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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 86
Edited by: B.H.V. Topping
Paper 23

Reliability Assessment of Theoretical Profiles in Concrete Gravity Dams

R.C. Silva and L.J. Pedroso

Department of Civil Engineering, University of Brasília, Brazil

Full Bibliographic Reference for this paper
R.C. Silva, L.J. Pedroso, "Reliability Assessment of Theoretical Profiles in Concrete Gravity Dams", in B.H.V. Topping, (Editor), "Proceedings of the Eleventh International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 23, 2007. doi:10.4203/ccp.86.23
Keywords: concrete, safety, dam, profiles, sliding, overturning.

Generally an increase in dam safety involves an increase in cost. However, for dam project usually equilibrium must be found between security and economy. On the other hand, if human life can be in risk by a structure failure safety requirements are higher and cost can increase [1].

Structure assessment can be defined as a set of activities used to determine the safety of an existing structure. In recent years, the use of probabilistic approaches to execute structure assessment provides a sophisticated manner to evaluate the safety of a structure as shown in references [2,3,4]. In fact, the variables involved in an assessment process are not perfectly known once they have inherent uncertainties and variabilities related to dimensions, material properties, etc. In this manner, these variables should be randomly described [4,5].

Thus, this paper presents a reliability assessment of theoretical profiles of concrete gravity dams (trapezium and triangle shapes) by using reliability theory. To carry out this analysis two hypotheses are considered. First, the dam base width is modified according to the following relations: 0.4H; 0.5H; 0.6H; 0.7H; 0.8H and 0.9H, where H represents the height of the dam (86.865m). Second the water levels in the upstream reservoir vary. The levels are 10m to 80m, considering an increment of 10m.

Different loads act upon the profiles. Dead load, hydrostatic pressure, uplift, silt pressure and seismic forces treated by the pseudo-static method (Westergaard Method) [6]. This simplified response spectrum method takes into account inertial forces of the concrete dam and hydrodynamic pressures as an added mass.

Two safety margins are verified concerning sliding and overturning safety factors. Performance analysis is carried out in the interface joint (dam/foundation). As a result, behaviour of theoretical profiles is discussed through the analysis of the reliability curves.

CIGB-ICOLD, International Comission of Large Dams- Dam Safety Guidelines, Bulletin 59, Paris, 1987.
BD 79, "Level 4 and level 5 Methods of Assessment for Bridges", Highway Agency BD 79, September, 2001.
P. Thoft-Christensen, Y. Murotsu, "Application of Structural Systems Reliability Theory", Springer-Verlag & Berlin Heidelberg, New York, Tokyo, 1985.
J. Schneider, "Introduction to Safety and Reliability of Structures", IABSE, AIPC & IVBH, 1997.
R.E. Melchers, "Structural Reliability Analysis and Prediction", Wiley, 1999.
H.M. Westergaard, "Water Pressure on Dams During Earthquakes", Transactions, ASCE, Vol.98, Paper No. 1835, pp. 418-433,1933.

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