Strengthening of Damaged Concrete Beams by External Prestressing of Aramid Fiber Cable


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Title: Strengthening of Damaged Concrete Beams by External Prestressing of Aramid Fiber Cable

Author(s): N. Saeki

Publication: Special Publication

Volume: 138


Appears on pages(s): 913-932

Keywords: beams (supports); cable; cements; composite materials; repairs; epoxy resins; fatigue tests; fibers; flexural strength; prestressing; load-deflection curve; portland cements; reinforcing materials; stiffness; strengthening; tests; Structural Research

Date: 9/1/1993

An experimental study of rehabilitation methods was investigated using artificially damaged concrete beams. The rehabilitation consisted of strengthening the damaged concrete beams by external post-tensioning, and some beams were not only externally prestressed but were also specially injected with epoxy resin to repair several sizes of cracks. Static as well as fatigue tests for three-point bending were conducted to investigate the effect of these rehabilitation methods. Fatigue tests of PRC strengthened by external cable were conducted at 2 million cycles, with a stress level of 33 percent of the ultimate static beam strength and cable tension force of 34 percent of tensile strength. From these test results, the static behavior of deformation and ultimate strength of the rehabilitated beams were confirmed as reasonably upgraded and strengthened by the proposed method. The results indicate that the deflection and ultimate strength of beams for the yield stage can be estimated by theoretical calculation. For the plastic hinge formation stage, deflection and ultimate strength were also evaluated by theoretical calculation. The change in beam rigidity was found to differ insignificantly before and after fatigue tests. In the same manner, ultimate bending strength of beams before and after fatigue tests was nearly the same. As a result of measuring the ratio of loss in the tension force of aramid rope, values of approximately 10 percent were obtained for all three stress states.