Broken-spiral stirrup and method for implementing the reinforcement of concrete structures

Abstract

Stirrup structure ( 1 ) shaped like a broken spiral, extending according to its longitudinal axis (A), constituted by a sequence of tracts substantially perpendicular ( 3 ) and substantially oblique ( 2 ) with respect to the longitudinal axis, forming winding configurations, with the oblique tracts ( 2 ) tilted two by two in directions different between them to implement the spiral pitch (D) and positioned on faced surfaces, with which implementing the method consisting in handling the single stirrup structure ( 1 ) in an axially compacted state, in positioning it in the site on a resting base or inside a form, in positioning inside thereof the reinforcement longitudinal members, in releasing the stirrup structure ( 1 ) from the ties in order to allow it extending elastically, then in fastening it with anchoring elements to the reinforcement longitudinal members.

1 . A broken-spiral stirrup for the reinforcement of concrete structures, comprising a stirrup structure ( 1 ) with extension according to its longitudinal axis (A), implemented with a metallic bar, constituted by a sequence of tracts substantially perpendicular ( 3 ) and substantially oblique ( 2 ) with respect to said longitudinal axis (A) and forming winding configurations with polygonal projection onto a plane substantially perpendicular to said longitudinal axis (A), characterized in that said oblique tracts ( 2 ) are tilted two by two in directions different between them to implement the spiral pitch and they are positioned at faced surfaces.  
   
   
       2 . The stirrup according to  claim 1 , characterized in that said oblique tracts ( 2 ) have a tilting angle and a length so as to make the distance between the projections onto the axis of the stirrup structure ( 1 ) itself of the beginning and of the end of each oblique tract ( 2 ) equal substantially to half the stirrup pitch.  
   
   
       3 . The stirrup according to  claim 1 , characterized in that the stirrup structure ( 1 ) shaped like a broken spiral comprises at least at one end a plane polygonal winding ( 4 ) substantially orthogonal to said longitudinal axis (A) according thereto the stirrup structure ( 1 ) itself develops.  
   
   
       4 . The stirrup according to  claim 1 , characterized in that it comprises a number of oblique tracts ( 2 ) apt to provide a whole length so as to cover a tract of reinforcement structure ( 8 ) to be implemented with a pre-established length.  
   
   
       5 . The stirrup according to  claim 1 , characterized in that it has a not constant pitch and oblique tracts ( 2 ) with different lengths.  
   
   
       6 . The stirrup according to  claim 1 , characterized in that it comprises a plurality of plane polygonal windings ( 4 ) substantially orthogonal to said longitudinal axis (A) and alternated by portions of broken-spiral stirrup structure.  
   
   
       7 . The stirrup according to  claim 1 , characterized in that it comprises anchoring means ( 7 ) to keep said stirrup structure in a compacted state.  
   
   
       8 . A method for implementing a broken-spiral stirrup according to  claim 1 , comprising the bending of a metallic bar so as to obtain a stirrup structure ( 1 ) with extension according to its longitudinal axis (A) which comprises a sequence of tracts substantially perpendicular ( 3 ) and tracts substantially oblique ( 2 ) with respect to said longitudinal axis (A) forming winding configurations with polygonal projection onto a plane substantially perpendicular to said longitudinal axis (A), characterized in that said bending comprises plastic deformations of the tracts constituting said winding configurations, so that said oblique tracts arrange tilted in directions different between them and on faced surfaces.  
   
   
       9 . The method according to  claim 8 , characterized in that it comprises the compaction of said stirrup structure ( 1 ) until the state wherein said winding configurations are mutually adjacent.  
   
   
       10 . The method according to  claim 9 , characterized in that it comprises the locking of said stirrup structure ( 1 ) in the compacted configuration performed with anchoring means ( 7 ).  
   
   
       11 . A method for assembling the reinforcement structure ( 8 ), characterized in that it comprises steps of introducing reinforcement longitudinal members ( 6 ) in one or more stirrup structures ( 1 ) in the compacted state and steps of loosening the compacted stirrup structure(s) ( 1 ) with consequent re-assumption of the extended configuration by the same due to elastic effect and shape memory.  
   
   
       12 . The method according to  claim 11 , characterized in that the step of loosening the stirrup structure ( 1 ) from the anchoring means ( 7 ) is performed outside or directly inside the receiving structure, in particular in the form.  
   
   
       13 . The method according to  claim 12 , characterized in that the reinforcement structures ( 8 ) are implemented in the site, the stirrup structures ( 1 ) are implemented in the workshop and they are handled in the compacted state and wherein in the site said stirrup structures ( 1 ) in the compacted state are positioned onto the assembly plane or in the form, the anchoring means ( 7 ) is removed and each of said stirrup structure ( 1 ) is released in axial direction in order to assume the extended state, with the pitch (D) equal to the one provided in the design, then said stirrup structures ( 1 ) are stabilized in such state to the reinforcement longitudinal members ( 6 ).  
   
   
       14 . The method according to  claim 13 , characterized in that it comprises the arrangement of a plurality of stirrup structures ( 1 ) aligned between them, the marking on at least one reinforcement longitudinal member ( 6 ) of the ending points of each stirrup structure ( 1 ), the positioning of the reinforcement longitudinal members ( 6 ) inside the stirrup structures ( 1 ), as well as at least a step of binding to said longitudinal members ( 6 ) the beginning and the end of each stirrup structure ( 1 ), wherein the bindings are performed at the marks shown on at least one of the reinforcement longitudinal members ( 6 ).  
   
   
       15 . The method according to  claim 14 , characterized in that the reinforcement longitudinal members ( 6 ) and the stirrup structures ( 1 ) are joined by ties ( 5 ) only at the ends of the stirrup structures ( 1 ) themselves.  
   
   
       16 . The method according to  claim 15 , characterized in that the stirrup structures ( 1 ) consecutive between them are anchored to the reinforcement longitudinal members ( 6 ) immediately one after the other.  
   
   
       17 . The method according to  claim 13 , characterized in that the stirrup structures ( 1 ) consecutive between them are anchored to the reinforcement longitudinal members ( 6 ) at a distance between them substantially equal to the stirrup pitch (D).  
   
   
       18 . The method according to  claim 13 , characterized in that the stirrup structures ( 1 ) consecutive between them have the same stirrup pitch (D).  
   
   
       19 . The method according to  claim 13 , characterized in that the reinforcement structure ( 8 ) is implemented with stirrup structures ( 1 ) with different stirrup pitches.  
   
   
       20 . The method according to any of the  claim 13  in that in the production of reinforcement structures ( 8 ) three or more stirrup structures ( 1 ) are used with the central one or ones provided with the stirrup pitch higher than the side stirrup structures ( 1 ).  
   
   
       21 . Structural member manufactured with the stirrup structure ( 1 ) of  claim 1 , obtained with a reinforcement structure ( 8 ).