• Title/Summary/Keyword: load-displacement relationship

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Displacement-based seismic design of open ground storey buildings

  • Varughese, Jiji Anna;Menon, Devdas;Prasad, A. Meher
    • Structural Engineering and Mechanics
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    • v.54 no.1
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    • pp.19-33
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    • 2015
  • Open ground storey (OGS) buildings are characterized by the sudden reduction of stiffness in the ground storey with respect to the upper infilled storeys. During earthquakes, this vertical irregularity may result in accumulated damage in the ground storey members of OGS buildings without much damage in the upper storeys. Hence, the structural design of OGS buildings needs special attention. The present study suggests a modification of existing displacement-based design (DBD) procedure by proposing a new lateral load distribution. The increased demands of ground storey members of OGS buildings are estimated based on non-linear time history analysis results of four sets of bare and OGS frames having four to ten storey heights. The relationship between the increased demand and the relative stiffness of ground storey (with respect to upper storeys) is taken as the criterion for developing the expression for the design lateral load. It is also observed that under far-field earthquakes, there is a decrease in the ground storey drift of OGS frames as the height of the frame increases, whereas there is no such reduction when these frames are subjected to near-field earthquakes.

Shaking Table Test of a Full Scale 3 Story Steel Frame with Friction Dampers (마찰형 감쇠장치가 설치된 실물크기 3층 철골프레임의 진동대 실험)

  • Bae, Chun-Hee;Kim, Yeon-Whan;Lee, Sang-Hyun;Park, Young-Pil
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.17 no.9
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    • pp.862-873
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    • 2007
  • Energy dissipation devices can be considered as an alternative for the seismic performance enhancement of existing structures based on the strengthened seismic design code. In this study, seismic response mitigation effects of friction dampers are investigated through the shaking table test of a full scale 3 story building structure. Frist, the bilinear force-displacement relationship of a structure-brace-friction damper system and the effect of brace-friction damper on the increase of frequency and damping ratio are identified. Second, frequency, displacement, and torque dependent characteristics of the friction damper are investigated by using harmonic load excitation tests. Finally, the shaking table tests are performed for a full scale 3 story steel frame. System identification results using random signal excitation indicated that brace-friction damper increased structural damping ratio and frequency, and El Centro earthquake test showed that brace-friction damper reduced the peak displacement and acceleration significantly. In particular, it was observed that the damping effect due to friction damper becomed obvious when the structure was excited by more intensive load causing frequent slippage of the friction dampers.

A Numerical Analysis of Load Transfer Behavior of Axially Loaded Piles (축하중 재하말뚝의 하중전이 거동에 대한 수치해석)

  • 오세붕;최용규
    • Geotechnical Engineering
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    • v.14 no.2
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    • pp.93-106
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    • 1998
  • The behavior of axially loaded pile was analyzed by two methodologies: one is the finite difference method using load transfer curves recommended by API(1993) , and the other is the numerical analysis using the FLAC program. From both analyses, load-displacement curves and load distributions along the depth were evaluated appropriately for the measured. The analysis using the FLAC could capture the nonlinearity of load-displacement curve even for unloading and reloading cases, since the unloaded stress paths of fill layer elements occurred on the failure envelop. Futhermore, the measured load transfer curves were compared with the API recommendations and with the calculations obtained front the results of the FLAC analysis for the interpretation of the transfer behavior between the soil and the pile under axial loadings. It was concluded that the atrial behavior of open ended piles at Pusan could be evaluated by both the finite difference analysis using API load transfer curves and the numerical analysis using FLAC.

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Load-Displacement Relationship of Passive Vibration Units Composed with a Spring and Vibration-Proof Rubbers (스프링과 방진고무가 융합된 제진장치의 하중-변위 관계)

  • Mun, Ju-Hyun;Im, Chae-Rim;Wang, Hye-Rin;Yang, Keun-Hyeok
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.6
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    • pp.226-234
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    • 2021
  • The objective of this study is to establish the fundamental design data for axial load-displacement relationship under axial monotonic or cyclic responses of seismic damping·isolation (SDI) units developed for ceiling structures. The main parameters include the installation of a spring, the number of rubber layer, prestress stress of bolts for connector between the spring and rubbers, and loading type. Test results showed that SDI units with a spring in the core and higher prestress stress of bolts tended to be higher stiffness at the ascending branch and more ductile behavior at the descending branch. This trends more notable for the specimens under monotonic load rather than cyclic loads. Consequently, the energy dissipation of SDI unit can be optimally designed with the following conditions: installation of a spring within 3-layer rubbers and prestress applied to the bolts at 10% of their yielding strength . When compared with the experimental tension capacity of the developed SDI units, the predictions by JIS B 2704-1 and KDS 31 00 are conservative under monotonic loading but higher by approximately 10% under cyclic loading.

Theoretical study of sleeved compression members considering the core protrusion

  • Zhang, Chenhui;Deng, Changgen
    • Structural Engineering and Mechanics
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    • v.66 no.6
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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.

Modelling of recycled aggregate concrete-filled steel tube (RACFST) beam-columns subjected to cyclic loading

  • Yang, You-Fu
    • Steel and Composite Structures
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    • v.18 no.1
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    • pp.213-233
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    • 2015
  • A nonlinear finite element analysis (FEA) model is presented for simulating the behaviour of recycled aggregate concrete-filled steel tube (RACFST) beam-columns subjected to constant axial compressive load and cyclically increasing flexural loading. The FEA model was developed based on ABAQUS software package and a displacement-based approach was used. The proposed engineering stress versus engineering strain relationship of core concrete with the effect of recycled coarse aggregate (RCA) replacement ratio was adopted in the FEA model. The predicted results of the FEA model were compared with the experimental results of several RACFST as well as the corresponding concrete-filled steel tube (CFST) beam-columns under cyclic loading reported in the literature. The comparison results indicated that the proposed FEA model was capable of predicting the load versus deformation relationship, lateral bearing capacity and failure pattern of RACFST beam-columns with an acceptable accuracy. A parametric study was further carried out to investigate the effect of typical parameters on the mechanism of RACFST beam-columns subjected to cyclic loading.

Bond Characteristics of FRP sheet to Various Types under Cyclic Load (반복하중하의 FRP 시트 종류에 따른 부착특성)

  • Ko, Hune Bum
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.2
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    • pp.131-138
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    • 2008
  • Fiber-reinforced polymer (FRP) sheets have been successfully used to retrofit a number of existing concrete buildings and structures because of their excellent properties (high strength, light weight and high durability). Bond characteristics between FRP sheets and concrete should be investigated to ensure an effective retrofitting system. RC structures strengthened with FRP sheets are often subjected to cyclic load (traffic, seismic, temperature, etc.). This research addresses a local bond stress-slip relationship under cyclic loading conditions for the FRP-concrete interface. 18 specimens were prepared with three types of FRP sheets (aramid, carbon, and polyacetal) and two types of sheet layer(one or two). The characteristics of bond stress-slip were verified through experimental results on load-displacement relationship.

Behavior Characteristics Comparison of Bridge Decks Strengthened with Glass Fiber Sheets On the Static Load and Service Load (정적하중과 사용하중하에서 유리 섬유로 보강된 교량 바닥판의 거동특성에 대한 비교)

  • 심종성;오홍섭;류승무;김영호
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.11a
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    • pp.59-64
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    • 2001
  • The concrete bridge decks are in need of replacement and rehabilitation due to decreasing load carrying capacity. In this study, to extend life cycle of the concrete bridge decks which are reinforced with the glass fiber sheets, the concrete bridge decks are examined on the strengthen effect and the fatigue behavior. The behavior of strengthened slabs is represented by load-displacement relationship, variation of compliance and total released energy. Owing to result of that, the strengthened slabs is modified the elasticity, the compliance and represents to control the crack elongation, to elevate the total released energy, to modify the fatigue life. When the concrete bridge deck is strengthened, the crack propagation nay be controled efficiently.

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A Study on Increase of Bearing Capacity of Dense Sandy Ground installed by Vertical Micropiles (연직 마이크로파일이 설치된 조밀한 모레지반의 지지력 증가에 관한 연구)

  • 최상민;임종철;이태형;공영주
    • Proceedings of the Korean Geotechical Society Conference
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    • 2001.03a
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    • pp.355-362
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    • 2001
  • Since micropiles were conceived in Italy in the early 1950s, which have been widely used for In-situ reinforcement, bearing pile or the concept of combination in the world-wide. The meaning of micropiles usually differs from that of a general deep foundation. Because the load capacity of it was mainly affected by skin friction. Also, it could be obtained the improvement effects of load capacity or ground's rigidity by the unitary behavior of ground and micropiles. In this study, The model tests were peformed on the dense sand where micropiles are set to the vertical direction. Strip footing was used in it. Steel bars of dia. 2 and 4㎜ were used in model tests of which the sand was attached on the surface, and the length of it was changed as 2B to 6B(where, B is width of strip footing) Through this process, the load capacity were analyzed from the test results in the relationship between load and displacement.

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The Effects of Friction on the Contact Area and the Distribution of Contact Pressure (접촉 면적과 접촉면 압력분포에 대한 마찰의 영향)

  • 이문주;조용주
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1999.11a
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    • pp.193-199
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    • 1999
  • In the 3-Dimensional contact of the smooth spheres, the effects of friction on the contact area and the distribution of contact pressure was studied numerically. The contact area and pressure distribution was evaluated for the only normal load and for the case of a normal load in the presence of a tangential traction. To do this work, the technique of simple discretization using the load . displacement relationship for a uniformly distributed load of a rectangular patch was used.

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