• Geomechanics and Engineering
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• v.27 no.5
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• pp.511-525
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• 2021

In the design of underground excavation, the shear strength (SS) is a key characteristic. It describes the way the rock material resists the shear stress-induced deformations. In general, the measurement of the parameters related to rock shear strength is done through laboratory experiments, which are costly, damaging, and time-consuming. Add to this the difficulty of preparing core samples of acceptable quality, particularly in case of highly weathered and fractured rock. This study applies rock index test to the indirect measurement of the SS parameters of shale. For this aim, two efficient artificial intelligence methods, namely (1) adaptive neuro-fuzzy inference system (ANFIS) implemented by subtractive clustering method (SCM) and (2) support vector regression (SVR) optimized by Harmony Search (HS) algorithm, are proposed. Note that, it is the first work that predicts the SS parameters of shale through ANFIS-SCM and SVR-HS hybrid models. In modeling processes of ANFIS-SCM and SVR-HS, the results obtained from the rock index tests were set as inputs, while the SS parameters were set as outputs. By reviewing the obtained results, it was found that both ANFIS-SCM and SVR-HS models can provide acceptable predictions for interlocking and friction angle parameters, however, ANFIS-SCM showed a better generalization capability.

• International Journal of Concrete Structures and Materials
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• v.8 no.2
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• pp.117-128
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• 2014

Numerous investigations of RC beams strengthened in shear with externally-bonded (EB) fibre-reinforced polymer (FRP) sheets, plates and strips have been successfully conducted in recent years. These valuable studies have highlighted a number of influencing parameters that are not captured by the design guidelines. The objective of this study was: (1) to highlight experimentally and analytically the influential parameters on the shear contribution of FRP to RC beams strengthened in shear using EB FRP sheets and strips; and (2) to develop a set of transparent, coherent, and evolutionary design equations to calculate the shear resistance of RC beams strengthened in shear. In the experimental part of this study, 12 tests were performed on 4,520-mm-long T-beams. The specimens were strengthened in shear using carbon FRP (CFRP) strips and sheets. The test variables were: (1) the presence or absence of internal transverse-steel reinforcement; (2) use of FRP sheets versus FRP strips; and (3) the axial rigidity of the EB FRP reinforcement. In the analytical part of this study, new design equations were proposed to consider the effect of transverse-steel in addition to other influential parameters on the shear contribution of FRP. The accuracy of the proposed equations has been verified in this study by predicting the FRP shear contribution of experimentally tested RC beams.

• Geomechanics and Engineering
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• v.10 no.3
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• pp.257-267
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• 2016

Charts are used extensively in slope practical application to meet the need of quick assessment of rock slope design. However, Charts for estimating the shear strength of the rock mass of a slope are considerably limited. In this paper, based on the Hoek-Brown (HB) criterion which is widely used in rock slope engineering, we present charts which can be used to estimate the Mohr-Coulomb (MC) parameters angle of friction ${\phi}$ and cohesion c for given slopes. In order to present the proposed charts, we firstly present the derivation of the theoretical relationships between the MC parameters and ${\sigma}_{ci}/({\gamma}H)$ which is termed the strength ratio (SR). It is found that the values of $c/{\sigma}_{ci}$ and ${\phi}$ of a slope depend only on the magnitude of SR, regardless of the magnitude of the individual parameters ${\sigma}_{ci}$(uniaxial compressive strength), ${\gamma}$(unit weight) and H (slope height). Based on the relationships between the MC parameters and SR, charts are plotted to show the relations between the MC parameters and HB parameters. Using the proposed charts can make a rapid estimation of shear strength of rock masses directly from the HB parameters, slope geometry and rock mass properties for a given slope.

• Structural Engineering and Mechanics
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• v.83 no.5
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• pp.671-680
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• 2022

The shear capacity of beams is an essential parameter in designing beams carrying shear loads. Precise estimation of the ultimate shear capacity typically requires comprehensive calculation methods. For steel fiber reinforced concrete (SFRC) beams, traditional design methods may not accurately predict the interaction between different parameters affecting ultimate shear capacity. In this study, artificial neural network (ANN) modeling was utilized to predict the ultimate shear capacity of SFRC beams using ten input parameters. The results demonstrated that the ANN with 30 neurons had the best performance based on the values of root mean square error (RMSE) and coefficient of determination (R²) compared to other ANN models with different neurons. Analysis of the ANN model has shown that the clear shear span to depth ratio significantly affects the predicted ultimate shear capacity, followed by the reinforcement steel tensile strength and steel fiber tensile strength. Moreover, a Genetic Algorithm (GA) was used to optimize the ANN model's input parameters, resulting in the least cost for the SFRC beams. Results have shown that SFRC beams' cost increased with the clear span to depth ratio. Increasing the clear span to depth ratio has increased the depth, height, steel, and fiber ratio needed to support the SFRC beams against shear failures. This study approach is considered among the earliest in the field of SFRC.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.325-332
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• 2003

The tube structures act like cantilevered box beams and effectively resist lateral loads. In result, they are adopted as a high-rise buildings system. However, the shear lag in tube system prevents the idealized tube behavior such as a cantilevered box beam. Therefore, the studies on shear lag phenomena are necessarily requested. The presented papers are almost studied on framed tube structures and tube in tube structures. However, the study on the shear lag in the tube structure with core wall is lack. Thus, in this paper, the shear lag of the structure is studied. The shear lag coefficient is defined to investigate shear lag phenomena. However, existing shear lag coefficients are not adequate for understanding them. Therefore, on this study, new shear lag coefficient is suggested. In addition, the shear lag in the tube structure with core wall is analyzed by changing the five structural parameters of stiffness factor in frame, stiffness factor in wall, stiffness ratio, the number of stories and the number of bays.

• International Journal of Korean Welding Society
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• v.5 no.1
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• pp.15-28
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• 2005

The ball shear test was investigated in terms of the effects of test parameters, i.e., shear height and shear speed, with an experimental and non-linear finite element analysis for evaluating the solder joint integrity of area array packages. Two representative Pb-free solder compositions were examined in this work: Sn-3.5Ag-0.75Cu and In-48Sn. The substrate was a common SMD type with solder bond pad openings of 460 $\mu$m in diameter. The microstructural investigations were carried out using SEM, and the IMCs were identified with EDS. Shear tests were conducted with the two varying test parameters. It could be observed that increasing shear height, at fixed shear speed, has the effect of decreasing shear force for both Sn-3.5Ag-0.75Cu and In-48Sn solder joints, while the shear force increased with increasing shear speed at fixed shear height. Too high shear height could cause some undesirable effects on the test results such as unexpected high standard deviation values or shear tip sliding from the solder ball. The low shear height conditions were favorable for screening the type of brittle interfacial fractures or the degraded layers in the interfaces. The shear speed conditions were discussed with the stress analyses of the solder ball, and we cannot find any conspicuous finding which is related to optimum shear speed from the stress analyses.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.11c
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• pp.57-68
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• 1999

This paper summarizes the results of a study which uses the recently developed Optical Profile Microscopy technique (Dove and Frost, 1996) as the basis for investigating the role of geomembrane surface roughness on the shear mechanism of geomembrane/geotextile interfaces. The alternative roughness parameters which consider the direction of shearing are described. These directional parameters are compared with the existing roughness parameters, and the relationship between these directional and non-directional parameters are investigated. Then, the relationship between interface shear strength and surface roughness quantified at the interface is investigated. The results show that interface friction can be quantitatively related to the surface roughness of the geomembrane. The peak and residual interface strengths increase dramatically through the use of textured geomembranes as opposed to smooth geomembranes. For the smooth geomembranes, the sliding of the geotextile is the main shear mechanism. For the textured geomembranes, the peak interface strength is mainly mobilized through the micro-texture of the geomembrane, however, the residual interface strength is primarily attributed to macro scale surface roughness which pulls out and breaks the filaments from the geotextile. The results of this study can be extended to the other interfaces such as joints in rock mass, and also can be used to provide a quantitative framework that can lead to a significantly improved basis for the selection and design of geotextiles and geomembranes in direct contact.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.3
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• pp.93-100
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• 2015

The object of this paper is to study the shear characteristics of the weathered granite soil. To this end, a series of consolidated undrained triaxial compression tests are carried out to investigate the shear parameters-cohesion and internal friction angle-for the degree of saturation and degree of weathering. From the results, it is found that the shear parameters of weathered granite soil are influenced on the degree of saturation, degree of weathering and disturbance. Especially, internal friction angle is more influenced on the upper factors than cohesion. And shear parameters are more acted on the degree of saturation than the degree of weathering in the test range. It is, therefore, recommended that must be considered the conditions of granite soil-degree of saturation, degree of weathering and disturbance etc-in case of the calculation of bearing capacity, stability analysis and other designs with shear parameters.

• Computers and Concrete
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• v.22 no.2
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• pp.197-207
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• 2018

In the present study, group method of data handling networks (GMDH) are adopted and evaluated for shear strength prediction of both FRP-reinforced concrete members with and without stirrups. Input parameters considered for the GMDH are altogether 12 influential geometrical and mechanical parameters. Two available and very recently collected comprehensive datasets containing 112 and 175 data samples are used to develop new models for two cases with and without shear reinforcement, respectively. The proposed GMDH models are compared with several codes of practice. An artificial neural network (ANN) model and an ANFIS based model are also developed using the same databases to further assessment of GMDH. The accuracy of the developed models is evaluated by statistical error parameters. The results show that the GMDH outperforms other models and successfully can be used as a practical and effective tool for shear strength prediction of members without stirrups ($R^2=0.94$) and with stirrups ($R^2=0.95$). Furthermore, the relative importance and influence of input parameters in the prediction of shear capacity of reinforced concrete members are evaluated through parametric and sensitivity analyses.

• Geomechanics and Engineering
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• v.21 no.3
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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.