Architectural Engineering PE

This is the most fundamental beam deflection equation on the PE exam. Memorize it and remember that it only applies to simply supported beams with uniform loads. Always check units carefully - mixing kips, feet, ksi, and in⁴ will give deflection in inches. For cantilevers or point loads, different equations apply.

Fan laws assume geometric and dynamic similarity - same fan operating at different speeds. Power increases with cube of speed ratio, so small speed increases dramatically increase power consumption. Always verify motor capacity and electrical requirements when increasing speed.

This is the fundamental equation for building envelope thermal analysis. Always verify that ΔT is calculated as inside minus outside temperature. For cooling loads, use outdoor minus indoor temperature. U-values are often given in problem statements or can be found in ASHRAE tables.

The coefficient of utilization (CU) must be looked up from manufacturer tables based on room cavity ratio and surface reflectances. Light loss factor (LLF) accounts for lamp depreciation, dirt accumulation, and maintenance - typical values range 0.75-0.90. Always round up the number of fixtures to the nearest whole number.

Always use nameplate wattage, not lamp wattage - include ballast losses for fluorescent fixtures. Exclude exit signs and emergency lighting from calculations unless specified. Double-check unit consistency (W/ft² vs W/m²).