The steel structure project is the easiest work to do. You know why? It will just start with anchor bolt installation, checking the distances of the anchor bolts and the critical distance. Ensuring the locations and level by providing survey report. Erecting the steel members start from column bracing, rafters, purlins, beam, joist etc. A tremendously easy and can be erected quickly.
Steel structure work is really different from concrete structure, concrete works are more complex, especially when the project is a high-rise concrete structure. Therefore, the foundation will be huge enough to carry all the load transferred from superstructure then follows the complexity of the construction of foundation towards superstructure.
In concrete structure, steel reinforcement holds the concrete elements that make it stand and firm, but in steel structure, it’s either the rivets or bolts that held it stand. So, I am going to write the most common method of checking the tightness of connection bolts in most practical and easiest way.
Actually, there are five methods of checking the tightness of connection bolts. There is “Direct Tension Indicator” or DTI. The direct tension indicator is usually written in the specification and one of the requirements to check the bolt for tightness. There is that called “Turn-of-Nut” method which is also easy to use but hugely tedious. Imagine that if you have 3,000 bolts in one “truss or floor beams” it is not practical. The other methods, we will discuss it later.
Now, in our projects we’ve used the most extremely simple and easy ways to checking the connection bolts tightness and you should be doing this in your project.
This is what we called “Calibrated Wrench Pre-tensioning.”
Here is the guide to check the connection bolts using calibrated wrench pre-tensioning or torque wrench.
1. Calibration Certificate
Maintain the calibration certificate of the torque wrench. If you have subcontractor require them to submit the calibration certificate and keep it in a file. Log it in your equipment calibration log to trace the date of expiration or validity of calibration. Make sure it is up to date.
2. Impact the bolts via impact machine
Before checking the bolts with torque, the bolts should have been tightened to snug-tight condition via impact machine. Make sure that all the bolts have been impacted.
Impacting to snug-tight condition
Snug-tight condition is defined as the tightness attained with a few impacts of an impact wrench or the full effort of an ironworker with an ordinary spud wrench to bring the connected plies into firm contact
3. Determine the torque value of bolts
There are standards that specify the torque values of the bolts like German Standard, British Standard, and American Standard. Some use the German Standard, but in our current project we are using American Standard which is ASTM A325 and ASTM A390. It is important to determine first the tightening torque requirement of bolt before checking the bolts with a torque wrench.
4. Bolt tightening inspection
Bolts shall be checked by calibrated torque wrench as per recommended tightening torque in the applied project standard. There are types of torque wrenches that you can use from, one is having the digital or dial gauge and the other has clicked type torque wrench. Click type is easy to use and very convenient. You are maybe asking “How to determine if the bolt being checked has passed to the required tightening torque value?” Because of the click type torque, once the torque has reached to tightening torque value a sound “Click” will come from the torque itself.
5. System of checking a group of bolts
This photo serves as a sample of system of tightening
If you are in the connection plate consists of a group of bolts shown in the above photo. Let us have an example to just explain how the system of checking. The tightening would start either from the bottom corners of the plate, let us say you would want to start at lower left corner and then cross in the upper right corner of the plate and vice-versa.
You should take extra care when the erection of steel structure, especially high-rise steel structure, hangars with 43.0-meter columns, space steel truss for pipe racks etc. If you will not consider the importance of connection bolts, those structures may fail. Because of bolts, that is why those structures I have mentioned are still standing rigidly and firm.
Good day. Excellent read.
Noel just a question. Are you sure it is ASTM A390 and not ASTM 490?
Hi Noel,
What is the most common way of determining the tension values of HSFG bolt?
Hi Camelo,
If you are talking about tension then it would simply mean that it is a test, what you will do then is to send the sample to the approved 3rd party laboratory they have the so-called UTM machine to test the bolt in order to know the tensile strength of the bolt.
Hi sir noel, may you give expert advice regarding our project. We have a project in Guadalupe bridge, bolt tightening of all bolts on it. But, they do not have the torque value of bolts. Also, what torque wrench may you suggest using? Thanks in advance
Hi King,
Firstly, thanks for your comment.
What is the size of the bolt are your going to tighten? If it is 30mm diameter bolt the torque value will be 1,511.12 N.m (lubricated bolt). The best for bigger diameter bolt, you can use a torque machine called “multiplier.”
Welcome. Keep on commenting….
Thank you very much sir. Actually, the bolts to be tightened are those in guadalupe bridge (mrt) if you are familiar sir. The ones used in steel and in concrete. I am not sure about the size, but i am sure it is bigger. I will check on the “torque multiplier” .
Btw, sir, your blog is amazing .
Welcome King. Just check the sizes of bolts. You can use torque multiplier from 30mm diameter bolt and above.
Once again thank you 🙂
Thanks for sharing mate!
Is Torque Inspection is mandatory in anchor bolts?
Hi Faisal,
No, not required.
Regards,
HI NOEL
CAN I GET THE STANDARD FORMAT OF QUALITY INSPECTION REPORT.
You can find the “10 Project Forms” I wrote. You can download from there.
Hi Noel,
About A325 7/8″ dia. bolts under 6″ in length.They all have the same thread length, but the bolt shaft is where the difference in length is. I have googled to death, what is the maximum number of threads sticking out of the nut, after the bolt has been tightened, and could find nothing.
All I saw was acceptable photos of tightened bolts which had the connections with different numbers of threads sticking out.
I can’t believe there is no information on this.
Thanks for any info on this mystery.
John
Hello John,
There is no mystery John if you ask the expert (kidding). You can find it in BS 5950 and RCSC. In BS, it said “at least 1 thread pitch after tightening” that is the requirement meaning you cannot make less than that. I suggest, if you can make a sticking out of 3 to 10 threads it looks nice as you can see in the photo above.
Hope this helps.
Noel
Greetings! Sir Noel, May i ask? Taking the circumstances that the nuts cannot be tightened using torque wrench due to its long thread. What would be the impact of reading torque when the bolt head is tightened? Does the torque of nuts has the same reading with the bolt head during the process? Thank you
You can use a long socket and or you can tight the bolt from the head with the same torque value. That’s why I told the erector to use bolts at least 10 mm protrusion from the surface of the nut.
Hello… I would like you to please tell me what is the size of the torque wrench being used in this video? Also, can you send your reply to my email address? [email protected]
Thank you… What type of torque wrench would you say should be used on structural steel?
You can use either “click type torque” or “bend type torque.”
Sir, What is the standard as reference for the 10% of bolt shall be tested
Excellent and concise article. Congrats.
Since we cannot inspect all of the bolts. Please, would you tell me what would be the percentage of inspection with the calibrated torque wrench?
Thanks in advance.
Thanks a lot. It is 10 percent in a group of bolts. Welcome.
What is the reference standard of 10%?
I am not sure what is the standard. It was written on our specification but most of the specifications are coming from the standards.
Excellent write up
Hi Shashi, thanks a lot for coming here.
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