Method of Making Monolithic Concrete Structures

Abstract

A method of making a monolithic portion of a concrete building from a combination of pre-cast and cast-in-situ elements distributes moments and shear loads by using flanged pre-cast columns for support. In addition, a precast ‘waffle’ element is used to reduce the overall weight of the slab being formed. In preferred versions of this method support arms are provided that link formwork to an anchor cast into a pre-cast column and from the anchor to a load bearing point on a lower, pre-cured slab.

1 ) A method of making a monolithic reinforced concrete portion of a building comprising an upper slab portion having a selected thickness extending between a top surface at a selected top height to a bottom surface at a selected bottom height, the slab portion connected to four columns defining a rectangular bay, the method comprising the steps of:
 a) providing the four precast reinforced columns respectively erected at respective corners of the rectangular bay, each of the columns comprising a respective vertically extensive portion and a respective horizontally extensive rectangular reinforced rigid flange portion having rebar protruding from each of its four edges, wherein each of the flange members has a top surface at the selected top height, the columns oriented so that each flange portion has two edges parallel to and facing respective edges of two other of the flange portions so as to define four border areas, each of which extends between a respective pair of the flange portions;   b) placing a first temporary support within the rectangular bay so that a top of the support is substantially at the selected bottom height;   c) placing a rectangular reinforced precast central slab member on the first support, the central slab member extending across the bay so as to abut all four of the flange members, the central slab member having a thickness over most of its area that is less than the thickness of the upper slab portion, the central slab member having rebar protruding outward from each of its edges;   d) supporting respective forms beneath each of the border areas;   e) pouring concrete over the forms and the central slab member to form the upper slab portion;   f) waiting for the concrete to harden; and   g) removing the supports.   
     
     
         2 ) The method of  claim 1  wherein each of the flange portions comprises four rabbeted edge portions, each of which comprises a respective lower portion extending further away from the associated column portion than does a respective upper portion, wherein both the upper and lower portions have rebar extending outwardly therefrom. 
     
     
         3 ) The method of  claim 1  wherein the central slab comprises four rabbeted edge portions, each of which comprises a respective upper portion extending to a respective edge of the central slab and a respective lower portion that does not extend to the respective edge, wherein both the upper and lower portions have rebar extending outwardly therefrom. 
     
     
         4 ) The method of  claim 1  wherein:
 each of the flange portions comprises four rabbeted edge portions, each of which comprises a respective lower portion extending further away from the associated column portion than does a respective upper portion, and wherein both the upper and lower portions have rebar extending outwardly therefrom except in four flange corner regions;   each of the central slab portions comprises four rabbeted edge portions, each of which comprises a respective upper portion extending to a respective edge of the central slab and a respective lower portion that does not extend to the respective edge, wherein both the upper and lower portions have rebar extending outwardly therefrom except in four central slab corner regions; and   wherein the dimensions of the flange portions and central slab are selected so that when the central slab is placed on the first temporary support, each of the four central slab corner regions rests on top of a respective flange portion corner region.   
     
     
         5 ) The method of  claim 1  comprising an additional step, carried out before the concrete is poured, of placing additional rebar in each of the border areas, the additional rebar running parallel to a nearest central slab edge. 
     
     
         6 ) The method of  claim 1  wherein each of the columns comprises a respective anchor disposed in the vertically extensive portion thereof, and wherein the step of supporting a respective form plate beneath each of the border areas comprises connecting a respective first support arm between the respective form plate and the anchor disposed in a respective one of the pair of columns defining the respective border area; and connecting a respective second support arm between each of the respective anchors and a cured bottom slab. 
     
     
         7 ) The method of  claim 1  wherein the central slab comprises two mutually perpendicular sets of rebar running between respective parallel edges thereof, the slab further comprising a plurality of low density elements. 
     
     
         8 ) A method of making a monolithic reinforced concrete portion of a building comprising an upper slab supported by a plurality of columns extending above a bottom slab, the method comprising the steps of:
 a) providing the plurality of precast reinforced columns comprising respective vertically extensive portions and respective horizontally extensive rigid flange portions disposed at a selected slab height, wherein each vertically extensive portion comprises a respective anchor for connecting a support arm to the column;   b) erecting the columns to extend from a lower slab to at least the height of the upper slab;   c) placing formwork extending between at least two of the columns and supporting the formwork by a combination of at least two first and at least two second support arms, wherein each of the first support arms connects a respective portion of the formwork to a respective anchor and wherein each second support arm connects the respective anchor to a respective load bearing point on the bottom slab;   d) pouring concrete onto the formwork and allowing it to harden; and   e) removing the support arms and the formwork.   
     
     
         9 ) The method of  claim 8  wherein each anchor comprises a respective metal member cast into a respective column. 
     
     
         10 ) The method of  claim 8  wherein each support arm is adjustable in length. 
     
     
         11 ) A method of making a monolithic reinforced concrete portion of a building comprising a slab supported by a plurality of columns comprising at least four columns erected at the four corners of a rectangular bay, the method comprising the steps of:
 a) providing a rectangular pre-cast slab member comprising a plurality of reinforced beam portions extending parallel to each of the edges of the slab member and an array of low-density regions disposed intermediate the beam portions, the slab member comprising rebar extending outward from each of the beam portions along each of the four edges of the slab member;   b) supporting the slab member in abutting contact with each of the columns; and   c) pouring concrete to join the slab member to the columns.   
     
     
         12 ) The method of  claim 11  wherein the low density regions comprise polymeric foam blocks having protrusions extending outward from faces thereof. 
     
     
         13 ) The method of  claim 11  wherein each of the columns comprises a laterally extensive flange portion having a rabbeted edge in which an upper portion of the flange portion is stepped back from the edge; wherein the slab member comprises a rabbeted edge in which a lower portion of the slab member is stepped back from the edge and wherein the step of supporting the slab member in abutting contract comprises placing each of four corner portions of the slab member on respective corner portions of each of the flange portions. 
     
     
         14 ) The method of  claim 11  wherein selected portions of the slab member have a thickness equal to the thickness of the slab and other selected portions of the slab member have a thickness substantially equal to one half of the slab thickness.