Precast concrete formwork, floor system and a method of construction

Abstract

Formwork for constructing a floor system in a building, the formwork comprising: a plurality of pre-cast concrete joists positioned in a generally parallel arrangement, wherein one or more of the joists comprises: a horizontal base portion; and an upwardly directed portion extending substantially along the length of the joist, the upwardly directed portion having spaced apart surfaces extending upwardly from the base wherein respective shelf portions of the base are located adjacent said upwardly directed portion; a plurality of pre-cast concrete members for extending along a length of the joists for receiving wet concrete; and a supporting arrangement to support opposite ends each of the pre-cast concrete members upon oppositely arranged shelf portions of two adjacent joists.

The claims defining the invention are as follows: 
     
         1 . Formwork for constructing a floor system in a building, the formwork comprising:
 a plurality of pre-cast concrete joists positioned in a generally parallel arrangement, wherein one or more of the joists comprises: a horizontal base portion; and an upwardly directed portion extending substantially along the length of the joist, the upwardly directed portion having spaced apart surfaces extending upwardly from the base wherein respective shelf portions of the base are located adjacent said upwardly directed portion;   a plurality of pre-cast concrete members for extending along a length of the joists for receiving wet concrete; and   a supporting arrangement to support opposite ends each of the pre-cast concrete members upon oppositely arranged shelf portions of two adjacent joists.   
     
     
         2 . Formwork in accordance with  claim 1  one or more of the pre-cast concrete members comprises a shell for receiving wet concrete, the shell being adapted to be coupled with respective downwardly directed supporting portions for supporting the shell on the oppositely arranged shelf portions of two adjacent joists. 
     
     
         3 . Formwork in accordance with  claim 1  or  2  wherein the supporting portions are integrally formed with the pre-cast members. 
     
     
         4 . Formwork in accordance with any one of the preceding claims wherein an outer surface of the pre-cast concrete members in combination with the surface of the upwardly directed portion of the supporting joists positioned at opposite ends defines an in-use receiving portion for receiving wet concrete. 
     
     
         5 . Formwork in accordance with any one of the preceding claims wherein the pre-cast concrete members comprises edge portions extending along a length of the pre-cast concrete members wherein preferably at least a first edge portion extends along a first lateral side of the pre-cast concrete member and at least a second edge portion extends a second lateral side of the pre-cast concrete member. 
     
     
         6 . Formwork in accordance with  claim 1  wherein one or more of the pre-cast concrete members comprises:
 a pan for receiving the wet concrete; and 
 shoulder portions located at opposite ends of the pan, said shoulder portions being adapted to be supported on the oppositely arranged shelf portions of two adjacent joists. 
 
     
     
         7 . Formwork in accordance with  claim 6  wherein the pan in combination with the surface of the upwardly directed portion of the supporting joists positioned at opposite ends defines an in-use receiving portion for receiving wet concrete. 
     
     
         8 . Formwork in accordance with any one of the preceding claims further comprising pre-cast concrete joists supported by a plurality of beams extending generally in a perpendicular direction relative to the general direction of the said pre-cast concrete joists. 
     
     
         9 . Formwork in accordance with  claim 8  wherein the beam comprises a beam portion with a substantially flat profile with two spaced apart formations extending upwardly from the beam portion, the said formations extending along a length of the beam and joist receiving portions extending outwardly from the said formations for supporting an end portion of a plurality of joists. 
     
     
         10 . Formwork in accordance with any one of  claim 8  or  9  wherein an outwardly projecting end portion of the plurality of joists is supported upon a joist receiving portion of the beam portion, the joist receiving portion of the beam preferably extending in a perpendicular direction relative to the said projecting end portions of the joist. 
     
     
         11 . Formwork in accordance with any one of  claims 8  to  10  wherein an underside bottom surface of the beam substantially lies in the same plane as a bottom surface of the joist. 
     
     
         12 . Formwork in accordance with any one of the preceding claims further comprising:
 a first connecting mechanism for connecting a first joist positioned on a first lateral side of the beam with a second joist positioned on a second lateral side of the beam, said connecting mechanism being further adapted for preferably applying a negative bending force to the first and second joists during use; and   a second connecting mechanism for connecting two adjacently located beams supported simultaneously on a column, the connector being provided for applying negative bending to said adjacently located beams.   
     
     
         13 . Formwork in accordance with any one of  claims 8  to  12  further comprising column formwork members for forming columns to support said beams wherein each of the column formwork members can be inter-connected to define a hollow portion for receiving wet concrete. 
     
     
         14 . Formwork in accordance with  claim 13  wherein end portions of each of the column formwork members comprises connecting portions for inter-connecting the column formwork members such that imaginary plane of a first column formwork member is transversely arranged relative to an imaginary plane of second column formwork member inter-connected with the first column formwork member. 
     
     
         15 . Formwork in accordance with any one of  claim 13  or  14  wherein said locking portions extend along a longitudinal edge of the column formwork member such that in an inter-connected configuration the locking member is adapted to be received in a recess of another of said column formwork, said recess extending along a longitudinal edge of said another column formwork. 
     
     
         16 . Formwork in accordance with any one of the preceding claims further comprising one or more permanent formwork members for being positioned in between two spaced joists and wherein preferably the permanent formwork members comprise a substantially L-shaped or U-shaped cross section. 
     
     
         17 . Formwork in accordance with any one of the preceding claims wherein the joists of the formwork further comprise one or more apertures for receiving reinforcing bars, the reinforcing bars extending in a transverse direction relative to the general direction of the joists, the reinforcing bars being adapted for being tensioned (by way of post-tensioning) after pouring concrete into the pre-cast concrete receiving members. 
     
     
         18 . Formwork in accordance with any one of the preceding claims wherein at least one the pre-cast concrete members comprises a stepped configuration having an in-use upper portion and an in-use lower portion. 
     
     
         19 . A pre-cast concrete joist comprising: a horizontal base portion; and an upwardly directed portion extending substantially along the length of the joist, the upwardly directed portion having spaced apart surfaces extending upwardly from the base wherein shelf portions of the base are located adjacent said upwardly directed portion, each of the shelf portions defining a seat for receiving a connecting portion of a pre-cast concrete pan member or a pre-cast concrete shell member wherein height of the upwardly directed portion is equal to or greater than vertical height of the said shelf portions. 
     
     
         20 . A pre-cast concrete member for being positioned in between and supported spaced apart joists or beams, the precast member extending along a length of the joists or beams for receiving wet concrete, the precast member comprising a supporting arrangement to support opposite ends each of the pre-cast concrete members upon oppositely arranged joists or beams. 
     
     
         21 . A method of constructing a suspended floor in a building, the method comprising the steps of:
 positioning a plurality of pre-cast concrete joists in a generally parallel arrangement, wherein one or more of the joists comprises: a horizontal base portion; and an upwardly directed portion extending substantially along the length of the joist, the upwardly directed portion having spaced apart surfaces extending upwardly from the base wherein shelf portions of the base are located adjacent said vertical portion;   positioning a plurality of pre-cast concrete members in between adjacently located joists, said pre-cast concrete members being positioned for extending along a length of the joists for receiving poured concrete;   supporting opposite ends of each of the pre-cast concrete members upon oppositely arranged shelf portions of two adjacent joists; and   pouring fresh concrete into a receiving portion defined by the pre-cast concrete members.