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Abstract
Precast concrete elements are widely used in the construction industry as they provide a number of advantages over the conventional insitu cast concrete structures. Joints cast on the construction site are needed to connect the precast elements, which poses several challenges. Moreover, the current practice is to design the joints as the weakest part of the structure, which makes analysis of the ultimate limit state behaviour by general purpose software difficult and inaccurate.
Manual methods of analysis based on limit analysis have been used for several decades. The methods provide excellent tools for engineers, however, the results are very dependent on the skill and intuition of the design engineer. Increasingly complex structures and the extensive use of computeraided design on other aspects of civil engineering push for more accurate and efficient tools for the analysis of the ultimate limit state behaviour. This thesis introduces a framework based on finite element limit analysis, a numerical method based on the same extremum principles as the manual limit analysis. The framework allows for efficient analysis and design in a rigorous manner by use of mathematical optimisation.
The scope is to be able to model entire precast concrete structures while accounting for the local behaviour of the joints. The insitu cast joints are crucial to the capacity of precast concrete structures, however, the behaviour of joints is in practice assessed by simple, empirical design formulas. A detailed study of insitu cast joints in twodimensions is conducted using finite element limit analysis, and the findings are used in the development of a twodimensional multiscale joint finite element, which can represent the complex behaviour of the joints to a satisfactory degree.
Analysis of threedimensional structures is rather difficult, especially by manual methods, however, considering threedimensional nature of structures will generally increase the capacity. The twodimensional joint element is therefore generalised to threedimensions in order to be able to account for the influence of the joints.
The strength and efficiency of the presented framework are demonstrated by two real size examples, a twodimensional precast shear wall and a threedimensional precast concrete stairwell. The analysis shows that the framework is capable of modelling complex precast concrete structures efficiently. Moreover, the influence and local behaviour of the joints are accounted for in the global model.
The results of the two examples demonstrate the potential of a framework based on finite element limit analysis for practical design. The use of mathematical optimisation ensures an optimised design, and the optimisation problems are solved efficiently using stateoftheart solvers. It is concluded that the framework and developed joint models have the potential to enable efficient design of precast concrete structures in the near future.
Manual methods of analysis based on limit analysis have been used for several decades. The methods provide excellent tools for engineers, however, the results are very dependent on the skill and intuition of the design engineer. Increasingly complex structures and the extensive use of computeraided design on other aspects of civil engineering push for more accurate and efficient tools for the analysis of the ultimate limit state behaviour. This thesis introduces a framework based on finite element limit analysis, a numerical method based on the same extremum principles as the manual limit analysis. The framework allows for efficient analysis and design in a rigorous manner by use of mathematical optimisation.
The scope is to be able to model entire precast concrete structures while accounting for the local behaviour of the joints. The insitu cast joints are crucial to the capacity of precast concrete structures, however, the behaviour of joints is in practice assessed by simple, empirical design formulas. A detailed study of insitu cast joints in twodimensions is conducted using finite element limit analysis, and the findings are used in the development of a twodimensional multiscale joint finite element, which can represent the complex behaviour of the joints to a satisfactory degree.
Analysis of threedimensional structures is rather difficult, especially by manual methods, however, considering threedimensional nature of structures will generally increase the capacity. The twodimensional joint element is therefore generalised to threedimensions in order to be able to account for the influence of the joints.
The strength and efficiency of the presented framework are demonstrated by two real size examples, a twodimensional precast shear wall and a threedimensional precast concrete stairwell. The analysis shows that the framework is capable of modelling complex precast concrete structures efficiently. Moreover, the influence and local behaviour of the joints are accounted for in the global model.
The results of the two examples demonstrate the potential of a framework based on finite element limit analysis for practical design. The use of mathematical optimisation ensures an optimised design, and the optimisation problems are solved efficiently using stateoftheart solvers. It is concluded that the framework and developed joint models have the potential to enable efficient design of precast concrete structures in the near future.
Original language  English 

Publisher  Technical University of Denmark, Department of Civil Engineering 

Number of pages  250 
ISBN (Print)  9788778774583 
Publication status  Published  2017 
Series  B Y G D T U. Rapport 

Number  R383 
ISSN  16012917 
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Projects
 1 Finished

Numerisk Modellering af betonelementkonstruktioners idealplastiske bæreevne
Herfelt, M. A., Poulsen, P. N., Hoang, L. C., Jensen, J. F., Stang, H., Andreasen, B. S. & Bleyer, J.
15/12/2013 → 29/09/2017
Project: PhD