• Title/Summary/Keyword: load ratio

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Experiments on Second -Order Behavior of High Strength Concrete Columns (고강도 콘크리트 기둥의 2계 거동에 관한 실험적 연구)

  • 김진근;양주경
    • Proceedings of the Korea Concrete Institute Conference
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    • 1992.10a
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    • pp.167-172
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    • 1992
  • To analyze the effects compressive strength of concrete and longitudinal steel ratio on second-order moment of columns, 30tied rein reinforced concrete columns with hinged ends were tested. The 80mm square cross section was used and the amount of eccentricity was 24mm. The compressive strengths of column specimens with slenderness ratios of 10, 60, and 100were 250, 648 and 880kg/$\textrm{cm}^2$, and the longitudinal steel ratios were 1.98%(4-D6) and 3.95%(8-D6). The ratio of ultimate load capacity to that of short column with the same eccentricity (Pu/Pn) was much decreased at high slenderness ratio with increasing the compressive strength of concrete. And the lateral displacement of slender column at the ultimate load was decreased as the strength was increased. These are due to that at high slenderness ratio the load capacity and behavior of column are affected by flexural rigidity. And, it was also found that with increasing steel ratio, the value of Pu/Pn and the lateral displacement at the ultimate load were larger for the same slenderness ratio.

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A Study on the Fatigue Crack Growth Behavior in Residual Stress Field of the SS41 Welding Material (SS41 용접재의 잔류응력장내에서의 피로균열 성장거동에 관한 연구)

  • Choi, Byung-Ki
    • Journal of the Korean Society of Safety
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    • v.17 no.1
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    • pp.33-38
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    • 2002
  • SS41 material is welded automatically and is investigated some effects of the welding residual stress on the growth and propagation of fatigue crack, so as to study the fatigue behaviour in the welding residual stress field. The summarized results are as follows; 1) In case of the load amplitude is constant, as the stress ration is changing to 0.1, 0.33 and 0.5 the propagation life is constant but the initiation life decreases. And than, when maximum load or minimum load is constant, s the stress ration increases the initiation life and propagation life. 2) It was shown that the fatigue crack propagation ratio da/dn was almost constant regardless of the stress ratio change at constant load amplitude and that the larger stress ratio, the slower was the fatigue crack propagation ratio. 3) The opening ratio U is influenced by $K_{max}$ but it isn't only the function of $K_{max}$ because data range is very large. 4) The fatigue life of the specimens on tensile compressive residual stress field was decreased and increased respectably more than that of the base metal.

Parametric study on eccentrically-loaded partially encased composite columns under major axis bending

  • Begum, Mahbuba;Driver, Robert G.;Elwi, Alaa E.
    • Steel and Composite Structures
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    • v.19 no.5
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    • pp.1299-1319
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    • 2015
  • This paper presents a detailed parametric study, conducted using finite element tools to cover a range of several geometric and material parameters, on the behaviour of thin-walled partially encased composite (PEC) columns. The PEC columns studied herein are composed of thin-walled built-up H-shaped steel sections with concrete infill cast between the flanges. Transverse links are provided between the opposing flanges to improve resistance to local buckling. The parametric study is confined to eccentrically-loaded columns subjected to major axis bending only. The parameters that were varied include the overall column slenderness ratio (L/d), load eccentricity ratio (e/d), link spacing-to-depth ratio (s/d), flange plate slenderness ratio (b/t) and concrete compressive strength ($f_{cu}$). The overall column slenderness ratio was chosen to be the primary variable with values of 5, 10 and 15. Other parameters were varied within each case of L/d ratio. The effects of the selected parameters on the behaviour of PEC columns were studied with respect to the failure mode, peak axial load, axial load versus average axial strain response, axial load versus lateral displacement response, moment versus lateral displacement behaviour and the axial load-moment interaction diagram. The results of the parametric study are presented in the paper and the influences of each of the parameters investigated are discussed.

Indeterminate Strut-Tie Model and Load Distribution Ratio of Continuous RC Deep Beams (I) Proposal of Model & Load Distribution Ratio (연속지지 RC 깊은 보의 부정정 스트럿-타이 모델 및 하중분배율 (I) 모델 및 하중분배율의 제안)

  • Kim, Byung-Hun;Chae, Hyun-Soo;Yun, Young-Mook
    • Journal of the Korea Concrete Institute
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    • v.23 no.1
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    • pp.3-12
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    • 2011
  • The structural behavior of continuous reinforced concrete deep beams is mainly controlled by the mechanical relationships associated with the shear span-to-effective depth ratio, flexural reinforcement ratio, load and support conditions, and material properties. In this study, a simple indeterminate strut-tie model which reflects characteristics of the complicated structural behavior of the continuous deep beams is presented. In addition, the reaction and load distribution ratios defined as the fraction of load carried by an exterior support of continuous deep beam and the fraction of load transferred by a vertical truss mechanism, respectively, are proposed to help structural designers for the analysis and design of continuous reinforced concrete deep beams by using the strut-tie model approaches of current design codes. In the determination of the load distribution ratio, a concept of balanced shear reinforcement ratio requiring a simultaneous failure of inclined concrete strut and vertical steel tie is introduced to ensure a ductile shear failure of reinforced concrete deep beams, and the primary design variables including the shear span-to-effective depth ratio, flexural reinforcement ratio, and concrete compressive strength are implemented after thorough parametric numerical analyses. In the companion paper, the validity of the presented model and load distribution ratio was examined by applying them in the evaluation of the ultimate strength of multiple continuous reinforced concrete deep beams, which were tested to failure.

Behavior of Geogrid-Reinforced Soil with Cyclic plate Load Test (반복 평판재하시험을 통한 지오그리드 보강지반의 거동 특성)

  • 신은철;김두환;이상조;이규진
    • Proceedings of the Korean Geotechical Society Conference
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    • 1999.10a
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    • pp.285-292
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    • 1999
  • The cyclic plate load test were peformed to determine the behavior of reinforced soft ground with multiple layers of geogrid. Five series of test were conducted with varying the soil profile conditions which including the ground level, type of soil, and the thickness of each soil layer. The plate load test equipment was slightly modified to apply the cyclic load. Based on the cyclic plate load test results, the bearing capacity ratio(BCR), subbase modules, shear modules, the elastic rebound ratio, and reinforcing parameters are presented.

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Numerical study on RC flat plates subjected to combined axial and transverse load

  • Park, Honggun
    • Structural Engineering and Mechanics
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    • v.8 no.2
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    • pp.137-150
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    • 1999
  • This paper presents a numerical study on the flat plates in deep basements, subjected to floor load and in-plane compressive load due to soil and hydraulic lateral pressure. For nonlinear finite element analysis, a computer program addressing material and geometric nonlinearities is developed. The validity of the numerical model is established by comparison with existing experiments performed on plates simply supported on four edges. The flat plates to be studied are designed according to the Direct Design Method in ACI 318-95. Through numerical study on the effects of different load combinations and loading sequence, the load condition that governs the strength of the flat plates is determined. For plates under the governing load condition, parametric studies are performed to investigate the strength variations with reinforcement ratio, aspect ratio, concrete strength, and slenderness ratio. Based on the numerical results, the floor load magnification factor is proposed.

Evaluation of Effective Rainfall Ratio Method for Estimating Unit Load from Paddy Fields (비우량 방법에 의한 논 오염부하 원단위 산정시 적용성 평가)

  • Jung, Jae-Woon;Yoon, Kwang-Sik;Yoon, Suk-Gun;Choi, Woo-Jung;Choi, Woo-Young;Huh, Yu-Jeong;Cho, Kyeong-Min;Hong, Jung-Jin
    • Journal of Korean Society on Water Environment
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    • v.25 no.6
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    • pp.849-854
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    • 2009
  • Pollutant unit load (unit-load) reported by Ministry of Environment (MOE) in 1995 has been a useful method for watershed management and environmental policy decision. The unit-load has been estimated using effective rainfall ratio method. However, reliability of unit-load determined by the method has been criticized especially for paddy field and upland conditions. In this paper the unit-load of paddy field estimated by effective rainfall ratio method was compared with continuous monitoring data. Annual loads was simulated by the method choosing 5~6 storm events randomly from whole events collected. Probability distribution of difference between results by the method and measured data was investigated. The results showed that unit-load derived by the method was generally lesser than measured unit-load and showed wide variations. Therefore, unit-load estimation of paddy fields by effective rainfall ratio method need caution.

An Experimental Study on Seismic Performance of Reinforced Concrete Bridge Columns under Lateral Cyclic Load (반복 횡하중을 받는 철근콘크리트 교각의 내진성능에 관한 실험적 연구)

  • 이진옥;윤현도;황선경;류효진;나홍성;이경준
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.161-164
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    • 2003
  • This experimental investigation was conducted to examine the seismic performance of reinforced concrete bridge columns. The columns were subjected to a constant axial load and a cyclic horizontal load-inducing reversed bending moment. The variables studied in this research are the volumetric ratio of transverse reinforcement ($P_s$ =0.96, 1.44 per cent) and axial load ratio (0.05, 0.1, 0.2 P/$P_o$). Test results show that bridge columns with 50 per cent higher amounts of transverse reinforcement than that required by seismic provisions of ACI 318-02 showed ductile behaviour. For bridge columns with axial load ratio(P/$P_o$) less than 0.2, the ratio of $M_{max}$ over $M_{aci}$, nominal moment capacity predicted by ACI 318-02 provisions, is consistently greater than 1 with approximately a 20 percent margin of safty.

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Evaluation of Fatigue Strength of Weld According to Load of Piping materials for Water Supply and Drainage (상.하수도 배관재 용접부의 하중에 따른 피로강도 평가)

  • Park, Keyung-Dong;Ryu, Hyoung-Ju
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2005.11a
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    • pp.224-225
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    • 2005
  • The lightness of components required on marine and shipbuilding industry is requiring high strength of components. In particular, fatigue failure phenomena, which happen in metal, bring on danger in human life and property. Therefore, antifatigue failure technology takes an important part of current industries. In this study, it was investigated about endurance and fatigue crack propagation rate of according to stress ratio of SMAW commonly using for welding structures in present. Fatigue crack propagation rate(da/dN) of low load(R=0.1) was lower than of high load(R=0.6) for piping weld. And in stage I, ${\Delta}$Kth, the threshold stress intensity factor of the weld under heavy load is higher than under small load. Fatigue life shows more improvement in the weld of stress ratio R=0.l than in the weld of stress ratio R=0.6.

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Electrical Characteristics of Disk-type Piezoelectric Transformer Poled with the Same Direction (동일 방향으로 분극된 디스크형 압전변압기의 전기적 특성)

  • 이종필;홍진웅
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.16 no.8
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    • pp.688-692
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    • 2003
  • For high voltage operation, a new type of piezoelectric transformer using radial vibration of disk, poled with the same direction was proposed. The piezoelectric ceramics was composed to PZT-PMN-PSN. The diameter and thickness of a disk type piezoelectric transformer were 45[mm]and 4[mm], respectively The surface ratio of driving electrode and generating electrode of the piezoelectric transformer was 2 : 1. The resonance characteristics of input admittance, step-up voltage ratio and power transmission efficiency of the piezoelectric transformer were measured by varying the load resistance(0.1∼70[kΩ]). As a result, both resonance frequency and step-up voltage ratio increased with increasing load resistance. The step-up voltage ratio was reached more than 60 times under no load resistance. The maximum efficiency of 97% at load resistance of 2kΩ was obtained.