Lately I began to wonder why I hadn't learned how to calculate the beam shear stiffness in college. I vaguely recalled that the teacher told us the shear stiffness could be omitted in the beam calculation compared to the bending stiffness.

Can anybody show me how to calculate the shear stiffness if it is large enough and cannot be ignored?  Like the example shown in the picture below

Recently, I indulged myself into the progressive damage simulation of composite materials. I firstly used the USDFLS to create several fields to define certain kinds of damage, such as fiber crack, matrix crack, shear damage and delamination. One curious thing that I experienced into this is that ABAQUS/Standard informed me that "Stiffness defined by engineering constants is not physically reasonable. Check choice of poisson's ratios". I checked the data and changed some to comply with the rules of the transversely isotropic materials and the program proceeded. 

Greetings, 

Recently I have been indulging into loads of papers on "Progressive Damage Methodology".

I wondered based on what theory did the "Progressive Damage Methodology" intrigue so many researchers to unfold various kind of experiment and simulation, in other words, why do people have to study on this methodology?

Also, I was curious on the difference between "Cumulative Damage" and "Progressive Damage".

Can anyone here possibly give me some advice on the two questions?

 Faithfully,

James