STEEL DOME FOR WEST BADEN HOTEL 361 



in Fig. 169. The rise is between *4 and l /=> of the span. The outline 

 of the top chord approximates an elliptical curve, and the bottom chord 

 is parallel to the top chord throughout its length, except in the three end 

 panels on either side ; the depth of the arch being 10 ft. back to back 

 of chord angles. The web members are arranged as a single system of 

 the Pratt type, with substruts to the top chord as purlin supports. In 

 the end sections the arrangement is necessarily modified, the sharper 

 curvature of the chords being allowed for by more frequent strutting. 



The maximum stresses in the different members of the arch are 

 given on the right half of the rib in Fig. 169. They are obtained by 

 properly combining the dead load stresses with the stresses due to wind 

 blowing successively in opposiie directions in the plane of the rib in 

 question. The loads used in the calculation were a dead load separate- 

 ly estimated for each panel point, a variable snow load, heaviest at the 

 center of the roof, a wind load of 30 Ibs. per sq. ft. on a normal surface 

 reduced for inclination of the roof to the vertical. The makeup of the 

 members is given on the left half of the rib in Fig. 169. In the plan 

 part of the dome the method of bracing the ribs is fully shown. Suc- 

 cessive pairs of ribs are connected by bays of bracing in both upper 

 and lower chords. In the upper chord the I beam purlins are made use 

 of as struts, angle struts being used in the lower chord. The bracing 

 consists throughout of crossed adjustable rods. At the center, these 

 rods are carried over to a tangential attachment to the central drum, so 

 as to give more rigidity against twisting at the center. 



The central drum, 16 ft. in diameter by 10 ft. deep, has a web of 

 y% inch plate, with stiffener angles to which the ribs are attached. At 

 top and bottom the drum carries a flange plate 24 ins. x 3-16 ins. for 

 lateral stiffeners. In addition it is cross braced internally by four 

 diametrical frames intersecting at the center. The outer tie-girder, 

 which takes the thrust of the arch ribs, is a simple channel-shaped plate 

 girder, 24 ins. deep, as shown on the plan. The weight of the dome 

 complete, including framework and covering was 475,000 Ibs. This 

 makes the dead load about 15 Ibs. per square foot of horizontal projec- 

 tion of roof surface. 



Mr. Harrison Albright, of Charleston, W. Va., was the architect of 

 the building and the design of the steel dome was worked out by Mr. 

 Oliver J. Westcott, while in charge of the estimating department of 

 the Illinois Steel Company. The structural steel was furnished by the 

 Illinois Steel Co. 



