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LecturesModule 20

Capstone Design Project

Design a small steel-framed building bay end-to-end.

AISC Reference Box
  • AISC 360-22 — Specification chapter governing this topic
  • AISC Manual 16th Ed. — Design tables and worked examples

Lecture Notes

This module introduces capstone design project. Lecture content here covers the governing physics, LRFD philosophy, and how the relevant AISC 360-22 chapter organizes the limit states.

Instructors can replace this text in Admin Mode. Each section is structured around: (1) behavior, (2) failure modes, (3) AISC limit-state equations, (4) design workflow, (5) detailing requirements.

A short comparison to ASD is included only where the resistance factor / safety factor relationship clarifies the LRFD design check.

4-story steel office, 5 bays × 30 ft, perimeter CBFcomposite floor • interior gravity columns • CBF lateral
Capstone: typical 4-story steel office, 5 × 30 ft bays with composite floor and perimeter braced frames.

Formula Sheet

NameEquationAISC Ref
Design strengthφ Rn ≥ RuAISC 360-22 B3.1

Worked Example

Capstone Design Project

Given
Replace with project-specific given data (loads, geometry, material).
Load combination
Controlling LRFD load combination from ASCE 7.
Required strength
Compute required strength Ru from the controlling combination.
Limit states
  • Limit state 1
  • Limit state 2
AISC reference
AISC 360-22 — applicable chapter
Solution steps
  1. 1. Required strength
    Compute Ru.
  2. 2. Trial section
    Pick a trial from AISC shape tables Instructor should verify with official AISC Manual.
  3. 3. Check each limit state
    Apply φ Rn ≥ Ru for every governing limit state.
  4. 4. Iterate
    Resize until the most economical section satisfies all checks.
Final design decision
Select the lightest section that satisfies all LRFD limit states.
Common mistakes in this example
  • Skipping a limit state
  • Using the wrong φ factor
  • Forgetting serviceability checks

FE-Style Worked Examples (7)

Each example mirrors the NCEES FE Civil Reference Handbook style: brief givens, a labeled figure, AISC section reference, step-by-step numeric solution, and a single boxed answer.

Given
Single bay 30×30 ft, office: D=80 psf, L=100 psf (reducible).
AISC Reference
ASCE 7 §4
Step-by-step solution
  1. wu (infill)
    (1.2×80 + 1.6×100) × 10 ft / 1000 = 2.56 k/ft
Answer Infill beam wu = 2.56 k/ft.
VConcentrically braced frame bay

Practice Problems

  1. [E] State the six deliverables of a capstone steel-building design.
  2. [E] Identify governing code package for U.S. commercial bldg (IBC + ASCE 7 + AISC 360 + AISC 341).
  3. [E] List design steps in order for a typical bay.
  4. [E] Sketch a typical office plan with framed bays and lateral system.
  5. [E] Define occupancy category and seismic design category.
  6. [M] Tributary loads on an interior column of a 4-story office (90 DL, 50 LL, 30 x 30 bay).
  7. [M] Pick a typical composite floor beam: 30 ft, 10 ft o.c., 100 psf service.
  8. [M] Pick the lightest W14 column for Pu = 720 k, KL = 14 ft.
  9. [M] Estimate base shear by ASCE 7 ELF for a 60 ft steel braced-frame office, Ss = 1.0, S1 = 0.40.
  10. [M] Recommend a brace configuration (X, K, chevron, EBF) and justify.
  11. [H] Capstone deliverable: design a typical floor (beam + girder + column) of a 4-story office bay including a perimeter braced frame.
  12. [H] Lateral design: develop seismic base shear, story shears, OTM; size the first-story brace.
  13. [H] Connection package: four representative connections (shear tab, girder-to-column shear tab, brace gusset, base plate).
  14. [H] Draft a CD set: framing plan, brace elevations, typical details, beam/column schedule, base-plate schedule.
  15. [H] Engineer's narrative: assumptions, governing load cases, software inputs, deviations from prescriptive AISC rules.
Structured Clues
  • Document every load combination considered — even if not controlling.
  • Provide one summary table per member type (Mu, φMn, ratio).
  • Always present BOTH a strength check and a serviceability check.
Code References
  • AISC 360-22 (full)
  • ASCE 7-22 (full)
  • AISC Manual Parts 2–18

Quiz

1. Which AISC 360-22 chapter primarily governs capstone design project?
2. In LRFD, the basic design inequality is:

Common Student Mistakes

  • Mixing ASD and LRFD load combinations in the same problem.
  • Using nominal strength Rn instead of design strength φRn.
  • Forgetting to check every limit state listed in the AISC chapter.

"Professor Explains" Script

Today we're talking about capstone design project. Think of this topic as one step in the LRFD workflow: identify the demand, identify the limit states from the relevant AISC chapter, then check that φ·Rn is at least equal to Ru. We'll walk through the failure modes, the equations, and a worked example. Pay close attention to where the resistance factor changes — that's where students lose points on exams.