Structural Engineering Exam (SE) Lateral Forces (Wind/Earthquake) — Breadth Syllabus

Lateral Forces (Wind/Earthquake) — Breadth syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Lateral Forces (Wind/Earthquake) — Breadth in Structural Engineering Exam (SE), not a summary of it.

1. 1

   Wind Load Determination (ASCE 7)

   4 topics

   • Wind Speed, Exposure, and Site Parameters
     • Basic wind speed maps and risk categories
     • Exposure categories and topographic effects
   • Main Wind Force Resisting System Loads
     • Directional and envelope procedures
     • Gust effect factor and enclosure classification
   • Components and Cladding Pressures
   • Wind on Other Structures and Appurtenances
2. 2

   Seismic Load Determination (ASCE 7)

   5 topics

   • Seismic Ground Motion and Site Effects
     • Spectral acceleration parameters and site class
     • Design response spectrum construction
   • Seismic Design Category and System Selection
     • Risk category, importance factor, and SDC assignment
     • Response modification coefficient R and system limits
   • Equivalent Lateral Force Procedure
     • Base shear, vertical distribution, and story forces
     • Period determination and drift limits
   • Modal Response Spectrum Analysis Concepts
   • Diaphragm, Redundancy, and Overstrength Forces
3. 3

   Lateral Systems and Load Path

   4 topics

   • Lateral Force Resisting System Types
     • Moment frames, braced frames, and shear walls
     • Dual systems and cantilevered column systems
   • Horizontal and Vertical Irregularities
     • Torsional, soft-story, and weak-story irregularities
   • Diaphragms, Chords, and Collectors
     • Rigid vs. flexible diaphragm behavior
     • Drag struts and force transfer to vertical elements
   • Continuous Load Path and Anchorage Concepts
4. 4

   Other Lateral and Dynamic Effects

   4 topics

   • Soil-Structure and Foundation Lateral Behavior
     • Liquefaction and seismic earth pressures
   • Nonstructural Component and Equipment Seismic Forces
   • P-Delta and Stability Under Lateral Loads
   • Flood, Tsunami, and Other Environmental Lateral Loads

Lateral Forces (Wind/Earthquake) — Breadth flashcards for Structural Engineering Exam (SE)

23 of 62 cards from the Lateral Forces (Wind/Earthquake) — Breadth deck — real questions with worked answers.

1. In ASCE 7, what does the basic wind speed $V$ represent and how is it defined?

   $V$ is the 3-second gust wind speed (mph) at 33 ft ($10\text{ m}$) above grade in Exposure C, taken from the strength-design wind speed maps for the relevant Risk Category. It is an ultimate (LRFD-level) speed, so the load factor on wind is $1.0$.

2. Define the three ASCE 7 wind Exposure Categories B, C, and D.

   Exposure B: urban/suburban, wooded, or closely spaced obstructions (lowest wind). Exposure C: open terrain with scattered obstructions $<30$ ft. Exposure D: flat, unobstructed areas and water surfaces (highest wind).

3. What is the velocity pressure equation in ASCE 7, and give the coefficient value (US units)?

   $$q_z = 0.00256\,K_z K_{zt} K_d K_e V^{2}\ (\text{psf})$$ where $V$ is in mph. $K_z$ = velocity pressure exposure coefficient, $K_{zt}$ = topographic factor, $K_d$ = directionality factor, $K_e$ = ground elevation factor.

4. What is the directionality factor $K_d$ for buildings (MWFRS and C&C), and why is it less than 1?

   $K_d = 0.85$ for buildings. It accounts for the reduced probability that the peak wind direction coincides with the building's most unfavorable orientation, and that the worst pressure coefficient acts simultaneously.

5. What is the topographic factor $K_{zt}$ and when does it exceed 1.0?

   $K_{zt} = (1 + K_1 K_2 K_3)^{2}$ accounts for wind speed-up over isolated hills, ridges, and escarpments. It exceeds $1.0$ on the upper half of abrupt topographic features; otherwise $K_{zt}=1.0$.

6. How is the gust-effect factor $G$ treated for rigid vs. flexible structures in ASCE 7?

   For rigid structures (fundamental frequency $n_1 \geq 1\text{ Hz}$), $G = 0.85$ may be used. For flexible structures ($n_1 < 1\text{ Hz}$), the gust-effect factor $G_f$ is computed including resonant response (dynamic amplification).

7. What distinguishes the Main Wind Force Resisting System (MWFRS) from Components and Cladding (C&C)?

   MWFRS receives wind from more than one surface and provides overall building stability (frames, shear walls, diaphragms). C&C are elements that receive wind directly over small tributary areas (cladding, fasteners, purlins, windows) and see higher localized peak pressures.

8. Write the MWFRS design pressure equation (Directional Procedure, enclosed building).

   $$p = q\,G C_p - q_i\,(GC_{pi})$$ where $q$ = velocity pressure at the appropriate height, $G$ = gust factor, $C_p$ = external pressure coefficient, and $(GC_{pi})$ = internal pressure coefficient applied with $q_i$.

9. Write the C&C design pressure equation for an enclosed low-rise building.

   $$p = q_h\big[(GC_p) - (GC_{pi})\big]$$ where $q_h$ = velocity pressure at mean roof height, $(GC_p)$ = combined external C&C coefficient (function of effective wind area and zone), and $(GC_{pi})$ = internal pressure coefficient.

10. What are the internal pressure coefficients $(GC_{pi})$ for enclosed, partially enclosed, and open buildings?

    Enclosed: $(GC_{pi}) = \pm 0.18$. Partially enclosed: $(GC_{pi}) = \pm 0.55$. Open buildings: $(GC_{pi}) = 0.00$. Both signs must be checked.

11. How does effective wind area affect C&C pressures, and why?

    As effective wind area increases, the magnitude of $(GC_p)$ decreases because peak gust pressures are not fully correlated over large areas. Smaller areas (e.g., a single fastener) get the highest pressures.

12. Define the C&C pressure zones on a low-rise roof (Zones 1, 2, 3).

    Zone 1 = interior field of roof (lowest suction), Zone 2 = edges/eaves/ridges (higher suction), Zone 3 = corners (highest suction). Corner and edge zones govern uplift design of roof attachments.

13. What is the minimum design wind pressure for the MWFRS of enclosed/partially enclosed buildings in ASCE 7?

    The wind load on the MWFRS shall not be less than $16\text{ psf}$ on the projected wall area and $8\text{ psf}$ on the projected roof area (applied per ASCE 7 minimum-load provisions).

14. For wind on solid freestanding walls and signs, what is the basic force equation?

    $$F = q_h\,G\,C_f\,A_s$$ where $q_h$ = velocity pressure at height $h$, $G$ = gust factor, $C_f$ = net force coefficient (depends on aspect ratio and clearance ratio), and $A_s$ = gross area of the wall/sign.

15. For wind on a chimney, tank, or other rooftop appurtenance, what equation applies and what governs $C_f$?

    $$F = q_z\,G\,C_f\,A_f$$ $A_f$ = projected area normal to wind. $C_f$ depends on cross-section shape (square, hexagonal, round) and the slenderness/aspect ratio of the structure.

16. What is the across-wind / vortex shedding concern for tall slender stacks under wind?

    Vortex shedding produces alternating across-wind forces; if the shedding frequency approaches the structure's natural frequency (lock-in), resonant oscillations occur. The critical velocity relates via the Strouhal number $St = \dfrac{n\,D}{V}$.

17. Define $S_S$ and $S_1$ in seismic ground motion.

    $S_S$ = mapped MCE$_R$ spectral response acceleration at short period ($0.2\text{ s}$). $S_1$ = mapped MCE$_R$ spectral acceleration at $1\text{-s}$ period. Both are given as fractions of $g$ for Site Class B/C boundary reference conditions.

18. How are the design spectral accelerations $S_{DS}$ and $S_{D1}$ obtained from mapped values?

    First adjust for site: $S_{MS} = F_a S_S$, $S_{M1} = F_v S_1$. Then take two-thirds of MCE: $$S_{DS} = \tfrac{2}{3} S_{MS}, \qquad S_{D1} = \tfrac{2}{3} S_{M1}.$$

19. What are the six site classes (A–F) and what property defines them?

    Defined primarily by average shear-wave velocity $\bar{v}_s$ (or $N$, $s_u$) in the top $100\text{ ft}$: A = hard rock, B = rock, C = very dense soil/soft rock, D = stiff soil (default), E = soft clay soil, F = soils requiring site-specific evaluation (e.g., liquefiable, sensitive clays).

20. What are the site coefficients $F_a$ and $F_v$, and how do they vary with soil softness?

    $F_a$ = short-period site amplification factor, $F_v$ = long-period site amplification factor. Both generally increase as soil softens (toward Site Class E) and for lower shaking levels, amplifying bedrock motion into design accelerations.

21. Sketch the shape of the ASCE 7 design response spectrum and its key period $T_S$.

    For $T<T_0$: linear rise. For $T_0 \leq T \leq T_S$: constant $S_a = S_{DS}$ (plateau). For $T > T_S$: $S_a = S_{D1}/T$. With $T_0 = 0.2\,T_S$ and $$T_S = \frac{S_{D1}}{S_{DS}}.$$ Beyond the long-period transition $T_L$: $S_a = S_{D1}T_L/T^{2}$.

22. How is the Seismic Design Category (SDC) determined?

    The SDC (A through F) is the more severe of the categories found from two tables using $S_{DS}$ and $S_{D1}$, combined with the Risk Category. Sites near major faults with $S_1 \geq 0.75$ and Risk Category I–III are assigned SDC E (IV $\to$ F).

23. What is the Importance Factor $I_e$ and its typical values by Risk Category?

    $I_e$ scales seismic demand for consequence of failure: Risk Category I & II $\to I_e = 1.0$; III $\to 1.25$; IV (essential facilities) $\to 1.50$.

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