WO2004072386A1

WO2004072386A1 - Prestressed scaffolding system

Info

Publication number: WO2004072386A1
Application number: PCT/KR2004/000294
Authority: WO
Inventors: Man-Yop Han
Original assignee: Man-Yop Han
Priority date: 2003-02-14
Filing date: 2004-02-13
Publication date: 2004-08-26
Also published as: EP1595031A4; JP2006517628A; CN1751157A; KR20030019937A; CN100489198C; KR100571102B1; US20060070803A1; EP1595031A1; JP4094043B2

Abstract

An innovative prestressed scaffolding system is provided to use triangular tendon supports and tendons in place of a plurality of struts for supporting the earth pressure applied during an excavation or an underground construction structure, thereby removing the obstacles of the construction, e.g., intermediate piles or struts, and contributing to an improvement of the constructional efficiency of the underground space and reduction of construction costs.

Description

PRESTRESSED SCAFFOLDING SYSTEM

FIELD OF THE INVENTION

The present invention relates to a scaffolding system that is temporarily placed

underground for preventing the collapse of excavated earth while an underground

structure is built and, more particularly, to a prestressed scaffolding system using

tendons with vertical piles (e.g., H-beams) and horizontal piles (e.g., wales), whereby

the number of struts supporting the vertical piles is considerably reduced.

BACKGROUND OF THE INVENTION

It is well known that excavation work for constructing a subway or a basement

of a building is started by excavating holes into the ground surface to a designed depth

on the basis of technical drawings, and then vertical piles are installed in the excavated

holes. After the installation of the vertical piles, excavation is partially carried out,

and then main girders and cover plates are placed. After the placement of the cover

plates, additional works are repeatedly performed by alternately excavating and

placing the struts.

Accordingly, in order to design a scaffolding system, the earth pressure on

each excavation level and load applied onto the struts are repeatedly calculated,

thereby enabling to design struts that can withstand the maximum load applied to the

beams. As a result, a large number of struts are required. In most cases, the struts are closely arranged, e.g., within intervals of approximately 2-3 m, for primarily

obstructing the delivery of construction materials in a working area, the transportation

of heavy equipments, and performance of the construction works. The struts also

give rise to a severe impediment to a molding or steel work when the main structure is

built. For example, a plurality of holes is unavoidably formed in the main structure,

such that the finished underground structure is subject to penetration of water.

In the conventional scaffolding system, steel H-piles are used as the vertical

piles, while concrete piles for filling concrete into the excavated holes may be used as

the vertical piles instead of using steel H-piles. Additionally, the steel piles and the

concrete piles may be simultaneously used, or sheet piles may be used. However, the

basic principle of supporting the load of excavated earth by making holes in the ground

and then forming a wall by piles is almost identical to that of the aforementioned

works. Preflexed beams may also be used as the vertical piles, and the H-piles may

be attached to the sheet piles to strengthen the sheet piles.

The earth anchor system is used for supporting steel piles in the scaffolding

system for constructing underground structures in place of systems using the aforesaid

struts. According to this system, inclined holes are drilled into the ground behind the

piles, tendons or high strength steel bars are inserted into the drilled holes, ends of the

inserted bars are anchored by a mechanical method or a chemical method such as

epoxy or cement grouting, and then the bars are tensioned and fixed to the steel piles.

This system has an advantage in that the inner space of the scaffolding system is very spacious, allowing the earth works and the support works to be easily performed. On

the other hand, there is a disadvantage in the system in that the works have to be

placed in the vicinity of private properties when this system is applied in a crowded

city, thus causing a lot of civil appeals from the neighbors. The high cost of the

construction is another disadvantage.

Korean Utility Model Registration No. 258949 discloses a method using truss

for removing struts, which pass across the excavated space of the scaffolding system.

This method is expected to be applied to a case where the depth of the excavated

ground is relatively shallow. H-beams are doubly placed in a grid-type near the earth

surface. The H-beams are reinforced with vertical beams and inclined beams so that

the earth pressure is supported by two floor trusses placed at the upper portion of the

scaffolding system. This method has been proposed to overcome difficulties in

excavating and constructing the structure, which occur due to the many struts of the

scaffolding system for supporting the ground. Consequently, this method is useful for

a construction to contain a wide structure at the bottom and a narrow structure at the

top of the excavated ground.

Korean Patent No. 188465, Korean Utility Model Registration No. 247053,

and Japanese Patent 837994 disclose a method for reinforcing a wale using

prestressing. In this method, an additional wale is placed on top of the existing wale

for tensioning the tendon and expanding the distance between the struts. This method

may be performed by using an additional wale or by reinforcing the flange of existing H-beams. These two methods are expected to be effective in increasing the distance

between the struts. However, since the tendon is linearly disposed, a constant support

bending moment occurs, which is different from the parabola-shaped moment

distribution generated on the wale by the earth pressure. Different moments and the

distribution thereof in relation to the load restrict the length of the reinforced wale.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a safe and effective method of

greatly reducing or removing the number of struts, which interfere in structure work

and cause an increase in construction costs, thereby obtaining an underground

construction space and minimizing construction costs.

In one preferred embodiment of the present invention, a prestressed

scaffolding system for supporting the excavated earth retaining wall by forming a

polygonal closed section comprises a prestressed wale comprising a plurality of

triangular tendon supports in the middle portion, a tendon-anchoring unit at both ends

of the wale, and a connecting brace for connecting the supports and the tendon-

anchoring unit. A strut is constituted by a truss or a plurality of H-beams or an H-

beam having a large cross section and strengthened for supporting the tendon-

anchoring unit.

The triangular tendon support is constituted by .a vertical member and an

inclined member, or only by vertical members, or only by inclined members for forming a triangle and supporting the wale. The triangular tendon support is

supported and connected by an intermediate pile and a support beam for the tendon

support.

The tendon-anchoring unit fastens a tendon and couples with the wale for

applying the compression force and also couples with the inclined or vertical member

for supporting the generated force.

BRD2F DESCRIPTION OF THE DRAWINGS

For a better understanding of the nature and objects of the present invention,

reference should be made to the following detailed description with the accompanying

drawings, in which:

FIG. 1 is a plan view of a scaffolding system applied to a closed section

according to an embodiment of the present invention; ^•

FIG. 2 is a plan view of a scaffolding system applied to another closed section

according to an embodiment of the present invention;

FIG. 3 is a cross-sectional view illustrating a scaffolding system applied to a

closed section according to an embodiment of the present invention;

FIG. 4 is a cross-sectional view of a scaffolding system applied to one

direction of a cross-section according to an embodiment of the present invention;

FIG. 5 is a cross-sectional view illustrating a scaffolding system applied to one

FIGS. 6a to 6d are detailed views of a tendon support used in the scaffolding system according to an embodiment of the present invention;

FIGS. 7a and 7b are detailed views of a corner tendon-anchoring unit used in

the scaffolding system according to an embodiment of the present invention;

FIGS. 8a to 8d are detailed views of a horizontal tendon-anchoring unit used

in the scaffolding system according to an embodiment of the present invention; and

FIG. 9 is a detailed view of a vertical tendon- anchoring unit used in the

scaffolding system according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention will now be described in

detail with reference to the attached drawings.

FIG. 1 is a plan view of the present invention applied to a closed section of an

architecture site. According to an exemplary embodiment of the present invention, a

prestressed wale 1 is disposed at four lateral sides of the closed section. A strut 3

made by a truss is placed at four corners and supports the wale. A conventional

corner support beam 5 is situated behind the strut. The prestressed wale 1 of each

lateral side includes three triangular tendon supports 12, a triangular anchoring unit 13,

and a connecting brace 10 for connecting the triangular tendon supports 12 and the

triangular anchoring unit 13. An intermediate pile 23 is equipped to support the

triangular tendon supports 12, and a support beam for the tendon support 16 is fixed at

the intermediate pile 23 by, for example, a bolt or welding. The support beam for the tendon support 16 supports the triangular tendon supports 12 during the installation of

the scaffolding system. The triangular tendon supports 12 and the support beam for

the tendon support 16 are connected via a U-bolt in order to prevent a vertical buckling

which may occur in the event of prestressing, carried out after the assembly work of

the scaffolding system.

The truss strut 3 of each corner is positioned between two triangular anchoring

units 13 to transmit the compression force of the anchoring units. The truss structure

of the embodiment of the present invention may be substituted by, for example, an H-

shaped steel having a large cross section, a plurality of H-shaped steels, or the like, as

long as the structure can withstand high compression force. The constructional

method of the corner support beam 5 behind the truss strut 3 is identical to that of the

conventional system and illustrated in the drawing for explaining the present invention.

The element numeral 60 is a tendon.

The configuration of FIG. 2 may be used when the excavating plane is small.

A corner anchoring unit 14 substitutes the conventional corner support beam 5 and

truss strut 3 of FIG. 1. A T-shaped connecting brace 11 is used where the interval

between the prestressed wale 1 and the corner anchoring unit is narrow. The rest of

the figures and methods for carrying out the construction work are identical to that of

FIG. 1.

FIG. 3 is a cross-sectional view of FIGS. 1 and 2 and illustrates a horizontal

prestressed scaffolding system 2 and main structure 7 according to an embodiment of the present invention. Unlike the conventional method, no equipment interferes the

middle portion of the system, and a wale 25 is arranged on four stages along the depth

of the excavated underground. A soldier pile 22 is located at a distal external wall in

a conventional way, and the wale 25 is mounted to support the soldier pile 22. The

support beam for the tendon support 16 and intermediate pile 23 are also illustrated in

the drawing.

FIG. 4, a cross-sectional view of a scaffolding system for a subway, includes a

main structure 8, vertical prestressed scaffolding system 6, and horizontal prestressed

scaffolding system 2. The horizontal prestressed scaffolding system 2 illustrated at

an upper portion of the drawing is identical in its figure and construction method to

that of the embodiment of FIG. 2, and thus, explanation of this system will be omitted.

However, the vertical prestressed scaffolding system 6 illustrated at a lower portion of

the drawing is supported at one side by a floor slab 9 of the main structure after the

slab is hardened. The other side of the system 6 is supported by a conventional

typical strut 26.

The vertical prestressed scaffolding system is useful when the main structure

is long such as a subway. In the vertical prestressed scaffolding system, a vertical H-

beam 19 is inserted from behind the pre-installed wale 25, and a short support 18 is

attached to the opposite side of the wale 25 for supporting the tension of the tendon 60.

The tendon is placed at both ends of the H-beam 19 and is fixed to a separate tendon-

anchoring unit 20, which is pre-coupled with the vertical H-beam. Thus, the anchoring unit of the lower end of the vertical prestressed scaffolding system is

configured to be supported by the hardened concrete slab 9 of the main structure, while

the anchoring unit of the upper end is supported by the typical strut 26. The element

numeral 24 is an earth retaining plate.

FIG. 5 is a plan view of FIG. 4 and is used when the excavating plane is long,

e.g., a subway or a channel construction. The prestressed wale 1 is arranged along

both lateral sides, and the truss strut 3 is located at each place where the tendon of the

prestressed wale is fixed. The configuration of the prestressed wale is identical to the

wale of the closed-section of FIG. 1, and thus, further explanation will be omitted.

The enlarged portion of the drawing illustrates the relative location of H-beam

19 in relation to the soldier piles 22, in which the H-beam 19 for the vertical

prestressed scaffolding system described in FIG. 4 is installed between the existing

soldier piles 22. In the vertical prestressed scaffolding system, the earth retaining

plate 24 should be mounted at a flange behind the existing vertical pile to thereby

allow the installation of the H-beam of the vertical prestressed scaffolding system.

Provided that the vertical pile is a sheet pile 21 in place of the soldier pile 22, the

vertical H-beam 19 is inserted into an empty space between the sheet pile 21 and the

wale 25.

FIGS. 6a to 6d illustrate various shapes and sizes of the triangular tendon

support utilized in the embodiments of the prestressed scaffolding system of the

present invention. The triangular tendon support is provided with a vertical member 32 and an inclined member 33 and is configured to reduce the number of support

points 31 being in contact with the tendon. The triangular tendon support is also

configured to support a wale 30 having a long length. When the compression force is

applied on the support point 31 making contact with the tendon, the force functions to

support the long wale 30 via the vertical member 32 and inclined member 33.

In FIG. 6a, two inclined members are welded or connected by a bolt (not

shown) to thereby form an isosceles triangle and support the wale 30 having a short

length. FIG. 6b is a second embodiment of the present invention and illustrates a pair

of inclined members 33 connected to each other at a 45 degree angle extended laterally

from the vertical member 32. The inclined and vertical members are all connected to

the wale 30 by, for example, a bolt or welding. According to a third embodiment in

relation to the case that the length of the wale 30 is long, two pairs of inclined

members 33 of FIG. 6c are connected to both lateral sides of the vertical member 32,

respectively. A plurality of vertical members and inclined members are used in FIG.

6d for supporting the long wale 30. The structure of the triangular tendon support is

not limited to the embodiments of the present invention, and thus, may be configured

to form a triangle and support the wale by using the vertical member and inclined

member, or only by vertical members, or only by inclined members.

FIGS. 7a and 7b are detailed views of the corner anchoring unit 14 of FIG. 2

that are designed to connect a wale 35 of the corner via reinforcing members 36 to

thereby secure the tendon 60. That is, when the tendon 60, which is used for constructing the prestressed scaffolding system, passes through the reinforcing

member 36 of the anchoring unit, the tendon is tensioned by a hydraulic jack 70. The

tensioned tendon is then fixed by an anchoring unit 71, which anchors the tendon.

The force pulled via the tendon transmits the compression force to an adjacent wale

(not shown) via a length adjusting unit 72, e.g., a precedent load jack or a screw jack.

As another embodiment of the present invention, the configuration of FIG. 7b is

adapted to anchor the tendon only by a reinforcing member 38 without a gusset plate.

The figures of the above embodiments may be varied in the scope of the basic concept

and function of the present invention. The reference numeral 39 refers to an inlet of

the anchoring unit.

FIGS. 8a to 8d illustrate various anchoring units of the horizontal prestressed

wale. FIG. 8a illustrates a small anchoring unit used when a small amount of tension

is applied thereto. The tendon 60 supporting a wale 41 is supported by an inclined

brace 43 or a vertical brace 44. The anchoring unit is formed with holes, thereby the

inclined brace 43 or vertical brace 44 may be inserted into the anchoring unit through

the holes as illustrated in the drawing, or may protrude out (not shown). The inlet 39

of the anchoring unit may preferably be formed in a curved shape in consideration of

the flexibility of the tendon. The tendon is fixed via the tendon-anchoring unit 73 at

an opposite side of the inlet 39. Further, the length adjusting unit 72 (e.g., precedent

load jack or screw jack) is equipped to add the compression force to the corner support

beam 5 after the tendon is tensioned. FIG. 8b illustrates an anchoring unit having an additional wale 42 for

strengthening the wale in a case where the wale 41 gets lengthened and the

compression force applied on the wale greatly increases thereby. FIG. 8b is identical

to FIG. 8a in that the curve-shaped inlet 39 is formed where the tendon 60 supporting

the wale 42 is inserted into the anchoring unit, and the tendon-anchoring unit 73 is

placed oppositely from the inlet 39. The difference from FIG. 8a is that the inclined

brace 43 for supporting the anchoring unit is doubly placed to withstand the increased

compression force and earth pressure. In addition, when the compression force is

applied on the double wale, the force may differently be applied on each wale, and thus

the compression force between the two wales is intended to be equally adjusted by

using the screw jack 72 of the high load.

FIG. 8c illustrates the triangular anchoring unit 13 of FIG. 1 configured to

secure the tendon 60, which supports the wale 41, via the tendon-anchoring unit 73.

FIG. 8c is also configured to transmit the load to the truss strut 3 supporting the

triangular anchoring unit 13. In the triangular anchoring unit, an inclined member 47

of H-shaped steel is disposed to form an isosceles triangle to withstand the load

applied on the unit. An apex at which these members contact each other is enhanced

by an appropriate gusset plate 46. A screw jack 74 is equipped to adjust the

compression force of the double wale, and the precedent load jack 72 is equipped to

add the compression force to the corner support beam 5. The screw jack 74 is further

connected with the truss strut, which supports the entire anchoring unit. A hydraulic jack 75 is provided to add a great amount of compression force between the anchoring

unit and the truss strut. That is, after the tendon is tensioned via the hydraulic jack 70,

the hydraulic jack 75 applies a compression force to the truss strut 3.

FIG 8d shows an anchoring unit used for the scaffolding system illustrated in

FIG. 4. The tendon 60 for supporting the wale 41 is tensioned via the hydraulic jack

70 and then secured by the tendon-anchoring unit 73. The tendon is designed to pass

through the inclined member 47 at its inlet portion. The truss strut 3 may be

connected with the anchoring unit by the screw jack 74 and hydraulic jack 75, or may

directly be connected without the aid of these members. The proper gusset plate 46 is

mounted for withstanding high compression force between a vertical member and a

horizontal member 48, which connects both sides of the anchoring unit. Since the

member receives only the prestressing force and the compression force is small, a

single wale is illustrated in the drawing. However, a double wale may preferably be

used depending on the case.

FIG. 9 is a detailed view of the anchoring unit 20 for the vertical prestressed

scaffolding system 6 illustrated in FIG. 4. Similar to the embodiment of FIG. 4, the

slab of the existing structure and intermediate strut are used as supports, and an H-

beam is inserted from behind the built wale. A short support is attached to the front

of the wale and the tendon fixed to the anchoring unit of both ends of the H-beam is

supported by the tendon support. This method is for a vertical prestressed scaffolding

system, which supports a channel-type excavating surface. In particular, the screw jack or precedent load jack 72, connected with the horizontal strut 26, is coupled with

the anchoring unit 20 If the anchoring unit 20 is placed at a lower end of the

scaffolding system, the anchoring unit 20 can directly contact the existing slab (not

shown) instead of the strut 26 The vertical H-beam is coupled to the anchoring unit

by being inserted into a vertical hole 50 This contact or coupling part may be firmly

connected by, for example, welding or a bolt, preferably by a bolt for facilitating the

disassembly of the members Once the tendon 60 for supporting the vertical H-beam

is inserted into the anchoring unit, the tendon is fixed by the tendon-anchoring unit 73

at an opposite side of the anchoring unit Accordingly, this anchoring unit is used in

the vertical prestressed scaffolding system, wherein the wale or the vertical beam is

removably manufactured

As apparent from the foregoing, there is an advantage in the prestressed

scaffolding system of the present invention in that vertical piles or horizontal beams

are prestressed by using a plurality of supports, anchoring units, and tendons The

number of struts and intermediate piles, which caused serious obstacles in carrying out

conventional constructional works, is considerably reduced

There is another advantage in that the excavation and scaffolding system

together with the construction cost are remarkably improved

Also, the formation of holes in the structure, which is inevitable in the

conventional scaffolding system, is effectively eliminated, thus facilitating the steel

reinforcing works and molding works, reducing the construction period and greatly improving the water-tightness and durability of the finished structure.

Claims

WHAT IS CLAIMED IS:

1. A scaffolding system for supporting the excavated earth retaining wall by

forming a polygonal closed section, comprising:

a prestressed wale comprising a plurality of triangular tendon supports in the

middle portion, a tendon-anchoring unit at both ends of said wale, and a connecting

brace for connecting said supports and said tendon-anchoring unit; and

a strut constituted by a truss or a plurality of H-beams or an H-beam having a

large cross section and strengthened for supporting said tendon-anchoring unit.

2. The system as defined in claim 1, wherein said triangular tendon support is

constituted by a vertical member and inclined member, or only by vertical members, or

only by inclined members for forming a triangle and supporting said wale.

3. The system as defined in claim 1, wherein said triangular tendon support is

support.

4. The system as defined in claim 1, wherein said tendon-anchoring unit fixes a

tendon and couples with said wale for applying the compression force and further

couples with said inclined member or vertical member for supporting the generated

force.

5. The system as defined in claim 4, wherein said tendon-anchoring unit forms

an isosceles triangle by using frame materials, the corner of said isosceles triangle is

reinforced by a reinforcing member, wherein said tendon is fixed at one corner of said

isosceles triangle and a member facing said corner is directly connected to a truss strut

or through a hydraulic jack or a screw jack, and the portion connected with said wale

has a length adjusting function.

6. The system as defined in claim 4, wherein said tendon-anchoring unit forms a

trapezoid by using frame materials, the corner of said trapezoid is reinforced by a

reinforcing member, said tendon is fixed at both corners, and the middle portion is

directly connected to said truss strut or through a hydraulic jack or a screw jack.

7. The system as defined in claim 4, wherein said tendon-anchoring unit may be

provided with an inclined or vertical strut, a tendon entered from one side of said

tendon-anchoring unit is fastened at an opposite side, a single wale or a double wale

may be supported by said tendon-anchoring unit, and said tendon-anchoring unit is

equipped with a screw jack or a precedent load jack having a length adjusting function.

8. A scaffolding system forming a polygonal closed section only by using a

prestressed wale comprising a plurality of triangular tendon supports in the middle portion, a tendon-anchoring unit at both ends of said wale, and a connecting brace for

connecting said supports and said tendon-anchoring unit.

9. The system as defined in claim 8, wherein said tendon- anchoring unit is a

corner anchoring unit and is designed to be connected with said wale and to fix a

tendon at both sides.

10. A vertical prestressed scaffolding system for supporting a channel type

excavating surface, wherein a slab of the structure and intermediate struts are used as

supports, an H-beam is inserted from behind a built wale, a short support is attached to

the front of said wale and supported by a tendon, wherein said tendon is fastened to an

anchoring unit of both ends of said wale.

11. The system as defined in claim 10, wherein said tendon-anchoring unit is for

a vertical prestressed scaffolding system in which said wale or vertical beam is

removably manufactured.