Load Testing of Existing Concrete Structures (Part 1)-Cyclic and Monotonic Load Tests for Strength Evaluation of Prestressed Concrete Beams (PDF)

Cyclic and Monotonic Load Tests for Strength Evaluation of Prestressed Concrete Beams (PDF)

Pdf Summary

The document presents an overview of load testing methods for assessing the strength of prestressed concrete beams, specifically focusing on cyclic and monotonic load tests. These tests are crucial for evaluating existing structures, ensuring their safety and performance under prescribed loads.<br /><br />The historical context highlights the evolution of load testing standards, initially incorporated into the ACI regulations in 1920. There are two principal frameworks discussed: ACI 318, which traditionally uses the monotonic load test, and ACI 437.2-13, that permits both cyclic and monotonic tests but with slight differences in the test load magnitude. <br /><br />The monotonic load test is described as a proof test that is slower but easier to perform, with criteria based on deflections. It requires a minimum performance over a 48-hour period. Conversely, the cyclic load test is faster and based on stiffness, employing hydraulic systems to react against a counterforce.<br /><br />Acceptance criteria for these tests are detailed, with the monotonic test focusing on maximum and residual deflection. For cyclic tests, criteria include deviation from linearity, permanency ratio, and residual deflection.<br /><br />A laboratory study detailed in the document involved eight prestressed T-shaped beam specimens subjected to varying conditions of pre-cracking and corrosion. The cyclic load test involved 14 application cycles, providing insights into the load levels at which the beams failed, while the monotonic test results were evaluated using both ACI 318 and ACI 437 standards.<br /><br />The conclusions highlight differences in applied load criteria between standards and note that neither standard explicitly determines the ultimate structural capacity. While ACI 437.2-13 offers a detailed commentary and addresses serviceability in load ratings, its acceptance criteria successfully identify damage in specimens, which can differ widely from the ACI 318 criteria outcomes.

Keywords

load testing

prestressed concrete beams

cyclic load test

monotonic load test

ACI 318

ACI 437.2-13

structural safety

deflection criteria

pre-cracking

corrosion