STRENGTHENING OF REINFORCED AND PRESTRESSED BEAMS

In beams of reinforced and prestressed concrete, loads are carried by the structural interaction of the concrete acting in compression, and the steel reinforcement or the steel prestressed tendons acting in tension. It may on occasion be desirable or necessary to increase the flexural capacity of an existing beam. This may be due to a change in the use of a building whereby additional load is to be carried by the beam, or it may be due to the beam having been damaged in some way. The author considers that fire is the most frequent cause of damage of such beams, and the resulting reduction in strength is discussed. In this article a new and positive method of strengthening is described which the author considers may be appropriate in some circumstances. The proposed method is illustrated by reference to a reinforced concrete beam from which the concrete cover to the longitudinal reinforcement at the bottom of the beam has been spalled away or has been removed. To strengthen this beam, a steel channel is fixed to the bottom of the beam in such a way that the web of the channel forms the new soffit of the beam. The channel is held in position by bolts passing through holes drilled in the flanges of the steel channel and in the web of the concrete beam above the longitudinal reinforcement. The gaps between the steel channel and the concrete and also between the bolts and the concrete are then filled with a suitable grout material. This method is only considered suitable where there exists in the beam shear reinforcement in the form of stirrups, which would resist any downward forces which may be conveyed to the beam through the bolts by the dowelling action of the channel. A new structural material is also described, known as composite reinforced concrete, which is a combination of composite construction and reinforced concrete. This material, it has been suggested, retains the material advantages of reinforced concrete with the constructional advantages of steelwork. /TRRL/

  • Availability:
  • Corporate Authors:

    Cement and Concrete Association

    52 Grosvenor Gardens
    London SW1W 0AQ,   England 
  • Authors:
    • Taylor, R
  • Publication Date: 1976-12

Media Info

  • Features: Figures; Photos; References;
  • Pagination: p. 28-29
  • Serial:
    • CONCRETE
    • Volume: 10
    • Issue Number: 12
    • Publisher: THE CONCRETE SOCIETY
    • ISSN: 0010-5317

Subject/Index Terms

Filing Info

  • Accession Number: 00152838
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Jul 2 1977 12:00AM