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Steel Plate Design

Steel Plate Design

Steel Plate Design

(OP)
Hi everyone I'm a fresh graduate in civil engineering and now I'm doing a steel plate design which is 400mm wide, 35mm thick and it's simply supported.The span length is .25m.It's in flexural condition. It look like elementary but I don't know how to consider the width thickness ratio of the plate.If someone knows about steel plate design plz help me thz

RE: Steel Plate Design

Is it flat?

If so, it's as easy as you think. M/S = fb

RE: Steel Plate Design

the AISC steel manual specifies how you are to determine allowable bending

RE: Steel Plate Design

If is simply supported on two ends only, manstrom has your answer. If it is simply supported on all four sides, check Roark's Formulas for Stress and Strain.

RE: Steel Plate Design

It shouldn't matter much for this particular application, but as a fresh grad I'd recommend you get used to checking serviceability as well as strength. Calculating deflection for a plate should be very straightforward if your load is uniformly distributed pressure, and that's included in the spreadsheet dik posted.

RE: Steel Plate Design

Quote (dik)

You can also use Z=bd^2/4 rather than bd^2/6 for section modulus...

If you use the Plastic Modulus, Z=bd^2/4, you would be using factored loads, right dik?

BA

RE: Steel Plate Design

aungthu,
35mm seems like a pretty thick plate to be spanning 250mm. What type of load do you have on this plate?

BA

RE: Steel Plate Design

BAretired,

No, dik is correct. The limit state is calculated independently of design method. For LRFD, the value is multiplied by 0.9; for ASD, it is divided by 1.67.

RE: Steel Plate Design

Okay, frv thank you. In Canada, ASD is not recognized, so for LRFD or LSD (Limit States Design), factored loads would be used and compared with 0.9Fy*Z, correct?

BA

RE: Steel Plate Design

Correct... BA, and although not common, WSD occasionally pops up.

Dik

RE: Steel Plate Design

BARetired, I believe the "plastification" of the cross-section has always been accounted for in AISC, albeit indirectly. I don't have the previous (ASD) codes in front of me (and I am unfamiliar with them , as I begun with the 13th (combined) Edition), but I believe there was an increase allowed in the capacity for the Yielding limit state depending on the shape of the member under consideration.. this essentially accounted for the plastic section modulus.

RE: Steel Plate Design

Now that you mention it frv, I believe a similar provision was in the Canadian code prior to the exclusive adoption of Limit States Design (LSD).

BA

RE: Steel Plate Design

In addition to the plastification of the section, the section can be considered as a Class 1 section, generally permitting a higher stress level.

RE: Steel Plate Design

I'm still wondering what type of load would require a 35 mm steel plate spanning 250 mm.

BA

RE: Steel Plate Design

Big <G>

RE: Steel Plate Design

(OP)
Thank you all the plate is used for pretension work to grip the strands at both ends (stressing end and dead end)of the form work.There are fives holes in the plate to hold five strands with wedges. The prestressed force in each strand is 144 kN.Ive checked shear, deflection, flexural. Among them, flexural is control.I used plastic modulus Z.I just wanted to know what else I still need to check.

RE: Steel Plate Design

You ask... “I just wanted to know what else I still need to check.”

One of the things you oughta check..., is to check back in here when you post a question, quickly and regularly, so there aren’t 16 guesses before you actually define your problem for the first time. And, drop the twitter speak/twitter spell and use regular engineering speak, full words and sentences. There are plenty of smart people here willing to help you with your problem, but you are wasting their time when you don’t make the effort to fully define your problem, so they know all the facts.

RE: Steel Plate Design

I think you need to check flexural again. A 35mm plate does not work for the loads given.

BA

RE: Steel Plate Design

Normally for these type of applications higher grade steel is used like 800mpa, is this the case with your project

http://www.nceng.com.au/
"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

RE: Steel Plate Design

That may be correct rowingengineer. It would be nice if the OP would clear the matter up for us. He asks a question, then abandons the thread leaving us all wondering.

Why would it be normal to use 800MPa for this application rather than a thicker plate of a more commonly available grade of steel?

BA

RE: Steel Plate Design

Because the anchor's wedge plate is relatively thick and stiff, the anchor's load to a simply-supported bearing plate is not really a distributed load. The stiffness of the wedge plate causes the anchor load to be applied to the bearing plate closer to the ends of the plate's span. This reduces the plate bending. I would expect a bearing plate for a 5-strand tieback anchor, spanning 250mm to be about 60 - 75 mm thick with Fy = 36 to 50 ksi. The larger the diameter of the wedge plate, the less load is applied to the middle of the bearing plate. The attached picture is from a recent tieback anchor project. The bearing plates spanned approximately 1'-5". The tieback design loads were generally in the 200 to 400 kip range. The steel for the bearing plates had Fy = 50 ksi. The plate thickness for a 5-strand, 176 kip DL anchor was 2.75 inches. If you ask the tendon supplier, they will often give you the plate design for the particular anchor design load and span.

www.PeirceEngineering.com

RE: Steel Plate Design

From the description given by the OP, I assumed there were five strands equally spaced along the 400mm length, presumably at 100mm oc and centered on the 250mm span. On that basis, it seemed reasonable to take the moment as PL/4 where P is 144*5 = 720kN and M = 45kN-m. If that is not correct, my earlier comment is not valid.

BA

RE: Steel Plate Design

we found that if the plate strength was well below the equipment strength, reuse of the plates is limited, thus we increased the strength. possibly a fagtiue issue as well, but mostly reuse condition.

http://www.nceng.com.au/
"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

RE: Steel Plate Design

(OP)
I used 460 MPa.I tried as PEinc said with M=PL/4.I got the thickness around 70mm

.I also find out in practice they use that much thickness.Thank you all for your answers.It help me a lot.

RE: Steel Plate Design

?

BA

RE: Steel Plate Design

(OP)
Sorry I tried like BAretied said.Should I assume them as impact loads?

RE: Steel Plate Design

They are not impact loads. Stress is applied gradually. I don't know how you came up with 70mm using Fy = 460 MPa. I believe I came up with 50mm using 300 MPa but I may be misinterpreting the problem.

Why don't you provide a sketch and your calculation?

BA

RE: Steel Plate Design

for a plate that small and supported on 4 sides, I wouldn't likely use PL/4, unless for a quick check... also, if I had a plate of a given thickness and was trying to use it, I'd look at the load distribution on the plate... unless a hard wheeled load, it may be that a UDL is applicable.

Dik

RE: Steel Plate Design

(OP)
I got 70 mm because I used impact factor for safety.its supported on two sides only dik.I realized that allowable strength is a lot more than require but I went to a precast site.In practice they use 75 mm thickness for same plate in the conditions as mine.And I have no idea why they use that much thickness.

RE: Steel Plate Design

It is not unusual to design these bearing plates for 95% of the 270 KSI guaranteed ultimate strength (GUTS) of the tendons. Check the recommendations of the Post-Tensioning Institute (PTI).

www.PeirceEngineering.com

RE: Steel Plate Design

Not a wheel load, but PT anchors... sorry

Dik

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