Question

stiffness of each storey (13 marks) Question 4 () Compare the defimition of centre of mass vw. centre of rigidity (6 marks (b) Compare the two planes shown in Figure Q(4b) regarding their torsional potential under earthquake. All joints of frames are pin-joint. The mass distribution in the floors is uniform and the stiffness of all the braces is equal (10 marks) Figure Q(4b) (c) A plane of a four-storey building having similar storeys is shown in Figure Q(4c). The plane consists of six squares, each having 6m x 6m dimensions. The stiffness of braces is shown in the Figure Q(4c) as k, 2k and 3k. All the joints in the frames are pin-joints. Only the braces resist the lateral loads in this structure. Determine the coordinates of the centre of rigadity of storeys (9 marks)
structural analysis

Answer 1

4a)

Center of mass is location wherein a linear force, if applied, produces only linear acceleration and no angular acceleration

Center of rigidity is location wherein if a force is applied does not cause any torsion in the system.

b) (i) is better in tosrion resistance compared to (ii) because the braces are well spread out and are oriented in both direction with minimum two line of resistance in each direction. In (i) there is only one line of resistsnace in each direction and therefore isnt a good system to resist torsion