• Title/Summary/Keyword: Longitudinal Stiffness

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Experimental and analytical behaviour of cogged bars within concrete filled circular tubes

  • Pokharel, Tilak;Yao, Huang;Goldsworthy, Helen M.;Gad, Emad F.
    • Steel and Composite Structures
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    • v.20 no.5
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    • pp.1067-1085
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    • 2016
  • Recent research on steel moment-resisting connection between steel beams and concrete filled steel tubes has shown that there are considerable advantages to be obtained by anchoring the connection to the concrete infill within the tube using anchors in blind bolts. In the research reported here, extensive experimental tests and numerical analyses have been performed to study the anchorage behaviour of cogged deformed reinforcing bars within concrete filled circular steel tubes. This data in essential knowledge for the design of the steel connections that use anchored blind bolts, both for strength and stiffness. A series of pull-out tests were conducted using steel tubes with different diameter to thickness ratios under monotonic and cyclic loading. Both hoop strains and longitudinal strains in the tubes were measured together with applied load and slip. Various lead-in lengths before the bend and length of tailed extension after the bend were examined. These dimensions were limited by the dimensions of the steel tube and did not meet the requirements for "standard" cogs as specified in concrete standards such as AS 3600 and ACI 318. Nevertheless, all of the tested specimens failed by bar fracture outside the steel tubes. A comprehensive 3D Finite Element model was developed to simulate the pull-out tests. The FE model took into account material nonlinearities, deformations in reinforcing bars and interactions between different surfaces. The FE results were found to be in good agreement with experimental results. This model was then used to conduct parametric studies to investigate the influence of the confinement provided by the steel tube on the infilled concrete.

Computation of Energy Release Rates for Slender Beam through Recovery Analysis and Virtual Crack Closure Technique (차원 복원해석과 가상균열닫힘 기법을 이용한 종방향 균열을 가진 세장비가 큰 보의 에너지 해방률 계산)

  • Jang, Jun Hwan;Koo, Hoi-Min;Ahn, Sang Ho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.30 no.1
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    • pp.31-37
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    • 2017
  • In this paper, computation results of reducible modeling, stress recovery and energy release rate were compared with the results of VABS, Virtual Crack Closure Technique. The result of stress recovery analysis for 1-D model including the stiffness matrix is compared with stress results of three-dimensional 3-D FEM. Energy release rate of composite beam with longitudinal cracks is calculated and compare verifications of numerical analysis results of 3-D FEM and VABS. The procedure of calculating energy release rate through dimensional reduction and stress recovery is intended to be efficient and be utilized in the life-cycle of high-altitude uav's wing, wind blades and tilt rotor blade.

Design of Longitudinal prestress of precast decks in twin-girder continuous composite bridges (강박스거더 교량의 프레임 형식 중간다이아프램의 설계)

  • Yoon, Dong Yong;An, Sung Hyun;Lee, Sung Chul
    • Journal of Korean Society of Steel Construction
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    • v.18 no.5
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    • pp.515-524
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    • 2006
  • Cross-sectional distortions take place when steel box girders a re subjected to torsional moment, as a consequence of which distortional warping stresses are necessarily developed. Additional normal stresses due to the distortion are should be included at the design stage. The relative magnitude with respect to the maximum bending stress are kept less than the specific values, i.e., at 5~10%, by properly spaced intermediate diaphragms that could prevent the distortional deformation of the box girder. However, current design equations for the stiffness of intermediate diaphragms were derived based on BEF. In this study, the area required by the intermediate diaphragm members are investigated through three-dimensional finite element analyses. The results of the analyses indicate that the current equations give to conservative values for the intermediate diaphragm of box girder bridges. Finally, an improved equation for the area of the intermediate diaphragm is derived from a regression analysis from the finite element analysis results.

Analysis of Post-tensioned Slab Bridge by Means of Specially Orthotropic Laminates Theory (특별직교이방성 복합적층판 이론을 응용한 포스트텐션된 슬래브 교량의 해석)

  • Han, Bong Koo;Kim, Yun Pyo
    • Journal of Korean Society of Steel Construction
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    • v.14 no.1
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    • pp.105-111
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    • 2002
  • A post-tensioned slab bridge is analyzed by the specially orthotropic laminates theory. Both the geometry and the material of the cross section of the slab are considered symmetrical with respect to the mid-surface so that the bending extension coupling stiffness, $B_{ij}=0$, and $D_{16}=D_{26}=0$. Each longitudinal and transverse steel layer is regarded as a lamina, and material constants of each lamina is calculated by the use of rule of mixture. This bridge with simple support is under uniformly distributed vertical and axial loads. In this paper, the finite difference method and the beam theory are used for analysis. The result of beam analysis is modified to obtain the solution of the plate analysis. The result of this paper can be used for post-tensioned slab bridge analysis by the engineers with undergraduate study in near future.

Flexural behaviour of reinforced low-strength concrete beams strengthened with CFRP plates

  • Boukhezar, Mohcene;Samai, Mohamed Laid;Mesbah, Habib Abdelhak;Houari, Hacene
    • Structural Engineering and Mechanics
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    • v.47 no.6
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    • pp.819-838
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    • 2013
  • This paper summarises the results of an experimental study to investigate the flexural behaviour of reinforced concrete beams strengthened using carbon-fibre reinforced polymer (CFRP) laminate in four-point bending. The experimental parameters included are the reinforcing bar ratio ${\rho}_s$ and preload level. Four bar ratios were selected (${\rho}_s=0.13$ to 0.86%), representing the section of two longitudinal tensile reinforcements, with diameters of 8, 14, 16, and 20 mm in order to reveal the effect of bar ratio on failure load and failure mode. Eight beams that could be considered "full-scale" in size, measuring 200 mm in width, 400 mm in total height and 2300 mm in length, were tested. Three beams were selected with different bar ratios (${\rho}_1$, ${\rho}_2$, ${\rho}_3$), and considered as control specimens (without ), while three other beams identical to the control beams with the same CFRP laminates ratio and a seventh beam with ${\rho}_{min}$ (the lowest bar ratio) were also used. In the second part of the study, two beams with the bar ratio ${\rho}_2$ were preloaded at two levels, 50 and 100% of their ultimate loads, and then repaired. This experimental investigation was consolidated using an analytical model. The experimental and analytical results indicate that the flexional capacity and stiffness of strengthened and repaired beams using CFRP laminate were increased compared to those of control beams, and the behaviour of repaired beams was nearly similar to the undamaged and strengthened beams; unlike the ductility of strengthened beams, which was greatly reduced compared to the control.

A Study on the Design Bending Moments of Long Span Decks with KL-510 Load (KL-510 하중을 적용한 장지간 바닥판의 설계휨모멘트에 관한 연구)

  • Chung, Chulhun;Lee, Hanjoo;Joo, Sanghoon;An, Hohyun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.36 no.3
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    • pp.375-384
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    • 2016
  • In the current Korea highway bridge design code (KHBDC), the criteria of concrete bridge decks are mainly based on short span decks of steel plate girder bridge, there are very little the specific criteria of long span decks in the twin steel plate girder bridge. Therefore, to put more rational and practical design criteria of the long span decks on the code, the complements of the related criteria are required in the current design code. This paper proposed the design bending moments of decks with 6.0~12.0m span for KL-510 load in direction to bridge (longitudinal direction) and perpendicular direction to bridge (transverse direction). The effects of orthotropic concrete decks, stiffness of steel girders and multiple lane loading factors (MLLF) were reflected in the design bending moments. The proposed design bending moments were compared to the design bending moments with DB-24 load.

Evaluation on Static Behavior of Long Span Prestressed Concrete Deck (장지간 프리스트레스트 콘크리트 바닥판의 정적 거동 평가)

  • Joo, Sanghoon;Chung, Chulhun;Lee, Hanjoo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.36 no.6
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    • pp.969-977
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    • 2016
  • In this paper, the static load test of long span PSC deck used in the twin steel plate girder bridge was conducted. To evaluate the structural behavior of long span deck, longitudinally sufficient length of deck is needed, but it is difficult to test the full-scale long span deck due to limit of transportation, setting and laboratory space. Therefore, this study proposed a method to apply longitudinal stiffness of the full-scale deck to the test specimen of longitudinally short length, and it was reinforced with the steel beam. The failure behavior and structural performance of the long span deck were evaluated by the proposed test specimen deck.

Nonlinear response of the pile group foundation for lateral loads using pushover analysis

  • Zhang, Yongliang;Chen, Xingchong;Zhang, Xiyin;Ding, Mingbo;Wang, Yi;Liu, Zhengnan
    • Earthquakes and Structures
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    • v.19 no.4
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    • pp.273-286
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    • 2020
  • The pile group foundation is widely used for gravity pier of high-speed railway bridges in China. If a moderate or strong earthquake occurs, the pile-surrounding soil will exhibit obvious nonlinearity and significant pile group effect. In this study, an improved pushover analysis model for the pile group foundation with consideration of pile group effect is presented and validated by the quasi-static test. The improved model uses simplified springs to simulate the soil lateral resistance, side friction and tip resistance. PM (axial load-bending moment) plastic hinge model is introduced to simulate the impact of the axial force changing of pile group on their elastic-plastic characteristics. The pile group effect is considered in stress-stain relations of the lateral soil resistance with a reduction factor. The influence factors on nonlinear characteristics and plastic hinge distribution of the pile group foundation are discussed, including the pier height, longitudinal reinforcement ratio and stirrup ratio of the pile, and soil mechanical parameters. Furthermore, the displacement ductility factor, resistance increase factor and yielding stiffness ratio are provided to evaluate the seismic performance of soil-pile system. A case study for the pile group foundation of a railway simply supported beam bridge with a 32 m-span is conducted by numerical analysis. It is shown that the ultimate lateral force of pile group is not determined by the yielding force of the single one in these piles. Therefore, the pile group effect is essential for the seismic performance evaluation of the railway bridge with pile group foundation.

Seismic Performance of Square RC Column Confined with Spirals (나선철근으로 횡구속된 정사각형 RC 기둥의 내진성능)

  • Ko, Seong Hyun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.16 no.5
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    • pp.88-97
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    • 2012
  • The objective of this research is to investigate the seismic performance and flexure-shear behavior of square reinforced concrete bridge piers with solid and hollow cross section. Test specimens were nonseismically designed with the aspect ratio 4.5 Two reinforced concrete columns were tested under constant axial load while subjected to lateral load reversals with increasing drift levels. Longitudinal steel ratio was 2.217 percent. The transverse reinforcement ratio As/($s{\cdot}h$), corresponding to 58 percent of the minimum lateral reinforcement required by Korean Bridge Design Specifications for seismic detailing, which represent existing columns not designed by the current seismic design specifications or designed by limited ductility concept. This study are to provide quantitative reference data for the limited ductility design concept and tendency for performance or damage assessment based on the performance levels such as cracking, yielding, collapse, etc. Failure behavior, ultimate displacement/drift ratio, displacement ductility, response modification factor, equivalent viscous damping ratio, residual deformation, effective stiffness, plastic hinge length, strain of reinforcements and nonlinear analysis are investigated and discussed in this paper.

Seismic Performance of Octagonal Flared RC Columns using Oblong Hoops (장방형 띠철근을 이용한 팔각형 플레어 RC 기둥의 내진성능)

  • Ko, Seong-Hyun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.19 no.6
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    • pp.1-9
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    • 2015
  • Transverse steel bars are used in the plastic hinge zone of columns to insure adequate confinement, prevention of longitudinal bar buckling and ductile behavior. Fabrication and placement of rectangular hoops and cross-ties in columns are difficult to construct. Details of reinforcement for rectangular section require a lot of rectangular hoops and cross-ties. In this paper, to solve these problems, the new lateral confinement method using oblong hoop is proposed for the transverse confinement of the flared column. It can be the alternative for oblong cross-section and flared column with improved workability and cost-efficiency. The final objectives of this study are to suggest appropriate oblong hoop details and to provide quantitative reference data and tendency for seismic performance or damage assessment based on the drift levels such as residual deformation, elastic strain energy. This paper describes factors of seismic performance such as ultimate displacement/drift ratio, displacement ductility, response modification factor, equivalent viscous damping ratio and effective stiffness.