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.

The effects of Number Theory study through Youtube

( Boonchai Aree-uea ) 한국교육공학회 2014 한국교육공학회 학술대회발표자료집 Vol.2014 No.2

At present, YouTube is very important online social media because the media are diverse and meet the needs of users in all aspects, especially in education. In this research, the students who studied the Number Theory were observed. All learners were giving items before and after class studying with YouTube. Data were collected and analyzed through observations, interviews and questionnaires. The results showed that YouTube is enhancing more understanding and giving more interesting points to exchange during the class. Moreover, after class studying, YouTube could be a convenient tool for study review as well as improve their language skill.

The effect of the hole position on trapezoidal winglet vortex generators in a rectangular-duct-type solar air heater

Boonchai Lertnuwat 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.12

This study presents the effect of hole positions on a trapezoidal winglet vortex generator mounted in a rectangular-duct-type solar air heater, under the condition that the Reynolds number of the air flowing passes through the heater was between 3000 and 20000. Simulations were conducted using the realizable k-epsilon model and the wall function. The simulation results show that the hole positions affect the Nusselt number and friction factor values. The Nusselt number was highest when the hole position was located near the dead zone of the flow field. This can be evinced with a temperature distribution on an absorber plate. The effect of hole positions on the friction factor can be explained by flow velocity distributions in the x-direction of the air influx. The velocity distributions revealed that a hole in a proper position reduces the momentum flux flowing toward the winglet vortex generator, resulting in a less pressure drag.

Low-Voltage Current-mode Squarer/Rectifier Using Linear MOS Resistor

Boonchai Boonchu,Wanlop Surakampontorn 대한전자공학회 2004 ITC-CSCC :International Technical Conference on Ci Vol.2004 No.7

Large deflections of spatial variable-arc-length elastica under terminal forces

Boonchai Phungpaingam,Chainarong Athisakul,Somchai Chucheepsakul 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.32 No.4

This paper aims to study the large deflections of variable-arc-length elastica subjected to the terminal forces (e.g., axial force and torque). Based on Kirchhoff’s rod theory and with help of Euler parameters, the set of nonlinear governing differential equations which free from the effect of singularity are established together with boundary conditions. The system of nonlinear differential equations is solved by using the shooting method with high accuracy integrator, seventh-eighth order Runge-Kutta with adaptive step-size scheme. The error norm of end conditions is minimized within the prescribed tolerance (10.5). The behavior of VAL elastica is studied by two processes. One is obtained by applying slackening first. After that keeping the slackening as a constant and then the twist angle is varied in subsequent order. The other process is performed by reversing the sequence of loading in the first process. The results are interpreted by observing the load-deflection diagram and the stability properties are predicted via fold rule. From the results, there are many interesting aspects such as snap-through phenomenon, secondary bifurcation point, loop formation, equilibrium configurations and effect of variable-arc-length to behavior of elastica.

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.

Investigation of Stability and Failure Mechanism of Undercut Slopes by Three-Dimensional Finite Element Analysis

Boonchai Ukritchon,Rithy Ouch,Thirapong Pipatpongsa,Mohammad Hossein Khosravi 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.5

Slope failures along a bedding plane were critical issues and mostly happened in an open pit mining project such as the Mae MohMine, Thailand. The prediction of maximum width to maintain stable slope after an excavation process is required. This paperpresents an investigation of 3D finite element analysis for the stability and failure mechanism of undercut slopes resting on a lowinterface friction plane. In numerical models, the soil slope was modeled as volume elements with the hardening soil material. Interface elements were used at the bottom plane to simulate the low interface friction plane and at the side support to simulate fullyrough surface for the models with side supports. Stage analyses in numerical models were performed following excavation processesin physical models until failure. The effects of the side support and the slope length to increase the stability of undercut slopes wereconsidered. Failure widths, failure mechanisms, and stress distributions associated with slope angles and boundary conditions of sidesupport were discussed and compared.

Microalgae membrane photobioreactor for further removal of nitrogen and phosphorus from secondary sewage effluent

Rawiwan Boonchai,서규태 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.10

For further removal of nitrogen and phosphorus from secondary sewage effluent, two strains of microalgae, Chlorella sp. ADE4 and Chlorella vulgaris, were selected for cultivation in the membrane photobioreactor. The Chlorella sp. ADE4, isolated from wastewater illustrated higher removal efficiency of T-N and T-P, and faster algal growth than the Chlorella vulgaris in a batch experiment using treated sewage effluent. The T-N and T-P removal efficiency was 66.5% and 94.5%, respectively, within HRT of two days when the photobioreactor of Chlorella sp. ADE4 was operated in continuous mode. The effluent water quality was 6.3mg/L and 0.044mg/L for T-N and T-P. It was estimated that the algal biomass productivity was 55mg/L·d with T-N and T-P uptake rates of 6.25 and 0.483mg/L·d, respectively, in the system. Operational flux below 58 LMH was found to be effective for separation of algal cell from effluent in membrane system.

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.

Large deflections of spatial variable-arc-length elastica under terminal forces

Phungpaingam, Boonchai,Athisakul, Chainarong,Chucheepsakul, Somchai Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.32 No.4

This paper aims to study the large deflections of variable-arc-length elastica subjected to the terminal forces (e.g., axial force and torque). Based on Kirchhoff's rod theory and with help of Euler parameters, the set of nonlinear governing differential equations which free from the effect of singularity are established together with boundary conditions. The system of nonlinear differential equations is solved by using the shooting method with high accuracy integrator, seventh-eighth order Runge-Kutta with adaptive step-size scheme. The error norm of end conditions is minimized within the prescribed tolerance ($10^{-5}$). The behavior of VAL elastica is studied by two processes. One is obtained by applying slackening first. After that keeping the slackening as a constant and then the twist angle is varied in subsequent order. The other process is performed by reversing the sequence of loading in the first process. The results are interpreted by observing the load-deflection diagram and the stability properties are predicted via fold rule. From the results, there are many interesting aspects such as snap-through phenomenon, secondary bifurcation point, loop formation, equilibrium configurations and effect of variable-arc-length to behavior of elastica.