• Title/Summary/Keyword: shear strength of concrete

Search Result 1,910, Processing Time 0.025 seconds

Engineering behavior of expansive soils treated with rice husk ash

  • Aziz, Mubashir;Saleem, Masood;Irfan, Muhammad
    • Geomechanics and Engineering
    • /
    • v.8 no.2
    • /
    • pp.173-186
    • /
    • 2015
  • The rapid urbanization in Pakistan is creating a shortage of sustainable construction sites with good soil conditions. Attempts have been made to use rice husk ash (RHA) in concrete industry of Pakistan, however, limited literature is available on its potential to improve local soils. This paper presents an experimental study on engineering properties of low and high plastic cohesive soils blended with 0-20% RHA by dry weight of soil. The decrease in plasticity index and shrinkage ratio indicates a reduction in swell potential of RHA treated cohesive soils which is beneficial for problems related to placing pavements and footings on such soils. It is also observed that the increased formation of pozzolanic products within the pore spaces of soil from physicochemical changes transforms RHA treated soils to a compact mass which decreases both total settlement and rate of settlement. A notable increase in friction angle with increase in RHA up to 16% was also observed in direct shear tests. It is concluded that RHA treatment is a cost-effective and sustainable alternate to deal with problematic local cohesive soils in agro-based developing countries like Pakistan.

Environmental Impact Characteristics Analysis of High-rise Structural System Based on Life Cycle Assessment (전과정평가 기법에 기반한 고층구조시스템의 환경영향특성 분석)

  • Kim, Rak-Hyun;Kim, Young-Hwa;Roh, Seung-Jun;Park, Sang-Hoon
    • Journal of Korean Association for Spatial Structures
    • /
    • v.22 no.4
    • /
    • pp.71-79
    • /
    • 2022
  • Recently, the construction of tall buildings utilized by high strength-concrete in the whole world is tending to be on the rise. The application of high-rise structural system in buildings results in the excellent cut-down effect in construction materials due to section reduction. Therefore, in order to investigate the CO2 and resource reduction effect for the high-rise structural system, comparisons of GWP and ADP in embodied energy of structural materlais between 4 type of high-rise structural system have been performed. As a result, GWP emission increased in the order of steel structure outrigger system, RC shear wall system, and RC outrigger system. On the other hand, ADP emissions increased in the order of RC shear wall system, RC outrigger system, and steel structure outrigger system.

Impact-resistant design of RC slabs in nuclear power plant buildings

  • Li, Z.C.;Jia, P.C.;Jia, J.Y.;Wu, H.;Ma, L.L.
    • Nuclear Engineering and Technology
    • /
    • v.54 no.10
    • /
    • pp.3745-3765
    • /
    • 2022
  • The concrete structures related to nuclear safety are threatened by accidental impact loadings, mainly including the low-velocity drop-weight impact (e.g., spent fuel cask and assembly, etc. with the velocity less than 20 m/s) and high-speed projectile impact (e.g., steel pipe, valve, turbine bucket, etc. with the velocity higher than 20 m/s), while the existing studies are still limited in the impact resistant design of nuclear power plant (NPP), especially the primary RC slab. This paper aims to propose the numerical simulation and theoretical approaches to assist the impact-resistant design of RC slab in NPP. Firstly, the continuous surface cap (CSC) model parameters for concrete with the compressive strength of 20-70 MPa are fully calibrated and verified, and the refined numerical simulation approach is proposed. Secondly, the two-degree freedom (TDOF) model with considering the mutual effect of flexural and shear resistance of RC slab are developed. Furthermore, based on the low-velocity drop hammer tests and high-speed soft/hard projectile impact tests on RC slabs, the adopted numerical simulation and TDOF model approaches are fully validated by the flexural and punching shear damage, deflection, and impact force time-histories of RC slabs. Finally, as for the two low-velocity impact scenarios, the design procedure of RC slab based on TDOF model is validated and recommended. Meanwhile, as for the four actual high-speed impact scenarios, the impact-resistant design specification in Chinese code NB/T 20012-2019 is evaluated, the over conservation of which is found, and the proposed numerical approach is recommended. The present work could beneficially guide the impact-resistant design and safety assessment of NPPs against the accidental impact loadings.

Behavior and Strength of Rib Stiffened SC Wall-slab Connection (리브 보강된 SC구조 벽-바닥 접합부의 거동 및 내력 평가)

  • Park, Joung Hak
    • Journal of Korean Society of Steel Construction
    • /
    • v.26 no.4
    • /
    • pp.349-359
    • /
    • 2014
  • Until now, wall-slab plate of steel plate concrete has been constructed by joint. But, the shear plate has problems in the workability as well as structural integrity. This study investigates the behavior and strength of rib stiffened SC wall-slab connection. Seven prototype specimens of wall-slab connections were fabricated and tested. the structural safety of the specimens was confirmed through the monotonic loading test. Based on the experimental observations, this study propose the strength formula of the joint was proposed. To enhance the reliability of the proposed strength formula, analytical verification was performed through inelastic finite element analysis. Effect of parameters, such as, load point, friction coefficient, on the joint strength was examined. The proposed formula yields a conservative value for most cases.

Experimental Study of Coupled Shearwalls with different Coupling Member (인방보의 형태에 따른 개구부가 있는 전단벽의 거동 특성에 대한 실험적 연구)

  • Bae, Baek-Il;Choi, Hyun-Ki;Choi, Yoon-Chel;Choi, Chang-Sik
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2008.04a
    • /
    • pp.37-40
    • /
    • 2008
  • Many engineers find the way of improving the old building's structural behavior in the remodeling project which is performed using artificial openings for merging two houses. This test was performed to verify the characteristics of coupling beams according to the shape of the openings. One of test specimen has rectangle shape and the other was made by the circle shaped opening and one has coupling member only as slabs. Additionally, three specimens which have openings have 23% ratio in opening area to total wall area. Consequently, solid type which have no opening area shows shear failure. In the case of CW-RBS which have rectangular shaped opening, cracks are developed in coupling beam significantly. And CW-CS which has circular opening failed in shear showing development of diagonal cracks at wall toes and wall mid-height. It is thought that degradation of the wall strength is under the control of the opening shape and coupling beam-wall connection area.

  • PDF

Seismic behavior of steel tube reinforced concrete bridge columns

  • Tian, Tian;Qiu, Wen-liang;Zhang, Zhe
    • Steel and Composite Structures
    • /
    • v.28 no.1
    • /
    • pp.63-71
    • /
    • 2018
  • This paper reports an experimental study that was accomplished to assess the seismic behavior of steel tube reinforced concrete bridge columns (SBCs). The motivation of this study was to verify a supposition that the core steel tube may be terminated at a rational position in the column to minimize the material cost while maintaining the seismic behavior of this composite column. Four SBC specimens were tested under combined constant axial load and cyclic reversed lateral loads. The unique variable in the test matrix was the core steel tube embedment length, which ranged from 1/3 to 3/3 of the column effective height. It is observed that SBCs showed two distinctly different failure patterns, namely brittle shear failure and ductile flexural failure. Tests results indicate that the hysteretic responses of SBCs were susceptible to the core steel tube embedment length. With the increase of this structural parameter, the lateral strength of SBC was progressively improved; the deformability and ductility, however, exhibited a tendency of first increase and then decrease. It is also found that in addition to maintained the rate of stiffness degradation and cumulative energy dissipation basically unchanged, both the ductility and deformability of SBC were significantly improved when the core steel tube was terminated at the mid-height of the column, and these were the most unexpected benefits accompanied with material cost reduction.

Improvement of the cyclic response of RC columns with inadequate lap splices-Experimental and analytical investigation

  • Kalogeropoulos, George I.;Tsonos, Alexander-Dimitrios G.
    • Earthquakes and Structures
    • /
    • v.16 no.3
    • /
    • pp.279-293
    • /
    • 2019
  • The overall seismic performance of existing pre 1960-70s reinforced concrete (RC) structures is significantly affected by the inadequate length of columns' lap-spliced reinforcement. Due to this crucial structural deficiency, the cyclic response is dominated by premature bond - slip failure, strength and stiffness degradation, poor energy dissipation capacity and low ductility. Recent earthquakes worldwide highlighted the importance of improving the load transfer mechanism between lap-spliced bars, while it was clearly demonstrated that the failure of lap splices may result in a devastating effect on structural integrity. Extensive experimental and analytical research was carried out herein, to evaluate the effectiveness and reliability of strengthening techniques applied to RC columns with lap-spliced reinforcement and also accurately predict the columns' response during an earthquake. Ten large scale cantilever column subassemblages, representative of columns found in existing pre 1970s RC structures, were constructed and strengthened by steel or RC jacketing. The enhanced specimens were imposed to earthquake-type loading and their lateral response was evaluated with respect to the hysteresis of two original and two control subassemblages. The main variables examined were the lap splice length, the steel jacket width and the amount of additional confinement offered by the jackets. Moreover, an analytical formulation proposed by Tsonos (2007a, 2019) was modified appropriately and applied to the lap splice region, to calculate shear stress developed in the concrete and predict if yielding of reinforcement is achieved. The accuracy of the analytical method was checked against experimental results from both the literature and the experimental work included herein.

Dynamic Behaviour of Masonry inFilled Reinforced Concrete Frames with Non-Seismic Details (진동대실험을 통한 비내진상세를 가지는 RC 골조의 조적채움벽 유무에 따른 동적 거동 평가)

  • Baek, Eun-Rim;Kim, Kyung-Min;Cheon, Ju-Hyun;Oh, Sang-Hoon;Lee, Sang-Ho
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.21 no.3
    • /
    • pp.121-129
    • /
    • 2017
  • In this paper, the shake table test for the masonry infilled reinforced concrete frame with non-seismic details was carried out in order to evaluate its dynamic behaviour and damage under seismic condition. The tested specimens were the RC frame and the masonry infilled RC frame and the dynamic characteristics, such as a resonant period, acceleration response, displacement response and base shear force response, were compared between them. As a result of the shake table test, RC frame specimen had flexural cracks at the top and bottom of the column and shear cracks at the joints. In the case of masonry infilled RC frame, the damage of the frame was relatively minor but the sliding cracks and diagonal shear cracks on the masonry wall were severe at the final excitation. The resonant period of infilled RC frame specimen was shorter than that of the RC frame specimen because the masonry infill contributed to increase the stiffness. The maximum displacement response of the infilled RC frame specimen was decreased by about 20% than the RC frame specimen. It was analyzed that the masonry infill wall applied in this study contributed to increase the lateral strength of the RC frame with non - seismic detail by about 2.2 times and the stiffness by about 1.6 times.

Seismic Performance of an Existing Low-Rise Reinforced Concrete Piloti Building Retrofitted by Steel Rod Damper (강봉댐퍼로 보강한 기존 저층 철근콘크리트 필로티 건물의 내진성능)

  • Baek, Eun Lim;Oh, Sang Hoon;Lee, Sang Ho
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.18 no.5
    • /
    • pp.241-251
    • /
    • 2014
  • In this study, shaking table test was carried out to evaluate the seismic behavior and performance of low-rise reinforced concrete (RC) piloti structures with and without retrofit. The specimens were designed considering the characteristics of existing building with pilotis such as natural period, distribution factor of strength and stiffness between columns and core wall on the first soft story. The test for the non-retrofit specimen showed that damage was concentrated on the stiffer member on the same floor as the core wall failed by shear fracture whereas columns experienced slight flexural cracks. Considering the failure mode of the non-retrofit specimen, the retrofit method using steel rod damper was presented for improving the seismic performance of piloti structures. The results of the test for retrofit specimen revealed that the retrofit method was effective for controlling the damage as the main RC structural members were not destroyed and most of input energy was dissipated by hysteretic behavior of the damper.

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

  • Hemamalini, S.;Vidjeapriya, R.
    • Advances in concrete construction
    • /
    • v.9 no.5
    • /
    • pp.437-448
    • /
    • 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.