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EIT2 (Structural) (OP)
26 Jan 04 7:21
Consider a thirty foot long, W12x30.  Must fit into an existing, occupied, office building and bear on masonry walls 28'-8" apart.  The contractor wants to cut the beam in half (mid-span), erect in place, and full-pen weld all around.

Considering all weld conditions acceptable, does the full-penetration weld qualify as full restoration of the original section properties?
ERV (Structural)
26 Jan 04 9:17
EIT2,

To answer your question directly, NO. Based on load and factor of safety, I would consider stiffener plates. Check the AWS D1.1 code.

http://www.aws.org/
Helpful Member!  Rich2001 (Mechanical)
26 Jan 04 9:35
AWS D1.1 Code 1998

2.26    Connections or Splices--Tension and Compression Members

Connections or splices of tension or compression members made by groove welds shall have complete joint penetration (CJP) welds. Connections or splices made with fillet or plug welds, except as noted in 2.31, shall be designed for an average of the calculated stress and the strength of the member, but not less than 75% of the strength of the member; or if there is repeated application of load, the maximum stress or stress range in such connection or splice shall not exceed the fatigue stress permitted by the applicable general specification.

2.26.1 RT or UT Requirements. When required by Table 2.4, weld soundness, for CJP groove welds subject to tension and reversal of stress, shall be established by radiographic or ultrasonic testing in conformance with section 6.



Yes, the full-penetration weld qualify as full restoration of the original section properties. However, one must be careful.

Have a Welding Inspector witness cutting the beam through final weld, i.e. he must be there continuously, anytime cutting  and welding work is being done. If you don't witness it how do you know?
 
Things to watch preheat, interpass temperatures, preparartion of the basemetal, condition of the electrodes (i.e. time out of oven for low hydrogen electrode. Current Voltage, travel speed, i.e heat input. Cleaning between passes. Check welder qualifification, welder needs to be qualified in Overhead and Vertical plate groove test or 6G pipe.

One-side groove welds are prohibited without backing
The weldment must be NonDestructively examined either Ultrasonic or radiograpghy.  

If the contractor does not do this on a regular bases expect to repairs.

How many repairs will you or your client allow?  With each repair more heat is being added to the steel changing the microstructure of the steel.  Many places do not alllow more than 3 repairs, any additional requires new members.

 
Helpful Member!  krus1972 (Structural)
26 Jan 04 10:51
EIT2,

It does, however, there are a few things you must consider beyond the AWS D1.1.

Based on ASD using E70xx electrodes the allowable for the weld material itself is 21 KSI. If the beam is A36 the MAX. allowable for the beam capacity is 21.6ksi.

If the beam is Grade 50 the the allowable is 30ksi. If you are using GRADE 65 the allowable will be 39 KSI. Since the splice is made at center and the weld material allowable is 21 KSI the weld material is going to control the capacity of your beam in this case.

Lastly it is highly recommended that you specify an ULTRASONIC test be performed on the connection. Inspectors who inspect weleded conntections know exactly what this is. The ultrasonic test will insure that there is solid fill all the way down to the base metal around the entire beam and there are no hidden bubbles or gaps due to poor welding from the contractor. Since the contractor is the one who wants to cut and re-weld the beam have him retain the services of the inpector and furnish you a copy of the report.


Hope this helps


Jeffrey A. Krus P.E.
 

 

Helpful Member!  Lutfi (Structural)
26 Jan 04 10:53
You can either make the splice a bolted or welded one. Welded connection should be full pen. Make surethat theconnection will develope the beam section. I do not recommend to place the splice in the middle since it is the most likely location for maximum bending stress. I would consider the middle third (1/3 span).

In bolted connection ensure that you have bottom and top plates and shear (web) plates. I also believe that field welding is more expensive and is harder to control the quality of thework.

Good luck.
FFIELD (Structural)
26 Jan 04 16:20
Welding a beam at it's max.  moment point is perfectly acceptable as long as you do it properly.  Call for independent special inspector to view all aspecte fo the job.  Prepare spliced ands properly according to the AISC and AWS.  Use proper weld rods to match the beam material specs.  Use preheat if called out by the AWS specs.  If you are concerned call for ultrsonic inspection of the completed welds.

If you are really concernen add doubler plates to the bottom and top flanges and full penetration weld these.

You will be able to sleep nights and the owner will be a little poorer.
JoeTank (Structural)
26 Jan 04 16:50
krus1972,
Isn't the 21.0 ksi allowable for stress on the throat of a fillet weld or partial penetration groove weld.  For an E70XX electrode and an A36 beam, the allowable stress would be based upon the base metal only.  I'm snowed into today, so I am looking at an old blue AISC.

Steve Braune
Tank Industry Consultants
www.tankindustry.com

Focht3 (Geotechnical)
26 Jan 04 17:22
Hire the inspector yourself - don't let the contractor control this!  Put a clause in the contractor's agreement that retest costs must be paid by the contractor.

While I agree that UT is the "best" tool for most jobs, listen to the welding inspector.  Other tests might be useful, too...



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.

krus1972 (Structural)
26 Jan 04 18:11
EIT2,

If you are the design engineer of record you DO NOT have to be the one that hires the inspector to check the contractor's work. It is the contractor's responsbility to verify the quality of his/her own work not you. You are not in the business of quality checking and checking workmanship of contractors. This includes to the quality welds.

The contractor should submit the field erection and shop drawings showing exactly how he intends on erecting and fabricating each piece of the project. These drawings should clearly identify the beam splice and how he/she intends on reconnecting it together. It is up to YOU the engineer of record to insure that his/her methods DO NOT impair your original design intent. If the contractor shows a splice connection that you prove is ok during your review of the shop drawings then your job is DONE. You then send back the shop drawings. It's not your job to watch over their shoulder ever step of the job. Your job is to just determine if the connection as they show on the shop drawings is adequete from the design stand-point.

To go further in this issue is soley an indivdual engineer's judgment call. You can check their connection and approve it or disapprove it and lay it to bed.

Assuming the connection as they show it proves ok from the design stand point. What I normally do for a situation like this is to approve the connection on the shop/erection drawings and mark a note on the drawing requesting an independent inspection report to be submitted after the beam is welded.

By doing it this way you are covered even if the contractor never submits the report to you. You are not responsbile for the quality and workmanship of the contractor - only the design.


Jeffrey A. Krus P.E.
 

 
 
CWIC (Specifier/Regulator)
26 Jan 04 20:32
The RDP or the Contractor may hire the RT/UT technician.

The contractor is responsible for their work. However, due to the nature of the work, the RDP may request additional inspection or testing to comfirm the work complies with the minimum requirements.

Most of my clients are the RDP. QA inspections or testing are performed in accordance with AWS D1.1:2002, 6.1.2.2 (Verification Inspection). The Contractor performs their inspection/testing per D1.1:2002, 6.1.2.1 (QC). You may specify the technician is paid by the contractor but reports directly to the RDP.

I also agree with the fact the [weld] repair satifies the requirement for  "...full restoration of the original section properties..." Beam/girder splices are not uncommon for retrofits.

One more note on this subject, many times inexperienced contractors botch this simple weld for one reason or another. My photo archive proves this point numerous times. Particular care must be implemented at the flange/web interface (K area). These are where most of the mistakes are made by the welder. Weld initiation/termination is critical at this location. UT testing at this location is entirely dependant on the skill of the technician. If a weld repair is utilized, make sure the repair is monitored (as noted above) by a welding inspector. Weld and run-off tabs are critical to making this happen at the weld terminations.

Good luck.  
krus1972 (Structural)
26 Jan 04 21:17
One thing I forgot to mention in my earlier post.

If the contractor does submit an inspection report make sure that the  report states in words that the connection satisifes ALL applicable AWS requirements for this type of weld. YOU the design engineer do not have to open the AWS book and show them what needs to be followed and what doesn't. You just state on the design drawings "All welding must conform to the latest applicable AWS code requirements".

Make sure the inspection report states in words that the weld conforms to the design drawings requirements also. Make sure the inspection report is P.E. stamped and signed. You may now sleep at night.

If they submit a report that has a bunch of numbers from tests and nothing more then this is useless. Make sure they expliciatly write the statments I've indicated above.

Jeffrey A. Krus P.E.

ml13 (Structural)
28 Jan 04 6:22
Other potential issues:  
1. Will the weldor be able to perform a (presumed)overhead full pen weld in the occupied space?  Seems like a lot of stopping and starting to me.  
2. Will the backing be back-gouged and reinforced with fillet welds?  Space might be a problem for that.
3. Also, there are fire issues to deal with if it is close to the ceiling, or sparks flying all about, not to mention ventilation issues.

Considering all the quality control issues mentioned above, I would look at a bolted connection.

MTL, P.E.
jheidt2543 (Civil/Environmental)
28 Jan 04 6:41
I agree with ml13, welding inside an existing office building presents lots of problems that you would not have with a bolted connection, particularly if the Owner wants to maintain operations in the building during the remodeling.  Sometimes, even though you CAN DO something, it doesn't mean you SHOULD DO it.

Just another thought, I have remodeled buildings where we cut slots through the exterior walls to insert a full length beam (windows arn't always in the right spot).  So, that could be an option in your case, slot the walls and slide the beam onto a rolling scaffold, then use duct hoists to jack it into place.
Helpful Member!  CSEllc (Structural)
30 Jan 04 1:15
EIT2, you have gotten a lot, for the most part, good advice.  Now let me offer you a little bit.

1. If you go with the Full penetration weld, the "ends" of the beam that will be welded must be prepared in accordance with AWS and AISC specifications to meet the criteria of pre-qualified weld.  If the ends are not prepared accordingly, the joint is not classified as a "pre-qualified joint." As such, proper welding procedures need to be written and sample joints must be tested to insure the joint welding procedures are acceptable.  

2. Have the steel fabricator submit copies of the shop drawings.  Have them also submit copies Spec sheet of the welding electrode they intend to use.  You should check the electrode is acceptable for use on this steel.  Look at AWS D1.1-96, Table 3.1, "Prequalified Base Metal-Filler Material Combinations for Matching Strength".  If you are not familiar with the fabricator, you should provide the testing lab a copy of the approved submittals.  Don't rely on the inspector to get a copy in the field from the welder.  Most likely, he is a outside sub to the fabricator and won't have the info.  

3. Ask for copies of the welder certification.  Not all welders are certified to weld in all positions, "unlimited" thicknesses, or with different processes SMAW vs. FCAW.  PAss along a copy of the certification to the inspector.  Most good inspectors know the welders in the area and most likely have "certified" them.  However, there may be that one welder that is not known.  (It also makes shure that the welder on the job is same person the fabricator said would be on the job.)

4. A CWI, HIRED BY THE OWNER AND PAID FOR BY THE OWNER, must be present before the welding begins to inspect for proper joint preparation,etc., during the welding operations - to inspect that proper interpass heat is being used, that slag is being removed, etc. - and after the joint is completed to inspect for any visual defects.  
Ask for a copy of the persons certification if you are not familiar with the inspector.

5. Thge CJP weld must be ultrasonically tested by an ASNT TC-1A Level 2 or Level 3 technician certified in UT testing.  The technician should be HIRED and PAID by the OWNER.  If you are not familiar with the testing lab's technician preforming the inspection, ask for a copy of his certification and a copy of the testing procedures he was certified to. ASNT TC-1A certification does not state the person qualified to perform UT testing.  It states that the person is qualified to perform UT testing to a certain set of procedures, or steps.  In other words, Joe B works for ABC Testing labs and is a certified Level 2 in UT testing and CWI. Joe leaves ABC Testing Labs to go to work at XYZ Testing, according to ASNT Standards, Joe is no longer a certified Level 2 UT technician until he re-certifies himself with the UT inspection procedures used at XYZ Testing.  However, regardless of what testing lab he works for he will always be a CWI because AWS certifies the person is qualified to inspect the welds based on a recognized standard.

Some engineers might say I'm a little jaded with some of my recommendations.....let's just say I've been there before and don't want to go back.

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