Title: CLT and AE Methods of In-Situ Load Testing: Comparison and Development of Evaluation Criteria

Author(s): Paul H. Ziehl, Nestore Galati

Publication: CRC

Volume:

Issue:

Appears on pages(s):

Keywords: in-situ, evaluation, post-tensioned, parking, garage

DOI:

Date: 4/24/2007

Abstract:
The research objective was to compare the results of two recently introduced nondestructive load test methods to the existing 24-hour load test method described in Chapter 20 of ACI 318-05. The two new methods of nondestructive evaluation were the Cyclic Load Test (CLT) and Acoustic Emission (AE) methods. Each method offered advantages over the 24-hour load test method and was particularly well suited to different aspects of structural evaluation. Two cyclic and one 24-hour load test were performed on the floor system of a parking garage in Kansas City, Missouri. In all load tests, the critical cross-section of interest was in the negative moment region at the column location in correspondence with the capital/shear collar. The three tests were performed at load levels producing the moment at the section of interest equivalent to the uniform load applied on the portion of structure under investigation. When tested simulating the presence of the shear collar with shoring posts, the structure passed the cyclic load test since repeatability, permanency, and deviation from linearity were within the limits prescribed by ACI 437. All of the acoustic emission evaluation criteria passed. In addition to the protocol prescribed by ACI 437, the applied load was kept on the structure for 24 hours as per ACI 318 Chapter 20. The structure also met the latter criteria. After strengthening with CFRP, the tested area of the structure did not meet the acceptance criterion on permanency prescribed by ACI 437. The acceptance criterion of 10% prescribed by ACI 437 may be conservative based on the evidence provided by Bares and FitzSimons (1975) showing that a 20% permanency for PC structures is common. The acoustic emission criteria generally passed. Further investigations will be made in relation to three AASHTO type III prestressed girders in the structures laboratory at U. South Carolina. More definitive conclusions regarding the different loading procedures and evaluation criteria will be drawn at the conclusion of that testing program.