Static structures (e.g. – buildings) – Sheetlike element assembled parallel to existing wall,... – Assembled with fastening device
Reexamination Certificate
1999-04-06
2001-04-24
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Sheetlike element assembled parallel to existing wall,...
Assembled with fastening device
C052S746100, C052S741100, C052S425000, C052SDIG007
Reexamination Certificate
active
06219986
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for reinforcing an existing wall structure, and preferably for reinforcing a ferroconcrete wall type pier or the like.
2. Description of the Prior Art
Known methods for reinforcing existing ferroconcrete piers include steel lining methods and concrete lining methods. Further, a method using steel segments has been disclosed by the present applicant in Japanese Laid Open Patent Publication No. JP-9,209,580.
The method using steel segments will be described with reference to
FIGS. 8
a
and
8
b
. This method employs: a plurality of PC steel bars
3
inserted into a plurality of holes which are pierced through an existing wall type pier
2
, in the direction of its thickness, installed on a bridge pedestal
1
; and a plurality of steel segments
4
, each of which are formed into a column having a cross-section in the shape of a circular-arc, and which are integrally provided with connecting flanges
4
a
at both sides of each circular-arc column in the width direction. Several stages of steel segments
4
, which are arranged adjacent to each other sideways, are vertically arranged onto the wall surface of the pier
2
by superimposing the respective flanges
4
a
. The PC steel bars
3
are allowed to pass through a plurality of holes formed in the flanges
4
a
and the holes of the pier
2
. The end portions of the PC steel bars
3
are then screwed, and the steel segments
4
are fixed onto the wall surface. Then, concrete
5
is placed into the circular-arc-like space between the steel segments
4
and the wall surface, and the steel segments
4
are integrated to the wall surface of the pier
2
. The PC steel bars
3
are then tensioned to impart restricting force to the concrete.
Since a plurality of steel segments is divided in the vertical and horizontal direction, this method is applicable to a pier having any cross-section.
Compared with the steel lining method and the concrete lining method, the segment method is simple in structure, realizes a larger concrete restricting effect, and increases earthquake-resistance ability. The segment method also eliminates the necessity of providing a form required for the concrete lining method, thereby achieving labor-saving of construction and shortening of construction period.
FIG. 8
a
shows an example in which two pieces of the PC steel bars are provided for each steel segment;
FIG. 8
b
shows an example in which three pieces of the PC steel bars are provided for each steel segment.
The above-described segment method, however, has the following technical problems.
The restricting force applied in the axial direction of the pier, that is, to the wall surface, becomes large by provision of the steel segments and the PC steel bars, and a sufficient earthquake-resistance ability of the wall surface is obtained. However, since the side surfaces (end surfaces) of the pier, which are located in the direction perpendicular to the axial direction, are not treated, when a large vibration is applied to the side surfaces of the pier, the covering concrete on the side surfaces is extruded by buckling of the main reinforcement, and damages progress therefrom. Therefore, not only is the earthquake-resistance ability decreased, but also the appearance is harmed.
Further, since the steel segments are divided into a plurality in the horizontal direction, there is a limitation in introducing the restricting force. This also complicates both the operation to superimpose the flanges onto each other, and the crane operation for carrying the divided steel segments upon actual assembly thereof.
OBJECT OF THE INVENTION
The present invention solves the above problems related to the reinforcement method using steel segments. The object of the present invention is to provide a method for reinforcing an existing wall structure which is capable of preventing buckling of end surfaces, and improving earthquake-resistance ability of the wall structure by imparting restricting forces, even to the end surfaces of the wall.
SUMMARY OF THE INVENTION
To achieve the above object according to the present invention, there is provided a method for reinforcing an existing wall structure which includes the steps of:
attaching steel segments in a plurality of stages onto the wall surface of the existing wall structure, each of the steel segments being formed into a cylinder-like form that has a continuous cross-section in the shape of a circular-arc, and having flanges for connection which are integrally provided on both sides of each circular-arc body in the width direction;
allowing a plurality of PC steel bars to pass through a plurality of holes formed in the flanges and a plurality of holes pierced through the existing wall structure in the direction of its thickness;
screwing the end portions of the PC steel bars having been passed through the flanges and the existing wall structure to fix said steel segments onto the wall surface; and
placing concrete into the circular-arc protruded spaces between the steel segments and the wall surface to integrate the steel segments onto the wall surface of the existing wall structure.
The above method is characterized by further including the steps of:
providing reinforcing bodies on end surfaces of the existing wall structure in the direction perpendicular to the wall surface thereof; and
connecting the reinforcing bodies to the end portions of the steel segments.
Therefore, it becomes possible to apply restricting forces even to the end surfaces of the existing wall structure in the direction perpendicular to the thickness direction thereof, and hence, possible to improve earthquake-resistance ability of the wall structure.
The reinforcing bodies may be newly constructed concrete blocks, and may have a structure, wherein the flanges provided on both end portions of the steel segments are positioned on a portion of the concrete blocks being at the same surface level as that of the wall surface, and PC steel bars are allowed to pass through the flanges and the concrete blocks and be fastened to fix the concrete. On the other hand, the reinforcing bodies may be flat steel plates which may be integrated with the end portions of the steel segments by welding. Further, the reinforcing bodies may be curved steel plates which are integrated with the end portion of the steel segments by welding in such a manner as to surround the end surfaces of the existing wall structure, and the structure thereof may be such that concrete is placed into the protruded portions formed between the curved steel plates and the end surfaces of the existing wall structure.
In the method of the present invention, an active restricting effect can be obtained by tensioning the PC steel bars after placing and curing the concrete.
The steel segments may be a unit which includes a plurality of circular-arc columns arranged sideways, and flanges connecting the respective adjacent columns to each other and integrating the same. Being so, it becomes possible to simplify the arrangement operations of the steel segments, and to alleviate limitations upon introducing restricting force by the PC steel bars.
REFERENCES:
patent: 5469674 (1995-11-01), Morello
Chavez Patrick J.
Dougherty & Clements LLP
Friedman Carl D.
Obayashi Corporation
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