Static structures (e.g. – buildings) – With component having discrete prestressing means – Beam – girder – or truss construction
Patent
1994-10-24
1997-04-08
Friedman, Carl D.
Static structures (e.g., buildings)
With component having discrete prestressing means
Beam, girder, or truss construction
522236, 5222313, 5222314, 527241, 527245, 527302, 527317, 527372, 527374, 527381, 5274519, E04C 326, E04C 3293
Patent
active
056176856
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a method for increasing the shear strength of an elongated or a substantially two-dimensional construction structure serving as a support; further a method for increasing the shear strength of a construction structure with an elongated, laminar reinforcement affixed from the outside to the structure to reinforce it; further a method for increasing the shear strength of an elongated or two-dimensional concrete construction structure reinforced on its inside with steel means; applicability of the above methods; apparatus to increase the shear strength of an elongated or substantially two-dimensional bearing construction structure, a bearing construction structure such as of steel reinforced concrete; with apparatus and a procedure to pre-stress a fabric-like hose or tube.
For many years research and development has been applied to retrofitting reinforced concrete by applying additional reinforcement(s). The beginnings of this technique are described in J. Bresson's "Nouvelles Recherches Et Applications Concernant l'Utilisation des Collages Dans Les Structures", Beton Plaque, Annales ITBTP 278 (1971), Serie Beton, Beton Arme Nr. 116. The description goes back to the sixties. Bresson's work especially covered the requirements of compound stresses in the field of anchoring bonded steel laminations.
Accordingly, it has been feasible for two decades to strengthen extant reinforced concrete structures, such as bridges, floor and paving slabs, longitudinal girders and the like, by subsequently bonding steel laminations.
The strengthening of concrete structures by bonding steel laminations using for example epoxy-resin adhesives, now may well be considered a standard technique.
Strengthening may be required for a number of reasons: structures such as uprights or struts or reducing their support functions;
Post-facto strengthening by means of bonded steel laminations has been found effective on numerous structures and, illustratively, is described in the following literature: Ladner, M. & Weder, Ch., "Geklebte Bewehrung Im Stahlbetonbau", EMPA Duendorf, Report No. 206 (1981); "Verstaerkung Von Tragkonstruktionen Mit Geklebter Armierung", Schweiz. Bauzeitung, Special print of 92nd year, Issue 19 (1974); "Die Sanierung Der Gizenenbruecke Uuber Die Muota", Schweiz. Ingenieur & Architekt, Special print from Issue 41 (1980).
However, such strengthening procedures incur a number of drawbacks. Steel laminations can be delivered only in short lengths and, therefore, only short laminations can be used. Accordingly, the laminations must butt and potential weak spots must be incurred. The steel laminations are heavy and their handling at the construction site may become quite difficult if the pertinent structures are high or accessible only with difficulty. As regards steel, even when carefully treated against corrosion, there is danger of the laminations under-rusting or that there will be corrosion at the interface of concrete and steel which may lead to detachment and hence to loss of the strengthening.
Accordingly, it was already suggested by U. Meier in "Brueckensanierung Mit Hochleistungs-Faserverbundwerkstoffen", Material+Technik, 15th year, Issue 4 (1987) and further in H. P. Kaiser's dissertation DISS. ETH. No. 8918, ETH ZURICH (1989) to replace the steel laminations by carbon-fiber reinforced epoxy-resin laminations. Laminations made of such material evince low bulk density, high strength, excellent fatigue properties and outstanding corrosion resistance. Accordingly, it is possible to use thin, lightweight carbon-fiber reinforced plastic laminations in lieu of heavy steel ones. The plastic ones, furthermore, may be moved in a nearly endless, rolled-up manner to the construction site. Practical tests have shown that carbon-fiber laminations 0.5 mm thick evince a tensile strength corresponding to the yield point of a 3 mm thick FE360 steel lamination.
The present invention essentially starts from the ETH dissertation and in part represents a further development of the technical solution d
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Deuring Martin
Meier Heinz
Meier Urs
Eidgenoessische Materialpruefungs- Und Forschungsanstalt Empa
Friedman Carl D.
Saladino Laura A.
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