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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 • nil MN INN 1111111 SW MN ETABS no aim Imo — 'um im 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 a ETABS III•. ii.�III ti /11 it 11 a a Ysrael A. Seinuk PC Submitted into the public record in connection with item PZ.1 on 02-28-08 Priscilla A. Thompson City Clerk -821. -695. -568. -442. -316. -189. -63. 63. • 189. 316. 442. 568. 695. 821. 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