Bai ging vt liu FRP references (2)

An Introduction to FRPStrengthening of Concrete Structures Source Repair with FRP reinforcement Module Objectives • To introduce students to the general philosophies and procedures for strengthening structures with FRPs Repair with FRP reinforcement Introduction Section: • The world’s population depends on an extensive infrastructure system • Roads, sewers, highways, buildings • The system has suffered in past years • Neglect, deterioration, lack of funding Global Infrastructure Crisis Repair with FRP Introduction reinforcement Section: • A primary factor leading to extensive degradation… Corrosion Concrete Reinforcing Steel Moisture, oxygen and chlorides penetrate Through concrete Through cracks Corrosion products form Volume expansion occurs More cracking Corrosion propagation End result Repair with FRP reinforcement Introduction Section: • Advantages Lightweight High Strength Easy to install 5x steel FRP Materials Corrosion resistant Durable structures Highly versatile Suit any project Repair with FRP reinforcement Type Flexural Shear Confinement FRP Materials Section: FRP-Strengthening Applications Application Fibre Dir Schematic Tension and/or Along long side face of axis of beam beam Side face of beam (u-wrap) Perpendicular to long axis of beam Around column Circumferential Section Section Section Repair with FRP FRP Materials reinforcement Section: General • Wide range of FRP products available: • Plates • Rigid strips • Formed through pultrusion • Sheets • Flexible fabric Carbon FRP sheet Repair with FRP FRP Materials reinforcement Section: Installation Techniques uWet lay-up Used with flexible sheets Saturate sheets with epoxy adhesive Place on concrete surface Epoxy Roller Resin acts as adhesive AND matrix Repair with FRP FRP Materials reinforcement vPre-cured Section: Installation Techniques Used with rigid, pre-cured strips Apply adhesive to strip backing Place on concrete surface Not as flexible for variable structural shapes Resin acts as adhesive AND matrix Repair with FRP reinforcement Evaluation of Existing Structures Section: Deficiencies • Deficiencies due to: Then Now v Updated Design Loads w Updated design code procedures Repair with FRP reinforcement Strengthening Section: Shear Strengthening Repair with FRP reinforcement Strengthening Section: Shear Strengthening Effective strain in FRP laminates Completely wrapped members Prevents shear cracks from widening beyond acceptable limits Loss of aggregate interlock of the concrete Bonded U-wraps or bonded face plies Repair with FRP reinforcement Strengthening Section: Shear Strengthening Bonded U-wraps or bonded face plies The active bond length Le is the length over which the majority of the bond stress is maintained Repair with FRP reinforcement Strengthening Section: Shear Strengthening Reinforcement limits The total shear reinforcement should be taken as the sum of the contribution of the FRP shear reinforcement and the steel shear reinforcement ISIS EC Module Composites Column Strengthening FRP Section: For Construction External Reinforcement • Confining reinforcement for concrete columns:  Concrete members can be wrapped with FRPs  Increases the axial and shear strength and deformation capacity of these members A A Elevation Section A-A Concrete bridge column strengthened with externally-bonded carbon FRP wraps Repair with FRP Column Strengthening reinforcement Section: • FRP sheets can be wrapped around concrete columns to increase strength • How it works: Overview Internal reinforcing steel Concrete FRP wrap Concrete shortens… …and dilates… …FRP confines the concrete… ISIS EC Module flfrp …and places it in triaxial stress… Repair with FRP reinforcement Column Strengthening Section: Overview • The result: Increased load capacity Increased deformation capability ISIS EC Module Repair with FRP reinforcement Column Strengthening Section: Overview • The result: ISIS EC Module Repair with FRP reinforcement Column Strengthening Section: Overview • Pure axial compression members with existing steel spiral reinforcement • Pure axial compression members with existing steel tie reinforcement The additional reduction factor Repair with FRP reinforcement Column Strengthening Section: Overview • Strength of confined concrete Repair with FRP reinforcement Column Strengthening Section: Overview • Strength of confined concrete • Circular cross sections k a = 1.0 • Noncircular cross sections Repair with FRP reinforcement Column Strengthening Section: Rectangular Columns • External FRP wrapping may be used with rectangular columns • There is far less experimental data available for rectangular columns • Strengthening is not nearly as effective Confinement all around Confinement only in some areas Repair with FRP reinforcement Column Strengthening Section: Add’l Considerations Shear • External FRP wrapping may be used with circular and rectangular RC columns to strengthen also for shear • Particularly useful in seismic upgrade situations where increased lateral loads are a concern Repair with FRP reinforcement Additional Applications Section: NSM Techniques • Newer class of FRP strengthening techniques: near surface mounting reinforcement (NSMR) Unstrengthened Longitudinal grooves concrete T-beam cut into soffit FRP strips placed Grooves filled in grooves with epoxy grout • Research indicates NSMR is effective and efficient for strengthening Repair with FRP reinforcement Column Strengthening Section: Overview • Homework ... es efrp Strain Distribution fs ffrp Stress Distribution a1Φcf’c Cc Ts Tfrp Equiv Stress Distribution Repair with FRP reinforcement Flexural Strengthening Section: General Design Repair with FRP. .. in FRPs can be ignored Repair with FRP reinforcement Evaluation of Existing Structures Environmental-reduction factor for various FRP systems and exposure conditions Section: Repair with FRP. .. Repair with FRP FRP Materials reinforcement Section: General • Wide range of FRP products available: • Plates • Rigid strips • Formed through pultrusion • Sheets • Flexible fabric Carbon FRP sheet