• 제목/요약/키워드: Prediction of Concrete Strength

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Prediction of the Shear Strength of FRP Strengthened RC Beams (II) - Verification and parametric study - (FRP로 보강된 철근 콘크리트보의 전단강도 예측 (II) - 모델 검증 및 변수연구 -)

  • Sim Jong-Sung;Park Cheol-Woo;Moon Do-Young;Sim Jae-Won
    • Journal of the Korea Concrete Institute
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    • v.17 no.3 s.87
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    • pp.353-359
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    • 2005
  • To evaluate the proposed shear strength models developed in a companion paper, the shear strengths of test specimens strengthened with FRP were predicted by ACl specification, and elsewhere. The advantage and disadvantage of the models were investigated by the comparisons with the test results. The characteristics and limitations of the existing model were investigated with respect to FRP types, strengthening methods, shear span to depth ratio and effective strength of FRP. The results of this parametric study showed that the proposed shear strength model is more accurate than other models.

Prediction of Compressive Behavior of FRP-Confined Concrete Based on the Three-Dimensional Constitutive Laws (3차원 구성관계를 고려한 FRP-구속 콘크리트의 압축거동 예측모델)

  • Cho Chang-Geun;Kwon Min-ho
    • Journal of the Korea Concrete Institute
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    • v.16 no.4 s.82
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    • pp.501-509
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    • 2004
  • The proposed model can predict the compressive behaviors of concrete confined with fiber reinforced polymer (FRP) jacket. To model confining concrete by FRP jackets, the hypoelasticity-based constitutive law of concrete In tri-axial stress states has been presented. The increment of strength of concrete has been determined by the failure surface of concrete in tri-axial states, and its corresponding peak strain is computed by the strain enhancement factor that is proposed in the present study, Therefore, the newly proposed model is a load-dependent confinement model of concrete wrapped by FRP jackets to compare the previous models which are load-independent confinement models. The behavior of FRP jackets has been modeled using the mechanics of orthotropic laminated composite materials in two-dimension. The developed model is implemented into the incremental analysis of compressive tests. The verification study with several different experiments shows that the model is able to adequately capture the behavior of the compression test by including better estimations of the axial responses as well as the lateral response of FRP-confined concrete cylinders.

Analysis of side-plated reinforced concrete beams with partial interaction

  • Siu, W.H.;Su, R.K.L.
    • Computers and Concrete
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    • v.8 no.1
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    • pp.71-96
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    • 2011
  • Existing reinforced concrete (RC) beams can be strengthened with externally bolted steel plates to the sides of beams. The effectiveness of this type of bolted side-plate (BSP) beam can however be affected by partial interaction between the steel plates and RC beams due to the mechanical slip of bolts. To avoid over-estimation of the flexural strength and ensure accurate prediction of the load-deformation response of the beams, the effect of partial interaction has to be properly considered. In this paper, a special non-linear macro-finite-element model that takes into account the effects of partial interaction is proposed. The RC beam and the steel plates are modelled as two different elements, interacting through discrete groups of bolts. A layered method is adopted for the formulation of the RC beam and steel plate elements, while a special non-linear model based on a kinematic hardening assumption for the bolts is used to simulate the bolt group effect. The computer program SiBAN was developed based on the proposed approach. Comparison with the available experimental results shows that SiBAN can accurately predict the partial interaction behaviour of the BSP beams. Further numerical simulations show that the interaction between the RC beam and the steel plates is greatly reduced by the formation of plastic hinges and should be considered in analyses of the strengthened beams.

Behaviors of UHPC-filled Q960 high strength steel tubes under low-temperature compression

  • Yan, Jia-Bao;Hu, Shunnian;Luo, Yan-Li;Lin, Xuchuan;Luo, Yun-Biao;Zhang, Lingxin
    • Steel and Composite Structures
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    • v.43 no.2
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    • pp.201-219
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    • 2022
  • This paper firstly proposed high performance composite columns for cold-region infrastructures using ultra-high performance concrete (UHPC) and ultra-high strength steel (UHSS) Q960E. Then, 24 square UHPC-filled UHSS tubes (UHSTCs) at low temperatures of -80, -60, -30, and 30℃ were performed under axial loads. The key influencing parameters on axial compression performance of UHSS were studied, i.e., temperature level and UHSS-tube wall thickness (t). In addition, mechanical properties of Q960E at low temperatures were also studied. Test results revealed low temperatures improved the yield/ultimate strength of Q960E. Axial compression tests on UHSTCs revealed that the dropping environmental temperature increased the compression strength and stiffness, but compromised the ductility of UHSTCs; increasing t significantly increased the strength, stiffness, and ductility of UHSTCs. This study developed numerical and theoretical models to reproduce axial compression performances of UHSTCs at low temperatures. Validations against 24 tests proved that both two methods provided reasonable simulations on axial compression performance of UHSTCs. Finally, simplified theoretical models (STMs) and modified prediction equations in AISC 360, ACI 318, and Eurocode 4 were developed to estimate the axial load capacity of UHSTCs at low temperatures.

Shear Strength of One-way Hollow Slab According to Effective Cross Section and Reinforcement Ratio (유효단면 및 철근비에 따른 일방향 중공슬래브 전단강도)

  • Seok, Keun-Young;Ye, Sang-Min;Kang, Joo-Won
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.18 no.2
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    • pp.90-98
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    • 2014
  • The shear behavior of reinforced concrete structure is one of difficult problems that are not clearly identified theoretically despite the efforts of researchers for several years. Since bending and shear strength of hollow slab may decrease due to hollow part inside slab, prediction of such structure performance is very important. Presently the formulas of shear designing standard expressions of each country are formulas by experiment for hollow slab. In this study, the shear behavior of one-way hollow slab by reinforcement ratio were analyzed through experiment to conduct studying on estimation of shear strength, and then shear strength formulas of hollow slab were compared and analyzed.

Characteristics of Autogenous Shrinkage for Concrete Containing Blast-Furnace Slag (고로슬래그를 함유한 콘크리트의 자기수축 특성)

  • Lee Kwang-Myong;Kwon Ki-Heon;Lee Hoi-Keun;Lee Seung-Hoon;Kim Gyu-Yong
    • Journal of the Korea Concrete Institute
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    • v.16 no.5 s.83
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    • pp.621-626
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    • 2004
  • The use of blast-furnace slag (BFS) in making not only normal concrete but also high-performance concrete has several advantages with respect to workability, long-term strength and durability. However, slag concrete tends to show more shrinkage than normal concrete, especially autogenous shrinkage. High autogenous shrinkage would result in severe cracking if they are not controlled properly. Therefore, in order to minimize the shrinkage stress and to ensure the service life of concrete structures, the autogenous shrinkage behavior of concrete containing BFS should be understood. In this study, small prisms made of concrete with water-binder (cement+BFS) ratio (W/B) ranging from 0.27 to 0.42 and BFS replacement level of $0\%$, $30\%$, and $50\%$, were prepared to measure the autogenous shrinkage. Based on the test results, thereafter, material constants in autogenous shrinkage prediction model were determined. In particular, an effective autogenous shrinkage defined as the shrinkage that contributes to the stress development was introduced. Moreover, an estimation formula of the 28-day effective autogenous shrinkage was proposed by considering various W/B's. Test results showed that autogenous shrinkage increased with replacement level of BFS at the same W/B. Interestingly, the increase of autogenous shrinkage is dependent on the W/B at the same content of BFS; the lower W/B, the smaller increasing rate. In concluding, it is necessary to use the combination of other mineral admixtures such as shrinkage reducing admixture or to perform sufficient moisture curing on the construction site in order to reduce the autogenous shrinkage of BFS concrete.

Column Shortening prediction and Field measurement of Tall building with Transfer floor (전이층을 가진 초고층건물의 기둥축소량 예측 및 현장계측)

  • Song Hwa-Cheol;Cho Yong-Soo;Chung Sung-Jin;Yoon Kwang-Sup;Lee Woo-Ho
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2006.04a
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    • pp.175-181
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    • 2006
  • The prediction of time-dependent column shortening is essential for tall buildings considering both strength and serviceability aspects. The Column shortening of tall buildings with transfer floor should be calculated considering the long-term deflection of transfer girder. In this study, both the column shortening and the deflection of transfer girder of 45-story tall concrete building are predicted. The column shortening considering deflection of transfer girder are compared with the actual column shortening by field measurement.

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Identification of a suitable ANN architecture in predicting strain in tie section of concrete deep beams

  • Mohammadhassani, Mohammad;Nezamabadi-pour, Hossein;Suhatril, Meldi;Shariati, Mahdi
    • Structural Engineering and Mechanics
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    • v.46 no.6
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    • pp.853-868
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    • 2013
  • The comparison of the effectiveness of artificial neural network (ANN) and linear regression (LR) in the prediction of strain in tie section using experimental data from eight high-strength-self-compact-concrete (HSSCC) deep beams are presented here. Prior to the aforementioned, a suitable ANN architecture was identified. The format of the network architecture was ten input parameters, two hidden layers, and one output. The feed forward back propagation neural network of eleven and ten neurons in first and second TRAINLM training function was highly accurate and generated more precise tie strain diagrams compared to classical LR. The ANN's MSE values are 90 times smaller than the LR's. The correlation coefficient value from ANN is 0.9995 which is indicative of a high level of confidence.

Mechanical Properties of Cement Mortar: Development of Structure-Property Relationships

  • Ghebrab, Tewodros Tekeste;Soroushian, Parviz
    • International Journal of Concrete Structures and Materials
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    • v.5 no.1
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    • pp.3-10
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    • 2011
  • Theoretical models for prediction of the mechanical properties of cement mortar are developed based on the morphology and interactions of cement hydration products, capillary pores and microcracks. The models account for intermolecular interactions involving the nano-scale calcium silicate hydrate (C-S-H) constituents of hydration products, and consider the effects of capillary pores as well as the microcracks within the hydrated cement paste and at the interfacial transition zone (ITZ). Cement mortar was modeled as a three-phase material composed of hydrated cement paste, fine aggregates and ITZ. The Hashin's bound model was used to predict the elastic modulus of mortar as a three-phase composite. Theoretical evaluation of fracture toughness indicated that the frictional pullout of fine aggregates makes major contribution to the fracture energy of cement mortar. Linear fracture mechanics principles were used to model the tensile strength of mortar. The predictions of theoretical models compared reasonably with empirical values.

Ultimate axial load of rectangular concrete-filled steel tubes using multiple ANN activation functions

  • Lemonis, Minas E.;Daramara, Angeliki G.;Georgiadou, Alexandra G.;Siorikis, Vassilis G.;Tsavdaridis, Konstantinos Daniel;Asteris, Panagiotis G.
    • Steel and Composite Structures
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    • v.42 no.4
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    • pp.459-475
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    • 2022
  • In this paper a model for the prediction of the ultimate axial compressive capacity of square and rectangular Concrete Filled Steel Tubes, based on an Artificial Neural Network modeling procedure is presented. The model is trained and tested using an experimental database, compiled for this reason from the literature that amounts to 1193 specimens, including long, thin-walled and high-strength ones. The proposed model was selected as the optimum from a plethora of alternatives, employing different activation functions in the context of Artificial Neural Network technique. The performance of the developed model was compared against existing methodologies from design codes and from proposals in the literature, employing several performance indices. It was found that the proposed model achieves remarkably improved predictions of the ultimate axial load.