Column and beam construction and method

Abstract

Site cast or pre-cast columns aligned and braced by pre-cast pre-stressed floor beams are used to erect a concrete skeleton structure for a building. The ends of the horizontal beams are imbedded in the columns at floor levels to stabilize and complete the skeleton. The horizontal beams are pre-stressed and are cast with passages that permit insertion of continuous reinforcing tendons into a network throughout each floor level. The tendons are subsequently post-tensioned so to tie the beams together and to the columns to reinforce the skeleton. Slab drop-forms starting at the roof and progressing floor-by-floor downward allow monolithic post-tensioned floor slabs to be cast to tie the skeleton into a unitary structure. The beams are usually integrated (buried) into each monolithic floor slab, keyed, doweled and bonded with bonding agent at cold joints to become a part of the slab structure.

Description

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to concrete building construction comprised of column-supported concrete slabs. The present innovation imbeds ends of pre-cast horizontal beams at floor levels in all columns to stabilize and complete a skeleton. Site-cast roof and floors may subsequently be formed and poured sequentially from the top down, efficiently reusing the formwork by simply lowering forms for floor spans between the floor beams of the skeleton floor by floor as the upper floors are finished. The specialized pre-cast floor beams are essential to the invention.

[0004] 2. Identification of Background Art

[0005] Broms, Carl Eric, “Punching of Flat Plates, ACI Structural Journal, V. 87, No. 3, May-June, pp. 292-304. U.S. Pat. No. 6,385,930 issued to Broms et al.

SUMMARY AND OBJECTS OF THE INVENTION

[0006] The present invention utilizes pre-cast or site-cast columns aligned and braced by pre-cast pre-stressed floor beams to erect a concrete skeleton structure for a building. The present innovation imbeds ends of pre-cast horizontal beams at floor levels in all columns to stabilize and complete the skeleton. The resulting skeleton utilizes pre-cast horizontal beams that are pre-stressed and cast with passages or ducts that permit insertion of continuous reinforcing tendons into a network throughout each floor level. Said tendons are subsequently post-tensioned so to tie the beams together and to the columns to reinforce the skeleton. Slab drop-forms starting at the roof and progressing floor-by-floor downward allow post-tensioned floor slabs to tie the skeleton into a unitary structure. The beams are usually integrated (buried) into each monolithic floor slab, keyed, doweled and bonded with bonding agent at cold joints to become a part of the slab structure.

[0007] Objects and advantages of my invention are:

[0008] It utilizes simple reusable forms and pre-cast components in rapid sequence for quick erection.

[0009] Small section building components require only small capacity lifting equipment.

[0010] Top down roof and floor construction protects subsequent construction and finishes from water and weather damage.

[0011] The objects of the invention and others as well are realized by a method for constructing a building having upright columns and slabs transversely spanning and supported by the columns, the method comprising the steps of: a) providing column sections or column forms bounding spaces for the columns; b) arranging pre-cast beams so as to span the distance between adjacent columns at a predetermined level of the columns, the beams forming a transverse grid of spaced beams, the ends of each beam intruding into the space bounded by a column exterior; c) pouring concrete into the forms to form columns that envelop the beam ends or erecting precast column sections that ennclose the ends of each beam; d) providing elongated reinforcing elements that extend (1) within the beams along the length of the beams and (2) between the beam ends within the columns, the reinforcing elements being unbonded to the beams and to the concrete in the columns, whereby the reinforcing elements can move within the beams and the columns during a post-tensioning operation; e) arranging slab forms transversely between the beams and the columns at the predetermined level of the beams; and f) pouring concrete into the slab forms to form the slabs.

[0012] Objects and advantages of embodiments of the present invention are disclosed herein. Still further objects and advantages will become apparent from a consideration of the ensuing description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 illustrates the column and beam placement for the first floor of a building constructed according to the present invention;

[0014] FIG. 2 illustrates a four-floor skeleton of a building constructed according to the present invention, before forming roof and floor slabs;

[0015] FIG. 3 illustrates details of forming the column-beam joint;

[0016] FIG. 4 illustrates details of the column-beam joint;

[0017] FIG. 5 illustrates bottom view of a beam, showing dowel hole, beam-end form alignment detent, slab form dams and their beam fastenings;

[0018] FIG. 6 illustrates details of a slab form;

[0019] FIG. 7 illustrates details of a joint between perimeter beams with tendon anchors and thinner interior beam aligned on a column;

[0020] FIG. 8 illustrates details of preferred pre-cast column sections and beam ends poised above pre-cast beam pockets; and

[0021] FIG. 9 illustrates anchors for unbonded beam tendons terminating in perimeter columns.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0022] Pre-cast column sections (FIG. 8) for the first floor are erected upon the foundation rising to the level of the next floor. The column sections contain pockets (FIG. 8a) for pre-cast floor beam ends imbedded in the column and joined at weld plates cast into column and beam (FIG. 8c, d, and e) and steel dowels (FIG. 3c) passing vertically through holes (FIG. 5a) in the beams about 18 inches into the column below and an equal distance into the column above and grouted into the column.

[0023] The pre-cast beams are an essential part of the invention. In this embodiment they are to be totally incorporated in the post-tensioned monolithic concrete slabs (FIG. 6a) to be subsequently poured sequentially from the roof down after the skeleton is erected. The pre-stressed beams each contain four bonded tendons (FIG. 4b) cut to beam length. Beams also each contain passages formed, for example, by PVC ducts (FIG. 4c) for subsequent insertion of four unbonded (post-tensioned) tendons running continuously end-to-end and side-to-side in the building, passing through every column tic-tac-toe fashion (FIG. 4a) and terminated and anchored in perimeter columns (FIG. 9a). Heavy steel dowels (FIG. 3d) pass through the columns and are grouted into the columns projecting into the floor space where they will help the beams lock the floors into the columns (FIG. 8f). The unbonded tendons, pre-stressed beam ends and the steel dowels provide extraordinary resistance to punching shear by columns.

[0024] Perimeter beams (FIG. 7a) are floor thickness. The interior beams are designed with 2 or 3 inches clearance below floor level ((FIG. 7b) so that shrouded unbonded tendons can be draped across them and crossed two ways in floor forms and anchored (FIG. 6c) in perimeter beams to create a monolithic slab (FIG. 6a) across and burying all the beams creating a unitary structure tying beams, floor and columns together. The skeleton is supported with temporary vertical shoring (FIG. 6b) until reusable drop forms supported by said shoring allows casting the roof slab first and by lowering the drop forms, subsequently each of the floor slabs in sequence from top to bottom.

[0025] The skeleton of a typical 40,000 sq. ft. structure requires approximately 200 cubic yards of concrete exclusive of slabs, foundation and shear bracing.

[0026] To recap and amplify, the pre-cast beams provide alignment and lateral bracing for the columns and facilitate the casting of the floors. Column spacing and screw anchors (FIG. 5e) for attaching temporary slab form dams (FIG. 5f) are designed into the beams at the start. The form dams seal drop forms against surrounding beams for pouring. The PVC ducts crossing tic-tac-toe fashion in the columns must be joined by short sleeves (FIG. 4a) during assembly before pouring if site casting columns to keep the ducts clear of concrete. Shear bracing can be by any method common in the industry.

[0027] The support for a floor slab form in this embodiment is shown in FIG. 6. in which floor slab form is mounted on shoring.

OTHER EMBODIMENTS

[0028] Optional site cast columns instead of precast. FIGS. 3, 4, 5 and 7 illustrate details representative of site cast columns as well as of precast columns.

[0029] Beams that although embedded in a slab, also project into ceiling space below slab permitting longer spans between columns.

Claims

1. A method for constructing a building having upright columns and slabs transversely spanning and supported by the columns, the method comprising the steps of: a) providing column forms bounding spaces for the columns; b) arranging pre-cast beams so as to span the distance between adjacent forms at a predetermined level of the columns, the beams forming a transverse grid of spaced beams, the ends of each beam intruding into the space bounded by a form; c) pouring concrete into the forms to form columns that envelop the beam ends; d) providing elongated reinforcing elements that extend (1) within the beams along the length of the beams and (2) between the beam ends within the forms, the reinforcing elements being unbonded to the beams and to the concrete in the formed columns, whereby the reinforcing elements can move within the beams and the columns during a post-tensioning operation; e) arranging slab forms transversely between the beams and the columns at the predetermined level of the columns; and f) pouring concrete into the slab forms to form the slab.

2. The method as recited in claim 1, wherein passages for the reinforcing elements are provided in the beams, and further comprising the following step performed before step c): providing sleeves in the column forms, the sleeves extending between confronting beam ends and disposed in alignment with the passages, the elongated reinforcing elements provided in step d) being inserted through the passages and through the sleeves.

3. The method as recited in claim 1, and further comprising the following steps: providing unbonded elongated reinforcing elements within a floor slab, the reinforcing elements within the floor slab extending into and terminating in perimeter beams located at a perimeter edge of the floor slab, a first set of the reinforcing elements within the floor slab oriented in a first direction, and a second set of the reinforcing elements within the floor slab oriented in a second direction that is generally orthogonal to the first direction; providing anchoring elements secured to the perimeter beams for gripping the ends of the reinforcing elements within the floor slab and for effecting a post-tensioning operation on the reinforcing elements within the floor slab; and providing anchoring elements within perimeter columns located at a perimeter edge of the floor slab for gripping the ends of the reinforcing elements in the beams and for effecting a post-tensioning operation on the reinforcing elements in the beams.

5. A method for constructing a building having upright columns and slabs transversely spanning and supported by the columns, the method comprising the steps of: a) erecting pre-cast column sections for supporting a floor, the column sections having beam pockets formed therein and being provided with metal inserts at the level of the beam pockets; b) arranging pre-cast beams so as to span the distance between adjacent column sections at the level of the beam pockets, the beams forming a transverse grid of spaced beams, the ends of each beam intruding into the beam pockets and being provided with metal inserts; c) fastening the metal inserts in the beams to the metal inserts in the column sections; d) providing elongated reinforcing elements that extend (1) within the beams along the length of the beams and (2) between the beam ends within the column sections, the reinforcing elements being unbonded to the beams and to the concrete in the columns, whereby the reinforcing elements can move within the beams and the columns during a post-tensioning operation; e) arranging slab forms transversely between the beams and the columns; and f) pouring concrete into the slab forms to form the slab.

6. The method as recited in claim 5, and further comprising the following steps: providing unbonded elongated reinforcing elements within a floor slab, the reinforcing elements within the floor slab extending into and terminating in perimeter beams located at a perimeter edge of the floor slab, a first set of the reinforcing elements within the floor slab oriented in a first direction, and a second set of the reinforcing elements within the floor slab oriented in a second direction that is generally orthogonal to the first direction; providing anchoring elements secured to the perimeter beams for gripping the ends of the reinforcing elements within the floor slab and for effecting a post-tensioning operation on the reinforcing elements within the floor slab; and providing anchoring elements within perimeter columns located at a perimeter edge of the floor slab for gripping the ends of the reinforcing elements in the beams and for effecting a post-tensioning operation on the reinforcing elements in the beams.