Earthquake engineering (Ch. 18–21 context) adds V=CsW, empirical T, and S/R calculators—use project spectrum for design.

Scope (full earthquake engineering)

This is the expanded handbook route for earthquake effects and design—not the mechanics-only view on Structural Dynamics, which stays at basics (SDOF period, harmonic magnification, simple equivalent-static base shear). Here the focus is damage, building seismic design, bridge seismic design, and performance-based seismic design per Chapters 18–21. Fundamentals and hazard framing (handbook Ch. 17) still underpin everything; site spectra, ductility, and code implementation (e.g. SANS 10160) govern real projects.

Handbook alignment. Handbook of Structural Engineering (Chen & Lui, 2nd ed.) — Section IV — Earthquake engineering and design. This page emphasises Chapter 18 — Earthquake damage; Chapter 19 — Seismic design of buildings; Chapter 20 — Seismic design of bridges; Chapter 21 — Performance-based seismic design. Pair with Ch. 17 (fundamentals) via Structural Dynamics for period and simple lateral-force illustrations.

Reference check (hazard → period → lateral demand)

  1. Spectrum / coefficient — Obtain design ground motion or equivalent coefficients from the approved hazard study and SANS 10160; the V = CsW and Sd calculators are teaching placeholders only.
  2. Period — Estimate building period (code formula or analysis); compare with the empirical T check—real projects use multi-modal response and irregularity rules.
  3. Capacity & detailing — Translate lateral demand into ductility class, diaphragm and connection design, and peer-reviewed analysis when required—use specialist seismic software for code-aligned models.

Structural Engineering — Earthquake Engineering

Expanded Section IV coverage: damage, buildings, bridges, and performance-based seismic design (Handbook Ch. 18–21)—beyond SDOF and hand base shear.

How this page relates to Chapters 18–21

Section IV of the handbook develops earthquake engineering across several long chapters (including hazard and fundamentals in Ch. 17). Chapters 18–21 are not summarised on this page. What follows is a roadmap of what each chapter is about; project design uses SANS 10160, site-specific hazard, ductility classes, and usually specialist software and peer review.

Illustrations (damage and dynamics)

Earthquake engineering ties physical damage and dynamic response to code procedures. The figures below are educational schematics—not project hazard or damage assessments.

Stylised city blocks with damage and debris after an earthquake
Stylised post-earthquake cityscape (damage, debris, fire). CC0, Wikimedia Commons
Log log frequency response of a harmonic oscillator
Harmonic oscillator frequency response (gain vs frequency)—SDOF concepts underpin spectrum methods. CC BY-SA 3.0, Wikimedia Commons

What earthquake engineering produces

Beyond Structural Dynamics hand checks, real seismic design delivers:

  • Design ground motion — Spectra or equivalent static coefficients per SANS 10160 and site studies.
  • System choices — Lateral system type, diaphragm and collector design, capacity design and detailing for ductility.
  • Documentation — Analysis reports, peer review packages, and performance-based studies for important or irregular structures.

Code basis (South Africa)

SANS 10160 structures seismic actions and combinations for buildings and similar works. Geotechnical hazard (liquefaction, slope displacement) links to geotechnical standards and site investigation. Always use the current national annex and project-specific hazard where required.

Notation (on-page calculators)

  • Base shear — W seismic weight; Cs seismic coefficient; V base shear.
  • Period — h building height (m); Ct empirical coefficient per code guidance for the system type.
  • Spectral reduction — S spectral acceleration (g); R generic force-reduction placeholder; Sd reduced acceleration.

Basics vs full earthquake engineering

The Structural Dynamics page teaches Chapter 3 mechanics and a minimal seismic hand check (e.g. V = CsW)—useful for intuition and rough period checks. It does not replace the design scope of Ch. 18–21: failure modes in real earthquakes, code-style building and bridge seismic provisions, or performance-based objectives and evaluation.

Chapter 18 — Earthquake damage (handbook scope)

What the chapter covers

  • Structural mechanisms — Flexural plastic hinges vs brittle shear; joint shear–flexure balance; wall and frame coupling.
  • System failures — Soft/weak storeys, torsion, pounding between blocks, progressive collapse triggers.
  • Geotechnical interaction — Liquefaction, lateral spreading, slope movement affecting foundations.
  • Non-structural — Cladding, partitions, equipment—life-safety and operational consequences.
  • Lessons for design — Why ductility, redundancy, and detailing rules in codes exist; priorities for assessment and retrofit.

Chapter 19 — Seismic design of buildings (handbook scope)

What the chapter covers

  • System types — Moment frames, braced frames, shear walls, dual systems; height and regularity effects.
  • Analysis procedures — Equivalent lateral force, modal response spectrum, time history; mass and stiffness modelling; accidental eccentricity.
  • Design concepts — Capacity design, strong-column/weak-beam ideals, diaphragm forces and collector elements, drift and stability limits.
  • Detailing — Ductility classes, confinement, connection design for energy dissipation.
  • Integration — Non-structural anchorage, stairs, façades; documentation for authority review.

Chapter 20 — Seismic design of bridges (handbook scope)

What the chapter covers

  • Structural forms — Continuous and simply supported spans; deck–pier–foundation load path; bearings and joints.
  • Substructure — Pier ductility, shear keys, abutment soil pressure; transverse vs longitudinal response.
  • Isolation and dissipation — Base isolation, dampers—when and how they change demand and displacement capacity.
  • Soil–structure — Foundation stiffness, liquefaction, kinematic loading on piles.
  • Construction — Staged erection, temporary stability, and as-built vs as-designed assumptions.

Chapter 21 — Performance-based seismic design (handbook scope)

What the chapter covers

  • Objectives — Explicit hazard levels (frequent, design, maximum considered) and performance targets (IO, LS, CP).
  • Analysis — Nonlinear static (pushover) and nonlinear dynamic procedures; fragility and uncertainty.
  • Acceptance — Deformation limits, component repairability, residual drift; peer review and regulatory paths.
  • When used — Irregular or important structures, retrofit, or when prescriptive code is insufficient.

The on-page V, T, and Sd calculators are teaching toys—Chapter 19–21 design uses approved spectra, multi-modal analysis, and code ductility rules.

Section IV — seismic calculators (illustrative)

Equivalent static base shear, empirical building period, and reduced spectral acceleration for a simple SDOF check—always follow project spectrum and code.

Calculator — base shear V = Cs W

Equivalent static (Ch. 17–19 context)

Equivalent static seismic base shear V = Cs × W from coefficient and seismic weight.

Calculator — empirical building period

Ch. 19 — rough T for regular buildings

T ≈ Ct h3/4   (h in m; Ct depends on system—enter per code guidance)

Height-based estimate

Approximate fundamental period T ≈ Ct h3/4 from building height (code-style empirical form).

Calculator — design spectral acceleration (SDS-style)

Ch. 17 / 21 — illustrative reduction

Sd = S / R (generic; R = force reduction / overstrength factor placeholder)

Reduced acceleration

Illustrative design spectral acceleration Sd = S/R from spectral acceleration and force-reduction placeholder R.

Software and seismic analysis

Modal and nonlinear seismic analysis, pushover procedures, and code-checked member design require specialist software. Examples (official vendor sites; use current licences and training for production work):

No endorsement of a particular product—seismic design must follow SANS 10160 and the regulator’s expectations for the building class.

Diagram sources

Educational schematics. Diagrams on this page were downloaded from Wikimedia Commons into Images/earthquake-engineering/—not reused from other topic folders.