Classifications

• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
  • E04C3/00—Structural elongated elements designed for load-supporting
  • E04C3/02—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces
  • E04C3/12—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of wood, e.g. with reinforcements, with tensioning members
  • E04C3/18—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of wood, e.g. with reinforcements, with tensioning members with metal or other reinforcements or tensioning members
  • E04C3/185—Synthetic reinforcements
• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
  • E04C3/00—Structural elongated elements designed for load-supporting
  • E04C3/02—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces
  • E04C3/12—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of wood, e.g. with reinforcements, with tensioning members
  • E04C3/18—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of wood, e.g. with reinforcements, with tensioning members with metal or other reinforcements or tensioning members

Definitions

• the object of the present invention is that of providing prestressed structures which comprise glued laminated timber beams and tendons of the "external" type and which have considerable transverse stability.
• two or more glued laminated timber beams, two terminal elements, one or more deviating elements and one or more tendons are made; said glued laminated timber beams, said terminal elements, said one or more deviating elements and said one or more tendons, from the start, are designed and made so as to produce the prestressed structure;
• a primary structure is assembled, applying said terminal elements and said one or more deviating elements to said glued laminated timber beams; said terminal elements are applied to the ends of said glued laminated timber beams; at the end of said second step of the method, said glued laminated timber beams are spaced from one another and are connected together by means of said terminal elements and said one or more deviating elements;
• said one or more tendons are arranged in position, in contact with said one or more deviating elements and with said terminal elements; at the location of said one or more deviating elements, the path followed by said one or more tendons changes direction; each of said one or more tendons is located outside the cross-section of said glued laminated timber beams and is positioned, at least partly, between said glued laminated timber beams; - fourth step; tensioning of said one or more tendons is performed, said tendons being then anchored, at their ends, to said terminal elements; said tensioning is performed using means which act against said glued laminated timber beams through the terminal element with which said means are in contact; each of said one or more tendons, during said tensioning, being subject to a tensile normal force, lengthens, sliding longitudinally with respect to said primary structure; following said tensioning, said one or more tendons, at the location of said terminal elements and of said one or more deviating elements, apply to said primary structure a system of forces which produces bending in said primary structure
• a primary structure comprising two or more glued laminated timber beams, two terminal elements applied to the ends of said glued laminated timber beams and one or more deviating elements applied to said glued laminated timber beams; said glued laminated timber beams are spaced from one another and are connected together by means of said terminal elements and said one or more deviating elements;
• each of said one or more tendons has its ends anchored to said terminal elements and is in contact with said one or more deviating elements; at the location of said one or more deviating elements the path followed by said one or more tendons changes direction; each of said one or more tendons is located outside the cross-section of said glued laminated timber beams and is positioned, at least partly, between said glued laminated timber beams; said one or more tendons, at the location of said terminal elements and of said one or more deviating elements, apply to said primary structure forces which produce bending in said primary structure, inducing in said primary structure a compressive normal force; said forces are due to the tensioning of said one or more tendons, performed during the construction of the prestressed structure, and to the loads applied to said prestressed structure; in particular, as a result of said tensioning, said one or more tendons, at the location of said terminal elements and of said one or more deviating elements, apply to said primary structure a system of forces which produces bending in said primary structure, induc
• FIG. 1 shows a partly longitudinal view and partly longitudinally sectioned view of a prestressed structure obtained according to the present invention
• FIG. 2 shows, on a scale larger than that of Figure 1, the cross-section along the line I-I of Figure 1 ;
• - Figure 3 shows, on the same scale as Figure 2, a detail of Figure 1 ;
• - Figure 4 shows, on the same scale as Figure 2, the view, from one of the two ends, of the prestressed structure according to Figure 1 ;
• FIG. 5 shows a partly longitudinal view and partly longitudinally sectioned view of a prestressed structure obtained in accordance with the present invention, according to a further embodiment
• the prestressed structure 1 which below is described when in use, is supported at its ends; more precisely, it is constrained with two external constraints 2, each of which is schematically represented as a hinge, and with two external constraints 3, each of which is schematically represented as a horizontally rolling support.
• the prestressed structure 1 which (during use) is subject to vertical concentrated loads 4 comprises in combination:
• a primary structure 5 comprising two glued laminated timber beams (glulam beams) 5a, two terminal elements 5b applied to the ends of the two glued laminated timber beams 5a and five deviating elements 5c, 5d, 5e applied to the two glued laminated timber beams 5 a;
• the glued laminated timber beams 5 a are spaced from each other and are connected together by means of the terminal elements 5b and of the deviating elements 5c, 5d, 5e;
• the glued laminated timber beams 5a which have a straight and horizontal axis, have a rectangular cross-section;
• the glued laminated timber beams 5a are identical and parallel to each other;
• each of the two glued laminated timber beams 5a consists of the set of two glued laminated timber beams 6 which are identical to each other and have a rectangular cross-section and which are placed in contact with each other and joined together;
• the expression "positioned partly between the two glued laminated timber beams 5a” is understood as meaning "positioned partly in the space between the two glued laminated timber beams 5a”;
• the tendons 7, at the location of the terminal elements 5b and of the deviating elements 5c, 5d, 5e, apply to the primary structure 5 forces which produce bending in the primary structure 5, inducing in the said primary structure 5 a compressive normal force;
• the abovementioned forces are due to the tensioning of the tendons 7, performed during the construction of the prestressed structure 1 , and to the loads 4 which are applied, during use, to the prestressed structure 1 itself; in particular, as a result of the abovementioned tensioning, the tendons 7, at the location of the terminal elements 5b and of the deviating elements 5c, 5d, 5e, apply to the primary structure 5 a system of forces which produces (upwards) bending in the primary structure 5,
• Each tendon 7 consists of a high-strength steel strand (steel, that is, having for example a tensile strength greater than 1750 N/mm 2 ) contained in its own sheath of synthetic material inside which the strand itself is able to slide.
• Each of the two terminal elements 5b consists of a set of metal elements which comprises two end-pieces 8, each of which is in contact with one of the two glued laminated timber beams 5a, two cross-pieces 9a, 9b which are joined to the two end-pieces 8 and an anchoring element 10 which is joined to the cross-piece 9a; the tendons 7 are anchored at the location of the anchoring elements 10 by means of wedges.
• the end-pieces, as well as the end cross-sections of the glued laminated timber beams are substantially perpendicular not to the axes of the said glued laminated timber beams, but to the axes of the tendons which are anchored at the location of the terminal element itself. It is pointed out that, according to another embodiment, not shown in the figures, the end- pieces may have dimensions which are smaller than the height of the cross-section of the glued laminated timber beams.
• Each of the five deviating elements 5c, 5d, 5e consists of a set of metal elements which comprises elements placed in contact with the glued laminated timber beams 5a and suitably shaped elements which, placed in contact with the tendons 7, deviate the path of the said tendons 7. It is pointed out that, in the prestressed structure 1, the axes of the deviating elements 5c, 5d, 5e are vertical and are perpendicular to the axes of the two glued laminated timber beams 5a; according to a variation, not shown in the figures, the axis of each deviating element is directed along the bisector of the angle formed between the two sections of each tendon located respectively on either side of the said deviating element.
• the method, according to the present invention, for the construction of the prestressed structure 1 comprising the following steps: - first step: the two glued laminated timber beams 5a, the two terminal elements 5b, the five deviating elements 5c, 5d, 5e and the eight tendons 7 are made; the two glued laminated timber beams 5a, the terminal elements 5b, the deviating elements 5c, 5d, 5e and the tendons 7, from the start, are designed and made so as to produce the prestressed structure 1 ;
• the primary structure 5 is assembled on-site, applying the terminal elements 5b and the deviating elements 5c, 5d, 5e to the two glued laminated timber beams 5a; the terminal elements 5b are applied to the ends of the glued laminated timber beams 5a; at the end of the second step of the method, the two glued laminated timber beams 5a are spaced from each other and are connected together by means of the terminal elements 5b and the deviating elements 5c, 5d, 5e; - third step: the tendons 7 are arranged in position, in contact with the deviating elements 5c, 5d, 5e and with the terminal elements 5b; at the location of the deviating elements 5c, 5d, 5e the path followed by the tendons 7 changes direction; each tendon 7 is located outside the cross-section of the two glued laminated timber beams 5a and is positioned, partly, between the said two glued laminated timber beams 5a; it is pointed out that the tendons 7 are inserted inside the deviating elements 5
• tensioning of the tendons 7 is performed, said tendons being then anchored, at their ends, to the terminal elements 5b; the abovementioned tensioning is performed using a hydraulic jack (not shown in the figures) which acts against the two glued laminated timber beams 5 a through the terminal element 5b with which said hydraulic jack is in contact; each tendon 7, during the abovementioned tensioning operation, being subject to a tensile normal force, lengthens, sliding longitudinally with respect to the primary structure 5; following the abovementioned tensioning, the tendons 7, at the location of the terminal elements 5b and of the deviating elements 5c, 5d, 5e, apply to the primary structure 5 a system of forces which produces bending in the primary structure 5, inducing in the said primary structure 5 a compressive normal force; the fourth step of the method is completed before the prestressed structure 1 is put into service.
• the hydraulic jack which is positioned at the location of the terminal element 5b close to the external constraints 3, tensions, in accordance with a suitable tensioning sequence, the tendons 7, acting, by means of the said terminal element 5b (close to the external constraints 3), against the two glued laminated timber beams 5a; the ends of the tendons 7 close to the external constraints 2 have been previously anchored, by means of the associated wedges, to the terminal element 5b close to the said external constraints 2; during the tensioning operations each tendon 7 slides, except for its end close to the external constraints 2, with respect to the primary structure 5, substantially (the term “substantially” is used since frictional forces are present) free to slide along its whole length inside its sheath.
• FIGS 5 and 6 illustrate a prestressed structure 20 obtained according to the present invention, which is supported at its ends on two external constraints 21, each of which is schematically represented by a hinge, and on two external constraints 22, each of which is schematically represented by a horizontally rolling support.
• the prestressed structure 20, which is described below during use, is subject to vertical concentrated loads 23 and comprises in combination:
• a primary structure 24 comprising two glued laminated timber beams 24a with a rectangular cross-section, two metal terminal elements 24b which are applied to the ends of the two glued laminated timber beams 24a, two metal deviating elements 24c applied to the two glued laminated timber beams 24a, and metal connection elements 24d applied to the two glued laminated timber beams 24a;
• the two glued laminated timber beams 24a are spaced from each other and are connected together by means of the terminal elements 24b, deviating elements 24c and connection elements 24d;
• the two glued laminated timber beams 24a have a straight and horizontal axis;
• each tendon 25 consists of a high-strength steel strand contained inside a sheath of synthetic material inside which the strand itself is able to slide.
• connection elements may be made of glued laminated timber.
• the behaviour of the prestressed structure 20 and the method for the construction thereof are technically equivalent to those already described for the prestressed structure 1. It is pointed out that, during the first step of the method, the connection elements 24d are also made, which elements, during the second step of the method, are applied to the two glued laminated timber beams 24a.
• the method according to the present invention may sometimes comprise a fifth step, following the first four steps, during which relative displacements, permitted during the fourth step of the method, between the one or more tendons and the primary structure are permanently prevented; the abovementioned possible fifth step of the method is completed before the prestressed structure is put into service.
• the possible fifth step of the method may be useful for optimizing the behaviour in the "ultimate state" of the prestressed structure.
• some of the permanent loads or all the permanent loads may be applied to the said structure before the start of the fourth step of the method.
• each of the two or more glued laminated timber beams comprised in the primary structure may consist of the set of two (as in the case of each of the glued laminated timber beams 5a) or more glued laminated timber beams, with a rectangular cross-section, which are arranged in contact with one another and joined together so as to form a single beam.
• each of the two or more glued laminated timber beams included in the primary structure may have a straight axis or curved axis or axis formed as a broken line (with possible connecting radii).
• the two or more glued laminated timber beams may be of the solid-wall type or truss type or Vierendeel type or other types; in the case where the glued laminated timber beams are of the solid-wall type, each of them may have (for example) a rectangular cross-section or T-shaped cross-section or I-shaped cross-section with the upper flange the same as the lower flange or different from the lower flange.
• each of the two or more glued laminated timber beams may have a constant cross-section or a variable cross-section.
• each of the two or more glued laminated timber beams may comprise two or more segments joined together and located, in the longitudinal direction, one after another; these segments are assembled on-site before implementing the third step of the method; it is pointed out that, generally, the stress states at the location of the joints between the abovementioned segments may be improved as a result of the prestressing. It is possible to have a prestressed structure obtained according to the present invention (this embodiment is not illustrated in the figures) in which each tendon is entirely positioned between the glued laminated timber beams (i.e. is entirely positioned in the space between the glued laminated timber beams).
• each of the abovementioned groups of strands is contained in a tubular housing element which is made of synthetic material and inside which a filling material has also been introduced; it is pointed out that each strand may be greased and contained inside its own sheath made of synthetic material such that sliding of each strand inside its sheath is permitted. It is possible to have a prestressed structure obtained according to the present invention in which a single deviating element is present.
• a prestressed structure obtained according to the present invention in which more than two glued laminated timber beams are present; these glued laminated timber beams are spaced from each other and are connected together by means of the terminal elements and the one or more deviating elements; it is pointed out that connection elements applied to the abovementioned glued laminated timber beams may also be present.
• the tendons consist, for example, of strands or bars or wires; it is pointed out that the tendons may be made of steel or may be made using synthetic materials or composite materials or also other suitable materials.
• the primary structure also comprises retaining elements which connect the primary structure and the tendons at points where the path followed by the tendons does not change direction.
• the present invention it is possible to produce, in addition to prestressed structures externally constrained in an isostatic manner, also prestressed structure externally constrained in a hyperstatic manner.
• An advantage of the present invention consists in the fact that, using a prestressed structure obtained according to the present invention instead of an "equivalent" traditional glued laminated timber bam, it is possible to reduce the quantity of glued laminated timber to be used.

Landscapes

• Engineering & Computer Science (AREA)
• Architecture (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Civil Engineering (AREA)
• Structural Engineering (AREA)
• Rod-Shaped Construction Members (AREA)
• Buildings Adapted To Withstand Abnormal External Influences (AREA)

Applications Claiming Priority (1)

Publications (3)

Family

ID=11333135

Family Applications (1)

Country Status (4)

Families Citing this family (8)

Family Cites Families (5)

• 1999
  • 1999-12-07 DE DE69939557T patent/DE69939557D1/de not_active Expired - Lifetime
  • 1999-12-07 WO PCT/IT1999/000404 patent/WO2001042584A1/en active IP Right Grant
  • 1999-12-07 EP EP99959683A patent/EP1235964B9/de not_active Expired - Lifetime
  • 1999-12-07 AT AT99959683T patent/ATE408045T1/de active

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events