STRENGTHENING OF CONCRETE STRUCTURE External prestress External bonding reinforcement Member enlargement Member replacement Seismic upgrading New member installation For each type of strengthening, there are several methods. The selection of strengthening methods depends on technical considerations, cost etc.
STRENGTHENING OF CONCRETE STRUCTURE Phan Huu Duy Quoc, Ph D The University of Tokyo Purposes of strengthening Retrofitting degraded structure Upgrading current structure to higher load bearing capacity to cope with changes in structural conditions or applied load Load bearing capacity Compensating design and construction faults Initial design value Degradation Time 1) Retrofitting degraded structures Time 2) Upgrading current structure Strengthening Time 3) Compensating design and construction faults Types of strengthening External prestress External bonding reinforcement Member enlargement Member replacement Seismic upgrading New member installation For each type of strengthening, there are several methods The selection of strengthening methods depends on technical considerations, cost etc 1 External prestress (1) Strengthening cable Prestress is introduced by either external or internal cable for - Adding shear and flexural capacity of member - Closing cracks, reducing displacement - Connecting single beams to form continuous beams External prestress (2) Types of cable: • Continuous Fiber reinforced polymer (CFRP) • Steel cable Design and application Analysis should be carried out on the strengthened members like the calculation of a prestressed member External cable is used in most cases The selection of steel or FRP rod depends on cost performance, construction condition, environmental condition, etc An example of using FRP rod for external prestress Fiber reinforced polymer (FRP) Advantages of FRP - High durability - Light weight (1/5 of steel) - High strength FRP Sheet Typical representation of Continuous FRP (CFRP) 2a External bonding reinforcement using steel plate (1) Anchor bolt Concrete Adhesive (Epoxy resin) Steel plate Bolt cap 2a External bonding reinforcement using steel plate (2) Strengthening a bridge slab by steel plate bonding Strengthening whole section of a tunnel by steel plate bonding 2b External bonding reinforcement using FRP sheet (1) From FRP to concrete strengthening Using FRP for strengthening bridge slab 2b External bonding reinforcement using FRP sheet (2) Strengthening a degraded slab Strengthening a degraded slab FRP Sheet FRP Sheet FRP Sheet Member enlargement Section enlargement with new concrete layer and steel bars Old Asphalt Surface treatment New Asphalt New concrete New bar Old concrete Case Case Member enlargement Section enlargement by shotcrete (Concrete or mortar projected at high pressure onto the target surface) Concrete comes out of nozzle Strengthening a structure by shotcrete Member replacement When the degradation is so severe, the replacement of a portion or whole member is one of strengthening options Seismic upgrading (1) Adding bracing system Steel wrapping External prestress FRP wrapping FRP wrapping Seismic upgrading (2) Load (tf) Before Strain Load (tf) After Strain Using spiral for strengthening concrete column Strengthening by wrapping with RC/PC concrete or precast panels New member or support structure installation (1) Sealing material Slab Pavement Epoxy injection Main beam Additional beam New member or support structure installation (2) Adding additional beam Adding new support Adding bracing system [...]... with new concrete layer and steel bars Old Asphalt Surface treatment New Asphalt New concrete New bar Old concrete Case 1 Case 2 3 Member enlargement Section enlargement by shotcrete (Concrete or mortar projected at high pressure onto the target surface) Concrete comes out of nozzle Strengthening a structure by shotcrete 4 Member replacement When the degradation is so severe, the replacement of a portion... a portion or whole member is one of strengthening options 5 Seismic upgrading (1) Adding bracing system Steel wrapping External prestress FRP wrapping FRP wrapping 5 Seismic upgrading (2) Load (tf) Before Strain Load (tf) After Strain Using spiral for strengthening concrete column Strengthening by wrapping with RC/PC concrete or precast panels 6 New member or support structure installation (1) Sealing... Strengthening by wrapping with RC/PC concrete or precast panels 6 New member or support structure installation (1) Sealing material Slab Pavement Epoxy injection Main beam Additional beam 6 New member or support structure installation (2) Adding additional beam Adding new support Adding bracing system ... surface) Concrete comes out of nozzle Strengthening a structure by shotcrete Member replacement When the degradation is so severe, the replacement of a portion or whole member is one of strengthening. .. value Degradation Time 1) Retrofitting degraded structures Time 2) Upgrading current structure Strengthening Time 3) Compensating design and construction faults Types of strengthening External prestress... installation For each type of strengthening, there are several methods The selection of strengthening methods depends on technical considerations, cost etc 1 External prestress (1) Strengthening cable