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Concrete Dams and Alkali-Aggregate Reaction

#G-1153


Computer Program for Strength Analysis of Alkali-Aggregate Reaction-Affected Concrete Dams

Tech Area / Field

  • INF-SOF/Software/Information and Communications
  • MAT-OTH/Other/Materials
  • PHY-STM/Structural Mechanics/Physics

Status
8 Project completed

Registration date
26.04.2004

Completion date
11.07.2008

Senior Project Manager
Lapidus O V

Leading Institute
Tbilisi Architectural and Civil Engineering Institute, Georgia, Tbilisi

Collaborators

  • Centro Elettrotecnico Sperimentale Italiano, Italy, Milan\nLoughborough University, UK, Loughborough

Project summary

The State of the Art in the Field of Research.

More than 20000 high concrete dams of various types currently operate around the world. They are affected not only by external, but internal forces as well. The latter is derived by reason of concrete nature as an artificial material. Among these is Alkali-Aggregate Reaction (AAR). AAR is a chemical reaction within hardened concrete, which causes it to expand over time. The expansion causes cracking in the cement paste and aggregates, which adversely affects the mechanical properties of the material. As the in-situ observations show, this phenomenon negatively affects the dams’ reliability and may cause their damage, partial or total failure with catastrophic human and material losses. This phenomenon became the subject of engineers’ study for the recent 10-15 years since a numerous number of alkali-aggregate reaction-affected dams were visualized in the U.S.A., South Africa, Portugal, Spain, Mozambique and other countries. A number of works are available in the literature in which attempts are made to model AAR phenomenon mathematically. Since the AAR causes change of concrete volume (concrete expansion), some works are based upon the model of equivalent thermal analysis (H. Elges, C.H. Yeh, et al.). The significant achievements on the basis of a stress-dependent concrete growth model are made by D. D. Curtis, R.G. Charlwood, G.A. Thomson, et al. In spite of this, the problem of stress-strain state of AAR-affected concrete dams is only at the initial stage of study. No direct numerical modeling of the AAR phenomenon is available. We see the further progress in the following two ways: 1. Use of different, more efficient mathematical model than the present ones, and 2. Direct numerical modeling of alkali-aggregate reaction phenomenon in the framework of finite element or other numerical methods.

The Project's Purposes:

1. A new approach to take into account the AAR in concrete on the stress-strain state of the dams. It is based upon the mathematical model similar to that, which successfully describes the creep process in concrete;


2. A computer program, developed on the basis of the Finite element method for the strength analysis of AAR-affected concrete dams, with a view to specifying their operational life.

The Impact of the Project Results on the Progress in the Field of Research:

1. Risk of damage or failure of AAR-affected concrete dams will be reduced, i.e. probability of precise prediction of their damage or failure will be raised;


2. Solution of the fundamental problem of operation of the most important hydraulic structures - dams: safety and reliability, will be increased, i.e. probability of disastrous ecological and economical consequences will be reduced.

Competence of the Project Team.

The core of the team is composed of the highly qualified researchers with successful scientific background, who are well respected among their colleagues. They have already developed a few effective approaches to the analyses of some structures, including various types of concrete dams. Having the experience of the joint research activity, they enthusiastically consolidated around the proposed project on behalf of the Tbilisi Architectural and Civil Engineering Institute.

Expected Results and their Applications.

1. A New Approach to the analysis of existing AAR-affected concrete dams with a view to specifying their operational life;


2. Computer Program, implementing the developed approach.

Scientific significance of the results consists in new approach to the analysis of the stress-strain state of AAR-affected concrete dams.

Commercial value consists in implementation of a new approach in the form of users friendly computer program. It may obtain its users in dam engineering industry, universities and R&D organizations.

Meeting ISTC Goals and Objectives.

The project fully meets ISTC goals, in particular:

· Field of research is purely peaceful. Hence, weapons scientists get an opportunity to switch over to the peaceful scientific activity during the project implementation. After the successful completion of the project they get a feasible chance to continue working both in peaceful research and implementation fields;


· The problem raised in the project belongs to the most urgent in the field of dam safety management. Many scientific centers around the world are involved in the solution of this problem. This fact directly implies integration of weapons scientists into the international scientific community. In this process the role of collaborators will be appreciable;
· The project result will essentially reduce the risk of damage or failure of AAR-affected concrete dams. Thus, the project makes a contribution to the field of environmental protection;
· The project result will speed up the solution of complete safety problem of the most important hydraulic structures in the world. Thereby, the contribution will be made to the international technical problem;
· The project result - a computer program will be a product, which will have its consumer; i.e. it will be a product of marked-based activity.

Scope of Activities.

Generally, the research will be carried out in the field of Structural Mechanics, specifically, in the fields of Solid Mechanics with the elements of Soil Mechanics. The Finite Element Method will be a calculation tool.


Role of Foreign Collaborators.

· Exchange information in the course of project implementation;
· Review the project plans and results;
· Help host project personnel to visit to the collaborator’s organizations;
· Assist in evaluating results from the computer analyses of the actual AAR-affected dam at the final, third stage of the project implementation (see “Technical Approach and Methodology” below).

Technical Approach and Methodology

Technical approach to the project implementation consists in a permanent research and parallel computer programming processes.

Methodologically, the work will be done in compliance with the sequence of its pision into three stages:

1. Research, when the adequate theoretical models and algorithms are developed;


2. Computer implementation of developed theoretical algorithms;

Implementation of the computer program for the calculation of the actual "dam-foundation " system.


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