CN105696451A - Main girder bottom plate structure of wide box-girder bridge capable of preventing bottom plate from cracking and construction method thereof - Google Patents

Abstract

The invention provides a main girder bottom plate structure of a wide box-girder bridge capable of preventing a bottom plate from cracking. Bottom plate thickening cross beams are arranged at the upper part of the bottom plate with embedded bottom plate prestressed reinforcing steel bar segments at intervals along the axial direction of a bridge; steel plates corresponding to the bottom plate thickening cross beams are arranged on the bottom surface of the bottom plate; and vertical prestressed reinforcing steel bars made up of finish rolling twisted steel are arranged in the bottom plate thickening cross beams and the bottom plate, extend out from the upper ends of the bottom plate thickening cross beams and the lower ends of the steel plates and are respectively fixed by nuts. During construction, the vertical prestressed reinforcing steel bars are stretched and drawn in a manner of screwing the nuts at the lower ends of the vertical prestressed reinforcing steel bars, and the elongation amount of the vertical prestressed reinforcing steel bars is controlled by a calculated value. The rigidity of the main girder bottom plate is reinforced through the bottom plate thickening cross beams, the radial force to the bottom plate, caused by stretching and drawing the bottom plate prestressed reinforcing steel bars, is counteracted by using the vertical prestressed reinforcing steel bars, and the combination of both can effectively prevent the main girder bottom plate from cracking during construction and after the bridge comes into service.

Description

Wide box girder bridge girder base arrangement and the construction method thereof of Bottom slab breaking can be prevented

Technical field

The present invention relates to highway bridge, particularly a kind of wide box girder bridge girder base arrangement preventing Bottom slab breaking and construction method thereof。

Background technology

Wide box beam bridge of the present invention refers to single box single chamber prestressed concrete continuous beam and the prestressed concrete continuous rigid-framed bridge of 1/50～1/20 that base plate average thickness (meansigma methods of girder span centre place base plate thickness and girder root place base plate thickness sum) is baseplate width。

Because of following reason, the girder of this wide box beam bridge causes that its base plate easily bursts apart after putting into effect with bridge in construction:

Girder is less at span centre and fulcrum place, limit height, relatively big at central bearing point place height, and the deck-molding at central bearing point place generally with the parabolic deck-molding transition to span centre and fulcrum place, limit, makes base plate form curved surface (see Fig. 1)。Baseboard prestress steel bar arrangement is in base plate, and the layout shape on its facade is similar to base plate, also curvilinear。Curved baseboard prestress reinforcing bar is with stretching force N_pBase plate being produced radial force (see Fig. 2) after stretch-draw, because base plate average thickness is too small with the ratio of baseplate width, the slenderness ratio of base plate is excessive, makes foolrstiffness not enough, and under the radial force effect of baseboard prestress reinforcing bar, base plate is susceptible to burst apart。

Prevent the traditional method of wide box beam bridge Bottom slab breaking, be arrange at base plate to prevent collapsing reinforcing bar。The method there is the problem that one is that the anti-design collapsing reinforcing bar lacks foundation, and including anti-collapsing the spacing whether reinforcing bar arrange, arrange, anti-reinforcing bar grade and the diameter etc. collapsing reinforcing bar used all specify without direct；Two is prevent in construction that collapsing reinforcing bar is difficult to clasp completely the corrugated tube of baseboard prestress reinforcing bar, not easily plays a role；Three is to solve the problem that base plate stiffness by itself is not enough。

Summary of the invention

For the above-mentioned traditional method Problems existing preventing wide box beam bridge Bottom slab breaking, it is an object of the invention to provide a kind of wide box girder bridge girder base arrangement that can effectively prevent Bottom slab breaking and construction method thereof。

The wide box girder bridge girder base arrangement preventing Bottom slab breaking provided by the invention, be equipped with the base plate top of baseboard prestress lengths of rebar along along bridge to there being spaced base plate to thicken crossbeam, having in the bottom surface of base plate and thicken, with base plate, the steel plate that crossbeam is corresponding up and down, the bottom surface of end face and steel plate that base plate thickeies crossbeam is the level of state；The duct having correspondence spaced apart, upper and lower in crossbeam and base plate is thickeied at base plate, being installed with the vertical prestressed reinforcement being made up of finish rolling deformed bar in duct, vertical prestressed reinforcement stretches out the upper end of base plate thickening crossbeam to be fixed by nut respectively with the lower end stretching out steel plate。

Described base plate thicken crossbeam along along bridge to mutual spacing s_vSpan be: 150cm≤s_v≤ 300cm；Base plate thickeies the centre-height d of crossbeam₂Span be: (K/15-d_j)≤d₂≤(K/10-d_j), in formula, K is baseplate width, d_jFor base plate average thickness。

The construction method of above-mentioned wide box girder bridge girder base arrangement comprises the following steps:

Step 1, build girder

After design erection template and assembling reinforcement (including girder and the reinforcing bar of base plate thickening crossbeam), build girder and the concrete of base plate thickening crossbeam, simultaneously at the bottom surface pre-embedded steel slab of base plate, reserved duct corresponding up and down in crossbeam and base plate is thickeied, the reserved boring corresponding with this duct in steel plate at base plate；

Step 2, installation and stretch-draw vertical prestressed reinforcement

When the concrete strength of step 1 reaches 90% design strength, vertical prestressed reinforcement is thickeied through base plate by root the boring of duct reserved in crossbeam and base plate and steel plate, utilizes the nut of vertical prestressed reinforcement upper end that the upper end of vertical prestressed reinforcement is fixed on base plate and thicken the top (nut and base plate thicken and put steel washer between crossbeam) of crossbeam；The nut of vertical prestressed reinforcement lower end is screwed with finger, itself and surface of steel plate is made to be adjacent to, with finger normal forces can not continue to screw vertical prestressed reinforcement time its lower end stretch out the length of nut for benchmark, continue the mode screwing the nut of vertical prestressed reinforcement lower end with screwing tool and vertical prestressed reinforcement is carried out stretch-draw, measure vertical prestressed reinforcement lower end simultaneously and stretch out the value added of nut length, this value added is defined as vertical prestressed reinforcement stretching extension value, stretch-draw vertical prestressed reinforcement is stopped when vertical prestressed reinforcement stretching extension value reaches limit value Δ；

Limit value Δ is tried to achieve by following formula:

$\begin{array}{cc}\mathrm{\Δ}=\frac{{\mathrm{\σ}}_{con}{A}_p{s}_v}{{\mathrm{nrE}}_s{A}_{pv}}(d_1+d_2)& \left(mm\right)\end{array}$

In formula

σ_con: the design tension stress (MPa) of baseboard prestress reinforcing bar,

A_P: the total cross-sectional area (mm of baseboard prestress reinforcing bar²),

s_v: base plate thicken crossbeam along along bridge to mutual spacing (m),

N: thicken the vertical prestressed reinforcement limb number on crossbeam at same base plate,

R: the circular curve radius (m) of base plate, when for other curve form, according toCalculating is taken, and wherein l is curve chord length, and β is the ratio of curve rise f and chord length l,

E_s: the elastic modelling quantity (MPa) of vertical prestressed reinforcement (5),

A_pv: the area of section (mm of single limb vertical prestressed reinforcement²),

d₁: base plate thickness (mm),

d₂: base plate thickeies the centre-height (mm) of crossbeam；

Step 3, stretch-draw baseboard prestress reinforcing bar

After the whole stretch-draw of all vertical prestressed reinforcement, stretch-draw baseboard prestress reinforcing bar, complete the construction of wide box girder bridge girder base arrangement。

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

(1) thickening crossbeam by base plate makes the rigidity of base plate strengthen；The stretch-draw baseboard prestress reinforcing bar radial force to base plate can be offset by vertical prestressed reinforcement, the two combine, can effectively prevent base plate when stretch-draw baseboard prestress reinforcing bar and bridge put into effect after burst apart。

(2) during stretch-draw vertical prestressed reinforcement, the limit value Δ calculated according to computing formula controls vertical prestressed reinforcement stretching extension value, the prestressing force that vertical prestressed reinforcement produces can be made just to offset the radial force that baseboard prestress reinforcing bar produces, play the effect effectively preventing base plate from bursting apart, because of excessive stretch-draw, base arrangement will not be caused damage again。

Accompanying drawing explanation

Fig. 1 is the side view of wide box girder bridge girder of the present invention；

Fig. 2 is baseboard prestress reinforcing bar radial force schematic diagram；

Fig. 3 is base plate curve chord length l and rise f schematic diagram；

Fig. 4 is along girder longitudinal direction partial sectional view；

Fig. 5 is A-A sectional drawing in Fig. 4；

Fig. 6 is B enlarged drawing in the middle part of Fig. 4。

In figure: 1 girder, 2 base plates, 3 baseboard prestress reinforcing bars, 4 steel washers, 5 vertical prestressed reinforcement, 6 base plates thicken crossbeam, 7 ducts, 8 steel plates, 9 nuts。

Detailed description of the invention

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

As it is shown in figure 1, the present embodiment can prevent the wide box beam bridge of Bottom slab breaking from being prestressed concrete continuous rigid-framed bridge, its base plate 2 is curved surface, and the baseboard prestress reinforcing bar 3 being placed in base plate is also curvilinear。The span of the girder 1 of wide box beam bridge is 90m, span centre deck-molding 2.2m, central bearing point place deck-molding 5.5m。Baseplate width K=1200cm；Base plate thickness is 25cm at span centre KZ place, and base plate thickness is 50cm at girder root GB place, base plate average thickness d_j=37.5cm, for the 1/32 of baseplate width, belongs to wide box beam bridge。The base plate thickness being equipped with baseboard prestress reinforcing bar is cumulative to 37.0cm by 25.0cm。

As it is shown on figure 3, span centre base plate curve chord length l=84.0m, the deck-molding of span centre and central bearing point can obtain, rise f=5.5-2.2=3.3m, try to achieve the circular curve radius of base plate

$r=\frac{l}{2}(\frac{1}{4\mathrm{\β}}+\mathrm{\β})=\frac{84}{2}\×(\frac{1}{4\×\frac{3.3}{84}}+\frac{3.3}{84})=268.9m$

As shown in Figure 4, being provided with 16 hole baseboard prestress reinforcing bars on base plate altogether, the area of section of the baseboard prestress reinforcing bar in single duct is 2919mm², the total cross-sectional area of 16 hole baseboard prestress reinforcing bars is A_P=46704mm², the design tension stress σ of baseboard prestress reinforcing bar_con=1395MPa (the stretching force N of baseboard prestress reinforcing bar shown in Fig. 2_pCorresponding)。

As in figure 2 it is shown, curved baseboard prestress reinforcing bar is with stretching force N_pBase plate can be produced radial force after stretch-draw。Because base plate average thickness is too small with the ratio of baseplate width, the slenderness ratio of base plate is excessive, makes foolrstiffness not enough, and after construction neutralization bridge puts into effect, under the radial force effect that stretch-draw baseboard prestress reinforcing bar produces, base plate is susceptible to deformation of bursting apart。

As shown in Figure 4, Figure 5 and Figure 6, for preventing base plate from bursting apart, build on base plate top along bridge longitudinal direction mutual spacing s_vThe base plate of=2.5m thickeies crossbeam 6, and it is that class is trapezoidal that base plate thickeies section of beam, and base plate thickeies crossbeam centre-height d₂=55cm, when building, the Q235C shape steel plate 8 of pre-buried thick 20mm, wide 10cm in the bottom surface of base plate, and make the end face of base plate thickening crossbeam and the bottom surface of steel plate be the level of state。Thicken 4 ducts 7 utilizing metal bellows reserved mutual spacing 3200mm, 4400mm, 3200mm in crossbeam and base plate at base plate, wherein the duct of both sides is positioned at base plate and thickeies the two ends of crossbeam, processes the boring corresponding with this duct in steel plate；With the PSB785 finish rolling deformed bar that diameter is 18mm as vertical prestressed reinforcement 5 (its elastic modulus E_s=2.0 × 10⁵Mpa, the area of section A of single limb vertical prestressed reinforcement_pv=254.4mm²), it being each passed through base plate and thicken the duct in crossbeam and base plate and the boring in steel plate, its upper end stretching out base plate thickening crossbeam is fixed with nut 9 respectively with the lower end stretching out steel plate, and same base plate thickeies the vertical prestressed reinforcement limb number n=4 on crossbeam。

The girder of said structure is constructed according to the following steps:

Step 1, build girder

After design erection template and assembling reinforcement, build girder and the concrete of base plate thickening crossbeam, the pre-buried described steel plate in the bottom surface of base plate simultaneously, thicken reserved described duct in crossbeam and base plate at base plate, steel plate processes the boring corresponding with this duct；

Step 2, installation and stretch-draw vertical prestressed reinforcement

When the concrete strength of step 1 reaches 90% design strength, vertical prestressed reinforcement is thickeied through base plate the boring of duct reserved in crossbeam and base plate and steel plate, the upper end of vertical prestressed reinforcement is fixed on base plate and thickeies crossbeam top by the nut and the steel washer 4 that utilize vertical prestressed reinforcement upper end, the nut of vertical prestressed reinforcement lower end is screwed with finger, itself and surface of steel plate is made to be adjacent to, when finger normal forces can not continue to screw vertical prestressed reinforcement, the length of nut is stretched out for benchmark with now vertical prestressed reinforcement lower end, continue the mode screwing the nut of vertical prestressed reinforcement lower end with screwing tool and vertical prestressed reinforcement is carried out stretch-draw, measure vertical prestressed reinforcement lower end with the electronic digital indicator that precision is 0.01mm simultaneously and stretch out the value added of nut length, this value added is defined as vertical prestressed reinforcement stretching extension value, stretch-draw vertical prestressed reinforcement is stopped when vertical prestressed reinforcement stretching extension value reaches its limit value Δ。

For shown in Fig. 4 section base plate, to 1#～11# totally 11 base plates being had to thicken crossbeam by section base plate, each base plate thickeies has 4 vertical prestressed reinforcement (as shown in Figure 5) on crossbeam, and corresponding 1#～11# base plate thickeies the base plate thickness d of crossbeam₁Substitute in following formula:

$\mathrm{\Δ}=\frac{{\mathrm{\σ}}_{con}{A}_p{s}_v}{{\mathrm{nrE}}_s{A}_{pv}}(d_1+d_2)=\frac{1395\×46704\×2.5}{4\×268.9\×2.0\×{10}^5\×254.5}\×(d_1+550)$

1#～11# the base plate calculating correspondence thickeies the vertical prestressed reinforcement stretching extension value limit value Δ such as following table on crossbeam:

Base plate thickeies crossbeam numbering	1#	2#	3#	4#	5#	6#	7#	8#	9#	10#	11#
												Base plate thickness d1(mm)	250	262	274	286	298	310	322	334	346	358.0	370.0
Limit value Δ (mm)	2.38	2.42	2.45	2.49	2.52	2.56	2.59	2.63	2.67	2.70	2.74

Vertical prestressed reinforcement on 1#～11# base plate thickening crossbeam of this section of base plate is carried out stretch-draw by limit value Δ listed in table respectively；Other base plate of base plate is thickeied the vertical prestressed reinforcement on crossbeam and presses same method calculating Δ value, and carry out stretch-draw by Δ value。

Step 3, stretch-draw baseboard prestress reinforcing bar

After the whole stretch-draw of all vertical prestressed reinforcement, stretch-draw baseboard prestress reinforcing bar, complete the construction of wide box girder bridge girder base arrangement。

In construction, base plate bursts apart when stretch-draw baseboard prestress reinforcing bar phenomenon；After bridge puts into effect, testing through one-year age, base plate also bursts apart, it was demonstrated that the present invention is respond well。

Claims (3)

1. the wide box girder bridge girder base arrangement that can prevent Bottom slab breaking, it is characterized in that: be equipped with base plate (2) top of baseboard prestress reinforcing bar (3) section along along bridge to there being spaced base plate to thicken crossbeam (6), having in the bottom surface of base plate and thicken, with base plate, the steel plate (8) that crossbeam is corresponding up and down, the bottom surface of end face and steel plate that base plate thickeies crossbeam is the level of state；The duct (7) having correspondence spaced apart, upper and lower in crossbeam and base plate is thickeied at base plate, being installed with the vertical prestressed reinforcement (5) being made up of finish rolling deformed bar in duct, vertical prestressed reinforcement stretches out the upper end of base plate thickening crossbeam to be fixed by nut (9) respectively with the lower end stretching out steel plate。

2. the wide box girder bridge girder base arrangement preventing Bottom slab breaking according to claim 1, it is characterised in that: described base plate thicken crossbeam (6) along along bridge to mutual spacing s_vSpan be: 150cm≤s_v≤ 300cm；Base plate thickeies the centre-height d of crossbeam₂Span be: (K/15-d_j)≤d₂≤(K/10-d_j), in formula, K is baseplate width, d_jFor base plate average thickness。

3. the construction method of the wide box girder bridge girder base arrangement of Bottom slab breaking described in claim 1, can be prevented, it is characterised in that: comprise the following steps:

Step 1, build girder

After design erection template and assembling reinforcement, build girder and the concrete of base plate thickening crossbeam, simultaneously at the bottom surface pre-embedded steel slab of base plate, thicken the duct of reserved correspondence up and down in crossbeam and base plate, the reserved boring corresponding with this duct in steel plate at base plate；

Step 2, installation and stretch-draw vertical prestressed reinforcement

When the concrete strength of step 1 reaches 90% design strength, vertical prestressed reinforcement is thickeied through base plate by root the boring of duct reserved in crossbeam and base plate and steel plate, utilizes the nut of vertical prestressed reinforcement upper end that the upper end of vertical prestressed reinforcement is fixed on base plate and thicken the top of crossbeam；The nut of vertical prestressed reinforcement lower end is screwed with finger, itself and surface of steel plate is made to be adjacent to, with finger normal forces can not continue to screw vertical prestressed reinforcement time its lower end stretch out the length of nut for benchmark, continue the mode screwing the nut of vertical prestressed reinforcement lower end with screwing tool and vertical prestressed reinforcement is carried out stretch-draw, measure vertical prestressed reinforcement lower end simultaneously and stretch out the value added of nut length, this value added is defined as vertical prestressed reinforcement stretching extension value, stretch-draw vertical prestressed reinforcement is stopped when vertical prestressed reinforcement stretching extension value reaches limit value Δ；

Limit value Δ is tried to achieve by following formula:

$\mathrm{\Δ}=\frac{{\mathrm{\σ}}_{con}{A}_p{s}_v}{{\mathrm{nrE}}_s{A}_{pv}}(d_1+d_2)$

In formula

σ_con: the design tension stress of baseboard prestress reinforcing bar,

A_P: the total cross-sectional area of baseboard prestress reinforcing bar,

s_v: base plate thicken crossbeam along along bridge to mutual spacing,

N: thicken the vertical prestressed reinforcement limb number on crossbeam at same base plate,

R: the circular curve radius of base plate, when for other curve form, according toCalculating is taken, and wherein l is curve chord length, and β is the ratio of curve rise f and chord length l,

E_s: the elastic modelling quantity of vertical prestressed reinforcement,

A_pv: the area of section of single limb vertical prestressed reinforcement,

d₁: base plate thickness,

d₂: base plate thickeies the centre-height of crossbeam；

Step 3, stretch-draw baseboard prestress reinforcing bar

After the whole stretch-draw of all vertical prestressed reinforcement, stretch-draw baseboard prestress reinforcing bar, complete the construction of wide box girder bridge girder base arrangement。