Pre-compression system for pre-compressing a structure
A pre-compression system for pre-compressing a concrete structure, the system comprising a first tubular element ( 31 ) that is expandable in a longitudinal direction and interposed between the first and the second head ( 21, 22 ). The first tubular element ( 31 ) is movable between a longitudinally elongated configuration, in which a pressurized fluid is placed inside the first tubular element ( 31 ), and a contracted configuration, in which said fluid is at least partly removed, the passage from the elongated configuration to the contracted configuration bringing about a compression on the concrete which at least partly envelops the first tubular element ( 31 ).
1. A pre-compression system for pre-compressing a structure, which, in turn, comprises a construction material, said pre-compression system comprising a first tubular element ( 31 ) that is expandable in a longitudinal direction, said first tubular element ( 31 ) being movable between a longitudinally elongated configuration, in which a pressurized fluid is placed inside the first tubular element ( 31 ), and a contracted configuration, in which said fluid is at least partly removed, a passage from the longitudinally elongated configuration to the contracted configuration bringing about a compression on the construction material which at least partly envelops the first tubular element ( 31 ); wherein:
a) said first tubular element ( 31 ) comprises a composite material the composite material comprises a matrix and fibres located in the matrix, said fibres comprising fibres that are wrapped around a longitudinal axis and that extend helically; or -the first tubular element ( 31 ) comprises fibres, said fibres comprising impregnated fibres helically wrapped around the longitudinal axis;
b) the fibres also comprise longitudinal fibres which are responsible for a contraction of the tubular element which determines the passage from the longitudinally elongated configuration to the contracted configuration thus defining the pre-compression of the construction material; the first tubular element ( 31 ) has a resistance to radial expansion and a resistance to longitudinal elongation, wherein the resistance to radial expansion is greater than the resistance to longitudinal elongation.
2. The pre-compression system according to claim 1 , characterized in that the pre-compression system comprises a first and a second compression head ( 21 , 22 ) for compressing the construction material interposed between them, said compression on the construction material being performed by the first and the second head ( 21 , 22 ) in the contracted configuration of the first tubular element ( 31 ).
3. The pre-compression system according to claim 2 , characterized in that the pre-compression system comprises a second expandable tubular element ( 32 ) that extends from the first compression head ( 21 ) to a third compression head, said first and said second tubular element ( 31 , 32 ) extending along different directions.
4. A method for pre-compressing a structure comprising a construction material, by means of the pre-compression system according to claim 1 , and comprising steps of: -pressurizing an area ( 310 ) inside the first tubular element ( 31 ); -applying the construction material around said first tubular element ( 31 ); -waiting for at least partial curing of the construction material; -reducing pressure in the area ( 310 ) inside the first tubular element ( 31 ), thus bringing about a longitudinal contraction of the first tubular element ( 31 ) and a pre-compression of the construction material that envelops the first tubular element ( 31 ).
5. The method according to claim 4 , wherein the step of pressurizing the inside area ( 310 ) comprises introducing a pressurized liquid inside the first tubular element ( 31 ) by pumping.
6. The pre-compression system according to claim 1 , characterized in that a ratio of a weight or a strength of the fibres wrapped around a longitudinal axis of the first tubular element ( 31 ) to a weight or a strength of the longitudinal fibres is about 2 to 1.