Patent Application
20050235595
NOT APPLICABLE
NOT APPLICABLE
NOT APPLICABLE
1. Field of the Invention
The present invention relates to systems and methods for a simplified framing system that facilitates cost-efficient, modular construction of large structures, and more particularly, to systems and methods for erecting large power generation plant structures.
2. Description of the Prior Art
Large structures such as, for example, power generation plants, petro-chemical facilities, mining and metal structures, industrial buildings, etc. are common. Many of these structures are now being built globally, especially in remote locations. Companies that obtain contracts for building such structures obviously want to minimize effort and expenses. Adding to the cost presumed, there often are time constraints involved in erecting structures. As steel erection is typically on the “critical path” of a project schedule, the required steel erection duration directly impacts the overall project schedule.
A common method for erecting such structures is a “stick-built” approach, where conventional columns, beams, girders, vertical braces, horizontal braces, deck, studs, grating pieces and others are assembled at the site. Consequently, this involves a large amount of labor. Additionally, tracking of the large number of members can be expensive and time-consuming.
A second method involves prefabrication of large-scale, three-dimensional modules. However, such modules are typically much more costly, due to special shipping requirements and the inevitable wasted space on the vehicles being used for the shipment.
Thus, improved systems and methods for cost-effectively and efficiently designing, fabricating and erecting large structures is needed.
Broadly, the present invention provides systems and methods wherein construction of structures is grossly simplified through the use of prefabricated, modular components fabricated to a maximum size that still may be stacked and then shipped conventionally on trucks. The components are erected to provide a simplified “super-frame,” which comprises a combined prefabricated primary support and roof system; shop-fabricated composite columns; and shop-fabricated floor panels that are assembled into bays within the primary support frame.
More particularly, the present invention provides a method of erecting a structure for generating power with a boiler, where the method comprises erecting a primary “super-frame” of only approximately 650-750 pieces, preferably only approximately 700 pieces. Components of the “super-frame” include combined boiler support/roof truss sections, large composite columns built-up from available shapes, deep horizontal trusses that consist of lacing adjacent floor beams and large floor panels (i.e., up to 12 feet×60 feet and including shop welded grating, checker plate or composite decking) that bear on column line members. The simplified “super-frame” greatly mitigates the required erection duration prior to commencement of the boiler.
In accordance with one aspect of the present invention, a majority of component connections are accomplished using bearing connections. While conventional steel structures involve members framing into one another, and thus lead to bolting and “fit-up” issues, all floor panels for this structure simply set on previously erected steel, with “stops” designed to prevent movement.
In accordance with another aspect of the present invention, the primary support is for a boiler for generating power and the support comprises using a common structure for both boiler support and roof framing.
In accordance with a further aspect of the present invention, no diagonal horizontal bracing is used. In adddition, no vertical bracing is used in one framing direction.
In accordance with yet another aspect of the present invention, components are sized to fit on a standard truck-trailer.
According to another aspect of the present invention, grating is used integrally with framing to create a horizontal diaphragm.
The following detailed description together with the accompanying drawings will provide a better understanding of the nature and advantages of the present invention.
The present invention provides systems and methods for erecting large structures or “superstructures” through the use of prefabricated modular components. While the present invention will be described with reference to a power-generating plant, those skilled in the art will understand that the present invention may be used for other large structures such as, for example, petro-chemical facilities, mining and metals facilities, industrial buildings, etc.
With reference to
To reduce the amount of time to assemble such a structure, the first two discrete sections may be assembled simultaneously. Generally, as an example for this type of power generating plant, only approximately 700 primary structural members are used. These members include building columns and column line members, boiler support systems, including trusses, stair tower modules, and soot blower floor grating panels and boiler front checker plate burner panels placed adjacent the boiler cavity. Preferably, these modules include 60-foot super columns.
The lower levels may be installed and assembled subsequent to assembly of the first two sections since it can be done at the same time as the primary boiler structure erection.
As may be seen in
Combined primary (in this case, boiler)/roof support structure 10 is illustrated in
The combined boiler roof system is sloped perpendicular to the centerline of the boiler. Thus, as may be seen in
The unique shop-fabricated grating panels preferably comprise two standard-weight parallel beams 30, 31 with perpendicular channels 32 across the beams to support the grating 33. This design essentially uses the channels and beam top flanges as a horizontal Vierendeel truss. Superimposed on this truss are shop-welded grating bearing bars that function as supplemental chord members to significantly increase the rigidity of the panel. Through use of the grating members, diaphragm stiffness may satisfy AISC stability bracing requirements.
Channels 32 also facilitate framing around pipe and other commodity penetrations and mitigate tripping hazards between adjacent panels by providing means of attaching overhanging grating from adjacent panels. The grating floor panels, which generally span from column line girder to column line girder, are installed more quickly and safely because they include bearing-type connections (see
While vertical Vierendeel trusses are common for prior art walkways, the present invention is actually utilizing them horizontally with grating as a reinforcing structural component. Preferably, the frames are coped seated connections and the channels located with web horizontals such that they have sufficient flexibility to align with channels of adjacent panels when brought together via the grating overlap. Preferably, the grating panels are sized for standard trucks. Thus, when stacked, the weight approximately equals the maximum capacity of the trucks such that the trucks are not shipping “air.”
Similar to the process of creating the grating panels, partially shop-fabricated stair towers are fabricated to a maximum extent that allows them to be shipped by rail or truck without special provisions. End frames include platform level grating and girts. Shop-assembled stair stringer frames also function as vertical bracing for open stair towers and the upper two tiers of enclosed stair towers.
Shop-fabricated composite panels, such as floor panels 13 and checkered plate burner panels 12, are created at the shop in order to avoid shipping beams that are loose with studs, decking, closure strips, etc. When these panels are assembled together to form a superstructure, concrete work, including rebar installation and concrete placement, may be performed at ground level or, depending upon panel height in the building, at the installed level.
Generally, standard tripper floor framing is conventionally “stick-built” steel. Due to the elevation of at least 150 feet above ground level or grade, the erection is generally time-consuming in crane usage as well as craft job hours. Thus, use of prefabricated panels allows for three framing panels to be used per bay as opposed to several hundered pieces (between 16 and 24 framing members, deck panels, edge angles, studs, closure strips, etc) when done with the prior art “stick-built” method. Composite decking is shop-installed within the panel periphery. Structural steel members are situated to function as pour stops. Panel bearing connections are used on primary steel beams. Reinforcing steel and concrete is placed at ground level or grade rather than more than 150 above grade. When the panels are used to form operating decks for turbine buildings, wood panels are generally placed over the openings to serve as a temporary cover to satisfy safety requirements.
Preferably, the checkered plate burner panels are sized (up to 12 feet by 60 feet maximum) to fit within a conventional oversized truck known in the art. Indeed, preferably all of the preformed components are sized to fit together on such a truck. The panels may be fabricated on a shop floor upside-down with all downward fillet welds. Preferably, bearing connections are used on primary steel beams to couple the panels to the superstructure.
Those skilled in the art will understand that many other components may be included in designing and erecting a superstructure in accordance with the present invention. For example, other components are often used in designing and erecting a power generation plant that uses a boiler as described herein but their description has been omitted for clarity. Preferably, most components used for designing and erecting a superstructure in accordance with the present invention are prefabricated and sized to fit together on a truck or other form of transportation. Additionally, those skilled in the art will understand that there are numerous ways to connect and interlink the various components.
Thus, the present invention provides a concept that uses larger building components, most of which have been wholly or partially preassembled off-site. With the present invention, no horizontal bracing is required on the sides of the boiler. This lack of heavy diaphragm is feasible by having each column line act as a horizontal moment frame, including the combined boiler/roof support at the top of the frame. Horizontal Vierendeel trusses serve to introduce structural redundancy and function as a light horizontal frame. Additionally, no east-west vertical bracing is required. This attribute avoids the numerous interferences and inefficient vertical bracing typically found with the large ductwork lying parallel to the boiler. Use of shop-fabricated 10-to-12-foot-deep vertical trusses that function as horizontals is also beneficial. The present invention also permits the extremely “commodity heavy” first hundred feet of the superstructure to be installed in parallel with the boiler. Each soot blower bay (generally 30 feet by 40 feet) is simply constructed with four framing/floor panels and a total of only four bolts.
Thus, the superstructure may be erected more quickly and efficiently in a cost-saving manner as opposed to the standard shipping of loose materials to the drop site and then assembling all the loose materials into the superstructure.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.
