Near Surface Mounted Reinforcement A. Palmieri, UGent

Transcription

1 Near Surface Mounted Reinforcement A. Palmieri, UGent

2 RC beams strengthened with NSM reinforcement: Ambient and Fire behaviour A. Palmieri, S. Matthys KVIV-studiedag Nieuwe generatie gelijmde wapening Antwerpen 29/11/211 Near Surface Mounted (NSM) FRP GFRP rods CFRP/GFRP strip CFRP rods 1

3 NSM FRP: Applications Concrete Cover Adhesive NSM FRP High bond characteristics Higher utilization FRP bars Improved resistance to fire FRP Properties at High Temperatures FRP fibers generally exhibit a good fire resistance Epoxy lose strength and stiffness at temperature close to Tg Borchert 24 Tg: Glass transition temperature is commonly taken as the performance limit for the FRP strengthened members - Typically 6 8 C - 2

4 FRP and Fire: Concerns Fire is recognized as a critical research need for FRP: a primary factor preventing widespread application on FRPs in buildings Potential concerns during fire: Loss of strength and stiffness Loss of interaction (bond) adhesive/frp/concrete Smoke generation and flame spread Problem Statement: Concrete structures strengthened with FRPs perform weak under fire conditions : thermal protection is required Research Objectives Evaluate the performance of NSM FRP strengthened and insulated members at ambient temperature and under fire exposure Develop practical methods for protecting FRP strengthening system during fire exposure Evaluate the performance of different insulation materials type in terms of efficiency and in terms of practical application Investigate the residual capacity of the fire tested beams 3

5 Sample Specimens Q 1 Q Strain Gauges 25 Dial Gauges and LVDT CFRP rods 9 mm Test Matrix Beam FRP GFRP rods 12 mm 4 CFRP strips 2x16 mm x D f f f E f Epoxy T g f c Age at testing [mm] [Mpa] [Gpa] resin [ C] [MPa] [days] B B1 Combar GFRP Sikadur B2 Aslan 2 CFRP Fortresin B3 Aslan 5 CFRP 2x Fortresin Installations FRP NSM Bars/Strips 1. Cutting Grooves and Cleaning 2. Filling with adhesive 3. Insert bar/strip 4. Final levelling 4

6 Test Results Beam P y [kn] P y /P yb [%] P u [kn] P u /P ub [kn] u [mm] u [%] u / f u [-] Failure mode B Yielding steel / concrete crush B Debonding FRP B Debonding FRP B Debonding FRP Concrete Crush Debonding FRP Fire Insulations Insulation Insulation type Density [kg/m 3 ] Conductivity [W/mK] Application Promat-H Calcium silicate board Mech. Fixed Promat L-5 Calcium silicate board 5.9 Mech. Fixed Aestuver Glass fiber cement board Mech. Fixed WR-APP type C Cementitious plaster 24.8 Spry applied HPC/Omega Ceramic coating Spry applied Spry applied Mechanically fixed 5

7 Z3 Z3 Fire Test Matrix First Fire Test Series B-F1 2 1 B1-F1-2 B1-F1-1 B2-F1-1 B2-F1-2 B3-F mm mm m 12 3 mm mm 3 mm 4 mm 15 mm m mm m 4 mm Second Fire Test Series B-F2 B1-F2-1 B1-F2-2 B1-F2-3 B2-F2-1 B2-F hours fire exposure mm mm 15+1 mm 4+2 mm 15+1 mm mm 15 mm mm 11 4 mm 12 2 mm 3 25 Third Fire Test Series B1-F mm mm B1-F3-2 B1-F3-3 B1-F3-4 B4-F mm mm mm mm mm mm mm 15 2 mm3 3 B2-F mm 1 hour fire exposure Test Set-up HEM 3 HEM 3 HEM 3 HEB 55 HEB2 jack 2 kn HEB2 HEB2 HEA 12 Frame in Gypsum B-F1 B1-F1-1 B3-F1-1 B1-F1-2 B2-F1-1 B2-F1-2 T1 T2 T3 T4 T5 B1 B2 B3 B4 The fire test is executed according to EN standard fire test method Heating according to ISO 834 time temperature curve T gs T 345log 8t 1 1 Tem mperature ( C) HE EB2 75 T7 HEM 3 HEB55 HEA16 1 Insulation System 132 HE EB2 Pla1 Pla2 Pla3 Pla4 Pla5T2 Pla6 Pla7 Pla8 Pla9 Pla1 ISO834 ISO834 ± 1 B7 B Time (min) 6

8 Load During Fire Test Beams loaded to service load Beam Q sl [kn] Q U [kn] Q sl,frp /Q sl,b [%] B B B Q sl /Q u,b [%] Q sl = service load Q u = ultimate load Q sl /Q u,b = % ultimate capacity of unstrength beam Q sl,frp /Q sl,b = % service capacity of unstrength. beam Fire Tests Instrumentation Thermocouple type K Mineral wool Aerated conc. slab Sect.1/2 4-point bending frame Fire LVDT 7

9 Beams After Fire Exposure Before test After 2 hours fire exposure Insulation detached after 34 minutes Beams After Fire Exposure (II) Before test After 2 hours fire exposure Crack due to the thermal shrinkage 8

10 Beams After Fire Exposure (III) Before test After 1 hour fire exposure perature [ o C] Temp 1 3 Test Results: Temperature Adhesive min 3.1 Tg Tg B1-F2-1 B2-F1-2 B1-F2-3 B1-F2-3 B2-F2-1 B2-F Tg Tg 1 34 min 3 2 Tg min 34 min 6 min Tg Time [min] ture [ºC] Temperat min B1-F3-3 B1-F3-2 B4-F3-1 B1-F Tg 1.8Tg 1.6Tg 38 min 5 min time [min] 9

11 Test Results: Deflection Beams 7 e deflection [mm] Increas min B-F2 B1-F2-1 B2-F1-2 B1-F2-3 B2-F Time [min] 12 lection [mm] Increase defl B1-F3-2 B1-F3-1 B4-F3-1 B1-F Time [min] Fire Endurance Exposur e time 2 hours 2 hours 1 hour Beam Insulation T concrete [ C] T steel [ C] T adhesive [ C] T Tadh=Tg [min] B-F B1-F1-1 Promat-H B2-F1-1 Aestuver B2-F1-2 Aestuver B3-F1-1 Aestuver B-F ,6 - - B1-F2-1 Promat L B1-F2-2 HPC/Omega Fire B1-F2-3 HPC/Omega Fire B2-F2-1 WR- APP type C B2-F2-2 WR-APP type C B1-F3-1 Promat L B1-F3-2 HPC/Omega Fire B1-F3-3 HPC/Omega Fire B1-F3-4 HPC/ Omega Fire B2-F3-1 Promat L B4-F3-1 HPC/ Omega Fire T adh at 1 and 2 hours of fire exposure T g erature ( C) Tempe EN No failure under applied loads T Steel 57 ºC [158 ºF] T unexp.,av. 14 ºC [284 ºF] T unexp. 18 ºC [356 ºF] T c,steel T steel B4-F3-1 B1-F3-3 B1-F3-2 B-F1 B2-F1-2 B2-F2-1 B1-F2-3 B1-F min Time (min) 1

12 Residual Strength Test Set-up All dimensions are in millimeters Q 1 Q Dial gauges and LVDTs Strain stirrups FRP point bedding Residual Strength Test Results Q 11 [kn] B T=25 C 5 B-F s [mm] Q 11 [kn] B1-F2-2 B1 T=25 C B T=25 C s [mm] T adh.,2hours = 281.3ºC T adh.,2hours = 27.3ºC Q 11 [kn] 1 B2 T=25 C B T=25 C 6 5 B2-F s [mm] Failure mode: Concrete Crush 11

13 Tadh.,1ours= 11.4ºC Residual Strength Test Results Qu,Res.= 155% Qu,B Qu,Res= 92.% Qu,B1 12 B1-F3-4 1 Load [kn] B1 T=25 C B1-F2-3 B T=25 C 84 kn concrete crush started 88.7 kn debonding FRP bar Qu,Res.= 156% Qu,B B1-F3-3 Qu,Res= 92.7% Qu,B Load [kn] Tadh.,2hours= 159.6ºC Qu,Res.= 134 % Qu,B Qu,Res= 79% Qu,B1 Q 11 [kn]1 84 kn concrete crush started 7 8 s [mm] 9 Tadh.,1ours= 11.6ºC displacement [mm] 89 kn debonding FRP bar B1-F3-3 B1_2 2 B displacement [mm] Failure mode: Debonding FRP/Concrete crush Conclusions FRP strengthened beams can achieve up to 1 or 2 hours fire endurance ratings under service load if well insulated. For none of the strengthened beams FRP NSM detached visibly, though temperature measurements may indicate reduced bond integrity after 34 to t 12 minutes. i t Efficiency of fixation of the protection during fire appeared to have a large influence. The U shaped protection seems to be more efficient than the flat one. After fire exposure, the insulated beams were able to retain all of the original unstrengthened flexural capacity by maintaining the temperature of the concrete and steel respectively below 14 ºC and 57 ºC If the insulation is able to maintain the adhesive temperature at relatively low temperature (16 ºC for these tests), the FRP concrete bond degradation under fire is limited and the FRP strengthened beam is still able to retain a considerably part of the original strength (up to 97% for 1 hour fire exposure and 8% for 2 hours of fire exposure). 12

14 Acknowledgements Thank you for your attention QUESTIONS???????? 13