EXHIBIT 7C FAA ATCT STRUCTURAL DESIGN STATEMENT OF WORK

Transcription

1 RFP No EXHIBIT 7C FAA ATCT STRUCTURAL DESIGN STATEMENT OF WORK EXHIBIT 7C Page 1 of 1

2 1. STRUCTURAL DESIGN DOCUMENTS - The A/E shall incorporate the following major structural design documents: 1.1. International Building Code (IBC), 2006 Edition ASCE 7-05 Standard Minimum Design Loads for Building and Other Structures, 2005 Edition and Addendum FAA Terminal Facilities Standard Designs A/E Project Manual, FY09 Edition Applicable City of San Francisco Building Code Requirements for High-Rise Structures, including Administrative Bulletin No. AB Applicable State of California Building Standards Commission Regulations for High-Rise Structures. 2. STRUCTURAL DESIGN ELEMENTS - The occupancy category for this structure shall be designated IV, an essential facility. Use a seismic importance factor of I = 1.5. The importance factor for wind forces shall be I = 1.15 as listed in ASCE 7-05, Table 6-1. Earthquake design shall be in accordance with the codes listed above and in accordance with recommendations of the geotechnical engineers. Strength design (LRFD) shall be used for the design of all components of the superstructure including non structural components as defined in Paragraph "Specific Structural Design Requirements" of this document. The design of the piled foundation system shall be performed using allowable stress design except that the reinforced concrete components that are part of the overall foundation system will be permitted to be designed using strength design Foundation design requirements and code items include: Foundation design requirements shall be provided to the structural designers from a geotechnical firm familiar with the requirements of the construction site geology. Preferably the geotechnical consultants shall be located in a city close to the project site. A piled foundation system is to be used for the tower support. A mat or raft foundation directly bearing on the sub grade is not to be considered an alternate solution. The selected foundation pile system must have individual piles that are have either a round or octagonal cross sectional properties At the recommendation of the geotechnical engineers a site specific response spectrum may be provided for the seismic dynamic analysis of the tower structure. If a specific spectrum is provided a probabilistic analysis shall be use for the development of that response spectrum and the magnitude of the spectral response accelerations will be based on the assumption of the tower being located directly above the nearest known active fault line The finite element computer model of the tower shall include the elements associated with the foundations and the geotechnical engineer must provide the structural engineer the following soil design parameters: Estimated long term vertical settlement of the recommended foundation system June 21, 2010 Page 1 of 4

3 A graphical plot of the passive soil resistance coefficient on the vertical face of the foundation for the soil reacting against the foundation plotted against horizontal deflection of the foundation. Values of the vertical and horizontal subgrade modulus and a diagram of the values of the horizontal subgrade modulus along the vertical length of the pile at 5 feet intervals. Due consideration in the selection of the piling system to mitigate the impact of construction noise in the vicinity of the tower The selected framing system must provide a connection of the tower shaft to the foundation that provides the full fixity condition for the shaft at its base and also transfers the superstructure tension forces from wind or seismic loading to the foundation system. This requirement shall apply to any tower shaft construction system selected The vertical seismic component (upward or downward) shall be included and provide additional load combinations when Sds is greater than This is a modification of paragraph in ASCE Structural design requirements Only two systems of shaft construction will be permitted for the tower: Steel columns with special steel concentrically braced frames up to the base of the cab structure. Concrete shear wall construction. A combination of these two systems is permissible. A change in framing system may be selected at some specific elevation on the tower shaft. That is the upper stories of the tower may be braced frames built on the lower concrete shear walls The control cab framing must be designed to include torsional seismic loading. Paragraph of ASCE 7-05 provides the proper reference. The seismic loading of the control cab must include the lateral forces generated by the combination of seismic loads in two orthogonal directions Deflection Limits For horizontal deflection under wind (drift limitation), the maximum permissible deflection shall be x height For horizontal deflection under MCE designs Earthquake (drift limitation), the maximum permissible deflection shall be x height (in the inelastic range) Both of the above mentioned (2.3.1 & 2.3.2) limiting deflection criteria have to be met in the final structural design of the Control Tower The maximum calculated inelastic drift shall be determined from the product of the maximum calculated deflection from the dynamic seismic analysis multiplied deflection amplitude factor C D divided by the importance factor I of The Control Cab maximum inter-story drift is also to be limited to cab height from cab floor to ceiling multiplied by An additional critical issue related to the overall tower deflection and cab inter-story drift during an earthquake is that those parameters must be June 21, 2010 Page 2 of 4

4 limited to a value that allows continuous operation of air traffic services during the MCE seismic event Non structural design components Definition - All equipment located in the tower and their associated support systems and including the cab glass is defined as non structural components Attachment of all these items to the tower structure shall be designed using the requirements of ASCE 7-05 Chapter 13. The value of the component amplification factor may be adjusted by the structural engineer to allow for the magnification effects of the cab acceleration during a Maximum Considered Earthquake (MCE) seismic event so as to ensure operational levels are maintained after the earthquake. The provisions of Chapter 13 shall apply but not limited the cab glass design and support of the control cab glazing panels All electronic equipment must stay in operation during the MCE seismic event and the cab glass must remain intact and must not be dislodged from the cab window support framing The cab window glass and framing shall be sub contracted to those manufacturers who specializes in cab glass design fabrication and also to the manufacturer for the cab glass support framing system. The design of the cab glass and framing system must be performed by a structural engineer experienced in the design and installation of airport traffic control tower cab glass. 3. WIND TUNNEL TESTING - Arrange wind tunnel testing for the project. In conjunction with professional wind engineering consultants, model the subject ATCT, base building, and surrounding development in accordance with current wind engineering testing criteria. Conduct high frequency balance testing The intent of wind tunnel modeling is to: Optimize the project design Determine cladding pressures that will assist with the optimization of the project structural system Identify adverse wind exposures caused by the design, including the wind conditions causing the following effects on the tower: Maximum drift of tower cab level specifically at the cab roof. Wind conditions causing tower resonant oscillations under steady stream wind or gust conditions. Determination of the stability of the tower under conditions causing wind eddies to be shed from opposite corners of the tower walls. (The Strouhal Effect) Reduce Construction Costs It is a requirement of the final design of the Airport Traffic Control Tower that the structure shall be scale modeled and tested in a wind tunnel under simulated scaled wind loading conditions. June 21, 2010 Page 3 of 4

5 3.3. Use the current edition ASCE 7, "Minimum Design Loads for Buildings and Other Structures." Test model structural loads and exterior cladding loads shall be recorded and utilized in the design. The A/E shall incorporate wind test data into the loading scenario, as allowable by the appropriate code(s), to produce a more efficient and cost saving design Design Comparison - The A/E shall provide a written report identifying any design and/or construction cost savings based upon use of the specific wind load conditions in lieu of conservative, model building code loads for the project. This report is due at the final design submission A list of wind engineering consultants used on previous projects by the FAA is available upon request. 4. BLAST ANALYSYS Blast analysis shall be an inherent part of the design At the 35 percent design phase and at approximately the 70 percent design stage, the blast analysis for the ATCT and base building buildings and site design shall be conducted. Based upon recommendations and findings of the two blast analyses, a fee proposal for any design changes may become necessary. Upon fee settlement, the A/E shall make appropriate changes, which include, but may not necessarily be limited to; altering structural connections, changing cladding, and hardening of the structure The cab window glass shall be laminated to ensure that the glass remains intact and in place during a design blast event End of Structural Engineering Statement of Work June 21, 2010 Page 4 of 4