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Dr. Azam Khan and Dr. Anil Patnaik
Concrete dams are thinner than embankment dams and impose more concentrated loads on the foundation and abutments. A narrow valley with sufficient rock foundation is a typical site for concrete dam, which require a solid foundation that is relatively free of faults, shears, and major changes in foundation strength. Such discontinuities can overstress the concrete by causing some areas of dams to carry more loads than other areas. The measurement of deflections and use of finite element technique can predict the stresses in the concrete dams. A computer model is underdeveloped for prediction of deflections and stresses in Concrete Dam by using finite element. At the first stage of this study, measured deflections from Burrinjuck Dam are compared with the predicted deflections by using finite element. This paper outlines the deflections measured in the dam due to temperature variations and comparison of the measured thermal deflections with those predicted from a finite element analysis.Learn more
Susantha Mediwaka, Nihal Vitharana, Badra Kamaladasa
Nalanda dam is the oldest concrete gravity dam on the Island built in the 1950s by the Ceylon Department of Irrigation. The dam was built in 9 monoliths having a dam crest length of approximately 125m and a maximum height of about 36m. The spillway consists of: (1) a low-level uncontrolled ogee-crested horse-shoe section with a crest length of 46m, and (b) a high-level broad crested weir with a crest length of 43m.Learn more
It was designed and constructed according to the then standard practices adopted throughout the world. Over the years, Nalanda dam has been showing signs of deterioration which is suspected to be Alkali-Aggregate Reaction (AAR). The dam was also shown to be deficient with respect to the stability levels required by modern standards. Under a program of dam safety improvement of the dams throughout Sri Lanka, it was decided to stabilise Nalanda dam as the first step in addressing a series of issues affecting the dam.
This paper presents the construction history, current issues, design assumptions and salient construction features in the upgrading of the dam to modern dam safety requirements.
Keywords: Concrete dams, dams Sri Lanka, concrete buttressing, upgrade, horse-shoe spillway
Randy J James, Yuyi Zhang, Gabriela Lyvers, David Schaaf
Abstract: Following the flooding disaster in New Orleans, Louisiana, due to Hurricane Katrina in August 2005, the U. S. Army Corps of Engineers (COE) initiated a comprehensive program to survey, evaluate, and rank all dams and levees in the COE’s portfolio for risk of structural failure and associated economic consequences. One objective of this program is to improve safety and risk through efficient allocation of resources for rehabilitation efforts when needed. One area of great concern is internal stresses in aging concrete monoliths causing cracking. While some cracking in concrete monoliths is a common condition having little effect on the structural performance, extended cracking can lead to instability in parts of the monolith. Mass concrete monoliths generally are not reinforced, and cold joints at lift interfaces are a potential source of weak planes. Failure of concrete monoliths due to sliding instability along internal cracked planes can have serious consequences for loss of pool. This failure mode can occur quite suddenly, and detection of such cracking or the extent of such cracking is very difficult to establish from visual inspections or even core sampling. To help in this portfolio risk assessment, analysis methodology has been developed for establishing the structural risk due to cracking in mass concrete monoliths. Finite element modelling with automated mesh generation and employing advanced concrete constitutive relations for crack initiation, propagation, and arrest, are used to establish internal cracking. Monte Carlo based probabilistic analysis methods, directly coupled to the finite element analyses, are used to evaluate uncertainties and establish the probability of failure for increasing pool elevations and seismic hazards. The objective is to provide a probability of failure for possible pool elevations under current site conditions given that there is always some possibility of a range of seismic events that could occur at any given time.
Keywords: concrete dams, cracking, structural reliability, risk, and safety