Effects of mechanical properties of adhesive and CFRP on the bond behavior in CFRP-strengthened steel structures

Li, Chuanxi; Liu, Ke; He, Jun; Chen, Zhuoyi; Jiao, Yang

doi:10.1016/j.compstruct.2018.12.020

Cited by 97 publications

(23 citation statements)

References 27 publications

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“…The elastic modulus and tensile stress of SikaDur®-30 is 11,200 MPa and 31 MPa, respectively. Many works [34][35][36][37][38][39][40] showed that the variation of properties was relatively low.…”

Section: Experimental Programmentioning

confidence: 99%

Flexural Response of CFRP-Strengthened Steel Beams with Initial Bond Defects

Prasertsri¹,

Lenwari²,

Thepchatri³

2020

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This paper presents the flexural behavior of steel beams strengthened with partial-length adhesive-bonded carbon fiber-reinforced polymer (CFRP) plates under static four-point bending. An initial bond defect was intentionally introduced in the constant moment region of the CFRP-strengthened steel beams. In the experimental program, the test variables included the size of the initial bond defect, FRP modulus, FRP plate length, and condition of the steel beam before installation of the FRP plate (undamaged and preyielded conditions). Based on the test results, the presence of the initial bond defect changed the failure mode of FRP-strengthened steel beam from the fiber rupture to intermediate plate debonding. With the initial bond defect, the effectiveness of the FRP strengthening scheme decreased as FRP modulus increased. The stiffness, strength, and ductility index of the CFRP-strengthened beam with the initial bond defect decreased as the defect size increased. However, the initial bond defect had no detrimental effect on the maximum load capacity and ductility index of the strengthened beams. The strengthening effectiveness in terms of stiffness, strength, and ductility enhancement was more pronounced in the case of the pre-damaged steel beam, of which the bottom flange had already yielded before installation of the CFRP plate, than the undamaged steel beam.

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Section: Experimental Programmentioning

confidence: 99%

Flexural Response of CFRP-Strengthened Steel Beams with Initial Bond Defects

Prasertsri¹,

Lenwari²,

Thepchatri³

2020

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“…Conventional repair and retrofit technology of fatigue damages in steel structures include the stop-hole method [11][12][13], weld repair method [14][15][16], reinforcement with steel/carbon fiber reinforced polymer(CFRP) plates method [17][18][19][20][21], concrete overlay methodology [22], etc. These methods are common in fatigue reinforcement engineering projects of OSDs.…”

Section: Introductionmentioning

confidence: 99%

Retrofit Fatigue Cracked Diaphragm Cutouts Using Improved Geometry in Orthotropic Steel Decks

Chen

et al. 2020

Applied Sciences

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Diaphragm cutouts are set to release redundant constraints and hence reduce weld fatigue at the connection of U-ribs to diaphragms in orthotropic steel decks. However, most fatigue cracks which originate from the edge of cutouts are in fact detected in the diaphragms. Therefore, a retrofit technology on cracked cutouts at the diaphragm is proposed and applied to the orthotropic steel box girder of a suspension bridge. Firstly, the stress concentration on the cutout is analyzed through refined finite element analyses. Furthermore, the fatigue cracked cutouts are retrofitted by changing their geometrical parameters. Thereafter, an optimized geometry and the size of diaphragm cutouts were confirmed and applied in the rehabilitation of a suspension bridge. On-site wheel load tests were carried out before and after retrofitting of the diaphragm cutout. The stress distributions along the edges of the cutouts and at the side of a diaphragm were measured under a moving vehicle. The stress spectra at two critical locations on the edge of a cutout was obtained under longitudinally and laterally moving vehicles. Finally, the fatigue life of the cutouts is assessed by the modified nominal stress method. The analytical and test results indicate that the wheel loads on the deck transmit stress to the diaphragms through the U-ribs, during the load transmission process, the stress flow is obstructed by diaphragm cutouts, resulting in local stress concentrations around the cutouts. In addition, the overall size of the cutouts should be small, but the radius of the transition arc should be large, thus the stress flow will not be obviously obstructed. After the retrofitting of the cutouts by improved geometry, the maximum stress decreases by 87.6 MPa, which is about 40% of the original stress. The equivalent constant amplitude stress is reduced by 55.2% when the lateral position of the wheel loads is taken into consideration. Based on the stresses obtained by finite element analysis (FEA) and experimental tests, the fatigue lives of the original cutouts are 1.7 and 4.9 years, respectively, which increase to 78.1 and 155.5 years, respectively, after the cutouts were retrofitted, which indicates that the improved geometry and retrofit technology can enhance the fatigue performance and extend the fatigue life of diaphragm cutouts with fatigue cracks.

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“…As more flexible and simple construction procedures are demanded in the rehabilitation and strengthening of existing concrete structures, post-installed adhesive or grouted anchors are gaining increasing importance [1,6]. Adhesive anchor is the insertion of reinforcing steel rod into cured concrete or masonry block by using a structural adhesive has bonding agent [7][8][9][10][11], holes are drilled into the hardened concrete to allow for postinstalled anchors to be placed at any desired position. Deteriorated concrete are rehabilitated and strengthened using anchors, it can also be used to attach structural elements to existing concrete structures.…”

Section: Introductionmentioning

confidence: 99%

Effect of Epoxy-based Adhesives and Embedded Length in the Bond Strength of Post-installed Reinforcement in Concrete

Ajamu¹,

Atoyebi²,

Oyeboade³

2020

International Journal of Engineering Research and Technology

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In Nigerian building industry, there has been events in practice that required improving the structural integrity of existing structures: such as strengthening the interconnection between members. In cases where new structural members are to be added to the existing ones, instead of condemning the whole structure for demolition and rebuilding, post-installation process offers a remedial approach. However, the bond strength (BS) between the reinforcements and the concrete in the postinstalled structural element goes a long way to determine the anchorage and effectiveness of the whole structural system. In this study, the BS characteristics of post-installed reinforcement in concrete using four different locally available epoxy-based adhesives in Nigeria were examined. Compressive strength test on concrete cubes and pull-out test on post-installed concrete were carried out for embedment lengths of multiples of 10 and 15 of bar diameters used. Average compressive strength at 28 days was 23.91N/mm 2 while the highest BS for 10d and 15d are respectively 5.52 and 6.80 N/mm 2 for 12mm bar diameter while corresponding values are respectively 5.38 and 6.35 N/mm 2 for 16mm bar diameter. From the results, it was observed that the pull-out force which is a measure of bond Stress is more influenced by the embedded length while increasing the embedment depth from 10d to 15d for the same bar size has less influence compared to increasing bar diameter. The epoxy-based adhesives possess appreciable BS characteristics for postinstalled reinforcement in concrete. However, of the three types of adhesives used, Hilti gave the highest BS capacity.

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Effects of mechanical properties of adhesive and CFRP on the bond behavior in CFRP-strengthened steel structures

Cited by 97 publications

References 27 publications

Flexural Response of CFRP-Strengthened Steel Beams with Initial Bond Defects

Flexural Response of CFRP-Strengthened Steel Beams with Initial Bond Defects

Retrofit Fatigue Cracked Diaphragm Cutouts Using Improved Geometry in Orthotropic Steel Decks

Effect of Epoxy-based Adhesives and Embedded Length in the Bond Strength of Post-installed Reinforcement in Concrete

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