FR2777930A1 - Locating sheaths for prestressed cables in reinforced concrete, particularly applicable to deck sections of bridges - Google Patents

Abstract

The shuttering of a bridge deck section consists of panels (7) which enclose a region to be filled with concrete. Prestressed reinforcing cables and their sheaths are held in position by holes (4) in rigid plates (3) made from concrete and metallic fibres or from steel. The plates (3) are directly fabricated by design software and numerically controlled machine tools and located to the shuttering by concrete wedges (5) and steel claws (6)

Description

Device for positioning prestressed cable ducts in the

  formwork of a concrete structure, in particular in the formwork of an apron of

  bridge, and method for manufacturing the device.

  The invention relates to the positioning of prestressing cable sheaths in the formwork of a concrete structure, and finds a

  particularly interesting application in bridge decks.

  The installation of longitudinal prestressing cables in a concrete bridge deck involves positioning, inside the formwork, sheaths in which the cables will be threaded, generally

  after pouring the concrete into the formwork.

  The common technique for achieving this positioning is to have, from place to place, in cross sections of the deck formwork, vertical grids to which are fixed rings which

  determine passages for the sheaths.

  This system has many drawbacks: - at the study level, the support grids require a manual or semi-manual drawing, long, tedious, and with significant risk of error, given the number of parts drawn (approximately 4,000

  supports for 1,000 linear meters of deck).

  - at the manufacturing level, we encounter the same long working hours difficulties, risk of errors, which have repercussions

  on time, quality and cost.

  Figure 1 of the accompanying drawing is a partial view of a vertical section in the formwork of a segment of a bridge deck at the location of a sheath support constituted by a grid (1) to which has been fixed of

  rings (2) at the locations determined for the positioning of the sheaths.

  The means have not been shown in the figure (welds, staples, etc.) used to secure the rings and the support grid, nor the means

  necessary to hold the grid in place in the segment formwork.

  According to the present invention, the grids and the rings are replaced by rigid plates which have perforations for the passage and the

duct positioning.

  The design of these plates, in connection with the calculation of the structure of the deck, is automatic. According to the invention, the plates are produced using calculation software on a numerically controlled machine tool, calculation software the output of which is transmitted by the design office by various computer means (files, diskettes, CDR, Internet, etc.). ), without drawings or intermediate calculations. Preferably, the plates have an outline which matches that of the formwork with a small interval, which allows the software to easily and automatically deduce the shape and dimensions of a plate from the form and dimensions of the formwork to the space provided for the plate in the formwork; they are blocked vertically and laterally against the formwork by concrete wedges and are blocked in the longitudinal direction

  formwork by steel pins.

  Figure 2 of the accompanying drawing is a partial view of a vertical section of the formwork of a bridge deck segment which shows inside this

  formwork, a plate (3) provided with perforations (4) according to the invention.

  This plate (3) with its perforations (4) replaces the grid (1) with its

  rings (2) used in the prior art.

  Also shown in Figure 2 wedges 5 and staples 6

  which hold the plate in position in the formwork.

  The formwork itself consists of panels (7), in a manner known per se, the invention not relating to the formwork itself. The passive steels also used in the

formwork, in a manner known per se.

  In a typical embodiment, the plates have a thickness of 1 to 3 cm

  and a weight that allows them to be handled manually.

  Preferably, the plates are made of a material based on concrete and / or steel to ensure the continuity and homogeneity of the material.

constituting the work.

  For example, the plates consist of a cement matrix

  hardened with metallic fibers.

  Examples of an ultra high resistance concrete consisting of a cement matrix comprising metallic fibers are described in the publication WO - A - 95/01316 but the invention is not limited to these

examples of fiber concrete.

  Alternatively, steel plates can be used.

  Advantageously, the plates have other perforations to allow the concrete to pass when the concrete is poured into the formwork of the deck. Ultimately in its most advantageous embodiment, the invention provides the following advantages over the prior art: - A rigid and non-deformable support system - A system which precisely positions the sheaths and which

  rigidly holds during concreting.

  - A fully automatic drawing conforming to the calculation scheme

of the structure.

  - Faithful and rapid transmission of data from the Design Office to the manufacturing workshops by computer means (files,

  diskettes, CDR, Internet ...), without calculations or intermediate drawings.

  - Fast and safe manufacturing by numerically controlled machine tools. - Use of a material based on concrete and / or steel, which

  preserves the continuity and homogeneity of the structure.

  - A positioning "imposed" therefore safe, the system in the formwork (vertical and lateral rigid blocking of the plate against the formwork). This

  lack of "flexibility" is a guarantee of quality.

  - A limited weight which allows manual handling of the part.

  - Easy visual control of the position of the part in the formwork.

  FIG. 3 represents, by way of example, a cross section of a segment constituting a longitudinal fraction of the deck of a bridge and the locations of the support plates of the invention have been circled in (10) in this figure. wall connection areas

  horizontal A, A 'and oblique walls B, B' of the segment.

  The invention is not limited to the embodiments or to the applications which have been described, it being specified however that the application to the positioning of the cable sheaths of longitudinal prestressing of a bridge deck is an application for which the invention has been specially designed.

Claims (9)

  1- Device for positioning in the formwork (7) of a concrete structure, before the concrete is poured into the formwork, sheaths intended to receive, preferably after the concrete has been poured, cables serving to prestress the structure, this device comprising elements to be installed from place to place in cross sections of the formwork and means for holding these elements in place, characterized in that these elements are rigid plates (3) which have perforations (4) for the   passage and positioning of the ducts.   2- Device according to claim 1, wherein the plates (3) have a shape which marries with a small interval the shape of the section cross section of the formwork (7).   3- Device according to claim 2 and which comprises shims (5) for locking the plates vertically and laterally against the   formwork and pins (6) to block them longitudinally.   4- Device according to one of claims 1 to 3 including the plates (3)   have a thickness of 1 to 3 cm and a weight that allows them handle manually.   - Device according to one of the preceding claims, the   plates (3) are made of a material based on concrete and / or steel to ensure the continuity and homogeneity of the material constituting the work.   6- Device according to claim 5, the plates (3) consist of a hardened cement matrix comprising metallic fibers.   7- Device according to claim 5 whose plates (3) are made of steel.   8- Device according to one of the preceding claims, the   plates (3) have other perforations to let the   concrete when pouring concrete from the structure into the formwork.   9- Process for manufacturing the perforated plates of a device according to   one of claims 1 to 8, characterized in that the   plates on a numerically controlled machine tool using calculation software, the output of which was transmitted to the machine without drawings or intermediate calculations.   1 0-Application of a device according to one of claims 1 to 8 and / or   of a method according to claim 9, in positioning the sheaths   longitudinal prestressing cables of a bridge deck.   11- Application according to claim 10 for positioning the sheaths   in the formwork of a segment constituting the deck.