Alkali silica reaction (ASR) and delayed ettringite formation (DEF) are two causes of
concrete deterioration. Both mechanisms cause expansion of concrete and thus extensive
cracking. Most previous research on ASR and DEF focused on understanding the
material science of the mechanisms. This dissertation adds to the smaller body of
knowledge about ASR/DEF’s effect on the structural behavior of reinforced concrete
columns. It compares the structural performance of ASR/DEF affected concrete columns
to mechanically cracked columns, evaluates the relative performance of four different
concrete repair methods for strengthening damaged columns, and describes how to model
pre-existing cracks in the finite element program ATENA.
Previous research on scaled columns used mechanically cracked concrete as an
approximation of ASR/DEF cracking damage. These earlier column tests, by Kapitan,
were compared to two columns affected by ASR/DEF. Due to a deficiency in original
design of the actual columns modeled, all of these scaled column specimens failed in
bearing during testing under biaxial bending. The ASR/DEF affected columns exhibited
nearly identical performance (including bearing capacity) as Kapitan’s control specimen. Thus, with over one percent expansion due to ASR/DEF, there was no reduction in
bearing capacity for these columns.
Based on the bearing failure observed in these scaled column specimens, concrete repairs
were designed to increase confinement of the column capital to address the bearing
capacity deficiency. A series of bearing specimens was constructed, externally
reinforced using four different strengthening schemes, and load tested. From this bearing
specimen series, both an external post-tensioned repair and a concrete jacketing repair
performed well beyond their designed capacities and are recommended for bearing zone
confinement repair of similar ASR/DEF affected concrete columns.
Further, this dissertation presents how Kapitan’s scaled column results were modeled
using ATENA (a reinforced concrete finite element program). A technique for modeling
the mechanical cracking was developed for ATENA. Once calibrated, a parametric study
used the model to find that a 0.17-inch wide through-section crack in the scaled columnd
(5/8 inches in the field) was the threshold that reduced capacity of the scaled column to
the factored design load. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/6656 |
| Date | 23 October 2009 |
| Creators | Talley, Kimberly Grau |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Format | electronic |
| Rights | Copyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works. |
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