Full Paper Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012
Using Steel Bars in Optimum Design of Reinforced Earth Walls by Genetic Algorithm E. Eshtehardian1, R.Taheriattar2, S.Mohammadi3, M.Farzanehrafat4 1
Project and Construction Management Dept., Tarbiat Modares University, Tehran, Iran Eshtehardian@iust.ac.ir 2 Civil Engineering Dept., Iran University of Science and Technology, Tehran, Iran Rezataheria@gmail.com 3 Civil Engineering Dept., Iran University of Science and Technology, Tehran, Iran Sina.moham@gmail.com 4 Civil Engineering Dept., Iran University of Science and Technology, Tehran, Iran Morvarid.fr@gmail.com
Abstract - Mechanically Stabilized Earth Wall (MSEW) is a kind of retaining walls promoted for its simplicity and appropriate flexibility. The most important problem in using this type of retaining walls is high operational volume. Employing new optimization methods in such circumstances play an important role for reducing costs and saving resources. So, the application of optimization techniques in large construction projects such as reinforced earth walls subjected to static forces sounds rational and useful. In this paper, Genetic Algorithm (GA) is used to achieve optimized design of reinforced earth walls. The findings demonstrated that using GA makes the construction of MSE walls cost-effective and provides safety and strength as well. Nevertheless, applying steel bars as a construction method did not contribute to cost deduction.
Prevalence of using reinforced earth walls caused to employ new methods for optimization, aiming to reduce the costs of constructing these walls. Smith et al. revealed the need for more collaborative and systematic approach to design and construction of MSE wall systems [18]. Basudhar et al. succeeded to make more than seven percent reduction in costs using optimization in design of earth walls reinforced with geotextiles [11]. Ghiassian et al. used limit equilibrium method for designing mechanically stabilized earth walls with horizontal metal strips [2]. Genetic algorithm optimization was used to find best layout of reinforcements based on the amount of consumed metal and reinforced wall fill. Integrating the simulation and optimization approaches in optimized design of MSEWs was adopted for the first time in its kind. According to the example presented in their research, costs were reduced up to 15% by using the proposed method [2]. Ghiassian et al. used PSO method to represent a model for optimization of reinforced earth walls design, which showed better results in comparison to linear programming method and costs reduced by 16 percent [1]. Despite several studies conducted to optimize MSEW design, there has not been an effort for optimum design of reinforced earth walls with steel bars in static conditions. So, it seems justifiable and necessary to conduct a scrutiny and concentrate on use of steel bars in optimum design of reinforced earth walls in order to save a great amount of financial and natural resources. This paper examined the application of steel bars in optimum design of reinforced earth walls subjected to static forces using Genetic Algorithm.
Key Words: Optimization; Genetic Algorithm; Reinforced Earth Wall; Steel Bars; Design; Construction
I. INTRODUCTION The reinforced earth wall as one of the most applicable flexible retaining walls promoted for its simplicity, appropriateness and low execution costs [1, 2]. The term “reinforced earth� points to the soil reinforced with elements such as steel bars, metal strips or geo-textiles. Reinforcements lead to increase tension and shear strength due to the friction between soil and reinforcing materials along contacting surfaces.Broad studies have been conducted about the application and design of reinforced earth walls [3, 4, 5, 6, 7, 8, 9, and 13]. Kim and Salgado showed the advantages of LRFD over working stress design (WSD) and evaluates load and resistance factors for external stability checks of MSE walls [14]. In 2012, they did the same for MSE wall sliding and overturning checks [15]. Bathurst et al. reported results of LRFD reliability based calibration of resistance factors for pullout and yield limit states of steel grid and ribbed strip reinforced soil walls [16]. SajnaSayed et al. investigated the effects of inputs uncertainty such as soil and reinforcing properties and their interactions on value of minimum reliability index (Parametric sensitivity analysis) [10]. Abdelouhab et al. numerically analyzed the behavior of MSEWs with different types of strips [17]. Š 2012 ACEE DOI: 02.ADCS.2012.1. 504
II. STABILITY ANALYSIS In this paper, it was assumed that the MSE wall has a horizontal backfill and reinforcing bars with constant length and uniform distribution.The external and internal stabilities are guaranteed by proper dimensions of structure and reinforcements. External failure mechanism consists of sliding, eccentricity, and bearing capacity and internal failure mechanism includes tension failure and pull-out failure.
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