Chapter 12: Structural Systems Flashcards
Describe a steel beam-and-girder structural system.
Large members, called girders, span between columns and smaller beams are framed into them. The girders span shorter distances because they carry the weight of the beams. The beams span longer distances and are framed into the girders. Typical spans are 25-40’.
The steel framing is usually covered with steel decking, which spans between the beams with a concrete slab poured over it.
This type of construction is commonly found in mid- to high-rise office buildings.
Describe an open-web steel joist system.
Joist span between beams or bearing walls. Joists can span 20-144’. Joists are typically spaced 2-6’ apart. Topped with steel decking and a concrete slab. Typically seen in one-story or low-rise buildings with wide column spacing.
Mechanical can be run through the webbed joists easily and suspended systems can be hung off them.
What does it mean when concrete is post-tensioned?
Steel cables within the concrete are tightened after the concrete sets, creating extra compression forces in the beam or slab. Slab should not be penetrated for pipes or conduit. Used in long span structures.
Describe a concrete beam-and-girder system.
Functions in a manner similar to a steel system in which the slab is supported by intermediate beams, which are carried by larger girders. Spans 15-30’. Among easiest of cast-in-place concrete systems to penetrate for piping.
Describe concrete joist system.
Comprised of concrete members spaced 24” or 36” apart, running in one direction, which frame into larger beams. More difficult to drill holes for small pipes and conduit.
Describe flat plate concrete construction.
The floor slab is designed and reinforced to transfer loads directly to the columns, which generally do not exceed 25’. Commonly used in situations where floor-to-floor height must be kept to a minimum. Difficult to drill for electrical service or small pipes.
Describe flat slab concrete construction.
Similar to flat plate except that drop panels (increased slab thickness around the columns) are used to increase strength.
Describe waffle slab system concrete construction.
Can provide support for heavier loads at slightly longer spans than the flat slab system. Waffle slabs are often left exposed, with lighting integrated into the coffers.
Why are single- and double-tee members a popular form of pre-cast construction?
They can simultaneously serve as beam and floor decking and are easy and fast to erect.
What’s the most common form of masonry construction?
Concrete block, also known as concrete masonry units (CMUs). Most common size is 8”x8”x16”
Two open cells on either side of an intermediate rib that can be left open or filled with grout if more strength is needed.
What’s the only way load-bearing walls can be modified?
Can only be pierced for doors and other openings if the top of the opening is framed with an adequately engineered lintel or beam.
What walls in a residential home are load-bearing?
Exterior walls are usually loadbearing (particularly first story) and some interior partitions.
What walls commercial construction are loadbearing?
Fewer loadbearing walls are used than in residential construction; most structures are some form of column-and-beam system with nonloadbearing infill. The core walls of high-rise buildings are nearly always structural and cannot be pierced except for small openings for pipes.
What are dead loads?
The vertical loads due to the weight of the building and any permanent equipment. The only time an interior designer needs to consult a structural engineer relative to dead loading is if plans call for the installation of unusually heavy partitioning (such as a masonry wall) or heavy equipment.
What are live loads?
Includes the weight of people, furniture, and other movable equipment. If a space is being designed for a use other than its original purpose and the floor loading will be increased, the designer should consult with a structural engineer. The structural bays near the center of the building are designed for heavier loading, so file rooms and book stacks should be located in the ares in the early planning stages.
