and this is [one of] my initial design:

thank you sir i had no idea about the beam, so other than the roof the stuff in the base are ok then?will i be needing a foundation of any sort?since i'm building this on the roof and i can't use concrete,will that frame in the base suffice?

i was doing another design i made the roof angle 90 degrees to make the work easier and changed the posts (and studs) a little bit

(this was before reading your post so i haven't fixed the post problem yet)

what do you think about this?i did it so i could screw the left rafter first and then the right one, is it ok?

i was thinking about using thick glass(10mm or 3/8") or twin wall polycarbonate for south side and cover the rest of the walls and roof with boards, if i did that would there be enough light?
and would side walls make shadow?is it a good idea?
i mean like this one

The beam detail on the 2nd diagram from the top, is a better design, but still needs end posts. Again, it will depend on the span and the loads, but you will likely need one or more 2x wood members for the beam, and they should be oriented vertically, with vertical posts supporting the ends (and maybe some in the middle too). Turning the beam will weaken it. And lap joints are nice but not necessary; for added strength you can use joist hangers.

There are other details too which should be put into your drawings, such as where the door is going to go, and the supports for it. Depending upon the height of the walls, you may not have too many choices on that. Same for vents and windows.

You will need some sort of foundation, even if just some treated 4x4's placed on leveled, compacted soil. Again, this is something which will vary depending upon your situation and locale. Does your ground freeze during the winter? What type of soil do you have, is it expansive? and things like this. If you plan to use glass, it will be VERY, VERY important that you have a stable foundation and strong enough framing to prevent movement. Glass does not have much leeway in bending if your structure shifts due to loads or the foundation.

There are also details such as the strength of the covering material (glass or polycarb), what spacing they need for the loads you are designing for, and what attachment system you are using. And it can be VERY DANGEROUS (even deadly) to use plain glass in a greenhouse, and it is against most building codes. A hail storm or other things cans cause the glass in the roof to break and rain down as sharp glass slivers. You need to use the proper glass for a GH.

You might want to ask a builder or an engineer to lend you a hand. There are quite a few details which need to be taken into account in building any structure. I would not want to send a novice off to start building without someone familiar with the process taking a look at their design, and confirming that it is adequate for the conditions where it is being built.

There are also sites which sell polycarbonate GH materials that have a lot of information about designing a GH with their products. They won't answer all your questions (such as locale loads and soil conditions), but should be a good start...

thanks, wood structures are not common in my country (almost non existent!) so i can't ask for local help :(
i'll fix the beam problem.
i was thinking about putting glass or polycarbonate inside these grooves and nail some woods over it to keep it place:
if i use glass i'll use tempered glass(i think it's safe)
what's your opinion about covering the sides like the third photo?would it cause a problem for lighting?

I did not realize that finding expertise with wood construction techniques was hard to do for you. Perhaps if you can take a look at a building or bridge with say a steel beam, you can get the idea. Those steel beams have their "tall" dimension vertically, since that is the way they are strongest, and it makes best use of their material strength. Even if what they are supporting is at an angle the beam is put in perfectly vertically, and angled spacers are used to fit the angled parts. For wood construction this might translate to a beam of say a 2x10 (or two of them nailed together), placed with the 10" dimension vertically. The rafters for the roof would be cut at an angle where they attach to this beam (a vertical cut) and either nailed to the beam or put into a joist hanger.

As far as attaching the glass or polycarbonate, you have several choices. There are aluminum extruded systems for both types which screw to the wood and clamp the glass/poly with rubber seals. These systems give a very finished look like for a house or commercial building. However for polycarbonate for commercial GHs, it is usually attached via screws with special washers that have a rubber coating on one side (specially made for poly, so that the synthetic rubber does not degrade the poly over time). Special channels are made for joining the butt ends. And some special tapes are made to seal the top and bottom. Take a look at http://www.sundancesupply.com/ they are one of the sites which sell multi-wall polycarb and have some good info on installing it on their site. Also take a look at http://www.palramamericas.com/Products/Flat-Sheets/thermaglas-line/THERMAGLAS/ they are a manufacture of multi-wall polycarbonate and that page has several downloads of their instructions for using their products. BTW, the pic of a GH with the covered sides appears to have its plastic installed on the outside of its frame, as an example.

You can put polycarb in a frame like glass, however it does expand more than glass does, so having the correct gap around the edges will be important to prevent buckling in the heat. It is important for glass too, just less so, although the glass can crack if you get it too tight.

Also, if you are going to install glass or poly in a wood frame, it is typically done such that the glass/poly goes in from the outside, at least on angled/roof surfaces. This way gravity will hold the pane in place even without the wood strips, and if it falls out, it falls to the outside not inside on people. It will make it more secure (in case those wood strips ever get loose) as well as easier to install. However if you go with polycarb glazing, the outside fitting with screws and washers will be a much easier way to install the glazing. If you do choose glass, be aware there are standard sizes it comes in (at least for double pane units). Designing around standard sizes can save considerable costs and trouble.

As for whether or not solid covering the sides will shade the inside of the GH too much, that will depend upon the details of your site, and your location. It is done frequently in northern areas where there is considerable cold during the winter and only marginal light/heat gains thru the sides. In those cases having more insulation on the sides outweighs the minimal additional light glazed sides would provide. Whether that trade off makes sense for your location and site is something you will have to determine. What are your winters like, are there trees or other things blocking sunlight from some directions, what are the light requirements of what you plan to grow, etc?

In the US, tempered glass is OK for vertical walls, but tempered-laminated glass (like auto windsheilds are made from) is what is building code for roof glazing. You may or may not have building codes to follow, but that is what is required here. Tempered will certainly be better in a roof; at least it wan't break into sharp pieces.

The glazing angle is designed for maximum solar gain
during the winter months, assuming you are located in the northern hemisphere
in the middle latitudes. Longer structures (ridge length) of this design will
experience a smaller percentage shading effect from the east and west walls. A
suggestion would be that you glaze at least the southern half of the east and
west walls because of the shorter length of this greenhouse.