John Pillar John Pillar Hampton Inn & Hampton Inn & Suites Suites National Harbor, Md Md National Harbor, Advisor: Dr. Memari Memari Advisor: Dr. Distinguished Speaker Series, Spring 2007
Presentation Outline Presentation Outline � Existing Conditions Existing Conditions � � Proposal Proposal � � Structural Depth Structural Depth – – PT Slab Investigation PT Slab Investigation � � Construction Breadth Construction Breadth – – Cost and Construction Cost and Construction � Impact Impact
Presentation Outline Presentation Outline � Existing Conditions Existing Conditions � � Proposal Proposal � � Structural Depth Structural Depth – – PT Slab Investigation PT Slab Investigation � � Construction Breadth Construction Breadth – – Cost and Construction Cost and Construction � Impact Impact
Typical Floor Typical Floor
Existing Conditions Existing Conditions � 10 10- -1/2 1/2” ” Concrete flat plate with 2 Concrete flat plate with 2- -1/2 1/2” ” drop drop � panels panels � 12 12” ”x24 x24” ” columns columns � � Spread footing foundations Spread footing foundations � � Concrete shear wall lateral force resisting system Concrete shear wall lateral force resisting system � � 11 stories above grade 11 stories above grade � � 10 10’ ’- -3 3” ” typical floor to floor height typical floor to floor height � � Designed under IBC 2003 Designed under IBC 2003 �
Presentation Outline Presentation Outline � Existing Conditions Existing Conditions � � Proposal Proposal � � Structural Depth Structural Depth – – PT Slab Investigation PT Slab Investigation � � Construction Breadth Construction Breadth – – Cost and Construction Cost and Construction � Impact Impact
Presentation Outline Presentation Outline � Existing Conditions Existing Conditions � � Proposal Proposal � � Structural Depth Structural Depth – – PT Slab Investigation PT Slab Investigation � � Construction Breadth Construction Breadth – – Cost and Construction Cost and Construction � Impact Impact
New Proposal New Proposal � Replace original 10 Replace original 10- -1/2 1/2” ” normally reinforced slab with normally reinforced slab with � thinner post- -tensioned slab tensioned slab thinner post � lower seismic base shear lower seismic base shear � � more economical system more economical system � � Examine behavior: Examine behavior: � � new lateral response new lateral response � � punching shear conditions, slab deflection punching shear conditions, slab deflection � � Footings, lateral force resisting system Footings, lateral force resisting system � � Analyze new cost and schedule associated with flooring Analyze new cost and schedule associated with flooring � system switch system switch
Presentation Outline Presentation Outline � Existing Conditions Existing Conditions � � Proposal Proposal � � Structural Depth Structural Depth – – PT Slab Investigation PT Slab Investigation � � Construction Breadth Construction Breadth – – Cost and Construction Cost and Construction � Impact Impact
Presentation Outline Presentation Outline � Existing Conditions Existing Conditions � � Proposal Proposal � � Structural Depth Structural Depth – – PT Slab Investigation PT Slab Investigation � � Construction Breadth Construction Breadth – – Cost and Construction Cost and Construction � Impact Impact
PT slab is more economical PT slab is more economical � Slimmer slab profile (8 Slimmer slab profile (8” ” vs. 10.5 vs. 10.5” ”) ) � � Punching shear predicted to be ok Punching shear predicted to be ok � � Banded tendons spanning East Banded tendons spanning East- -West West � � Uniform tendons spanning North Uniform tendons spanning North- -South South � � Loading: Loading: 40 psf psf (live) (live) 40 � 100 psf psf (dead) (dead) 100 28 psf psf (partitions, (partitions, m/e/p m/e/p) ) 28 168 psf psf 168
Column Adjustments Column Adjustments
Tendon Profiles, Latitudinal Tendon Profiles, Latitudinal � 8 8” ” slab, cover requirements limit profile drape slab, cover requirements limit profile drape � � Tendons calculated to balance 90% of the dead Tendons calculated to balance 90% of the dead � load load � 9 strands in exterior longitudinal spans 9 strands in exterior longitudinal spans � � 12 strands in interior spans 12 strands in interior spans �
Tendon Profiles, Longitudinal Tendon Profiles, Longitudinal � 3 strands per tendon 3 strands per tendon � � Tendons spaced at 3 Tendons spaced at 3’ ’- -0 0” ” to 4 to 4’ ’- -0 0” ” o.c o.c. . � � End profiles terminated at center of slab End profiles terminated at center of slab � � Coordinate with slab openings/penetrations Coordinate with slab openings/penetrations �
PT investigation continued PT investigation continued � 12 12” ” x 24 x 24” ” columns adequate for punching shear columns adequate for punching shear � in all locations in all locations � Punching shear was found to be ok for worst case Punching shear was found to be ok for worst case � φ Vc column, φ Vc=110k>Vu=57k =110k>Vu=57k column, � Long term deflection is within appropriate limits Long term deflection is within appropriate limits � � Maximum deflection: Maximum deflection: � � positive positive – – 0.6 0.6” ” � � negative negative – – 0.2 0.2” ” �
Slab Stresses at Midspan Midspan Slab Stresses at � f f b at jacking: 146 psi psi Allowable: 0.6f Allowable: 0.6f’ ’c c i =1800psi b at jacking: 146 i =1800psi � � f f t at jacking: - -292 292 psi psi Allowable: 3 Allowable: 3 √ √ f f’ ’c c i =164psi t at jacking: i =164psi � � f f b at service: 370 psi psi Allowable: 0.45f Allowable: 0.45f’ ’c=2250psi c=2250psi b at service: 370 � � f f t at service: - -780 780 psi psi Allowable: 6 Allowable: 6 √ √ f f’ ’c=424psi c=424psi t at service: � � f f’ ’c c=5000 =5000 psi psi � � f f’ ’c c i =3000 psi psi i =3000 � � All conditions meet code, slab is ok All conditions meet code, slab is ok �
Other considerations Other considerations � Overall building weight reduced by 11% Overall building weight reduced by 11% � � Seismic base shear decreased by 11% with weight Seismic base shear decreased by 11% with weight � savings, from 594k to 530k savings, from 594k to 530k � lateral system redesign unnecessary lateral system redesign unnecessary � � 70k reduced axial load on worst case column, footings 70k reduced axial load on worst case column, footings � were found to be same size or very similar were found to be same size or very similar � footing redesign unnecessary footing redesign unnecessary � � Wind drift decreased by 0.8 Wind drift decreased by 0.8” ” � � Seismic drift decreased by 1.5 Seismic drift decreased by 1.5” ” �
Presentation Outline Presentation Outline � Existing Conditions Existing Conditions � � Proposal Proposal � � Structural Depth Structural Depth – – PT Slab Investigation PT Slab Investigation � � Construction Breadth Construction Breadth – – Cost and Construction Cost and Construction � Impact Impact
Presentation Outline Presentation Outline � Existing Conditions Existing Conditions � � Proposal Proposal � � Structural Depth Structural Depth – – PT Slab Investigation PT Slab Investigation � � Construction Breadth Construction Breadth – – Cost and Cost and � Construction Impact Construction Impact
Cost savings of $156,760 Cost savings of $156,760 � Increased cost for stressing tendons & labor Increased cost for stressing tendons & labor +$360,570 +$360,570 � � Decreased cost for rebar Decreased cost for rebar -$111,800 $111,800 - � � Decreased cost for slab Decreased cost for slab -$380,000 $380,000 - � � Other savings Other savings -$25,530 $25,530 - � 156,760 $ 156,760 $ This equates to a savings of approximately $172,100 after location and inflation are considered
Cost savings of $156,760 Cost savings of $156,760 � Increased cost for stressing tendons & labor Increased cost for stressing tendons & labor +$360,570 +$360,570 � � Decreased cost for rebar Decreased cost for rebar -$111,800 $111,800 - � � Decreased cost for slab Decreased cost for slab -$380,000 $380,000 - � � Other savings Other savings -$25,530 $25,530 - � 156,760 $ 156,760 $ This equates to a savings of approximately $172,100 after location and inflation are considered Savings equivalent: 24,586 engineering computation pads (200 page tablet)
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