reduce manufacturing cost. In this study, a subframe type rear suspension by hydroforming has been developed. In designing suspension, a driving stability and durability should be considered as an important factor for the performance improvement, respectively. Thus, we focus on increasing the stiffness of suspension and decreasing the maximum stress affecting a durability cycle life. Several optimization design techniques such as shape, size, and topology optimization are implemented to meet these requirements. The shapes of rear suspension obtained from optimization are formed by using hydroforming process. Through commercial software based on the finite element, the superiority of this design method is demonstrated.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.553-558
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• 1998

Two-way slab-column specimens were tested under monotonic loading increased up to punching shear failure to investigate the beneficial effects of fiber-reinforced concrete. The parameters for experiments are the placement of fibers within the immediate column region, the placement on the entire surface of the slab, and no placement of fibers. The effects of these parameters on the punching shear capacity, negative moment cracking. and stiffness of the two-way slab specimens were studied. According to the results the addition of steel fibers in the slab around the column results in a significant improvement in the performance including the increase of punching shear resistance, greater post-cracking stiffness and smaller crack width at service load levels.