CN105755960A - Method for preventing middle beam of T-shaped beam bridge from generating lateral bending deformation - Google Patents

Abstract

The invention discloses a method for preventing a middle beam of a T-shaped beam bridge from generating lateral bending deformation. External pre-stressed steel bars are arranged on two lateral surfaces of the middle beam through lateral transverse partition plates and a middle transverse partition plate; and the pre-stressed steel bar of the middle beam is tensioned to designed tension force Np once after the external pre-stressed steel bars are tensioned according to the calculated tension force. According to the method, the middle beam can be effectively prevented from generating lateral bending deformation towards any side by external prestress; complicated procedure of tensioning the pre-stressed steel bar of the middle beam in cycle for a plurality of times can be omitted; the external pre-stressed steel bars are tensioned according to the calculated tension force; proper tension force can be ensured; the lateral bending deformation in construction of the middle beam can be effectively prevented; and the middle beam structure is not damaged.

Description

A kind of method preventing tee girder bridge central sill from producing lateral thrust deformation

Technical field

The present invention relates to highway bridge, particularly a kind of method preventing tee girder bridge central sill from producing lateral thrust deformation.

Background technology

Tee girder bridge is a kind of common highway bridge, and tee girder bridge, in building course, is easily generated lateral thrust deformation during the construction of its central sill, its reason is:

(1) by the impact of version: the central sill slenderness ratio of tee girder bridge is big, and lateral bending rigidity is little.

(2) by the impact of deformed bar tensioning process: the lateral dimension that central sill bottom section is " Horse hoof " shape part is less, can not at two deformed bars of beam-ends two jack simultaneous tension " Horse hoof " shape parts placed side by side, pretensioning reinforcing bar will produce lateral moment of flexure at central sill, and this lateral moment of flexure can make central sill generation lateral thrust deform.

(3) by the impact of deformed bar deviations: construction is difficult to avoid that deformed bar deviations occur, as certain side is partial to by deformed bar, this side pretensioning reinforcing bar can be caused when central sill is constructed to produce lateral moment of flexure, and this lateral moment of flexure can make central sill produce lateral thrust deformation.

Under factors above affects, such as the prestressed reinforcement of tensioning when central sill age is less, when its lateral thrust deformation extent is bigger compared with age, prestressed reinforcement of tensioning is many greatly；As long in deposited the beam time, then the lateral thrust deformation of central sill can be gradually increased with the prolongation depositing the beam time.

According to engineering statistics, the lateral thrust deformation values Δ of tee girder bridge central sill maximum up to l/700, l be tee girder bridge across footpath.

If central sill produces lateral thrust deformation, central sill can be made to produce micro-cracks, have a strong impact on construction quality and the durability of bridge.

At present, tee girder bridge construction process prevents from central sill from producing lateral thrust to deform mainly by following several method:

(1) the symmetrical deformed bar of central sill " Horse hoof " shape part adopt classification, circulation carry out stretch-draw.Namely it not single tension to the design stretching force N required_p, but it is circulated stretch-draw several times, as first by the deformed bar stretch-draw on the left side to N_pAfter/4, then move the deformed bar on the right to N_p/4；Then with N_p/ 4 stretching forces are incremented by, and circulation carries out successively, until it reaches design stretching force N_pTill.Reduce the lateral moment of flexure of central sill that asymmetric prestressed reinforcement of tensioning causes in this way.

(2) take measures to improve the accuracy of deformed bar location, reduce deviations.

(3) designing requirement post-stress reinforcing bar is reached at central sill concrete strength, can not stretch-draw too early.

(4) after stretch-draw completes, complete prefabricated central sill in factory the resting period less than 60 days；After erection, connect the diaphragm plate between each beam as early as possible, to increase its lateral confinement, it is prevented that lateral thrust deformation continues development.

Though tee girder bridge construction being taked said method can reduce the deformation of central sill lateral thrust to a certain extent, but there is techniques below problem:

(1) taking repeatedly stretching deformed bar to reduce the deformation of central sill lateral thrust, operation is numerous and diverse, affects the duration；

(2) take repeatedly stretching deformed bar to reduce the deformation of central sill lateral thrust, other unfavorable factor causing central sill lateral thrust to deform can not be eliminated, under other factors affect, once there is lateral thrust deformation, then lack the effective measures reducing lateral thrust deformation；

(3) location of deformed bar relies heavily on the technical quality of system norms and operator, even if taking measures, it is also difficult to avoid the occurrence of deviations phenomenon.

Summary of the invention

It is an object of the invention to the above-mentioned technical problem existed for prior art, it is provided that a kind of method simply, effectively preventing tee girder bridge central sill from producing lateral thrust deformation.

For achieving the above object, the method preventing tee girder bridge central sill from producing lateral thrust deformation provided by the invention, comprise the following steps:

Step 1, prefabricated tee girder bridge central sill

The structure of the central sill of tee girder bridge is: have limit diaphragm plate respectively in rear and front end, the two sides portion of central sill, middle diaphragm plate is had between the diaphragm plate of both sides, limit diaphragm plate and middle diaphragm plate are integral and vertical with the side of central sill with central sill, and its outer rim flushes with the top outer rim of central sill；Steering gear (steel pipe of a kind of bending) is had, in the plane that steering gear is vertical at same and middle beam sides with central sill barycenter at the root of limit diaphragm plate and the outboard end of middle diaphragm plate；

During by the central sill of said structure prefabricated tee girder bridge, after steering gear operation in being sequentially completed erection template, assembling reinforcement, the corrugated tube of layout central sill, pre-buried limit diaphragm plate and middle diaphragm plate, corrugated tube is worn deformed bar, then builds the concrete of central sill, limit diaphragm plate and middle diaphragm plate；

Step 2, installation and stretch-draw external prestressing reinforcing bar

After the concrete strength of step 1 reaches 90% design strength, external prestressing reinforcing bar is worn in the steering gear of the limit diaphragm plate in central sill both sides and middle diaphragm plate respectively, the two ends of external prestressing reinforcing bar are temporarily anchored on the diaphragm plate of limit after stretch-draw by then simultaneous tension；

The stretching force F of external prestressing reinforcing bar_pTried to achieve by following formula:

$F_p=\frac{3E_c{I}_{xx}}{87500l^{2}cos\frac{\mathrm{\θ}}{2}}\left(kN\right)$

In formula

E_c: central sill is adopted concrete elastic modelling quantity (MPa)；

I_xx: the lateral bending rigidity (mm of central sill⁴)；

θ: external prestressing reinforcing bar is at the angle (rad) of steering gear place of middle diaphragm plate；

L: central sill across footpath (mm)；

Step 3, stretch-draw central sill deformed bar

After completing step 2, by disposable for central sill deformed bar stretch-draw to design stretching force；

Step 4, lifting construction

The central sill hoisted in position of step 3 will be completed, carry out transverse splicing by building wet joint concrete, make central sill laterally be retrained by limit diaphragm plate and middle diaphragm plate, it is impossible to occur lateral thrust to deform again, then external prestressing reinforcing bar is removed, complete the constructing operation of tee girder bridge central sill.

Compared with prior art, the invention has the beneficial effects as follows:

(1) by arranging external prestressing reinforcing bar in central sill both sides and applying stretching force F simultaneously_p, can effectively prevent central sill from deforming to either side generation lateral thrust in construction.

(2) tee girder bridge central sill deformed bar can single tension to design stretching force, save repeatedly numerous and diverse operation of circulation stretch-draw, make construction simple, quick, construction period shortens.

(3) according to the stretching force F calculated_pValue stretch-draw external prestressing reinforcing bar, it can be ensured that stretching force size to fit, can effectively prevent central sill lateral thrust from deforming, will not center sill structure be caused damage again.

(4) external prestressing reinforcing bar used by can have enough to meet the need use, saves Master Cost.

Accompanying drawing explanation

Fig. 1 is the tee girder bridge center sill structure side view after stretch-draw external prestressing reinforcing bar of the present invention；

Fig. 2 is C-C sectional drawing in Fig. 1；

Fig. 3 is A-A sectional drawing in Fig. 1；

Fig. 4 is B-B sectional drawing in Fig. 1.

In figure: 1 central sill, 2 limit diaphragm plates, 3 middle diaphragm plates, 4 external prestressing reinforcing bars, 5 steering gears, 6 central sill barycenter.

Detailed description of the invention

Below in conjunction with drawings and Examples, the present invention will be further described.

The present embodiment prevents central sill generation lateral thrust deformation in certain freely-supported tee girder bridge construction process for adopting the inventive method.

In conjunction with Fig. 1 to Fig. 4, this freely-supported tee girder bridge, central sill 1 across footpath l=47000mm, central sill adopts C50 concrete, the concrete elastic modulus E of C50_c=3.45 × 104MPa, the lateral bending rigidity I of central sill_xx=7.84 × 10¹⁰(mm⁴), central sill has N1～N5 deformed bar 5, designs stretching force N_pIt is 3710.7kN.

Prevent the construction that central sill generation lateral thrust deforms from carrying out in the steps below:

Step 1, prefabricated central sill

As shown in Figure 1, the structure of central sill 1 is: having thickness on the central sill two sides from its rear and front end 8.5m respectively is the limit diaphragm plate 2 that 60cm, outer rim vertical with middle beam sides integral with central sill, vertical flushes with central sill top outer rim, and there is the middle diaphragm plate 3 that a size and structure are identical with limit diaphragm plate diaphragm plate middle, both sides.

During central sill prefabricated by said structure, it is sequentially carried out erection template；The reinforcing bar of colligation central sill and limit diaphragm plate and middle diaphragm plate in a template；Arrange central sill corrugated tube；On the limit diaphragm plate reinforcing bar of colligation from 23cm place, middle web side and on the middle diaphragm plate reinforcing bar of colligation from the pre-buried steering gear 5 passed through for external prestressing reinforcing bar respectively of 63cm place, middle web side, and make steering gear with central sill barycenter 6 in the same plane vertical with middle beam sides, the transverse height difference e=400mm of the steering gear of steering gear and the limit diaphragm plate of diaphragm plate in the middle of now；Then in corrugated tube, wear central sill deformed bar；Finally build the concrete of central sill, limit diaphragm plate and middle diaphragm plate.

Calculating external prestressing reinforcing bar in the angle theta of steering gear place of middle diaphragm plate according to the middle steering gear of diaphragm plate with the transverse height difference e of steering gear of limit diaphragm plate and the distance of two limit diaphragm plates is 176.9 °, θ/2=1.543744 (rad).

Step 2, installation and stretch-draw external prestressing reinforcing bar

After concrete strength reaches 90% design strength, external prestressing reinforcing bar 4 is worn in the steering gear of the limit diaphragm plate in central sill both sides and middle diaphragm plate respectively, and utilizes jack simultaneous tension both sides external prestressing reinforcing bar,

The stretching force of external prestressing reinforcing bar is:

$F_p=\frac{3E_c{I}_{xx}}{87500l^{2}cos\frac{\mathrm{\θ}}{2}}=\frac{3\×3.45\×{10}^4\×7.84\×{10}^{10}}{87500\×{47000}^2\×cos\left(1.543744\right)}=1552\left(kN\right)$

After stretch-draw, the two ends of external prestressing reinforcing bar are temporarily anchored on the diaphragm plate of limit respectively.

Step 3, stretch-draw central sill deformed bar

After completing step 2, according to a conventional method by the disposable stretch-draw of N1～N5 deformed bar of central sill to design stretch-draw force value 3710.7kN.

Step 4, lifting construction

By the central sill hoisted in position after deformed bar stretch-draw, carry out transverse splicing by building wet joint concrete, make central sill laterally be retrained by limit diaphragm plate and middle diaphragm plate, it is impossible to occur lateral thrust to deform again, then external prestressing reinforcing bar is removed, complete the constructing operation of tee girder bridge central sill.

Claims (1)

1. one kind prevents the method that tee girder bridge central sill produces lateral thrust deformation, it is characterised in that comprise the following steps:

Step 1, prefabricated tee girder bridge central sill

The structure of the central sill (1) of tee girder bridge is: have limit diaphragm plate (2) respectively in rear and front end, the two sides portion of central sill, middle diaphragm plate (3) is had between the diaphragm plate of both sides, limit diaphragm plate and middle diaphragm plate are integral with central sill, and vertical with the side of central sill, its outer rim flushes with the top outer rim of central sill；Steering gear (5) is had, in the plane that steering gear is vertical at same and middle beam sides with central sill barycenter (6) at the root of limit diaphragm plate and the outboard end of middle diaphragm plate；

During by the central sill of said structure prefabricated tee girder bridge, after steering gear operation in being sequentially completed erection template, assembling reinforcement, the corrugated tube of layout central sill, pre-buried limit diaphragm plate and middle diaphragm plate, corrugated tube is worn deformed bar, then builds the concrete of central sill, limit diaphragm plate and middle diaphragm plate；

Step 2, installation and stretch-draw external prestressing reinforcing bar

After the concrete strength of step 1 reaches 90% design strength, external prestressing reinforcing bar (4) is worn in the steering gear of the limit diaphragm plate in central sill both sides and middle diaphragm plate respectively, the two ends of external prestressing reinforcing bar are temporarily anchored on the diaphragm plate of limit after stretch-draw by then simultaneous tension；

The stretching force F of external prestressing reinforcing bar_pTried to achieve by following formula:

$F_p=\frac{3E_c{I}_{xx}}{87500l^{2}cos\frac{\mathrm{\θ}}{2}}$

In formula

E_c: central sill is adopted concrete elastic modelling quantity；

I_xx: the lateral bending rigidity of central sill；

θ: external prestressing reinforcing bar is at the angle of steering gear place of middle diaphragm plate；

L: central sill across footpath；

Step 3, stretch-draw central sill deformed bar

After completing step 2, by disposable for central sill deformed bar stretch-draw to design stretching force；

Step 4, lifting construction

The central sill hoisted in position of step 3 will be completed, carry out transverse splicing by building wet joint concrete, make central sill laterally be retrained by limit diaphragm plate and middle diaphragm plate, it is impossible to occur lateral thrust to deform again, then external prestressing reinforcing bar is removed, complete the constructing operation of tee girder bridge central sill.