METAL BUILDING SYSTEMS:SPECIFYING CRANE BUILDINGS.pdf
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1、CHAPTER 15 SPECIFYING CRANE BUILDINGS 15.1INTRODUCTION Two out of every five metal building systems are constructed for manufacturing facilities where cranes are frequently needed for material handling. A building crane is a complex structural system that consists of the actual crane with trolley an
2、d hoist, crane rails with their fastenings, crane run- way beams, structural supports, stops, and bumpers. A motorized crane would also include electri- cal and mechanical components that are not discussed here. Our discussion is further limited to interior building cranes. The main focus of this ch
3、apter is on proper integration of the crane and the metal building into one coordinated and interconnected system. Any attempts to add a heavy crane to the already designed and constructed pre-engineered building are likely to be fraught with frustration, high costs, and inefficiencies. If the requi
4、red planning is done beforehand, however, a cost-effective solution is much more likely. We are also interested in a relationship among the three main parties with design responsibilitiesarchitect-engineer, metal building manufacturer, and crane supplier. Occasionally, disputes arise when the contra
5、ct documents do not clearly delineate their respective roles in the project. 15.2BUILDING CRANES: TYPES AND SERVICE CLASSIFICATIONS Several types of cranes are suitable for industrial metal building systems, the most common being bridge cranes (either top-running or underhung), monorail, and jib cra
6、nes. Occasionally, stacker and gantry cranes may be required for unique warehousing and manufacturing needs. Jib, mono- rail, and bridge cranes are examined here in this sequencein order of increasing structural demands imposed on a pre-engineered structure. Constraints of space prevent us from disc
7、ussing gantry and stacker cranes, as well as conveyors and similar material handling systems. Within each type, the cranes are classified by the frequency and severity of use. Each crane must conform to one of six service classifications established by the Crane Manufacturers Association of America
8、(CMAA). The six classes are:A (standby or infrequent service), B (light), C (moderate), D (heavy), E (severe), and F (continuous severe). Guidance for assigning a service classification is contained in CMAA standards 701and 742and in the MBMA Manual.3The Manuals Design Practices apply only to the cr
9、anes with service clas- sifications A to D. Information on cranes with service classification E or F, including design loads and impact factors, is given in AISE Technical Report 13.4 Another way to classify the cranes is by kind of movementhand-geared or electric. Hand- geared cranes are physically
10、 pulled along the rail by the operator and are less expensive, but slower, 423 than electric cranes. Hand-geared cranes act with less impact on the structure than their faster-running electric cousins. The operator controlling an electrically powered crane can be either standing on the floor using a
11、 suspended pendant pushbutton station or sitting in a cab located on the moving bridge. 15.3JIB CRANES Jib cranes require relatively little planning from the pre-engineered building designer. Floor-mounted jib cranes (also known as pillar cranes) do not depend on the building superstructure for supp
12、ort and bear on their own foundations (Fig. 15.1). Column-mounted jib cranes, on the other hand, are either supported from or braced back to the metal building columns and thus impose certain requirements on strength and stiffness of the structure. For example, Ref. 5 recommends that building column
13、s sup- porting jib cranes be rigid enough so that the relative vertical deflection at the end of the boom is lim- ited to the boom length divided by 225. Floor-mounted jib cranes can rotate a full 360, while column-mounted cranes are usually limited to a 200 boom rotation. A jib crane picks up the l
14、oad by a trolley that travels on the bottom flange of the boom and carries a chain hoist. The hoist can be either electric or manually operated. Upon lifting the load, the boom rotates around the cranes stationary column and lowers the object to the desired location. These two operationstravel of th
15、e trolley and rotation of the jibare frequently performed manually. The length of the jib cranes boom varies from 8 to 20 ft. The lifting capacity ranges from 1?4to 5 tons,3with 1?2- and 1-ton jib cranes being the most popular. 424CHAPTER FIFTEEN FIGURE 15.1Floor-mounted jib crane. (American Crane a
16、nd Equipment Corp.) Common applications of jib cranes include machinery servicing operations, assembly lines, steam hammers, and loading docks. Sometimes, a pair of jib cranes and a monorail in combination with forklifts is sufficient to transport cargo from a loading dock to the area serviced by ov
17、erhead or stacker cranes. Inexpensive jib cranes can relieve main overhead cranes of much minor work that would tie them up for a long time. Manufacturers of floor-mounted jib cranes normally supply the suggested foundation sizes for their equipment, but the foundation design is still the specifying
18、 engineers responsibility. Whenever floor-mounted jib crane foundations are added to an existing metal building, care should be taken not to interrupt any floor ties or hairpins which could be located in the slab. Otherwise the lateral-load-resisting system of the building could be damaged. Obviousl
19、y, an addi- tion of the column-mounted crane needs to be approached even more carefully, because the existing building columns will probably need strengthening to resist the newly imposed loads. The basic design concepts for jib cranes are discussed in Ref. 6. 15.4MONORAILS 15.4.1The Monorail System
20、 The monorail crane is a familiar sight in many industrial plants, maintenance shops, and storage facilities. Monorails are cost-effective for applications requiring material transfer over predeter- mined routes without any side-to-side detours; their range of travel can be expanded with the help of
21、 switches and turntables. The monorail crane is essentially a hoist carried by trolley, the wheels of which ride on the bottom flange of a single runway beam. Monorails can be used to move the loads from 1 to 10 tons and can be either hand-geared or electric. Monorail runway beams have been traditio
22、nally made of standard wide-flange sections that could accept straight-tread wheels or from I beams supporting tapered-tread wheels. (The straight- tread wheel is essentially a short cylinder; the tapered-tread one is a short truncated cone.) Today, these standard beam sections are being increasingl
23、y displaced by proprietary built-up runway beam products with unequal flange configuration. Figure 15.2 illustrates one of these hard-alloy-steel inverted T products offered by crane manufacturers; it also shows the loads exerted on the runway by the hoist. Some advantages of the proprietary tracks
24、over rolled beams include better wear resistance, easier rolling, longer service life, and weight savings. The tracks are specially engineered to over- come such common problems of the standard shapes as excessive local flange bending due to wheel loading. The advantages of the proprietary products
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