Kelles
- 17
- 0
Homework Statement
Hello everyone, as you can see from the picture below this is a 2 storey frame with 6DOF's (2 translational DOF's = u1 and u2, 4 rotational DOF's = u3, u4, u5 and u6).
i would like to determine the consistent mass matrix (6x6 and symmetric) of the frame without carrying individual calculations for each element and then superimposing them. I would like to setup the matrix by just using the relevant coefficients directly.
The procedure that i am following to setup the matrix is: a unit of acceleration is applied at each DOF successively while the other DOF are kept at zero and then determine the inertia forces that are generated at all other DOF so to keep the system in equilibrium. For example, the mass influence coefficient m12 is the external force generated at DOF 1 due to a unit acceleration at DOF 2.
mc is the mass per unit length of the column
h is the height of the column
mb is the mass per unit length of the beam
l is the length of the beam
The Attempt at a Solution
As you can see below i have already started putting the matrix together but there are certain coefficients for which i am not sure about and i would like your help if anyone has come upon this before.
The coefficients and equations that i am using within the matrix i have found them in both the Chopra and Clough Dynamics of Structures books.
Highlighted in yellow are the two coefficients for which i am not sure about, the other ones i am mostly sure they are correct
I am having a really hard time figuring out the coefficients for the 1st row and 1st column which are supposed to be the same since the matrix is symmetric. I would really appreciate it if you could at least help me complete the first column.
The first column of the matrix is determined by assuming a unit acceleration at DOF u1 as shown in the picture below and then determining the coefficients for all other DOF
Last edited: