The structural design for new CPS buildings shall comply with all of the requirements prescribed in CBC.
5.4.1 Design Methodologies
The structural design shall be based on the intended long term life expectancy and use requirements for CPS buildings. CPS buildings are typically designed as educational spaces with supporting office and athletic spaces.
Floor Structure Design: Structural designs with skewed floor structures shall be avoided when possible. The skewed design typically complicates the framing design and escalates the project costs. Similarly, large cantilevered floor structures shall be avoided because they complicate the design and increase costs.
Wall Design: Tall cantilever walls shall be carefully evaluated for deflection and serviceability requirements. Bracing required at cantilevered walls may present long term serviceability issues due to corrosion and thermal movement at exposed bracing members. Sloped walls where the top of the wall extends beyond the base shall be avoided. Walls constructed with a slope are difficult to maintain and may fail without warning.
5.4.2 Structural Systems and Elements
CPS buildings are generally comprised of structural steel framing. Masonry bearing walls comprised of Concrete Masonry Units (CMU) are often used at elevator shafts and stair towers.
Floor structures are generally constructed with normal concrete on composite metal deck. Composite steel framing can be used at the discretion of the structural engineer of record. Roof structures are generally constructed of metal deck on steel beams or joists. Truss girders are typically used for long-span applications above assembly spaces.
The lateral system design shall be informed by the architectural arrangement of the building. Steel moment or braced frames are typically used on CPS buildings. Braced frames are preferred for their lower cost and higher stiffness. Moment frames shall be used when the architectural arrangement of the building does not permit for the installation of steel braced frames. The CMU towers shall be considered as a part of the lateral design system at the discretion of the structural engineer of record.
5.4.3 Structural Alterations
Structural alterations shall be designed to the new construction standards, being mindful of the archaic nature of the construction of most existing CPS buildings. The collateral effects of alterations on the existing structures shall be considered, with a particular emphasis on snow drifting.
5.4.4 Seismic
Seismic design for CPS buildings shall comply with all requirements of the CBC. Chicago is not in a region of high seismic activity, but the seismic load shall be evaluated per the requirements of the CBC to determine if it is the controlling lateral system design load.
5.4.5 Equipment and Fixtures
The proposed mechanical equipment and architectural fixtures shall be coordinated with the structural design. The structural design shall be coordinated with the mechanical equipment loads to determine the appropriate framing. Concrete pads shall be considered at roof mounted mechanical equipment above educational spaces to reduce the noise transmission to the below space.
Fixture locations shall be coordinated with the architectural design to ensure they are considered in the structural design. The fixture type shall be reviewed to determine if there are specific structural requirements for the installation. For example, movable partitions are a typical architectural fixture with specific deflection requirements that need to be coordinated with the structural design.
5.4.6 Security and Safety
Structural design shall consider the robustness required for public building. At entrances near intersections or substantial plazas, vehicle restricting bollards shall be provided.