Structures and Structural Systems
Structures and Structural Systems tests whether you can follow load from roof to foundation and apply the Florida Building Code and ASCE 7 load provisions. In Florida, wind uplift and flood elevation govern far more designs than seismic, but the exam still expects correct load combinations and lateral-system vocabulary.
Loads and combinations
- Dead, live, wind, flood, and soil loads; rain and construction loads matter too.
- Strength combinations to know cold: 1.2D + 1.6L for gravity, and 0.9D + 1.0W for wind, where the reduced dead load is what exposes uplift.
- ASD versus LRFD: never mix an allowable-stress wind pressure with strength-level combinations.
Wind
- The FBC wind maps derive from ASCE 7 ultimate design speeds; HVHZ values for Risk Category II approach 175 mph, while interior Florida is far lower.
- Exposure B, C, or D depends on surface roughness; enclosure classification (enclosed, partially enclosed, open) sets internal pressure, and a partially enclosed building can nearly double the inward/outward demand.
- Components and cladding use GCp; the main wind-force-resisting system uses different coefficients. Do not swap them.
- Continuous load path is the theme: roof sheathing to truss, truss to wall, wall to floor, floor to foundation, using straps, clips, anchor bolts, and holdowns matched to the design.
Flood
FBC 1612 and ASCE 24 set the lowest floor relative to base flood elevation, freeboard, flood openings, and elevation certificates.
Lateral systems
Shear walls and diaphragms, moment frames, and braced frames; masonry and cast-in-place concrete are common in Florida mid-rise work, wood shear walls in residential.
Worked example
A roof assembly has dead load 15 psf and design wind uplift of 40 psf (suction). Gravity: 1.2(15) + 1.6(20 live) = 50 psf downward, used to size sheathing and rafters. Uplift: 0.9(15) - 40 = 13.5 - 40 = -26.5 psf net, meaning the connection must resist 26.5 psf of pull-out. The member is governed by gravity, but the connection is governed by uplift - a classic exam distinction.
Traps that cost marks
- Designing connections with 1.2D + 1.6L and ignoring the 0.9D + 1.0W case.
- Using main-wind-force-resisting coefficients for roof panels.
- Treating a partially enclosed building as enclosed, understating internal pressure.
- Assuming flood vents are unnecessary because the wall is concrete.
- Missing a link in the load path, such as unstrapped trusses on a strapped wall.