JPH047403B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a steel composite girder that combines a steel girder and concrete slab, and a method for constructing the same.
This prevents stress from remaining in the steel girder due to pre-stretching, which introduces compressive stress sufficient to cancel out the tensile stress generated in the concrete cross section.

(Prior art) Generally, for bridges or expressways,
Regarding the cross-section of the concrete deck in a steel composite girder that combines a steel girder and a concrete deck via anti-slip devices, only compressive stress occurs in all parts under any design load, and no compressive stress occurs. It is desired that the strong slab concrete acts effectively over the entire cross section. Therefore, if it is found that tensile stress is generated in the cross section of the concrete slab for any reason, it is necessary to introduce the necessary compressive stress in advance to cancel out the tensile stress, that is, so-called pre-stressing. Lessing is generally applied to concrete floor slabs. That is, as shown in FIGS. 2a and 2b, after welding a large number of stoppers 3 at appropriate intervals to the upper surface of the upper flange 4 of the steel girder 2, which has been completely erected, the steel girder 1 is
Along the longitudinal direction, a large number of sheaths 5 containing steel materials such as piano wire are arranged at appropriate intervals, and after assembling the required reinforcing structure, concrete is poured to form the concrete floor slab 1. In order to apply pre-stressing to the concrete floor slab 1 having such a configuration, for example, against tensile stress occurring in the longitudinal direction, both ends of a piano wire or the like in the sheath 4 are pulled and fixed to the end faces 7 of the concrete floor slab 1, respectively. Applying a compressive stress comparable to the predicted tensile stress to the slab concrete 1 in advance is as follows:
This was a conventional pre-stressing implementation mode.

(Problems to be Solved by the Invention) However, when performing conventional pre-stressing in this manner, the concrete of the deck slab 1 is integrated with the slip stopper 3 welded to the upper flange 4 of the steel girder 2. , has already hardened, so the compressive stress applied in advance, that is, the prestress, will be applied to the composite cross section of the concrete deck 1 and the steel girder 2. Therefore, a portion of the applied force required for the conventional pre-stressing according to the embodiment described above, for example, 25
% is consumed in deforming the steel girder 2, which not only results in the undesirable result that "stress due to pre-stressing" inevitably remains in the steel girder 2, but also causes excessive force to be applied. Therefore, it is necessary to provide an extra sheath and perform extra processing operations, which is extremely uneconomical.

An object of the present invention is to solve the above-mentioned conventional problems, and when performing pre-stressing, conventionally, a shear stopper was welded directly onto the upper flange of a steel girder, and slab concrete was then formed on the flange. In contrast, by welding a shear stop onto another flange fastened to the upper flange of the steel girder with high-strength bolts and forming deck concrete on top of it, the steel girder and deck concrete can be easily connected. A steel composite girder that eliminates the bond between the steel girders and applies prestress only to the concrete cross section that originally requires prestress, leaving unnecessary stress on the steel girder and requiring only the minimum amount of force necessary. and its construction method.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the steel composite girder of the present invention is constructed by assembling a sheath containing a steel material and reinforcing bars on a flange to which anti-slip is welded, and pouring concrete. The flange of the prestressed concrete slab formed by applying tensile force to the steel material is placed on the upper flange of the steel girder via an oil layer, and the flange is fastened to the upper flange with high-strength bolts. This is a characteristic feature.

In addition, in the method of constructing a steel composite girder according to the present invention, a flange to which a slip stopper is welded is placed on the completed steel girder upper flange through an oil layer, and is temporarily attached to the upper flange using high-strength bolts. a step of assembling a sheath with a built-in steel material and reinforcing bars on the flange and pouring concrete to complete the concrete floor slab; and a step of attaching both ends of the steel material built into the sheath to the end face of the concrete floor slab. and a step of injecting mortar into the sheath after fully tightening the high-strength bolts.

(Function) In the steel composite girder of the present invention having the above-mentioned features and its construction method, the minimum necessary tensile force is applied to the cross section of the concrete slab, and the steel girder is properly constructed without residual unnecessary stress. can be pre-stressed.

(Example) The present invention will be described in detail below with reference to the drawings.

Figure 1 shows an example of the detailed structure of the main parts of the steel composite girder of the present invention when a steel girder with a relatively long span is used like the conventional steel composite girder shown in Figure 2, and the cross section of each part is shown in Figure 1. They are shown in a to c, respectively.

In the illustrated configuration example, first, changes in the plate thickness of the upper flange 14 in the steel girder 2 that has been completely erected are smoothed out to make the upper surface of the upper flange 14 flat and smooth, and the field joints of the upper flange 14 are Weld on-site and finish the upper layer smoothly. Furthermore, a tab plate 13 made of a steel plate is welded to the longitudinal edge of the upper flange 14 as shown in the figure. Steel girder 2 subjected to such processing
After applying an oil or fat as a lubricant to the smooth surface of the upper flange 14, the second flange 11 made of a mild steel plate with a thickness of 10 mm or more is aligned with the longitudinal edges of the upper flange 14. Lay them out one on top of the other. The second flange 11 made of this mild steel plate
As will be described later, it acts integrally as a part of the composite cross section of the concrete floor slab 1 formed by pouring concrete. Also, this second flange 1
1, in order to connect the above-mentioned concrete slab 1 to the steel girder 2, high-strength bolts of, for example, Torcia type are attached to the tab plate 13 welded to the upper flange 14 via a filler 9 made of mild steel, as shown in the figure. 6
Fasten and secure. In this case, the bolt holes provided in the second flange 11 and the tab plate 13 are formed in the shape of slots in the longitudinal direction of the steel girder 2, so that the position where the second flange 11 is fixed to the upper flange 14 is relatively shifted. Make sure you get it. In addition, since the head of the high-strength bolt 6 used for fastening is buried in concrete later,
It is preferable that the bolt be of the Torcia type, which has a rivet-like bolt head, can be fixed to a nut at the tip of the screw, and can be sheared when a tightening torque exceeds a predetermined value.

On the upper surface of the second flange 11 configured as described above, concrete shear stops 3 are welded, for example, as shown in the drawings, with appropriate distribution. Note that the anti-slip 3 may be of any type or type. On the second flange 11, a sheath 5 containing reinforcing bars for concrete pouring and a steel material for pre-stressing similar to that described above in FIG. 2 is appropriately disposed and assembled, and then concrete is poured. The required concrete floor slab 1 is formed by pouring. The steel material 5 contained in the sheath 5 is appropriately selected from, for example, a so-called piano wire, a steel wire, a twisted steel wire, a steel rod, or the like.

The steel composite girder of the present invention constructed as described above is preferably erected in sequence by the construction method described below.

(1) After completing the erection of the steel girder 2, the upper surface 4 of the upper flange 14 is coated with oil such as grease as a lubricant.

(2) On the upper surface 4 of the upper flange 14 of the steel girder 2, the second flange 11 welded with the anti-slip 3 appropriately distributed is placed overlappingly, and the edge of the second flange 11 and the upper flange 14 are Welded tag plate 13 via filler 9,
Temporarily tighten with high-strength bolts 6 to temporarily fix.

(3) Floor slab concrete 1 on the second flange 11
After appropriately assembling the reinforcing bars for use in the concrete and the sheath 5 containing steel materials such as piano wire for pre-stretching, concrete is poured and cured to complete the concrete floor slab 1.

(4) Completely loosen all the high-strength bolts 6 located other than the midpoint of the span of the steel girder 2, and tighten the upper flange 1 of the steel girder 2.
4, the second flange 11 is made to be able to slide in accordance with the prestress when prestress is applied except at the midpoint of the span.

(5) Apply force to both ends of a steel material such as piano wire for concrete pre-stretching (PC) in each sheath 5 until a predetermined tensile force is reached, and use bolts and nuts connected to both ends of the steel material. Its both ends are fixed to the end face of the concrete floor slab 1.

(6) If necessary, use a vibrator 8 to vibrate the concrete slab 1 while repeatedly moving it from the end of the girder toward the midpoint of the span, to loosen the upper flange 14 of the steel girder 2 during pre-stressing. The friction generated between the upper surface 4 and the second flange 11 is reduced, and the second flange 1 is
1 so that it can slide relatively easily.

(7) Every time the tensile force of the prestressing steel material decreases due to the effect of the vibration described above and loosens, apply force again to maintain the predetermined tensile force.

(8) When the prestressing introduced into the prestressing steel reaches the predetermined value required to cancel the expected tensile force and becomes stable, the necessary prestressing has been completed, and all high-strength bolts should be After tightening and fully securing all sheaths 5
Inject mortar into the floor slab concrete 1
Harden the whole thing without any gaps.

(Effects of the Invention) As is clear from the above description, the steel composite girder of the present invention connects the flange of the prestressed deck concrete after applying tensile force and the upper flange of the steel girder with high-strength bolts. Because they are fastened, a portion of the pre-stretching force applied to cancel the tensile stress generated in the concrete slab is not applied to the upper flange of the steel girder, unlike in the conventional case.

Therefore, with the method of constructing a steel composite girder of the present invention, pre-stressing of concrete slabs can be carried out economically by applying the minimum necessary force.

[Brief explanation of drawings]

Figures 1a, b, and c are cross-sectional views showing examples of the main parts of the steel composite girder of the present invention, respectively, and Figures 2a and b are side views showing examples of the schematic configuration of a conventional steel composite girder, respectively. and sectional views of various parts. 1... Slab concrete, 2... Steel girder, 3... Slip prevention, 4... Flange top surface, 5... Sheath, 6... High strength bolt, 7... Concrete end face, 8... Vibrator, 9...
Filler, 11...Second flange, 13...Tab plate, 14...Upper flange.

Claims (1)

[Scope of Claims] 1. A sheath with a built-in steel material and reinforcing bars are assembled on the flange to which the anti-slip is welded, and concrete is poured, and a tensile force is applied to the steel material to form the flange of prestressed slab concrete. A steel composite girder, characterized in that it is disposed on an upper flange of a steel girder via an oil layer, and the flange is fastened to the upper flange with high-strength bolts. 2. A steel composite girder according to claim 1, wherein the high strength bolt is a Torsia type high strength bolt. 3 A process of installing a flange with a slip stopper welded to it through an oil layer on the upper flange of the steel girder that has been completed and temporarily fastening it to the upper flange with high-strength bolts, and incorporating steel material on the flange. a step of assembling the sheath and reinforcing bars and pouring concrete to complete the concrete floor slab; a step of fixing both ends of the steel built in the sheath to an end face of the concrete floor slab; 1. A method for constructing a steel composite girder, comprising sequentially performing a step of injecting mortar into the sheath after tightening the sheath. 4. In the construction method as set forth in claim 3, when fixing both ends of the steel material built into the sheath to the end face of the concrete deck after pre-stretching, a fixed point other than a predetermined fixed point of the steel girder is fixed. Erection of a steel composite girder characterized by loosening all the high-strength bolts located in advance, and applying a predetermined tensile force to both ends of the steel material built in the sheath while applying vibration to the concrete floor slab with a vibrator. Construction method. 5. A construction method for a steel composite girder according to claim 3 or 4, characterized in that the high-strength bolt is a Torsia type high-strength bolt.