Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Quantification of Different Sources of Over-Strength in Seismic Design of a Reinforced Concrete Tall Building
Get PDFAn over-strength factor in seismic design plays an important role in computing actual forces in a structural member designed to remain elastic. However, sources contributing to this over-strength have not yet been systematically quantified for tall buildings. This paper aims to investigate the contribution from different sources of the over-strength factor in a reinforced concrete (RC) tall building. The contribution of slab-column gravity load framing to the lateral load capacity of the building is also investigated. A 39-story RC tall building subjected to earthquake ground motions in Bangkok was first designed according to the current building codes. Then, pushover analysis was conducted to compute the capacity curves of the building with three different specified strengths: design strength (with f factor), nominal strength (without f factor), and actual strength (with material over-strength). It was found that slab-column framing action contributes about 60% of the total lateral load capacity of the building. The building has an overall lateral over-strength factor of 3.36 to 3.71. The over-strength factor arising from the design is 2.12 to 2.42 in which the contributions from strength reduction factor, material over-strength, and other sources involving the design requirements are about 1.10, 1.17, and 1.77, respectively. The over-strength factor arising from the redundancy due to the redistribution of internal forces is about 1.55 and the contribution from the steel strain hardening to the over-strength factor is relatively small
Material Cost Prediction for Jewelry Production Using Deep Learning Technique
Get PDFProduction cost management is a key factor to increase industrial competitiveness. The precious metals and the gemstones comprise 65% of the jewelry material cost. Managing raw material cost is a challenging task especially when the price highly fluctuates. In this article, deep learning models were proposed to predict the prices of main raw materials of jewelry which are silver, gold, and diamond. These models are designed for Thai jewelry manufactures which are mostly small businesses. Therefore, our models only consider historical price data. This is because small businesses usually do not have access to other relevant data, i.e. oil prices and other economic data.
The proposed precious metal price model can provide prediction with RMSE of 0.00765 which is comparable to other models in literature while requires less data and offers a simpler model. Also, the proposed diamond price model can provide RMSE of 0.0181 which is 42.41% improvement from the model normally used by jewelry manufacturers.
In addition to the raw material price prediction model, a quantization method of diamond 4C grade is proposed and validated statistically and visually. This quantization method could be used in a diamond analysis
Modified Fuzzy FMEA Application in the Reduction of Defective Poultry Products
Get PDFFailure mode and effects analysis (FMEA) consists of the famous qualitative management methods used for improvements in management processes. This paper aims to determine the factors of defective products in the processing of poultry products in the industry. The causes of problems have been analyzed by systematic brainstorming of specialist consensus in the evaluation of problems to achieve unanimity on the violence level. The FMEA method uses the risk priority number (RPN), which indicates the priorities of risk problems and can evaluate three components: severity, occurrence and detection. Sometimes, this risk assessment leads to the wrong priorities. Therefore, we propose fuzzy FMEA methods for priority ranking of RPN and efficiently reducing poultry product defects, which are established based on fuzzy systems followed by comparison with conventional FMEA. The results indicate that the fuzzy FMEA method can efficiently and feasibly reduce poultry product defects
Effects of Water Table Level on Slope Stability and Construction Cost of Highway Embankment
Get PDFHighway embankments stability during its service period represents an important factor for the safety of highway users and vehicles. Consequently, the cost of construction of these embankments should be adequate to maintain the safety and durability during this period through proper estimation of the loading on asphalt pavement, slope stability, horizontal and vertical deformation, etc. Slope stability of the embankment mainly depends on the shear strength of the soil layers materials; this shear strength is affected by the water table level through the contribution of the capillary water. Negative pore water pressure above the water table level evolves matric suction in the unsaturated zone above water table; this matric suction increases the shear strength of the soil depending on the soil type, void ratio, etc. This paper studies the slope stability of highway embankment using finite element method analysis to show the effect of the presence of water table and the contribution of the matric suction. A trial slope is shown to have same factor of safety with reduced cross section due to increasing the shear strength hence, reducing the cross-sectional cost is determined
Solving Many-Objective Car Sequencing Problems on Two-Sided Assembly Lines Using an Adaptive Differential Evolutionary Algorithm
Get PDFThe car sequencing problem (CSP) is addressed in this paper. The original environment of the CSP is modified to reflect real practices in the automotive industry by replacing the use of single-sided straight assembly lines with two-sided assembly lines. As a result, the problem becomes more complex caused by many additional constraints to be considered. Six objectives (i.e. many objectives) are optimised simultaneously including minimising the number of colour changes, minimising utility work, minimising total idle time, minimising the total number of ratio constraint violations and minimising total production rate variation. The algorithm namely adaptive multi-objective evolutionary algorithm based on decomposition hybridised with differential evolution algorithm (AMOEA/D-DE) is developed to tackle this problem. The performances in Pareto sense of AMOEA/D-DE are compared with COIN-E, MODE, MODE/D and MOEA/D. The results indicate that AMOEA/D-DE outperforms the others in terms of convergence-related metrics
Influence of Bottom Ashes with Different Water Retainabilities on Properties of Expansive Mortars and Expansive Concretes
Get PDFThis study investigates the influence of bottom ashes with different water retainabilities as an internal curing material on the performances of mixtures containing an expansive additive and fly ash. Two series of experiments were conducted: mortar containing expansive agent (expansive mortar) with a controlled w/b ratio and concrete containing expansive agent (expansive concrete) with a controlled initial slump. Test results indicate that workability of expansive mortar is improved due to retained water of bottom ash. Compressive strength of expansive mortar with bottom ash decreases. Total shrinkage of the expansive mortars, with a constant w/b, increases with the use of bottom ashes that have high water retainability in the condition of 7 days of water curing and then air curing. However, by using bottom ashes, compressive strength increases when the slump of the expansive concrete is controlled due to decrease of w/b ratio. The internal curing ability of bottom ashes leads to enhanced expansion of expansive mortars with sealed curing and expansive concretes with moist curing, reducing total shrinkage of expansive mortars with air curing. It was found by DTG analysis that expansive concretes with higher expansion containing bottom ash with higher water retainability had a higher amount of ettringite
Analysis of Tropospheric Nitrogen Dioxide Using Satellite and Ground Based Data over Northern Thailand
Get PDFTropospheric NO2 columns over northern Thailand were analyzed using satellite products of the SCIMACHY, OMI, GOME-2A, and GOME-2B sensors for the 14-year period 2003–2016. The comparative results of the four pairs of different satellite datasets within overlapped years showed that they were well correlated with correlation coefficients (r) ranging from 0.82 to 0.88. The r-values improved to 0.85–0.90 when the analysis was considered only during the dry period (October to April). Ground in situ measurements of NO2 concentrations were also obtained for comparative analysis with the satellite NO2 columns. The results revealed relatively good agreement between these two parameters for a seasonal pattern. High levels of NO2 were detected by both satellite and ground monitoring during January–April with the maximum levels in March. Moreover, during this period, most satellite and ground datasets recorded greater levels of NO2 in the afternoon corresponding with the number of fire hotspots collected from the MODIS-Terra and -Aqua satellites. Satellite and ground measurements show slightly increasing annual trends of NO2 levels for 2010–2016 with values of 8.40 and 1.18 %, respectively, over the 6-year period
Modeling of Precast Concrete Load-Bearing Walls Exposed to Fire
Get PDFThe performance of precast concrete load-bearing walls exposed to fire is investigated using 3-D thermal and structural models. The thermal model is validated by comparing the predicted temperatures with results from the fire tests carried out in the present study, previous experimental studies, and Eurocode 2. The structural model is validated by comparing the predicted displacements and crack patterns with results from the fire tests carried out in the present study. It is found that the results obtained from the thermal model and the structural model are in line with the experimental data and Eurocode 2 results. The validated 3-D model of precast concrete load-bearing walls is used to study the effect of load level, slenderness ratio and boundary conditions on the fire performance of the walls. The results show that the fire resistance rating of load-bearing walls decreases with increasing load level and slenderness ratio, while the fire resistance rating of the walls increases when rotational restraints are imposed at the ends of the walls. Finally, equations are presented for estimating the fire resistance rating of the walls with different support conditions
Numerical Simulation of Currents and Volume Transport in the Malacca Strait and Part of South China Sea
Get PDFThe aim of this work is to determine the hydrodynamics of the Malacca Strait (MS) and the southern part of the South China Sea (SCS). The study uses the two-dimensional numerical model with a finite-difference method. The results show that the sea levels in MS and part of SCS are reversed and consistent with assimilation data that derived from Simple Ocean Data Assimilation (SODA). Sea level in northern MS is lower than that in the southern part during January and July. However, the interval of sea level elevation in both January and July appears differently. It is steeper in January than in July. Therefore, the currents and transports during January are stronger than those during July. However, in general, the direction of currents and volume transport of MS flow to the Andaman Sea both in January and July. In SCS, the pattern is relatively the same as in MS; that is, the currents during January are stronger than those during July
Pre-project Planning Process Study of Green Building Construction Projects in Thailand
Get PDFProject effectiveness is a challenge in sustainable building construction projects. Lack of experience, knowledge, and skills in sustainable projects have been highlighted as the main barriers to using sophisticated and innovative techniques. Based on the literature, the pre-project planning effort directly influences a project’s success. Nevertheless, the differences in planning efforts for green projects have not been fully determined, especially in Thailand where sustainability just has been only recently considered in this context. This study investigated the status of pre-project planning for green building construction projects located in Thailand to promote sustainable construction. The analyses were performed based on two main objectives: (1) to compare the overall planning effort and (2) to address dissimilar planning factors between green and conventional projects. The concept of a project definition rating index (PDRI) was applied to evaluate the level of pre-project planning effort in 40 sample projects. An independent t-test was used for data analysis. The findings from this study indicated the importance of pre-project planning for green building construction that contributes all stakeholders to understand which aspects were differently implemented during the planning process in green compared to conventional programs