Seismic Design Philosophy and Codes

Introduction

Earthquake-resistant design is not based on the expectation that a building will remain completely elastic during a severe earthquake. Such a requirement would usually be uneconomical and, in some cases, physically unrealistic. Modern seismic design therefore seeks a controlled hierarchy of performance: buildings should remain operational under frequent minor earthquakes, sustain limited damage under moderate earthquakes, and avoid collapse under rare, severe earthquakes. This philosophy combines structural mechanics, probabilistic hazard assessment, ductile detailing, capacity design, construction quality, and regulatory judgment.

Seismic codes translate this philosophy into design actions and rules. Important international frameworks include ASCE/SEI 7 and ACI 318 in the United States, Eurocode 8 with Eurocode 0 and Eurocode 1 in Europe, the International Building Code, New Zealand Standards, and national standards such as India’s IS 1893 and IS 13920. These documents differ in terminology and numerical factors, but their underlying principles are broadly similar.

Learning Objectives

After studying this chapter, the reader should be able to:

1. Distinguish force-based and displacement-based seismic design.

2. Explain ductility, overstrength, redundancy, regularity, and capacity design.

3. Interpret importance categories and seismic load combinations.

4. Identify the purpose of seismic detailing requirements.

5. Compare major international code frameworks and recognize their limitations.

6. Apply code concepts to preliminary design decisions and professional review.

1. Performance-Based Seismic Design Philosophy

1.1 Earthquake hazard and performance objectives

Seismic design begins with a hazard model. Ground motion is described by parameters such as peak ground acceleration, response spectra, duration, frequency content, and probability of exceedance. A code generally specifies one or more hazard levels, for example:

• a frequent or service-level earthquake, for which damage should be minor;
• a design-level earthquake, for which repairable damage may be accepted; and
• a maximum considered or maximum credible earthquake, for which collapse prevention is required.

The term “performance objective” describes the relationship between hazard level and acceptable structural and non-structural damage. A hospital, emergency operations centre, or fire station normally has a higher performance objective than an ordinary office building because post-earthquake function is socially important.

Performance is not determined only by member strength. It includes inter-storey drift, residual deformation, connection damage, falling hazards, equipment anchorage, fire protection, water ingress, and the ability to reoccupy the building. Consequently, seismic safety is a system property rather than merely a collection of member checks.

1.2 Life safety versus economic optimization

Codes establish minimum requirements, not a guarantee of zero damage or continued operation. A conventional code-compliant building is generally intended to protect life by preventing collapse and by controlling dangerous failure modes. The owner may require enhanced objectives, such as immediate occupancy or rapid recovery, through performance-based design, higher design forces, special detailing, isolation, damping, or structural redundancy.

This creates an important professional distinction: “code compliant” does not automatically mean “damage free,” “repairable,” or “functional after the earthquake.” These outcomes must be explicitly specified and verified.

2. Force-Based and Displacement-Based Design

2.1 Elastic force demand and design reduction

A single-degree-of-freedom system with mass m and elastic spectral acceleration Sa has an approximate elastic base-shear demand

V_e = m S_a,

where V_e is force, m is effective seismic mass, and Sa is spectral acceleration in consistent units. A force-based code reduces this elastic demand to a design force using factors representing ductility, overstrength, and sometimes redundancy. In simplified form,

V_d = V_e / R,

where R is a code-defined response modification or behavior factor. This expression is conceptual: actual codes define base shear using mapped hazard, site class, period, importance, and code-specific coefficients. R is not a pure material property. It represents the combined effect of ductility, energy dissipation, structural redundancy, and reserve strength.

The reduction is permissible only if the structure is detailed to sustain the associated inelastic response. Applying a large R to a brittle or poorly detailed system is unsafe.

2.2 Displacement demand

For a linear single-degree-of-freedom oscillator, spectral displacement may be related to spectral acceleration by

S_d = S_a (T/2π)^2,

where Sd is spectral displacement, T is natural period in seconds, and Sa is expressed as acceleration in consistent length-per-time-squared units. This relation applies to a linear oscillator and is commonly used to interpret elastic response spectra. In inelastic design, displacement demand is influenced by period, hysteretic behavior, strength, ductility, damping, and degradation; therefore, elastic displacement cannot simply be substituted for nonlinear peak displacement in all cases.

Displacement-based design selects a target displacement or drift and designs the structure to achieve it. It is particularly useful when damage, repairability, residual drift, or non-structural performance is important. Direct displacement-based design commonly uses an equivalent linear representation with an effective period and damping, but the selected procedure must be calibrated to the structural system and code framework.

2.3 Comparison

Force-based design is familiar, relatively efficient, and well integrated into prescriptive codes. Its limitations include dependence on assumed period, difficulty representing stiffness degradation, and the possibility that equal design forces produce very different drift and damage demands in different systems.

Displacement-based design focuses more directly on deformation, which is closely related to damage. However, it requires reliable estimates of stiffness, damping, hysteresis, effective mass, and target performance. It may also be sensitive to modelling assumptions and is not a substitute for strength and stability checks. In advanced practice, force and displacement checks are complementary rather than mutually exclusive.

3. Ductility and Energy Dissipation

3.1 Definition and significance

Ductility is the ability of a structural component or system to undergo significant inelastic deformation while retaining useful strength and stability. A common displacement ductility measure is

μ = Δ_max / Δ_y,

where Δmax is the maximum considered displacement and Δy is the displacement at first significant yield. This ratio is meaningful only when yield displacement and the relevant deformation measure are defined consistently.

Ductility allows a structure to dissipate earthquake energy through stable hysteretic cycles. It does not mean that damage is avoided. Plastic hinges, reinforcement yielding, local buckling, cracking, connection damage, and residual drift may occur. Ductility must therefore be accompanied by confinement, anchorage, shear protection, and control of failure modes.

3.2 Local and global ductility

Local ductility concerns sections, reinforcement, connections, and individual members. Global ductility concerns the ability of the complete structural system to form a stable and distributed mechanism. A building may contain ductile beams but still have poor global behavior if it develops a soft storey, weak columns, torsional concentration, or brittle joint failure.

Ductility classes in codes usually correspond to different detailing demands and response factors. Higher ductility generally permits lower design forces, but it also demands greater construction precision and inspection.

4. Capacity Design and the Hierarchy of Strength

Capacity design deliberately establishes which components yield and which components remain essentially elastic. The designer first selects a desirable ductile mechanism and then protects other components against the maximum forces that can be generated by that mechanism.

For a moment-resisting frame, a common objective is “strong columns–weak beams.” Beam plastic hinges form at selected locations, while columns, beam-column joints, foundations, and shear-resisting components retain adequate capacity. The exact implementation depends on the code and structural system. Capacity design does not imply that columns can never yield; rather, it seeks to prevent a storey mechanism that could cause rapid loss of stability.

A conceptual capacity-design relationship is

E_d ≤ E_cap,

where Ed is the design action in a protected component and Ecap is the action associated with probable or overstrength capacity of the yielding components. In practice, Ecap is calculated using probable material strengths, strain hardening, reinforcement limits, equilibrium, and code-specified factors—not merely nominal design strength.

Typical capacity-design applications include:

• designing beam shear strength for probable flexural strength;
• designing columns for beam overstrength moments;
• protecting beam-column joints against brittle shear failure;
• designing braces, gusset plates, collectors, diaphragms, and foundations for system overstrength; and
• preventing anchorage or connection failure before member yielding.

5. Overstrength, Redundancy, and Regularity

5.1 Overstrength

Actual strength often exceeds calculated nominal design strength because of conservative dimensions, reinforcement minima, material strengths greater than specified values, strain hardening, and load paths not fully represented in the model. The ratio of actual or probable strength to design strength is commonly described as overstrength.

Overstrength is beneficial because it provides reserve capacity, but it can shift inelastic demand to unintended locations. For example, stronger-than-expected beams can force columns or joints to yield. Capacity design must therefore account for probable strengths rather than relying solely on nominal member capacities.

5.2 Redundancy

Redundancy is the availability of multiple components and load paths capable of resisting earthquake actions. A redundant frame may redistribute force after local yielding or damage. A structure with only one critical resisting line may experience severe consequences from local failure.

Redundancy is not identical to indeterminacy. A highly indeterminate structure is not necessarily redundant if all its resistance depends on one vulnerable connection or diaphragm. Effective redundancy requires compatible deformation, reliable connections, and a continuous load path from diaphragms to foundations.

5.3 Regularity

Plan regularity concerns symmetry, mass distribution, stiffness, strength, and geometry. Vertical regularity concerns continuity of columns, walls, stiffness, strength, and mass over the height. Irregularities can cause torsion, concentration of drift, discontinuous force transfer, pounding, or soft-storey collapse.

Common irregularities include re-entrant corners, large openings, eccentric cores, sudden setbacks, transfer floors, weak or soft storeys, vertical discontinuity of walls, and substantial mass changes. Codes may require more conservative analysis, additional accidental torsion, modal analysis, diaphragm checks, or restrictions on structural systems when irregularity is significant.

Regularity is a design advantage, not an absolute safety condition. Irregular buildings can be designed safely, but they require more realistic modelling, stronger attention to load paths, and often nonlinear analysis.

6. Seismic Load Paths and Structural Systems

Earthquake inertia forces arise from acceleration of structural mass. A complete load path transfers these forces through floor and roof diaphragms to vertical lateral-force-resisting elements and then into foundations and soil. The path includes collectors, chords, anchors, connections, walls, frames, foundation ties, and soil contact.

Principal systems include:

• moment-resisting frames, which resist lateral forces through flexure and joint action;
• structural walls, which provide high stiffness and strength but may attract large force and foundation demand;
• braced frames, which use axial forces in braces and may be concentric or eccentric; and
• dual systems, which combine frames and walls or braces with defined sharing of resistance.

The choice depends on height, architectural requirements, drift control, site conditions, construction capability, fire and durability requirements, and expected seismic demand. Stiff systems generally reduce drift but may attract higher force and experience high acceleration-sensitive non-structural demand. Flexible ductile systems may reduce force but require careful drift and stability control.

7. Importance Categories and Risk Classification

Codes classify buildings according to consequences of failure, occupancy, emergency function, and sometimes hazard to the public. Ordinary residential or commercial buildings commonly occupy a standard category. Hospitals, emergency facilities, schools, major communication centres, and buildings containing hazardous materials may receive higher importance factors or more demanding performance requirements.

An importance factor generally increases design demand or imposes enhanced detailing, but its exact use is code-specific. It should not be treated as a universal multiplier independent of the hazard model. Classification also affects inspection, quality assurance, seismic restraint of equipment, non-structural components, and post-earthquake functionality.

Professional judgment is essential for mixed-use buildings, facilities with hazardous inventories, buildings serving vulnerable populations, and structures whose failure could cause cascading infrastructure disruption.

8. Seismic Load Combinations

Seismic effects are combined with gravity and other actions using code-prescribed factored load combinations. A generic strength combination may be expressed conceptually as

U = Σγ_i Q_i ± E,

where U is the factored action effect, Qi are permanent and variable actions, γi are code-specified factors, and E is the seismic effect with both positive and negative directions considered. The actual combination must be taken from the governing code because factors differ for dead load, live load, snow, wind, fluid, soil, and earthquake actions.

Two issues require particular care. First, seismic effects are reversible, so both signs and orthogonal combinations may be required. Second, vertical earthquake effects may be important for long spans, cantilevers, transfer structures, prestressed members, and elements with high gravity demand. Foundation design may also require uplift, overturning, sliding, soil bearing, and geotechnical stability checks.

Accidental torsion accounts for uncertainty in mass, stiffness, and ground motion. It is not a substitute for modelling actual eccentricity. P-Δ effects must be considered when gravity load acting through lateral displacement creates significant additional moment. A commonly used stability coefficient has the conceptual form

θ = P Δ /(V h),

where P is the gravity load above the storey, Δ is storey drift, V is storey shear, and h is storey height. Acceptance limits and calculation definitions are code-specific.

9. Detailing Rules and Constructability

Seismic detailing converts analytical ductility assumptions into physical behavior. Important rules include:

• confinement reinforcement in potential plastic hinge regions;
• closely spaced transverse reinforcement near beam-column joints and wall boundaries;
• adequate development length, lap-splice location, and anchorage;
• prevention of longitudinal bar buckling after cover spalling;
• shear strength greater than the shear associated with flexural overstrength;
• continuity of diaphragms, collectors, chords, and wall boundary elements;
• reliable brace, gusset, and moment-connection detailing in steel structures;
• positive ties between precast elements and the primary structure; and
• seismic restraint of partitions, ceilings, façades, tanks, pipes, mechanical equipment, and electrical systems.

Detailing rules are often prescriptive because failures may arise from local instability, bond deterioration, congestion, poor welding, inadequate inspection, or construction deviations that are difficult to capture in global analysis. Constructability must be reviewed early. Reinforcement that cannot be placed, vibrated, inspected, and anchored reliably is not a valid ductile design.

10. International Code Frameworks

10.1 United States framework

ASCE/SEI 7 provides structural loading provisions, seismic hazard parameters, site classification, response spectra, analysis procedures, structural system coefficients, drift limits, and combinations. Material standards such as ACI 318 for concrete and AISC 341 for steel provide system-specific design and detailing. The International Building Code integrates many of these requirements into a regulatory model.

10.2 Eurocode framework

Eurocode 8 is used with Eurocode 0 and Eurocode 1. It defines seismic actions through design ground acceleration, soil factors, spectral shapes, behavior factors, ductility classes, importance classes, analysis methods, drift checks, and rules for concrete, steel, composite, masonry, timber, and foundations. Nationally determined parameters allow adaptation to regional conditions.

10.3 Other national systems

New Zealand standards emphasize ductile capacity design and detailed structural-system requirements. Indian practice commonly uses IS 1893 for seismic actions and IS 13920 for ductile detailing, together with material and foundation standards. Japan, Chile, Canada, Australia, and other countries maintain frameworks reflecting their hazard, construction, materials, and regulatory histories.

Codes should not be mixed casually. A response factor from one standard, a spectrum from another, and detailing rules from a third may produce an internally inconsistent design. When international practice is necessary, the governing authority, hazard basis, units, reliability assumptions, and compatible material standards must be identified explicitly.

11. Worked Application: Preliminary Review of a Regular Frame

Consider a five-storey reinforced-concrete office building with an estimated effective seismic mass of 2,400 Mg. For a preliminary conceptual check, suppose the elastic spectral acceleration at the effective period is 0.60g and the selected code response factor is R = 5.0. Taking g = 9.81 m/s²,

m = 2,400 Mg = 2.4 × 10^6 kg,

V_e = mS_a = (2.4 × 10^6)(0.60 × 9.81) = 14.13 × 10^6 N = 14.13 MN.

The conceptual reduced base shear is

V_d = V_e/R = 14.13/5.0 = 2.83 MN.

This is not a complete code design. A real calculation must verify the code minimum base shear, period limits, site and importance factors, vertical distribution, accidental torsion, orthogonal effects, drift, P-Δ stability, diaphragm forces, foundation actions, and the applicability of R to the selected structural system.

Suppose the design storey shear produces a roof-to-ground drift pattern whose maximum inter-storey drift is 0.085 m over a 3.4 m storey. The drift ratio is

0.085/3.4 = 0.025 = 2.5%.

Whether this is acceptable depends on the governing code, occupancy, structural system, and drift definition. Even if the ratio satisfies a structural drift limit, non-structural damage may be unacceptable. The review should therefore examine cladding movement, partitions, elevators, stairs, utility connections, and residual drift. The example demonstrates why base shear alone cannot establish seismic adequacy.

12. Illustrative Case: Soft-Storey Vulnerability

Background

An illustrative six-storey residential building has open parking at ground level and masonry partitions on upper floors. The ground storey contains few walls and has substantially lower stiffness than the upper storeys.

Problem

A linear code analysis produces acceptable total base shear and member strength ratios. However, the calculated ground-storey drift is nearly twice that of any upper storey. Columns also carry large axial loads, and architectural openings restrict the available beam depth.

Analysis and approach

The condition is identified as a vertical stiffness and strength irregularity. A more realistic model includes cracked member stiffness, diaphragm action, P-Δ effects, and the actual distribution of mass and walls. The design team evaluates alternatives: adding reinforced-concrete walls at the perimeter, strengthening columns and joints, introducing steel bracing, and improving the continuity of the upper-storey walls into the foundation. Nonlinear static analysis is used as a diagnostic tool, while the final design remains consistent with the governing code and required analysis method.

Outcome

The selected solution adds continuous walls and improves column confinement and joint capacity. Ground-storey drift is redistributed, the intended yielding mechanism is developed above the foundation, and the parking layout is modified to maintain a continuous load path. Non-structural anchorage is upgraded.

Learning points

Adequate total strength can coexist with dangerous local drift concentration. Regularity, capacity design, and deformation compatibility are therefore as important as base-shear resistance. Architectural decisions made early can either create or eliminate seismic vulnerability.

13. Limitations, Governance, and Contemporary Practice

Prescriptive codes necessarily simplify uncertain phenomena. They use idealized spectra, approximate damping, conventional response factors, and assumed failure mechanisms. They may not accurately predict repair cost, residual drift, soil-structure interaction, pounding, liquefaction, façade damage, or functionality of equipment. Nonlinear analysis can improve insight but is not automatically more accurate: results depend on constitutive models, record selection and scaling, damping, numerical convergence, and engineering interpretation.

Peer review is valuable for important or irregular projects. It should examine hazard selection, modelling assumptions, load paths, capacity hierarchy, detailing, constructability, and non-structural systems rather than merely checking arithmetic. Regulatory approval, independent checking, inspection, material testing, and documentation are governance mechanisms that reduce professional and public risk.

Digital tools and AI can assist with code retrieval, model checking, clash detection, reinforcement scheduling, record processing, and anomaly identification. They cannot replace the engineer’s responsibility for selecting appropriate assumptions, interpreting uncertain results, protecting confidential data, and verifying that generated outputs correspond to the adopted code edition. Traceability, human review, version control, and validation against benchmark problems are essential.

Contemporary seismic engineering increasingly emphasizes functional recovery, resilience, low-damage systems, base isolation, supplemental damping, embodied carbon, and community-scale interdependence. These objectives extend beyond minimum life-safety design and require coordination among owners, authorities, architects, engineers, contractors, insurers, and emergency planners.

Best-Practice Design Workflow

1. Identify the governing code, hazard level, site class, occupancy, and performance objective.

2. Establish a continuous and inspectable load path.

3. Select a regular, redundant, and constructible structural system.

4. Determine mass, stiffness, period, damping, and analysis procedure consistently.

5. Design for strength, drift, stability, torsion, diaphragm action, and foundation response.

6. Apply capacity design using probable overstrength where required.

7. Detail yielding regions and protect brittle components.

8. Coordinate non-structural components and building services.

9. Verify constructability, inspection, testing, and quality assurance.

10. Document assumptions, code references, limitations, and residual risks.

Chapter Summary

Seismic design seeks controlled performance rather than purely elastic behavior. Force-based design uses code-defined reductions of elastic demand, while displacement-based design focuses more directly on drift and damage. Ductility permits stable inelastic deformation, but it is reliable only when supported by confinement, anchorage, shear protection, and sound construction.

Capacity design establishes a hierarchy in which selected components yield while critical components remain protected. Overstrength, redundancy, regularity, importance classification, accidental torsion, P-Δ effects, and complete load paths strongly influence real performance. Load combinations must follow the governing code, and detailing rules are essential because global analysis cannot represent every local failure mode.

International codes differ in parameters and terminology but share the objectives of life safety, controlled damage, and collapse prevention. Code compliance is a minimum regulatory condition, not a promise of immediate occupancy or negligible repair cost. Advanced practice integrates nonlinear analysis, peer review, non-structural protection, resilience objectives, quality assurance, and responsible use of digital tools.

Key Terms

Ductility: Ability to sustain inelastic deformation without unacceptable loss of strength or stability.

Capacity design: Method of selecting a hierarchy of yielding and protected components.

Overstrength: Strength exceeding the nominal design strength.

Redundancy: Availability of multiple components or load paths for resistance and redistribution.

Regularity: Uniformity of mass, stiffness, strength, and geometry in plan and elevation.

Response modification factor: Code factor representing ductility, overstrength, and system behavior.

Inter-storey drift: Relative lateral displacement between adjacent floors.

Performance objective: Required damage and functionality level for a specified hazard.

Plastic hinge: Localized region designed to undergo inelastic rotation.

Strong-column weak-beam: Hierarchy intended to promote beam rather than storey-column mechanisms.

Load path: Continuous route by which earthquake forces reach the foundations and ground.

Importance category: Classification reflecting consequences and required reliability of a facility.

Accidental torsion: Code allowance for uncertainty in mass, stiffness, and ground motion.

P-Δ effect: Additional moment caused by gravity load acting through lateral displacement.

Diaphragm: Floor or roof element distributing lateral forces to vertical resisting elements.

Soft storey: Storey with substantially lower stiffness than adjacent storeys.

Response spectrum: Graph of peak response versus natural period for a specified ground motion or hazard.

Non-structural component: Architectural, mechanical, electrical, or contents element not part of the primary structure.

Functional recovery: Ability to restore intended building use after an earthquake.

Review Questions

Short Answer Questions

1. What is the principal difference between force-based and displacement-based seismic design?

2. Define ductility and explain why ductility alone does not guarantee seismic safety.

3. What is the purpose of capacity design?

4. Distinguish structural redundancy from structural indeterminacy.

5. Why are non-structural components included in seismic performance assessment?

Long Answer Questions

1. Explain the relationship between hazard levels, performance objectives, and code-based life-safety design.

2. Discuss how overstrength and probable material strengths influence capacity design.

3. Compare the advantages and limitations of moment frames, structural walls, braced frames, and dual systems.

4. Explain the role of regularity, torsion, and P-Δ effects in seismic response.

5. Compare the general frameworks of ASCE/SEI 7, Eurocode 8, and a national seismic code of your choice.

Analytical / Application Questions

1. A building has an effective seismic mass of 1,800 Mg, elastic spectral acceleration of 0.50g, and response factor R = 4.0. Calculate the conceptual elastic and reduced base shears, using g = 9.81 m/s², and list the code checks still required.

2. A six-storey building has acceptable total base shear but a ground-storey drift ratio three times that of the upper storeys. Diagnose the likely vulnerability and propose two structural interventions.

3. Develop a preliminary seismic design strategy for a hospital on a soft-soil site, addressing importance, structural system, drift, non-structural components, redundancy, analysis, and post-earthquake functionality.

Multiple Choice Questions with Answers

Question 1

What is the primary purpose of capacity design?

A. To ensure every member remains elastic during the design earthquake

B. To establish a controlled hierarchy of yielding and protect brittle components

C. To eliminate the need for seismic load combinations

D. To reduce the importance of construction quality

Correct Answer: B. To establish a controlled hierarchy of yielding and protect brittle components

Question 2

In the conceptual relation Vd = Ve/R, what does R represent?

A. Storey height

B. Response modification associated with system behavior

C. Foundation overturning resistance

D. Live-load factor

Correct Answer: B. Response modification associated with system behavior

Question 3

Which condition most directly indicates a soft storey?

A. Uniform stiffness over the building height

B. Substantially lower storey stiffness than adjacent storeys

C. A symmetrical floor plan

D. A continuous shear wall

Correct Answer: B. Substantially lower storey stiffness than adjacent storeys

Question 4

For a linear oscillator, spectral displacement is related to spectral acceleration by which expression?

A. Sd = SaT

B. Sd = Sa/T

C. Sd = Sa(T/2π)^2

D. Sd = Sa(2πT)^2

Correct Answer: C. Sd = Sa(T/2π)^2

Question 5

The strong-column weak-beam concept primarily seeks to prevent:

A. Beam flexural yielding

B. A hazardous storey mechanism caused by column failure

C. Diaphragm force transfer

D. All foundation settlement

Correct Answer: B. A hazardous storey mechanism caused by column failure

Question 6

A complete seismic load path transfers inertia forces from:

A. Foundations directly to roof finishes only

B. Mass through diaphragms and vertical resisting elements to the ground

C. Columns to mechanical equipment only

D. Soil to partitions without structural connections

Correct Answer: B. Mass through diaphragms and vertical resisting elements to the ground

Question 7

What does redundancy provide in a seismic structural system?

A. Multiple potential load paths and redistribution capacity

B. Guaranteed absence of damage

C. A replacement for ductile detailing

D. Elimination of torsional response

Correct Answer: A. Multiple potential load paths and redistribution capacity

Question 8

For m = 2.0 × 10^6 kg, Sa = 0.50g, and R = 5, the conceptual reduced base shear is approximately:

A. 0.98 MN

B. 1.96 MN

C. 4.91 MN

D. 9.81 MN

Correct Answer: B. 1.96 MN

Question 9

Why is code compliance not equivalent to immediate occupancy?

A. Codes generally target minimum safety and collapse prevention, not zero damage

B. Codes do not consider gravity loads

C. Codes prohibit non-structural design

D. Codes apply only to foundations

Correct Answer: A. Codes generally target minimum safety and collapse prevention, not zero damage

Question 10

Which action is most appropriate when combining international seismic standards?

A. Mix factors freely to obtain the lowest design force

B. Use a spectrum from one code and detailing from any unrelated code

C. Maintain consistency among hazard basis, factors, analysis, materials, and detailing

D. Ignore the governing authority

Correct Answer: C. Maintain consistency among hazard basis, factors, analysis, materials, and detailing