GB2037863A

GB2037863A - Earthquake-resistant Structural Building Element and Method of Making the Same

Info

Publication number: GB2037863A
Application number: GB7849020A
Authority: GB
Original assignee: WIMPEY CONST UK
Current assignee: WIMPEY CONST UK
Priority date: 1978-12-19
Filing date: 1978-12-19
Publication date: 1980-07-16
Also published as: AR223021A1; BR7908158A; GB2037863B

Abstract

A structural building element comprises a core of no-fines concrete 5 and a ductile render 11 capable of increasing the resistance of the core to collapse when subjected to shear forces such as those produced by an earthquake. Ductile render 11 may comprise 13 mm mesh chicken wire or 15 mm plastics mesh. These may be applied to each side of the core 5, and may be secured by 1.5 mm diameter soft- iron: tying-wire passing through the core. The render may be of mortar comprising Portland cement, lime, and sand. <IMAGE>

Description

SPECIFICATION Structural Building Element and Method of Making the Same The invention relates to structural building elements such as, for example, walls of buildings, and to methods of making the same.

Seismic action, that is earthquakes and earth tremors, will cause a building structure to vibrate at a frequency dependent upon its overall stiffness, and consequently, horizontal forces alternately will be applied to the building structure. The major requirement, therefore, for a building structure likely to be exposed to seismic action is an adequate horizontal load carrying capacity, ductility, i.e. the ability to maintain a significant load carrying capacity even after the building structure has been subject to horizontal forces during an earthquake, and characteristics which reduce damage to the building structure and minimise remedial work after a minor earth tremor and reduce the risk to those attempting to escape from the building structure during a major earthquake.

Tests have shown that a building structure whose walls etc. are of no-fines concrete formed in conventional manner have sufficient horizontal load carrying capacity and ductility to withstand minor earth tremors but, when subjected to extreme horizontal forces such as would be experienced during a major earthquake, it has been found that disintegration or collapse of the no-fines concrete takes place.

According to one aspect of the present invention there is provided a structural building element comprising a core of no-fines conrete and a ductile render capable of increasing the resistance of the core to collapse when subjected to shear forces.

In one embodiment the render includes a wire mesh. The wire mesh may be a 13 mm. wire mesh.

In another embodiment the render includes a plastics mesh. A plastics mesh may be a 1 5 mm, plastics mesh.

The mesh may be in strips butt-jointed to each other.

Preferably the render includes a layer of lime mortar. The layer may consist of one part by weight of cement, one part by weight of lime and six parts by weight of sand.

According to a further aspect of the present invention there is provided a method of making a structural building element comprising forming a core of no-fines concrete and applying thereto a ductile render capable of increasing the resistance of the core to collapse when subjected to shear forces.

The invention is illustrated, merely by way of example, in the accompanying drawing which shows various stages of the construction of a building structure according to the present invention.

Initially, as indicated by reference numeral 1, internal shuttering, including, if desired, door frames, window frames etc. is erected. Next, prefabricated column reinforcement 2 is located in position with stop ends and cores 3 if necessary. External shuttering 4 is then erected.

No-fines concrete 5 is then poured to the desired level between the internal and external shuttering.

Dense concrete 6 is poured into the cores 3 to form columns, the cores 3 immediately being removed by means, for example, of a crane, before the no-fines concrete and dense concrete have had time to harden so that the no-fines concrete and dense concrete intermingle.

Prefabricated beam reinforcement 7 is placed on top of the no-fines concrete core so formed and dense concrete is poured around the reinforcement 7 to form a beam 8. The internal and external shuttering is then struck or removed as indicated by reference numeral 9. Formwork is then erected in the conventional manner and flooring 10 formed by any known technique.

Finally, a ductile render 11 is applied to the nofines concrete walls to increase its strength and to contain and so increase the resistance of the nofines concrete core to collapse when subjected to shear forces resulting from seismic action.

The render 11 may include a 13 mm, mesh chicken wire secured to each side of the no-fines concrete wall using, for example, 1.5 mm.

diameter soft iron tying wire passing through the core. In one experiment, the chicken wire was applied in 600 mm wide vertical strips buttjointed and secured together by the tying wire.

Each side of the core then has two layers of lime mortar applied to a total thickness of 13 mm. The lime mortar consists of 1 part by weight Portland cement, 1 part by weight lime and 6 parts by weight sand.

It has been found that the ductility and strength of the render may be further improved by overlapping the strips of chicken wire by 200 mm and tying them together with the tying wire at 1 00 mm centres vertically and horizontally prior to the application of the layers of lime mortar.

It has also been found that a plastics mesh, for example, a 1 5 mm plastics mesh manufactured by Netlon Limited, may be used in place of the chicken wire. This gives superior strength and ductility.

Claims

1. A structural building element comprising a core of no-fines concrete and a ductile render capable of increasing the resistance of the core to collapse when subjected to shear forces.

2. A building element as claimed in claim 1 in which the render includes a wire mesh.

3. A building element as claimed in claim 2 in which the wire mesh is a 13 mm. wire mesh.

4. A building element as claimed in claim 1 in which the render includes a plastics mesh.

5. A building element as claimed in claim 4 in which the plastics mesh is a 1 5 mm. plastics mesh.

6. A building element as claimed in any of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Structural Building Element and Method of Making the Same The invention relates to structural building elements such as, for example, walls of buildings, and to methods of making the same. Seismic action, that is earthquakes and earth tremors, will cause a building structure to vibrate at a frequency dependent upon its overall stiffness, and consequently, horizontal forces alternately will be applied to the building structure. The major requirement, therefore, for a building structure likely to be exposed to seismic action is an adequate horizontal load carrying capacity, ductility, i.e. the ability to maintain a significant load carrying capacity even after the building structure has been subject to horizontal forces during an earthquake, and characteristics which reduce damage to the building structure and minimise remedial work after a minor earth tremor and reduce the risk to those attempting to escape from the building structure during a major earthquake. Tests have shown that a building structure whose walls etc. are of no-fines concrete formed in conventional manner have sufficient horizontal load carrying capacity and ductility to withstand minor earth tremors but, when subjected to extreme horizontal forces such as would be experienced during a major earthquake, it has been found that disintegration or collapse of the no-fines concrete takes place. According to one aspect of the present invention there is provided a structural building element comprising a core of no-fines conrete and a ductile render capable of increasing the resistance of the core to collapse when subjected to shear forces. In one embodiment the render includes a wire mesh. The wire mesh may be a 13 mm. wire mesh. In another embodiment the render includes a plastics mesh. A plastics mesh may be a 1 5 mm, plastics mesh. The mesh may be in strips butt-jointed to each other. Preferably the render includes a layer of lime mortar. The layer may consist of one part by weight of cement, one part by weight of lime and six parts by weight of sand. According to a further aspect of the present invention there is provided a method of making a structural building element comprising forming a core of no-fines concrete and applying thereto a ductile render capable of increasing the resistance of the core to collapse when subjected to shear forces. The invention is illustrated, merely by way of example, in the accompanying drawing which shows various stages of the construction of a building structure according to the present invention. Initially, as indicated by reference numeral 1, internal shuttering, including, if desired, door frames, window frames etc. is erected. Next, prefabricated column reinforcement 2 is located in position with stop ends and cores 3 if necessary. External shuttering 4 is then erected. No-fines concrete 5 is then poured to the desired level between the internal and external shuttering. Dense concrete 6 is poured into the cores 3 to form columns, the cores 3 immediately being removed by means, for example, of a crane, before the no-fines concrete and dense concrete have had time to harden so that the no-fines concrete and dense concrete intermingle. Prefabricated beam reinforcement 7 is placed on top of the no-fines concrete core so formed and dense concrete is poured around the reinforcement 7 to form a beam 8. The internal and external shuttering is then struck or removed as indicated by reference numeral 9. Formwork is then erected in the conventional manner and flooring 10 formed by any known technique. Finally, a ductile render 11 is applied to the nofines concrete walls to increase its strength and to contain and so increase the resistance of the nofines concrete core to collapse when subjected to shear forces resulting from seismic action. The render 11 may include a 13 mm, mesh chicken wire secured to each side of the no-fines concrete wall using, for example, 1.5 mm. diameter soft iron tying wire passing through the core. In one experiment, the chicken wire was applied in 600 mm wide vertical strips buttjointed and secured together by the tying wire. Each side of the core then has two layers of lime mortar applied to a total thickness of 13 mm. The lime mortar consists of 1 part by weight Portland cement, 1 part by weight lime and 6 parts by weight sand. It has been found that the ductility and strength of the render may be further improved by overlapping the strips of chicken wire by 200 mm and tying them together with the tying wire at 1 00 mm centres vertically and horizontally prior to the application of the layers of lime mortar. It has also been found that a plastics mesh, for example, a 1 5 mm plastics mesh manufactured by Netlon Limited, may be used in place of the chicken wire. This gives superior strength and ductility. Claims

6. A building element as claimed in any of claims 2 to 5 in which the mesh is in strips buttjointed to each other.

7. A building element as claimed in any preceding claim in which the render includes a layer of lime mortar.

8. A building element as claimed in claim 7 in which the layer consists of one part by weight of cement, one part by weight of lime and six parts by weight of sand.

9. A structural building element substantially as herein described with reference to and as shown in the accompanying drawing.

10. A method of making a structural building element comprising forming a core of no-fines concrete and applying thereto a ductile render capable of increasing the resistance of the core to collapse when subjected to shear forces.

11. A method of making a structual building element substantially as heren described with reference to the accompanying drawing.