In Situ Concrete Bridge Strengthening Using Ductile Activated NSMR CFRP System
Abstract
:1. Introduction
Scope and Research Questions
- The developed ductile strengthening system is applicable for fast and efficient in situ installation.
- Laboratory testing of the assembled and complete CFRP anchorage system will provide high accuracy and thus a low safety factor due to a consistent response and yielding thresholds.
- Proof loading can be used to validate that all other ultimate failure modes from a theoretical safety assessment can be disregarded.
- Does the novel activated CFRP system provide a controlled response with warning and consistent yielding thresholds?
- Can the obtained yielding threshold be used as a capacity threshold?
- Can laboratory testing ensure results that provide a basis for validating the required reliability level?
- How can an in situ proof-loading procedure support further validation of the system resistance and reliability?
2. Bridge Pilot Project
Positioning of the Pre-Stressed Ductile CFRP NSMR System
3. CFRP Strengthening System and Mounting Preparation
4. Testing of CFRP Anchor System
4.1. Positioning of the Pre-Stressed Ductile CFRP NSMR System
4.2. Anchor System Testing
4.3. Design Yield Resistance
- is the expected value of log of test results;
- is the standard deviation of log of test results;
- n is the number of data;
- are the data from tests;
- is a factor used to obtain the characteristic value with being the p = 0.05 quantile of the Student-t distribution with n − 1 degrees of freedom.
- is a factor based on the recommended lifetime reliability index = 3.8 and a sensitivity factor 0.8 implying an exceedance probability = 0.0012, with being the standard Normal distribution function.
5. Mounting, Prestressing, and Verification
5.1. Pre-Stressing, Phase 1
5.2. Pre-Stressing, Phase 2
6. Conclusions
- The laboratory test showed excellent consistency when comparing the load/deformation curves of the anchor system.
- The response can be tailored, primarily controlled by the ductile mechanism.
- Controlled yielding was obtained for all anchor systems tested in the laboratory, thus ensuring a low-yielding threshold safety factor (γR = 1.02).
- The ULS design (yielding threshold) resistance of 60.3 kN fulfilled the required demand for the ULS design resistance of 50 kN, required from the presented unique pilot project.
- In situ proof loading of the strengthening systems (20 anchor systems) showed no signs of distress.
- Proof loading ensured that variations in the unique ultimate failure modes of the mounted anchor systems did not compromise the desired resistance (yielding threshold).
- A good basis is provided for upcoming systems, which can resist significantly higher tailored load magnitudes combined with a desired response.
- A more detailed probabilistic verification seems necessary to ensure that the yielding threshold provides a minimum capacity level not compromised by ultimate capacity variations and to avoid proof-loading entirely.
- The developed NSMR CFRP pre-stressed strengthening system worked as desired and ensured fast mounting and effective controlled prestressing
- After three weeks, acceptable prestress losses ranging from approximately 0.2 to 1.6 kN were observed, corresponding to a full strengthening system (including anchors) and a deformation of 0.2–1.3 mm, respectively.
- The applied strengthening resulted in a bridge class upgrading from standard passage class 20 to class 50 and conditional passage (type 3) class 50 to class 100, as required.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
- El-Hacha, R.; Rizkalla, S.H. Near-Surface-Mounted Fiber-Reinforced Polymer Reinforcements for Flexural Strengthening of Concrete Structures. ACI Struct. J. 2004, 101, 717–726. [Google Scholar]
- Mohamed Ali, M.S.; Oehlers, D.J.; Griffith, M.C.; Seracino, R. Interfacial Stress Transfer of near Surface-Mounted FRP-to-Concrete Joints. Eng. Struct. 2008, 30, 1861–1868. [Google Scholar] [CrossRef]
- Rashid, R.; Oehlers, D.J.; Seracino, R. IC Debonding of FRP NSM and EB Retrofitted Concrete: Plate and Cover Interaction Tests. J. Compos. Constr. 2008, 12, 160–167. [Google Scholar] [CrossRef]
- Seracino, R.; Jones, N.M.; Ali, M.S.; Page, M.W.; Oehlers, D.J. Bond Strength of Near-Surface Mounted FRP Strip-to-Concrete Joints. J. Compos. Constr. 2007, 11, 401–409. [Google Scholar] [CrossRef]
- Sena-Cruz, J.M.; Barros, J.A.O.; Coelho, M.R.F.; Silva, L.F.F.T. Efficiency of Different Techniques in Flexural Strengthening of RC Beams under Monotonic and Fatigue Loading. Constr. Build. Mater. 2012, 29, 175–182. [Google Scholar] [CrossRef] [Green Version]
- Al-Mahmoud, F.; Castel, A.; Franois, R. Failure Modes and Failure Mechanisms of RC Members Strengthened by NSM CFRP Composites—Analysis of Pull-out Failure Mode. Compos. Part B Eng. 2012, 43, 1893–1901. [Google Scholar] [CrossRef]
- Schmidt, J.W.; Krabbe, J.; Sørensen, N.O.; Hertz, K.D.; Goltermann, P.; Sas, G. CFRP Strengthening of RC Beams Using a Ductile Anchorage System. In Proceedings of the 8th International Conference on Fibre-Reinforced Polymer (FRP) Composites in Civil Engineering, CICE 2016, Hong Kong, China, 14–16 December 2016. [Google Scholar]
- Schmidt, J.W.; Hertz, K.D.; Goltermann, P. NSMR Strengthening of Short RC Beams Using Activated Anchorage. In Proceedings of the 9th International Conference on Fibre-Reinforced Polymer (FRP) Composites in Civil Engineering, CICE 2018, Paris, France, 17–19 July 2018. [Google Scholar]
- Sabau, C.; Popescu, C.; Sas, G.; Schmidt, J.W.; Blanksvärd, T.; Täljsten, B. Strengthening of RC Beams Using Bottom and Side NSM Reinforcement. Compos. Part B Eng. 2018, 149, 82–91. [Google Scholar] [CrossRef] [Green Version]
- Nordin, H.; Täljsten, B. Concrete Beams Strengthened with Prestressed Near Surface Mounted CFRP. J. Compos. Constr. 2006, 10, 60–68. [Google Scholar] [CrossRef]
- American Concrete Institute. ACI 440.2R-17: Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures; American Concrete Institute: Indianapolis, IN, USA, 2017; ISBN 9781945487590. [Google Scholar]
- Täljsten, B. Strengthening of Beams by Plate Bonding. J. Mater. Civ. Eng. 1997, 9, 206–212. [Google Scholar] [CrossRef]
- Triantafillou, T.C.; Antonopoulos, C.P. Design of Concrete Flexural Members Strengthened in Shear with FRP. J. Compos. Constr. 2000, 4, 198–205. [Google Scholar] [CrossRef]
- Smith, S.T.; Gravina, R.J. Modeling Debonding Failure in FRP Flexurally Strengthened RC Members Using a Local Deformation Model. J. Compos. Constr. 2007, 11, 184–191. [Google Scholar] [CrossRef]
- Teng, J.G.; Smith, S.T.; Yao, J.; Chen, J.F. Intermediate Crack-Induced Debonding in RC Beams and Slabs. Constr. Build. Mater. 2003, 17, 447–462. [Google Scholar] [CrossRef]
- Said, H.; Wu, Z. Evaluating and Proposing Models of Predicting IC Debonding Failure. J. Compos. Constr. 2008, 12, 284–299. [Google Scholar] [CrossRef]
- Tworzewski, P.; Alexy, J.K.; Barnes, R.W. Intermediate Crack Debonding of Externally Bonded FRP Reinforcement—Comparison of Methods. Materials 2022, 15, 7390. [Google Scholar]
- Gao, B.; Leung, C.K.Y.; Kim, J.K. Prediction of Concrete Cover Separation Failure for RC Beams Strengthened with CFRP Strips. Eng. Struct. 2005, 27, 177–189. [Google Scholar] [CrossRef]
- Corden, G.; Ibell, T.; Darby, A. Concrete Cover Separation Failure in Near-Surface Mounted CFRP Strengthened Concrete Structures. Struct. Eng. 2008, 86, 19–21. [Google Scholar]
- Wight, R.G.; Green, M.F.; Erki, M.-A. Prestressed FRP Sheets for Poststrengthening Reinforced Concrete Beams. J. Compos. Constr. 2001, 5, 214–220. [Google Scholar] [CrossRef]
- Diab, H.; Wu, Z.; Iwashita, K. Short and Long-Term Bond Performance of Prestressed FRP Sheet Anchorages. Eng. Struct. 2009, 31, 1241–1249. [Google Scholar] [CrossRef]
- Yang, D.S.; Park, S.K.; Neale, K.W. Flexural Behaviour of Reinforced Concrete Beams Strengthened with Prestressed Carbon Composites. Compos. Struct. 2009, 88, 497–508. [Google Scholar] [CrossRef]
- Chen, C.; Chen, J.; Zhou, Y.; Sui, L.; Hu, B. Design of Ductile H-Anchorage for Strengthening Reinforced Concrete Beams with Prestressed FRP. Constr. Build. Mater. 2021, 307, 124883. [Google Scholar] [CrossRef]
- D’Amato, M.; Laterza, M.; Casamassima, V.M. Seismic Performance Evaluation of a Multi-Span Existing Masonry Arch Bridge. Open Civ. Eng. J. 2018, 11, 1191–1207. [Google Scholar] [CrossRef]
- Modena, C.; Tecchio, G.; Pellegrino, C.; da Porto, F.; Donà, M.; Zampieri, P.; Zanini, M.A. Reinforced Concrete and Masonry Arch Bridges in Seismic Areas: Typical Deficiencies and Retrofitting Strategies. Struct. Infrastruct. Eng. 2015, 11, 415–442. [Google Scholar] [CrossRef]
- American Concrete Institute. ACI 440.4R-04: Guide for Prestressing Concrete Structures with FRP Tendons; American Concrete Institute: Farmington Hills, MA, USA, 2004. [Google Scholar]
- Nanni, A. North American Design Guidelines for Concrete Reinforcement and Strengthening Using FRP: Principles, Applications and Unresolved Issues. Constr. Build. Mater. 2003, 17, 439–446. [Google Scholar] [CrossRef]
- Jiang, Z.; Fang, Z.; Fang, C.; Li, Q.; Wang, Z. Experimental Investigation on High-Temperature Creep Behavior of Carbon Fiber Reinforced Polymer Cable. Compos. Struct. 2022, 291, 115533. [Google Scholar] [CrossRef]
- Schmidt, J.W.; Bennitz, A.; Täljsten, B.; Goltermann, P.; Pedersen, H. Mechanical Anchorage of FRP Tendons—A Literature Review. Constr. Build. Mater. 2012, 32, 110–121. [Google Scholar] [CrossRef]
- Bennitz, A.; Grip, N.; Schmidt, J.W. Thick-Walled Cylinder Theory Applied on a Conical Wedge Anchorage. Meccanica 2011, 46, 959–977. [Google Scholar] [CrossRef] [Green Version]
- Hansen, C.S.; Schmidt, J.W.; Stang, H. Transversely Compressed Bonded Joints. Compos. Part B Eng. 2012, 43, 691–701. [Google Scholar] [CrossRef]
- Schmidt, J.W.; Bennitz, A.; Täljsten, B.; Pedersen, H. Development of Mechanical Anchor for CFRP Tendons Using Integrated Sleeve. J. Compos. Constr. 2010, 14, 397–405. [Google Scholar] [CrossRef]
- Grelle, S.V.; Sneed, L.H. Review of Anchorage Systems for Externally Bonded FRP Laminates. Int. J. Concr. Struct. Mater. 2013, 7, 17–33. [Google Scholar] [CrossRef] [Green Version]
- Cuntze, R.G.; Freund, A. The Predictive Capability of Failure Mode Concept-Based Strength Criteria for Multidirectional Laminates. Compos. Sci. Technol. 2004, 64, 343–377. [Google Scholar] [CrossRef]
- Schmidt, J.W. External Strengthening of Building Structures with Prestressed CFRP; Technical University of Denmark: Lyngby, Denmark, 2011. [Google Scholar]
- Bennitz, A.; Schmidt, J.W.; Täljsten, B. Failure Modes of Prestressed CFRP Rods in a Wedge Anchored Set-Up. In Proceedings of the Advanced Composites in Construction 2009, ACIC 2009—Proceedings of the 4th International Conference, Toronto, ON, Canada, 16–17 July 2009. [Google Scholar]
- Piątek, B.; Siwowski, T. Experimental Study on Flexural Behaviour of Reinforced Concrete Beams Strengthened with Passive and Active CFRP Strips Using a Novel Anchorage System. Arch. Civ. Mech. Eng. 2022, 22, 1–17. [Google Scholar] [CrossRef]
- Heydarinouri, H.; Motavalli, M.; Nussbaumer, A.; Ghafoori, E. Development of a Mechanical Wedge–Barrel Anchor for CFRP Rods: Static and Fatigue Behaviors. J. Compos. Constr. 2021, 25, 04021015. [Google Scholar] [CrossRef]
- Heydarinouri, H.; Vidovic, A.; Nussbaumer, A.; Ghafoori, E. FE Analysis and Experimental Validation of Mechanical Wedge–Barrel Anchors for CFRP Rods. Compos. Struct. 2021, 275, 114509. [Google Scholar] [CrossRef]
- Schmidt, J.W.; Smith, S.T.; Täljsten, B.; Bennitz, A.; Goltermann, P.; Pedersen, H. Numerical Simulation and Experimental Validation of an Integrated Sleeve-Wedge Anchorage for CFRP Rods. J. Compos. Constr. 2011, 15, 284–292. [Google Scholar] [CrossRef]
- Schmidt, J.W.; Christensen, C.O.; Goltermann, P.; Hertz, K.D. Shared CFRP Activation Anchoring Method Applied to NSMR Strengthening of RC Beams. Compos. Struct. 2019, 230, 111487. [Google Scholar] [CrossRef]
- Schmidt, J.W.; Sena-Cruz, J.; Goltermann, P.; Christensen, C.O. Experimental and Numerical Studies on the Shared Activation Anchoring of NSMR CFRP Applied to RC Beams. In Proceedings of the APFIS 2019 Proceedings—7th Asia-Pacific Conference on FRP in Structures, Gold Coast, Australia, 10–13 December 2019. [Google Scholar]
- Schmidt, J.W.; Christensen, C.O.; Goltermann, P. Ductile Response Controlled EW CFRP Anchor System. Compos. Part B Eng. 2020, 201, 108371. [Google Scholar] [CrossRef]
- Schmidt, J.W.; Christensen, C.O.; Goltermann, P.; Sena-Cruz, J. Activated Ductile CFRP NSMR Strengthening. Materials 2021, 14, 2821. [Google Scholar] [CrossRef]
- Schmidt, J.W.; Christensen, C.O.; Goltermann, P.; Sena-Cruz, J. Activated CFRP NSMR Ductile Strengthening System. In RILEM Bookseries; Springer: Berlin/Heidelberg, Germany, 2022; Volume 34, pp. 349–361. [Google Scholar]
- EN 1990; Eurocode: Basis of Structural Design. European Committee for Standardization: Bruxelles, Belgium, 2002.
- ISO 2394; General Principles on Reliability for Structures: International Standard ISO; Bind 2394. International Organization for Standardization: Geneva, Zwitserland, 2015.
- Joint Committee on Structural Safety. Probabilistic Model Code; Joint Committee on Structural Safety: Deift, The Netherlands, 2002. [Google Scholar]
- Vejdirektoratet (The Danish Road Directorate). Vejledning Til Belastnings- Og Beregningsgrundlag; Vejdirektoratet (The Danish Road Directorate): Hedehusene, Denmark, 2010. [Google Scholar]
- Vejdirektoratet (The Danish Road Directorate). DS/EN 1991-2 DK NA:2017, Annex A: Lastmodeller for Klassificering Og Bæreevnevurdering (Models of Special Vehicles for Road Bridges); Vejdirektoratet (The Danish Road Directorate): Hedehusene, Denmark, 2017. [Google Scholar]
- ABAQUS, Version Abaqus/CAE; Dassault Systèmes Simulia Corp: Johnston, RI, USA, 2021.
Parameter | Value [MPa] |
---|---|
Recommended ult. Stress of the CFRP rod | 2200 1 |
E-modulus CFRP tendon, Ecf | 160.000–170.000 1 |
Stainless steel yield/tension strength of the anchor block parts, fy/fu | 235/700 1 |
Steel yield/tension strength of the barrel, fy/fu | 235/340 1 |
Aluminum (6082-T6, EN 573-3) yield/tension strength | 260/310 1 |
Steel yield/tension strength of the threaded activation bar, fy,bar/fu,bar | 900/1000 1 |
Parameter | Values |
---|---|
Hardness | 60, Shore A (ISO 868) 1 |
Failure stress | 3.0 N/mm2 (ISO 37) 1 |
E-modulus | 3.0 MPa 1 |
Extension at failure | 200% (ISO 37) 1 |
Elasticity | +/−20% 1 |
Curing | 2 mm/day (Environment dependent) 1 |
Mean | COV | Characteristic Resistance, | ULS Design Resistance, (Rd,n) | Partial Factor, (γR) |
---|---|---|---|---|
62.3 kN | 0.01 | 61.7 kN ( = 2.34) | 60.3 kN ( = 7.48) | 1.02 |
Location | 10 kN, Measures με/(kN) | 25 kN, Measures με/(kN) | 55 kN, Measures με/με3; (kN/kN3) | |
---|---|---|---|---|
Beam 1 | Ø (A) | 1269 (10.2) | 3189 (25.6) | 6867/6785; (55.2/54.6) |
V (B) | 1185 (9.5) | 3196 (25.7) | 6852/6743; (55.1/54.2) | |
Beam 2 | Ø (A) | 1211 (9.7) | 3102 (24.9) | 6877/6821; (55.3/54.9) |
V (B) | 1187 (9.5) | 3069 (24.7) | 6841/6696; (55.0/53.9) | |
Beam 3 | Ø (A) | 1281 (10.3) | 3161 (25.4) | 6870/6762; (55.3/54.4) |
V (B) | 1248 (10.0) | 3200 (25.7) | 6882/6795; (55.3/54.6) | |
Beam 4 | Ø (A) | 1226 (9.9) | 3091 (24.9) | 6877/6780; (55.3/54.5) |
V (B) | 1215 (9.8) | 3142 (25.3) | 6883/6804; (55.4/54.7) | |
Beam 5 | Ø (A) | 1354 (10.9) | 3116 (25.1) | 6847/6748; (55.1/54.3) |
V (B) | 1278 (10.3) | 3141 (25.3) | 6844/6780; (55.0/54.5) |
Location | 55kN, Measures με3/μεw (kN3/kNw) | Difference με3-μεw/(kN3-kNw) | |
---|---|---|---|
Beam 1 | Ø (A) | 6785/6666 (54.6/53.6) | 119/(1.0) |
V (B) | 6743/6582 (54.2/52.9) | 161/(1.3) | |
Beam 2 | Ø (A) | 6821/6758 (54.9/54.3) | 63/(0.5) |
V (B) | 6696/6545 (53.9/52.6) | 151/(1.2) | |
Beam 3 | Ø (A) | 6762/6568 (54.4/52.8) | 194/(1.6) |
V (B) | 6795/6627 (54.6/53.3) | 168/(1.4) | |
Beam 4 | Ø (A) | 6780/6630 (54.5/53.3) | 150/(1.2) |
V (B) | 6804/6749 (54.7/54.3) | 55/(0.4) | |
Beam 5 | Ø (A) | 6748/6648 (54.3/53.5) | 100/(0.8) |
V (B) | 6780/6750 (54.5/54.3) | 30/(0.2) |
Location | 55kN, Measures με3/μεw (kN3/kNw) | |
---|---|---|
Beam 1 | Ø (A) | 6899/55.5/1104 |
V (B) | 6938/55.8/1110 | |
Beam 2 | Ø (A) | 6861/55.2/1098 |
V (B) | 6869/55.2/1099 | |
Beam 3 | Ø (A) | 6846/55.1/1095 |
V (B) | 6963/55.9/1114 | |
Beam 4 | Ø (A) | 6938/55.8/1110 |
V (B) | 6888/55.4/1102 | |
Beam 5 | Ø (A) | 6863/55.2/1098 |
V (B) | 6924/55.7/1108 |
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Schmidt, J.W.; Sørensen, J.D.; Christensen, C.O. In Situ Concrete Bridge Strengthening Using Ductile Activated NSMR CFRP System. Buildings 2022, 12, 2244. https://doi.org/10.3390/buildings12122244
Schmidt JW, Sørensen JD, Christensen CO. In Situ Concrete Bridge Strengthening Using Ductile Activated NSMR CFRP System. Buildings. 2022; 12(12):2244. https://doi.org/10.3390/buildings12122244
Chicago/Turabian StyleSchmidt, Jacob Wittrup, John Dalsgaard Sørensen, and Christian Overgaard Christensen. 2022. "In Situ Concrete Bridge Strengthening Using Ductile Activated NSMR CFRP System" Buildings 12, no. 12: 2244. https://doi.org/10.3390/buildings12122244