CN110761202A - Prestress applying method in pre-pressing construction process - Google Patents
Prestress applying method in pre-pressing construction process Download PDFInfo
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- CN110761202A CN110761202A CN201810829028.4A CN201810829028A CN110761202A CN 110761202 A CN110761202 A CN 110761202A CN 201810829028 A CN201810829028 A CN 201810829028A CN 110761202 A CN110761202 A CN 110761202A
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
- E01D22/00—Methods or apparatus for repairing or strengthening existing bridges ; Methods or apparatus for dismantling bridges
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Abstract
The invention belongs to the field of bridge construction, and aims to provide a prestress application method in a pre-pressing construction process capable of reducing cracks generated on the lower edge of a bridge, which has the technical scheme that the prestress application method in the pre-pressing construction process comprises the following steps: dismantling the original mid-span hanging hole concrete box girder, and prepressing the mid-span steel box girder; checking whether the pre-pressure applied to the span middle section box girder is stable; and (5) solidifying the midspan steel box girder after the pre-pressure is detected to be stable. In the prior art, the lower edge of the section of a concrete box girder is usually reinforced; in this scheme, carry out the pre-compaction to striding well steel box girder in advance for striding well steel box girder when concreting, just can bear the pressure of certain degree, cracked possibility reduction appears in two adjacent concrete box girder cross-section lower edges, and the construction degree of difficulty is littleer, can also shorten construction cycle. The invention is suitable for bridge construction working conditions.
Description
Technical Field
The invention relates to midspan steel box girder construction, in particular to a prestress applying method in a pre-pressing construction process.
Background
The steel box girder is a common structural form for a large-span bridge and is generally used for a bridge with a large span. When the steel box girder is installed, the steel box girder is mostly added on the existing or original bridge, and the steel box girder is solidified with the existing or original bridge.
In the work progress, when carrying out the system conversion, the primary structure is that the T of taking the string roof beam constructs the case roof beam, needs to demolish original midspan hanging hole concrete case roof beam, changes for steel construction case roof beam to make the connection of steel construction section and old bridge, reach the effect that the steel constructs in succession. Continuous steel structure refers to the three-directional deformation coordination of the connection points.
However, the original T-beam is changed into a continuous steel bridge, which increases the overall rigidity of the bridge, but the middle part of the bridge span after the continuous steel structure generates a certain positive bending moment, and the prestressed steel bundles of the T-beam are arranged on the upper edge of the cross section and mainly used for resisting the negative bending moment of the upper edge, so that certain measures are required to be taken to resist the middle positive bending moment, and if the middle connection part is simply and rigidly connected, a certain positive bending moment is generated on the lower edge of the cross section at the connection position, so that the concrete at the lower edge cracks.
Disclosure of Invention
The invention aims to provide a prestress applying method in a pre-pressing construction process, which has the advantage of reducing the possibility of generating cracks on lower edge concrete.
The technical purpose of the invention is realized by the following technical scheme:
a prestress applying method in a pre-pressing construction process comprises the following steps: the method comprises the following steps:
s1: the original mid-span hanging hole concrete box girder is dismantled,
s2: prepressing the midspan steel box girder;
s3: checking whether the pre-pressure applied to the span middle section box girder is stable;
s4: and (5) solidifying the midspan steel box girder after the pre-pressure is detected to be stable.
By adopting the technical scheme, in the prior art, if the defects of cracks and the like appear on the lower edges of the sections of the two adjacent concrete box girders at the joint, the lower edges of the sections of the concrete box girders are usually reinforced; in this scheme, carry out the pre-compaction to striding well steel box girder in advance for striding well steel box girder when concreting, just can bear the pressure of certain degree, cracked possibility reduction appears in two adjacent concrete box girder cross-section lower edges, and the construction degree of difficulty is compared in the later stage and is repaired littleer, and compare in later stage repair period longer, can also shorten construction period.
Furthermore, when the midspan hanging hole concrete box girder is dismantled, the original bridge parts on the two sides of the midspan hanging hole concrete box girder are reserved, and the end face of the bridge is polished to be flat.
Through adopting above-mentioned technical scheme, the bridge terminal surface is more level and more smooth, and during later stage butt joint concreties, paste more tightly between original bridge and the newly-increased steel box girder of striding, and the clearance between the two is littleer, is more convenient for obtain reliable and stable consolidation structure.
Further, the pre-pressure is always output until the midspan steel box girder is solidified, and the pre-pressure is removed.
By adopting the technical scheme, the midspan steel box girder can be always subjected to the prepressing action of the prepressing force, the state of the midspan steel box girder is stable in the construction process, the prepressing force simulates the working condition when the external force is borne in the later period, after the prepressing force is removed, the external force borne by the midspan steel box girder is reduced, compared with the midspan steel box girder installed by the conventional method, the damaged critical value of the structure installed by the prepressing method is larger than the conventional damaged critical value, and the size deviation of the two is the value close to the size of the prepressing force.
Further, the method for determining the magnitude of the pre-pressure comprises the following steps: when the tensile stress of the lower edge of the concrete section is reduced to the limit value of the tensile stress which can be borne by the concrete, the magnitude of the applied pre-pressure is the maximum value.
By adopting the technical scheme, when pressure is continuously applied, the pre-pressure is continuously increased, and the defects of cracks and the like can be pressed out from the lower edges of the concrete sections of the midspan steel box girder and the original bridge, so that the damage is caused. Therefore, the pre-pressure is set to a damage critical value, namely, the possibility of cracks can be reduced, and the pressure resistance of the whole structure can be improved to the maximum extent within an allowable range.
And further, pre-pressing the midspan steel box girder until the tensile stress output value of the midspan steel box girder is kept stable, and determining that the pre-pressing is stable at the moment.
By adopting the technical scheme, the output of the pre-pressure ensures that the state of the midspan steel box girder is kept stable so as to facilitate construction; when the output value of the pre-pressure has large deviation, the stress on the midspan steel box girder is unstable, so that the midspan steel box girder is unstable; when the pre-pressure is stably output, the tensile stress corresponding to the pre-pressure generated on the midspan steel box girder and the force for balancing the two forces between the midspan steel box girder and the pre-pressure can balance the pre-pressure and the working condition of the midspan steel box girder, so that the whole structure tends to be balanced and is convenient to construct.
Further, the state that the tensile stress output value is kept stable comprises the following steps: no deviation and deviation value less than five thousandths of tensile stress.
Through adopting above-mentioned technical scheme, ideal state when there is not the deviation, it is the actual state to have the deviation value, so the deviation value is in certain extent, does not cause the influence to whole steel box girder striding in, can be accepted.
Furthermore, the midspan steel box girder is consolidated, and the acting force position of the pre-pressure on the midspan steel box girder are kept unchanged in the consolidation process.
By adopting the technical scheme, the midspan steel box girder can be enabled to tend to a stable state as soon as possible only when the magnitude and the position of the pre-pressure are unchanged.
Furthermore, the consolidation mode adopts the modes of welding reinforcing ribs and building cement concrete.
By adopting the technical scheme, the cement concrete building is a common reliable means, and on the basis of the cement concrete building, the reinforcing structure of the reinforcing ribs can improve the connecting strength between the original bridge and the newly-added midspan steel box girder.
In conclusion, the invention has the following beneficial effects:
1. by increasing the pre-pressure stably acting on the midspan steel box girder in advance, the critical value of the midspan steel box girder can be continuously increased on the basis of the critical value which can bear the external force originally, and the possibility of cracks at the lower connecting edge between the original bridge and the newly-added midspan steel box girder is reduced in the using process and the construction process.
Drawings
FIG. 1 is a schematic structural view for embodying a first step of a construction step;
FIG. 2 is a schematic structural view for embodying a second step of the construction step;
FIG. 3 is a schematic structural view for embodying the third step of the construction step.
In the figure, 1, a steel box girder is spanned; 2. an original bridge; 3. and (4) bolts.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
In which like parts are designated by like reference numerals. It should be noted that the terms "front," "back," "left," "right," "upper" and "lower" used in the following description refer to directions in the drawings, and the terms "bottom" and "top," "inner" and "outer" refer to directions toward and away from, respectively, the geometric center of a particular component.
A prestress applying method in a pre-pressing construction process is mostly applied to the condition of folding construction of two structures when a T-structure bridge convertible system is a steel structure bridge.
When the system is converted, the original midspan hanging hole concrete box girder is firstly dismantled and replaced by the steel structure box girder, and the steel structure is connected with the original bridge structure, so that the effect of continuous rigid frame is achieved. Although the overall rigidity of the bridge can be improved by adopting the steel structure box girder, the bridge span middle part can generate certain positive bending moment after continuous steel structure, taking the frame girder as an example, the support seat of the frame girder receives negative bending moment, and the span middle of the frame girder receives positive bending moment, so that the span middle edge of the bridge is subjected to positive bending moment, and in order to reduce the influence of the positive bending moment on the bridge lower edge, the bridge lower edge concrete is cracked, and pre-pressing construction is adopted.
When prestress is applied by adopting a prepressing method, firstly, prepressing the midspan steel box girder 1;
the prepressing steps are as follows:
the magnitude of the pre-pressure is based on the principle that the tensile stress of the lower edge of the concrete section of the connecting section is reduced to be within the maximum limit of the tensile stress of the labeled concrete; that is, when the tensile stress of the lower edge of the concrete section is reduced to the limit value of the tensile stress that the concrete can bear, the magnitude of the pre-pressure applied at this time is the maximum value.
And pre-pressing the midspan steel box girder 1 to the state of the midspan steel box girder 1, keeping the size of the output tensile stress stable, and selecting five thousandths of the tensile stress as an allowable error range in the range with extremely small deviation or without deviation. The pre-compression is considered to be stable at this time.
And then, the midspan steel box girder is consolidated, and the consolidation mode comprises the following steps:
the newly installed midspan steel box girder 1 is welded with the metal framework in the original bridge, so that the adjacent sections of the newly installed midspan steel box girder 1 and the metal framework are attached to each other, and then the midspan steel box girder 1 and the original metal framework are cast into a whole by adopting cement concrete.
In the process of consolidation, the prepressing force on the midspan steel box girder 1 is always kept until the cement concrete is completely dried after the consolidation is finished, and then the prepressing force is removed. In order to enable the bridge deck to achieve the expected construction effect, the acting force and the acting force position on the midspan steel box girder 1 are always kept unchanged in the process of the pre-pressure consolidation.
The consolidation mode adopts the modes of welding reinforcing ribs and building cement concrete. If the reinforcing steel bar reinforcing ribs are reserved at the two ends of the bridge, the midspan steel box girder 1 with the reinforcing steel bar reinforcing ribs is adopted, the reinforcing steel bars extend out of the end face of the midspan steel box girder 1, the reinforcing steel bars on the original bridge 2 and the reinforcing steel bars on the midspan steel box girder 1 are welded, and then cement concrete is adopted for pouring and solidifying to realize connection.
If the end face of the bridge is smooth, the bridge is directly concreted and consolidated by adopting cement concrete
And after the pre-pressure is removed, carrying out bridge deck system construction on the bridge deck.
In the overall construction steps, as shown in fig. 1, firstly, a midspan steel box girder 1 is placed at a prestressed concrete box girder of an original bridge 2, and then the midspan steel box girder 1 is pre-pressed, so that the pre-pressure is F, and the pre-pressure direction is vertically downward; in order to keep stable output of the pre-pressure, in this embodiment, the cement concrete block is used as a pre-pressure source, and the cement concrete block is placed right above the midspan steel box girder, so that the self weight of the cement concrete block continuously and stably applies the pre-pressure;
secondly, as shown in figure 2, anchoring and connecting the midspan steel box girder 1 and the original bridge 2, wherein a plurality of bolts 3 penetrate through the midspan steel box girder 1 and the prestressed concrete box girder of the original bridge 2 to be fixedly connected; if the reinforcing ribs extend out, welding the connection between the reinforcing ribs; coating cement concrete on the other parts for building;
and thirdly, as shown in fig. 3, removing the pre-pressing external load and finishing the construction. The bolts 3 of the anchor connection are left in the construction position.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.
Claims (8)
1. A prestress applying method in a pre-pressing construction process comprises the following steps: the method comprises the following steps:
s1: the original mid-span hanging hole concrete box girder is dismantled,
s2: prepressing the midspan steel box girder (1);
s3: checking whether the pre-pressure applied to the span middle section box girder is stable;
s4: and (3) solidifying the midspan steel box girder (1) after the pre-pressure is detected to be stable.
2. The prestress applying method in the pre-compaction construction process according to claim 1, wherein: when the midspan hanging hole concrete box girder is dismantled, the original bridge (2) parts on the two sides of the midspan hanging hole concrete box girder are reserved, and the end face of the bridge is polished to be flat.
3. The prestressing method in a pre-compaction construction process according to claim 1, wherein: and the pre-pressure is always kept output until the middle-span steel box girder (1) is solidified, and the pre-pressure is removed.
4. The prestressing method in a pre-compaction construction process according to claim 1, wherein: the method for determining the magnitude of the pre-pressure comprises the following steps: when the tensile stress of the lower edge of the concrete section is reduced to the limit value of the tensile stress which can be borne by the concrete, the magnitude of the applied pre-pressure is the maximum value.
5. The prestressing method in a pre-compaction construction process according to claim 1, wherein: and pre-pressing the midspan steel box girder (1) until the tensile stress output value of the midspan steel box girder (1) is stable, and determining that the pre-pressing is stable at the moment.
6. The prestressing method in the pre-compaction construction process according to claim 5, wherein: the state that the tensile stress output value is kept stable comprises the following steps: no deviation and deviation value less than five thousandths of tensile stress.
7. The prestressing method in a pre-compaction construction process according to claim 1, wherein: and (3) solidifying the midspan steel box girder (1), wherein the acting force and the acting force position of the pre-pressure on the midspan steel box girder (1) are kept unchanged in the solidifying process.
8. The prestressing method in a pre-compaction construction process according to claim 1, wherein: the consolidation mode adopts the modes of welding reinforcing ribs and building cement concrete.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201810829028.4A CN110761202A (en) | 2018-07-25 | 2018-07-25 | Prestress applying method in pre-pressing construction process |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201810829028.4A CN110761202A (en) | 2018-07-25 | 2018-07-25 | Prestress applying method in pre-pressing construction process |
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| CN110761202A true CN110761202A (en) | 2020-02-07 |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2683604B2 (en) * | 1995-08-21 | 1997-12-03 | 富士千橋梁土木株式会社 | Floor slab edge cutting device and floor slab edge cutting method |
| CN1587531A (en) * | 2004-06-30 | 2005-03-02 | 清华大学 | Method for anti-cracking in hogging moment area of steel-concrete combined beam |
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2018
- 2018-07-25 CN CN201810829028.4A patent/CN110761202A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2683604B2 (en) * | 1995-08-21 | 1997-12-03 | 富士千橋梁土木株式会社 | Floor slab edge cutting device and floor slab edge cutting method |
| CN1587531A (en) * | 2004-06-30 | 2005-03-02 | 清华大学 | Method for anti-cracking in hogging moment area of steel-concrete combined beam |
| CN105421252A (en) * | 2015-11-20 | 2016-03-23 | 同济大学 | Bridge seamless broadening joint crack based on two-dimension prestress and implement method thereof |
| CN106320192A (en) * | 2016-10-27 | 2017-01-11 | 武汉理工大学 | Beam section replacement reinforcement method for large-span concrete continuous beam bridge |
| CN107988924A (en) * | 2017-12-11 | 2018-05-04 | 兰州理工大学 | A kind of steel based on re-building of old bridge-mixed composite beam bridge system transform system and conversion method |
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