• Structural Engineering and Mechanics
• /
• 제62권5호
• /
• pp.595-606
• /
• 2017

During their life span, post-tensioned concrete structures may be exposed to thermal loads. Therefore, there has been a growing interest in research on the advanced analysis and design of post-tensioned concrete slabs subjected to thermal loads. This paper investigates the structural behaviour of post-tensioned one-way spanning concrete slabs. A nonlinear finite element model for the analysis of post- tensioned unbonded and bonded concrete slabs at elevated temperatures was developed. The interface between the tendon and surrounding concrete was also modelled, allowing the tendon to retain its profile shape during the deformation of the slab. The load-deflection behaviour, load-force behaviour in the tendon, and the failure modes are presented. The numerical analysis was conducted by the finite element ANSYS software and was carried out on two different one-way concrete slabs chosen from literature. A parametric study was conducted to investigate the effect of several selected parameters on the overall behavior of post-tensioned one-way concrete slab. These parameters include the effect of tendon bonding, the effect of thermal loading and the effect of tendon profile. Comparison between uniform thermal loading and nonuniform thermal loading showed that restrained post tensioned slab with bottom surface hotter has smaller failure load capacity.

• 국제초고층학회논문집
• /
• 제3권3호
• /
• pp.231-241
• /
• 2014

Ductile fracture is one of the most common failure modes of steel beam-to-column connections in moment resisting frames. Most proposed evaluation methods of the plastic deformation capacity of a beam until ductile fracture are based on steel beam tests, where the material's yield strength/ratio, the beam's moment gradient, and loading history are the most important parameters. It is impossible and unpractical to cover all these parameters in real tests. Therefore, a new attempt to evaluate a beam's plastic deformation capacity through analysis is introduced in this paper. Another important issue is about the loading histories. Recent years, the effect on the structural component under long-duration ground motion has drawn great attentions. Steel beams tends to experience a large number of loading cycles with small amplitudes during long-duration earthquakes. However, current research often focuses on the beam's behavior under standard incremental loading protocols recommended by respective countries. In this paper, the plastic deformation capacity of steel beams subjected to long duration ground motions was evaluated through analytical methodology.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
• /
• pp.33-36
• /
• 2008

조개껍질과 같이 얇은 요소들이 생체적인 접착제에 의해서 겹겹이 쌓여 층 구조를 이루는 패각은 정적하중 및 충격하중에 대하여 뛰어난 저항 성능을 보이는 것으로 알려져 있다. 이러한 다양한 층 구조의 복합재료는 두 개의 서로 다른 매질이 적층되면서 단일 재질의 경우보다 충격, 완화 효율이 극대화될 것이라 판단된다. 본 연구에서는 충격을 견디고 최소화시키기 위한 분절 복합체(Segmented Composites)로써 층 구조의 형태를 가지는 복합 재료를 개발하기 위해 일반 모르타르와 일반 콘크리트 블록을 이용한 보 형태의 분절 복합체 부재를 제작하여 정적하중 및 충격하중 실험을 실시하였다. 그리고 분절 복합체의 성능 및 파괴형태를 콘크리트 블록과 같은 강도로 제작된 콘크리트 보 부재와 비교하였다.

• Steel and Composite Structures
• /
• 제26권1호
• /
• pp.67-78
• /
• 2018

The application of rib stiffeners is common on steel connections, with regard to the stiffened angle connection, experimental results about the influence of stiffeners under monotonic and cyclic loading are very limited. Consequently, this paper presents the experimental investigation on four types angle connections with or without stiffener under static loading and another four type stiffened angle connections subjected to cyclic loading. The static experimental result showed that the rib stiffener weld in tension zone of the connection greatly enhanced its initial rotational stiffness and flexural strength. While a stiffener was applied to the compression zone of the connection, it had not obvious influences on the initial rotational stiffness, but increased its flexural strength. The moment-rotation curves, skeleton curves, ductility, energy dissipation and rigidity were evaluated under cyclic loading. Stiffened top-and-seat angle connections behaved as semi-rigid and partial strength, and rotation of all stiffened angle connections exceeded 0.04rad. The failure modes between monotonic and cyclic loading test were completely different and indicated certain robustness.

• Computers and Concrete
• /
• 제21권5호
• /
• pp.583-592
• /
• 2018

Today, buildings are exposed to the effects such as explosion and impact loads. Usually, explosion and impact loads that act on the buildings such as nuclear power plants, airports, defense industry and military facilities, can occur occasionally on the normal buildings because of some reasons like drop weight impacts, natural gas system explosions, and terrorist attacks. Therefore, it has become important to examine the behavior of reinforced concrete (RC) structures under impact loading. Development of computational mechanics has facilitated the modeling of such load conditions. In this study, three kinds of RC walls that have different geometric forms (square, ellipse, and circle) and used in guardhouses with same usage area were modeled with Abaqus finite element software. The three configurations were subjected to the same impact energy to determine the geometric form that gives the best behavior under the impact loading. As a result of the analyses, the transverse impact forces and failure modes of RC walls under impact loading were obtained. Circular formed (CF) reinforced concrete wall which has same impact resistance in each direction had more advantages. Nonetheless, in the case of the impact loading occurring in the major axis direction of the ellipse (EF-1), the elliptical formed reinforced concrete wall has higher impact resistance.

• Steel and Composite Structures
• /
• 제38권2호
• /
• pp.165-176
• /
• 2021

Existing research on confined concrete filled steel tubular (CCFT) columns has been mainly focused on static or cyclic loading. In this paper, square section CCFT and CFT columns were tested under both static and impact loading, using a 10,000 kN capacity compression test machine and a drop weight testing equipment. Research parameters included bonded and unbonded fiber reinforced polymer (FRP) wraps, with carbon, basalt and glass FRPs (or CFRP, BFRP, and GFRP), respectively. Time history curves for impact force and steel strain observed are discussed in detail. Experimental results show that the failure modes of specimens under impact testing were characterized by local buckling of the steel tube and cracking at the corners, for both CCFT and CFT columns, similar to those under static loading. For both static and impact loading, the FRP wraps could improve the behavior and increase the loading capacity. To analyze the dynamic behavior of the composite columns, a finite element, FE, model was established in LS-DYNA. A simplified method that is compared favorably with test results is also proposed to predict the impact load capacity of square CCFT columns.

• Journal of the Korean Wood Science and Technology
• /
• 제31권3호
• /
• pp.61-69
• /
• 2003

This study investigated the effect of moisture content and loading direction on dowel bearing strength of two types of SCL. Dowel bearing tests of LVL and PSL were conducted with two different MC level, 7.5% and 19%, and two different oriention, L-direction(loading parallel to grain) and X-direction(loading perpendicular to grain). Most of specimens showed typical load-deformation curves and intersected 5% offset line. Failure modes were classified into two categories; spliting(for L-direction specimens) and peeling(for X-direction specimens). Dowel bearing strength generally decreased with increasing MC. The decreasing rate was more significant in X-directon. ESG also decreased with increasing MC, and the ratio of ESG of 7.5% versus 19% was about 1.47. Dowel bearing strength of LVL and PSL in L-direction was higher than that of X-direction. This results indicated that MC and loading orientation had a significant effect on dowel bearing strength of SCL. The average dowel bearing strength of LVL were higher than that of PSL in each loading direction. Two types of probability distribution model were chosen to quantify strength distribution, normal and 2-parameter weibull distribution. The two models showed good agreement with the data, especially in lower tail of the cumulative distribution. Normal and 2-parameter weibull distribution seemed to proper model of the dowel bearing strength for each MC levels.

• 한국공간구조학회논문집
• /
• 제22권2호
• /
• pp.29-37
• /
• 2022

The collapse of reinforced concrete (RC) frame buildings is mainly caused by the failure of columns. To prevent brittle failure of RC column, numerous studies have been conducted on the seismic performance of strengthened RC columns. Concrete jacketing method, which is one of the retrofitting method of RC members, can enhance strength and stiffness of original RC column with enlarged section and provide uniformly distributed lateral load capacity throughout the structure. The experimental studies have been conducted by many researchers to analyze seismic performance of seismic strengthened RC column. However, structures which have plan and vertical irregularities shows torsional behavior, and therefore it causes large deformation on RC column when subjected to seismic load. Thus, test results from concentric cyclic loading can be overestimated comparing to eccentric cyclic test results, In this paper, two kinds of eccentric loading pattern was suggested to analyze structural performance of RC columns, which are strengthened by concrete jacketing method with new details in jacketed section. Based on the results, it is concluded that specimens strengthened with new concrete jacketing method increased 830% of maximum load, 150% of maximum displacement and changed the failure modes of non-strengthened RC columns.

• Structural Engineering and Mechanics
• /
• 제90권5호
• /
• pp.435-446
• /
• 2024

The use of cold-formed steel members is increasing day by day, especially in regions where earthquake effects are intensively experienced. Among cold-formed steel members (CFS), "channel" members are used more than other crosssectional members, especially in buildings or industrial structures. In recent years, several studies have been carried out on the axial load and flexural performance of these members under monotonic loading. In this study, CFS beam-column members were cyclically and monotonically loaded under combined axial load and biaxial bending moments, and their buckling behavior, load bearing capacity, stiffness, ductility, and energy absorption capacity were determined. For this purpose, monotonic and cyclic loading experiments were carried out on 30 CFS channel members at 15 different eccentricities. Then, material properties were determined by axial monotonic tensile and very low cycle fatigue tests for use in numerical studies. From the experimental results, the buckling modes, bearing capacities, ductility, stiffness, and energy absorption capacities of the members were obtained. The characteristics of the members were compared according to the stress state of the lips. According to the data obtained from the displacement transducer placed on the lips and on the back of the web, information about the buckling mode and curvature of the members was obtained. Finally, monotonic, and cyclic loading results were compared to determine the differences in the buckling behavior of the members.

• Journal of Korean Neurosurgical Society
• /
• 제45권3호
• /
• pp.169-175
• /
• 2009

Objective : The goal of this study was to evaluate the biomechanical features of human cadaveric spines implanted with the Activ L prosthesis. Methods : Five cadaveric human lumbosacral spines (L2-S2) were tested for different motion modes, i.e. extension and flexion, right and left lateral bending and rotation. Baseline measurements of the range of motion (ROM), disc pressure (DP), and facet strain (FS) were performed in six modes of motion by applying loads up to 8 Nm, with a loading rate of 0.3 Nm/second. A constant 400 N axial follower preload was applied throughout the loading. After the Activ L was implanted at the L4-L5 disc space, measurements were repeated in the same manner. Results : The Activ L arthroplasty showed statistically significant decrease of ROM during rotation, increase of ROM during flexion and lateral bending at the operative segment and increase of ROM at the inferior segment during flexion. The DP of the superior disc of the operative site was comparable to those of intact spine and the DP of the inferior disc decreased in all motion modes, but these were not statistically significant. For FS, statistically significant decrease was detected at the operative facet during flexion and at the inferior facet during rotation. Conclusion : In vitro physiologic preload setting, the Activ L arthroplasty showed less restoration of ROM at the operative and adjacent levels as compared with intact spine. However, results of this study revealed that there are several possible theoretical useful results to reduce the incidence of adjacent segment disease.