טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentBenyamin Rana
SubjectShear Design of Reinforced Concrete Elements with Circular
Cross-Sections
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Avraham Dancygier


Abstract

It is commonly known that diagonal tension stress develop in RC members subjected to shear load. Therefore, proper design of RC members with wide rectangular cross-sections requires that stirrups will be given also in the cross-section’s center. This is neither required nor practiced in cross-sections of members with circular cross-sections with large diameters. This study focuses on the analysis of circular RC members subjected to shear. It especially deals with the detailing of transverse reinforcement in large diameter circular cross-sections.

The analysis is theoretical.  Numerical analyses were performed with the finite element program “ANSYS”, where in the first stage numerical simulations were done of two experiments performed by Khalifa and Collins, whose experimental research is considered as one of the important works on circular RC members subjected to shear.

The above analyses were followed by a numerical, finite element analysis of a test case of an RC member with a circular cross-section with a relatively large, 2-meter diameter.  This example was analyzed with different detailing of the transverse reinforcement.

Three different cases were examined: circular ties, ties combined with stirrups that were given at the center and stirrups that were given only at the center.  Study of the results of the non-linear finite element calculations of these cases included their load-displacement curves, their strain distributions and the angle of inclination of their shear cracks. In addition, the maximum shear loads that were obtained from the finite element analyses were compared with the calculated shear strength predictions of several models published in the literature.

In order to examine the validity of the above results that were obtained for the different detailing of the shear reinforcement it was felt necessary to carry out similar simulations of an RC beam with a wide rectangular cross-section.

It should be noted that the non-linear simulation of reinforced concrete in the finite element program ANSYS yielded numerical difficulties, which were caused by the divergence of the calculations due to large deformations or an unstable behavior of the nonlinear element. Therefore, a further conclusion of this work is that this version of the finite element program is not recommended for nonlinear simulation of reinforced concrete.  Consequently, the detailing problem of the transverse reinforcement of circular reinforced concrete members should be further examined by analytical-numerical calculations, followed by experimental study.