GB2059479A - Composite prestressing of concrete structures - Google Patents
Composite prestressing of concrete structures Download PDFInfo
- Publication number
- GB2059479A GB2059479A GB7935608A GB7935608A GB2059479A GB 2059479 A GB2059479 A GB 2059479A GB 7935608 A GB7935608 A GB 7935608A GB 7935608 A GB7935608 A GB 7935608A GB 2059479 A GB2059479 A GB 2059479A
- Authority
- GB
- United Kingdom
- Prior art keywords
- prestressing
- reinforcements
- prestressed
- reinforcement
- cases
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/08—Members specially adapted to be used in prestressed constructions
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- Engineering & Computer Science (AREA)
- Architecture (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Reinforcement Elements For Buildings (AREA)
Abstract
In a composite prestressing of a concrete structure, there are prestressed reinforcements and unstressed reinforcements. Both prestressed and unstressed reinforcements are made of the same material which is a steel having a breaking strength between 60 and 120 kg/mm<2>.
Description
SPECIFICATION
Composite prestressing of structures
The invention relates to a method of prestressing invention relates to a method of prestressing structures and to prestressed structures.
In order to provide lasting prestressing forces, particularly in reinforced concrete parts, it is conventional to use steel reinforcements with a high elastic limit and a breaking strength which varies from 110 kg/mm2 to above 200 kg/mm2.
These reinforcements are initially tensioned to the limit of their plastic region and are subjected to different preliminary treatments to ensure their suitability for particular applications (fatigue strength, resistance to corrosion, reduction of the loss of tensile strength).
In certain cases, i.e. in cases which are called composite prestressing, tensioned prestressing reinforcements are used in addition to nontensioned reinforcements to ensure that the part of the structure has particular qualities, for example stability in the case of fire (floors, poles), or reduction of cracking (reservoirs, structures exposed to bad weather).
This combination of two types of reinforcement is also found in cases where the ratio R between the maximum load needed to cause collapse and the normal working load under which the concrete part or structure cannot crack, or cracks only to a limited extent, is higher than 2, which is the approximate ratio for conventional structures subjected to bending stress.
This is particularly so in the case of long, thin poles which are subjected to bending stresses in opposite directions and in which the essential role of the prestressing or of the additional reinforcements is to reduce the deformations which are likely to increase bending. This also applies to parts which may be subjected to particularly high abnormal forces, for example frameworks in seismic zones or railway-sleepers, for which the ratio R may reach values equal to or higher than 4.
Finally, the combination of two categories of reinforcement is used when the main load is the action of shearing stresses in bent parts which
have been prestressed according to the pretensioning method. In this case fracture by
creeping of a pretensioned reinforcement acted
upon by an additional tension in a crack near the support area is a dangerous phenomenon owing to its abruptness and for which the usual rules of
adding reinforcing effects do not apply. It is then
necessary to use non-tensioned additional
reinforcements which are suitably reinforced,
particularly since prestressing reinforcements with
a high elastic limit generally adhere badly in the
case of reinforced concrete with respect to the
anchorage of excess tensions on either side of the
crack.
This situation applies for example to heavily
loaded floors with a poor bearing surface, poles
prestressed by pretensioning and embedded in
their foundations and railway-sleepers.
The object of the invention is to obtain a
prestressing method which can be used in cases
of composite prestressing, and particularly in the
cases listed above, with reinforcements of a single
type owing to the fact they they consist of a steel
having particular properties.
For this purpose the invention provides a
prestressing method for cases of composite
prestressing, wherein reinforcements of a single type are used whose breaking strength is between
60 kg/mm2 and 120 kg/mm2, i.e. between that of
usual reinforcing steels of reinforced concrete and that of steels with a high elastic limit (H.L.E.) used for prestressing.
The invention also provides a prestressed structure including both prestressed and nonstressed reinforcements, both forms of
reinforcement being made of the same steel which
has a breaking strength in the range 60-120 kg/mm2.
Other details and characteristics of the invention will be apparent from the following
description.
In order to manufacture parts or make structures which have composite prestressing, the
reinforcements of the above-mentioned special type may be subjected to supplementary treatments.
In certain cases a preliminary work-hardening, tempering or other treatment is carried out, leading to a regularisation of the stress-strain curve of the steel, so as to be able to monitor the prestressing by checking the elongation.
In other cases a preliminary tensioning treatment is carried out, possibly completed by a heat treatment, at a force such that the tension in the reinforcement when the concrete is prestressed is particularly a linear function of the elongation. In general, this treatment prevents loss of tensile strength, susceptibility to brittleness and to corrosion and enhances fatigue strength of the reinforcement.
This preliminary tension is adapted to the residual tension required for each part or for each structure. It also depends on the manufacturing or construction methods (for example heat treatment of the concrete).
CLAIMS
1. A method of composite prestressing, wherein steel reinforcements of a single type are used for both prestressed and non-stressed
reinforcements, the breaking strength of the - reinforcements being between 60 kg/mm2 and
120 kg/mm2.
2. A method according to claim 1, wherein a preliminary work-hardening; tempering or other treatment is carried out, leading to a regularisation of the stress-strain curve of the steel, so as to be abide to monitor the prestressing by checking the elongation.
3. A method according to claim 1, wherein a preliminary tensioning treatment is carried out, at a force such that the tension in the reinforcement when the concrete is prestressed is a linear
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (4)
- **WARNING** start of CLMS field may overlap end of DESC **.SPECIFICATION Composite prestressing of structures The invention relates to a method of prestressing invention relates to a method of prestressing structures and to prestressed structures.In order to provide lasting prestressing forces, particularly in reinforced concrete parts, it is conventional to use steel reinforcements with a high elastic limit and a breaking strength which varies from 110 kg/mm2 to above 200 kg/mm2.These reinforcements are initially tensioned to the limit of their plastic region and are subjected to different preliminary treatments to ensure their suitability for particular applications (fatigue strength, resistance to corrosion, reduction of the loss of tensile strength).In certain cases, i.e. in cases which are called composite prestressing, tensioned prestressing reinforcements are used in addition to nontensioned reinforcements to ensure that the part of the structure has particular qualities, for example stability in the case of fire (floors, poles), or reduction of cracking (reservoirs, structures exposed to bad weather).This combination of two types of reinforcement is also found in cases where the ratio R between the maximum load needed to cause collapse and the normal working load under which the concrete part or structure cannot crack, or cracks only to a limited extent, is higher than 2, which is the approximate ratio for conventional structures subjected to bending stress.This is particularly so in the case of long, thin poles which are subjected to bending stresses in opposite directions and in which the essential role of the prestressing or of the additional reinforcements is to reduce the deformations which are likely to increase bending. This also applies to parts which may be subjected to particularly high abnormal forces, for example frameworks in seismic zones or railway-sleepers, for which the ratio R may reach values equal to or higher than 4.Finally, the combination of two categories of reinforcement is used when the main load is the action of shearing stresses in bent parts which have been prestressed according to the pretensioning method. In this case fracture by creeping of a pretensioned reinforcement acted upon by an additional tension in a crack near the support area is a dangerous phenomenon owing to its abruptness and for which the usual rules of adding reinforcing effects do not apply. It is then necessary to use non-tensioned additional reinforcements which are suitably reinforced, particularly since prestressing reinforcements with a high elastic limit generally adhere badly in the case of reinforced concrete with respect to the anchorage of excess tensions on either side of the crack.This situation applies for example to heavily loaded floors with a poor bearing surface, poles prestressed by pretensioning and embedded in their foundations and railway-sleepers.The object of the invention is to obtain a prestressing method which can be used in cases of composite prestressing, and particularly in the cases listed above, with reinforcements of a single type owing to the fact they they consist of a steel having particular properties.For this purpose the invention provides a prestressing method for cases of composite prestressing, wherein reinforcements of a single type are used whose breaking strength is between60 kg/mm2 and 120 kg/mm2, i.e. between that of usual reinforcing steels of reinforced concrete and that of steels with a high elastic limit (H.L.E.) used for prestressing.The invention also provides a prestressed structure including both prestressed and nonstressed reinforcements, both forms of reinforcement being made of the same steel which has a breaking strength in the range 60-120 kg/mm2.Other details and characteristics of the invention will be apparent from the followingdescription.In order to manufacture parts or make structures which have composite prestressing, the reinforcements of the above-mentioned special type may be subjected to supplementary treatments.In certain cases a preliminary work-hardening, tempering or other treatment is carried out, leading to a regularisation of the stress-strain curve of the steel, so as to be able to monitor the prestressing by checking the elongation.In other cases a preliminary tensioning treatment is carried out, possibly completed by a heat treatment, at a force such that the tension in the reinforcement when the concrete is prestressed is particularly a linear function of the elongation. In general, this treatment prevents loss of tensile strength, susceptibility to brittleness and to corrosion and enhances fatigue strength of the reinforcement.This preliminary tension is adapted to the residual tension required for each part or for each structure. It also depends on the manufacturing or construction methods (for example heat treatment of the concrete).CLAIMS 1. A method of composite prestressing, wherein steel reinforcements of a single type are used for both prestressed and non-stressed reinforcements, the breaking strength of the - reinforcements being between 60 kg/mm2 and120 kg/mm2.
- 2. A method according to claim 1, wherein a preliminary work-hardening; tempering or other treatment is carried out, leading to a regularisation of the stress-strain curve of the steel, so as to be abide to monitor the prestressing by checking the elongation.
- 3. A method according to claim 1, wherein a preliminary tensioning treatment is carried out, at a force such that the tension in the reinforcement when the concrete is prestressed is a linearfunction of the elongation.
- 4. A prestressed structure including both prestressed and non-stressed reinforcements, both forms of reinforcement being made of the same steel which has a breaking strength in the range 60-120 kg/mm2.Amendments to claims filed on 3rd December 1979.In claim 1 line 3 delete "breaking" and insert "ultimate tensile".
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB7935608A GB2059479B (en) | 1979-10-12 | 1979-10-12 | Composite prestressing of concrete structures |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB7935608A GB2059479B (en) | 1979-10-12 | 1979-10-12 | Composite prestressing of concrete structures |
Publications (2)
Publication Number | Publication Date |
---|---|
GB2059479A true GB2059479A (en) | 1981-04-23 |
GB2059479B GB2059479B (en) | 1983-09-28 |
Family
ID=10508495
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB7935608A Expired GB2059479B (en) | 1979-10-12 | 1979-10-12 | Composite prestressing of concrete structures |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB2059479B (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1985004203A1 (en) * | 1983-03-03 | 1985-09-26 | Leif Berntsson | Method of conferring load and deformation stability on railway tracks by means of concrete sleepers |
-
1979
- 1979-10-12 GB GB7935608A patent/GB2059479B/en not_active Expired
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1985004203A1 (en) * | 1983-03-03 | 1985-09-26 | Leif Berntsson | Method of conferring load and deformation stability on railway tracks by means of concrete sleepers |
Also Published As
Publication number | Publication date |
---|---|
GB2059479B (en) | 1983-09-28 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PCNP | Patent ceased through non-payment of renewal fee |