Junrui Zhang, Ph.D. Candidate ([email protected])
Enrique del Rey Castillo, Senior Lecturer in Structural Engineering Lucas Hogan, Senior Lecturer in Structural Engineering
Tom Allen, Senior Lecturer in Mechanical Engineering
Optimizing the Design of EB-FRP on RC Strengthening: Impact of Large-sized FRP Ties and Anchors
Fifty-one single lap shear tests were conducted. The critical parameters under consideration were concrete compressive strength, FRP thickness, and bond length.
PREDICTIVE MODEL FOR UNANCHORED TIES
A systematic literature review was conducted using the Scopus and Web of Science databases spanning the period between 1994 and 2022. Yielding two datasets of existing tests.
SYSTEMATIC LITERATURE REVIEW
[3-5]Collected unanchored tests encompassed the range of critical parameters were shown below, and a 3D plot have also been plotted.
• Unanchored specimens exhibited debonding failure, while anchored specimens experienced diverse failure modes: fan debonding, fabric fracture, and anchor rupture.
• Debond strain is correlated with FRP stiffness-to-concrete stiffness ratio, revealing a non-linear power relationship with potential future design implications.
• The debond strain in unanchored specimens was primarily influenced by the stiffness and length of the FRP. Thicker ties improved anchorage capacity, and longer ties exhibited greater post-debond deformation capacity, which depends on both the bonded length and the stiffness (thickness) of the tie.
• Larger anchors and increased spacing improved system capacity and enabled load sharing between two anchors up to a spacing of 24 inches (609.6 mm).
CONCLUDING REMARKS
[1, 6]A strength model is proposed for FRP systems under pure tension, which aligns well with both the published and tested results.
Externally bonded fibre reinforced polymer (EB-FRP) techniques have been widely recog- nized as an excellent seismic retrofit strategy for structures. Existing research was limited to short and thin FRP strips with small and shallow FRP anchor(s). which are often not repre- sentative of real in-situ construction scenarios. Recent experimental works has shed light on the debond strain capacity, the post-debond deformation capacity.
INTRODUCTION
[1,2]portionKey
REFERENCE
[1] Zhang, J., del Rey Castillo, E., Kanitkar, R., & D Borwankar, A. (2023, June). Behaviour of Large FRP Ties for Seismic Strengthening of Concrete Diaphragms. In Structural Engineering Society New Zealand (SESOC) 2023 Conference, Christchurch, New Zealand..
[2] del Rey Castillo, E. N. R. I. Q. U. E., Kanitkar, R. A. V. I., & Smith, S. T. (2019). Floor diaphragm strengthening of concrete structures with FRP. In Proc., 2019 Concrete New Zealand Conf (pp. 1-5).
[3] del Rey Castillo, E., Harries, K. A., Rogers, R., & Kanitkar, R. (2022). FRP Tension Ties: State-of-the-Art Review of Existing Design Guidance for Debonding Capacity and Applicability to Concrete Diaphragm Seismic Strengthening. Journal of Composites for Construction, 26(2), 04022014.
[4] del Rey Castillo, E., Kanitkar, R., Smith, S. T., Griffith, M. C., & Ingham, J. M. (2019a). Design approach for FRP spike anchors in FRP-strengthened RC structures. Composite Structures, 214, 23-33.
[5] del Rey Castillo, E., Dizhur, D., Griffith, M., & Ingham, J. (2019b). Experimental testing and design model for bent FRP anchors exhibiting fibre rupture failure mode. Composite Structures, 210, 618-627.
[6] Zhang, J., Kanitkar, R., del Rey Castillo, E., Harries, K.A., Rogers, R., & Borwankar, A. (2023, July 3). BOND BEHAVIOUR OF FRP FOR PURE AXIAL TENSION STRENGTHENING OF CONCRETE. 11th International Conference on Fiber-Reinforced Polymer (FRP) Composites in Civil Engineering (CICE 2023), Rio de Janeiro, Brazil. https://doi.org/10.5281/zenodo.8108872
Inputs: Configuration of anchor(s), failure modes, and theories development
Outputs: Potential variables, comparison with available guidelines and proposed models.
Number of tests collected
(2145, by 14 Apr, 2023) Systematically categorized
(Criteria for included and excluded)
Input 1: General information
(Sources, DAQs and instrumentation)
Input 2: Variables of material
(Concrete, adhesive and FRP)
Outputs: Results of tests
(Loads, strain and energy)
Experimental testing was undertaken to evaluate the interfacial bond behavior of thick and long FRP ties bonded on concrete using the testing setup shown in below.
Specimens
DIC system Actuator
Load cell
Ruler Targets
The intent of the anchored test was to observe if and how the anchors, including the length of the splay and the spacing between the anchors, modified the failure mode of the FRP strips.
SYSTEM BEHAVIOUR OF FIBRE ANCHORED TESTS
[6]152
152 457
1/2/3/4 layers Unbonded area
Primaryfiber direction
152
1372 914
Direction of loading
152
152.4 457.2
1 layer
Unbonded area
Primaryfiber direction
152
1372
Fibreanchor
Fan Length = 406 mm Hole diameter = 13 (19 or 25) + 3 mm
Hole depth = 102 + 6 mm Splay anchor fan over the exterior fabric layer.
152662406
Direction of loading
152
152
152 457
2 layers
Unbonded area
Primaryfiber direction
Fibreanchor
Fan Length = 305 mm Hole diameter = 13 (19 or 25) + 3 mm Sandwich anchor splay between FRP layers
305305305
When debonding starts, the force progresses along the ties till the anchor is engaged. The
progression results in a plateau as the displacement increases without a significant change in the force. Also, the two-anchor specimens exhibit a similar behaviour to the one-anchor ones.
0.0 0.5 1.0 1.5
Once the DIC data is analysed, the progression of debonding along the strips, between the an- chors, and the resulting stress in the strips will be better understood.
FRP bond length (𝒍 )
FRP stiffness (𝒌 ) 12 in.
(304.8 mm) 24 in.
(609.6 mm) 36 in.
(914.4 mm) 60 in.
(1524 mm) 54 in.
(1371.6 mm) FRP tie (370 g/m2 [11 oz./yd.2]) with 2 layers (𝒕 = 1 mm) 19.2/19.5/36.1 MPa 19.2/19.5/36.1 MPa 19.2/19.5/36.1 MPa 20.7/41.4/41.4 MPa N/A FRP tie (370 g/m2 [11 oz./yd.2]) with 1 layer (𝒕 = 0.5 mm) 19.2/19.5/36.1 MPa 19.2/19.5/36.1 MPa 19.2/19.5/36.1 MPa N/A N/A FRP tie (370 g/m2 [11 oz./yd.2]) with 3 layers (𝒕 = 1.5 mm) 19.2/19.5/36.1 MPa 19.2/19.5/36.1 MPa 19.2/19.5/36.1 MPa N/A N/A FRP tie (370 g/m2 [11 oz./yd.2]) with 4 layers (𝒕 = 2 mm) 19.2/19.5/36.1 MPa 19.2/19.5/36.1 MPa 19.2/19.5/36.1 MPa N/A N/A FRP tie (1,490 g/m2 [44 oz./yd.2]) with 1 layer (𝒕 = 2 mm) N/A N/A N/A 20.7/20.7/20.7/41.4/
41.4/41.4 MPa 27.6/27.6 MPa
FRP tie (740 g/m2 [22 oz./yd.2]) with 4 layers (𝒕 = 4 mm) N/A N/A N/A N/A 20.7/41.4 MPa
FRP tie (1,490 g/m2 [44 oz./yd.2]) with 3 layers (𝒕 = 6 mm) N/A N/A N/A N/A 27.6/27.6 MPa