1. EWHA WOMANS UNIVERSITY ARCHITECTURAL STRUCTURE LABORATORY Investigation of Rehabilitation Effects on Fire Damaged High Strength Concrete Beams Eun Mi Ryu 1, Ah Young An 1, Ji Yeon Kang 2, Yeong Soo Shin 3, Hee Sun Kim 3 1 : M.S., Ewha Womans University, Seoul, South Korea 2 : Ph.D, Ewha Womans University, Seoul, South Korea 3 : Professor, Ewha Womans University, Seoul, South Korea

2. Research backgrounds and objectives Experimental approach and results Analytical approach and results Conclusion Parametric studies

3. Research backgrounds and objectives  When high strength reinforced concrete is exposed to high temperature due to fire, deteriorations occur :  Reduction in strength and elastic modulus  Cracking and spalling of the concrete  Loss of bond between concrete and steel 3

4. Research backgrounds and objectives 4  Types of repair materials  Fibre Reinforced polymer (FRP)  Epoxy injection for structural cracks  Polymeric mortar  Concrete jacketing  Steel Jacketing  Shotcreteing

5. Experimental approach and results 5  Experimental approach  Specimen -From the compressive test, averaged value is obtained as 54.39MPa -Mixture ratios for concrete are listed in Table -Width, depth and length of high strength concrete beams are 250mm, 400mm and 4700mm, respectively compressive strength (MPa) W/C (%) s/a (%) Weight per unit volume (kg/m 3 ) WCSGAD 54.3931411685426669741.6

6. Experimental approach and results 6  Experimental approach  Fire test and rehabilitation -Specimens are heated according to the ISO 834 standard time temperature curve -The beams are subject to four-point loading -After fire test, fire damaged U-shaped concrete cover is removed. And removed part is filled with polymeric cement mortar.

7. Experimental approach and results 7  Experimental approach  Test set-up -Specimens are simply supported with an effective span of 3750mm and subject to four-point loading  Variable -cover thickness(40, 50mm), fire exposed time period(0, 1 hour), rehabilitation(or not) Specimen Cover Thickness (mm) Fire exposed time period (sec) Rehabilitation H4BC40-- H4B1H403600- H4B1HR403600○ H5BC50-- H5B1H503600- H5B1HR503600○

8. Experimental approach and results 8  Experimental results  Specimen having cover thickness of 40 mm and 50 mm 5.4 % (ultimate load) 0.7% (ultimate load)

9. Experimental approach and results 9  Experimental results Specimen Ultimate load (kN) Slope (kN/mm) Exp_H4BC 254.113.3 Exp_H4B1H 220.19.4 Exp_H4B1HR 268.014.3 Exp_H5BC 248.013.2 Exp_H5B1H 177.06.6 Exp_H5B1HR 249.714.0 7.3 % (ultimate load)

10. Analytical approach and results 10  Analytical approach ABAQUS version 6.10-3, is used. And three-dimensional FE models are with width, depth and length equal to experimental conditions  Step 1 Temperature analysis  Step 2 Integrated temperature-structural analysis  Step 3 Structural analysis of rehabilitated beams and damaged beams PartTemperature Ratio of original strength Concrete lower than 500°C90 % Steel lower than 500°C90 %

11. Analytical approach and results 11  Analytical results  Specimen having cover thickness of 40 mm and 50 mm

12. Analytical approach and results 12  Analytical results  Stress contour of FE models for beam having cover thickness of 40mm -High stresses are distributed in rehabilitated part while low stresses are found in damaged concrete part. (a)Stress contour of concrete part (b)Stress contour of rehabilitated part

13. Parametric studies 13  Approach of parametric studies  Parametric studies are performed in order to predict the structural behavior of high strength RC beam according to strength of polymeric mortar.  Parameters are strength of two different polymeric cement mortar such as 59.7MPa and 44.4MPa. DescriptionUnitMortar type AMortar type B Elastic modulusMPa2921025540 Compressive strength MPa59.7244.40 Poisson’s ratio 0.2 Densitykg/m 3 20 Model Condition Cover thickness H4B1HRARehabilitated with mortar type A40mm H4B1HRBRehabilitated with mortar type B40mm H5B1HRARehabilitated with mortar type A50mm H5B1HRBRehabilitated with mortar type B50mm

14. Parametric studies 14  Results of parametric studies  Specimen having cover thickness of 40 mm and 50mm 11.4 % (ultimate load) 13.3% (ultimate load)

15. Conclusion 15  The results obtained from experiments and FE analyses are summarized as follows:  In the experiments, the ultimate load of the rehabilitated beam is similar to that of the control beam. So, high strength concrete beam can be reused if a damaged beam due to fire is rehabilitated with polymeric cement mortar.  The load-deflection curves of the beams from the FE analyses are in good agreement with those of the experiments.  The ultimate loads of the beams heated for 1hour are fully recovered regardless of strengths of polymeric cement mortar.  It is found that the ultimate loads and slopes of beams having cover thickness of 40mm are higher than those of beams having cover thickness of 50mm.

16. EWHA WOMANS UNIVERSUTY ARCHITECTURAL STRUCTURE LABORATORY