HomeMy WebLinkAboutSubmittal-LERALERA
SUBMITTED INTO THE
Leslie E. Roberti on Associates, R.L.L.P.
Consulting Structural Engineers PUBLIC RECORD FO R
ITEM zi ON )0 j08 ,
2 November 2005
File: P370
lMaalee Development Corporation
429 Lenox Avenue
Miami Beach, Florida 33139 c/o Ysrael A. Seinuk P.C.
Via e—mail: ysrael@yaseinuk.com
330 Biscayne Boulevard, Miami
Conceptual Structural Design
30 Broad Street, 47th Floor
New York, NY 10004-2304
Tel: (212) 750-9000
Fax: (212) 750-9002
http://wwwlera.com
William J. Pa -set -Ian
Partner
wjft?a lera.com
Dear Sirs:
We write to confirm that we have reviewed the conceptual
structural design for the 330 Biscayne Boulevard project,
and generally, we concur with the design.
We reviewed structural concept sketches, a preliminary
computer analysis and a summary description of the basic
structural systems and its wind loading performance
characteristics, all as provided by the, office of Ysrael A.
Seinuk P.C. The purpose of our initial review was to form
an independent opinion concerning the general
appropriateness and adequacy of the structural design
concept.
While the available information is of a conceptual nature
only and is subject to development, we believe that the
design concept is appropriate for the project and we expect
that the structural systems envisioned in the conceptual
sketches may be developed to provide adequate structural
performance for the project.
We look forward to working with you in the development of
the design for this landmark project.
Regards,
LESLIE E. }2OBERTSON ASSOCIATES, R.L.L.P.
William
WJF/pi
J.
Faschan
A Registered Limited Liability Partnership
1
LERA
' Leslie E. Robetison Associates, R.LLP.
Consulting Structural Engineers
11
' 2 November 2005
30 Broad Street, 47th Floor
New York, NY 10004-2304
Tel: (212) 750-9000
Fax: (212) 750-9002
http://www.lera.com
William J. Faschan
Partnex
wjf(7a lera.com
File: P370
11 Maclee Development Corporation
429 Lenox Avenue
Miami Beach, Florida 33139 c/o Ysrael A. Seinuk P.C.
Via e—mail: ysrael@yaseinuk.com
330 Biscayne Boulevard, Miami
Conceptual Structural Design
Dear Sirs:
We write to confirm that we have reviewed the conceptual
structural design for the 330 Biscayne Boulevard project,
and generally, we concur with the design.
We reviewed structural concept sketches, a preliminary
computer analysis and a summary description of the basic
structural systems and its wind loading performance
characteristics, all as provided by the office of Ysrael A.
Seinuk P.C. The purpose of our initial review was to form
an independent opinion concerning the general
appropriateness and adequacy of the structural design
concept.
While the available information is of a conceptual nature
only and is subject to development, we believe that the
design concept is appropriate for the project and we expect
that the structural systems envisioned in the conceptual
sketches may be developed to provide adequate structural
performance for the project.
We look forward to working with you in the development of
the design for this landmark project.
Regards,
LESLIE E. OBERTSON ASSOCIATES, R.L.L.P.
William J.
WJF/pi
Faschan
Submitted into the public
record in connection with
item PZ.1 on 02-28-08
Priscilla A. Thompson
City Clerk
A Registered Limited Liability Partnership
-1
I
EMPIRE WORLD TOWERS
330 Biscayne Boulevard, Miami
1. General Information
The Empire World Towers consist of two 106-story main towers
perpendicular to each other in plan. They are connected by a podium from the
ground level to the 21 S` (Lanai) level. The West Tower is 290 ft in the north -
south direction and the East Tower is 450 feet in east -west direction.
From a structural point of view, the two towers are disconnected from
the ground level to the 21st level. An expansion joint shall be placed between
them, and since they are technically separated, they shall be investigated as two
individual towers. It may also be noted that bridges may connect the two towers
in order to provide accesses especially in case of emergencies. The bridges will
be designed to accommodate the different deformation characteristics of the
towers (temperature change, creep and shrinkage of concrete, etc.)
Because of the similarity (height, dimension and layout) of the lateral
resisting systems of the East tower and the West tower, the structural analysis
focused on the East tower. It is assumed that winds could approach the tower
from any direction without any effect from the West tower. In fact, the West
tower may actually reduce the wind loads to the East tower when the wind
approaches from the north-west side.
A finite element analysis model was setup to investigate static and
dynamic properties of the east tower, using ETABS software. Twenty four
ASCE7-2002 specified wind load cases are considered in the structural
analysis. Some important parameters used in the analysis are shown in Table 1.
Table 1: Analysis Parameters
Building Height'
1210'-10"
Area/Floor (Typical)
22785 ft2
Wind Exposure Category
D
Basic Wind Speed
146 mph
Note: Basic Wind Speed is defined as a nominal design 3-second gust wind speed
in miles per hour at 33 ft (10 m) above ground for Exposure C category. The mean hourly
wind speed at roof level is approximately 256ft/second.
' Building height=1200'-00" above grade and 10'-10" basement.
1
Submitted into the public
record in connection with
item PZ.1 on 02-28-08
Priscilla A. Thompson
City Clerk
1
' 2. Analysis model
i
1
a
i
In the finite element analysis model, the 10" post -tensioned slabs were
modeled as membrane elements and the shear walls, as shear elements. Figure
1 shows the shear wall and column layout of typical floor. The thickness of the
wall at grid line D, E and F varies from 4 feet to 2 feet. The area of the hammer
heads at grid line D, E and F are 144 ft2, 156 ft2 and 144 ft2, respectively. There
are four belts connecting these hammer heads with the adjacent columns. These
belts are located at the 23`d, 50`h 78th and Roof levels as shown in Figure 2.
High strength concrete is used to increase the stiffnesses of the buildings. The
cylinder compressive strength of the concrete shear walls is 12 ksi from
basement to 69th level, and 10 ksi from 70th level to roof level.
Twelve reversible wind load cases (total of 24 load cases), as shown in
Table 2 are considered in the structural analysis. An importance factor of 1.15
is used to calculate the wind loads.
Table 2: WIND LOAD CASES
Wind
Load
Wind load description
1
1.0WX
2
1.0WY
3
0.75 WX+0.75 WY
4
0.75 WX-0.75 WY
5
0.75WX+0.75WTX
6
0.75 WX-0.75 WTX
7
0.75WY+0.75WTY
8
0.75WY-0.75WTY
9
0.563 WX+0.563 WTX-0.563 WY-0.563 WTY
10
0.563 WX+0.563 WTX-0.563 WY+0.563 WTY
11
0.563 WX-0.563WTX+0.563 WY+0.563 WTY
12
0.563 WX-0.563 WTX-0.563 WY+0.563 WTY
Where: WX is wind approaching the building in the east -west direction; WY is
wind approaching the building in the north -south direction; WTX and WTY are
wind WX and WY approaching the building with 15% eccentricity.
It is noted that in the ASCE 7-2002 analysis procedure, the wind loads
are based on wind with a 500-year return period. The Empire World Towers are
Submitted into the public
record in connection with
item PZ.1 on 02-28-08
Priscilla A. Thompson
City Clerk
2
located in a high hurricane area and will be one of the tallest buildings in the
world. To be conservative (before wind tunnel laboratory tests are done), the
ASCE code -specified wind loads have been increased by 10% in the north -
south direction.
3. Analysis Results
a) Deflection and Story Drift
By using the wind loads described above, and considering the P-S effect
in the analysis model, the roof displacement and the story drift of the East
tower are shown in Table 3.
Table 3 Displacement
Roof Displacement
North -south direction
28.2 in
H1515
East-West direction
20.3 in
H1715
Story Drift
North -South direction
h/375
East-West direction
h/584
Where: H is the height of the building, e.g. H=1210'-10 "; h is the story height
Although it is not directly specified in ASCE 7 or the 2002 ACI code,
some codes such as the National building Code of Canada limit the maximum
lateral deflection or the inter -story drift. The maximum lateral deflection for tall
buildings is limited to be H1500 and the inter -story drift is limited to h/350, if
the P-S effect is considered in the analysis.
b) Dynamic property
The first 3 natural periods and mode shapes of the east tower are shown
in Table 4. These buildings have good dynamics properties. The first two mode
shapes are translation and the third mode shape is torsion. The maximum static
displacement is in south -north direction while the potential dynamic
displacement is most likely to be in east -west direction.
Table 4 Natural period and Mode Shape
Mode
Period
(Seconds)
Mode Shape
1 st Mode
7.23
East-West Translation
2nd Mode
6.44
North -south Translation
3rd Mode
4.48
Torsion
3
Submitted into the public
record in connection with
item PZ.1 on 02-28-08
Priscilla A. Thompson
City Clerk
c) Strength Design
Figure 4 shows the critical tensile stress distribution of the shear wall at
Grid Line D. It is observed that only a small portion of the shear wall has the
tensile strength exceeding its rupture strength, which is 821 psi for concrete
with a cylinder compressive strength of 12 ksi. This indicates:
i) Shear walls will perform within established parameters.
ii) The tensile forces in the shear wall are relatively small in service
condition. The uplift forces are low and the foundation is
basically in compression.
4. Conclusions
Based on our structural analysis, we conclude:
a) The Empire World Towers with a height of 1200 ft are structurally
feasible, in a high hurricane area.
b) Lateral displacements of the building are H/515 in the north -south
direction and H/715 in east -west direction, which is less than the
limitation of H/500. The inter -story drift of the building in both
directions are less than h/350, even with a 10% wind load increase in the
north -south direction, (making the structural analysis to be on the
conservative side before a more accurate prediction of the wind loads
through wind tunnel laboratory test can be done).
c) The Empire World Towers have good dynamic properties (natural period
and mode shape). It is predicted that the dynamic motions of the towers
will be satisfactory in accelerations and occupant comfort criteria. This
will be verified by the wind tunnel laboratory test. Nevertheless,
excessive acceleration could be technically mitigated by the installation
of a Tuned Mass Damper or Hydraulic Damper devices at Roof level or
the 78`11 floor level (Mechanical Floor).
d) The lateral system of the Empire World Towers is very efficient. The
shear walls at Grid line D and F form a pair of "flanges" that make it
very efficient to resist the lateral loads in east -west direction. Four belts
connecting the hammer heads and adjacent columns increase the lateral
stiffness in north -south direction. Meanwhile, the number of gravity
columns is reduced by the use of 10" post -tensioned slab. Most of the
4
Submitted into the public
record in connection with
item PZ.1 on 02-28-08
Priscilla A. Thompson
City Clerk
gravity loads are introduced to the shear walls instead of columns. As a
result, the tensile forces in the foundation and shear walls are relatively
small. Design of the shear walls and foundation will be very economical
since they are basically in compression.
In summary, the proposed Empire World Towers is structurally feasible.
The gravity and the lateral systems considered in the study are very efficient.
5
Submitted into the public
record in connection with
item PZ.1 on 02-28-08
Priscilla A. Thompson
City Clerk
0
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ETABS
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Ysrael A. Seinuk PC
1BS v8.5.4 - File: EMPIRE WORLD TOWER 3A8 - October 31,2005 17:18
n View - STORY48 - Elevation 6348 - Kip -In Units
ETABS
Ysrael A. Seinuk PC
ETABS v8.5.4 - File: EMPIRE WORLD TOWER 3A_8 - October 31,2005 19:09
3-D View - Kip -in Units
Submitted into the public
record in connection with
item PZ.1 on 02-28-08
Priscilla A. Thompson
City Clerk
ETABS
Yareel A Saint* PC
um
ETABS ',BSA - File: EMPIRE WORLD TOWER Skil November 1,2005 8:48
E/evation View - F -Kp.n Units
Submitted into the public
record in connection with
item PZ.1 on 02-28-08
Priscilla A. Thompson
City Clerk
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Ysrael A. Seinuk PC
Submitted into the public
record in connection with
item PZ.1 on 02-28-08
Priscilla A. Thompson
City Clerk
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ETABS v8.5.4 - File: EMPIRE WORLD TOWER 3A_8 - November 1,2005 11:42
Elevation View - D Stress S22 Diagram (ADW04) - lb -in Units