• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1065-1078
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• 2009

The shear strength has been managed as an important factor in soil mechanics. The shear strength estimation model was developed to evaluate the shear strength using only a few soil properties by the linear regression analysis model which is one of the statistical methods. The shear strength is divided into two part; one is the internal friction angle ($\Phi$) and the other is the cohesion (c). Therefore, some valid soil factors among the results of soil tests are selected through the correlation analysis using SPSS and then the model are formulated by the linear regression analysis based on the relationship between factors. Also, the developed model is compared with the result of direct shear test to prove the rationality of model. As the results of analysis about relationship between soil properties and shear strength, the internal friction angle is highly influenced by the void ratio and the dry unit weight and the cohesion is mainly influenced by the void ratio, the dry unit weight and the plastic index. Meanwhile, the shear strength estimated by the developed model is similar with that of the direct shear test. Therefore, the developed model may be used to estimate the shear strength of soils in the same condition of study area.

• Structural Engineering and Mechanics
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• 제61권5호
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• pp.605-615
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• 2017

Shear failure of reinforced concrete (RC) beams is a major concern for structural engineers. It has been shown through various studies that the shear strength and ductility of RC beams can be improved by adding steel fibers to the concrete. An accurate model predicting the shear strength of steel fiber reinforced concrete (SFRC) beams will help SFRC to become widely used. An artificial neural network (ANN) model consisting of an input layer, a hidden layer of six neurons and an output layer was developed to predict the shear strength of SFRC slender beams without stirrups, where the input parameters are concrete compressive strength, tensile reinforcement ratio, shear span-to-depth ratio, effective depth, volume fraction of fibers, aspect ratio of fibers and fiber bond factor, and the output is an estimate of shear strength. It is shown that the model is superior to fourteen equations proposed by various researchers in predicting the shear strength of SFRC beams considered in this study and it is verified through a parametric study that the model has a good generalization capability.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.139-146
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• 2002

The characteristics and prediction model for the shear strength of unsaturated residual soils was studied. In order to investigate the influence of the net normal stress on the shear strength, unsaturated triaxial tests and SWCC tests were carried out varying the net normal stress, and the experimental data for unsaturated shear strength tests were compared with predicted shear strength envelopes using existing prediction models. It was shown that the soil - water characteristic curve and the shear strength of the unsaturated soil varied with the change of the net normal stress. Therefore, to achieve a truly descriptive shear strength envelope for unsaturated soils, tile effect of the normal stress on the contribution of matric suction to the shear strength has to be taken into consideration. In this paper, a modified prediction model for the unsaturated shear strength was proposed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.271-274
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• 2005

Existing strut-and-tie model cannot be applied to analysis of slender beams without shear reinforcement because shear transfer mechanism is not formed. In the present study, a new strut-and-tie model with rigid joint was developed. Basically, concrete strut is modeled as a frame element which can transfer shear force (or moment) as well as axial force. Employing Rankine failure criterion, failure strength due to shear-tension and shear-compression developed in compressive concrete strut was defined. For verification, various test specimens were analyzed and the results were compared with tests. The proposed strut-and-tie model predicted shear strength and failure displacement with reasonable precision, addressing the design parameters such as shear reinforcement, concrete compressive strength, and shear span ratio.

• Geomechanics and Engineering
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• 제21권3호
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• pp.247-258
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• 2020

The shear strength of unsaturated soils, a research hotspot in geotechnical engineering, has great guiding significance for geotechnical engineering design. Although kinds of calculation models for the shear strength of unsaturated soil have been put forward by predecessors, there is still need for new models to extensively consider the nonlinear variation of shear strength, particularly for the nonlinear effect of the net normal stress on the shear strength of unsaturated soil. Here, the shear strength of unsaturated soils is explored to study the nonlinear effects of net normal stress with the introduction of a general nonlinear Mohr-Coulomb (M-C) strength criterion, and the relationship between the matric suction (or suction stress) and degree of saturation (DOS) constructed by the soil-water characteristics curve (SWCC) of van Genuchten is also applied for unsaturated soil. Then, two calculation models (i.e., an envelope shell model and an effective stress model) are established for the shear strength of unsaturated soils under the nonlinear strength theory. In these two models, the curve of the shear strength of unsaturated soils versus the net normal stress exhibits a tendency to gently. Moreover, the proposed formulas have flexibility and convenience with five parameters (for the effective stress model) or six parameters (for the envelope shell model), which are from the M-C strength parameters of the saturated soil and fitting parameters of SWCC of van Genuchten. Thereafter, by comparison with the classical theory of the shear strength of unsaturated soils from some actual cases, the rationality and accuracy of the present models were verified.

• Structural Engineering and Mechanics
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• 제53권1호
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• pp.41-55
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• 2015

In this paper, a model for the evaluation of shear strength of fibre reinforced polymer (FRP)-reinforced concrete beams is given. The survey of literature indicates that the FRP reinforced beams tested with shear span to depth ratio less than or equal to 1.0 is limited. In this study, eight concrete beams reinforced with GFRP rebars without stirrups are cast and tested over shear span to depth ratio of 0.5 and 1.75. The concrete compressive strength is varied from 40.6 to 65.3 MPa. The longitudinal reinforcement ratio is varied from 1.16 to 1.75. The experimental shear strength and load-deflection response of the beams are determined and reported in this paper. A model is proposed for the prediction of shear strength of beams reinforced with FRP bars. The proposed model accounts for compressive strength of concrete, modulus of FRP rebar, longitudinal reinforcement ratio, shear span to depth ratio and size effect of beams. The shear strength of FRP reinforced concrete beams predicted using the proposed model is found to be in better agreement with the corresponding test data when compared with the shear strength predicted using the eleven models published in the literature. Design example of FRP reinforced concrete beam is also given in the appendix.

• Advances in concrete construction
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• 제10권3호
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• pp.185-193
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• 2020

An analytical model is developed in this paper to predict the shear capacity of reinforced concrete (RC) columns with corroded transverse reinforcements. The shear strength model for corroded RC columns is proposed based on modifying the existing strut-and-tie model, which considers the deformational compatibility between truss and arch mechanisms. The contributions to the shear strength from both truss and arch mechanisms are incorporated in the proposed model. The effects of corrosion level of transverse reinforcements are considered in the proposed model through the minimum residual cross-sectional area of transverse reinforcements and the reduction of concrete compressive strength for the cover area. The shear strengths calculated from the developed model are compared with the experimental results from Vu's study (2017), which consisted of RC columns with corroded transverse reinforcements showing shear failure under the cyclic loading. The comparison results indicate satisfactory correlations. Parametric studies are conducted based on the developed shear strength model to explore the effects of column axial loading, aspect ratios, transverse reinforcements and the corrosion levels in transverse reinforcements to the shear strength of RC columns with corroded transverse reinforcements.

• Structural Engineering and Mechanics
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• 제33권3호
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• pp.357-371
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• 2009

Test results of thirteen reinforced concrete corbels with shear span-to-depth ratio greater than unity are reported. The main variables studied were compressive strength of concrete, shear span-to-depth ratio and parameter of vertical stirrups. The test results indicate that the shear strengths of corbels increase with an increase in compressive strength of concrete and parameter of vertical stirrups. The shear strengths of corbels also increase with a decrease in shear span-to-depth ratio. The smaller the shear span-to-depth ratio of corbel, the larger the stiffness and the shear strength of corbel are. The higher the concrete strength of corbel, the higher the stiffness and the shear strength of corbel are. The larger the parameter of vertical stirrups, the larger the stiffness and the shear strength of corbel are. The softened strut-and-tie model for determining the shear strengths of reinforced concrete corbels is modified appropriately in this paper. The shear strengths predicted by the proposed model and the approach of ACI Code are compared with available test results. The comparison shows that the proposed model can predict more accurately the shear strengths of reinforced concrete corbels than the approach of ACI Code.

• 한국안전학회지
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• 제30권5호
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• pp.67-73
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• 2015

In this paper, the simple truss model was modified to predict the punching shear strength of long-span prestressed concrete (PSC) deck slabs under wheel load including the effects of transverse prestressing and long span length between girders. The strength of the compressive zone arounding punching cone was evaluated by the stiffness of inclined strut which was modified by considering aging effective modulus. The stiffness of springs which control lateral displacement of the roller supports consists of the steel reinforcement and prestressing which passed through the punching cone. Initial angle of struts was determined by the experimental observation to compensate for uncertainties in the complexities of the punching shear. The validity of computed punching shear strength by modified simple truss model was shown by comparing with experimental results and the experimental results were also compared with existing punching shear equations to determine level of predictability. The modified simple truss model appeared to better predict the punching shear strength of PSC deck slabs than other available equations. The punching shear strength, which was determined by snap-through critical load of modified simple truss model, can be used effectively to examine punching shear strength of long span PSC deck slabs.

• Structural Engineering and Mechanics
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• 제57권4호
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• pp.657-680
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• 2016

Reinforced concrete (RC) deep beams are structural members that predominantly fail in shear. Therefore, determining the shear strength of these types of beams is very important. The strut-and-tie method is commonly used to design deep beams, and this method has been adopted in many building codes (ACI318-14, Eurocode 2-2004, CSA A23.3-2004). In this study, the efficiency of artificial neural networks (ANNs) in predicting the shear strength of RC deep beams is investigated as a different approach to the strut-and-tie method. An ANN model was developed using experimental data for 214 normal and high-strength concrete deep beams from an existing literature database. Seven different input parameters affecting the shear strength of the RC deep beams were selected to create the ANN structure. Each parameter was arranged as an input vector and a corresponding output vector that includes the shear strength of the RC deep beam. The ANN model was trained and tested using a multi-layered back-propagation method. The most convenient ANN algorithm was determined as trainGDX. Additionally, the results in the existing literature and the accuracy of the strut-and-tie model in ACI318-14 in predicting the shear strength of the RC deep beams were investigated using the same test data. The study shows that the ANN model provides acceptable predictions of the ultimate shear strength of RC deep beams (maximum $R^2{\approx}0.97$). Additionally, the ANN model is shown to provide more accurate predictions of the shear capacity than all the other computed methods in this study. The ACI318-14-STM method was very conservative, as expected. Moreover, the study shows that the proposed ANN model predicts the shear strengths of RC deep beams better than does the strut-and-tie model approaches.