Patent Application
20210363711
Not Applicable
Not Applicable
This invention relates to the construction of bridges with prefabricated deck units.
For bridges with prefabricated full-depth concrete deck units, it is important to have a pre-compression force in the deck to ensure joint integrity in the service condition. The inventor has proposed several construction methods to apply compression force in prefabricated decks. U.S. Pat. Nos. 8,316,495 B2 and 7,475,446 B1 utilized post-tensioning to apply the needed deck pre-compression force. U.S. Pat. No. 8,266,751B2 proposed three methods to compress deck units with jacks. However, jacking methods presented in U.S. Pat. No. 8,266,751B2 carry some shortcomings, such as the need for extensive modifications to the supporting girder to accommodate the jacking frame attachment; the jacking frame extending outside the bridge deck limits (which can be impossible due to geometric limitations); the need for a large dimension setback of the bridge deck with time consuming cast-in-place deck closure after the jacking operation; or the need for a significant amount of work to remove the jacking frames.
The current invention provides a jacking force transfer system to further improve bridge construction with prefabricated deck units by minimizing the modification to the supporting girders. This allows all equipment and operations to come within the bridge deck limit; and requires no cast-in-place deck closure after the jacking operation.
The present invention provides a jacking force transfer method for bridges constructed with prefabricate deck units that:
a. Provides pre-compression across joints between deck units by reacting the deck with supporting bridge girders via the proposed jacking bracket;
b. Conducts deck stressing on top of installed deck units to improve work safety;
c. Operates entirely within the limit of bridge deck;
d. Requires minimum modifications to the bridge supporting girder and deck units; and
e. Requires no cast-in-place deck closure.
Further objects and advantages will become apparent from considering the ensuing description and drawings.
The present invention proposes practical methods to transfer jacking force to prefabricated bridge deck units using a novel bracket assembly, which simplifies field operation, improves safety and reduces construction schedule.
A preferred embodiment of the bridge with prefabricated deck units using the present invention of the jacking force transfer system is illustrated in
Girders 15 are placed on and supported by abutments 11. Prefabricated deck units are placed on top of girders 15, seating on a plurality of leveling devices that sets deck units 21 at the desired elevation and also allows for relative longitudinal motion between girders 15 and the prefabricated deck units 21.
Each prefabricated deck unit 21 consists of a plurality of pockets 22, similar to those used in conventional prefabricated deck placement, as shown in
Before deck jacking is applied; the right end deck unit 28 must be made composite to the supporting girder 15. At jacking time, the jack 32 is inflated and the jacking action causes compression in the deck and tension in the girder 15.
The jacking bracket 30 is the key component of the proposed jacking force transfer method. The jacking bracket 30 performs the following functions: 1) housing the jack 32, 2) transferring the force from the jack 32 to the girder reaction plate 52, and 3) resisting the overturning moment caused by jacking force. The jacking bracket 30 consists of: 1) the jacking bracket end bearing plate 36, which interacts with the jack 32 directly, 2) a pair of jacking bracket side plates 34, which forms the frame to resist the overturning moment, 3) the jacking 180 bracket bottom plate 35, which reinforces the jacking bracket side plates 34 and jacking bracket end bearing plate 36 as they react with the girder reaction plate 52, 4) hold down rods 55 at the end of the jacking bracket side plate 34, which connect to the girder during jacking operation, 5) diaphragms for jacking bracket 39, which connect both jacking bracket side plates 34.
The jacking bracket 30 is installed inside a deck opening in the deck jacking unit 27. The jacking bracket bottom plate 35 sets on the girder top flange 18. The jacking bracket end bearing plate 36 shall be aligned with the girder reaction plate 52 in both vertical and transverse directions. In order to transfer the jacking force to the girder, the lower end of the jacking bracket end bearing plate 36 shall engage the girder reaction plate 52 tightly along the longitudinal direction of the bridge. Filler plates for the reaction plate 53 may be used to fill the gap between the jacking bracket end bearing plate 36 and the girder reaction plate 52. Dimensions in gaps can vary due to construction tolerance, such as variation in girder position, variation in girder reaction plate placement and variation in deck unit placement. Therefore, filler plates 53 with various lengths, typically in ¼″ increment, are prepared for each project. After the deck jacking unit 27 is installed, the distance between the pocket for jacking brackets 33 and girder reaction plates 52 is measured and a filler plate 53 with appropriate length is installed. The jacking bracket 30 is then placed with the jacking bracket bottom plate 35 tightly against the filler plate 53.
The front end of the jacking bracket (point toward the middle of the bridge span) seats on the leveling block 56 with appropriate height so that the bottom of the jacking bracket side plate 34 is parallel to the deck. Afterward, hold-down rods and nuts 55 are installed to connect the jacking bracket front end to the girder. Hold-down rods shall be securely connected to the girder and are capable to take tension in vertical direction. Hold-down nuts shall be snuggly tightened only so that the jacking bracket 30 can have slight movement relative to the deck jacking unit 27 during jacking. Hold-down rods 55 are used to balance the overturning moment caused by jacking.
At the jacking time, a jack 32 is placed inside the jacking bracket 30 where the center of the jack 32 aligns with center of the deck unit 27 in the vertical direction. When the jack 32 is inflated, it pushes the jacking bracket end bearing plate 36 on the back end and the bearing plate embedded in the deck jacking unit 38 on the front end. The jacking force acting on the back end is transferred into girder tension via the girder reaction plate 52. The jacking force acting on the deck jacking unit 27 becomes compression across all joints 24 between prefabricated deck units and is balanced by the girder restraint force from deck end anchor unit 28 at the right end of the bridge. The offset between deck compression (at deck center) and girder reaction (at girder reaction plate 52) results in an overturning moment acting on the jacking bracket. Such overturning moment causes tension in hold-down rods 55 and compression between the jacking bracket 30 and the girder top flange 18.
Alternate embodiments for the present invention are described hereinafter:
The bridge layout can be a single span or multiple spans;
The girder 15 can be comprised of any other material or cross-section suitable to support the loads applied to these members such as steel I-girders, precast prestressed concrete beams, composite material I-girders, single or multiple box girders of steel or concrete, trusses, wood beams, etc.:
Though the preferred embodiment of the present invention is presented in the context of bridges, it is not limited to bridge applications. Any structural application requiring decking support by longitudinal structure members can utilize the present invention in alternate embodiments such as building floor systems and building roof systems;
Joints 24 between adjacent prefabricated concrete deck units can be of the match-cast type, with or without epoxy, or cast-in-place using concrete, grout or other suitable jointing materials. In the preferred embodiment, match-cast epoxy joints are used;
The preferred embodiment utilizes grouted haunch 17 and shear connector pockets 22 to restrain relative movement between the deck end anchor unit 28 and the girder 15 before jacking. Such restraint can be provided by other means such as installing steel restraining angles or providing another set of jacking brackets 30 on for deck end anchor units 28;
The preferred embodiment utilizes grout to make deck units composite with supporting girders 15. Any other materials such as UHPC or other means such as bolting or welding to prevent the deck unit from moving relatively to the girder can be utilized to form such composite action;
The preferred embodiment places the deck jacking unit 27 on the left end of the bridge and the deck end anchor unit 28 on the right end of the bridge. The reversed arrangement of the deck jacking unit 27 is also valid; and
The preferred embodiment utilizes one jacking bracket 30 per girder line 19. The deck compression can be applied without having jacking brackets 30 on each girder line 19.
The construction of the preferred embodiment in the context of the example bridge is illustrated hereinafter.
Abutments 11 are constructed. Girders 15 are erected. Prefabricated deck units 21 are erected, placing one unit adjacent to the previously erected one and applying epoxy to the adjacent faces of the two deck units. Means will be employed to provide a certain amount of compression over the epoxy joint to ensure the joint is properly set. This process is repeated until all deck units 21 are installed.
The deck end anchor unit 28 is made composite to the supporting girder 15 by grouting the shear connector pocket 22 and haunch 17. Such composite action is preferably made early since the deck jacking can't be applied before the grout reaches the required strength. After all deck units are erected, jacking brackets 30 are installed. Jacking operations consist of the following steps:
Install a jack 32 inside each jacking bracket 30;
Shim all jacks 32 tightly against the jacking bracket end bearing plate 36 and bearing plate for the deck jacking unit 38;
Gradually increase the jacking load to the design value; and
Lock all jacks 32 to maintain the jacking force.
After the jacking operation, shear connector pockets and haunches are grouted, except those occupied by jacking brackets 30. After the grout for shear connector and haunch reaches the specified strength, jacks 32 and jacking brackets 30 are released and removed, A secondary grouting will then be conducted to fill in the remaining opening left by the jacking brackets 30.
The operational description above is particular to the preferred embodiment of the present invention in the context of a single span bridge heretofore defined. Alternate materials, member shapes, number of spans, means of jacking, means 290 of making composite action between deck and girder, etc. can be used in employing the structural construction system of the present invention.
The present invention provides a practical method to transfer jacking forces to longitudinal compression in the prefabricated deck units when jacking the deck against the supporting girder. This significantly reduces the cost and time of construction required.
In conclusion, the present invention provides a jacking force transfer method used in combination with prefabricated bridge deck units that is simple to implement. The present invention can accommodate a variety of structural configurations and can be rapidly deployed.
Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the preferred embodiments of this invention at present. For example, as illustrated and described herein, the present invention can be employed a variety of bridge span layouts, a variety of girder types, and via a variety of means to make composite action between deck and girders.
Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.
This application claims the benefit of U.S. Provisional Application No. 62/704,703, filed May 22, 2020 by the present inventor.
| Number | Date | Country | |
|---|---|---|---|
| 62704703 | May 2020 | US |
