Structural System Redesign · ETABS - Diaphragms modeled as Rigid and Semi-Rigid - Shearwalls...
Transcript of Structural System Redesign · ETABS - Diaphragms modeled as Rigid and Semi-Rigid - Shearwalls...
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Structural System Redesign• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
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• Existing Conditions• Proposal• Gravity Design• Lateral Design • Cost Comparison• Schedule Impact• Conclusions
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Location: New York, NYOwner: NYC HHCArchitect: RMJM HillierStructural Engineer: Greenman-Pedersen Inc.Construction: September 2008 – Mid 2012Cost: $160 million overall project costDelivery: Design-Bid-Build with multiple prime contracts
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•75,000 sq. ft. Addition to Existing Hospital•13 Stories•Steel Framed Addition•Concrete Existing Structure•11’ Floor-to-Floor
• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
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•Cellular Beams for all Gravity Members•Moment Frames•Braced Frames
• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
3rd Floor Framing Plan 8th Floor Framing Plan
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Design Choices- Use of Steel Framing- Removal of Column Line- Use of Moment Frames
Impact- Need Cellular Beams- Heavy Lateral Members- Further Restrictions on MEP systems
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• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
Proposal- Redesign current, steel-framed addition as a concrete structure utilizing two-way flat plate slab and shearwalls
Design Goals- Maintain regularity in design
SlabColumnShearwalls
- Provide design freedom for other systems- Design a more cost effective structural system
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• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
Codes- ASCE7-05
- Wind Loads as per Chapter 6- Seismic Loads using Equivalent Later Force
- ACI 318-08
Methodology- ETABS- RAM Concept- PCA Column- Microsoft Excel
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3rd Floor Plan
• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
Gravity System-12” slab- fc’ = 6ksi- 22’ x 24’ bay-16” columns- 20” columns
Lateral System- 6 shearwalls-16” shearwalls- 20” shearwalls
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• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
Design Loads- 26 psf Superimposed Dead Load- 80 psf Live Load
Deflection Limits- L/360 Immediate Live Load Defl.- L/480 Long-term Deflection- L/240 Long-term Deflection
Creep Factor = 220% of Live Load
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Slab
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3rd Floor Reinforcing Plan
Bottom Reinforcing
• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
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Slab
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3rd Floor Reinforcing Plan
Top Reinforcing
• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
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3rd Floor Deflection Plan
Max. long-term Deflection:
0.4438 in
Initial. LL Deflection:
0.0555 inAllowable:L/360 = 0.80 in
Allowable:L/480 = 0.60 in
• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
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Typical Column Details
Columns supporting 6 stories:16” x 16” fc’= 6 ksiColumns supporting 13 stories:20” x 20” fc’= 6 ksi
• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
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Slender Column Design
• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
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Column G/5.8 (6 stories):16” x 16” fc’= 6 ksiColumn F/5.8 (13 stories):22” x 22” fc’= 6 ksi
• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
Slender Column Design
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9th Floor Plan
• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
Column Shift- Control Deflections- Match Floorplan Layout
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• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
Column Shift- Control Deflections- Match Floorplan Layout
- 60” deep beam- 20” width
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• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
- 60” deep beam- 20” width
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Design AssumptionsETABS
- Diaphragms modeled as Rigid and Semi-Rigid- Shearwalls modeled as Membranes- 0.7 f22 modifier for shearwalls-0.35 I3 modifier for coupling beam-Deflection: H/400 for wind
0.015hx for seismic3.00” overall floor deflection3.50” overall deflection at roof
12.12.3 Building Separation. Allportions of the structure shall bedesigned and constructed to act as anintegral unit in resisting seismic forcesunless separated structurally by adistance sufficient to avoid damagingcontact under total deflection (δx) asdetermined in Section 12.8.6
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• Existing Conditions• Proposal• Gravity Design• Lateral Design • Cost Comparison• Schedule Impact• Conclusions
Seismic ForcesEquivalent Lateral Force Procedure
- Seismic Design Category SDC = B- Importance Factor I = 1.15- Response Modification Coeff. R = 4- Deflection Amplification Factor Cd = 4- Base Shear V = 303 k
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• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
Seismic DeflectionETABS Elastic Analysis
- EX Overall Deflection = 1.6257”- EY Overall Deflection = 1.1233”
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• Existing Conditions• Proposal• Gravity Design• Lateral Design• Cost Comparison• Schedule Impact• Conclusions
Final Seismic DeflectionAccidental Torsion
- Force applied at 5% eccentricity- Amplification of torsion:
A= (dmax/(1.2*davg))2 (Figure 12.8-1)
dmax = 1.693”
davg = 1.573”
Amplified Seismic Deflections- Amplification of Elastic Output
δx=Cd δxe/I *(Ta/T) (eq 12.8-15)
-Maximum Overall Floor Deflection2.9393” (EXMZ)
-Maximum Overall Roof Deflection3.2132” (EXMZ)
-Maximum Story Drift0.0022 (EXMZ)
Ax = 0.804 therefore Ax= 1.00
< 3.00” upper limit
< 3.50” upper limit
< 0.015 max allowable
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• Existing Conditions• Proposal• Gravity Design• Lateral Design • Cost Comparison• Schedule Impact• Conclusions
Wind Forces- Basic Wind Speed V = 100mph- Importance Factor I = 1.15
- Base Shear X-dir V = 382 k- Base Shear Y-dir V = 314 k
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Controlling Case- Seismic Deflection governed design- Wind Combinations produced highest forces- Provide Minimum Reinforcing:
(2) #5 bars @ 12” O.C. Each Way
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Cos
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Existing vs. Proposed- Compared elements of structure that change- Assumed 3% O&P- Materials, Labor, and Equipment- Moment Connections not considered
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Existing vs. Proposed- Existing Foundation $ 901,050- Proposed Foundation $ 1,281,495- Percent Increase ~ 40%
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Existing vs. Proposed
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Existing vs. Proposed- Existing Structure $ 10,329,667- Proposed Structure $ 9,760,392- Percent Saving ~ 5%-Overall Project Cost $ 130,000,000
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Sche
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Impa
ct• Existing Conditions• Proposal• Gravity Design• Lateral Design • Cost Comparison• Schedule Impact• Conclusions
Existing vs. Proposed- Existing Structure sequenced in two portions- Existing Duration 6.5 Months- Proposed Structure sequenced in three portions
~ 3 weeks per floor- Proposed Duration 12 Months
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Con
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• Existing Conditions• Proposal• Gravity Design• Lateral Design • Cost Comparison• Schedule Impact• Conclusions
Design Goal Achievement- Maintain Structural Regularity
- Promote design freedom for other systems
- Design a more cost-effective structure
Recommendations
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Que
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• Existing Conditions• Proposal• Gravity Design• Lateral Design • Cost Comparison• Schedule Impact• Conclusions
Thank You- Entire AE Faculty- Dr. Memari- Professor Holland- Professor Parfitt- AE Structural Professors
• Dr. Boothby• Dr. Geschwindner• Dr. Hanagan• Dr. Lepage
- Greenman- Pedersen Inc.- Friends and Family
Questions?