168 ILLINOIS ACADEMY OF SCIENCE 



WIND STRESSES IN STEEL SKELETON CON- 

 STRUCTION 



W. M. Wilson, University of Illinois 



I. DEFINITION OF STEEL SKELETON CONSTRUCTION 



By steel skeleton construction is meant that type of building 

 construction in which the frame is made up of a system of steel 

 columns and girders so planned that the loads from the walls 

 and floors are delivered by the girders to the columns at each 

 story. Each floor slab is supported on steel beams, and at 

 each floor the walls are supported on steel beams framed into 

 the columns, so that the floors and walls of one story, so far 

 as support is concerned, are entirely independent of the floors 

 and walls of all other stories. As seen in elevation, the steel 

 work of such a building is made up of a series of rectangular 

 frames. This is the type of construction that is used in prac- 

 tically all modern high buildings. 



II. HOW A STEEL SKELETON FRAME RESISTS WIND PRESSURE 



The wind pressure on a building acts upon the outside wall 

 and is delivered by the wall to the steel frame. It is cus- 

 tomary to assume that the wind load is applied to the steel 

 frame at the level of the floors only. A bent of a building 

 which is designed to resist the wind load is, therefore, con- 

 sidered as being acted upon by a series of concentrated hori- 

 zontal forces at the various floors. The force at the top of 

 the top story tends to make the top of the story more hori- 

 zontally relative to the bottom of the story. For a twenty- 

 story bent, the force at the top of the twentieth story and also 

 the one at the top of the nineteenth story, tend to make the top 

 of the nineteenth story move horizontally relative to the bot- 

 tom of that story. In the same way, for any story, all of the 

 forces above the story tend to make the top of the story in 

 question move horizontally relative to the bottom of that 

 story. The bottom of a story is prevented from moving hor- 

 izontally because of its connection to the foundation by means 

 of the intervening stories of the bent. For any story, there- 

 fore, the forces acting on the bent above the story in question 

 tend to move the top of the story horizontally in one direction, 

 whereas the stories below act horizontally upon the bottom 



