www.sefindia.org

[ibarua]

10th Jan 2009

Don't great minds think alike?

I.B.


On Fri, 09 Jan 2009 jatfuentes wrote :

[ibarua]

10 Jan 2009

The bolt has necessarily to project beyond the sleeve to accommodate the nut.

I.B.


On Fri, 09 Jan 2009 pravin.pai wrote :

[vipul_ahuja]

Why can't a simple coupler be used. Chip off some concrete if greater lap is required. If not much room is available for coupler, cut off a little bit of bolt shank to make it available.

If welding is done, it will be hard to align the new welded portion so the nut wont bear properly over the base plate. There is so much notching in the thread root; any bending in the bolt shank will initiate a fracture.

Thanks & regards

Vipul Ahuja

[jatfuentes]

Thanks Mr. r.anna

I visited the site that you sent.  
I found an interesting article in Internet that I send in attach.
Regards,
jatfuentes

De: ranna [mailto:forum@sefindia.org]
Enviada em: sábado, 10 de janeiro de 2009 04:17
Para: general@sefindia.org
Assunto: [SEFI] Re: Welding Anchor Bolts



the anchor bolt can definitely be welded.
for welding requirement kindly contact
welding research institute
bhel,
trichy 620014
phone 0431 2520266
r.anna
ranna@bheltry.co.in (ranna@bheltry.co.in) (ranna@bheltry.co.in (ranna@bheltry.co.in))

jatfuentes wrote:    
--auto removed--

Posted via Email

[Dr. N. Subramanian]

Dear Mr. Jatfuentes

Is the anchor bolt, referred by you is made of high-strength steel?

High strength steels tend to be more sensitive to cracking than mild steels, which is why implementing good heat control prior to and during the welding process is crucial. First, preheating is a best step toward controlling the temperature gradient, or the range of temperature increase and decrease that occurs during welding. This is especially important, as welding on a cold piece of high strength steel will cause the material to heat up too quickly, and in turn cool too rapidly. This rapid cooling is the leading cause of cracking and preheating helps prevent it.

Likewise, welders need to maintain the correct interpass temperature for a given thickness of high strength steel. Doing so prevents a larger heat affected zone (HAZ) from forming during welding; HAZ is the area between the weld deposit and the base metal and an area that is prone to cracking. Maintaining interpass temperatures also reduces changes to the grain structure of the steel during cooling, which in turn limits any mechanical changes that could adversely affect the steels’ toughness or tensile strength. Welders can use contact pyrometers, Tempilstiks or other heat-sensing devices (including infared) to track the interpass temperature specified for their particular welding procedure.

As with any welding process, controlling travel speed and maintaining the recommended welding parameters (volts, amps) minimizes heat input when welding high strength steels.

Choosing filler metals with the least amount of hydrogen content, as well as those with good toughness (high impact values) and the appropriate strength is key when welding high strength steels. Each of these features also helps prevent cracking.


Carbon equivalant also places an important role in weldability; See pp. 20 of my book on steel structures



Regards

Subramanian








Dr.N.Subramanian,Ph.D.,F.ASCE, M.ACI,

Consulting Structural Engineer
Maryland, USA

See my books at: www.multi-science.co.uk/subramanian-book.htm
www.oup.co.in/search_detail.php?id=144559





--- On Sat, 1/10/09, jatfuentes <forum@sefindia.org> wrote:

[jatfuentes]

Dear Dr. Subramanian

The chemical composition of SAE 1020 is : C=0.23, Mn=0.6; P=0.030 and S=0.05
Specifications  don´t say nothing about Cr, Mo, V, Ni and Cu ( I suppose that don’t have this elements).

Applying the formula for  equivalent carbon  Ceq = (C+Mn)/6 + (Cr+Mo+V)/5 +(Ni+Cu)/15   
 I obtain Ceq = 0.138 less than 0.30.
Then I can deduct that this steel have good weldability

This steel SAE 1020 is very common here in Brazil for the design of anchor bolts. Its mechanical properties are Fy = 210 MPa and Fu=380 MPu.

Thanks for your advice.
Sincerely,
jatfuentes

De: drnsmani [mailto:forum@sefindia.org]
Enviada em: sábado, 10 de janeiro de 2009 23:37
Para: general@sefindia.org
Assunto: [SEFI] Re: Welding Anchor Bolts



Dear Mr. Jatfuentes

Is the anchor bolt, referred by you is made of high-strength steel?

High strength steels tend to be more sensitive to cracking than mild steels, which is why implementing good heat control prior to and during the welding process is crucial. First, preheating is a best step toward controlling the temperature gradient, or the range of temperature increase and decrease that occurs during welding. This is especially important, as welding on a cold piece of high strength steel will cause the material to heat up too quickly, and in turn cool too rapidly. This rapid cooling is the leading cause of cracking and preheating helps prevent it.

Likewise, welders need to maintain the correct interpass temperature for a given thickness of high strength steel. Doing so prevents a larger heat affected zone (HAZ) from forming during welding; HAZ is the area between the weld deposit and the base metal and an area that is prone to cracking. Maintaining interpass temperatures also reduces changes to the grain structure of the steel during cooling, which in turn limits any mechanical changes that could adversely affect the steels’ toughness or tensile strength. Welders can use contact pyrometers, Tempilstiks or other heat-sensing devices (including infared) to track the interpass temperature specified for their particular welding procedure.

As with any welding process, controlling travel speed and maintaining the recommended welding parameters (volts, amps) minimizes heat input when welding high strength steels.

Choosing filler metals with the least amount of hydrogen content, as well as those with good toughness (high impact values) and the appropriate strength is key when welding high strength steels. Each of these features also helps prevent cracking.


Carbon equivalant also places an important role in weldability; See pp. 20 of my book on steel structures



Regards

Subramanian








Dr.N.Subramanian,Ph.D.,F.ASCE, M.ACI,

Consulting Structural Engineer
Maryland, USA

See my books at: www.multi-science.co.uk/subramanian-book.htm
www.oup.co.in/search_detail.php?id=144559





--- On Sat, 1/10/09, jatfuentes wrote:    
--auto removed--

Posted via Email

[Dr. N. Subramanian]

Dear Mr. Jatfuentes

Since Fy is only 210 MPa, and since Ceq is only 0.138, you can weld it.

Best wishes
Subramanian

Dr.N.Subramanian,Ph.D.,F.ASCE, M.ACI,

Consulting Structural Engineer
Maryland, USA

See my books at: www.multi-science.co.uk/subramanian-book.htm
www.oup.co.in/search_detail.php?id=144559





--- On Sun, 1/11/09, jatfuentes <forum@sefindia.org> wrote:

[jatfuentes]

Thank you for your reply Dr. Subramanian,
Regards,
jatfuentes

De: drnsmani [mailto:forum@sefindia.org]
Enviada em: domingo, 11 de janeiro de 2009 18:38
Para: general@sefindia.org
Assunto: [SEFI] Re: Welding Anchor Bolts



Dear Mr. Jatfuentes

Since Fy is only 210 MPa, and since Ceq is only 0.138, you can weld it.

Best wishes
Subramanian

Dr.N.Subramanian,Ph.D.,F.ASCE, M.ACI,

Consulting Structural Engineer
Maryland, USA

See my books at: www.multi-science.co.uk/subramanian-book.htm
www.oup.co.in/search_detail.php?id=144559





--- On Sun, 1/11/09, jatfuentes wrote:    
--auto removed--

Posted via Email

[gsparsan]

There is another problem that may need to be considered in my opinion.

Welding of the anchor bolt which is already cast in will heat the anchor bolt. There is a risk of debonding with the concrete. If washer plates (or anchor plates) are used to resist uplift, this is not a problem. But if the bonding between the bolt and the concrete is being relied upon, can this be a potential problem?

[jatfuentes]

Dear Mr. gsparsan,
Yes ,the anchor bolts have a square plate stiffened at the embedment end in order to form a concrete cone.
Thanks for your advice
jatfuentes

De: gsparsan [mailto:forum@sefindia.org]
Enviada em: segunda-feira, 12 de janeiro de 2009 09:22
Para: general@sefindia.org
Assunto: [SEFI] Re: Welding Anchor Bolts



There is another problem that may need to be considered in my opinion.

Welding of the anchor bolt which is already cast in will heat the anchor bolt. There is a risk of debonding with the concrete. If washer plates (or anchor plates) are used to resist uplift, this is not a problem. But if the bonding between the bolt and the concrete is being relied upon, can this be a potential problem?

Posted via Email