Torsional Constant for Beams in ETABs

sUPPOSE BEAM SIZE IS 8" X 51" AND f'c = 3000 psi First of ALL , PUT TOSRIONAL CONSTANT VALUE OF 1 IN ALL BEAM SECTIONS , HOW TU PUT TORSIONAL CONSTANT VALUE OF 1 IN BEAMS , FOR THIS , GO TO DEFINE THEN FRAME SECTIONS THEN SELECT BEAM SECTIONS ONE BY ONE AND CLICK ON MODIFY/SHOW PROPERTY THEN SET MODIFIERS THEN THERE PUT TORSIONAL CONSTANT VALUE OF 1 IN BOX NOW ACP = 8 X 51 AND PCP = 2(8+51) NOW PUT THESE VALUES IN PHI.TCR = 0.85 x 4 x (3000)^0.5 x (( 8X 51)^2)/(2(8+51)) = 262700.554 lb-inch = 21.89 kip-ft

Now for TU value , Run Model in ETABS , then dESIGN IT , after DESIGN , SEE ALL BEAMS OF SIZE 8X51 THEN FROM THESE ALL BEAMS RIGHT CLICK ON BEAMS AND SEE SUMMARY THEN SEE TU VALUE ONE BY ONE AND SELECT MAXIMUM TU VALUE FROM ALL 8 X 51 SIZE BEAMS SUPPOSE YOUR TU (MAX) FROM ALL 8 X 51 SIZE BEAMS COMES OUT TO BE 40 kips-ft then TORSIONAL CONSTANT VALUE = 21.89 / 40 = 0.547 NOW PUT THIS 0.547 VALUE IN ALL 8 X 51 SIZE BEAMS IF YOUR BEAM SIZE IS DIFFERENT AND ALSO f'c is DIFFERENT THEN DO ABOVE ALL STEPS FOR THAT BEAM SIZE AND f'C