<P> Hat trusses ( or `` outrigger truss '' ) located from the 107th floor to the top of the buildings were designed to support a tall communication antenna on top of each building . Only 1 WTC ( north tower ) actually had an antenna fitted ; it was added in 1978 . The truss system consisted of six trusses along the long axis of the core and four along the short axis . This truss system allowed some load redistribution between the perimeter and core columns and supported the transmission tower . </P>
<P> Hat trusses ( or `` outrigger truss '' ) located from the 107th floor to the top of the buildings were designed to support a tall communication antenna on top of each building . Only 1 WTC ( north tower ) actually had an antenna fitted ; it was added in 1978 . The truss system consisted of six trusses along the long axis of the core and four along the short axis . This truss system allowed some load redistribution between the perimeter and core columns and supported the transmission tower . </P>
what was on the top of the world trade center
what was on the top of the world trade center
a tall communication antenna
a tall communication antenna