Building Systems and Structural Integration
This domain tests whether the architecture can actually hold up and be serviced: load path, structural depth, bay coordination, and the space mechanical, electrical, and plumbing systems need.
Core rules
- Trace the load path. Gravity loads move from slab to beam to girder to column to foundation; lateral loads move through diaphrams to shear walls, braced frames, or moment frames. Every transfer, cantilever, and discontinuity is a cost and coordination risk.
- Depth rules of thumb. Steel beam depth ≈ span ÷ 20; concrete beam ≈ span ÷ 12 to ÷ 15; concrete one-way slab ≈ span ÷ 24 to ÷ 28. Repetitive wood joists at 16 in. on center are commonly about span in feet matches depth in inches.
- Serviceability governs often. Floor deflection limits are typically L/360 for live load and L/240 for total load; roofs are looser. Vibration governs long-span floors, labs, and gyms.
- Reserve the plenum. Structure plus ducts, sprinkler, lights, and ceiling need room: a 13 ft floor-to-floor with a 30 in. structural zone and a 9 ft ceiling leaves about 18–24 in. for services - enough for ducts only if the layout is disciplined.
- Movement and coordination. Expansion joints, seismic separations, and long-span thermal movement must be shown on plan and carried through cladding, ceilings, and MEP.
Worked example
A 30 ft steel bay: 30 × 12 ÷ 20 = 18 in. beam depth. With a 3 in. deck and a 2 ft ceiling plenum plus 9 ft ceiling, structural zone plus services equals about 18 + 3 + 24 in. = 45 in., needing a floor-to-floor of at least 12.5–13 ft. If the client insists on 12 ft, either the beams deepen the problem or the mechanical layout must use a different distribution strategy.
Traps
- Assuming a column-free bay is free; long spans drive depth and cost quickly.
- Forgetting that lateral systems need wall or frame lines that also block program space.
- Coordinating duct mains but not branch ducts, sprinkler mains, and structural penetrations.
- Placing expansion joints on architectural drawings but not following them through the envelope and services.