Technical seminar reportvon Barron Wang
The seminar on GFRP as reinforcement for concrete structure was held on June 18th in University of Toronto. There were about 50 attendees from MTO, consulting firms and contractors in this seminar.
FRP is composed of 2 part of materials: fibre and matrix. The combining fibre and matrix gives a composite material with superior properties. GFRP has been used as reinforcement for concrete structures, as GFRP has strong corrosion resistance and is considered a cost effective alternative. It’s about 50% of cost of stainless steel. For Combar GFRP, the ultimate tensile strength is 1300 MPa, modulus of elasticity is 63000MPa, ultimate elongation is 2.06% and density is 2.2 g/cm3. Some tests have been conducted on GFRP structures, such as beams, cold temperature and durability of GFRP in concrete.
FRP product specification was introduced in the seminar. It addressed the qualification testing, quality control/assurance tests, materials and manufacturing. There are three GFRP bars in Ontario market, Aslan, ComBAR and V-Rod. The design codes of concrete structure with internal FRP reinforcement are CSA S806-02 and CHBDC S-06. There are some calculation examples on moment, cracking width, shear, deflection etc. The 401 WB collectors Bridge #2 over Humber River is a good example on application of GFRP in bridge decks.
On the application of GFRP, bend bars are always a concern. The University of Waterloo carried out the tests and the GFRP bars were supplied by Schoeck Company. The strength of the bent bars was higher than expected, resulting in concrete failure prior to GFRP bar failure. Bonding strength is not negatively affected by bending. For the same anchored length, the peak load was higher for a bent bar.
Bonding is always a top topic in application of GFRP bars in concrete. Extensive tests have been conducted. ‘De-bonding’ appears to be the primary failure mode of GFRP reinforced concrete structure members.
The seminar went very well. It gave many engineers confidence in using GFRP products. On the other hand, it pointed out the different GFRP suppliers have different performance. For example, for the same size, ComBAR bars have much better properties than the other 2 suppliers. It can give the engineers flexibility when they design the structures.