Please, transform last expression by removing simplify:

I1 := int((diff(W, x))^2, x = 0 .. L);
U := u1+u2-(1/2)*E*b*h^3*evalf(Pi^2)*N*(I1)/(12*L^2);

In such a case, calculation takes a few seconds.

Correction.mw

Please, type "k" in

for K to 7 do .......

in lieu of "K"

I suppose that Maple essentially lacks Case command, similar to Basic.

Something like the following:

Select Case Cond

Case Cond1

{Code}

Case Cond2

{Code}

......

Case Else

{Code}

End Select

Obviously, one can use if/elif commands, but Case is more clear.

Very simple.

You should write out a vector fiield as two-component vector and use embedded Maple function.

Say, if vector field is (x^2, y^2), we get

Try this

Str:= "Hello! Bob";
Sent := StringTools[Words](Str);
[seq(StringTools[Length](Sent[i]), i=1..StringTools[WordCount](Str))];

You can implement summation on i

So a member of the series has the order of 1/j.

The initial sum diverges.

Dear friend

It's very very very simple thing:

Source: https://yadi.sk/d/SDMMy48RqEFpt

I can suggest the following aproach:

$\underline{\mathcal{G}}$

$\underline{\phantom{some text}\mathcal{G}\phantom{some text}}$

Thank you, friends. I tested the functionality of Maple and have got sure now, that cause of the error is damaged installation of Maple. It's very strange, because I haven't noticed any other issues except described above.

For example:

For example, in such a way: