• Title/Summary/Keyword: Axial Compression

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Seismic assessment of transfer plate high rise buildings

  • Su, R.K.L.;Chandler, A.M.;Li, J.H.;Lam, N.T.K.
    • Structural Engineering and Mechanics
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    • v.14 no.3
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    • pp.287-306
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    • 2002
  • The assessment of structural performance of transfer structures under potential seismic actions is presented. Various seismic assessment methodologies are used, with particular emphasis on the accurate modelling of the higher mode effects and the potential development of a soft storey effect in the mega-columns below the transfer plate (TP) level. Those methods include response spectrum analysis (RSA), manual calculation, pushover analysis (POA) and equivalent static load analysis (ESA). The capabilities and limitations of each method are highlighted. The paper aims, firstly, to determine the appropriate seismic assessment methodology for transfer structures using these different approaches, all of which can be undertaken with the resources generally available in a design office. Secondly, the paper highlights and discusses factors influencing the response behaviour of transfer structures, and finally provides a general indication of their seismic vulnerability. The representative Hong Kong building considered in this paper utilises a structural system with coupled shear walls and moment resisting portal-frames, above and below the TP, respectively. By adopting the wind load profile stipulated in the Code of Practice on Wind Effects: Hong Kong-1983, all the structural members are sized and detailed according to the British Standards BS8110 and the current local practices. The seismic displacement demand for the structure, when built on either rock or deep soil sites, was determined in a companion paper. The lateral load-displacement characteristic of the building, determined herein from manual calculation, has indicated that the poor ductility (brittle nature) of the mega-columns, due mainly to the high level of axial pre-compression as found from the analysis, cannot be effectively alleviated solely by increasing the quantity of confinement stirrups. The interstorey drift demands at lower and upper zones caused by seismic actions are found to be substantially higher than those arising from wind loads. The mega-columns supporting the TP and the coupling beams at higher zones are identified to be the most vulnerable components under seismic actions.

Effect of Non-Woven Geotextile Reinforcement on Mechanical Behavior of Sand (모래의 역학적 거동에 미치는 부직포 보강재의 효과)

  • Kim, You-Seong;Oh, Su-Whan;Cho, Dae-Seong
    • Journal of the Korean Geosynthetics Society
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    • v.9 no.4
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    • pp.39-45
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    • 2010
  • The effects of non-woven geotextiles on mechanical behavior of sand were investigated. A comprehensive series of triaxial compression tests were performed for these investigation on unreinforced and reinforced sand with geotextiles. The Joomunjin standard sand was used and non-woven geotextiles were included into sand specimen with three layers. The inclusion of non-woven geotextile reinforcement into sand increased the peak strength of sand significantly and the reinforced samples exhibited a greater axial strain at failure. Also the effect on number of reinforcement layers was studied and found as increasing the number of reinforcement layers resulting in more ductility by clogging developed in the shear band within the specimens. It was also found that the tendency of samples to dilate is restricted by non-woven geotextile inclusion. The effect of nunber of reinforcement layer increasing is just same to the effect of decreasing void ratio of sand in this case.

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Experimental study on shear capacity of SRC joints with different arrangement and sizes of cross-shaped steel in column

  • Wang, Qiuwei;Shi, Qingxuan;Tian, Hehe
    • Steel and Composite Structures
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    • v.21 no.2
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    • pp.267-287
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    • 2016
  • The seismic performance of the ordinary steel reinforced concrete (SRC) columns has no significant improvement compared to the reinforced concrete (RC) columns mainly because I, H or core cross-shaped steel cannot provide sufficient confinement for core concrete. Two improved SRC columns by constructing with new-type shaped steel were put forward on this background, and they were named as enlarging cross-shaped steel and diagonal cross-shaped steel for short. The seismic behavior and carrying capacity of new-type SRC columns have been researched theoretically and experimentally, while the shear behavior remains unclear when the new-type columns are joined onto SRC beams. This paper presents an experimental study to investigate the shear capacity of new-type SRC joints. For this purpose, four new-type and one ordinary SRC joints under low reversed cyclic loading were tested, and the failure patterns, load-displacement hysteretic curves, joint shear deformation and steel strain were also observed. The ultimate shear force of joint specimens was calculated according to the beam-end counterforce, and effects of steel shape, load angel and structural measures on shear capacity of joints were analyzed. The test results indicate that: (1) the new-type SRC joints display shear failure pattern and has higher shear capacity than the ordinary one; (2) the oblique specimens have good bearing capacity if designed reasonably; and (3) the two proposed construction measures have little effect on the shear capacity of SRC joints embedded with diagonal cross-shaped steel. Based on the mechanism observed from the test, the formulas for calculating ultimate shear capacity considering the main factors (steel web, stirrup and axial compression ratio) were derived, and the calculated results agreed well with the experimental and simulated data.

Seismic Resistance of Cast-In-Place Concrete-Filled Hollow PC Columns (현장타설 콘크리트 채움 중공 PC기둥의 내진성능)

  • Lim, Woo-Young;Park, Hong-Gun;Oh, Jung-Keun;Kim, Chang-Soo
    • Journal of the Korea Concrete Institute
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    • v.26 no.1
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    • pp.35-46
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    • 2014
  • Two types of cast-in-place concrete-filled hollow PC (HPC1, HPC2) columns were developed to reduce lifting load of heavy-weight PC columns and to improve the structural integrity of joints. To form the hollow PC columns, a couple of prefabricated PC panels was used for HPC1, and special hoops were used for HPC2. Lateral pressure of wet concrete on PC faces was measured while placing the concrete inside the columns. To evaluate the seismic resistance, full scale specimens of two HPC columns and a conventional RC column were tested under combined axial compression and lateral cyclic loading. The test results showed that the structural performance of the proposed HPC columns such as intial stiffness, maximum strength, and displacement ductility was comparable to that of the conventional RC column, but the energy dissipation of HPC2 slightly decreased after rebar-buckling. However, all the test specimens satisfied the energy dissipation requirement specified in ACI 374.

Straight-Forward versus Bicortical Fixation Penetrating Endplate in Lumbosacral Fixation-A Biomechanical Study

  • Karakasli, Ahmet;Acar, Nihat;Uzun, Bora
    • Journal of Korean Neurosurgical Society
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    • v.61 no.2
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    • pp.180-185
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    • 2018
  • Objective : Many lumbosacral fixation techniques have been described to offer a more screw-bone purchase. The forward anatomical fixation parallel to the endplate is still the most preferred method. Literature revealed little knowledge regarding the mechanical stability of lumbosacral trans-endplate fixation compared to the traditional trans-pedicular screw fixation method. The aim of this study is to assess the pull-out strength of lumbosacral screws penetrating the end plate and comparing it to the conventional trans-pedicular screw insertion method. Methods : Eight lumbar and eight sacral vertebrae, with average age 69.4 years, Left pedicles of the 5th lumbar vertebrae were used for trans-endplate screw fixation, group 1A, right pedicles were used for anatomical trans-pedicular screw fixation, group 1B. In the sacral vertebrae, the right side S1 pedicles were used for trans-endplate fixation, group 2A, left side pedicles were used for anatomical trans-pedicular screw fixation, group 2B. The biomechanical tests were performed using the axial compression testing machine. All tests were applied using 2 mm/min traction speed. Results : The average pull-out strength values of groups 1A and 1B were $403.78{\pm}11.71N$ and $306.26{\pm}17.55N$, respectively. A statistical significance was detected with p=0.012. The average pull-out strength values of groups 2A and 2B were $388.73{\pm}17.03N$ and $299.84{\pm}17.52N$, respectively. A statistical significance was detected with p=0.012. Conclusion : The trans-endplate lumbosacral fixation method is a trustable fixation method with a stronger screw-bone purchase and offer a good alternative for surgeons specially in patients with osteoporosis.

Seismic damage assessment of steel reinforced recycled concrete column-steel beam composite frame joints

  • Dong, Jing;Ma, Hui;Zhang, Nina;Liu, Yunhe;Mao, Zhaowei
    • Earthquakes and Structures
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    • v.14 no.1
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    • pp.73-84
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    • 2018
  • Low cyclic loading tests are conducted on the steel reinforced recycled concrete (SRRC) column-steel (S) beam composite frame joints. This research aims to evaluate the earthquake damage performance of composite frame joints by performing cyclic loading tests on eight specimens. The experimental failure process and failure modes, load-displacement hysteresis curves, characteristic loads and displacements, and ductility of the composite frame joints are presented and analyzed, which shows that the composite frame joints demonstrate good seismic performance. On the basis of this finding, seismic damage performance is examined by using the maximum displacement, energy absorbed in the hysteresis loops and Park-Ang model. However, the result of this analysis is inconsistent with the test failure process. Therefore, this paper proposes a modified Park-Ang seismic damage model that is based on maximum deformation and cumulative energy dissipation, and corrected by combination coefficient ${\alpha}$. Meanwhile, the effects of recycled coarse aggregate (RCA) replacement percentage and axial compression ratio on the seismic damage performance are analyzed comprehensively. Moreover, lateral displacement angle is used as the quantification index of the seismic performance level of joints. Considering the experimental study, the seismic performance level of composite frame joints is divided into five classes of normal use, temporary use, repair after use, life safety and collapse prevention. On this basis, the corresponding relationships among seismic damage degrees, seismic performance level and quantitative index are also established in this paper. The conclusions can provide a reference for the seismic performance design of composite frame joints.

Local Buckling of Built-up Square Tubular Compression Members Fabricated with HSA800 High Performance Steels under Concentric Axial Loading (중심압축력을 받는 건축구조용 고성능강(HSA800) 용접 각형강관 압축재의 국부좌굴)

  • Yoo, Jung-Han;Kim, Joo-Woo;Yang, Jae-Keun;Kang, Joo-Won;Lee, Dong-Woo
    • Journal of Korean Society of Steel Construction
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    • v.24 no.4
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    • pp.435-442
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    • 2012
  • Recently, high performance(strength) steels have been utilized to structural materials in buildings and bridges with the demand for high-rise and long-span of main structures. This paper is a series of basic study for the design specification of structural members using high performance steel, material properties of high performance rolled steel building structures. HSA800 was compared with the requirements of Korean Standards(KS) for HSA800. Welded square tube stub columns with variables of width-to-thickness ratios are planned in order to investigate the local buckling behaviors and check the current design limit of width-to-thickness ratio and uniaxial compressive tests are carried out. In addition, the local buckling behaviors of stub columns obtained finite element analysis were compared with those of test results.

Multi-Scale Heterogeneous Fracture Modeling of Asphalt Mixture Using Microfabric Distinct Element Approach

  • Kim Hyun-Wook;Buttler William G.
    • International Journal of Highway Engineering
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    • v.8 no.1 s.27
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    • pp.139-152
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    • 2006
  • Many experimental and numerical approaches have been developed to evaluate paving materials and to predict pavement response and distress. Micromechanical simulation modeling is a technology that can reduce the number of physical tests required in material formulation and design and that can provide more details, e.g., the internal stress and strain state, and energy evolution and dissipation in simulated specimens with realistic microstructural features. A clustered distinct element modeling (DEM) approach was implemented In the two-dimensional particle flow software package (PFC-2D) to study the complex behavior observed in asphalt mixture fracturing. The relationship between continuous and discontinuous material properties was defined based on the potential energy approach. The theoretical relationship was validated with the uniform axial compression and cantilever beam model using two-dimensional plane strain and plane stress models. A bilinear cohesive displacement-softening model was implemented as an intrinsic interface and applied for both homogeneous and heterogeneous fracture modeling in order to simulate behavior in the fracture process zone and to simulate crack propagation. A disk-shaped compact tension test (DC(T)) with heterogeneous microstructure was simulated and compared with the experimental fracture test results to study Mode I fracture. The realistic arbitrary crack propagation including crack deflection, microcracking, crack face sliding, crack branching, and crack tip blunting could be represented in the fracture models. This micromechanical modeling approach represents the early developmental stages towards a 'virtual asphalt laboratory,' where simulations of laboratory tests and eventually field response and distress predictions can be made to enhance our understanding of pavement distress mechanisms, such its thermal fracture, reflective cracking, and fatigue crack growth.

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Nonlinear Analysis of RC Shell Structures Including Creep and Shrinkage Effects (크리프와 건조수축을 고려한 RC쉘 구조물의 비선형 해석)

  • 정진환;한충목;조현영
    • Magazine of the Korea Concrete Institute
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    • v.5 no.2
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    • pp.181-188
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    • 1993
  • In this study, a numerical method for the material nonlinear analysis of reinforced concrete shell structures including the time dependent effects due to creep and shrinkage is developed. Degenerate shell elements with the layered approach are used. The perfect or strain hardening plasticity model in compression and the linearly elastic model in tension until cracking for concrete are employed. The reinforcing bars are considered as a steel layer of equivalent thickness. Each :steel layer has an uniaxial behaviour resisting only the axial force in the bar direction. A bilinear idealization is adopted to model elasto-plastic stress-strain relationships. For the nonlinear anaysis, incremental load method combined with unbalanced load iterations for each load increment is used. To include time dependent effects of concrete, time domain is divided into several time steps which may have different length. Some numerical examples are presented to study the validity and applicability of the present method. The results are compared with experimental and numerical results obtained by other investigator.

Optimization of Reinforced Concrete Frames Subjected to Dynamic Loads (동적 거동을 받는 철근 콘크리트 뼈대 구조의 최적화)

  • Park, Moon Ho;Kim, Sang Jin
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.14 no.3
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    • pp.439-452
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    • 1994
  • A method to optimize the cost of R/C frames and an algorithm of the optimal limit state design for R/C frames subjected to dynamic loads are presented. The modal superposition method was used to find the dynamic responses of the frames. Each member of R/C frame is made up of more than two elements and the stiffness matrix and consistent mass matrix of three d.o.f in the node of each element was used to include axial, shear and flexural effects. The objective function to be minimized formulated the cost of materials, steel and concrete, and optimised to satisfy the behaviors of R/C frame and each constraint imposed by the limit state requirements. Both objective function and each constraint are derived in terms of design variables which include the effective depth, beam width, compression and tension steel area, and column shear steel area. A few applications are presented which demonstrate the feasibility, the validity and efficiency of the algorithm for automated optimum design of R/C frames where dynamic behavior is to be considered.

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