JPH0348285B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite deck bridge made of section steel and concrete.

Conventionally, for example, synthetic deck bridges such as road bridges,
For example, as shown in FIG. 1, T-beams 1 having protrusions 1b on the upper surface of the upper flange 1a are arranged in parallel at required regular intervals, and a bottom steel plate 2 is placed between the lower end surfaces of each T-beam 1 with protrusions. Welded, an upper force distribution reinforcing bar 3 is disposed at a position slightly above the upper flange 1a of each T-shaped steel 1 with projections, perpendicular to each T-shaped steel 1 with projections. Concrete 4 is placed inside the so-called open section steel box girder up to a position slightly above the distribution reinforcing bars 3.
It is constructed by pouring.

Composite slab bridges made in this way can keep the slab height ratio (ratio of slab height to span) as low as 1/30 or less, so they are used for bridges with span lengths of 26 m or less.

However, in this conventional composite deck bridge, the open cross-section steel box girder is completely filled with concrete, so as the span becomes longer, the deck height increases, and as a result, the As shown in Figure 2, the weight of the steel girder supporting the concrete weight also increases.

When the span length exceeds 20 m, the weight per unit area of the steel girder increases rapidly, which significantly impairs economic efficiency.In addition, bridges with span lengths of 26 m or more cannot be constructed using composite slab bridges that are fully filled with concrete. It would be economically and mechanically difficult to construct such a system.

The present invention has been made to solve the problems of conventional synthetic deck bridges, and examples thereof will be described below.

What is shown in FIGS. 3 to 5 is the first embodiment of the present invention.
In this embodiment, T-shaped steels 1 having projections 1b on the upper surface of the upper flange 1a are arranged in parallel at required regular intervals, and a bottom steel plate 2 is welded between the lower end surfaces of each of the T-shaped steels 1 with projections. , an upper force distribution reinforcing bar 3 is disposed at a position slightly above the upper flange 1a of each T-shaped steel 1 with projections and perpendicular to each T-shaped steel 1 with projections.

Holes 1d are bored in the web portion 1c of each T-shaped steel 1 with projections at predetermined intervals in the longitudinal direction at approximately 1/2 the height of the web portion 1c of each T-shaped steel 1 with projections. A lower distribution reinforcing bar 5 is provided through the holes 1d of 1c, and a very light foamed resin plate with a specific gravity of 0.06 or less is installed from the upper surface of the bottom steel plate 2 to a position slightly below the lower distribution reinforcing bar 5. 6 and pour expanded concrete 7 from the upper surface of the foamed resin board 6 to a position slightly above the upper load distribution reinforcing bars 3 to construct a composite deck bridge.

What is shown in FIG. 6 is a second embodiment of the present invention, in which a support metal fitting 8 is provided between the web portions 1c of the T-beams 1 with projections located slightly below the lower distribution reinforcing bars 5. , a corrugated steel plate 9 as a half-filling formwork is arranged, and the upper distribution reinforcing bar 3 is inserted from the upper surface of this corrugated steel plate 9.
Expanded concrete 7 is poured to a position slightly above the bottom steel plate 2, and a space 10 is formed between the upper surface of the bottom steel plate 2 and the lower surface of the corrugated steel plate 9, thereby constructing a composite deck bridge.

The diameter of the lower reinforcing bars 5 must be 13 mm or more, and the distance between the lower reinforcing bars 5 is at most 300 mm.

The concrete to be poured may be ordinary concrete with a compressive strength of 270 kg/cm ² or more at 28 days old, but in order to prevent cracks from occurring due to drying shrinkage of concrete, expansion is added to the above ordinary concrete mix. 30Kg of cement admixture
Preference is given to using expanded concrete with the addition of m ³ .

Furthermore, by using artificial lightweight aggregate with a unit volume weight of 2 tons/m ³ or less as the sand and gravel as the aggregate, it is possible to further reduce the weight of the concrete.

As described above, the present invention arranges T-beams having protrusions on the upper surface of the upper flange in parallel at required equal intervals,
A bottom steel plate is welded between the lower end surfaces of the web parts of each T-shaped steel with projections, and a bottom steel plate is welded to a position slightly above the upper surface of the upper flange of the T-shaped steel with modified projections, and is perpendicular to each T-shaped steel with projections. An upper force distribution reinforcing bar is installed, and a lower force distribution reinforcing bar is installed perpendicularly through approximately 1/2 the height of the web portion of each T-beam with a projection. Since a composite slab bridge was constructed by pouring concrete from the lower position to a position slightly above the upper distribution reinforcing bars, the bottom steel plate was integrated by welding between the lower end surfaces of the web parts of each T-shaped steel with protrusions. The structure is
Since the bottom steel plate is continuous, it looks like I-beams are lined up in series, and has resistance to large external forces.

In addition, with respect to a positive bending moment in the lateral direction (lower edge side tensile stress), the bottom steel plate takes charge of the tensile force below the neutral axis, and the concrete takes charge of the compressive force above the neutral axis.

In other words, even if concrete is filled below the neutral axis, it does not contribute to the strength of the slab bridge.

For this reason, according to the synthetic deck bridge of the present invention, like the conventional synthetic deck bridge shown in FIG.
Without completely filling the so-called open section steel box girder from the top surface of the bottom steel plate to a position slightly above the upper load distribution reinforcing bar, the lower distribution force is passed orthogonally to approximately 1/2 of the height of the web section. Since reinforcing bars are placed and concrete is placed only above and slightly below the lower reinforcing bars, the weight of concrete and steel girder per unit area can be reduced, and the weight of the steel girder can be reduced. The applicable span range can be extended to 40m.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional composite deck bridge, Fig. 2 is a graph showing the relationship between the steel girder weight per unit area and span length, and Fig. 3 is a composite showing the first embodiment of the present invention. A cross-sectional view of the deck bridge; FIG. 4 is a cross-sectional view taken along the line A-A in FIG. 3; FIG. 5 is a cross-sectional view taken along the line B-B in FIG. 3; FIG. It is a cross-sectional view of a synthetic deck bridge showing an example.

Claims (1)

[Claims] 1 T-beams having protrusions on the upper surface of the upper flange are arranged in parallel at the required equal intervals, and a bottom steel plate is welded between the lower end surfaces of the web portions of the T-beams with protrusions,
An upper force distribution reinforcing bar is arranged at a position slightly above the upper surface of the upper flange of each T-shaped steel with projections, perpendicular to each T-shaped steel with projections, and the height of the web portion of each T-shaped steel with projections is A composite floor slab is made by placing lower distribution reinforcing bars perpendicularly through approximately 1/2 of the area, and pouring concrete from a position slightly below the lower distribution reinforcement bars to a position slightly above the upper distribution reinforcement bars. bridge.