GB2302888A

GB2302888A - Precast floor slab

Info

Publication number: GB2302888A
Application number: GB9613965A
Authority: GB
Inventors: Shigeji Onsen; Akihito Mori; Toshitaka Hikimura
Original assignee: Sho Bond Corp
Current assignee: Sho Bond Corp
Priority date: 1995-07-04
Filing date: 1996-07-03
Publication date: 1997-02-05
Anticipated expiration: 2016-07-03
Also published as: JPH0921114A; AU5836896A; KR0183425B1; KR970011189A; SG42419A1; MY112057A; GB9613965D0; JP2832522B2; GB2302888B

Abstract

A precast floor slab (1) comprises a steel plate (2) joined to a concrete layer (10) by friction-jointed high-strength bolts (3) used as shear connectors. Adjacent floor slabs (1) may be joined by a splice plate (4) attached to edge portions (2b) of the steel plates (2) of the floor slabs by high-strength bolts (3) which act as shear connectors and project into a concrete infill strip [not shown] between the concrete layers (10) of the floor slabs.

Description

PRECAST FLOOR SLAB The present invention relates to a precast floor slab composed of a steel plate and concrete. For example, this invention yes to a precast floor slab composed ( eel plate and concrete in which high-strength bolts friction-jointed to the steel plate are used as shear connector structure and joint portions of precast floor slabs are friction-jointed to each other by means of the high-strength bolts together with an auxiliary plate, the high-strength bolts also being used as shear connectors.

Bridge floor slabs include a cast-in-place slab for which form assembling, reinforcing and concrete placing processes are conducted in the field, and a precast floor slab in which such processes as described above are carried out in advance in the shop and then brought to the field.

Conventionally, as shown in Fig.7, a precast floor slab composed of a steel plate and concrete is prepared by welding shear connectors 13 of stud type, pipe type and the like at predetermined intervals on a concrete placing portion 12a of a steel plate 12 of predetermined size comprising the concrete placing portion and a joint portion, and then placing concrete on the concrete placing portion 12a. Two panels are connected by opposingly facing the joint portions 12b, welding an attaching plate 14 on an undersurface of the joint portions 12b and then placing concrete thereon so as to keep continuity of the steel plate 12.

In Fig. 7, there is shown a situation where concrete is not placed on the joint portions, numerals 17 and 18 designating reinforcing bars.

Operation of welding considerably depends on welder's skill and is easily influenced by operating environment including wind and ambient temperature around the site in the case of field welding.

Such disadvantages make deck welding less reliable. Further, distortion (internal stress) and change in hardness derived from welding would decrease the resistance to fatigue of decks.

On the other hand, structural continuity of jointed decks is weakened because of difference between structure of main body and that of joint portions.

Accordingly, it is an object of the present invention to solve these conventional problems by using a deck and joint structure in which fixture of shear connectors to a steel plate and connection of steel plates are conducted without welding.

To achieve the above mentioned object, there is provided a precast floor slab composed of a steel plate and concrete, in which high-strength bolt holes are formed on the steel plate at predetermined intervals, high-strength bolts are inserted in the high-strength bolt holes and fitted with nuts to form shear connectors, and then concrete is placed thereon.

There is also provided joint structure of a precast floor slab composed of a steel plate and concrete, in which joint portions of precast floor slabs to be connected are opposingly faced each pother, a splice plate, which has high-strength bolt holes corresponding to those high-strength bolt holes formed on the jointing portions, is attached on an undersurface of the joint portions, high-strength bolts are inserted in the high-strength bolt holes and fitted with nuts to form shear connectors, precast floor slabs to be jointed are connected each other, and then concrete is placed thereon.

As the high-strength bolts are friction-jointed, each bolt functions as reliable shear connector structure of the floor slab composed of a steel plate and concrete without decreasing the resistance to fatigue which has been inevitable to conventionally welded shear connectors because of distortion and change in hardness thereof.

As the joint portions of precast floor slabs to be connected are opposingly faced each other in the joint structure, attached by the splice plate on the undersurface thereof and friction-jointed by means of the high-strength bolts similarly as the concrete placing portion, structure of the concrete placing portion and the joint structure are about the same, thereby improving continuity of both structure as a whole and, because of the same shear connector structure, improving reliability.

Preferably, because the high-strength bolts are friction-jointed by driving nuts from both surfaces of the steel plate, fixing of shear connectors is not affected conventionally by a welder's skill and can be conducted conveniently without a decrease in the resistance to fatigue caused by distortion (internal stress) and change in hardness due to a welding operation.

Preferably, because of such structure that the jointing portions of the precast floor slabs to be connected by means of the joint structure are opposingly faced each other, attached with the auxiliary plate thereunder and friction-jointed by the high-strength bolts similarly as in the case of the concrete placing portion, it is possible to avoid conventional problems arising from field welding conditions such as wind, ambient temperature, etc. as well as other inconvenience accompanied by welding, thereby rendering structure of the concrete placing portion and the joint portions substantially identical and improving continuity thereof as a whole.

Accordingly, a reliable shear connected-structured precast floor slab composed of a steel plate and concrete and joint structure thereof can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a section taken on line A-A in Fig. 2, showing a precast floor slab composed of a steel plate and concrete.

Fig.2 is a plan view of the precast floor slab composed of a steel plate and concrete.

Fig. 3 is a section taken on line B-B in Fig. 4, showing joint structure of a precast floor slab to be connected.

Fig. 4 is a plan view of joint structure of a precast floor slab to be connected.

Fig. 5 is a section showing how to fix a high-strength bolt.

Fig. 6 is a section of an another embodiment how to fix a high-strength bolt.

Fig. 7 is a section of a conventional precast floor slab composed of steel and concrete and joint structure thereof.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The present invention will be described in detail by referring the drawings.

In Fig. 1, only outlines of placed concrete are drawn and inside thereof is shown as if concrete is not placed for convenience. An embodiment of a precast floor slab 1 is shown in Figs. 1 and 2. A steel plate 2 is consisted of a concrete placing portion 2a and a jointing portion 2b and may have arbitrary size decided by considering conditions of a bridge where floor slabs thereon are replaced and effective conveyance of the panel.

Bolt holes 9 for high-strength bolts 3 are formed on the steel plate at predetermined intervals. In Fig. 2, the highstrength bolt holes 9 formed on the concrete placing portion 2a are invisible because the high-strength bolts 3 are inserted therein.

Distances of the high-strength bolt holes 9 are different between the concrete placing portion 2a and the joint portion 2b in Fig. 2.

The high-strength bolt 3 is fitted with a washer 6a and a nut 5a at a downward portion thereof and inserted from upside of the concrete placing portion 2a in the high-strength bolt hole 9 formed thereon as shown in Fig. 5. The high-strength bolt 3 is then fitted with a washer 6b and a nut 5b from downside and fixed to the concrete placing portion 2a by driving these nuts 5a and 5b from both sides so that the the bolt 3 functions as a shear connector.

Fixing of the high-strength bolt 3 is not limited to the above mentioned manner but may be conducted, for example, by inserting the bolt 3 from downside of the concrete placing portion 2a to the bolt hole 9 and driving a nut Sc from upside, as shown in Fig. 6 in which numeral symbols 6c and 6d designate washers. In either case, predetermined axial force is added to the high-strength bolt 3 to stock the frictional resistance required. Height of the highstrength bolt 3 is preferably within a range from a neutral axis level to an upper covering thickness of concrete to be placed.

Reinforcing bars 7 and 8 are then arranged above the steel plate 2 while side forms are assembled, followed by placing concrete 10 thereon. The forms are assembled to leave the jointing portions 2b at both sides of the steel plates 2 to the axial direction of a bridge for connecting neighboring precast floor slabs 1, a single jointing portion being left at one side of the steel plate in case of an outmost panel. The forms are removed after the concrete is placed.

In this manner, there is prepared the precast floor slab 1 composed of a steel plate and concrete.

Joint structure for connecting precast floor slabs each other is shown in Figs. 3 and 4.

In order to provide the joint structure, first of all, the steel plate jointing portions 2b of the above mentioned precast floor slabs 1 are opposingly faced each other, while reinforcing bars 8 directed to the bridge axis are overlapped (the bars 8 are conventionally arranged in advance to overlap each other).

After a splice plate 4, which has high-strength bolt holes 9 corresponding to those high-strength bolts formed on the jointing portions 2b, is attached on the undersurface of the portions 2b, the headed high-strength bolts 3 fitted with a washer 6a and a nut 5a at downward portion are inserted in holes 9 from upper side thereof, the high-strength bolt holes 9 being invisible because of the inserted bolts 3 in Figs. 3 and 4. A washer 6b and a nut 5b are then fitted to the high-strength bolts 9 from underside of the auxiliary plate 4 and driven to fasten thereof from both sides together with the nut 5a. The high-strength bolts 3 are thus fixed as a shear connector to the jointing portions 2a, thereby both portions 2a of the precast floor slabs 1 to be connected being friction-jointed each other. As a matter of course, the highstrength bolts 3 may be fixed in any other manner, for example, by way of fixing described in Fig. 4. Preferably, height of the highstrength bolts 3 is within a range from the neutral axis level to the upper covering thickness.

After reinforcing bars 7 are arranged, concrete is placed on the jointing portions 2b to complete the joint structure. Fig. 3 shows a situation where concrete is not placed.

Claims

CLANS

1. A precast floor slab comprising: a steel plate having bolt holes at predetermined intervals; high-strength bolts inserted in the bolt holes and fitted with nuts to form shear connectors; and a concrete layer into which the bolts project.

2. A floor slab assembly comprising first and second floor slabs as claimed in claim 1, wherein: edge portions of the steel plates of the floor slabs are side by side; and a splice plate which has bolt holes is attached to the undersurfaces of the edge portions of the steel plates by high-strength bolts which are inserted through bolt holes in the splice plate and the edge portions, are fitted with nuts to form shear connectors, and project into a concrete infill strip between the concrete layers of the floor slabs.

3. A precast floor slab substantially as herein described with reference to, or with reference to and as illustrated in, Figs. 1 and 2 of the accompanying drawings.

4. A floor slab assembly substantially as herein described with reference to, or with reference to and as illustrated in, Figs. 3 and 4 of the accompanying drawings.