Hi everyone!I am currently doing my final year project on the modal analysis of a truss footbridge and the aim of this study is to verify Staadpro Modal analysis with manual calculation of the frequency. It is found that the manual calculation follows the principle from the formula and Staadpro doesnt.
According to the formula, when the mass is increasing, the natural frequency will decrease and vice versa. While conducting the analysis from Staadpro, it shows that when the mass increases, natural frequency increases too. So my question is what verification can i do when both analysis are not getting the same value
Frequency as you know is affected by stiffness in addition to mass. So please check whether your stiffness are changing too with the mass. For example if you are increasing the member sizes, the mass would increase but the stiffness would increase too and so you may not see a decrease in frequency.
Also there are multiple verification examples on frequency analysis which are provided with the software, as marked next
Hi Sye, Thank you for your reply and explanation on the modal analysis. I will look it up and hopefully I get the answer that i needed. I will also try to look for the stiffness value in order to make the comparison
I appreciate your help and Thank you so much