JPS5832243B2 - Continuous type bridge using prestressed steel girders - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous type bridge using prestressed steel girders commonly referred to as pre-beams.

As a bridge construction girder, a forward deflection load is applied to the steel girder in advance, concrete is poured around the lower flange that will be the tension side, and the forward deflection load is released after the concrete hardens. A prestressed steel girder, commonly called a pre-beam, which introduces prestress stress into the lower flange concrete by the restoring force of the steel girder is already known (Japanese Patent Publication No. 33-10424).

A girder in which such a prestressed steel girder is erected on site and then web concrete and slab concrete are placed to completely cover the steel girder with concrete is called a pre-beam composite girder.

This pre-beam composite girder has a high bending stiffness because the lower flange concrete and deck concrete are attached to the steel girder, and the girder height can be lower than that of a normal composite girder. This is extremely advantageous for construction of bridges that are subject to restrictions.

Furthermore, since the steel girder itself is not exposed, it has the advantage of not requiring maintenance such as painting, not generating noise, and having fire resistance.

When constructing a bridge using pre-beam composite girders that have these advantages, it is possible to consider whether to use a simple support type or a continuous support type, but in the case of a continuous support type composite girder, intermediate support It is necessary to deal with the problem of cracking of the slab concrete due to the bending moment of the roasting that acts in the vicinity.

Measures to deal with this problem include, for example, placing a temporary preload in the positive bending moment region, or jacking up the intermediate fulcrum to temporarily reduce the strength of the steel girder at the intermediate fulcrum. There is a method in which tensile stress is applied to the upper flange, and after the intermediate fulcrum concrete slab is placed and hardened, the preload is removed or jack town is carried out to support the prestress stress in the intermediate fulcrum concrete slab. be.

However, under these circumstances, countermeasures against negative moments near the fulcrum must be carried out at the construction site, and the methods are complicated, so they cannot necessarily be said to be appropriate for construction. For these reasons, although the prestressed steel girder used in the present invention has the above-mentioned advantages, it has not been constructed as a continuous support type, and has been used more often in simple support type bridges than in the past. .

The present invention aims to take advantage of the advantages of pre-beam composite girders made of prestressed steel girders, which have the above-mentioned advantages, and to apply them to a continuous composite girder type that is advantageous in terms of earthquake resistance and vehicle running stability. The purpose is to provide a continuous type bridge that can simplify the procedure for introducing prestress stress into the concrete deck slab at the intermediate support.
Span members made of ordinary prestressed steel girders with prestressed concrete on the lower flanges are constructed in the spans that receive positive bending moments, and span members made of pre-bending are constructed near intermediate supporting members that receive negative bending moments. By pouring slab concrete on the tension side and releasing the pre-bending load after the concrete hardens, an intermediate support member is erected using a deformed prestressed steel girder in which prestress stress is introduced into the slab concrete. It is characterized by the continuous construction of steel girders.

Next, the construction process of a continuous type bridge according to the present invention will be described in detail with reference to the illustrated embodiment. FIGS. Side view showing the manufacturing process of No. 1, Figures 2 a to e
1 is a side view showing the manufacturing process of an intermediate fulcrum member 2 using a deformed prestressed steel girder used for an intermediate fulcrum part that receives a negative bending moment.

As shown in FIG. 1, the span member 1 is manufactured in a manner similar to the manufacture of known prestressed steel girders.

That is, as shown in figure a, the steel girder 1. A camber is applied in advance to the steel girder 1, and then a forward deflection load (preflexion) Pf is applied to the steel girder 1□ to cancel the camber while supporting both ends of the steel girder 1□ as shown in the figure.

In this state, concrete 5 is placed on the lower flange 3 on the tension side of the steel girder 11, leaving the girder connecting end 4 as shown in Fig. Pf is released and prestress stress is introduced into the lower flange concrete 5 by the restoring force of the steel girder.

The intermediate support member 2 shown in FIG. 2 is basically manufactured in the same manner as the span member 1 described above, but in this case, the intermediate support member 2 is made of a steel girder 2 which applies the forward deflection load Pf. The position of the upper and lower flanges 6.7 is
It is arranged so as to be opposite to the prestressed steel girder 1□ for the span member.

That is, as shown in Fig. 2a (the steel girder 21 was initially attached to the lower flange 7).
is placed facing upward, and in this state, a forward deflection load Pf is applied so that the upper flange 6 becomes the tensile side as shown in Figure 2.

Next, at this stage, slab concrete 8 is poured leaving the girder connecting end 9 on the upper flange 6 on the tension side, and when this concrete 8 reaches a predetermined strength, the front deflection load Pf is released and the Prestress stress is introduced into the slab concrete 8 by the restoring force of the girder 2.

Next, as shown in FIG.
Concrete 11 was poured into concrete 8, 10,
This is a composite member in which the main steel girder is coated with No. 11.

Of course, no prestress is introduced into these web concrete 10 and lower flange concrete 11.

The intermediate fulcrum member 2 made of the deformed prestressed steel girder thus manufactured is rotated above and below the girder as shown in FIG. 2e, returned to the correct position, and stored until erection.

The span member 1 and intermediate fulcrum member 2 obtained by the above manufacturing process are constructed in the order shown in FIGS. 3a to 3d.

That is, as shown in Fig. 3a, first, the vicinity of the girder connecting ends of the span member 1 and the intermediate fulcrum member 2 were supported by temporary vents 12, etc., respectively, and the girder connecting ends 4 of the span members were exposed in advance. The girder connecting end 9 of the intermediate fulcrum member 2 is connected to the splice plate 1, respectively.
3. Connect firmly using high-strength bolts.

Next, as shown in Figure 3, the central lower surface of the intermediate support member 2 is supported by the intermediate support shoe 14, and at the same time the temporary vent 12 is removed to form a continuous girder.

Then, as shown in FIG.
Lower flange filler concrete 15 is placed on the lower flanges 3 and 7.

Finally, after the above-mentioned filler concrete 15 has hardened, Fig. 3 d
As shown in FIG. 2, the floor slab concrete 17 of the upper 7 langes 16 of the span member 1 is applied to cover not only the top of the girder connection end 4 but also the upper flange 6 of the girder connection end 9 of the intermediate fulcrum member 2. The member 20 is poured to the position where it contacts the floor slab concrete 8, and the web concrete 18 is placed on the web of the span member 1 in the same way as the floor slab concrete. Pour it until it touches J-NO.

Therefore, at this stage, a continuous girder in which all steel members 11゜21 are covered with concrete is completed, and the subsequent dead loads such as ground covering, handrails, pavement, etc., and live loads such as vehicles, etc., are handled by the lower flange prestressed concrete. This means that the concrete slab acts on the continuous composite girder combined with the steel girder.

The continuous type bridge according to the present invention has the above structure,
It has the following advantages.

As mentioned above, when constructing conventional continuous composite girder type bridges, there are problems such as cracking of concrete slabs due to negative bending moments generated near intermediate support members. As mentioned above, by applying a temporary preload to the positive bending moment region or by jerking up the opening support, tensile stress is applied to the upper flange of the steel girder at the intermediate support, and concrete is poured for the intermediate support member. hand,
The procedure involved removing the preload after curing and applying prestress stress to the concrete slab of the intermediate supporting member by jacking down the supporting point, which was extremely complicated in terms of on-site construction.

However, in the continuous type bridge according to the present invention, the basic principle of prestressed steel girders is applied to the intermediate support member 2, and the concrete slab 8 is poured on the tension side of the steel girder to which the preload is applied. By releasing the concrete floor slab 8
This method introduces prestress stress into the slab concrete 8, and the work to introduce prestress into the concrete slab 8 is carried out in advance for each member at the stage before the girder erection, that is, in the factory or on-site yard where workability is good, so it improves workability. is extremely good,
Moreover, since it is sufficient to simply connect the span member 1 and the intermediate fulcrum member 2 at the stage of constructing the girder member, there is an advantage that countermeasures against negative bending moments at the intermediate fulcrum portion are significantly simplified overall.

In addition, in the bridge of the present invention, both the span member 1 and the intermediate support member 2 have steel girders 11+21 as their constituent members, and each member 1 and 2 has prestress stress introduced into a predetermined portion in advance. It has the advantage that the continuity between the members to which these prestress stresses have been introduced can be reliably and easily achieved by connecting the steel girders as structural members.

Further, the intermediate fulcrum member 2 is constructed based on a steel girder 21 having a predetermined length, and both ends of the intermediate fulcrum member 20 are connected to the span member 1.
Therefore, this connection part can be set in a section where the bending is not large and the sign of the bending moment changes, so there is no problem with the load-bearing force, and it is possible to create an extremely rational structural type according to the bending moment distribution of the continuous girder. can do.

In addition, the handling of girders during erection is not so complicated compared to the case of a simple type bridge with conventional prestressed steel girders, and the erection work can be carried out safely. It is superior in terms of economy, earthquake resistance, vehicle drivability, aesthetics, etc., and has a better moment balance, so the girder height/span ratio can be reduced to 1/3 of that of a simple type bridge.
This has the effect that it can be reduced from 7 to 1/45, resulting in an extremely slender and beautiful bridge.

[Brief explanation of drawings]

Figures 1 a to c are side views showing the manufacturing process of the bridge span member according to the present invention, Figures 2 a to e are side views showing the manufacturing process of the intermediate fulcrum member, and Figures 3 a to d are side views showing the manufacturing process of the intermediate support member. 4 is a sectional view taken along line IV--IV in FIG. 1C, and FIG. 5 is a sectional view taken along line v-V in FIG. 2e. In the figure, 1... span member, 2...
Intermediate fulcrum member, 3, 7... Lower flange, 4, 9
......Girder connection end, 5,11...Bottom flange concrete, 6゜16...Top flange,
8, 17... Floor slab concrete, 10, 18...
... Web concrete, 12 ... Temporary vent, 13 ... Splice plate, 14 ...
...Intermediate bearing, 15... Filling concrete.

Claims (1)

[Claims] 1 In the span area that receives a positive bending moment, a span member made of a normal prestressed steel girder is erected in which prestress stress is applied to the concrete poured on the lower flange of the steel girder, and the span receives a negative bending moment. Near the intermediate supporting point, slab concrete is placed on the tension side flange due to pre-bending of the steel girder, and after the concrete hardens, pre-stress stress is applied to the slab concrete by releasing the pre-bending load. An intermediate support member made of a deformed prestressed steel girder with non-prestressed concrete is erected, and both girder members are connected to form a continuous girder. A continuous type bridge using prestressed steel girders, characterized in that all of the steel girders are covered with concrete after pouring.