Cracked Section for concrete members

Question

Dear All, 
 I have modelled and applied Cracked section properties code specifies Is1893:2016 and in another model i have assigned Global Cracked section properties for the beams and columns. But the results and area of steel in columns and beams are reduced in the second case compared with the code Specified Cracked Section Properties. Please clarify whether my modelling issue or any thing?? 
 
 Thanks & Regards, 
 Anirudh

DSANJU · Answer

Please note that property reduction specification using MEMBER CRACKED CODE IS1893 2016 command will be imposed only on IS:1893 static and Response Spectrum load cases. Whereas, general property reduction specification will be applicable for all the active primary load cases. Thus, you are getting the difference in analysis results.

DSANJU · Answer

Please share your models with us.

Abhisek M · Answer

Hello, 
 As per code IS1893:2016 part 1, cracked section properties should be used for the elements when there will be seismic forces only. In a model apart from seismic load dead, live , wind etc load may present and there is no need to do the reduction for those load cases. When you use the code specific command, the program is intelligent enough to apply the the reduction only for the load cases where it gets IS1893:2016 relation. It does not apply any reduction for other cases as prescribed by the code. 
 On the other hand, when you apply the reduction through general properties it is applied to all the cases, that is not expected. To solve the issue, you need to change the reduction to 1.0 value. To do that in your model, before Ded load case 1 and just after the change command write, 
 MEMBER CRACKED 1001 TO 1097 2001 TO 2120 3001 TO 3112 4001 TO 4114 5001 TO 5036 - 5037 REDUCTION RIY 1.0 RIZ 1.0 1 TO 54 101 TO 154 201 TO 252 301 TO 352 401 402 419 420 427 428 432 433 438 - 439 TO 441 445 446 451 452 527 528 532 533 538 TO 541 545 546 551 - 552 REDUCTION RIY 1.0 RIZ 1.0 
 This will reset the reduction factors and rest of the load cases will be analyzed with full section properties. 
 Hope this will solve your issue.

Royal Civil Design Center · Answer

MEMBER CRACKED CODE IS1893 2016.std

Royal Civil Design Center · Answer

MEMBER CRACKED.std

Royal Civil Design Center · Answer