Design and analysis of two-dimensional structural concrete with strut-tie model
Abstract
The performance and strength of five simply supported reinforced concrete beams with different stirrup detailing and one pretensioned concrete beam are evaluated using the strut-tie model approach with the aid of the interactive computer graphics program. In addition, two design examples, squat shear walls subjected to large lateral forces, are presented to demonstrate that the strut-tie model approach with graphics capabilities can provide simple solutions for a large number of design situations dealing with structural concretes. The strut-tie model approach as a conceptual model is found instrumental in understanding the function of both concrete and steel reinforcement. It not only provides a visual representation of the essential aspects of structural loading carrying mechanisms, but also provides useful tools for structural detailing and dimensioning. The interactive computer graphics program with nonlinear analysis capability, which implements the strut-tie model approach for the analysis and design of structural concrete, is developed. The graphics program consists of three parts. The first part is considered as a pre- and post-processor to a nonlinear finite element analysis program for solving plane solid problems. The second part enables the user to develop strut-tie models interactively based on the results of the first part. This part is also considered as a pre- and post-processor to a nonlinear finite element program for solving plane truss problems. The third part is a design routine for dimensioning and detailing the components (struts, ties and nodes) of the developed strut-tie model using the resulting forces from the second part. The use of interactive computer graphics program incorporated with finite element nonlinear analysis programs is shown to be efficient in the development, analysis and detailing of strut-tie models for design, and analysis of reinforced and prestressed concrete members including disturbed regions. For a more accurate prediction of nonlinear structural behavior, a finite element nonlinear formulation which is implemented in the interactive computer graphics program is developed based on the consistent continuum mechanics approach. In the formulation, the updated material reference frame is employed so that the true stress-strain test can be directly applied to correctly characterize properties of materials which undergo nonlinear deformations. Since the compressive strength of concrete is affected by several factors such as disturbance caused by cracks and reinforcement, confinement and multiaxial state of stress, it is not possible to have all the concrete struts reach simultaneously a unique peak value of compressive strength. In this study, a general and consistent approach for determining the effective strengths of concrete struts is developed by implementing the principal stress ratios obtained from the finite element analysis for the corresponding strut and nodal regions.
Degree
Ph.D.
Advisors
Ramirez, Purdue University.
Subject Area
Civil engineering
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