• Title/Summary/Keyword: Effective compressive stiffness

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Shear performance assessment of steel fiber reinforced-prestressed concrete members

  • Hwang, Jin-Ha;Lee, Deuck Hang;Park, Min Kook;Choi, Seung-Ho;Kim, Kang Su;Pan, Zuanfeng
    • Computers and Concrete
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    • v.16 no.6
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    • pp.825-846
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    • 2015
  • In this study, shear tests on steel fiber reinforced-prestressed concrete (SFR-PSC) members were conducted with test parameters of the concrete compressive strength, the volume fraction of steel fibers, and the level of effective prestress. The SFR-PSC members showed higher shear strengths and stiffness after diagonal cracking compared to the conventional prestressed concrete (PSC) members without steel fibers. In addition, their shear deformational behavior was measured using the image-based non-contact displacement measurement system, which was then compared to the results of nonlinear finite element analyses (NLFEA). In the NLFEA proposed in this study, a bi-axial tensile behavior model, which can reflect the tensile behavior of the steel fiber-reinforced concrete (SFRC) in a simple manner, was introduced into the smeared crack truss model. The NLFEA model proposed in this study provided a good estimation of shear behavior of the SFRPSC members, such as the stiffness, strengths, and failure modes, reflecting the effect of the key influential factors.

A Study on the Modified Simple Truss Model to Predict the Punching Shear Strength of PSC Deck Slabs (PSC 바닥판의 뚫림전단강도 예측을 위한 단순트러스모델 개선 연구)

  • Park, Woo Jin;Hwang, Hoon Hee
    • Journal of the Korean Society of Safety
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    • v.30 no.5
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    • pp.67-73
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    • 2015
  • In this paper, the simple truss model was modified to predict the punching shear strength of long-span prestressed concrete (PSC) deck slabs under wheel load including the effects of transverse prestressing and long span length between girders. The strength of the compressive zone arounding punching cone was evaluated by the stiffness of inclined strut which was modified by considering aging effective modulus. The stiffness of springs which control lateral displacement of the roller supports consists of the steel reinforcement and prestressing which passed through the punching cone. Initial angle of struts was determined by the experimental observation to compensate for uncertainties in the complexities of the punching shear. The validity of computed punching shear strength by modified simple truss model was shown by comparing with experimental results and the experimental results were also compared with existing punching shear equations to determine level of predictability. The modified simple truss model appeared to better predict the punching shear strength of PSC deck slabs than other available equations. The punching shear strength, which was determined by snap-through critical load of modified simple truss model, can be used effectively to examine punching shear strength of long span PSC deck slabs.

Structural behavior of sandwich composite wall with truss connectors under compression

  • Qin, Ying;Chen, Xin;Zhu, Xingyu;Xi, Wang;Chen, Yuanze
    • Steel and Composite Structures
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    • v.35 no.2
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    • pp.159-169
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    • 2020
  • Sandwich composite wall consists of concrete core attached by two external steel faceplates. It combines the advantage of steel and concrete. The appropriate composite action between steel faceplate and concrete core is achieved by using adequate mechanical connectors. This research studied the compressive behavior of the sandwich composite walls using steel trusses to bond the steel faceplates to concrete infill. Four short specimens with different wall width and thickness of steel faceplate were designed and tested under axial compression. The test results were comprehensively evaluated in terms of failure modes, load versus axial and lateral deformation responses, resistance, stiffness, ductility, strength index, and strain distribution. The test results showed that all specimens exhibited high resistance and good ductility. Truss connectors offer better restraint to walls with thinner faceplates and smaller wall width. In addition, increasing faceplate thickness is more effective in improving the ultimate resistance and axial stiffness of the wall.

Stiffness Comparison of Tissue Phantoms using Optical Coherence Elastography without a Load Cell

  • Chae, Yu-Gyeong;Park, Eun-Kee;Jeon, Min Yong;Jeon, Byeong-Hwan;Ahn, Yeh-Chan
    • Current Optics and Photonics
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    • v.1 no.1
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    • pp.17-22
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    • 2017
  • Mechanical property of tissue is closely related to diseases such as breast cancer, prostate cancer, cirrhosis of the liver, and atherosclerosis. Therefore measurement of tissue mechanical property is important for a better diagnosis. Ultrasound elastography has been developed as a diagnostic modality for a number of diseases that maps mechanical property of tissue. Optical coherence elastography (OCE) has a higher spatial resolution than ultrasound elastography. OCE, therefore, could be a great help for early diagnosis. In this study, we made tissue phantoms and measured their compressive moduli with a rheometer measuring the response to applied force. Uniaxial strain of the tissue phantom was also measured with OCE by using cross-correlation of speckles and compared with the results from the rheometer. In order to compare stiffness of tissue phantoms by OCE, the applied force should be measured in addition to the strain. We, however, did not use a load cell that directly measures the applied force for each sample. Instead, we utilized one silicone film (called as reference phantom) for all OCE measurements that indirectly indicated the amount of the applied force by deformation. Therefore, all measurements were based on displacement, which was natural and effective for image-based elastography such as OCE.

Strength enhancement in confined concrete with consideration of flexural flexibilities of ties

  • Teerawong, J.;Lukkunaprasit, P.;Senjuntichai, T.
    • Structural Engineering and Mechanics
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    • v.18 no.2
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    • pp.151-166
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    • 2004
  • The interaction between concrete core expansion and deformation of perimeter ties has been known to have a significant effect on the effective confinement of rectangular reinforced concrete (RC) tied columns. This interaction produces passive confining pressure to the concrete core. Most existing models for determining the response of RC tied columns do not directly account for the influence of flexural stiffness of the ties and the variation of confining stress along the column height. This study presents a procedure for determining the confined compressive strength of RC square columns confined by rectilinear ties with various tie configurations considering directly the influence of flexural flexibility of the ties and the variation of confining stress along the vertical direction. The concept of area compatibility is employed to ensure compatibility of the concrete core and steel hoop in a global sense. The proposed procedure yields satisfactory predictions of confined strengths compared with experimental results, and the influence of tie flexibility, tie configuration and degree of confinement can be well captured.

Experimental investigation of a frame retrofitted with carbon textile reinforced mortar

  • Sinan M., Cansunar;Kadir, Guler
    • Earthquakes and Structures
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    • v.23 no.5
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    • pp.473-491
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    • 2022
  • The research investigates experimentally the effect of confinement on structural behavior at the ends of beam-column in reinforced concrete (RC) frames. In the experimental study, five specimens consisting of 1/3-scaled RC frames having single-bay, representing the traditional deficiencies of existing buildings constructed without receiving proper engineering service is investigated. The RC frame specimens were produced to represent most of the existing buildings in Turkey that have damage potential. To decrease the probable damage to the existing buildings exposed to earthquakes, the carbon Textile Reinforced Mortar (TRM) strengthening technique (fully wrapping) was used on the ends of the RC frame elements to increase the energy dissipation and deformation capacity. The specimens were tested under reversed cyclic lateral loading with constant axial loads. They were constructed satisfying the weak column-strong beam condition and consisting of low-strength concrete, such as compressive strength of 15 MPa. The test results were compared and evaluated considering stiffness, strength, energy dissipation capacity, structural damping, ductility, and damage propagation in detail. Comprehensive investigations of these experimental results reveal that the strengthening of a brittle frame with fully-TRM wrapping with non-anchored was effective in increasing the stiffness, ductility, and energy dissipation capacities of RC bare frames. It was also observed that the frame-only-retrofitting with an infill wall is not enough to increase the ductility capacity. In this case, both the frame and infill wall must be retrofitted with TRM composite to increase the stiffness, lateral load carrying, ductility and energy dissipation capacities of RC frames. The presented strengthening method can be an alternative strengthening technique to enhance the seismic performance of existing or moderately damaged RC buildings.

Shape Design of Disk Seal in $SF_6$ Gas Safety Valve using Taguchi method (다구찌법을 이용한 $SF_6$가스 안전밸브용 디스크 시일 형상의 설계)

  • Cho Seunghyun;Kim Chungkyun;Kim Younggyu
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2004.11a
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    • pp.237-240
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    • 2004
  • Sulfur Hexafluoride, SF6 is widely used for leak detection and as a gaseous dielectric in transformers, condensers and circuit breakers. SF6 gas is also effective as a cleanser in the semiconductor industry. This paper presents a numerical study of the sealing force of disk type seal in SF6 gas safety valve. The sealing force on the disk seal is analyzed by the FEM method based on the Taguch's experimental design technique. Disk seals in SF6 gas safety valve are designed with 9 design models based on 3 different contact length, compressive ratio and gas pressure. The calculated results of Cauchy stress and strain showed that the sealing characteristics of Teflon PTFE is more effective compared to that of FKM(Viton), which is related to the stiffness of the materials. And also, the contact length of the disk seal is important design parameter for sealing the SF6 gas leakage in the safety valve.

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Development of Reinforced Wood Beams Using Polymer Mortar (폴리모 모르터를 이용한 강화목재보의 개발)

  • 연규석
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.32 no.3
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    • pp.79-86
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    • 1990
  • Based on limited number of tests on reinforced wood beams using polymer mortar in this study, following conclusions were drawn ; 1.Reinforcing compression side of wood beam using polymer mortar was effective in reducing deflection. 2.By increasing thickness of polymer mortar, effective beam stiffness was improved, but energy absorption was reduced. 3.Polymer mortar reinforcement improved compressive strength and reduced strain in compression side of the beam. Therefore, it was possible to change the failure mode from by compression in control beam to by tension in composite beams. 4.The composite beams that have more than 2cm of polymer mortar layer did not perform well because a strain redistribution and separation of meterials at interface were induced in moment span. 5.To maximize the load carrying capacity of composite beam, it is necessary to make polymer mortar and wood behave together without failing at interface. To do this, it is needed to use a polymer mortar which has high strength with such elastic modulus that is closer to elastic modulus of wood. otherwise, it is recommended to use shear connectors at interface to prevent separation of materials under ultimate load.

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Effective buckling length of steel column members based on elastic/inelastic system buckling analyses

  • Kyung, Yong-Soo;Kim, Nam-Il;Kim, Ho-Kyung;Kim, Moon-Young
    • Structural Engineering and Mechanics
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    • v.26 no.6
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    • pp.651-672
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    • 2007
  • This study presents an improved method that uses the elastic and inelastic system buckling analyses for determining the K-factors of steel column members. The inelastic system buckling analysis is based on the tangent modulus theory for a single column and the application is extended to the frame structural system. The tangent modulus of an inelastic column is first derived as a function of nominal compressive stress from the column strength curve given in the design codes. The tangential stiffness matrix of a beam-column element is then formulated by using the so-called stability function or Hermitian interpolation functions. Two inelastic system buckling analysis procedures are newly proposed by utilizing nonlinear eigenvalue analysis algorithms. Finally, a practical method for determining the K-factors of individual members in a steel frame structure is proposed based on the inelastic and/or elastic system buckling analyses. The K-factors according to the proposed procedure are calculated for numerical examples and compared with other results in available references.

An Experimental Study on Uniaxial Compressive Behavior of RC Circular Columns Laterally Confined with Prestressing Aramid Fiber Strap (아라미드 스트랩으로 프리스트레싱 횡구속된 RC 원형기둥의 일축압축거동에 관한 실험적 연구)

  • Han, Sang-Hoon;Hong, Ki-Nam;Lee, Jae-Bum
    • Journal of the Korea Concrete Institute
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    • v.21 no.2
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    • pp.159-168
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    • 2009
  • In this study, strength, stiffness and confinement effect with stress-strain and stress-volumetric strain curves for improved uniaxial compressive behavior of RC circular columns laterally confined with prestressing aramid fiber strap were experimentally investigated. The test variables were the specimens with or without axial reinforcing bar and the number and spacing of strap, prestressing level, the types of reinforcing fiber (CFS, GFS). As a result, the failure type of the columns was very stable and strength increase rate was about 73% comparison with the general RC columns. Moreover, the strain increase rate is very small and the axial displacement confinement effect was very effective compared with existry methods (CFS, GFS), the initial and final lateral confinement effect was excellent.