CREEP RUPTURE STRENGTH OF V-ROD #3 GFRP REINFORCING BARS

Transcription

1 NSERC Research Chair in Innovative FRP Composite Materials for Infrastructure CREEP RUPTURE STRENGTH OF V-ROD #3 GFRP REINFORCING BARS Prepared by: Pierre-Olivier Caron Perigny, B. Eng., Mathieu Robert, Ph.D., and Brahim Benmokrane, P. Eng., Ph.D. Professor of Civil engineering NSERC Research Chair in Innovative FRP Composite Materials for Infrastructure Department of Civil Engineering University of Sherbrooke Sherbrooke, Quebec CANADA J1K 2R1 Phone: (819) Fax: (819) Submitted to: Pultrall, Inc. Thetford Mines, Quebec August 31th, 2012

2 INTRODUCTION The purpose of this report is to evaluate creep rupture strength of sand-coated V-ROD Glass FRP bars manufactured by Pultrall, Inc., as required by CAN/CSA S807 code FRP Product Certification [1]. The GFRP bars were shipped to the Industrial NSERC Research Chair in Innovative FRP Composite Materials for Infrastructures at the Department of Civil Engineering at the University of Sherbrooke for testing in the materials and durability laboratories. The GFRP bars of sizes # 3 (nominal diameter 10mm) were received and tested. TEST METHOD AND PROCEDURES This report presents the results of creep-rupture tests of GFRP bar-samples subjected to different levels of sustained axial load using sustained load frame of durability laboratory of the University of Sherbrooke, shown in Figure 1. These tests are being conducted in compliance with ACI 440.3R-04, Test Method B.8, Test Method for Creep Rupture of FRP Bars [2]; or CSA-S806-02, Annex J, Test Methods for Creep of FRP Rods [3] (both based on ASTM D 7337 standard, Standard Test Method for Tensile Creep Rupture of Fiber Reinforced Polymer Matrix Composite Bars [4]). a) b) Figure 1: Sustained load frame: a) Specimen under sustained load, b) Schematic view of the frame 1

3 TEST RESULTS Prior to installation in sustained load frames, V-ROD #3 GFRP bars, of the same batch, were tested under static tensile tests to determine the initial longitudinal tensile properties of non-conditioned samples (reference) according to ASTM D7205 Standard [5], Standard Test Method for Tensile Properties of Fiber Reinforced Polymer Matrix Composite Bars. or CSA-S [3], Annex C, Test Method for Tensile Properties of FRP Reinforcements. The obtained values were used as reference for the subsequent creep and creep-rupture tests, Table 1. The nominal cross-sectional areas provided by the CAN/CSA S807 [1] was considered in the calculation of the tensile strength and the elastic modules for all the tested bars. It should be mentioned that the LVDTs were removed at about 80% of the ultimate capacity of the other five specimens not to break the LVDTs. Table 1. Tensile properties of GFRP bar samples (reference samples) Bar Size (Nominal Diameter) [Nominal Area] V-ROD#3 (9 mm) [71 mm2] Specimen Ultimate tensile strength (MPa) Modulus of elasticity (GPa) Ultimate strain (%) Average S.D C.O.V Table 2 presents the rupture time for GFRP bars under sustained loads. Figure 2 presents the logarithmic time to failure (stress rupture) curve for V-ROD #3 GFRP bars. 2

4 Table 2. Details on Creep-rupture for V-ROD #3 GFRP bars V-ROD#3 Mean Applied Load on Bars 84% of UTS 1080 Mpa 72% of UTS 910 MPa 65% of UTS 860 MPa 59% of UTS 800 Mpa Rupture time (hours) Figure 2. Logarithmic Time to Failure (Stress Rupture) Curve for V-ROD GFRP bar #3 3

5 CONCLUSIONS According to Figure 2, the tendency curve fit from the 4 sets of data obtained by testing V-ROD GFRP bars #3 at stress ratio of 84%, 72%, 65% and 59 % f u,ave, the rupture strength, which is the 10 6 strength, is 45% f u,ave. The creep rupture strength value of V- ROD #3 is above the specified limit (35% of ultimate tensile strength for GFRP bars) according to CAN/CSA-S807 [1], FRP product specification. REFERENCES 1. CAN/CSA-S807-10, 2010, FRP Product Specification, Canadian Standards Association, Rexdale, Ontario, Canada, 31 p. 2. ACI 440.3R-4, 2004, Guide Test Methods for Fibre-Reinforced Polymers (FRPs) for Reinforcing or Strengthening Concrete Structures, American Concrete Institute, Farmington Hills, Michigan, USA, 41 p. 3. CAN/CSA-S806-02, 2002, Design and Construction of Building Components with Fibre Reinforced Polymers, Canadian Standards Association, Rexdale, Ontario, Canada, 177 p. 4. ASTM D 7337, 2007, Standard Test Method for Tensile Creep Rupture of Fiber Reinforced Polymer Matrix Composite Bars. ASTM D 7337, Philadelphia. 5. ASTM D 7205, 2006, Standard Test Method for Tensile Properties of Fiber Reinforced Polymer Matrix Composite Bars. ASTM D 7205, Philadelphia. 4