PEER/SSC Tall Building Design Case study #2
Typical Plan View at Ground Floor and Below
Typical Plan View at 2 nd Floor and Above
Code Design
Code Design Shear Wall properties Shear wall thickness and concrete strength t = 18 f c = 5,000 psi 20 th t = 24 f c = 6,000 psi
Code Design Frame Properties Frame column concrete strength f c = 5,000 psi Frame Frames Beam A Properties & F Interior & 30 Corner x 36 columns f c 36 = 5000 x 36 psi 15 th f c = 6,000 psi 10 th f c = 8,000 psi Ground f c = 10,000 psi
Code Design Frame Properties Frame column concrete strength f c = 5,000 psi Interior columns Frames 2 at & gridline 5 C.5 Interior 46 x 46 columns from at Ground gridline to B 10& th E 42 42 x x 42 42 from Ground 10 th to to 25 25 th th 36 x 36 from 25 th to Roof 15 th f c = 6,000 psi 10 th f c = 8,000 psi Ground f c = 10,000 psi
Code Design Periods and Base Shear Site specific design response spectra Periods: T 1 = 5.50 sec. T 2 = 4.97 sec. T 3 = 2.98 sec. Design base shear: V B = 0.043 W
Code Design Static Shear Distribution
Code Design Inter-story Drifts Maximum inter-story drift allowed 0.020 h n
LATB Design
Exceptions from LATBSDC 1. Service level check is for an earthquake event of 25 year return period with 2.5% viscous damping. 3. Up to 20% of the elements with ductile actions are allowed to reach 150% of their capacity under the serviceability check. 5. The minimum base shear specified by the LATBSDC (2008) is waived. 7. Strengths for ductile actions at service level are calculated using strength reduction factors per ACI 318-08.
Shear Wall Concrete Strength and Thickness Comparison Code Design Performance Design t = 16 f c = 5,000 psi t = 18 f c = 5,000 psi 30 th t = 18 f c = 6,000 psi 20 th 20 th t = 24 f c = 6,000 psi t = 24 f c = 8,000 psi
Corner Column Concrete Strength and Size Comparison Code Design Performance Design 36 x 36 f c = 5,000 psi 30 th f c = 5,000 psi 36 x 36 42 x 42 22 nd 18 th f c = 6,000 psi 15 th f c = 6,000 psi 10 th 10 th f c = 8,000 psi f c = 8,000 psi Ground 46 x 46 3 rd f c = 10,000 psi f c = 10,000 psi
Response Spectrum Analysis for Service Level Earthquake LATB Design
LATB Design Service Level Periods and Base Shear 2.5% damped service level site specific response spectra Periods: T 1 = 4.13 sec. T 2 = 3.81 sec. T 3 = 2.21 sec. Base Shear: V Bx = 0.043 W V By = 0.047 W
Strength of Elements at Service Level Ductile actions: Brittle actions: Expected material properties φ per code Specified material properties φ per code CAUTION: Specified material properties φ per code Could result in the same design as that prescribed by code
Inter-story Drifts at Service Level Overall drift allowed at service level 0.005 h n
Pier 1 Service Level Peak Shear on X Direction
Coupling Beam Peak Shear Demand at Service Level 150% φv Nexpected 20% of elements
Frames 2 & 5 Beam Moment Demand at Service Level Corner Beam-Column Joint Interior Beam-Column Joint Negative Moments Positive Moments Negative Moments Positive Moments 150% φμ Nexpected 20% of elements
Step by Step Time-History Non-Linear Analyses at MCE Level LATB Design
Collapse Prevention MCE Level Acceptance Criteria
Element Properties for Non-Linear Model Expected material properties φ of 1 Demand Actions at MCE Level Ductile actions: Average of 7 records Brittle actions: Average of 7 records times 1.5 Element Capacity at MCE Level Expected material properties φ equals 1 Specified material properties φ equals 1
Building 2B MCE Periods and Average Base Shear MCE target response spectra Periods: T 1 = 4.93 sec. T 2 = 4.50 sec. T 3 = 2.78 sec. Base Shear: V Bx = 0.106 W V By = 0.099 W
Peak Story Shear at MCE Level
Inter-story Drifts at MCE Level on X direction Maximum inter-story drift allowed at MCE level 0.030 h n
Pier 1 MCE Average Shear on X Direction
Compression Strain at Corner by Pier 1 Maximum compression strain allowed for for unconfined concrete ε u = 0.015 0.003 in/in
Coupling Beam Rotation at MCE Level Maximum Coupling Beam rotation allowed θ u = 0.06 rad
Corner Column Peak Shear on X Direction at MCE Level
Corner Column Peak Compression at MCE Level 0.4 f c exp A g
Frame A Peak Beam Rotation at MCE Level θ u = 0.045 rad
Period and Base Shear Comparison Code design periods T 1 = 5.5 sec. T 2 = 4.97 sec. T 3 = 2.98 sec. Base Shear: V Bx = 0.043 W V By = 0.043 W Service level periods T 1 = 4.13 sec. T 2 = 3.81 sec. T 3 = 2.21 sec. V Bx = 0.043 W V By = 0.047 W MCE level periods T 1 = 4.93 sec. T 2 = 4.50 sec. T 3 = 2.78 sec. V Bx = 0.105 W V By = 0.098 W
Corner Column Axial Load Comparison Compression Code design column at seismic base: 36 x 36 column f c = 8,000 psi Non-linear design column at seismic base: 46 x 46 column f c = 10,000 psi 150% increase
Code Maximum Axial Load φp n,max = 0.8φ [0.85f c(a g -A st ) + f y A st ] Eq. 10-2 ACI 318-08 φp n / (f c Ag)
Frame Beam Longitudinal Reinforcing Comparison Code design: Performance design: 4#9 T&B 29 th 4#9 T&B 8#9 T&B
Coupling Beam Diagonal Reinforcing Comparison Code design: Performance design: 4#10 32 nd 4#9 6#10 21 st 21 st 8#11 14 th 4#11 10 th 10#11 6#10
PEER Design
PEER Design vs. LATB Design The return period for the service level earthquake is 43 years At service level, all the elements considered to have ductile behavior are allowed to have a demand to capacity ratio greater than 1.0 but less than 1.5. Where compression Pu 0.3f c exp A g element is considered ductile The capacity for ductile actions is calculated using expected material properties and φ = 1.0
PEER Design Linear Modal Spectral Analysis at Service Level
43 vs. 25 Years Return Period Earthquake At T = 4.0 sec. Demand increase : 0.051 /0.035 = 1.45
PEER Design Inter-story Drift at Service Level Overall drift allowed at service level 0.005 h n
PEER Design Coupling Beam Peak Shear Demand at Service Level 150% V Nexpected
PEER Design Frame Beam Moment Demand at Service Level M service > 1.5 Mn exp
PEER Design Corner Column Peak Axial Compression at Service Level
PEER Design Pier 1 Peak Axial Compression at Service Level
PEER Design Pier 1 Moment Demand at the Base M service X = 17,798 k 2 M service Y = 54,441 k 2 P service = 882 kip (Tension) M nexp X = 6,648 k 2 M nexp Y = 20,336 k 2 M service / M nexp = 2.70 > 1.50
PEER Design Damage Assessment at Service Level Step by Step Time-History Non-Linear Analyses
PEER Design Inter-Story Drifts at Service Level
PEER Design Overall Peak Shear on X Direction
PEER Design Comparison of Peak Story Shear on X Direction at Service Level
PEER Design Coupling Beam Peak Rotation Demand at Service Level
PEER Design Coupling Beam Rotation Demand at Service Level Chord rotation limit state suggested by ASCE 41-06 for Immediate Occupancy Performance Level (θ = 0.005 rad) Testing and Modeling of diagonally Reinforced Concrete Coupling Beams. Coupling beam design is acceptable Maximum Naish, David, rotation Fry, demand Andy, at Klemencic, Level 8 Ron and Wallace, John. (2009) (θ = 0.0036 rad) At a rotation of θ = 0.01 rad. the maximum observed Average crack rotation width for demand 7 coupling at Level beam 8 specimens is 0.095 in. (θ = 0.0015 rad)
PEER Design Comparison of Peak Axial Compression at Pier 1
PEER Design Compression Strains at Corner by Pier 1 Peak average compression strain ε c = 0.00074 in/in Shear wall design is acceptable
Frame Beam Peak Rotation Demand
Frame Beam Rotation Demand Approximate beam rotation when concrete strain reaches 0.003 Beam rotation limit state suggested by ASCE 41-06 for Immediate Occupancy Performance Level Maximum rotation demand at Level 29 Frame beam design is acceptable (θ = 0.0047 rad) Average rotation demand at Level 29 (θ = 0.0032 rad) (θ = 0.01 rad)
PEER Design Comparison of Peak Axial Compression in Corner Columns
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