Cracked/Uncracked stiffness in RSA
Posted: 12 Jan 2023, 09:40
Hi SeismoSoft team,
I'm doing a RSA in a model of a 12-storey RC building (Example from App.B FEMA P-2091). In the Project Settings, I have set a 50% of the cracked by the uncracked stiffness for columns and walls, and a 30% for beams.
After running the analysis, I want to check the total base shear, which I obtained from 'Global Response Parameters' and then 'Forces and Moments at Supports', calling this one BS1. Then, to double-check my values, I check the sum of shear in each vertical element at the base, which I obtained from 'Element Action Effects' and then 'Frame Forces', where I oriented each local axes of each element in the same direction in order to get a cumulative correspondingly, calling this one BS2.
I was expecting that both values should be the same or maybe some small variations but, comparing BS1 with BS2, I obtained BS1 = 2*BS2 exactly, in other words, 50%*BS1 = BS2. Then I tried with 70% instead of 50% for the vertical elements and I got 70%*BS1 = BS2. Also, I tried with 100% (uncracked section) instead of 50% for the vertical elements and I got BS1 = BS2.
Is it correct? should I get the same value for BS1 and BS2? How can/should I calibrate the model with cracked stiffness in order to get the same values in both cases?
Thanks in advance.
I'm doing a RSA in a model of a 12-storey RC building (Example from App.B FEMA P-2091). In the Project Settings, I have set a 50% of the cracked by the uncracked stiffness for columns and walls, and a 30% for beams.
After running the analysis, I want to check the total base shear, which I obtained from 'Global Response Parameters' and then 'Forces and Moments at Supports', calling this one BS1. Then, to double-check my values, I check the sum of shear in each vertical element at the base, which I obtained from 'Element Action Effects' and then 'Frame Forces', where I oriented each local axes of each element in the same direction in order to get a cumulative correspondingly, calling this one BS2.
I was expecting that both values should be the same or maybe some small variations but, comparing BS1 with BS2, I obtained BS1 = 2*BS2 exactly, in other words, 50%*BS1 = BS2. Then I tried with 70% instead of 50% for the vertical elements and I got 70%*BS1 = BS2. Also, I tried with 100% (uncracked section) instead of 50% for the vertical elements and I got BS1 = BS2.
Is it correct? should I get the same value for BS1 and BS2? How can/should I calibrate the model with cracked stiffness in order to get the same values in both cases?
Thanks in advance.