Modelling and simulation of deterioration, repair and strengthening of reinforced concrete structures

Transcription

1 Modelling and simulation of deterioration, repair and strengthening of reinforced concrete structures Geir Horrigmoe NORUT Technology, Narvik Norway 1 st Annual FENET Industry Workshop, Wiesbaden, Germany, November 13 15, 2001

2 Deterioration of concrete infrastructure Widespread problems of deterioration of reinforced concrete structures have been experienced in many countries. The registered need for repair and rehabilitation and the associated, estimated cost is a major concern of companies, municipalities and public agencies. An efficient infrastructure is one of the prerequisites for continued development and growth.

3 Retrofitting of reinforced concrete structures Protection: Seeks to maintain the existing condition. (surface treatments, inhibitors, electrochemical methods) Repair: Seeks to restore mechanical properties (stiffness, strength) and durability in order to maintain design service life. ( mechanical repair ) Strengthening: Seeks to increase stiffness and strength of the structure. (external bonding of FRP sheets or plates)

4 General performance of conventional retrofitting methods Often unsatisfactory performance, especially durability. High (in many cases prohibitive) cost. No simple or universal procedure exists. In the future, repair and retrofitting procedures should be able to provide increased load-carrying capacity and extended service life at reasonable cost ( We must do more and better for less ). Need for new, innovative methods for retrofitting of concrete structures.

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7 Analysis of deteriorated and retrofitted concrete structures There is a need to predict stiffness and strength: in the deteriorated state, to assess the structural consequences of the observed damage. in the planning and design of repair, to assess the safety of repair operations. after repair (and strengthening) has been completed and the structure has been put back into service, to assess the serviceability and ultimate capacity of the retrofitted structure.

8 Why do we need numerical simulations? Deterioration (especially reinforcement corrosion) leads to nonlinear behaviour (loss of bond, cracking, spalling). Complex distributions of strains and stresses. Current repair techniques involve removal of deteriorated material and addition of new, strain-free materials. The entire history of loading, straining, deterioration and repair or strengthening needs to be taken into account. Realistic predictions cannot be obtained by analytical methods or simple hand calculations.

9 Deterioration, repair and strengthening I) Deterioration

10 Deterioration, repair and strengthening II) Repair

11 Deterioration, repair and strengthening III) Strengthening f) Application of externally bonded FRP sheet or plates. g) Repaired and strengthened beam is loaded until failure.

12 Typical load-deflection deflection diagram of deteriorated, repaired and strengthened beam Design load Load g S Service load b g NS c Permanent load a d e f Deflection

13 Analysis of full scale beam

14 Beam with uniform corrosion and pitting exp = 0.5 L exp 50 Load [kn/m] ULS load 41.3 kn/m SLS load 31.8 kn/m Permanent load 23.8 kn/m B1CEB-FIP-S B1C - 25%U - 0.5L B1C - 25%U+38%P -0.5L Calculated failure load Central deflection [mm]

15 What do we handle well? Finite element discretization of the composite structure. Constitutive models for concrete (?), steel, fibre reinforced composite and adhesive (?). Solution algorithms.

16 What do we need to improve? Modelling of corrosion of embedded reinforcement and the relation between corrosion and loss of bond. Algorithms for changing cross sectional areas, stiffness characteristics, removing or adding finite elements while the structure is subjected to a given loading. Modelling of interfaces: Bond slip of steel reinforcement without or with corrosion attack. Debonding of composite material (brittle failure).

17 The ultimate goal Environment Maintenance Durability design Structural design