• Steel and Composite Structures
• /
• 제19권2호
• /
• pp.417-439
• /
• 2015

Many methods are developed for strengthening of reinforced concrete structural members against the effects of shear. One of the commonly used methods in recent years is turned out to be bonding of fiber reinforced polymers (FRP). Impact loading is one of the important external effects on the reinforced concrete structural members during service period among the others. The determination of magnitude, the excitation time, deformations and stress due to impact loadings are complicated and rarely known. In recent year impact behavior of reinforced concrete members have been researched with experimental studies by using drop-weight method and numerical simulations are done by using finite element method. However the studies on the strengthening of structural members against impact loading are very seldom in the literature. For this reason, in this study impact behavior of shear deficient reinforced concrete beams that are strengthened with carbon fiber reinforced polymers (CFRP) strips are investigated experimentally. Compressive strength of concrete, CFRP strips spacing and impact velocities are taken as the variables in this experimental study. The acceleration due to impact loading is measured from the specimens, while velocities and displacements are calculated from these measured accelerations. RC beams are modeled with ANSYS software. Experimental result and simulations result are compared. Experimental result showed that impact behaviors of shear deficient RC beams are positively affected from the strengthening with CFRP strip. The decrease in the spacing of CFRP strips reduced the acceleration, velocity and displacement values measured from the test specimens.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2008년도 춘계학술대회 논문집
• /
• pp.61-66
• /
• 2008

Impact behavior of large SF590A (Fe-0.65C-1.5Mn-0.035P-0.035S-0.3Cr-0.15Mo-0.4Ni-0.3Cu) forged propeller shaft was studied in this study. Charpy impact specimens were prepared from the forged product with different heat number. The impact value of each specimen with different heat number tends to vary greatly depending on the prior austenite grain size and, less significantly, on the amount of sulfur. The dominant metallurgical factors affecting impact behavior of SF590A forged product are discussed based on fractographic and metallographic observations.

• Structural Engineering and Mechanics
• /
• 제84권5호
• /
• pp.619-632
• /
• 2022

Reinforced concrete (RC) structures may be subjected to sudden dynamic impact loads such as explosions occurring for different reasons, the collision of masses driven by rockfall, flood, landslide, and avalanche effect structural members, the crash of vehicles to the highway and seaway structures. Many analytical, numerical, and experimental studies focused on the behavior of RC structural elements such as columns, beams, and slabs under sudden dynamic impact loads. However, there is no comprehensive study on the behavior of the RC column-beam connections under the effect of sudden dynamic impact loads. For this purpose, an experimental study was performed to investigate the behavior of RC column-beam connections under the effect of low-velocity impact loads. Sixteen RC beam-column connections with a scale of 1/3 were manufactured and tested under impact load using the drop-weight test setup. The concrete compressive strength, shear reinforcement spacing in the beam, and input impact energy applied to test specimens were taken as experimental variables. The time histories of impact load acting on test specimens, accelerations, and displacements measured from the test specimens were recorded in experiments. Besides, shear and bending crack widths were measured. The effect of experimental variables on the impact behavior of RC beam-column connections has been determined and interpreted in detail. Besides, a finite element model has been established for verification and comparison of the experimental results by using ABAQUS software. It has been demonstrated that concrete strength, shear reinforcement ratio, and impact energy significantly affect the impact behavior of RC column-beam connections.

• Steel and Composite Structures
• /
• 제12권3호
• /
• pp.207-230
• /
• 2012

Nowadays CFRP (Carbon Fiber Reinforced Polymer) became widely used materials for the strengthening and retrofitting of structures. Many experimental and analytical studies are encountered at literature about strengthening beams by using this kind of materials against static loads and cyclic loads such as earthquake or wind loading for investigating their behavior. But authors did not found any study about strengthening of RC beams by using CFRP against low velocity impact and investigating their behavior. For these reasons an experimental study is conducted on totally ten strengthened RC beams. Impact loading is applied on to specimens by using an impact loading system that is designed by authors. Investigated parameters were concrete compression strength and drop height. Two different sets of specimens with different concrete compression strength tested under the impact loading that are applied by dropping constant weight hammer from five different heights. The acceleration arises from the impact loading is measured against time. The change of velocity, displacement and energy are calculated for all specimens. The failure modes of the specimens with normal and high concrete compression strength are observed under the loading of constant weight impact hammer that are dropped from different heights. Impact behaviors of beams are positively affected from the strengthening with CFRP. Measured accelerations, the number of drops up to failure and dissipated energy are increased. Finite element analysis that are made by using ABAQUS software is used for the simulation of experiments, and model gave compatible results with experiments.

• 산업융합연구
• /
• 제1권1호
• /
• pp.1-24
• /
• 2003

The 583 employees as subject for empirical analysis were selected by cluster sampling method in Banwol & Sihwa Industrial complex in Ansan area. This study shows the followings; 1. In the group where the task is unstructured and the subordinate's ability is high, the achievement-oriented and participative leader behavior have positive impact on the subordinate's expectancy. 2. In the group where the task is unstructured and the subordinate's ability is low, the directive leader behavior has positive impact on the subordinate's expectancy. 3. In the group where the task is structured and the subordinate's ability is high, the supportive leader behavior has positive impact on the subordinate's expectancy. 4. In the group where the task is structured and the subordinate's ability is low, only supportive leader behavior has positive impact on the subordinate's expectancy, and the directive leader behavior has no significant impact. 5. The subordinate's need for growth has a strong moderating effect in the relationship between leader behavior and job satisfaction. Finally this study indicates the implication for future theoretical and empirical development.

• 한국공작기계학회논문집
• /
• 제13권6호
• /
• pp.23-28
• /
• 2004

Impact behavior of polycarbonate in various defect state was investigated using an instrumented impact tester. A method of analyzing raw impact data was developed and successfully demonshsted the impact behavior in terms of load-displacement and energy-displacement curves. This technique was shown to be capable of separating defect no-defect initiated fractures as well as their propagation behaviors.

• Asia Pacific Journal of Business Review
• /
• 제6권1호
• /
• pp.1-19
• /
• 2021

This research is based on the relevant research literature on the voice behavior, this study examines the influence of trust in leader on voice behavior. And this study examines the role of psychological safety as a mediating between trust in leader and voice behavior. This study uses SPSS for data analysis. The results of the study are as follows: This study explains the impact of trust in leader on psychological safety, and explains the impact of trust in leader on organization members' voice behavior, as well as the impact of psychological safety on organization members' voice behavior. And this study also explains the influence of psychological safety as an intermediary effect on trust in leader and voice behavior. Overall, the higher the level of organization members' trust in leader, the more they will increase the level of psychological safety of the organization members, which will prompt the organization members to make more voice behavior.

• 아태비즈니스연구
• /
• 제14권4호
• /
• pp.357-370
• /
• 2023

Purpose - This study examined the influence relationships between the impacts of tourism development, local attachment, and resident involvement and local residents' support and pro-environmental behavior intentions in Jeju Island. Design/methodology/approach - A questionnaire was distributed to the Jeju Island residents and 373 samples were used for the analysis. Findings - The results showed that the perceived positive impact of tourism development has a positive effect on local residents' support, while the negative impact has a negative effect. Local attachment has no significant effect on local residents' support, while local involvement positively affects local residents' support. The positive impact of tourism development has a negative effect on pro-environmental behavior intention, while the perceived negative impact has a positive effect. Finally, when analyzing the relationship between local attachment, local involvement, and local support for eco-friendly behavior intention, it was found that they all have a positive effect. Research implications or Originality - Theoretical and managerial implications and suggestions for future research are discussed.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2014년도 추계 학술논문 발표대회
• /
• pp.139-140
• /
• 2014

The purpose of this study in to evaluate relationship between mechanical properties of materials and fiber type by reinforced fiber with high-velocity impact fracture behavior of fiber reinforced concrete. As a result, for fracture behavior by high-velocity impact, it is considered that impact fracture behavior is not affected by static mechanical properties directly but affected by fiber type and density of the number of fiber. It is necessary to consider type, shape, mechanical properties and the number of fiber with flexural and tensile performance for the evaluation on impact resistance performance of fiber reinforced concrete.

• Composites Research
• /
• 제20권5호
• /
• pp.1-6
• /
• 2007

본 연구에서는 탄소/에폭시 복합재 적층판과 강철평판의 저속충격 거동에 관한 비교 연구를 수행하였다. 각각의 평판의 해석을 위한 판의 충격거동의 타당성을 검증하기 위해 Karas 모델을 사용하여 해석 검증을 하였다. 충격거동 비교연구를 위한 모델은 Karas 모델과 동일한 두께의 강철평판을 모사하였고, 같은 두께의 복합재 적층판을 모사하기 위하여 $[0/90/45/-45/-45/45/90/0]_{8S}$ 적층각을 이용하여 모델링 하였다. 각각의 판에 대한 저속충격 거동을 비교하기 위해 일정한 속도로 낙하하는 충격체 무게별 해석과 일정한 무게를 가진 충격체의 속도변화에 따른 해석 결과를 비교 연구하였다. 연구결과 복합재 적층판과 강철평판의 물성치로 인하여 접촉하중과 판의 변위에서는 결과값의 차이를 보였으나 복합재 적층판의 경우가 판의 유연한 특성으로 충격완화 효과가 보였으며 강철평판 보다 무게비와 충격손상에 대한 우수성을 확인하여 볼 수 있었다.