What is the difference between a girder and a stringer

For example accommodation deck plating or main deck plating. It is made of smaller sections of steel plates. These smaller sections of the plate are welded together. Irrespective of with what method these plates are joined together, these are placed in a certain pattern. Let us understand this with an example of box shaped ship. The smaller plates that we are talking about would look something like this for the box shaped ship.

In naval architecture and ship construction each of these plate has an identification. These are numbered in certain pattern. For example the plates on the side shell plating are numbered like this.

Now based on these numbering system the identification of plates for the box shaped ship would look something like this. If we want to be more specific, We can say that we have starboard A-Strake , starboard B-strake and so on.

Similar naming will be on the port side. For the bottom shell plating, similar numbering is done for the plates forming it.

For the bottom shell plating. So the plate adjacent to the keel plate will have a identification of A1, A2 and so on starting with A1 from the after most plate. Now there are three type of strakes that you would hear in ship construction. Let us see what these are. Shear strake is the top most strake of the Side shell plating. So if side shell plating has strakes from A to K, then K-strake is the shear strake. This is the strake that connects with the deck plating.

Can you identify the shear strake in the box shape ship example that i gave above? Yes, you got it right. I-Strake is the shear strake in this case. Shear strake is usually of higher thickness and strength than other strakes. This is because this strake can have lot of physical damages during the life of ship.

I earlier said that keel is a plate that is back bone of the ship. But keel plate is also made up of smaller sections of the steel plates.

These strake of plates that form the keel of the ship is called Keel Strake. Garboard strake is the first strake on each side of the keel strake. As we discussed in the bottom strakes, the first stake from the keel is named A-strake.

Now for the box shape ship, the naming of strakes might look simple but for actual ship with curved sides and flared bottom, it might not be that simple. Next time you get your hands on a shell expansion plan of your ship, try to read it to identify shear strake, keel strake and garboard strake.

A steel plate of 2mm thickness can be easily bent. If you lift this plate with the crane from its ends, it will most likely bend at the center. Now what can you do to avoid it from bending? One easy solution is to increase the thickness of the plate by welding two or more plates together. But in ship construction this is not a good idea. One among many reasons for this is that we do not want to increase the light weight of the ship. The better option is to weld two of more flat bars either in fore and aft direction or athwartship direction.

In this case these flat bars will be called stiffners. Anything that is used solely to provide strength to a ship structure can be called a stiffner. Longitudinal stiffners and transverse stiffners can further will named according to various factors including the amount of strength these provide to the structure. Girders are also named according to its location. The girder at the center of the ship is called center girder.

In double bottom tanks, the thick solid metal plate that divides the ballast tanks into port and starboard tank is the center girder. Apart from the center girder, there can be few girders on each side of the ship or double bottom. While center girder runs in full depth of the double bottom tank, side girders may or may not run in full depth.

In most cases the longitudinals are beams mostly L-beams and runs along the length of the ship. Double bottom space is the most common space where you can easliy identify longitudinals. Longitudinals are further named depending upon what section these longitudinals are strengthening.

If you have been to a double bottom tank, these longitudinals are difficult to miss. The bottom longitudinals are the one we sometime step on to avoid stepping in the left over water or mud of the ballast tank. I am sure you can locate the longitudinals in above picture that I shared.

If you cannot, I share it again with marking of longitudinals. We can consider the frames to be similar to the girders but with only one difference. Frames runs in transverse Athwartship direction. These are different from frames in two ways. First unlike frames these do not extend to full height of the compartment. Second transverse are of lesser strength and thickness than frames. In the above photo, notice how the girder is stiffned.

The stiffner is welded in vertical direction. If same stiffner is required to be welded in horizontal direction, it will be called stringer. One of the location where stringer is mostly used is the forward part of the ship. Bow of the ship has to bear lots of stress and so requires extra strengthening. I will limit myself with discussion of bow construction just to understand stringers. I will cover bow construction in detail some other day.

So among many other strengthening members, panting beams are used in this area to counter these stresses. But even these beams need to be stiffened at the point where these connects with the side frame. Panting stringers does this job.

As I said stringers are horizontal stiffeners parallel to the water line. Ship construction is something that requires a lot of imagination to understand.

But even if someone has a strong imagination bone in the body, knowledge of ship construction will still be difficult without knowing basic terms used in it. These 10 terms are the basic of ship constructions and once we know these, ship construction will be a little easier task. Rajeev Jassal has sailed for over 19 years mainly on crude oil, product and chemical tankers. He has done extensive research on quantitatively measuring Safety culture onboard and safety climate ashore which he believes is the most important element for safer shipping.

Sir i have recently completed my JET for 6 months. Now preparing for class4. This information you gave is not new to me. But the way you explained things was awesome. I am definitely not going to forget this. Looking forward for same great stuff.

Very good article Also try this one on the web.. It's about hull structure, It's very good First of all l take this oppertunity to appreciate you, for your efffort taken to post this very usefull Blog. This blog is very usefull to everyone in shipping field.. Sir,first of all i would like to thank you for the blogs,these are so simply written so that everyone can understand,quite helpful also to understand the basics. If you can write something about MS Act ,it can be more helpful.

Thanks Soumen. Sure I will consider writing on MS act. Meanwhile if you have any particular question, you can ask on our new section "Questions". I have been going through your blog from quite sometime now. They are really helpful! Thank you :. Ur explanation is very helpful with supportive pictures. Even as a senior ranked engineer I felt ur article was much helpful. Thank u. Sir, really thankful to you making such a clear and good explanation of ships construction, it was well labeled and very simple words used in explanation, and the image ugh too good.

Hello Sir , Was going through the page and was confused about the part " identification of plates for the box shaped ship would look something like this" if i am not mistaken you were trying to explain about the shell expansion plan in here right. Wanted to know if thickness of side shell platings will be mentioned in the Shell Expansion plan.

Yes, Thickness is mentioned in shell expansion plan. I will cover this topic in one of my future blogs. Due to this now i have understood most of the things.. Very nicely explained Ship construction is really tough topic for us Very helpful thank you so much sir for these information helped me in preparation for the 2nd mate orals. Good day, Mr Rajeev am very greatful for your articles, it really improve me a little, because am preparing for my oow examination in Nigeria maritime academy.

Thank you for your good explanation of those basic ship construction terms. I have some questions to ask sir. What are the structural members of the ship that counters yawning. I am really impressed.. Dear Sir, It's lot easier to learn Ship Const. Thank You soo much sir, for the easy and beautiful explanation. Preparing for Chief Mates oral exam and all your articles are really very helpful.

Thanks a lot Sir. Captain, this was a really good lesson in understanding the basics first of ship construction. I'm going aboard soon as deck cadet and this will surely help me in my pre sea course. Sir the way you explain i love it. The best thing of your blog is that ,i love most ,after reading there is no question arise that i need explaination.

Welldone sir, well ellaborated.. Am an MSc Student of Middlesex University UK and presently we've just concluded the course 'Ship designs and Systems', your simple explanations and pictoral illustrations really helped in differentiating the structural members and their functions from each other.. Thanks once more, more grease to your elbow. Beautiful article sir with super self-explanatory image.

The outer plating of the structure is riveted, welded, or cemented to stringers connected to such transverse members as ribs and beams.

Stringer beams: These are secondary beams typically used in truss bridges to carry the load from the slab till the cross beams located at truss nodes. The main difference between a girder and a beam is the size of the component. In general, workers in the construction industry refer to large beams as girders. If it is the chief horizontal support in a structure, it is a girder , not a beam. If it is one of the smaller structural supports, it is a beam.

As nouns the difference between stringer and beam. What is the stringer? In journalism, a stringer is a freelance journalist, photographer, or videographer who contributes reports, photos, or videos to a news organization on an ongoing basis but is paid individually for each piece of published or broadcast work.

The term is typically confined to news industry jargon. What is spandrel beam? In concrete or steel construction, an exterior beam extending from column to column usually carrying an exterior wall load is known as a spandrel beam. The spandrels over doorways in perpendicular work are generally richly decorated. At Magdalen College, Oxford, is one which is perforated.

What is girder beam? It is the main horizontal support of a structure which supports smaller beams. Girders often have an I-beam cross section composed of two load-bearing flanges separated by a stabilizing web, but may also have a box shape, Z shape, or other forms. What is a stringer plate? Definition of stringer plate. What is stringer beam in staircase? In case of RCC stairs, steps are constructed over stair slab that has width up to full length of steps. Please observe the bridge section attached.

In technical report would you use the term girders or stringers for the members spanning between bent caps? In that configuration, either term would be appropriate. My understanding of the applicable terminology follows KootK's. If there is only one predominant beam in the structure before you get to the vertical gravity supports then I just default to the term "girders".

I suppose you could make an argument that the bent cap is the "girder" and the primary bridge beams are "stringers", but I would disagree with this. While we're talking about bridge terms, can I go on record to say that the term "bent" has always sounded like a misnomer to me.

There's nothing "bent" about them yes, I know the etymology is probably from historic usage or non-English languages. Maybe it's just me but I've always tried to refer to bridge supports are "piers" rather than "bents". I would use the term beam for cross members between the stringers. I would use the term "Bent Cap Beam"; and agree with you that the bent cap should not be labeled a girder.

I've heard of the vertical bents being referred to as piers also. It appears this bridge could be labeled as having either girders or stringers. The member size is W36x and there are six 6 of them. Lomarandil makes a good point; if I see a member which is too small to be a typical size for a "girder" I would probably not call it such unless it had other members framing into it and truly was a "girder". All said, I think you could call it a girder or a stringer and the intent would be clear, as long as you were consistent.

A floorbeam - can be rolled or fabricated - is perpendicular to a girder and supports stringers. W36 would be a stringer; beams between stringers or girders are diaphragms. For W36 these days, I agree with Lomarandil. Whether the beams are called "stringers" or "girders" has more to do with the general size of the members. Consistent with bridgebuster's comments, the difference was more significant in the early 20th century when large beams were not rolled by steel mills.

Anything larger was a riveted "girder". A bridge "bent" usually has been used to refer to one "line" of supports for the superstructure. This could be one large pier, perhaps two, three, or more smaller piers that share a common foundation, or a row of piling, as in a "pile bent".