Ultimate lateral capacity of two dimensional plane strain rectangular pile in clay

Keawsawasvong, Suraparb,Ukritchon, Boonchai Techno-Press 2016 Geomechanics & engineering Vol.11 No.2

This paper presents a new numerical solution of the ultimate lateral capacity of rectangular piles in clay. The two-dimensional plane strain finite element was employed to determine the limit load of this problem. A rectangular pile is subjected to purely lateral loading along either its major or minor axes. Complete parametric studies were performed for two dimensionless variables including: (1) the aspect ratios of rectangular piles were studied in the full range from plates to square piles loaded along either their major or minor axes; and (2) the adhesion factors between the soil-pile interface were studied in the complete range from smooth surfaces to rough surfaces. It was found that the dimensionless load factor of rectangular piles showed a highly non-linear function with the aspect ratio of piles and a slightly non-linear function with the adhesion factor at the soil-pile interface. In addition, the dimensionless load factor of rectangular piles loaded along the major axis was significantly higher than that loaded along the minor axis until it converged to the same value at square piles. The solutions of finite element analyses were verified with the finite element limit analysis for selected cases. The empirical equation of the dimensionless load factor of rectangular piles was also proposed based on the data of finite element analysis. Because of the plane strain condition of the top view section, results can be only applied to the full-flow failure mechanism around the pile for the prediction of limiting pressure at the deeper length of a very long pile with full tension interface that does not allow any separation at soil-pile interfaces.

Undrained lateral capacity of rectangular piles under a general loading direction and full flow mechanism

Boonchai Ukritchon,Suraparb Keawsawasvong 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.7

New upper and lower bound solutions of undrained lateral capacity of rectangular piles under a general loading direction and fullflow mechanism were investigated by using finite element limit analysis with plane strain condition. The true collapse loads of thisproblem were generally bracketed by computed upper and lower bound solutions to within 3%. Results were summarized in the formof three dimensionless variables, including soil–pile adhesion factor, pile aspect ratio, and lateral loading direction. Predicted failuremechanisms of laterally loaded rectangular piles associated with these parameters were examined and discussed. Approximateequations of failure envelopes for rectangular piles under a general loading direction were proposed for a convenient and accurateprediction of their undrained lateral capacity in practice.

Optimal Design of Reinforced Concrete Cantilever Retaining Walls Considering the Requirement of Slope Stability

Boonchai Ukritchon,Sophea Chea,Suraparb Keawsawasvong 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.7

A Reinforced Concrete Cantilever Retaining Wall (RCCRW) is one commonly used soil retaining structure in engineering practice. Various optimization techniques to obtain the optimal design of cantilever walls have been proposed, where the three basic geotechnical constraints of overturning, sliding and bearing failures have generally been taken into consideration. However, none of these approaches have considered the geotechnical requirement of slope stability. In this paper, a novel formulation for the optimal design of RCCRWs that considers the more complete requirements of geotechnical stability of overturning, sliding, bearing and slope failures, is described. The objective function of the minimum cost of materials, geotechnical constraints of wall failures (overturning, sliding and bearing) and the structural requirements for steel reinforcements in the wall sections all followed the conventional approaches used in previous works. Using the Ordinary Method of Slices (OMS) with a circular arc failure surface (CAFS), the factor of safety against slope failure (FSOMS) for a RCCRW was implicitly derived. Constraints for ensuring that the minimum FSOMS was higher than the required factor were enforced in the formulation. Design variables were the dimensions of the wall sections, corresponding steel reinforcements and the x-y coordinate of center of the CAFS, where the latter are the additional unknowns in this novel formulation. Computational performance of the proposed optimization method is demonstrated and verified through its application to the optimal design of two examples of RCCRWs.

Predictive model for the shear strength of concrete beams reinforced with longitudinal FRP bars

Saif Alzabeebee,Moahmmed K. Dhahir,Suraparb Keawsawasvong 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.2

Corrosion of steel reinforcement is considered as the main cause of concrete structures deterioration, especially those under humid environmental conditions. Hence, fiber reinforced polymer (FRP) bars are being increasingly used as a replacement for conventional steel owing to their non-corrodible characteristics. However, predicting the shear strength of beams reinforced with FRP bars still challenging due to the lack of robust shear theory. Thus, this paper aims to develop an explicit data driven based model to predict the shear strength of FRP reinforced beams using multi-objective evolutionary polynomial regression analysis (MOGA-EPR) as data driven models learn the behavior from the input data without the need to employee a theory that aid the derivation, and thus they have an enhanced accuracy. This study also evaluates the accuracy of predictive models of shear strength of FRP reinforced concrete beams employed by different design codes by calculating and comparing the values of the mean absolute error (MAE), root mean square error (RMSE), mean (μ), standard deviation of the mean (σ), coefficient of determination (R2), and percentage of prediction within error range of ±20% (a20-index). Experimental database has been developed and employed in the model learning, validation, and accuracy examination. The statistical analysis illustrated the robustness of the developed model with MAE, RMSE, μ, σ, R2, and a20-index of 14.6, 20.8, 1.05, 0.27, 0.85, and 0.61, respectively for training data and 10.4, 14.1, 0.98, 0.25, 0.94, and 0.60, respectively for validation data. Furthermore, the developed model achieved much better predictions than the standard predictive models as it scored lower MAE, RMSE, and σ, and higher R2 and a20-index. The new model can be used in future with confidence in optimized designs as its accuracy is higher than standard predictive models.

Optimized ANNs for predicting compressive strength of high-performance concrete

Hossein Moayedi,Amirali Eghtesad,Mohammad Khajehzadeh,Suraparb Keawsawasvong,Mohammed M. Al-Amidi,Bao Le Van 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.6

Predicting the compressive strength of concrete (CSoC) is of high significance in civil engineering. The CSoC is a highly dependent and non-linear parameter that requires powerful models for its simulation. In this work, two novel optimization techniques, namely evaporation rate-based water cycle algorithm (ER-WCA) and equilibrium optimizer (EO) are employed for optimally finding the parameters of a multi-layer perceptron (MLP) neural processor. The efficiency of these techniques is examined by comparing the results of the ensembles to a conventionally trained MLP. It was observed that the ER-WCA and EO optimizers can enhance the training accuracy of the MLP by 11.18 and 3.12% (in terms of reducing the root mean square error), respectively. Also, the correlation of the testing results climbed from 78.80% to 82.59 and 80.71%. From there, it can be deduced that both ER-WCA-MLP and EO-MLP can be promising alternatives to the traditional approaches. Moreover, although the ER-WCA enjoys a larger accuracy, the EO was more efficient in terms of complexity, and consequently, time-effectiveness.

Numerical investigations of pile load distribution in pile group foundation subjected to vertical load and large moment

Ukritchon, Boonchai,Faustino, Janine Correa,Keawsawasvong, Suraparb Techno-Press 2016 Geomechanics & engineering Vol.10 No.5

This paper presents a numerical study of pile force distribution in a pile group foundation subjected to vertical load and large moment. The physical modeling of a pile foundation for a wind turbine is analyzed using 3D finite element software, PLAXIS 3D. The soil profile consists of several clay layers, which are modeled as Mohr-Coulomb material in an undrained condition. The piles in the pile group foundation are modeled as special elements called embedded pile elements. To model the problem of a pile group foundation, a small gap is created between the pile cap and underlying soil. The pile cap is modeled as a rigid plate element connected to each pile by a hinge. As a result, applied vertical load and large moment are transferred only to piles without any load sharing to underlying soil. Results of the study focus on pile load distribution for the square shape of a pile group foundation. Mathematical expression is proposed to describe pile force distribution for the cases of vertical load and large moment and purely vertical load.