Jump to content
  • Welcome to SEFP!

    Welcome!

    Welcome to our community forums, full of great discussions about Structural Engineering. Please register to become a part of our thriving group or login if you are already registered.

Sign in to follow this  
Waqas Haider

Relation between Temprature reinforcement and grade of steel

Recommended Posts

Assalam o alaikum dear fellows,

Why we need more temperature steel ratio for lesser grade of steel as shown by following relation?

For Fy = 40 ksi 

As(min) = 0.002bh

For Fy = 60 ksi

As(min) = 0.0018bh

 

Moreover, According to 7.12.1.2, it says

 
7.12.1.2 — Where shrinkage and temperature movements are significantly restrained, the requirements of 8.2.4 and 9.2.3 shall be considered.
 
And in its commentary it says
 
R7.12.1.2 — The area of shrinkage and temperature reinforcement required by 7.12.2.1 has been satisfactory where
shrinkage and temperature movements are permitted to occur. Where structural walls or columns provide significant
restraint to shrinkage and temperature movements, the restrain of volume changes causes tension in slabs, as well as
displacements, shear forces, and flexural moments in columns or walls. In these cases, it may be necessary to increase the
amount of slab reinforcement required by 7.12.2.1 due to the shrinkage and thermal effects in both principal directions (see
References 7.7 and 7.16).
 
Kindly tell how to increase this amount? Thanx.
Edited by Engr Waqas

Share this post


Link to post
Share on other sites

As you said, according to R7.12.1.2, first of all, reduce the modulus of rupture by half i.e. from 0.62√f'c to 0.31√f'c.

Second, increase the reinforcement as required for axial tension (T=phi As fy) in addition to what required for moment.

Share this post


Link to post
Share on other sites

Waqas,

The statement is asking you not to rely on temp and shrinkage steel values provided for cases where analysis shows higher amount is required. You can carry out the temperature analysis and add to that the amount of steel required due to shrinkage. You can calculate extra steel due to shrinkage based on how much strain would be caused by shrinkage or any other method if you are aware of.

Thanks.

Thanks.

Share this post


Link to post
Share on other sites
On ‎12‎/‎3‎/‎2016 at 6:23 PM, Engr Waqas said:

Why we need more temperature steel ratio for lesser grade of steel as shown by following relation?

For Fy = 40 ksi 

As(min) = 0.002bh

For Fy = 60 ksi

As(min) = 0.0018bh

Kindly give your value able comment over this also. thanks.

Is proposal of temp. steel by ACI based on the thing that this temp steel may have to bear temp stresses upto yielding and higher steel strength can support more portion of concrete in temp stresses so requiring less steel and vice versa?

If this steel ratio is quite higher as compared to yielding of steel then why cant we have same ratio for both of grade?

Edited by Engr Waqas

Share this post


Link to post
Share on other sites
5 hours ago, Engr Waqas said:

Is proposal of temp. steel by ACI based on the thing that this temp steel may have to bear temp stresses upto yielding and higher steel strength can support more portion of concrete in temp stresses so requiring less steel and vice versa?

What does the commentary say?

Thanks.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Our picks

    • *SEFP Consistent Design*<br style="color:#272a34">*Pile Design*<br style="color:#272a34">*Doc No: 10-00-CD-0005*<br style="color:#272a34">*Date: Nov 21, 2017*<br style="color:#272a34">
       

      This article is intended to cover design of piles using Ultimate Limit State (ULS) method. The use of ULS method is fairly new for geotechnical design (last decade). The method is being used in multiple countries now (Canada, Australia etc). The following items shall be discussed:

      Overview


      Geotechnical Design of Piles (Compression Loads, Tension Loads and Lateral Loads)


      Structural Design of Piles (Covering both Concrete and Steel)


      Connection of Pile with the foundation (Covering both Concrete and Steel)


      Pile Group Settlement


      Things to consider



       

      1. Overview

      Piles provide a suitable load path to transfer super-structure loads to foundation where shallow foundation are not suitable - this can be due to a number of reasons like existing space constraints or suitable soil strata is not present immediately below structure. Other uses can be to meet design requirements like to have reduced settlement etc.

      This article shall cover the use of straight shaft cast-in-place concrete piles and straight shaft driven steel pipe piles. There are a number of additional piles types like belled concrete piles, precast concrete piles, screw / helical steel piles etc but the discussion to choose a suitable pile type is not in the intended scope of this article. The article is intended  to discuss design requirements for straight shaft piles only (both concrete and steel) . The aforementioned topic about pile selection is a very diverse subject and requires a separate discussion on its own.

      Click on the link to read the full article.
       
      • 9 replies
    • I am suppose to design a pile foundation for a machine weighing approximately 50 tons and with an operational loading of 100 tons. 
      I ll appreciate your help in terms of guidance & provision of notes...  
       
      Thank you..
      • 36 replies
    • Material behavior can be idealized as consisting of an 'elastic' domain and a 'plastic' domain. For almost 200 years, structural design has been
      based on an elastic theory which assumes that structures display a linear response throughout their loading history, ignoring the post-yielding
      stage of behavior. Current design practice for reinforced concrete structures is a curious blend of elastic analysis to compute forces and moments, plasticity theory to proportion cross-sections for the moment and axial, load, and empirical mumbo-jumbo to proportion members for shear.

       

      From the book "Design of Concrete Structures with Stress Fields" by A. Muttoni,  J. Schwartz and  B.Thurliman.

       
      • 0 replies
    • Dear Fellow Researchers, Academicians, and research students,

       

      NED University of Engineering & Technology in collaboration with Institution of Engineers Pakistan (IEP) is organizing 9th International Civil Engineering Conference (ICEC 2017) on December 22-23, 2017 at Karachi, Pakistan.

       The congress details are available at its website www.neduet.edu.pk/icec

       Also attached is congress flyer for information and dissemination among your peers.

       Abstracts submission deadline has been extended till October 31, 2017.

      Please click on the link to see the full description.
      • 0 replies
    • AoA all,

      Is it mandatory to do column concreting upto the soffit of the beam in a single pour ?

      What code says about the construction/cold joint location in column ?

      Majority of the contractors are pouring the column concrete upto the soffit of the beam (full height of the column), some contractors leave the column height about 9" to 12" below the beam level and then fill this 9" to 12" column height with the beams & slab concreting. On one site column concreting was stopped at the mid height and the remaining half was filled on the next day.

      Thanks

       

       
      • 5 replies
    • AOA 

      i am facing problems in shear wall design .what are the pier and spandral ?what will be the difference when we assign pier or spandral? without assigning these the shear wall design is incomplete .

      i am taking about etabsv16

      someone have document about shear wall design plz provide it 

      thank you

       
      • 10 replies
    • Salam Members,

      Congratulations to Engineers, PEC has become full signatory of Washington Accord, what are the benefits to Pakistani engineers for this agreement. 

       

      Regards   

       

       
      • 3 replies
    • Please clarify the following confusions one by one:-

       

      1. If we run P-delta analysis in ETABS, then should we ignore stiffness property modifiers for beams and columns? I have heard that if we perform P-delta analysis and apply stiffness modifiers at the same time then the moment magnification process is doubled...?

       

      2. ETABS considers selenderness of a column by applying moment magnification factors. If we run P-delta analysis also, does it mean that the selenderness of column is being over-estimated? I mean once the moments are magnified in P-delta analysis process and again through moment magnification process?

       

      Please help me understand the software myth and clarify above confusions.
      • 1 reply
    • Assalam o alaikum.
      According to ACI 12.5.2,
      development length for fc' = 3000, fy=60000, for normal weight concrete and epoxy less reinforcement, The required development length comes out to be
      for #3 = 8.2 inch
      for #4 = 10.95 inch
      for #6 = 16.42 inch
      for #8 = 21.9 inch
       
      And if in my case, ACI 12.5.3 is not fulfilled, it means now i have to provide ldh as mentioned above. ldh is STRAIGHT EMBEDMENT LENGTH + RADIUS OF BEND + ONE BAR DIAMETER as shown in figure attached. Now my question is, if in my case, main reinforcement of beam is of #6 and #4, minimum column size required will be 18 inch and 12 inch respectively. Lets say by any means, i can not select #4, #3 bars and size of column where bars are to be terminated is 12 inch, how to fullfil this development length???
      • 11 replies
    • Dear all,

      I am trying to design shearwalls through ETABS with temperature load applied over shell. At various location, spandral section fails in Shear due to temperature and piers (sometime in shear, mostly in flexure).  (See Attached Image)

      Certainly all the problem in Shearwalls are due to temperature. I don't want to increase cross section of spandral or pier at some location just due to temperature load case as it will appears non-uniform with rest of the wall. 

      I have seen stiffness modifier affect distribution of forces and also rigid/semi rigid daiphragm assumption. 

       

      Can anybody guide how to properly design the shear wall with temperature load applied in ETABS or share any similar experience. Thanks in Advance.    
      • 15 replies
  • Recently Browsing   0 members

    No registered users viewing this page.

×

Important Information

By using this site, you agree to our Terms of Use and Guidelines.