Fatigue Behaviour of FRP Reinforced Concrete Structural Elements
Typ i c a l f a t i g u e l o a d i n g pattern ( E l - R a g a by, e t a l . , 2 0 0 7 )
S – N c u r ve a n d fatigue limit ( w w w. s ub s t e c h. c om / , 2 0 1 5 )
Problem statement - FRP products usage is in great expansion - Great savings are possible over the whole life of a structure - Fatigue is one of the most important issues in FRP concrete design
Politecnico di Milano
Schöck ComBAR® in bridges ( w w w. s c ho e c k c o m b a r. c o m / , 2 0 1 5 )
ESR
Ana Veljkovic
Supervisor: Prof. Valter Carvelli
E xp e r i m e n t a l s e t u p f o r fatigue testing (Carvelli, et al.,2010)
Future fields of investigation - Fatigue life diagrams of FRP rebar and concrete bond: experimental investigation - In-depth knowledge of the FRP rebar and concrete adhesion behavior under cyclic loading - Experimental investigation of the GFRP reinforced concrete slabs exposed to fatigue - Numerical modelling for prediction of fatigue behavior of FRP reinforced concrete structural elements
Crack pattern on slab bottom below jack (Carvelli, et al.,2010)
Failure of GFRP slab under fatigue ( S i v a ga m a s un da r i , e t a l . , 2 0 0 8 )
Aims - Obtaining appropriate knowledge of the FRP rebar and concrete bond - Collecting data of real member/s truc ture response under fatigue loading - Understanding , simulating and predicting the behaviour of FRP RC members and structures by numerical modelling using FEM - Assessing and comparing the design rules and standards available for both, steel and FRP reinforcement and extending existing guidelines
Bond stress-slip relationships a ) s h e a r - b o n d f a i l u r e , b ) c o ve r - c r a c k f a i l u r e , c ) f a i l u r e b y s p l i t t i n g o ff t h e s u r r o u n d i n g c o n c r e t e ( Te p f e r s , e t a l . , 2 0 0 3 )
Motivation - Still few experimental data exist on the long -term fatigue performance of GFRP reinforced concrete structural elements - Lack of appropriate standard test methods for fatigue behavior of FRP bars - Recommendati ons and Standard didn’t consider enough the design of concrete elements reinforced with FRP bars under fatigue loadings
Stress state in concrete around a deformed bar ( G u d oni s , e t a l . , 2 0 1 4 )
Te n s i l e - st r e s s d i s t r i b u t i o n s ( Te p f e r s , e t a l . , 2 0 0 3 )
A l t e r n a t i ve s h a p e s f o r t h e a r e a o f t r a n s ve r s e s t r e s se s i n t h e c a s e o f t h i n c o n c r e t e c o ve r (Horak, et al.,2013)
Two - d i me n s i o n a l , a xi s ym m e t r i c finite element model of smooth r o d , wi t h p r o b e , i n c o n c r e t e (Bakis, et al.,1998)
Experimental investigation of static and fatigue behaviour of the bond between GFRP rebar and concrete - Joint work of Politecnico di Milano and University of Kaiserslautern - Influence of the concrete cover on the bond of FRP bar and concrete - The pull-out set-up with eccentrically positioned GFRP bar to measure the effect of three parameters:
Experimental setup
(1) thickness of the concrete cover, (2) diameter and surface of the bar, (3) concrete mechanical properties.
- Static behaviour of bond done in March/April 2015, - Over 100 samples tested, - Strain measurement by 2D and 3D DIC, - Fatigue tests in October 2015.
Bar surfaces before (up) and after (down) static tests
DIC map of the strain at the maximum load on a surface centered on bond length, for: 20 mm concrete cover ( left), 15 mm (middle) and 10 mm concrete cover (right)
Representative shear stress vs. slip curves for the bar diameter 8mm, 3 concrete covers and 2 concrete strengths
Marie Curie Initial Training Network European Network for Durable Reinforcement and Rehabilitation Solutions http://www.endure-itn.eu
