The difference between the road and rail trusses typically was the road bridges had the
bottom chord (tension) constructed from timber whereas the rail bridges had the
bottom chord constructed from steel.
It is to be noted here that, for Figure 2, the fundamental mode shape corresponding to the
bottom chord is used, whereas, in Figure 3, the fundamental mode shape corresponding to the top chord is utilized for damage localization.
The
bottom chord of the trusses gets into a zone of the neutral line, therefore the internal forces are insignificant and even change the sign.
"The
bottom chord, especially the middle truss, is discolored due to severe exposure to the fire," they noted.
The optimal cross-sectional areas of the
bottom chord and vertical web elements are found to be smaller, meanwhile cross-sectional areas of the top chord and inclined web elements--bigger in the case C2.
"Oval hubs in the
bottom chord of the domes' ribs allowed us to use two rectangular bars in parallel, reducing the overall arch count, and increasing structural efficiency." Gracia explained.
The
bottom chord adopts a channel cross section with a beam height of 1.5 m, and the beam end is 2.0 m thick.
The chambers of single cable and cable truss
bottom chord f are equal to 20 m.
At each of the seven spacer locations, paint glue on a spacer and the
bottom chord where it fits, and position the spacer on the
bottom chord, against the spacer stops.