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Interaction between CFRP-repair and initial damage of wide-flange steel beams subjected to three-point bending
This paper has presented an experimental program to examine the interaction between carbon fiber reinforced polymer (CFRP) repair and initial damage of steel beams loaded in flexure. Three different sizes of notches were created at midspan of the beams to simulate the level of damage. A predictive FEA model was developed and the response was compared with that of the experimental beams. The following is concluded. (1) CFRP-repair increased the load-carrying capacity of the damaged steel beams up to 22.5%, while the improvement in yield capacity was more noticeable after the repair (i.e., increase up to 32.2% in yield load). Such a repair method, however, decreased the energy-dissipation capacity of the repaired beams until the peak load was reached, in particular significant when the notch depth was greater than 30% of the section depth. Care should be taken when a repair design is conducted for repairing severely cracked steel beams using CFRP sheets. (2) All damaged beams failed due to wide notch-opening, followed by crack propagation towards the upper flange. For the repaired beams, local debonding of the CFRP at the notch location was first observed and it progressed along the CFRP-steel interface. These failure modes were independent of the level of initial damage (notch depth). CFRP-repair was effective for reducing crack-opening of the damaged beams and delayed crack-formation across the steel section; however, once cracks progressed towards the upper flange, the contribution of the CFRP became insignificant. Designers need to consider a method that precludes CFRP-debonding so that CFRP can provide sustainable repair effects. U-wraps at damage locations may be recommended for this purpose. (3) The level of initial damage did not influence the strain development of the CFRP sheet at a damage location, whereas it contributed to rapid debonding progression of the sheet. The predicted CFRP strains along the CFRP-steel interface agreed well with those of the experiment until moderate debonding of the sheet occurred (i.e., service load level); however, the model provided more sensitive debonding prediction when load levels approached the ultimate state. Refined modeling techniques should be developed to better predict the crack propagation of damaged steel beams, including discrete crack propagation of steel sections. (4) Two distinct bond-slip responses were observed: the primary debonded region that exhibited softer bond-slip behavior than the secondary debonded regions. This experimental finding may guide a new direction to improve existing bond-slip models. Stress concentrations induced by the initial damage (notch) significantly affected the local slip of the CFRP.
Interaction between CFRP-repair and initial damage of wide-flange steel beams subjected to three-point bending
This paper has presented an experimental program to examine the interaction between carbon fiber reinforced polymer (CFRP) repair and initial damage of steel beams loaded in flexure. Three different sizes of notches were created at midspan of the beams to simulate the level of damage. A predictive FEA model was developed and the response was compared with that of the experimental beams. The following is concluded. (1) CFRP-repair increased the load-carrying capacity of the damaged steel beams up to 22.5%, while the improvement in yield capacity was more noticeable after the repair (i.e., increase up to 32.2% in yield load). Such a repair method, however, decreased the energy-dissipation capacity of the repaired beams until the peak load was reached, in particular significant when the notch depth was greater than 30% of the section depth. Care should be taken when a repair design is conducted for repairing severely cracked steel beams using CFRP sheets. (2) All damaged beams failed due to wide notch-opening, followed by crack propagation towards the upper flange. For the repaired beams, local debonding of the CFRP at the notch location was first observed and it progressed along the CFRP-steel interface. These failure modes were independent of the level of initial damage (notch depth). CFRP-repair was effective for reducing crack-opening of the damaged beams and delayed crack-formation across the steel section; however, once cracks progressed towards the upper flange, the contribution of the CFRP became insignificant. Designers need to consider a method that precludes CFRP-debonding so that CFRP can provide sustainable repair effects. U-wraps at damage locations may be recommended for this purpose. (3) The level of initial damage did not influence the strain development of the CFRP sheet at a damage location, whereas it contributed to rapid debonding progression of the sheet. The predicted CFRP strains along the CFRP-steel interface agreed well with those of the experiment until moderate debonding of the sheet occurred (i.e., service load level); however, the model provided more sensitive debonding prediction when load levels approached the ultimate state. Refined modeling techniques should be developed to better predict the crack propagation of damaged steel beams, including discrete crack propagation of steel sections. (4) Two distinct bond-slip responses were observed: the primary debonded region that exhibited softer bond-slip behavior than the secondary debonded regions. This experimental finding may guide a new direction to improve existing bond-slip models. Stress concentrations induced by the initial damage (notch) significantly affected the local slip of the CFRP.
Interaction between CFRP-repair and initial damage of wide-flange steel beams subjected to three-point bending
Wechselwirkung zwischen Reparatur mit kohlenstofffaserverstärktem Kunststoff und Anfangsschaden von Breitflansch-Stahlträgern unter Dreipunktbiegungbelastung
Kim, Yail J. (Autor:in) / Brunell, Garrett (Autor:in)
Composite Structures ; 93 ; 1986-1996
2011
11 Seiten, 11 Bilder, 2 Tabellen, 34 Quellen
Aufsatz (Zeitschrift)
Englisch
Wechselwirkung , Reparatur , Schädigung , Stahlträger , Biegebeanspruchung , Kerbe , Finite-Elemente-Methode , Tragfähigkeit , Energiedissipation , Spitzenlast , Tiefe (geometrische Größe) , Riss , Rissausbreitung , Flansch (Verbindungselement) , Schichtablösung , Grenzfläche , Dehnung , Modell , Gleiten , Spannungskonzentration , Elastizitätsgrenze , kohlenstofffaserverstärkter Kunststoff , Polymermatrix-Verbundwerkstoff , Umwinden
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