What is this structure and what does it exactly mean?

Zamanı olupta bana yardım edebilecekler lütfen bana yazsın.

Yollarıma bakıpta hep boynunu bükmüşsün.

 - The first one is pretty straightforward, you can translate it as,

Those who have the time and feel they can be of help (to me) please write to me.

 - The second one is slightly more complicated. You have to understand two idioms, before you can understand it.

Idiom 1 : Yollara bakmak ... to look at one´s roads ... means waiting someone´s return with great enthusiasm

Idiom 2 : Boyun bükmek...to drop your head....dropping your head down (as opposed to keeping it up) is an expression of sadness in Turkish culture.

Putting all together your sentence would translate to,

(I hear) you constantly waited for my return and were extremely sad.

Ok, thank you, AlphaF, but what does the locative ending actually bring to the meaning? Wouldn´t it be the same if it was just olup, bakıp?

I do not have an answer to that questıon. To me, BAKIP and BAKIPTA can be interchanceably used, with no significant difference in meaning.

I think -da there is not locative. It must be seperate.

There may be a misspelling in the latter sentence, but the former with olupta I am sure about because tunci wrote it (or corrected it into this form) a couple of days ago.

In my opinion it must be seperate. I think -da is a conjuction there.

Look at how AlphaF translated it and how he/she used "and" to connect actions.

Ok, as you are so smart what do you say about this verse:

Dünyanın en tuhaf mahlukusun yani, hani şu derya içre olup deryayı bilmiyen balıktan da tuhaf. (Nazım Hikmet) 

Isn´t it strange that there is no da after olup here? Doesn´t it look like the negation in bilmiyen concerns olup also?

Dear abla ol-up is an adverb there. And there is no rule that you must use -da after -up.

Ex: Bağırıp beni rahatsız etme.