Construction of house needs different materials and hence needs study. The general guide points have been discussed by us in Material Buying Guide In General. Here we discuss buying guide for steel.
One need to do adequate research when you plan to buy steel bars. The steel bars are important for the life of the structural system. They are known as rebars in short form. They are also known as reinforcing bar or reinforcement steel.
Steel bars and cement are the most important materials used in the building. The strength of building is directly related to the strength of steel bars. We already discussed the cement buying guide in our recent content.
Xingtai Steel are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together.
There are two types of steel bars in the market.
a) Mild Steel Bars:
Mild steel bars are plain in surface and are round sections of diameter from 6 to 50 mm. They can be manufactured in long length and can be cut quickly and bend easily without damage.
Mild steel bars are available in Fe410-S (Grade 60) or Fe410-O (Grade 40).
Medium tensile steel bars are available in Fe540 (Grade 75)
High strength deformed steel bars are provided with lugs, ribs or deformation on the surface of the bar to improve the bond with the concrete. They are also twisted to improve the bond with the concrete.
Cold twisted deformed bars (Ribbed or Tor Steel Bars) are recommended as best quality steel bars for construction work.
They are available in Grade Fe415, Fe415D, Fe500, Fe500D, Fe550, Fe550D, and Fe600.
Fe indicates the specified 0.2 percent proof stress or yield stress in Newton per square millimeter.
You will have to spend a lot of time towards reviewing types, brands and its grade while buying.
Tips to Buy Steel Bars for Construction
01. Why do You Want to Buy Steel Bars?
Steel bars are needed as reinforcement in RCC structure. Concrete is the materials that is very weak in tension but strong in compression. To compensate for this imbalance of concrete, we provide steel bars in concrete to increase its tensile strength.
You therefore have to select the right type and grade of steel bars depending on your requirement or as considered in structural design/structural drawing by the structural engineer.
First you have to decide why and where do you need steel? i.e. for foundation, slab, and beam, column or for water tank and where is your area located? I.e. near the sea shore is It in corrosion prone area? You may than need CRS steel.
02. Quality and Specification of Steel Bars:
You can check the quality of steel bars by following steps
- Buy only that grade of steel, as prescribed in drawing.
- Check the identification mark on the bars from the manufacturing company. Identification mark will be marked at every running meter of the bar length.
- There should not be any rust film on bars. Always buy steel bars, which are rust free.
- Check the diameter of the bar by vernier calliper and it should be the same as specified in drawing.
a) Steel Rolling Margin:
Check the percentage of deviation (Rolling Margin) in weight of reinforcement steel.
Rolling margin is very important when you buy in tonnes, and you get paid in lengths.
Avoid using steel from those rolling mills which use 'rerolled or scrap steel' as a row material. These are likely to have higher carbon content, which are prone to high corrosion.
b) Always ask for 'chemical composition' test from the supplier. Apart from other material, the content of carbon is very important. It should not be more that 0.25 percent as it would accelerate corrosion and which will not only reduce the life of building but also will increase periodical repairing work.
c) Readymade Cut Bars:
Normally in advanced countries, people don't buy steel, but they buy 'Readymade cut bars' as per designed length and shape i.e. as per bar bending schedule.
They have to be simply placed in position. But here also you need to exercise many of the above points.
When you buy 'Readymade Cut bars', check the following
(i) Check the shape and length of each type of bar as per bar bending schedule.
(ii) Check nos and stack each bar separately.
(iii) Always check the hooks, its shape and length.
(iv) Check the quantity.
d) Certification:
Check whether the steel bars you buy bears a national certification like ASTM A706, JIS G, BS, ASTM A615, JIS G and IS 432 (Mild Steel Bar), IS (High Strength Deformed Steel Bar) etc. The certification assures you about its quality as well as the reputation of the manufacturer.
03. Study of Product Literature:
When you buy steel bars, you should read all the technical specifications which are either described in the product literature or on the manufacturer's website. We have to check whether the product specification represented by sales persons and the literature confirms or not. Try to understand and follow all the cautions of use and advice for use, etc. as per the written specifications in the literature. It is also necessary to read the terms and condition of warranty, guarantee, etc.
The company is the world’s best a706 rebar supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.
04. Finance:
You may economise and save on each and every individual item, but you should not save on steel bars. They are the definite requirement of your house and directly related to safety and stability of your house.
It is advisable to provide steel bars as specified in drawing or as instructed by the structural consultant. Some people avoid consulting the structural consultant and providing the steel as per thumb rule to save the fees of the structural consultant. They forgot that every structure has carried different behaviour and one cannot use the same thumb rule for different structures. Do not get away by idiotic thumb rule of using this 2 to 3 kg of steel per Sq.ft. One thing we can tell you that thumb rules will raise your budget in future as they ultimately increase the cost of repairing work. They either excess your budget by over design or reduce the lifespan of the structure by under design.
- The Quantity You Want to Buy:
You should also estimate the exact quantity of steel diameter wise. The wastage of steel bars will cost you high. You need to work out quantity in advance so you can bargain with the supplier or distributor.
- Where is it Available, From Where to Buy Steel Bars?
You must search for the right supplier or distributor and their location. You should also find out whether it is directly available from the manufacturers or distributors or retailers etc. The price will definitely depend on from whom you buy the steel bars.
- The Cost of Transport/Taxes:
The cost of transportation, taxes and duties including the cost of loading and unloading at the site are the necessary point to remember as they also affect your budget while buying steel bars. Steel being heavy material, they form substantial weight and hence higher cost of the transportation.
05. Brand:
Always use the popular brand of steel bars as they may have a certain quality. It is advisable to use the brand suggested by your structural consultant or use the government-approved brand or ISI brand.
The Price of steel bars vary between Rs 30 to Rs 60 per kg. Kamdhenu, Thermax, Tata Tiscon, Jindal, Essar, Vizag and Electro are the popular brands of steel bars in India who make different types of steel with different grade.
06. Buy Steel Bars after Testing:
Always try to learn how to test the materials on site as well as in laboratory in case of bulk buying.
a) Hardness Test:
- Take 1 m length from each diameter of bars belonging to different lots. Bend the bar by applying pressure at both ends with your hands.
- Observe the bend portion. It should be smooth.
- If the steel is not of good quality, it may break or develop cracks on the surface. Such steel should be rejected.
b) Weight Checking:
- Take the exactly 1-meter length of each diameter of the bars on the random basis.
- Weigh each sample on a weighting scale.
- Compare the weight with the theoretical weights given in codes and assume rolling margin.
- The difference in weight which is called rolling margin should not be more than 5%.
07. Selection of Material and Supplier to Buy Steel Bar:
Study the above factors of steel bars and then select the right material and the supplier.
It is advisable to place written order if you are buying the large quantity. It should include specifications of steel bars, rates including taxes, transportation, and loading-unloading charges, etc. It should also include quantity, time of delivery, warranty, guarantee, terms of payment including advance.
When you receive steel bars at the site, please check the make, quantity and quality. Also check ISI marks, brand and whether there are any damages to the steel bars.
Also check the weight of steel bar received on site by at approved weighbridge.
Use this formula for the actual weight of steel (site) = Total weight of truck with steel bars ' The empty weight of truck (Weight without steel).
Do not stack directly on the ground as the ground moisture will rust it. Store the steel bars in godown and place wooden batten below them so they should not directly rest on ground.
If you are satisfied with the quality and quantity of the steel bars, then make payment as per the contract and obtain the receipt of payment. Preserve all the bills, product literature and the warrant/guarantee certificate, etc.
08. Life of Material:
The steel bars are generally one-time purchase, and it has a long lasting service life when embedded in concrete. If we leave them in open environment, they get corroded fast. Hence try to use them as early as possible or store steel bars in warehouse.
You can buy steel bars in 8 mm (18 nos per bundle), 10 mm (12 nos per bundle), 12 mm (8 nos per bundle), and 16 mm (5 nos per bundle) sizes. They are commonly used for house construction. You can also buy steel bars with the bigger diameter of 20 mm (3 nos per bundle), 25 mm, 28 mm, and 32 mm, which are used for high-rise buildings only. They are generally packed in the bundle, and above 20 mm diameter, they are available in the single piece.
The standard length of steel bars is 12 meter, but you can select the length as per your requirement.
Nowadays Thermo Mechanically Treated (TMT) steel and Corrosion Resistance Steel (CRS) are also used in Reinforced Concrete Framed Structure construction. They have good elongation, bending strength, ductility and high tensile strength and high corrosion resistance.
Contact us to discuss your requirements of astm a615 rebar. Our experienced sales team can help you identify the options that best suit your needs.
Conclusion:
- Buy the popular brand of right type and grade of steel bars from the right supplier as per your need.
- Place the written order. Written order should include specification, the quantity, type, grade, time of delivery and terms of payment, etc.
- Once you are satisfied with quality and quantity as per your requirement, make the payment and obtain the receipt of payment. Preserve the entire purchasing document as you may need them in future.
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I am not entirely convinced by PXC suggestion is necessary. Sure it seems to be a more positive anchorage to weld a bar to pre-drilled holes but the strength essentially comes from the weld. A long fillet weld, mostly on both sides of one leg of a "L" shape rebar should have more weld than that around the circumference of a couple of holes. One leg of the "L" in this case could be fully welded to the steel member. The weld should be strong enough allow the bar fail first before any unzipping or any detackment from the host steel member.
Rebar is difficult to weld and the heat process of the welding process can degrade the load carrying capacity of the steel. The former can be overcome by experienced and certified welders and selection of a suitable weldable grade for the rebar. The latter can be offset by increasing the development length, say in the worst case the high yield degrades to mild steel. There is no technical reason why SRO's proposal should not work in practice, as some posts here already substantiated.
I have doubt on the end-on butt weld application capable of developing the full tensile strength of the rebar. I am aware of the stub type connection is good for shear and widely used in composite construction. It doesn't sound right here if the bar's primary function is to resist moment with axial tension.
Can an end-on butt weld by a stub gun, which I presume the weld is formed by impact and electrical current, be pulled out by failing only in the rebar body and not the weld?
Hi all,
I'm a little surprised no one has mentioned the governing welding code here, AWS D1.4.
It has sections on allowable stresses, allowable reinforcing steel and allowable filler metals. For the flare-bevel joint described above, the Code will only allow stresses of 30% of the nominal tensile strength of the filler metal, similar to a fillet weld in LRFD structural welds. Effective weld sizes must be determined per Code similar to flare bevel grooves joining sections onto pipe or tube steel.
I'm not sure of the design, but the reinforcing steel is 60 ksi YS and the structural shape is 50 ksi YS. Moment frame connection are typically complete penetration welds to develop the full strength of the materials. Code requires (I assume A706 "weldable" rebar) 70 ksi filler metal to match the lower strength structural steel. The Code makes no distinction between A706 and several other reinforcing steels available. They are all "weldable" when following a proven welding procedure in conformance with the Code. My tests have shown tensile strength to be at least 125% of yield strength is easily attained for welded A706 and A615 gr 60. But it is your money.
Remembering the structural steel and E70 class electrode, automatic stud welding of DBA's would accomplish the same thing. They, too, are complete penetration welds. Preproduction bend tests proof load these welds by bending a sample of the fabricator's daily run to 30 degrees out of normal. That's a pretty good indicator of weld soundness. These welds are governed by AWS D1.1. Buy that Code, too.
And under a moment load, won't your concrete crack out around the bar before the weld or even the reinforcing steel yields? I don't think development length governs here. We're not just pulling the rod out of the concrete. Just a thought.
The hold back of two rod diameters from the tangent of the cold bend is correct.
Running the PQR is mandatory to prove the fabricator's welding process. I don't recommend running procedures for every job though. Some jurisdictions require recent tests. My thoughts are once the appropriate PQR has been run, it validates the supplier's methods. Nobody cheats a weld test. You have to audit the supplier to verify continued compliance with the qualified welding procedure.
And don't let your fabricator use some other fabricator's welding procedures! It's your money and your fabricator's should be sophisticated enough to understand the control of their welding program. If they aren't, run them out of business. There has to be at least a modicum of honor among us thieves.
Fun!
Koz
Speaking from the projects I have involved (all outside USA) the standard site practice is to disallow welding of rebar on site unless the situation is unavoidable. Welding in a fabricator yard is a totally different story because the work will be properly prepared, executed and experienced and qualified welders are available.
Unless SRO's design is prepared and included in the design of the structural shapes allowing the fabricator to implement the welded bars before the delivery of the structural steelwork, the other alternative would be to put the detail of the welded rebar on the reinforcement drawing leaving the contractor to carry out the welding on site.
May be SRO should make it clear which route he is likely to embark on. It is just not a standard practice to ask a steel fabricator to weld steel reinforcing bars routinely on structural shapes even though there is no technical reason not to and I am sure many such cases have been done in the past.
I seldom deal with structural shapes and welding myself and wish to understand a bit more from Koz's comment.
Would I be correct in thinking as the code allows only 30% of tensile strength from the filler material in the welding with a rebar this effectively requires a designer to specify an equivalent of 330% of rebar cross sectional area for the weld. Also the end result is that the full capacity of the rebar can be utilized in the design without any loss in the welding process, presumably obtainable from any site application as long as the proper procedure is followed and experienced and qualified welder is used (I am leaving out the problem of achieving the right facilities on site as a separate problem).
I am not sure why development length is irrelevant here. One leg of "L" bar is anchored to the structural shape and Koz's remark convinces me that the anchorage can be achieved by designing to AWS D1.4. The remaining leg is cast into the concrete column and surely the moment in the interconnected steel shapes cannot be transferred into the concrete column without the embedded rebar able to develop it full strength. Concrete cracks out around bars only in compression and the reinforcement problem here is mainly tensile (Because if needed we always can put rebar in the compression zone with the amount equal to the tension zone to beef up the combined compressive resistance with concrete to avoid a compressive failure).
Finally there is a potential gap to be bridged in our understanding of joining steel structural shapes with reinforced concrete. This is because, unlike steel which behaves homogeneously in both tension and compression, concrete is an inhomogeneous material not permitted to have strength in tension (or its small tensile resistance is ignored) in the design. Thus under a loaded condition the tension side of the neutral axis has no concrete but in the analysis of the structure it is acceptable to use only the full concrete section for resisting moment and all reinforcement is ignored. In other word in the frame analysis we always use the second moment of area of a RC beam not corresponding to its service condition. Hence there is an error in the analysis. Although many codes also allow cracked sections to be used but this is rarely done in practice because the uncracked (full) section approach works well as long as every member of the structure is reinforced concrete. We all know moment distribution is based on the relative and not the actual stiffness.
However if we marry up structural shapes to reinforced concrete beams and columns the established method of design may need to be revised, like using the actual stiffness of the cracked section of the reinforced concrete may be necessary.
I would welcome any comment from other engineers to my last point.
Hi all
To Bbird's question regarding weld area.
I think your numbers are right. AWS D1.1 and AISC LRFD set the same limits noted in my post for fillet welds of structural to structural. You're have to have fillet welds long enough to resist the allowable load whether they're 3/16" or 3/4". And then you can only use 30% of the filler metal UTS. This is standard practice. Anyone who designs a ledger angle runs into this same consideration. It gets slightly more complicated for a flare-bevel groove since you have to consider the "effective" throat of the weld. Look at your AWS D1.4 for accurate information.
The loss of strength because of welding that you speak of is already considered in the 30% reductions and the load resistance factors of ACI. And the weld is stronger than the reinforcing steel. Sound direct butt joints always fail in the reinforcing steel with large amounts of necking of the bar observed. The structural steel has the least strength of the joint and it is your limiting factor.
Regarding the welding of the reinforcing steel, the steel doesn't care where it is welded. Shop or field, daytime or nighttime, California or Katmandu (base material quality aside and don't weld when it is less than 0 deg F or in the rain, etc and read the Code) it doesn't matter. Follow Code parameters and the weld joint will pass the required mechanical tests. Done deal. If someone can show me why the steel is sensitive to the geographical location of assembly please enlighten me. Otherwise, this is just noise.
Code parameters include proper preheat, proper cleanliness, proper joint preparation. These parameters are generally performed by non-welders or overseen by supervisory personnel that have no understanding of welding Codes or requirements, so they cut corners when no one is looking. The mundane aspects of setting the proper power source settings and having the skills to manipulate the torch properly, all controlled by the skilled welder, are only part of getting a good weld. If the welds are failing, it is because someone is cheating. It is not due to the welding processes or the base materials.
Of course your comments regarding the tension side versus compression side of reinforced concrete are correct. The reinforcing steel takes the tension. And designs frequently consider the resistance of the section using the cracked moment of inertia.
But a seismic or ballistic event is not simple tension nor compression. It is acceleration more like waves. So that hard reinforcing steel bashes around in the concrete. Eventually you just have a steel rod sitting in a dust filled hole. That's what I think, anyway.
What do you think?
Koz
Hi all,
Once again we are talking practice, not material or process. I have read the referenced thread and it is built upon the same confusion. While there is some good technical welding data there, it is also surrounded in anecdote and prejudice concerning the capabilities of today's erectors and fabricators.
There is a lack of welding training in our country. I judge by the CWIC appelation that you have passed the AWS certified welding inspector examination. Did you find any questions on that exam concerning the inspection of reinforcing steel? That is because reinforcing steel is relatively easy to weld and we figure everyone will read the Code and do the job right. It's not like a moment frame, afterall. And rebar gets buried in concrete. Who's going to know? Our industry continually overlooks the control necessary to do a good job. And with the carbon equivalents as high as we find in reinforcing steel, training and verification are critical.
These are not, however, material or weldability issues. These are training and implementation issues. Reinforcing steel is very weldable. If you trust a welder to weld up a seismic resistant moment frame or power piping or an ammonia containing pressure vessel, you can trust the welder to join reinforcing steel if they are aware of the requirements and necessary techniques. Many of these same folks also carry certs for D1.4.
If I have a Bechtel or a Fluor running a job in Katmandu, I know the expertise is there to do the job right regardless of product form or chemical analysis. If Ma and Pa Kettle Welders-R-Us is doing a job in San Bernadino County, I think I would impose continuous inspection, as IBC permits, because I can almost guarantee they will botch it. But they would botch handrail, too. Pride of Craftsmanship doesn't recognize geopgraphical location, either.
To fix a problem, we have to define the problem. The problem is not the material or welding process, regardless of where that operation is being performed. The problem is in the flow-down of knowledge. This will only get worse as we continue to go off-shore for our welders and demonize what little welding training is left in our country. I expect our engineers to demand excellence and enforce it. Ma and Pa Kettle cannot be permitted to set the quality standards of our designs because we choose to save a nickel on inspection. Get those bums off the job and hire properly trained welders. Welding inspectors can help by pulling the certs of shoddy welder's, too. Inspectors are permitted, even expected, to require welder requalification if a specific reason can be found as permitted by AWS Code.
Let's not confuse the issue by spinning personal war-stories about shoddy workmanship. The data is anecdotal and not scientific. There are still plenty of good welders and contractors out there. Reinforcing steel is readily welded, using common welding processes, and common welding techniques. Implement the Code, that's all. Upgrade our industry, don't degrade it.
Koz
Well, I'll try one more time to clarify some of my replies and by others.
Repeat from the original thread noted by SRO:
"I would not reject the idea of rebar welding as it is commonly performed (at least here in So Cal) daily with satisfactory results."
"I respectfully disagree that welding of reinforcing steel is not recommended."
In my first reply to SRO above, I also note welding of rebar is quite common.
I feel more is being interpreted regarding the replies than what is clearly stated. I am encouraging the welding process for joining the rebar to the carbon or high strength steel originaly noted by SRO.
The "war stories" are documented facts noted during QA or QC inspections where the workmanship or technique performed in the past were less than adequate and not in compliance with the code. Yes [weldable] rebar can be performed satifactorily by qualified and experienced personnel, but workmanship and technique are paramount.
A few more facts:
1.) Not all jurisdictions or agencies use the UBC/IBC. Special inspection is NOT always required.
2.) NO special inspector has the authority to "pull" a welder performance qualification. Qualification or requalification of welding personnel is the contractors responsibility. QC or QA can only make the recommendation.
3.) If organizations like the ICC, SEAOSC, etc. believe these unscientific anecdotes are just that, then there are a lot of building officials and engineers [who are my clients] very confused.
4.) I am a SCWI, there are almost 30,000 CWI's, I am one of a couple of hundred Senior Welding Inspectors.
No harm no foul, just stating "what I think" which is what SRO asked way up on top.
Hi All,
Thank you for taking the time to clarify your responses. In light of that respect I will try to keep this one short, rather than get on the soap box,again.
I asked Bbird about the reinforcing steel cracking out its developed length during a seismic event for a moment frame. I've gotten no response. They are conducting tests at our local university on full-section models of what I'm assuming is a similar joint configuration. The concrete columns are about 18" x18", but I'm wasn't really paying attention. The rebar doesn't yield, maybe a little, but the concrete surrounding the bar turns to dust. And I think they are getting some cracking of the beam, but nothing catastrophic. They are developing wrapping these joints in carbon-reinforced sheets to ensure the performance and reliability of these connections. They're getting a patent on the wrapping process, et. al. So what do you think about this connection?
To CWIC: Since we're throwing certs on the table, I'm a SCWI, too. But I was also a 6-G welder-fitter for Chicago Bridge & Iron and journeyman'd with Ironworkers in my wild and crazy youth. And as I work to finish my ME in Civil Engineering, I find science is much more valuable than war-stories for promoting good engineering. The initial question regarded welding rebar to structural and a confusion concerning deformed bar anchors. These are easy welding problems. Codes recognise that. You made it sound difficult for ancillary problems not related to materials or process. Problems common to all operations including NDT and concrete, I will add.
I will love to continue this discussion in another thread, because I think we have gotten way off track. But I think it is a very important discussion. Our engineers are not being taught key issues in welding. Even the best California structural engineering firms are struggling with how to effectively control the welding going on in their projects. And the engineering schools are not giving these folks even the rudimentary tools to ensure quality. But all of the codes make it the sole, legal responsibility of the engineer to develop quality plans and approve deviations from Code. It should be our responsibility, as SCWI's, to help these folks with the best data available. So let's move our discussion to a new thread in this discussion group so we don't continue to bore the concrete guys. I'll call it "Zen and Welding" and we can devote it to the gap between Code implementation and actual practice. I'll kick it off by commenting on your "facts" there.
I'm still interested in the development length, though.
Koz