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mohan1441 SEFI Member
Joined: 18 Jun 2008 Posts: 2
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Posted: Sat Apr 13, 2013 7:45 am Post subject: PSC box design as per IRC:112-2011 |
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Dear all,
In design of PSC box girder as per IRC:112-2011,
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The following Load combinations as given in Table 3.3 of IRC:6-2010 have been checked ..
For Max. & min stress limits
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Serviceability Limit state:Rare combination (1.0DL+1.0SIDL+1.0WC+1.0PRESTR+1.0LL+0.6TL)
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Serviceability Limit state:Rare combination (1.0DL+1.0SIDL+1.0WC+1.0PRESTR+0.75LL+1.0TL)
<o> </o>
For Deflection,crack width
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Serviceability Limit state:Frequent combination (1.0DL+1.0SIDL+1.0WC+1.0PRESTR+0.75LL+0.5TL)
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Serviceability Limit state:Frequent combination (1.0DL+1.0SIDL+1.0WC+1.0PRESTR+0.2LL+0.6TL)
<o> </o>
For Permanent stress
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Serviceability Limit state:Quasi-permanent combination (1.0DL+1.0SIDL+1.0WC+1.0PRESTR+0.5TL)
<o> </o>
My query is in above all combinations psf for prestess is 1.0, whereas in IRC:112-2011, cl.7.9.5 po.no:6 ,in serviceability limit state, psf of 1.1 & 0.9 shall be used for prestress, in such case, is it reqd. to check the above LC’s for these two factors separetaly.
Kindly explain above clause.
regards
P.C.Mohan
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akshat_bansal SEFI Member
Joined: 29 Oct 2013 Posts: 2
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Posted: Tue Oct 29, 2013 7:54 am Post subject: |
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In IRC:6-2010, in notes below it is mentioned in point no. 4 that factors from prestressing need to be taken from relevent code (i.e. IRC:112 in this case).
Out of 1.1 and 0.9, the factor which is unfavourable needs to be considered. In complex structures, it would be best to check with both factors. Otherwise in simply supported bridges judgement can be used to select which factor to be used. If it is not clear, it is best to check with both 1.1 and 0.9. _________________ Regards,
Akshat Bansal
Chief Technical Officer
Force Structural Engineers Pvt. Ltd.
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