NEW BRIDGE STRUCTURESAberfeldy Footbridge- UK Built on a Golf Course World’s first cable-stayed footbridge Constructed in 1992 113m long with 63m main span All composite materials used for construction of this bridge
Contd..Bonds Mill Bridge - UK Bascule vehicular traffic bridge Constructed in 1994 27ft long and 14ft wide by 2.8ft deep Maximum loading capacity of a 40-ton truck Six-cell box composite girder used for the construction
ENCLOSURESSecond Severn Enclosure System - UK Constructed in 1993 Bridge bottom soffit enclosure system 40 psf is the design load with a L/120 deflection
BONDED STEEL PLATESGiezenen Bridge - Switzerland Made of reinforced concrete dual-tied arch Consists of concrete hangers and Orthotropic beam & slab deck 102 ft span Constructed in 1980 Steel plates bonded to all transverse & longitudinal deck beams
Contd..Koblenz/ Waldshut Railway Bridge - Switzerland Historical railroad made of Wrought Iron Built in 1859 Constructed to increase capacity for double-deck commuter trains Method employed was to bond steel plates to cross-girders
BONDED CARBON LAMINATESCo-op City Departmental Store - Switzerland Reinforced concrete floor slab Constructed in 1996 CFRP Laminates –To allow floor cutouts for elevator shafts and escalator openings
Contd..Ibach Bridge – Switzerland 748 ft long bridge Construction 1991 Coring external box damaged tendon in 128 ft span 16.4 ft x 1.75 in x 6 in CFRP Laminate plates bonded to box to rectify the damage
Contd..Oberriet Rhein Bridge Rhein River Switzerland-Austria Rehabilitation & LL capacity upgrade & bottom soffit strengthening Construction 1996 3-Span Steel Girder Bridge (35ft-45ft-35ft) CFRP Laminate strips bonded to bottom of deck between main girders in positive moment region
Contd..Furstenland Bridge - Switzerland Multi-Cell box arch bridge Extensive corrosion of box Carbon Laminates bonded to lower portion of webs inside box during removal and replacement of bottom box slab areas
Contd..Hiyoshigura Viaduct – Japan Bridge deck strengthening for increase from TL20 to TL25 trucks Tonen tow sheet & Sho-bond CFRP bonding method
CABLESStorchenbrucke (Stork Bridge) - Switzerland First cable-stayed road bridge 406 ft Length with Pylon Height of 125 ft Construction in 1994-96; 2 of 24 CFRP cable stays
ROPEAKASHI-KAIKYO Bridge - Japan 7.531ft main span / 283ft towers Pilot rope for main cables
TENDONSSUMITOMO BRIDGES - Japan Oyama Works – Sumitomo Construction Co, Ltd. Pre/post-tensioned demonstration Internal post-tensioned box – 10 TecvhnoraR 6 mm strands External post-tensioning – 7 TecvhnoraR 6 mm strands 8 mm AFRP Bars for stirrups and deck reinforcement
Contd..SCHIESSBERGSTRASSE Bridge - Germany 174 ft Long by 32 ft Wide with 3.7 ft Depth Post-tensioned with 27 continuous parabolic HLV-Polystal tendons Comprised of 19 E-glass rods Continuously monitored-Optical Fiber Sensors
Structural FRP Composite plate binding Commentsneed/deficiency solutionCorrosion of reinforcement Replacement of lost Damaged concrete mustin reinforced concrete reinforcement by plates of be replaced without equivalent effect impairing behavior of platesInadequate flexural Design FRP composite plate Extent of strengtheningcapacity in reinforced bonding solution to add tensile limited by capacity ofconcrete elements concrete in compressionSafety net to cover Add plates, either stressed or Method appropriate withuncertain durability of pre unstressed, to ensure safety segmental constructionstressed concreteLost pre stress due to Replace pre stress that has Need to ensure nocorrosion in pre stressed been lost with stressed overstress of concrete inconcrete composites the short term
Structural need/deficiency FRP Composite plate binding Comments solutionInadequate stiffness or Add external pre stress by means of aserviceability of cracked stressed composite platereinforced concrete structurePotential overstress due to Design composite reinforcement beforerequired structural alteration removing load bearing membersAvoidance of sudden failure Addition of either stressed orby cracking of cast iron unstressed composite plate bonding to the tensile faceEnhancement of shear External bonding of stressed plates or Web reinforcementcapacity by web reinforcement techniques little researched
Advantages of epoxy resin over otherpolymersThe advantages of epoxy resins over other polymers as adhesiveagents for civil engineering use can be summarized as follows: High surface activity and good wetting properties for a variety of substrates. May be formulated to have a long open time (the time between mixing and closing of the joint). High cured cohesive strength, so the joint failure may be dictated by the adherent strength, particularly with concrete substrates. May be toughened by the inclusion of a dispersed rubbery phase.
Contd.. Minimal shrinkage on curing, reducing bond line strain and allowing the bonding of large areas with only contact pressure. Low creep and superior strength retention under sustained load. Can be thixotropic for application to vertical surfaces. Able to accommodate irregular or thick bond lines. Formulation can be readily modified by blending with a variety of materials to achieve desirable properties.
Advantages of FRP CompositePlate BondingStrength of plates: FRP composite plates may be designed withcomponents to meet a particular purpose and may comprise varyingproportions of different fibers. The ultimate strength of the plates canthus be varied, but for strengthening schemes the ultimate strength ofthe plates is likely to be at least three times the ultimate strength ofsteel for the same cross-sectional area.Weight of plates: The density of FRP composite plates is only 20% ofthe density of steel. Thus composite plates may be less than 10% ofthe weight of steel of the same ultimate strength. Apart from transportcosts, the biggest saving arising from this is during installation.Composite plates do not require extensive jacking and support systemsto move and hold in place. The adhesives alone will support the plateuntil curing has taken place. In contrast, fixing of steel platesconstitutes a significant proportion of the works costs.
Transport of plates: The weight of plates is so low that a 20 m longcomposite plate may be carried on site by a single man. Some platesmay also be bent into a coil as small as 1.5 m diameter, and thus maybe transported in a car or van without the need for Lorries orsubsequent craneage facilities. The flexibility of plates enablesstrengthening schemes to be completed within confined spaces.Versatile design of systems: steel plates are limited in length by theirweight and handling difficulties. Welding in situ is not possible, becauseof damage to adhesives, and expensive fixing of lap plates is thereforerequired. In contrast, composite plates are of unlimited length, may befixed in layers to suit strengthening requirements, and are so thin thatfixing in two directions may be accommodated by varying the adhesivethickness.
Easy and reliable surface preparation: Steel plates requirepreparation by grit blasting, followed by careful protection until shortlybefore installation. In contrast, the ROBUST project has demonstratedthat composite plates may be produced with a peel-ply protective layerthat may be easily stripped off just before the adhesive is applied.Reduced mechanical fixing: Composite plates are much thinner thansteel plates of equivalent capacity. This reduces peeling effects at theEnds of the plates and thus reduces the likelihood of a need for endfixing. The overall depth of the strengthening scheme is reduced,Increasing head-room and improving appearance.
Durability of strengthening system: There is the possibility ofcorrosion on the bonded face of steel plates, particularly if the concreteto which they are fixed is cracked or chloride contaminated. This couldreduce the long term bond. Composite plates do not suffer from suchdeterioration.Improved fire resistance: Composite plates are a low conductor ofheat when compared with steel, thus reducing the effect fire has on theunderlying adhesives. The composite itself chars rather than burns andthe system thus remains effective for a much longer period than steelplate bonding.
Reduced risk of freeze/thaw damage: There is theoretical risk ofwater becoming trapped behind plate systems, although this should notoccur if they are properly installed. In practice, this has not been foundto be a problem. However, if water did become trapped in this way, theInsulating properties of the composite materials would reduce the riskof disruption of the concrete due to freeze/thaw. Loss of bond wouldalso be evident by tapping the composite, but would be more difficult todetect with steel.Maintenance of strengthening system: Steel plates will requiremaintenance painting and may incur traffic disruption and access costsas well as the works costs. Composite plates will not require suchmaintenance, reducing the whole life cost of this system.
Reduced construction period: Many of the practical advantagesdescribed above combine to enable composite plates to be installed ingreatly reduced time periods when compared with steel plates. As wellas lower contract costs, the traffic delay costs are minimized.Installation from mobile platforms becomes possible and it may becomepracticable to confine work within such restraints as limited railwaypossessions or night-time working.Ability to pre stress: The ability to prestress composites opens up awhole new range of applications for plate bonding. The plate bondingmay be used to replace lost prestress and the shear capacity ofsections will be increased by the longitudinal stresses induced.Formation of cracks will be inhibited and the serviceability of thestructure en-hanced. Strengthening of materials such as cast iron alsobecomes more practicable.
Disadvantages of FRP CompositePlate BondingCost of plates: Fiber reinforced composite plates are more expensivethan steel plates of the equivalent load capacity. However, thedifference between the two materials is likely to be reduced asproduction volumes and competition between manufacturer’sincreases. Comparison of total contract costs for alternative methods ofstrengthening will be based on labor and access costs as well asmaterial costs. Open competition has already shown that FRPcomposite plate bonding is the most economic solution in virtually alltested cases, without taking into account additional advantages such asdurability.
Mechanical damage: FRP composite plates are more susceptible todamage than steel plates and could be damaged by a determinedattack, such as with an axe. In vulnerable areas with public access,the risk may be removed by covering the plate bonding with a rendercoat. Fortunately, if damage should occur to exposed FRP compositeplate, such as by a high load, repairs can be undertaken much moreeasily than with a steel plate. A steel plate may be dislodged, or bondbroken over a large area, which would damage bolt fixings andnecessitate complete removal and replacement.However, with FRP composite plate bonding the damage is more likelyto be localized, as the plate is thinner and more flexible. With FRPcomposite, the plate may be cut out over the damaged length, anda new plate bonded over the top with an appropriate lap.
CONCLUSIONS Fiber reinforced composite plate bonding offers significant advantages over steel plate bonding for the vast majority of strengthening applications. No construction or repair method involving structural analysis and deterioration mechanisms can be said to be completely understood, including all of those currently in everyday use. However, FRP composite plate bonding has been sufficiently researched to enable the techniques to be applied confidently on site, providing care is taken. The method of FRP composite plate bonding is here to stay and is already being actively marketed. The number of applications worldwide is set to grow very fast. The challenge is to ensure that these applications take full account of the current state of knowledge. The benefits must not be put at risk by inappropriate or badly detailed applications under-taken by the inexperienced.
Future Composite Applications Internal Structural Aircraft Components Human Body Structural Components Precision Dimensional Measurement Devices Concrete Reinforcement in Buildings Bridge Construction Components Automotive Body Components Components for Automotive Engines Utility Poles Production Tooling