EXISTING STRUCTURE
NY TIMES BUILDING
Saba Sheikh
Professor G. Schierle
Renzo Piano Building Workshop, Genoa Italy FXFOWLE Architects, NY Thorton Tomasetti, NY 2007
Aireen Batungbakal
ARC 613 SPRING 2011 -
SITE
SEISMIC FACTORS SOIL CLASS SDC B, C – Moderate Seismic Risk Seismic Design Categories HARD ROCK SDC A – Low Seismic Risk SDC B, C – Moderate Seismic Risk SDC D – High Seismic Risk SOFT SOIL York State SDC E, F – High Seismic Risk Will not apply in New York
SITE / TERRAIN CONDITIONS RELATIVELY SLOPED In lower Manhattan bedrok is rarely near the surface, (NEHRP site classification).
CLASS B Sediments are moderately deep and soft because they are predominantly of post-glacial Holocene and estuarine origin (organic clays, salts, and find sand) Source:
NEHRP Soil Classifications by Census Tract of Lower Manhattan [Jacob, 1999]
Site Loca on
PROGRAM
170 ‘-0” 90 ‘-0”
40 ‘-0”
300’-0”
40 ‘-0”
1,048’ 744’-0”
PERIMETERR
OPEN N
NY Times, section
facade New York Times utilities / mechanical commercial [ tenants] retail green pockets
FREEE
STRUCTURE: BRACING
DIAGONAL ROD AT CANTILEVER BAY X-BRACED ROD (SPADE CONFIGURATION) pretensioned BEAM (CANTILEVER) / HORIZONTAL STRUT EXTERIOR COLUMNS (2)-excluded from fireproofing
STRUCTURE: BRACING
FACADE
The New YYork Times Company’s new world headquarters designed by Renzo Piano features an 800-foot glass curtain wall to provide natural daylight to occupants. Computercontrolled shades respond to the sun’s angle and intensity, y and are fully integrated with the
Detail of the Sun Shading Screen facade that is applied to the building. It is made up of ceramic tubes that control Direct sun exposure.
facade and floor-air ventilation
MULTIFRAME ANALYSIS
LOAD
SHEAR
MOMENT
MOMENT
RE-DESIGN
SUSPENDED HIGH-RISE RATIONALE ATIONALE Prevent vent obstruction of views Enable able original design’s open plan Minimize nimize members and its sizes For instance, small hangers opposed to large posts Facilitates cilitates for future expansion (from top,down) Minimizes nimizes buckling Hangers, replaces compression w/ tension Reduced uses of large members Compression directed on large posts
RE-DESIGN 145’-0”
20’
40’
32.5’
32.5’
40’
COLUMNS
30’
DIAGONAL BRACING
30’
195’ - 0”
30’
OUTRIGGER DIAGONAL BRACING CROSS-BRACING
MEMBER
SIZES
20’
30’
30’
- BEAMS (tapered from 22” to 18”) W21x147
FRAMING PLAN scale: 1/32” = 1’-0”
- GIRDERS
W21x147
- HORIZONTAL STRUTS
W21x147
- 30x30 COLUMNS(8 total)
W30x191
- COLUMNS
W21x147
CHARACTERISTICS Steel braced-frame core of building: 65ft (EW direction), 90 ft (NS direction)
Layout of core:
40 ft spans (EW sides)
1st: 28’–0”
Upper-level and mid-level: Double-story outrigger diagonal braces (from core to perimeter columns), allowing all columns to participate in lateral stiffness
Four corner notches of tower, columns: 30”x30” box columns, Steel Grade 50 or Grade 42 plate
Flange thickness for columns:
FLOOR HEIGHTS
4” @ base, 2”@ top levels
Pre-tensioned steel rods, x-braced systems & outrigger diagonal bracing:
2nd-13th: 14’–0” 14th: 28’–0” 15th-26th: 14’ –0” 27th: 28’–0” 28th-39th: 14’ –0” 40th: 28’-0”
Allow all columns to resist lateral forces
Steel rods, size:
4” diameter @ base 2” diameter @ upper levels
Horizontal strut connects between columns: Resist compression from tensioned rods’ force Depth: 22” , ‘I’-shaped, Flange thickness: 2” @ base &1” @ top
Structural slab:
1-4”
Exposed, Cantilevered beams (E&W faces of the bay): Beams: 22” @ column to 18” at tip
41st-49th: 14’-0” 50th: 28’-0”
REDESIGN
10
12
12
12
CALCULATIONS - part I Assume: Concrete core wall thickness: t= 1’ Suspender cables: 2 ø2 7/8” Guy cables: 2 ø2 7/8” + 2 ø2 1/2” Average wind pressure (90-110mph, exposure B, @ 749’) P (10 floor stack)= qs Ce Cq = (16.4)(1.1)(1.4)= P=25.256 25 psf P (8 floor stack)= qs Ce Cq = (16.4)(1.05)(1.4)= P=24.108 24 psf P (12 floor stack)= qs Ce Cq = (16.4)(1.25)(1.4)= P=28.7 29 psf P (11 floor stack)= qs Ce Cq = (16.4)(1.15)(1.4)= P=26.404 26 psf Beam: Beam: Beam:
R= 0.08(A-150) SHALL NOT EXCEED 40% FOR HORIZONTAL MEMBERS R= 0.08(A-150)=0.08((14’)(30’)-150) R= 22% R= 0.08(A-150)=0.08((14’)(40’)-150) R= 33% MAX. R= 40% Suspender: SHALL NOT EXCEED 60% FOR VERTICAL MEMBERS R= 60% GRAVITY LOADS Steel deck/concrete slab = 60 psf Partitions (req. by code), other = 40 psf DL = 100 psf BEAM LIVE LOAD (100%-22%) = 78%) 0.78(50)
LL=39 psf
SUSPENDER LIVE LOAD 0.40(50) LL=20 psf TOTAL LOADS: [BEAM] 139 psf à100 DL + 39 LL [SUSPENDER] 120 psf à180 DL + 20 LL UNIFORM BEAM LOAD w= (139 psf (14’))/1000 BEAM BENDING M= wL2 /8= 2 klf (1608.3ft2)/8 S= M/Fb= 402 k’ (14’)/22 USE W21X122
w= 1.946 2 klf
M= 402 k’ S= 256 in3 S= 273 in3>256in3
CALCULATIONS - part II SUSPENDER LOAD P= 13(120psf)[182 +18(18+9)/2]/1000
P=885 k
SUSPENDER CROSS SECTION (twin 2 ø2 7/8”, 70% metallic) A= 2 (0.7)(2.875”/2)2 A= 9 in2 SUSPENDER STRESS f= P/A= 885k / 9in2
f= 98 ksi
GRAVITY FORCE (GUY FORCE): 1252 K' GUY FORCE (from vector graph) P= 1252 k GUY CROSS SECTION (2 suspenders + 2-2.5” strands) AREA= 9 in2 + 2 (0.7)(2.5/2)2 A= 15.9 in2 GUY STRESS f= P/A= 1252 k / 15.9 in2 f= 79 ksi OUTRIGGER BEAM Compression (from vector graph) Try w36x 230 AXIAL STRESS f(a)= P/A= 885 k/67.6
P= 885 k A= 67.6 S= 837 in3 f(a)=13.1 ksi
BENDING STRESS f(b)= M/S= 402 k’(12”) / 837 in3
f(b)= 5.8 ksi
BEAM RADIUS OF GYRATION r= (I/A)1 2 = (15,000/67.6)1 2
r= 14.9^11”
SLENDERNESS RATIO (y-direction braced by floor) KL/r= 40’ (12”)/14.9” ) kL/r= 32.21 ALLOWABLE BUCKLING STRESS CHECK COMBINED STRESS (5.8ksi/22)+(13.1/20)
Fa= 20 ksi fb/ Fb + fa/ Fa<=1 =0.91<1
CALCULATIONS - part III OVERTURN MOMENT M(All)= 30psf(40(28+714+42)2 / 2+2(40(714’)(40’+65‘)]/ 1000 = M(11)= 30psf(40(28+154‘+28)2 / 2+2(40(154’)(40’+65‘)]/ 1000 = 65,268k’ M(12)= 30psf(40(28+168’+28)2 / 2+2(40(168’)(40’+65‘)]/ 1000 = 72,442 k’ (x 3) = 282,594 k‘ Define overturn moments M(All), M11 & M12 (by drawing) CORE MOMENT OF INERTIA I (I(outside)- I(inside)- two 6’ doors) I= (B4-b4)/12- Ay2 I= (654-604)/12- 2x6 (32.52)= 39.488 ft4 BENDING STRESS f(b)= MC/I f(b(10))= 65,268k’(32.5’)/39.488 ft4 f(b (12))= 72,442k’(32.5’)/39.488 ft4 f(b(total))= 282,594k’(32.5’)/39.488 ft4
= 53.72 ksf = 59.62 ksf = 232.6 ksf
DEAD LOAD P(12)=13(180psf) ((195x145)-(4(800ft2)) P(10)=11(180psf) ((195x145)-(4(800ft2))
= 58,675,500# = 58,675,500#
DEAD LOAD STRESS f(c)= P/A f(c12)= 58,675,500#/ (2(40+28)168) f(c10)= 58,675,500#/ (2(40+28)140)
= 2,568psi = 3,081psi > 232.6 ksf, no tensile stress
DETAILS DETAILS Anchor connection from core Cable to edge w/ facade rail Separate core for edges
Cable to slab connection
MULTI FRAME
MULTIFRAME ANALYSIS : MOMENT
MULTIFRAME ANALYSIS : LOAD
MULTIFRAME ANALYSIS: SHEAR
MULTIFRAME ANALYSIS : DEFLECTION