• Title/Summary/Keyword: loading performance

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Experimentally evaluating the seismic retrofitting of square engineered cementitious composite columns using CFRP

  • Akhtari, Alireza;Mortezaei, Alireza;Hemmati, Ali
    • Structural Engineering and Mechanics
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    • v.78 no.5
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    • pp.545-556
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    • 2021
  • The present experimental study evaluated the seismic performance of six engineered cementitious composite (ECC) columns strengthened with carbon fiber reinforced polymer (CFRP) laminates under cyclic lateral loading. The ECC columns damaged and crushed in the first stage of cyclic tests were repaired using the ECC with a certain polyvinyl alcohol (PVA) fiber and strengthened with flexural and sheer CFRP laminates and then re-assessed under the cyclic loading. The effects of some variables were examined on lateral displacement, energy absorption and dissipation, failure modes, crack patterns, load bearing capacity and plasticity, and the obtained results were compared with those of the first stage of cyclic tests. The results showed that retrofitting the ECC columns can improve their performance, plasticity and load-bearing threshold, delayed the concrete failure, changed the failure modes and increased the energy absorbed by the strengthened columns element by over 50%.

Nitrification Performance of a Moving Bed Bioreactor (MBBR) at Different Ammonia and Hydraulic Air-Loading Rates under Seawater Conditions (해수 조건에서 총암모니아성 질소 부하량과 수리학적 공기 부하량에 따른 유동상 여과조의 질산화 성능 평가)

  • Jaegeon Lee;Younghun Lee;Jeonghwan Park
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.56 no.6
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    • pp.870-877
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    • 2023
  • The purpose of this study was to assess the efficiency of nitrification based on ammonia loading rates and hydraulic air-loading rates in a moving bed bioreactor (MBBR) under seawater conditions. The goal was to provide foundational data for the design of these bio reactors. At an ammonia loading rate of 0.2 g TAN·m-2 surface area·day-1, the influent TAN concentration was determined to be 1.76±0.33 mg·L-1, which is below the safe concentration for fish survival (2 mg·L-1). Considering operational aspects, the optimal ammonia-loading rate was derived. Subsequently, experimental results for nitrification efficiency at the optimal ammonia-loading rate revealed that the optimum hydraulic air-loading rate was 1.8 L·air·m-2 surface area·min-1. This condition resulted in the lowest concentrations of TAN and NO2-N in the influent water, thus establishing the optimal hydraulic air-loading rate. A regression equation was derived for the ammonia-removal rate (Y) based on the ammonia-loading rate (x) and expressed as a 0.5-order equation (Y=ax0.5+b). Specifically, for TAN concentrations of 0-6 mg·L-1, the regression equation Y=0.1683x0.5-0.13628, was established.

The Effect of Performance on Loading Impact of Emulsion Explosive in Long Vertical Borehole (에멀젼 폭약의 수직 장공 장약 시 낙하 충격에 의한 성능 영향)

  • Lee, Young-Ho;Lee, Seung-Chan;Lee, Eung-So
    • Explosives and Blasting
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    • v.25 no.1
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    • pp.45-52
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    • 2007
  • When emulsion explosives(1kg/cartridge) are loaded into a long vertical borehole at open blasting site, they undergo an Impact corresponding to 117.6J of shock energy. After shocking. the crystallization of emulsion nay happen immediately. Furthermore, it nay cause a desensitization, arising from increase in the density of emulsion explosive by the breakage of sensitizer. In this paper, some experimental work was performed using PVC pipe equipment(50mm diameter and 12m lengths) to investigate the effects of loading impart of emulsion explosive. It is shown that detonation energy decreases up to 26% of the normal state value and this effect is less than 3% of the total performance of emulsion explosives in borehole blasting.

Influence of connection detailing on the performance of wall-to-wall vertical connections under cyclic loading

  • Hemamalini, S.;Vidjeapriya, R.
    • Advances in concrete construction
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    • v.9 no.5
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    • pp.437-448
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    • 2020
  • In high rise buildings that utilize precast large panel system for construction, the shear wall provides strength and stiffness during earthquakes. The performance of a wall panel system depends mainly on the type of connection used to transfer the forces from one wall element to another wall element. This paper presents an experimental investigation on different types of construction detailing of the precast wall to wall vertical connections under reverse cyclic loading. One of the commonly used connections in India to connect wall to wall panel is the loop bar connection. Hence for this study, three types of wet connections and one type of dry connection namely: Staggered loop bar connection, Equally spaced loop bar connection, U-Hook connection, and Channel connection respectively were used to connect the precast walls. One third scale model of the wall was used for this study. The main objective of the experimental work is to evaluate the performance of the wall to wall connections in terms of hysteretic behaviour, ultimate load carrying capacity, energy dissipation capacity, stiffness degradation, ductility, viscous damping ratio, and crack pattern. All the connections exhibited similar load carrying capacity. The U-Hook connection exhibited higher ductility and energy dissipation when compared to the other three connections.

Micro-concrete composites for strengthening of RC frame made of recycled aggregate concrete

  • Marthong, Comingstarful;Pyrbot, Risukka N.;Tron, Stevenly L.;Mawroh, Lam-I D.;Choudhury, Md. Sakil A.;Bharti, Ganesh S.
    • Computers and Concrete
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    • v.22 no.5
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    • pp.461-468
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    • 2018
  • In this paper, to access the suitability of recycled aggregate for structural applications, concrete strength i.e., compressive, tensile and flexural strength were evaluated and compared with those specimens made of natural aggregates. Test results indicated that 30 to 42% of the mentioned strength decreases. To study the performance of frame structures made of recycled aggregate concrete (RAC) two reinforced RAC frames were prepared and tested under monotonic loading. The joint regions of one of the RAC frame were casted with micro-concrete. A reference specimen was also prepared using natural aggregate concrete (NAC) and subjected to a similar loading condition. The RAC frame resulted in a brittle mode of failure as compared to NAC frame. However, the presence of a micro-concrete at the joint region of an RAC frame improved the damage tolerance and load resisting capacity. Seismic parameter such as energy dissipation, ductility and stiffness also improves. Conclusively, strengthening of joint region using micro-concrete is found to have a significant contribution in improving the seismic performance of an RAC frame.

Development of Rutting Prediction Model of Flexible Pavement using Repetitive Axial Loading Test (반복 축하중 시험을 이용한 연성포장의 소성변형 예측모델 개발)

  • Kim, Nakseok
    • Journal of the Society of Disaster Information
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    • v.13 no.4
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    • pp.491-498
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    • 2017
  • The primary objective of this research is to develop a rutting performance prediction model of flexible pavement. Extensive laboratory testings were conducted to achieve the objective. A new test method employing repetitive axial loading with confinement was also adopted to estimate the rutting performance of asphalt concrete in the research. The rutting prediction model employes a layer-strain theory. The required rutting coefficients for the prediction model were determined through the laboratory rutting characterizations of the asphalt concrete layer materials. Within the limits of this study, a laboratory rutting prediction model of flexible pavement using repetitive axial loading test was presented. It is noted that the developed rutting prediction model simulates propery the behaviors of flexible pavement layer materials.

SFRHPC interior beam-column-slab joints under reverse cyclic loading

  • Ganesan, N.;Nidhi, M.;Indira, P.V.
    • Advances in concrete construction
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    • v.3 no.3
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    • pp.237-250
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    • 2015
  • Beam-column joints are highly vulnerable locations which are to be designed for high ductility in order to take care of unexpected lateral forces such as wind and earthquake. Previous investigations reveal that the addition of steel fibres to concrete improves its ductility significantly. Also, due to presence of slab the strength and ductility of the beam increases considerably and ignoring the effect of slab can lead to underestimation of beam capacity and defiance of strong column weak beam concept. The influence of addition of steel fibres on the strength and behaviour of steel fibre reinforced high performance concrete (SFRHPC) interior beam-column-slab joints was investigated experimentally. The specimens were subjected to reverse cyclic loading. The variable considered was the volume fraction of crimped steel fibres i.e., 0%, 0.5% and 1.0%. The results show that the addition of steel fibres improves the first crack load, strength, ductility, energy absorption capacity and initial stiffness of the beam.

Study on seismic performance of steel frame with archaized-style under pseudo-dynamic loading

  • Liu, Zuqiang;Zhou, Chaofeng;Xue, Jianyang
    • Earthquakes and Structures
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    • v.17 no.1
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    • pp.39-48
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    • 2019
  • This paper presents an experimental study on a 1/2 scale steel frame with archaized-style under the pseudo-dynamic loading. Four seismic waves, including El Centro wave, Taft wave, Lanzhou wave and Wenchuan wave, were input during the test. The hysteresis characteristic, energy dissipation acceleration response, displacement response, strength, stiffness and strain were analyzed. Based on the experiment, the elastoplastic dynamic time-history analysis was carried out with the software ABAQUS. The stress distribution and failure mode were obtained. The results indicate that the steel frame with archaized-style was in elastic stage when the peak acceleration of input wave was no more than 400 gal. Under Wenchuan wave with peak acceleration of 620 gal, the steel frame enters into the elastoplastic stage, the maximum inter-story drift was 1/203 and the bearing capacity still tended to increase. During the loading process, Dou-Gong yielded first and played the role of the first seismic fortification line, and then beam ends and column bottom ends yielded in turn. The steel frame with archaized-style has good seismic performance and meets the seismic design requirement of Chinese code.

Seismic Performance Test of a Steel Frame with Multi-action Hybrid Dampers (다중거동 복합형 감쇠장치를 적용한 철골골조의 내진성능실험)

  • Roh, Ji Eun;Heo, Seok Jae;Lee, Sang Hyun
    • Journal of the Earthquake Engineering Society of Korea
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    • v.23 no.1
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    • pp.1-8
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    • 2019
  • In this study, the effectiveness of a multi-action hybrid damper (MHD) composed of lead rubber bearing (LRB) and friction pad was verified in terms of seismic performance improvement of a frame structure. The LRB and the friction elements are connected in series, so the LRB governs the intial small deformation and the friction determines large deformation behavior. Cyclic loading tests were conducted by using a half scale steel frame structure with the MHD, and the results indicated that the structure became to have the stable trilinear hysteresis with large initial stiffness and first yielding due to the LRB, and the second yielding due to the friction. The MHD could significantly increase the energy dissipation capacity of the structure and the hysteresis curves obtained by tests were almost identical to the analytically estimated ones.

An Experimental Study on the Structural Performance of Steel Beam with Opening Close to End Subjected to Cyclic Loading (반복하중을 받는 단부에 근접한 개구부를 갖는 강재보의 구조성능에 관한 실험적 연구)

  • Han, Dong-Ho
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.2
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    • pp.66-73
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    • 2021
  • In the existing study of steel beams with openings, openings are located at a location where the distance to the support point is equal to or greater than the section height. Considering the facilities using the openings in the steel beam, the distance from the opening to the support point may be closer than the height of the beam section. Therefore, research on this is needed. This study is an experimental study to understand the structural performance of beams with openings close to the ends subjected to Cyclic Loading. In addition, in this study, we want to understand the structural performance through experiments on beams with openings reinforced with vertical or horizontal steel plates.