000203633 001__ 203633
000203633 005__ 20190317000046.0
000203633 0247_ $$2doi$$a10.1016/j.engstruct.2014.11.017
000203633 022__ $$a0141-0296
000203633 02470 $$2ISI$$a000349882100003
000203633 037__ $$aARTICLE
000203633 245__ $$aDetermination of minimum CFRP pre-stress levels for fatigue crack prevention in retrofitted metallic beams
000203633 260__ $$aOxford$$bElsevier$$c2015
000203633 269__ $$a2015
000203633 300__ $$a13
000203633 336__ $$aJournal Articles
000203633 520__ $$aThe majority of fatigue strengthening studies focus on reducing propagation rates of existing cracks, ignoring the crack initiation stage. Many existing metallic bridge members however do not contain existing cracks, but rather are nearing their design fatigue life. Limited research exists on the prevention of crack initiation using carbon fiber reinforced polymer (CFRP) materials. In this paper, constant life diagrams (CLDs) are used to determine the minimum level of CFRP pre-stress required to indefinitely extend the fatigue life of existing metallic beams. It is shown that by applying a compressive force to an existing fatigue-susceptible detail using pre-stressed CFRP plates, the mean stress level can be reduced such that the detail is shifted from the 'finite life' regime to the 'infinite life' regime. The proposed fatigue strengthening approach is advantageous particularly when the stress history from the prior traffic loadings is not known. To validate the proposed method, a pre-stressed un-bonded CFRP reinforcement system is introduced and tested on four metallic beams. The proposed un-bonded CFRP system is advantageous over traditional bonded CFRP systems as it can be applied to rough or obstructed surfaces (surfaces containing rivet heads or corrosion pitting for example). Additionally, the new un-bonded CFRP system offers a fast on-site installation (no glue and surface preparation are required) and an adaptive pre-stress level. Experimental results show that strengthening using pre-stressed CFRP plates are capable of shifting the working stresses from a finite fatigue-life zone to an infinite fatigue-life zone preventing crack initiation. Although according to many structural standards, the stress range is the main parameter that affects the fatigue life of a metallic detail, the results of this study clearly show that the mean stress level also plays a significant rule in the detail fatigue life. Based on the proposed CLD approach in this paper, the combined effects of the stress range and mean stress level can be taken into account for prediction of fatigue life of metallic members. (C) 2014 Elsevier Ltd. All rights reserved.
000203633 6531_ $$aFatigue damage prevention
000203633 6531_ $$aMean stress influence
000203633 6531_ $$aConstant life diagram (CLD)
000203633 6531_ $$aFatigue crack
000203633 6531_ $$aMetallic beams
000203633 6531_ $$aPre-stressed carbon fiber reinforced
000203633 6531_ $$apolymer (CFRP)
000203633 6531_ $$aStrengthening
000203633 6531_ $$aSteel
000203633 700__ $$aGhafoori, E.
000203633 700__ $$aMotavalli, M.
000203633 700__ $$0243059$$aNussbaumer, A.$$g113159
000203633 700__ $$aHerwig, A.
000203633 700__ $$0245201$$aPrinz, G.S.$$g208996
000203633 700__ $$aFontana, M.
000203633 773__ $$j84$$q29-41$$tEngineering Structures
000203633 8564_ $$s1740731$$uhttps://infoscience.epfl.ch/record/203633/files/Engineering%20Structures%2084%20%282015%29%2029%E2%80%9341.pdf$$yn/a$$zn/a
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000203633 917Z8 $$x106673
000203633 937__ $$aEPFL-ARTICLE-203633
000203633 973__ $$aEPFL$$rREVIEWED$$sPUBLISHED
000203633 980__ $$aARTICLE