Probabilistic Analysis of the External Stability of MSE Structures Using Monte Carlo Simulations (original) (raw)
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Canadian Geotechnical Journal, 2018
This paper demonstrates reliability-based design for tensile rupture and pullout limit states for mechanically stabilized earth (MSE) walls constructed with geosynthetic (geogrid) reinforcement. The general approach considers the accuracy of the load and resistance models that appear in each limit state equation plus uncertainty due to the confidence (level of understanding) of the designer at the time of design. The reliability index is computed using a closed-form solution that is easily implemented in a spreadsheet. The general approach provides a quantitative link between nominal factor of safety, which is familiar in allowable stress design practice, and reliability index used in modern civil engineering reliability-based design practice. A well-documented MSE wall case study is used to demonstrate the general approach and to compare margins of safety using different load and resistance model combinations. A practical outcome from the case study example is the observation that ...
Ultimate Limit State Reliability-Based Optimization of MSE Wall Considering External Stability
Sustainability
We present reliability-based optimization (RBO) of the Mechanically Stability Earth (MSE) walls, using constrained optimization, considering the external stability, under ultimate limit state conditions of sliding, eccentricity, and bearing capacity. The design is optimized for a target reliability index of 3 that corresponds to an approximate failure probability of 1 in 1000. Reliability index is calculated by the first-order reliability method (FORM). The MSE wall, founded on cohesionless soil, with horizontal backfill and uniform live traffic surcharge, is studied. The RBO results are reported for the height of MSE wall ranging from 1.5 m to 20 m. For target reliability index of 3, the optimized length to height ratio, Lopt/H, of the MSE wall is greater than 0.7 (the minimum length to height ratio requirement of AASHTO) for H≤4.5 m, and then it decreases below the minimum required value of 0.7 for H>4.5 m. The RBO approach presented in this study will help practitioners to ach...
STRUCTURAL RELIABILITY ASSESSMENT WITH STOCHASTIC PARAMETERS
The performance of a structure [23] is assessed by its safety [1], serviceability [1] and economy [1]. Since we do not know the exact details of loads [4] acting on a structure at any time, there is always some uncertainty about the total loads on structure. Thus random variables (means stochastic variable) of loads and other parameters are the main criteria of design variables [18]. They vary with space and time. The input variables is never certain and complete. The safety factor provided in the existing codes and standers primarily based on practice, judgment and experience, may not be adequate and economical. Using the techniques presented earlier, we can design or analyze individual members in the contest of structural reliability [2][3][22][24]. However we are not examined how the system performs [23] or how to calculate the reliability of the structure as a whole.
RELIABILITY ANALYSIS OF STRUCTURES USING STOCHASTIC FINITE ELEMENT METHOD
Author of the monograph, Juraj Králik, has been working at the Department of Structural Mechanics as assistant since September 1, 1976 and as associate professor since January 18, 1988. During the years 2000 - 2006 he was the head of Department. He holds lectures in two study programs: Engineering Structures and Transport Structures; and Civil Engineering and Architecture. He teaches the following subjects: Mechanics of Structures and Materials, Seismic Enginering and Computer Design, Risk Engineering, Safety and Reliability of Buildings. His regular students and doctoral students have won several prizes in the student research competitions at the Faculty. He has been implementing advanced computer programs and methods in teaching and research at the Department, being himself an author of more than 100 programs of the static and dynamic applications. He is guarantor of using the licensed software systems ANSYS and MathCAD at the Department and Faculty, too. As the co-guarantor, he has established the doctoral study program “Applied Mechanics”. During the years 2000-2006, in cooperation with the Slovak Chamber of the Civil Engineers he was the supervisor of seven volumes of the postgraduate study course „Aeroelasticity and Seismicity“, and the chairman of seven volumes of the International Conference „New Trends in the Statics and Dynamics of Buildings“. His results were presented in more than 300 papers in conference proceedings and journals, 10 papers are indexed in prestigious database „Web of Science“. Three papers were published in the currented international journals „Mathematics and Computers in Simulation” (1999), „Control and Cybernetics” (2006) and “Engineering Structures” (2009). 17 research and grant projects were managed by him. His works were cited in more than 200 papers in scientific and special publications. As the reputable scientific personality he was the member of the scientific committees of several international conferences abroad. In the year 1989 he was appointed an expert of the safety and reliability of nuclear power plants in Slovakia. He cooperated at the analysis of the seismic resistance of the nuclear power plant buildings and their safety under impact of explosion, missile and container drop. More than 100 expertises were realized by him in the field of the safety and reliability of the NPP buildings in Slovakia. Some of his research and expert works were awarded by significant institutions. The most significant is the honorable award of the Czech Engineering Academy for the paper „Probability Analysis of Reinforced Concrete Structure Failure of Nuclear Power Plants Due to Loss of Coolant Accident “ published in the journal „ENGINEERING MECHANICS“ in 2006.
Reliability based risk index for the design of reinforced earth structures
Geotechnical and Geological Engineering, 2003
The design methods currently used for earth reinforcement are mostly based on deterministic properties of both the soil and the construction materials used. Nowadays, however, the general trend is designing at a specific degree of reliability. This is even more true where the raw data such as soil properties exhibit significant variation. Deterministic solutions, in this case, may not suffice. Therefore, this paper will attempt to use probabilistic formulations thereby modifying the existing design procedure of reinforced earth retaining walls to account for uncertainties and variabilities. Through a first order Taylor's series expansion about the mean, the mean and variance of the strip reinforcing components, namely width and length, are derived in terms of the variations in the soil properties. Design charts that enable estimation of both mean and variance are developed to avoid extensive partial differentiation involved in the computations. Using appropriate probability distributions along with the mean and variance, the final design outputs are determined for a selected failure probability by introducing what is refered to as 'risk index'. The results indicate that the risk index increases with an increase in the coefficient of variations and a decrease in failure probability. Furthermore, it is shown that in some cases, depending on the variabilities of the soil properties, the classical design technique produced a relatively high failure probability.