Expansion joint for bridge structure

Abstract: An expansion joint for bridge structure (1) comprising a layer of composite (5) consisted of rubber grains (6) as the aggregates and synthetic resins (7) with lower modulus of elasticity as the binder.

Description: Field of the Invention This invention relates to an expansion joint for bridges over rivers, valleys or roads, more particularly to a type called a seamless expansion joint, and to a composite material for use in forming the composite layer of such a joint. Prior Art Conventional expansion joints include a finger joint which comprises a pair of teeth-like steel combs arranged between a pair of floor slabs opposite to each other, with each one end thereof fixed to respective opposite ends of the floor slabs, and a rubber joint which comprises a rubber seal interconnecting the opposite ends of the floor slabs to cover the clearance therebetween, and these two kinds of expansion joints have been dominantly used. However, these two kinds of expansion joints involve drawbacks due to discontinuity of pavement surfaces that provides vehicles with an unfavorable running surface and generates uncomfortable noise. Accordingly, in order to overcome these drawbacks, there has recently been proposed and practically used an expansion joint that is called a seamless expansion joint. A main feature of this expansion joint exsists in that a composite comprising a binder and natural aggregates is laid in recessed portions of pavements, prepared over adjacent ends of a pair of floor slabs, the upper surface of the composite layer being made even with those of the remaining portions of the pavements (cf. for example, JP-A-61-191703, and GB-A-2218437, which discloses an expansion joint according to the precharacterising part of Claim 1. The seamless expansion joint provides a favorable influence upon a vehicle's running, since the composite layer is even with the surface of pavements, and generates little noise since there is no gap in the running surface over the clearance. Usually, the seamless expansion joint employs a composite consisting of natural aggregates and a rubber asphalt as a binder, and the role of compression resistance thereof against vehicle load is allotted to natural aggregates embedded in plastic materials, while the elasticity against the floor slabs is played by the binder. However, since the rubber asphalt itself has poor elasticity and a plastic nature, the layer of the composite cannot resist vehicles of heavy load, resulting in gradual deformation which ruins the flatness of the road surface. On the other hand, since the natural aggregates lack elasticity, the elasticity of the rubber asphalt alone does not provide the road structure with sufficient elasticity. The present invention is aimed at provision of an expansion joint that is capable of maintaining the flatness of the road surface and also fully following the expansive and contractive behavior of the floor slabs, with the above problems eliminated. For attaining the above object, in the expansion joint for a bridge structure according to the present invention, the layer of composite material has the features of the characterising part of Claim 1. US-A-4871809 discloses an expansion joint composition for a railway crossing comprising a polymeric aggregate in a polymeric binder of lower elasticity than the aggregate. There is disclosed a high ratio of aggregate to binder (greater than 6 to 1 by weight) and a small granular size for the aggregate (0.001 mm to 3 mm). The expansion joint according to the present invention is capable of keeping the flatness of the road surface, with the elastic nature of the binder providing both resisting and restoring forces against the vehicle load, and also of following large expansion and contraction of the floor slabs, owing to both the elasticity of the binder and the deformability of the aggregate. Fig. 1 is a sectional view showing rebates in a pavement layer over adjacent ends of floor slabs, caused by cutting away portions of the pavement layer; Fig. 2 is a sectional view similar to Fig.1, but showing an expansion joint according to the present invention in the rebates; and Fig. 3 is an enlarged sectional view of a portion A in Fig. 2. Now, with reference to the drawings, an expansion joint of the present invention will be described in detail. Referring first to Fig. 1, rebated, or notched portions 2, 2 are respectively prepared by partly cutting off end portions of pavement layers 3, 3 over floor slabs 1, 1, which are adjacent to each other, with an idle space, or clearance 10 therebetween. A water proof member 8 is preferably provided in the clearance 10. Turning now to Figs. 2 and 3, a primer 9 is preferably painted on the surface of the notched portions 2, 2, and a cover member 4 made of an aluminium plate or the like is laid over the adjacent ends of the adjacent floor slabs 1, 1 to cover them. The cover member 4 may be omitted if the composite layer 5 does not happen to drop down into the clearance 10 when laying the composite layer 5 on the floor slabs 1,1. Then, the composite layer 5 comprising an aggregate 6 and a binder 7 is placed in the notched portions 2, 2 such that the upper surface thereof may be made even with that of the pavement layer 3, 3. As an example, the blending rate and performance of a composite not strictly falling within the scope of the claims are as follows: Blending rate epoxy resins 1 (by weight) rubber grains 2.5 (by weight) (hardness 40°-60° by Shore hardness tester and grain sizes 5 mm - 1 mm) Performance compressive strength (kg/cm²) 20 modulus of compression elasticity (kg/cm²) 60 bending strength (kg/cm²) 14 deflection (mm) 60 In this connection, the deflection of a conventional composite is 3 mm, with the same volume and blending rate of 1 rubber asphalt (by weight) and 7 natural aggregates (by weight). In comparison of these deflections, it will be apparent that the deformability of the present composite employing the rubber grains as the aggregates is excellent. The composite may employ as the binder another synthetic resin of low elastic modulus, specifically polyurethane resin, or polybutadiene resin, which can be applied at normal temperature and possesses sufficient adhesive strength. The aggregate includes ethylene propylene terpolymers (EPDM), nitrile-butadiene rubbers (NBR), or styrene-butadiene rubbers (SBR) and the grain size ranges from 5 mm to 10 mm. If required, natural aggregates may be blended therewith. Comprised as above, the expansion joint according to the present invention possesses the following effects. The elastic nature of the binder resists the vehicle load and restores even though the composite layer undergoes deformation, while the extension characteristic of the aggregate provides sufficient shrinkage. Further, the seamless expansion joint also provides vehicles with a good running surface and generates little noise as in the case of conventional seamless joints.

Claims: An expansion joint of a bridge structure having adjacent floor slabs (1) with a clearance (10) between the slabs for compensating for possible expansion and contraction of the slabs, a pavement layer (3) laid on the floor slabs, with a rebate (2) formed in the pavement layer over each of the adjacent ends of the floor slabs (1) to form a recess over the clearance (10), the recess containing a composite layer (5) laid on the slabs so that the upper surface of the composite layer is even with that of the pavement layers characterised in that the composite layer consists of an aggregate comprising grains of ethylene propylene terpolymer, nitrile-butadiene rubber, or styrene-butadiene rubber, having a grain size 5 mm to 10 mm, a binder comprising an epoxy, polyurethane, or polybutadiene resin, the binder having a lower modulus of elasticity, after curing, than the aggregate. An expansion joint according to Claim 1, wherein the binder is provided in a ratio of binder to aggregate of 1:2.5. A composite material (5) for use in forming the composite layer of an expansion joint according to Claim 1, the material comprising an aggregate (6) comprising grains of ethylene propylene terpolymer, nitrile-butadiene rubber, or styrene-butadiene rubber, having a grain size 5 mm to 10 mm, and a binder (7) comprising an epoxy, polyurethane, or polybutadiene resin, the binder having a lower modulus of elasticity, after curing, than the aggregate.

Inventors: AKIRA UEDA, AKIRA, UEDA
Applicants: SHO BOND CORP, SHO-BOND CORPORATION
Application year: 1990
Main classification: E01D19
IPC codes: E01D19, E01C11