INSTRUCTIONS FOR THE ERECTION OF STUCTURAL STEEL. 479 



Piles should have a penetration of not less than 10 ft. in hard material and not less than 20 ft. 

 in soft material. For a steam hammer unity in the denominator in (l) should be replaced by -j^. 



The following specification is commonly used for piles for heavy falsework. 



All piles are to be spruce, yellow pine or oak, not less than 9 in. in diameter at the point and 

 not more than 14 in. in diameter at the butt. Piles are to be straight and sound, and free from 

 -i affecting their strength or durability. Piles are to be driven into hard bottom until they 

 do not move more than in. under the blow of a hammer weighing 2,000 Ib. and falling 25 ft. 



For specifications for falsework piles, see Chapter VII. 



A track pile driver is shown in Fig. 26. 



Design of Falsework. Falsework should be designed to carry the necessary loads. Where 

 the falsework is required to carry traffic it should be designed for the same allowable stresses as 

 are permitted for timber trestles and bridges, Table V, Chapter VII. Where the falsework does 

 not carry traffic the allowable stresses may be fifty per cent in excess of those permitted for perma- 

 nent structures. Care should be used in the design to prevent crushing of timber across the 

 grain. For details of timber trestles see Chapter VII. 



Traveler for Erection of Armory.* The new armory for the University of Illinois is 276 ft. 

 by 420 ft. in plan, the main drill hall being covered by three-hinged arches with a span 206 ft. 

 centers of end pins, a center height of 94 ft. 3 in., and are spaced 26 ft. 6 in. The arches have a 

 horizontal tie of two 4 in. X t in. bars, and are braced together in pairs. 



Each arch was shipped in eight segments, and the four sections for each half of the arch 

 were assembled and riveted up in horizontal position on the ground close to their final positions. 

 One side of the arch was then lifted into a vertical plane by a two-boom traveler, and its lower 

 end was fitted into the shoe and the shoe pin driven. The truss was then lowered on this pin 

 until its head rested on the ground, the arch segment being supported by guys at the sides. The 

 opposite segment of the arch was then raised and adjusted in the same way. The traveler was 

 then placed at the center of the arch, and the hoisting lines of the two booms were attached near 

 the ends of the two half-arches, which were then raised, the lower ends rotating on the shoe pins. 

 The arch was then held while the center pin was driven and the purlins were placed connecting it 

 to the adjacent arch. 



The traveler, Fig. 28, consisted of a steel tower about 40 ft. square and 33 ft. high to the 

 working deck. On this deck were two 4O-ft. masts wj$h A-frames, each carrying a 9O-ft. boom, so 

 that the top of the boom could reach about 20 ft. above the top of the arches, the maximum 

 height from the ground to the hoisting block being 125 ft. 



The traveler was supported on wood rollers on tracks of 16 X 16 in. timbers about 40 ft. 

 apart. The .upper part of the traveler was composed of two stiff-leg derricks of the type shown 

 in Fig. 29, with one stiff- leg and one sill removed from each, the masts being stepped on the 

 traveler frame and connected by bracing as shown. Each derrick had a lifting capacity of 15 tons, 

 and was operated by an engine of 8 H. P., the two engines being placed on a platform on the 

 lower sills of the traveler about 2 ft. from the ground. 



INSTRUCTIONS FOR THE ERECTION OF STRUCTURAL STEEL. The McClintic- 

 Marshall Construction Co. has issued the following instructions to foremen. 



In Order to Avoid Accidents, as Far as Possible, be Guided by the Following: 



I. See that Your Equipment is Sufficiently Strong. It is your duty to see that the equip- 

 ment and tools you use for each part of the work are sufficiently strong to handle the same safely. 



You should see that the derricks you use are amply strong for the loads to be lifted. The 

 goose neck and gudgeon pia are the critical points of a derrick. If you have any doubt about 

 the strength of the goose neck, provide heavy wire guys from gudgeon pin to sill at base of stiff 

 legs. Don't lift a ten ton load on a five ton derrick. The same thing applies to gin poles and 

 travelers. Don't overload your equipment and don't run any chances where life is endangered. 

 Be careful not to lift any but a light load on a derrick if the length of the boom exceeds seventy 

 times the least width or thickness of the boom; that is, if your boom is 12 in. X 14 in. the least 

 width is 12 in., you should not lift a heavy load on this boom if it is more than seventy feet in 

 length. 



* Engineering News, Dec. n, 1913. The structural steel was fabricated and erected and the 

 traveler was designed by the Morava Construction Co., Chicago, Illinois. 



