WO2001096665A1

WO2001096665A1 - Method of constructing simple and continuous composite bridges

Info

Publication number: WO2001096665A1
Application number: PCT/KR2000/001501
Authority: WO
Inventors: Min Se Koo
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-06-08
Filing date: 2000-12-21
Publication date: 2001-12-20
Anticipated expiration: 2002-12-08
Also published as: JP2002004224A; CN1494628A; KR100522170B1; AU2001222332A1; JP3588325B2; CN1252354C; KR20030014686A

Abstract

Disclosed herein is a method of constructing simple and continuous composite bridges in which compressive stress is additionally introduced to an upper floor slab concrete in a negative moment region and the lower flange of a composite girder by lowering and lifting up end supports. The method includes the steps of providing first and second abutments, implanting a shape steel in said first abutment, simply resting a beam on said first and second abutments, connecting said shape steel to the lower flange of said beam, applying a connecting concrete to a portion ranging from an upper end of said beam first abutment to a neutral axis of said beam, lowering a support near said second abutment, applying a concrete to a portion ranging from an upper end of said connecting concrete to a bottom plate of said beam, applying a floor slab concrete to said beam, and lifting up the lowered support near said second abutment.

Description

METHOD OF CONSTRUCTING SIMPLE AND CONTINUOUS COMPOSITE BRIDGES

Technical Field

The present invention relates to a method of constructing simple and continuous composite bridges, such as simple and continuous preflex composite bridges, prestressed concrete (PSC) composite bridges, steel box girder bridges, plate girder bridges, and long span truss bridges.

Background Art

Of the conventional arts regarding a method of constructing simple and continuous composite bridges, for simple composite bridges Korean Unexamined

Pat. Publication No. 0250937 (hereinafter, referred to as "cited invention 1") discloses a method of constructing simple preflex composite bridges using a provisional support, and for continuous composite bridges Korean Unexamined Pat. Publication No. 105754 (hereinafter, referred to as "cited invention 2") discloses a continuous prestressed composite beam and method of constructing continuous prestressed composite beam structure using the same.

Figs, la to Id are views showing a conventional procedure for constructing composite bridges in accordance with the cited invention 1. With reference to these drawings, there will be described a method of constructing composite bridges in accordance with the cited invention 1.

As shown in Figs, la and lb, a preflex beam fabricated in a factory or field is rested on two abutments, a provisional support 51 is set, and a compressive stress is introduced to a lower concrete casing 52 by lifting up the provisional support 51 to compensate for the creep of initial concrete and the loss of compressive stress by drying contraction.

Thereafter, as shown in Fig. lc, while the provisional support is lifted up, an upper floor slab concrete 53 and a web concrete are applied and cured. Finally, as shown in Fig. Id, if the provisional support is removed after the upper concrete 53 is cured, a simple preflex composite bridge is completed.

However, in the method of the cited invention 1 described above, a provisional support is positioned under the center of a beam and an upward load is applied to the support. Accordingly, high costs are incurred by the use of a staging for a beam having a high overhead clearance, traffic is obstructed under the bridge, and the construction is complicated.

Additionally, in the method of the cited invention 1, the entire bridge behaves as a simple beam system, so the cross section of a composite girder should be enlarged to provide against the maximum positive moment, thereby causing a problem that excessive deflection occurs at the center of the beam owing to the enlargement of the cross section.

Figs. 2a to 2e and 3a to 3h are views showing methods of constructing a two-span continuous composite bridge and a three-span continuous composite bridge in accordance with the cited invention 2.

First of all, the method of constructing a two-span continuous composite bridge is described. As depicted in Fig. 2a, preflex beams made by span according to the design of the continuous beam are connected to each other over a second support 54 and rested on the second support 54. Thereafter, as shown in Fig. 2b, compressive stress is introduced to a lower casing concrete 52 by lifting up the second support 54. Thereafter, as shown in Fig. 2c, a floor slab concrete 53 is applied to the upper flange of a steel girder near a second support 54 and cured, and as shown in Fig. 2d, compressive moment is introduced to provide against negative moment created in the floor slab concrete near the second support 54. Thereafter, as illustrated in Fig. 2e, the two-span continuous preflex composite bridge is completed by applying the remaining floor slab concrete.

Figs. 3a to 3h are views showing a method of constructing a three-span continuous preflex composite bridge. For the three-span continuous composite bridge, as shown in Figs. 3a to 3d, a process performed near a second support 54 is the same as that of the two-span continuous preflex composite bridge shown in

Fig. 2. Thereafter, as shown in Figs. 3e to 3h, the three-span continuous preflex composite bridge is completed by lifting up a third support 55, applying a floor slab concrete 53, lowering the third support 53 and applying the remaining floor slab concrete.

However, the method of the cited invention 2 is problematic in that a construction joint is created owing to time difference in the application of a floor slab concrete to positive and negative moment regions and the difficulty and danger in construction occur owing to the lifting-up and lowering of supports being performed on bridge piers, that is, the second and third supports.

Additionally, in both methods of the cited inventions 1 and 2, a bridge bearing that serves as a medium for transmitting the load of its upper structure to its lower structure is comprised of a rotatable hinge support and a rotatable and movable roller support, so the bridge bearing should be continuously maintained to guarantee the safety of the upper structure of a bridge and may be damaged by an earthquake.

Disclosure of the Invention

Accordingly, the present invention lias been made to overcome the above problems occurring in the prior art, and an object of the present invention is to provide a practical and economical method of constructing simple and continuous composite bridges, which is capable of introducing compressive stress to the upper floor slab concrete in a negative moment region and the lower flange of a composite girder by lowering and lifting up a support on an abutment, that is, an end support while for a simple composite bridge a beam is completely integrated with an abutment or for a continuous composite bridge a beam is integrated with a bridge pier or not. In order to accomplish the above object, the present invention provides a method of constructing simple composite bridges, comprising the steps of providing first and second abutments; implanting a shape steel in a bridge seat portion of the first abutment; simply resting a beam on the first and second abutments; connecting the shape steel in the bridge seat portion to a lower flange of the beam; applying a connecting concrete to a portion ranging from an upper end of the first abutment to a neutral axis of the beam; lowering a support near the second abutment; applying a concrete to a portion ranging from an upper end of the connecting concrete to a bottom plate of the beam; applying a floor slab concrete to the beam; and lifting up the lowered support near the second abutment.

A method of constructing continuous composite bridges of the present invention may comprise the steps of: connecting at least two beams to each other and simply resting the connected beams near a first abutment, a second abutment and at least one imier bridge pier; lowering supports near said first and second abutments; applying a floor slab concrete to said beams; and lifting up the lowered supports.

In constructing a preflex composite girder bridge, the method further comprises the step of applying a lower casing concrete to the connected portions of the beams, before the step of simply resting the beams. Preferably, a method of constructing continuous composite bridges further comprises the steps of: implanting a shape steel in the coping portion of the inner bridge pier before the step of simply resting the beams; connecting the shape steel and the lower flanges of the beams after the step of simply resting the beams; applying a concrete to a portion ranging from the upper end of the coping portion of the inner bridge pier to the neutral axis of cross sections of the beams; and applying a concrete to a portion ranging from the upper end of the connecting concrete of the inner bridge pier to the bottom plates of the beams before the step of lowering supports near the first and second abutments.

In that case, the supports near the first and second abutments are simultaneously lowered when the supports near the first and second abutments are lowered, and the lowered supports near the first and second abutments are simultaneously lifted up when the supports near the first and second abutments are lifted up.

Alternatively, the supports near the first and second abutments are sequentially lowered when the supports near the first and second abutments are lowered, and the lowered supports near the first and second abutments are sequentially lifted up when the supports near the first and second abutments are lifted up.

In constructing a two-span continuous composite bridge, one of the supports near the first and second abutments is lowered when the supports near the first and second abutments are lowered, and the lowered one support is lifted up when the supports near the first and second abutments are lifted up.

In constructing a preflex or steel box girder bridge, the method further comprises the step of mounting one or more reinforcing members and studs to the webs of the beams. In constructing a prestressed concrete bridge, the method further comprises the step of exposing reinforcing rods out of the webs of the beams.

In constructing a prestressed concrete composite bridge, the method further comprises the steps of applying a floor slab concrete to the parapet wall of the first abutment and a positive moment region, and arranging connective reinforcing rods for connecting the parapet wall to the floor slab concrete; before the step of lowering the support near the second abutment.

In constructing a prestressed composite bridge, the method further comprises the steps of applying floor slab concretes to the positive moment region of the beams, and arranging connective reinforcing rods to com ect the floor slab concretes to one another; before the step of lowering the supports near the first and second abutments.

In such cases, the beams are connected at a position that is situated at an inner support, or a position that is situated by the right and left sides of an inner support.

Brief Description of the Drawings

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

Figs, la to Id are views showing a conventional procedure for constructing a simple preflex composite bridge;

Figs. 2a to 2e are views showing a conventional procedure for constructing a two-span continuous preflex composite bridge;

Figs. 3a to 3h are views showing a conventional procedure for constructing a three-span continuous preflex composite bridge;

Figs. 4a to 4d are views showing a state in which an abutment is integrated with a composite girder so as to construct a simple preflex composite bridge;

Figs. 5a to 5c are views showing a state in which an abutment is integrated with a composite girder so as to construct a simple steel box girder bridge;

Figs. 6a to 6c are views showing a state in which an abutment is integrated with a composite girder so as to construct a simple prestressed concrete composite bridge; Figs. 7a to 7d are views showing a procedure for constructing a simple preflex composite bridge in accordance with the present invention;

Figs. 8a to 8d are views showing a procedure for constructing a two-span continuous composite bridge in which a bridge pier is not integrated with a composite girder, in accordance with the present invention; Figs. 9a to 9d are views showing a procedure for constructing a three-span continuous composite bridge in which a bridge pier is not integrated with a composite girder, in accordance with the present invention;

Figs. 10a to 10c are views showing a state in which a beam is connected to another beam at an inner support during the construction of a multi-span continuous composite bridge in accordance with the present invention;

Figs. 1 la to 1 Id are views showing a state in which a composite girder is integrated with a bridge pier so as to construct a multi-span continuous preflex composite bridge in accordance with the present invention;

Figs. 12a to 12c are views showing a state in which a composite girder is integrated with a bridge pier so as to construct a multi-span continuous steel box girder bridge in accordance with the present invention; Figs. 13a to 13c are views showing a state in which a composite girder is integrated with a bridge pier so as to construct a multi-span prestressed concrete composite bridge in accordance with the present invention;

Figs. 14a to 14c are views showing a procedure for constructing a two- span continuous composite bridge in which a bridge pier is integrated with a composite girder, in accordance with the present invention; and

Figs. 15a to 15c are views showing a procedure for constructing a three- span continuous composite bridge in which a bridge pier is integrated with a composite girder, in accordance with the present invention. ^' *Description of reference numerals*

1 : bridge seat portion 2: beam 3 : shape steel

4: connecting plate 5: bolt 6: reinforcing rod

8: reinforcing member 9: stud 10: connecting concrete

11 : j oint concrete 12 : assembly step 13 : bridge pier 14: shape steel 15: welding material 60: lower flange

61 : floor slab 62: plate 63 : parapet wall

64: tensile reinforcing rod

Best Mode for Carrying Out the Invention

Hereinafter, with reference to accompanying drawings, a method of constructing simple and continuous composite bridges will be described. This constructing method can be applied to preflex composite bridges, prestressed concrete (PSC) composite bridges, steel box girder bridges, plate girder bridges, and long span truss bridges.

Figs. 4a to 7d are views showing methods of constructing simple composite bridges in which beams are integrated with abutments. Figs. 4a to 4d are views showing a method in which while a preflex beam 2 fabricated in the form of a simple beam is simply rested on a pair of abutments, a bridge seat portion 1 is coimected to the preflex beam 2 in one of the abutments. As shown in Fig. 4a, an H- or D-shaped steel 3 is implanted in the bridge seat portion 1, a connecting plate 4 is welded onto the shape steel 3 to connect the shape steel 3 to the lower flange 60 of a beam 2, and the shape steel 3 is coimected to the lower flange 60 of the beam 2 by bolts 5 or a welding process. In addition, a reinforcing member 8 is attached to the beam 2, and a plurality of studs 9 are secured onto a steel girder to improve the connection of the steel girder with a concrete.

Thereafter, as shown in Fig. 4b, a connecting concrete 10 is applied to a portion ranging from the upper end of the abutment to the neutral axis of the cross section of the preflex beam 2. In advance, a plurality of reinforcing rods 6 are exposed out of the connecting concrete 10 to connect the connecting concrete 10 to a later applied concrete.

Thereafter, as shown in Fig. 4c, a stationary support is accomplished by applying a concrete as well as an upper floor slab 61.

Fig. 4d is a plan view of the abutment employed in this method. Figs. 5a to 5c are views showing a method in which while a steel box girder 2 is simply rested on a pair of abutments, a bridge seat portion 1 is connected to the steel box girder 2 in one of the abutments.

Referring to Fig. 5a, similarly to Fig. 4a, an H- or D-shaped steel 3 is implanted in the upper portion of the bridge seat portion 1, a connecting plate 4 is welded onto the shape steel 3 to connect the shape steel 3 to the lower flange 60 of the steel box girder 2, and the shape steel 3 is connected to the lower flange 60 of the steel box girder 2 by bolts 5 or a welding process. In addition, reinforcing members 8 are attached to the steel box girder 2, and a plurality of studs 9 are secured onto a steel girder to improve the connection of the steel girder with a concrete.

Thereafter, as shown in Fig. 5b, a connecting concrete 10 is applied to a portion ranging from the upper end of the abutment to the neutral axis of the cross section of the steel box girder 2. In advance, a plurality of reinforcing rods 6 are exposed out of the connecting concrete 10 to connect the connecting concrete 10 to a later applied concrete.

Thereafter, as shown in Fig. 5c, a stationary support is completed by applying a concrete as well as an upper floor slab 61.

Figs. 6a to 6c are views showing a method of constructing a prestressed concrete composite bridge in which while a prestressed concrete (PSC) beam 2 is simply rested on a pair of abutments, a bridge seat portion 1 is connected to the PSC beam 2 in one of the abutments.

Referring to Fig. 6a, similarly to Figs. 4a and 5a, an H- or D-shaped steel

3 is implanted in the upper portion of the bridge seat portion 1, a connecting plate

4 is welded onto the shape steel 3 to connect the shape steel 3 to the PSC beam 2, and the shape steel 3 is connected to a plate 62 implanted in a concrete applied to the PSC beam 2 by a welding material 15.

Thereafter, as shown in Fig. 6b, a floor slab concrete is applied over a full span except about 10% of the span extended from a stationary support and a connecting concrete 10 is applied to a portion ranging from the upper end of the abutment to the neutral axis of the cross section of the PSC beam 2, to integrate the abutment with the PSC beam 2. A parapet wall 63 is provided. Additionally, in order to allow the connecting concrete 10 to be integrated with a later applied concrete, reinforcing rods 6 are exposed out of the connecting concrete 10 and the parapet wall 63 in advance. Tensile reinforcing rods 64 are arranged in the parapet wall 63 of the abutment and applied floor slab concrete to provide against tensile force created when a movable support is lowered during the construction.

About 10% of the span is a value that is determined through parameter study utilizing the length of a negative moment region as a variable in the case of a 30m bridge. The former length is a length that allows compressive stress to be effectively introduced, and can be varied depending upon bridge classes and materials of concretes used.

Thereafter, as shown in Fig. 6c, a stationary support is completed by applying a concrete as well as an upper floor slab 61.

Figs. 7a to 7d are views showing the method of constructing a simple composite bridge. Fig. 7a is a view showing a state in which a beam fabricated in a factory or field is simply rested on a pair of abutments with a stationary support 71 employed as one support and a movable support 72 employed as the other support. Fig. 7b is a view showing a state in which compressive stress is introduced to the lower flange of the beam by lowering the moving support 72, and moment distribution in this state. Fig. 7c is a view showing a state in which a floor slab concrete (61 in

Figs. 4c, 5c and 6c) is applied, and moment distribution in this state.

Fig. 7d is a view showing a state in which compressive stress corresponding to negative stress created in the stationary support 71 is introduced to the floor slab concrete by lifting up the lowered movable support 72 after the floor slab concrete is cured. Through the process shown in Fig. 7d, tensile stress is created in the lower flange. This tensile stress amounts to about 60 to 70% of compressive stress introduced during the lowering of the movable support 72 owing to the increased sectional strength after integration, resulting in the achievement of about 30 to 40% compressive prestressing effect. In the case of the PSC composite bridge, a floor slab concrete is applied over a full span except about 10% of the span extended from the stationary support before the lowering of the movable support, and a concrete is applied to the remaining portion after the lowering of the movable support.

In the simple composite bridge of the present invention, about 10%) of the span extended from the stationary support is made to have relatively large sectional area so as to provide against relatively large moment created on the stationary support, thereby allowing the composite bridge to have various cross sections.

Figs. 8a to 9d are views showing constructing methods for eliminating the problems of the cited invention 2 in which a construction joint may be created and an accident may occur owing to the lifting and lowering of the support on a bridge pier. As described above, these methods can be applied to preflex composite bridges, PSC composite bridges, steel box girder bridges, plate girder bridges, and long span truss bridges.

Figs. 8a to 8d are views showing a method of constructing two-span continuous composite bridges in which a bridge pier is not integrated with a composite girder. In the method of the cited invention 2, additional compressive stress is introduced to the lower flange in a positive moment region by lifting up the inner support, or the second support; whereas in this method of the present invention, as shown in Fig. 8a, a preflex beam or PSC beam fabricated in the form of a simple beam is rested on abutments and a bridge pier and connected to the bridge pier at an inner support 73 (as shown in Figs. 10a and 10c) or by the right or left side of the inner support 73 (as shown in Fig. 10b).

Fig. 8b is a view showing a state in which additional compressive stress is introduced into a lower flange by lowering the two end supports of a bridge on the abutments of the bridge, and moment distribution in this state. Fig. 8c is a view showing a state in which a floor slab concrete is applied while two end supports are lowered, and moment distribution in this state.

Fig. 8d is a view showing a state in which compressive stress corresponding to tensile stress created in an inner support after integration is introduced to the floor slab concrete by lifting up the lowered end supports 72 after the floor slab concrete is cured. Through the process shown in Fig. 8d, tensile stress is created in the lower flange, as in the simple span. This tensile stress amounts to about 60 to 70% of compressive stress introduced during the lowering of the end supports owing to the increased sectional strength after integration, resulting in the achievement of about 30 to 40%> compressive prestressing effect. In the case of the PSC composite bridge, a floor slab concrete is applied over a full span except about 10% of the span by both sides of an inner support before the lowering of the end supports, and a concrete is applied to the remaining portion after the lowering of the end supports.

Figs. 9a to 9d are views showing a method of constructing three-span continuous composite bridges in which a bridge pier is not integrated with a composite girder.

Fig. 9a is a view showing a state, in which preflex beams or PSC beams are rested on abutments and a bridge pier, and, as shown in Figs. 10a, 10b and 10c, are connected to one another at an inner support or at a position by the right or left side of a bridge pier in the negative moment area of the entire bridge away from the inner support. As described above, in the method of the cited invention 2, additional compressive stress is introduced to the lower flange in a positive moment region by sequentially lifting up the second support 73 and the third support 74; whereas in this method of the present invention, as shown in Fig. 9b, the same effect is achieved by simultaneously or sequentially lowering both end supports.

Fig. 9c is a view showing a state in which a floor slab concrete is applied while two end supports are lowered, and moment distribution in this state.

Fig. 9d is a view showing a state in which compressive stress corresponding to tensile stress created in an inner support after integration is introduced to the floor slab concrete by lifting up the lowered end supports after the floor slab concrete is cured. In this case, tensile stress is created in the lower flange, as in the above embodiments. This tensile stress amounts to about 60 to 70%) of compressive stress introduced during the lowering of the end supports owing to the increased sectional strength after integration, resulting in the achievement of about 30 to 40% compressive prestressing effect. For the three- span continuous composite bridge of the present invention in which each bridge pier is not integrated with each composite girder, the positive moment created in an inner span is only about 1/5 of the absolute value of the maximum negative moment created on the inner support owing to the structural characteristics of a continuous beam, so the continuous composite bridge has a sufficient compressive stress without the introduction of additional compressive prestressing during the lifting and lowering of the end supports.

In the case of the PSC composite bridge, a floor slab concrete is applied over a full span except about 10%> of the span by both sides of its inner support before the lowering of the end supports, and a concrete is applied to the remaining portion after the lowering of the end supports.

Fig. 10a is a detailed view showing a state in which for the preflex composite bridge two beams 2 are connected to each other by means of a plurality of connecting plates 4 and bolts 5. In the method of the cited invention 2 described in "Prior art" part, after a support is lifted up, a floor slab concrete is applied to a negative moment region and a joint concrete 11 is applied over an inner support; whereas in the method of the present invention, before the end supports are lowered, a joint concrete 11 is applied over the inner support.

Fig. 10b is a detailed view showing another connecting method for the preflex composite bridge in which two beams 2 are connected at a position by the sides of the inner support to each other by means of a plurality of connecting plates

4 and bolts 5. In the method of the cited invention 2, after the support is lifted up, the floor slab concrete is applied to the negative moment region and the joint concrete is applied to an inner support; whereas in the method of the present invention, before the end supports are lowered, the joint concrete 11 is applied to the inner support.

Fig. 10c is a detailed view showing a state in which for a PSC composite bridge two beams 2 are connected to each other at the inner support of the bridge. In fabricating each PSC beam, a plurality of bolts 5 are previously implanted in the concrete of the upper flange of the PSC beam; in connecting the beams, the bolts are tightened to a connecting plate 4. Additionally, two PSC beams are connected by means of connective reinforcing rods 6 in the upper flanges of the PSC beams. This construction is provided to stabilize the entire composite girder, though the connective reinforcing rods 6 do not play an important role because of the lower flanges near the inner support being a compressive side. In order to facilitate the connection of the beams, an assembly step 12 is formed along the central axis of the beams and the gap between the beams is filled with non-contractile mortar.

The steel box girder bridge has no connecting portion near its inner support, so the method of the present invention can be applied to the steel box girder bridge.

Figs. 11a to 15c are views showing the different methods of constructing multi-span continuous composite bridges. These methods can provide for the shortcomings of a bridge bearing and damage due to earthquake by integrating each beam and each bridge pier. These integration methods and construction methods will be described hereinafter.

Referring to Fig. 11a, for a preflex composite bridge, two beams 2 fabricated in the form of simple beams, as shown in Fig. 10a, are connected to each other by means of a plurality of connecting plates 4 and bolts 5 and laid on a D-shaped steel 14, and the D-shaped steel 14 is coimected to the lower flange 60 of a steel girder through a welding process. In order to help the bridge pier 13 and the lower casing concretes 52 of the beams 2 to be connected to a connecting concrete 10 applied in the next stage, reinforcing rods 6 are exposed out of the bridge pier 13 and the lower casing concretes 52 of the beams 2 in advance. As shown in Fig. 1 lb, a concrete is applied to the remaining portion of the beams 2, the connecting concrete 10 is applied to a portion ranging from the upper end of the bridge pier 13 to the neutral axis of the cross section of the beams 2, and reinforcing rods 6 are exposed out of the connecting concrete 10 to help the connecting concrete 10 to be connected with a later applied concrete.

As shown in Fig. l ie, the multi-span continuous composite bridge in which each beam 2 is integrated with each bridge pier 13 can be completed by applying a floor slab concrete, a web concrete and the remaining upper end concrete of the bridge pier while the end supports of the multi-span continuous composite bridge are lowered. Fig. 1 Id is a plan view showing the D-shaped steel 14 implanted in the bridge pier 13.

Figs. 12a to 12c are views showing a method of constructing steel box girder bridges.

As shown in Fig. 12a, a steel box girder 2, or a segment corresponding to a negative moment region is laid on a D-shaped steel 14 previously implanted in a bridge pier 13, and the D-shaped steel 14 is connected to the lower flange 60 of the steel box girder 2 by a welding process. As shown in Fig. 12b, a connecting concrete 10 is applied to a portion ranging from the upper end of the bridge pier 13 to the neutral axis of the cross section of the steel box girder 2 to integrate the bridge pier 13 with the steel box girder 2. In this case, reinforcing rods 6 are exposed out of the bridge pier 13, reinforcing members 8 are attached to the web portions of the steel box girder 2 to reinforce the steel box girder 2, and studs 9 are implanted in the upper flange and web of the steel box girder 2 to allow concretes to be securely attached to the steel box girder 2. In particular, since the connecting portion of a composite girder does not exist in the steel box girder bridge, the methods of the present invention can be easily applied to the steel box girder bridge.

As illustrated in Fig. 12c, the multi-span continuous steel box girder bridge in which each girder is integrated with each bridge pier can be completed by applying a floor slab concrete and the remaining upper end concrete of the bridge pier while the end supports of the composite bridge are lowered.

Figs. 13a to 13c are views showing a method of constructing PSC composite bridges. As shown in Fig. 13a, two PSC beams connected to each other as in Fig.

13a are laid on a D-shaped steel 14 previously implanted in a bridge pier 13, and the D-shaped steel 14 is connected to a connecting plate 4 implanted in the concrete of a lower flange by a welding process. As shown in Fig. 13b, a floor slab concrete is applied over a full span except about 10% of the span extended by both sides of its inner support and a connecting concrete 10 is applied to a portion ranging from the upper end of the bridge pier 13 to the neutral axis of the cross section of the PSC beam 2, to integrate the bridge pier 13 with the PSC beam 2. Additionally, in order to allow the connecting concrete 10 to be integrated with a later applied concrete, reinforcing rods 6 are exposed out of the bridge pier 13. Floor slab concretes applied to the remaining portion except for the inner support are coimected to one another by tensile reinforcing rods 64 previously implanted. This construction is made to provide against tensile stress generated while both end supports are lowered during the construction. About 10% of the span is a value that is determined through parameter study utilizing the length of a negative moment region as a variable in the case of a 30m bridge. The former length is a length that allows compressive stress to be effectively introduced, and can be varied depending upon bridge classes and materials of concretes used.

As illustrated in Fig. 13c, the multi-span continuous PSC composite bridge in which each girder is integrated with each bridge pier can be completed by applying the remaimng floor slab concrete and the remaining upper end concrete of the bridge pier while the end supports of the composite bridge are lowered. Figs. 14a to 14c are views showing a method of constructing two-span continuous composite bridges.

Fig. 14a is a view showing a state in which additional compressive stress is introduced into a lower flange by simultaneously or sequentially lowering the two end supports of an entire structure after a composite girder is connected to a bridge pier as shown in Figs, l ib, 12b and 13b,, and moment distribution in this state.

Fig. 14b is a view showing a state in which a floor slab concrete is applied while the two end supports are lowered,, and moment distribution in this state. In this case, as illustrated in Figs, lie, 12c and 13c, the bridge pier is completely integrated with the composite girder by applying the floor slab concrete and the remaining upper end concrete of the bridge pier.

Fig. 14c is a view showing a state in which compressive stress corresponding to tensile stress created in the floor slab concrete in a negative moment region caused by design live loads is introduced by simultaneously or sequentially lifting up the lowered two end supports after the floor slab concrete and the upper end concrete of the bridge pier are cured. Through this process, tensile stress is created in the lower flange portion in a positive moment region. This tensile stress amounts to about 60 to 70% of compressive stress introduced during the lowering of the end supports owing to the increased sectional strength after integration, resulting in the achievement of about 30 to 40% compressive prestressing effect.

For a PSC composite bridge, a floor slab concrete is applied over a full span except about 10% of the span by both sides of an inner support before the lowering of the end supports, and a concrete is applied to the remaining portion after the lowering of the end supports.

For a two-span continuous composite bridge shown in Figs. 8 and 14, the same effect can be achieved by lowering and lifting up one of the two end supports depending upon the circumstances of a field. However, in this case, the amount of being lowered and lifted up should be doubled in comparison with the case of simultaneously or sequentially lowering and lifting up both end supports. Figs. 15a to 15c are views showing a method of constructing three-span continuous composite bridges in which a bridge pier is integrated with a composite girder.

Fig. 15a is a view showing a state in which additional compressive stress is introduced into a lower flange by simultaneously or sequentially lowering the two end supports of an entire structure after a composite girder is connected to a bridge pier as shown in Figs, l ib, 12b and 13b„ and moment distribution in this state.

Fig. 15b is a view showing a state in which a floor slab concrete is applied while the two end supports are lowered,, and moment distribution in this state. In this case, as illustrated in Figs, l ie, 12c and 13c, the bridge pier is completely integrated with the composite girder by applying the floor slab concrete and the remaining upper end concrete of the bridge pier.

Fig. 15c is a view showing a state in which compressive stress corresponding to tensile stress created in the floor slab concrete portion in a negative moment region caused by design live loads is introduced by simultaneously or sequentially lifting up the lowered two end supports after the floor slab concrete and the upper end concrete of the bridge pier are cured. As in the two-span continuous composite bridge, tensile stress is created in the lower flange portion. This tensile stress amounts to about 60 to 70% of compressive stress introduced during the lowering of the end supports owing to the increased sectional strength after integration, resulting in the achievement of about 30 to 40% compressive prestressing effect.

For the three-span continuous composite bridge in which a bridge pier is integrated with a composite girder, the positive moment created in the inner span is only about 1/3.5 of the absolute value of the maximum negative moment, so the bridge has a sufficient compressive stress even though additional compressive prestress is not introduced during the lowering and lifting up of both end supports.

Additionally, in the multi-span continuous composite bridge in which a bridge pier is integrated with a composite girder in accordance with the present invention, about 10% of the span by both sides of the bridge pier is made to have a relatively large sectional area so as to provide against relatively large moment generated near the integrated bridge pier and composite girder, thereby allowing the composite bridge to have various cross sections.

Additionally, in the simple and continuous composite bridge of the present invention, the amount of compressive prestress can be adjusted by reducing the amount of lifting-up of the end supports to an amount less than that of the lowering of the end supports.

Industrial Applicability

In a method of constructing simple and continuous composite bridges in accordance with the present invention, floor slab concrete is applied at the same time and the lowering and lifting-up operations of a support is performed on an abutment near the ground, so there can be overcome the shortcomings of the cited invention 2 that a construction joint is created owing to time difference in the application of a floor slab concrete to positive and negative moment regions and the difficulty and danger in construction occur owing to the lifting-up and lowering of supports being performed on a bridge pier.

In the method of constructing a simple composite bridge in which an upper composite girder is integrated with an abutment and the method of constructing a multi-span continuous composite bridge in which an upper girder is integrated with a bridge pier, the following effects can be achieved except for the above-described effects. That is, the single structure, two-span structure and three-span structure of the cited invention are a determinated structure, a first order indeterminated structure and a three order inderminated structure, while the single structure, two-span structure and three-span structure of the present invention are a first order indeterminated structure, a five order indeterminated structure and a eight order inderminated structure, thereby improving a vibration reduction effect and earthquake-proof by due to energy dispersion by plasticity. Additionally, relatively great moment is distributed over a lower structure by the integration of the composite girder and the lower structure, so the burden of a beam against external force is reduced, thereby reducing the height of the girder and extending the length of a span and acquiring an economical cross section.

Additionally, the number of bridge bearings, which are an important cause of deterioration of a bridge and require continuous maintenance, can be reduced, so the additional economic savings can be realized.

Claims

1. A method of constructing simple composite bridges, comprising the steps of: providing first and second abutments; implanting a shape steel in a bridge seat portion of said first abutment; simply resting a beam on said first and second abutments; connecting said shape steel in the bridge seat portion to a lower flange of said beam; applying a connecting concrete to a portion ranging from an upper end of said first abutment to a neutral axis of said beam; lowering a support near said second abutment; applying a concrete to a portion ranging from an upper end of said connecting concrete to a bottom plate of said beam; applying a floor slab concrete to said beam; and lifting up the lowered support near said second abutment.

2. A method of constructing continuous composite bridges, comprising the steps of: connecting at least two beams to each other and simply resting the connected beams near a first abutment, a second abutment and at least one inner bridge pier; lowering supports near said first and second abutments; applying a floor slab concrete to said beams; and lifting up the lowered supports.

3. The method according to claim 2, further comprising the step of applying a lower casing concrete to the connected portions of said beams, before the step of simply resting said beams, so as to construct a preflex composite girder bridge.

4. The method according to claim 2, further comprising the steps of: implanting a shape steel in the coping portion of said inner bridge pier before said step of simply resting said beams; connecting said shape steel and the lower flanges of said beams after said step of simply resting said beams; applying a concrete to a portion ranging from the upper end of said coping portion of said inner bridge pier to the neutral axis of cross sections of said beams; and applying a concrete to a portion ranging from the upper end of the coimecting concrete of said inner bridge pier to the bottom plates of said beams before said step of lowering supports near said first and second abutments.

5. The method according to claim 2 or 4, wherein said supports near said first and second abutments are simultaneously lowered when said supports near said first and second abutments are lowered, and wherein said lowered supports near said first and second abutments are simultaneously lifted up when said supports near said first and second abutments are lifted up.

6. The method according to claim 2 or 4, wherein said supports near said first and second abutments are sequentially lowered when said supports near said first and second abutments are lowered, and wherein said lowered supports near said first and second abutments are sequentially lifted up when said supports near said first and second abutments are lifted up.

7. The method according to claim 2 or 4, wherein, in order to construct a two-span continuous composite bridge, one of said supports near said first and second abutments is lowered when said supports near said first and second abutments are lowered, and said lowered one support is lifted up when said supports near said first and second abutments are lifted up.

8. The method according to claim 1 or 4, further comprising the step of mounting one or more reinforcing members and studs to the webs of said beams, so as to construct a preflex or steel box girder bridge.

9. The method according to claim 1 or 4, further comprising the step of exposing reinforcing rods out of the webs of said beams, so as to construct a prestressed concrete bridge.

10. The method according to claim 1, further comprising the steps of, applying a floor slab concrete to the parapet wall of said first abutment and a positive moment region, and arranging connective reinforcing rods for connecting said parapet wall to said floor slab concrete; before said step of lowering said support near said second abutment, so as to construct a prestressed concrete composite bridge.

11. The method according to claim 2 or 4, further comprising the steps of, applying floor slab concretes to the positive moment region of said beams, and arranging connective reinforcing rods to connect said floor slab concretes to one another; before the step of lowering said supports near said first and second abutments, so as to construct a prestressed composite bridge.

12. The method according to claim 2, wherein said beams are coimected at a position that is situated at an inner support.

13. The method according to claim 2, wherein said beams are connected at a position that is situated by the right and left sides of an inner support.