Seismic Design of Reinforced-Concrete Structures

Introduction and Context

Reinforced-concrete (RC) structures perform well in earthquakes only when strength, stiffness, ductility, regularity, and detailing are considered together. Earthquake-resistant design is not simply the provision of larger members or greater reinforcement. It is the deliberate control of how a structure yields, dissipates energy, redistributes forces, and preserves life safety after significant inelastic deformation.

The central design principle is capacity design: selected ductile components are permitted to yield, while brittle components and critical load paths are protected from failure. In a moment-resisting frame, for example, beams may be designed to form plastic hinges while columns, joints, foundations, and shear-resisting elements remain sufficiently strong. This produces a predictable mechanism rather than a sudden collapse.

Design must comply with the governing national standard and local seismic hazard provisions. Common references include ASCE 7 and ACI 318 in the United States, Eurocode 8 with Eurocode 2 in Europe, and equivalent national standards elsewhere. Numerical coefficients, detailing limits, load combinations, and drift limits are code-dependent; the principles in this chapter are intended to be used with the applicable standard, not as a substitute for it.

Learning Objectives

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

• explain the seismic behaviour of RC moment frames, shear walls, dual systems, diaphragms, joints, and foundations;
• distinguish ductile flexural behaviour from brittle shear, bond, anchorage, and joint failures;
• apply capacity-design reasoning to develop a reliable yielding mechanism;
• interpret basic seismic force, drift, and reinforcement calculations;
• identify common construction deficiencies and diagnose their structural consequences;
• evaluate the interaction between analysis assumptions, detailing, construction quality, and performance;
• use modern computational and monitoring tools responsibly in seismic design.

1. Seismic Design Philosophy

1.1 Performance objectives

Seismic design generally seeks several performance levels:

1. Operational or immediate occupancy: limited damage and continued use after a smaller or moderate earthquake.

2. Life safety: substantial damage may occur, but collapse is prevented and occupants can escape during a severe earthquake.

3. Collapse prevention: extreme inelastic damage is accepted, but a stable gravity-load system remains.

A building code usually provides minimum life-safety requirements rather than guaranteeing immediate occupancy. Owners, hospitals, emergency facilities, and critical infrastructure may require explicit performance-based objectives beyond code minimums.

1.2 Strength, stiffness, ductility, and redundancy

Strength is the capacity to resist force; stiffness controls deformation under force; ductility is the ability to sustain deformation beyond first yield without substantial loss of resistance. Redundancy provides alternative load paths when individual components are damaged. A safe structure requires a suitable balance. Excessive flexibility can produce unacceptable drift and second-order effects, whereas a very strong but poorly detailed structure may fail in a brittle mode.

For a single-degree-of-freedom idealization, the seismic design force is often represented in code form as

\[

V = C_s W

\]

where \(V\) is design base shear, \(C_s\) is the code-prescribed seismic response coefficient, and \(W\) is the effective seismic weight. This is a design model, not a universal physical law. The value of \(C_s\) depends on hazard, soil, period, ductility or response modification, importance, and code limitations. Base shear must be distributed vertically and horizontally according to the adopted code, and dynamic analysis may be required for irregular or tall buildings.

1.3 The hierarchy of failure

A desirable hierarchy is:

• flexural yielding in selected beams or wall boundaries;
• stable plastic rotation and hysteretic energy dissipation;
• yielding of carefully selected wall regions where appropriate;
• preservation of column axial and flexural capacity;
• preservation of shear, joint, anchorage, diaphragm, and foundation capacity.

Undesirable mechanisms include column sway, storey mechanisms caused by weak or soft storeys, diagonal shear failure, joint shear failure, lap-splice failure, bar anchorage failure, foundation overturning or sliding, and loss of diaphragm continuity.

2. Structural Configuration and Seismic Load Paths

A seismic load path extends from the mass at each floor through the diaphragm, collectors, vertical lateral-force-resisting elements, foundations, and ground. Every transfer must be explicit. Architectural discontinuities, large openings, setbacks, transfer floors, nonaligned walls, and discontinuous columns can produce force concentrations and torsional response.

2.1 Regularity

Plan regularity reduces torsion and improves the reliability of analytical models. Important considerations include near-symmetric stiffness and strength, limited re-entrant corners, continuous diaphragms, and avoidance of large eccentricities between mass and resistance. Vertical regularity requires continuity of columns and walls, gradual changes in stiffness and strength, and avoidance of abrupt setbacks.

A soft storey has substantially lower lateral stiffness than adjacent storeys; a weak storey has substantially lower lateral strength. These conditions can concentrate drift and damage in one level. Parking levels with few partitions and open ground floors are common examples. The remedy may involve additional walls, moment frames, bracing, stronger columns, or a revised architectural layout.

2.2 Torsion and accidental eccentricity

Even when the calculated centre of mass and centre of rigidity coincide, construction tolerances, nonstructural damage, and uncertain mass distribution create torsion. Codes therefore commonly require accidental eccentricity in analysis. Torsional response must be checked using both elastic analysis results and the possibility of concentration of inelastic demand at perimeter elements.

3. Ductile Reinforced-Concrete Moment Frames

3.1 Behaviour and mechanism

A moment frame resists lateral forces through flexure and shear in beams and columns. Under cyclic loading, plastic hinges may form at beam ends and, in some systems, at the bases of columns. The preferred mechanism for a typical building is strong-column/weak-beam behaviour. This does not mean columns are infinitely strong; it means the sum of column flexural strengths at a joint should exceed the sum of beam flexural strengths by the code-required margin, considering the relevant axial load and probable material strengths.

A simplified joint equilibrium expression is

\[

\sum M_{c} \geq \gamma \sum M_{b}

\]

where \(\sum M_c\) is the design sum of column moment capacities above and below the joint, \(\sum M_b\) is the corresponding beam capacity, and \(\gamma\) is a code-specified overstrength factor. The expression is a capacity-design check, not a complete analysis of joint behaviour. Actual calculations must consider axial force, reinforcement placement, biaxial bending, slab participation, and probable rather than nominal material strengths where required.

3.2 Beam design and detailing

Beam plastic hinges should form in regions where flexural yielding can occur without premature shear or bond failure. Essential measures include:

• continuous longitudinal reinforcement with reliable anchorage;
• adequate top reinforcement over supports and bottom reinforcement in spans;
• closely spaced closed hoops in potential hinge regions;
• seismic hooks and confinement that remain effective after cyclic cracking;
• restrictions on lap splices near plastic hinge zones;
• sufficient shear strength based on probable flexural overstrength.

For a beam with probable end moments, the design shear should not be based only on elastic analysis. A conceptual capacity-design expression is

\[

V_{u,cap} = \frac{M_{pr,L}+M_{pr,R}}{L_n} \pm V_g

\]

where \(M_{pr,L}\) and \(M_{pr,R}\) are probable positive and negative flexural strengths at the beam ends, \(L_n\) is the clear span, and \(V_g\) is the shear associated with gravity loads; the sign and load arrangement must be selected to maximize shear. The expression assumes plastic hinges at the ends and must be adapted to the governing code and loading direction.

3.3 Column design and confinement

Columns carry gravity loads during and after an earthquake. Axial compression reduces curvature ductility and can accelerate strength degradation. Transverse reinforcement must therefore confine the concrete core, restrain longitudinal bars against buckling, and resist shear. In potential hinge regions, hoops are closely spaced, properly anchored, and arranged with cross-ties so that all longitudinal bars are laterally supported.

Lap splices are particularly vulnerable in plastic hinge regions because cyclic tension-compression reversals can cause bond deterioration. Where splices are unavoidable, their location, length, transverse confinement, and proportion of spliced bars must comply with seismic provisions. Poorly confined columns may exhibit concrete spalling, bar buckling, rapid axial-capacity loss, and eventual storey collapse.

3.4 Strong-column/weak-beam limitations

The preferred mechanism is not appropriate without qualification for every building. Wall-frame interaction, transfer structures, irregular geometry, gravity-load sensitivity, and foundation flexibility can alter the mechanism. A building with very strong beams and weak columns may form a column mechanism even when elastic analysis appears satisfactory. Capacity design must therefore be checked at every critical joint and along the complete load path.

4. Shear Walls and Dual Systems

4.1 Wall behaviour

Structural walls provide high lateral stiffness and strength and are effective in limiting drift. Their behaviour involves flexure, shear, axial force, overturning, boundary compression, and coupling between wall segments. A slender wall often behaves as a flexural cantilever, while a squat wall may be governed by diagonal compression and shear mechanisms.

Wall boundary zones develop high compression and tension during overturning. Boundary elements may be required where compressive strains, axial load, or code criteria indicate that ordinary distributed reinforcement is insufficient. Confinement reinforcement must maintain the integrity of the compressed boundary after cover spalling.

4.2 Wall shear and capacity design

Wall shear should be checked against the shear associated with probable flexural development, not merely the elastic base shear. This protects against a brittle diagonal failure after the wall has developed its intended flexural strength. Openings create coupling beams, which may require diagonal reinforcement or specially detailed transverse reinforcement because their shear demand is high and stress reversals are severe.

4.3 Dual systems

A dual system combines moment frames with walls or other primary lateral-force-resisting elements. The wall system commonly provides most stiffness and strength, while moment frames provide additional resistance, redundancy, and drift control. The frame must not be treated as nominally nonstructural unless the code explicitly permits that assumption; its required participation and detailing depend on the selected system classification.

The distribution of seismic forces between walls and frames is sensitive to relative stiffness, cracking, diaphragm action, foundation flexibility, and nonlinear response. Linear analysis using gross section properties can significantly misrepresent this distribution. Cracked-section stiffness assumptions should be justified and checked through sensitivity studies.

5. Diaphragms, Collectors, and Ties

Floor and roof diaphragms transfer inertial forces to vertical resisting elements. A diaphragm may act as rigid, semi-rigid, or flexible depending on its in-plane stiffness relative to the vertical elements and the building geometry. Treating a flexible diaphragm as rigid can underestimate local force demands; treating a stiff diaphragm as flexible can distort force distribution and torsional response.

Diaphragm design includes:

• in-plane shear and flexure;
• chords that resist diaphragm tension and compression;
• collectors or drag struts that gather and transfer forces;
• connections to walls and frames;
• openings, re-entrant corners, and discontinuities;
• continuity of reinforcement and anchorage.

A collector may carry forces much greater than those suggested by a simple tributary-area interpretation because it gathers load from a broad diaphragm region. Reinforcement must be developed through joints and around openings. Mechanical, electrical, and architectural penetrations should not sever critical diaphragm reinforcement without a designed alternative load path.

6. Beam-Column Joints

Beam-column joints are three-dimensional force-transfer regions, not merely intersections of line elements. Joint shear can be critical after beam and column flexural strengths are mobilized. Exterior joints may have limited anchorage length, while corner joints experience biaxial effects and geometric confinement limitations.

Seismic joint design should address:

• joint shear strength under load reversals;
• anchorage and development of beam bars;
• confinement of the joint core;
• continuity of column transverse reinforcement;
• bond deterioration and bar slip;
• interaction with slabs, transverse beams, and framing direction.

A joint that survives elastic analysis may still fail when beam bars yield and bond stresses reverse repeatedly. Beam bars should be anchored with adequate development length, hooks, headed bars, or other approved systems. Reinforcement congestion is not an acceptable reason to omit transverse reinforcement; constructability must be resolved during design.

7. Foundations and Soil–Structure Interaction

The foundation must transfer axial load, shear, and overturning while maintaining a stable soil contact condition. Seismic design checks commonly include sliding, overturning, bearing pressure, uplift, pile axial and lateral demands, foundation-member strength, and continuity of ties between individual foundations.

For a simplified rigid footing under a vertical force \(N\) and overturning moment \(M\), the linear elastic soil-pressure distribution over footing width \(B\) can be expressed as

\[

q_{max,min}=\frac{N}{A}\left(1\pm\frac{6e}{B}\right), \qquad e=\frac{M}{N}

\]

for a rectangular footing under the stated one-direction, uniform-soil, rigid-footing assumptions, with \(A\) as footing area. If the calculated minimum pressure is tensile, the soil cannot sustain that tension under ordinary contact assumptions; the compression zone becomes partial and a different pressure distribution must be used. This equation is therefore not valid for unrestricted uplift.

Foundation capacity design is essential. If an intended wall or frame yields, the foundation should not fail first through brittle punching, one-way shear, inadequate development, or uncontrolled rocking unless rocking is intentionally designed and verified. Soil flexibility can lengthen the effective period, modify force distribution, increase drift, and alter wall and frame demands. Nonlinear soil–structure interaction is particularly relevant for tall, heavy, irregular, or foundation-sensitive buildings.

8. Seismic Analysis and Drift Control

8.1 Analysis methods

Common analysis levels include:

• equivalent lateral-force procedures for regular buildings within code limits;
• modal response-spectrum analysis for systems with significant dynamic participation;
• linear response-history analysis for more detailed elastic assessment;
• nonlinear static or pushover analysis for mechanism and capacity assessment;
• nonlinear response-history analysis for advanced performance-based design.

No method eliminates engineering judgment. A sophisticated nonlinear model with incorrect hysteresis, stiffness, damping, or connection assumptions can be less reliable than a carefully reviewed simpler model.

8.2 Drift and P–Δ effects

Interstorey drift is a primary indicator of structural and nonstructural damage. The design drift ratio is commonly defined as

\[

\theta_i=\frac{\Delta_i}{h_i}

\]

where \(\Delta_i\) is the relative lateral displacement between two adjacent floors and \(h_i\) is the storey height. Code procedures may require amplification from elastic analysis to estimated inelastic displacement. Drift limits protect against instability, excessive damage, pounding, and failure of partitions, cladding, elevators, and utilities.

P–Δ effects arise when gravity load acts through displaced geometry. A useful storey stability indicator is

\[

\theta_{P\Delta}=\frac{P\Delta}{Vh}

\]

where \(P\) is the gravity load tributary to the storey, \(\Delta\) is storey displacement, \(V\) is storey shear, and \(h\) is storey height. Its interpretation and limiting values are code-specific. Significant values indicate that second-order effects reduce lateral resistance and may require redesign or nonlinear analysis.

9. Worked Design Illustration: Capacity Design of a Beam Segment

Consider an illustrative interior beam with clear span \(L_n=6.0\,m\). Probable positive and negative end flexural strengths are each estimated as \(M_{pr}=300\,kN\cdot m\). The factored gravity shear contribution that maximizes one direction of seismic shear is \(V_g=80\,kN\).

Assuming plastic hinges develop at both ends, the seismic component of shear is

\[

V_{eq}=\frac{300+300}{6.0}=100\,kN.

\]

The maximum capacity-design shear for the selected direction is therefore

\[

V_{u,cap}=100+80=180\,kN.

\]

The transverse reinforcement must be designed for at least the governing code combination involving this capacity-design shear, while also considering concrete contribution, axial effects if applicable, load reversals, and detailing limits. It would be unsafe to design the beam shear reinforcement solely for an elastic analysis value of, for example, 120 kN if that value is lower than the 180 kN capacity-design demand. The illustration demonstrates the principle; it does not replace code-specific shear equations or resistance factors.

10. Construction Detailing and Quality Assurance

Seismic performance is strongly affected by construction. Frequent deficiencies include:

• missing or widely spaced column hoops;
• open or improperly bent seismic hooks;
• lap splices placed in hinge zones;
• inadequate concrete cover or poor consolidation;
• reinforcement displaced from its designed location;
• discontinuous wall boundary reinforcement;
• unanchored collector bars;
• weak construction joints;
• unauthorized openings in beams, slabs, or walls;
• short columns created by partial-height infill walls;
• removal or alteration of walls during renovation.

Inspection should verify bar size, spacing, anchorage, splice location, confinement, embedment, concrete strength, placement, curing, and construction-joint preparation. Photographic records, rebar inspection checklists, batch records, non-destructive testing, and independent special inspection can support quality assurance, but none substitutes for competent site supervision.

Nonstructural components must also be anchored. Heavy ceilings, façade panels, mechanical equipment, tanks, parapets, partitions, and suspended services can injure occupants or block emergency response even when the primary frame remains stable.

11. Illustrative Case: Open-Storey RC Building

Background

Consider a fictional six-storey RC apartment building in a high-seismic region. The upper floors contain masonry partitions, while the ground floor is largely open for parking. The original design used perimeter moment frames and assumed uniform storey stiffness.

Problem

A review identified a major vertical irregularity: the upper-storey infill increased stiffness and strength, while the open ground floor had relatively few lateral-resisting elements. The analytical model also omitted the stiffness effect of the infill and did not check column shear using probable beam strengths.

Analysis

Under lateral loading, the upper floors behaved as a comparatively stiff block, concentrating drift in the open ground storey. Columns at the ground level experienced high shear and combined axial-flexural demand. If plastic hinges formed in these columns before beams, a ground-storey mechanism could develop. In addition, unconfined column lap splices were located close to the foundation, where plastic hinging was likely.

Approach and solution

The retrofit strategy included new reinforced-concrete walls positioned to reduce torsion, enlargement and confinement of critical ground-storey columns, relocation or strengthening of deficient splices, and positive anchorage of the diaphragm-to-wall load path. Masonry infill was surveyed and represented using an appropriate analytical idealization, while nonstructural walls were detailed to avoid unintended short-column effects. The foundation was checked for wall overturning, shear transfer, and development of new reinforcement.

Outcome

The revised system reduced ground-storey drift concentration, improved redundancy, and shifted the probable mechanism toward controlled beam and wall flexural damage. The outcome depended not only on member strength but also on continuity, detailing, construction sequencing, and the reliability of the infill assumptions.

Learning points

The case illustrates that seismic vulnerability can arise from interaction between structure and architecture. An apparently adequate frame may be unsafe when a soft storey, omitted infill, deficient column confinement, and incomplete foundation load path occur together.

12. Diagnosing Brittle Mechanisms

A useful diagnostic procedure is to ask, in sequence:

1. Where is first yield expected?

2. Can the yielded component sustain cyclic rotation?

3. Is shear strength greater than the shear generated by probable flexural capacity?

4. Are joints and anchorage stronger than the connected members?

5. Can columns retain axial capacity after damage?

6. Is the diaphragm able to transfer inertial forces and collector actions?

7. Can foundations transfer the resulting forces without brittle failure?

8. Do nonstructural components create unintended restraints or hazards?

Typical visual indicators include diagonal cracks in joints or walls, concentrated column cracking, spalled cover, buckled longitudinal bars, slipped bars, crushed wall toes, excessive residual drift, failed beam-column connections, and foundation settlement or rotation. Post-earthquake evaluation must be performed by qualified engineers using inspection protocols and, where needed, material testing and nonlinear assessment.

13. Professional, Regulatory, and Ethical Considerations

Engineers have a duty to protect life, communicate uncertainty, and avoid presenting code compliance as a guarantee of no damage. Design decisions should be traceable, calculations independently checked, and changes during construction formally reviewed. Value engineering must not remove confinement, anchorage, redundancy, or inspection provisions without demonstrating equivalent performance.

Codes establish minimum requirements, but local construction practice, enforcement, materials, workmanship, and emergency access affect actual risk. Engineers should report unsafe conditions even when correction is commercially inconvenient. Existing-building assessment requires particular care because drawings may be incomplete, materials uncertain, and past alterations undocumented.

14. Technology and Contemporary Developments

Building-information modelling can coordinate reinforcement, identify congestion, and preserve the intended load path. Automated checking can detect missing bars or inconsistent member dimensions, but model outputs require engineering verification. Digital twins and structural-health-monitoring systems can combine accelerometers, displacement sensors, inspection data, and damage models to support post-event decisions.

Artificial intelligence is increasingly used for image-based crack detection, surrogate modelling, demand prediction, and optimization. Its limitations include biased training data, poor transfer to unfamiliar structural systems, false confidence, and inability to assume professional liability. AI should assist—not replace—engineering judgment, code interpretation, inspection, and independent verification.

Emerging design practice emphasizes performance-based engineering, low-damage systems, replaceable structural fuses, rocking walls, supplemental damping, resilient foundations, and embodied-carbon reduction. These approaches require explicit modelling of repairability, residual drift, downtime, uncertainty, and life-cycle cost rather than relying only on peak strength.

Best-Practice Design Workflow

A robust workflow is:

1. define hazard, site conditions, occupancy, and performance objectives;

2. select a regular and clearly defined lateral-force-resisting system;

3. establish diaphragm, collector, wall, frame, and foundation load paths;

4. develop an analysis model with justified cracked stiffness and mass assumptions;

5. check strength, drift, torsion, P–Δ effects, and irregularities;

6. apply capacity design to beams, columns, walls, joints, diaphragms, and foundations;

7. detail reinforcement for cyclic loading, anchorage, confinement, and constructability;

8. coordinate structural and nonstructural components;

9. perform independent design review and construction inspection;

10. document assumptions, deviations, and maintenance or post-event inspection procedures.

Chapter Summary

Seismic design of RC structures is the design of a controlled inelastic system rather than a collection of individually strong members. Ductile moment frames should encourage beam hinging while protecting columns, joints, shear mechanisms, and foundations. Walls provide stiffness and strength but require careful treatment of boundary zones, shear, coupling beams, and overturning. Dual systems depend on realistic stiffness assumptions and reliable interaction between frames and walls. Diaphragms, collectors, joints, and foundations complete the seismic load path and must receive capacity-design attention.

Drift, torsion, P–Δ effects, irregularity, infill interaction, construction quality, and nonstructural safety are essential parts of performance. Brittle failure commonly results from inadequate confinement, shear or anchorage failure, weak-storey mechanisms, joint distress, diaphragm discontinuity, or foundation deficiencies. Codes provide minimum requirements, while performance-based methods and modern monitoring technologies support more explicit evaluation of damage, resilience, and uncertainty.

Key Terms

Capacity design: Designing critical components to remain stronger than components intentionally selected to yield.

Ductility: Ability to undergo inelastic deformation while retaining substantial strength and stability.

Plastic hinge: Localized region capable of sustaining inelastic rotation during flexural yielding.

Strong-column/weak-beam: Design hierarchy encouraging beam rather than column hinging at joints.

Moment frame: Lateral system resisting forces primarily through beam-column flexure and shear.

Structural wall: Vertical reinforced-concrete element resisting lateral force through flexure, shear, and axial action.

Dual system: Lateral system combining moment frames with walls or another primary resisting system.

Diaphragm: Floor or roof element transferring inertial forces to vertical resisting elements.

Collector: Element gathering diaphragm forces and transferring them to walls or frames.

Beam-column joint: Force-transfer region connecting beams and columns.

Interstorey drift: Relative lateral displacement between adjacent floors.

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

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

Weak storey: Storey with substantially lower lateral strength than adjacent storeys.

Boundary element: Confined wall zone designed to resist high compression or tension demands.

Probable strength: Estimated member strength using expected material properties and applicable overstrength provisions.

Soil–structure interaction: Mutual influence between foundation/soil flexibility and structural response.

Confinement: Transverse reinforcement and surrounding concrete action that restrain core concrete and longitudinal bars.

Residual drift: Permanent lateral deformation remaining after earthquake shaking.

Review Questions

Short Answer Questions

1. Why is capacity design central to ductile RC seismic design?

2. Distinguish a soft storey from a weak storey.

3. What functions do diaphragm collectors perform?

4. Why are lap splices discouraged in plastic hinge regions?

5. Identify two reasons why foundation design must consider probable member strength.

Long Answer Questions

1. Explain the intended inelastic mechanism of a ductile RC moment frame and discuss the detailing required to achieve it.

2. Compare structural walls, moment frames, and dual systems in terms of stiffness, strength, ductility, and analytical considerations.

3. Describe the principal seismic design requirements for beam-column joints.

4. Explain how irregularity, infill walls, and torsion can alter the seismic response of an RC building.

5. Discuss the relationship between construction quality assurance and the assumed seismic performance of a designed structure.

Analytical / Application Questions

1. A beam has probable end moments of 260 kN·m and 310 kN·m over a 5.5 m clear span, with 70 kN gravity shear acting in the critical direction. Calculate the capacity-design shear demand and state the assumptions used.

2. A six-storey building has an open ground floor and heavily infilled upper floors. Develop a diagnostic plan covering modelling, likely failure mechanism, and two alternative retrofit strategies.

3. A footing carries 1,200 kN axial load and a 300 kN·m overturning moment over a 2.5 m width. Calculate the eccentricity and, under the stated rigid-footing linear-contact assumptions, determine whether the calculated minimum pressure is compressive or tensile. Explain the limitation if uplift occurs.

Multiple Choice Questions with Answers

Question 1

What is the preferred yielding mechanism for a typical ductile RC moment frame?

A. Column shear failure before beam yielding

B. Beam flexural hinging with protected columns and joints

C. Joint crushing before any member yields

D. Foundation punching before frame deformation

Correct Answer: B. Beam flexural hinging with protected columns and joints

Question 2

Which component transfers inertial floor forces to vertical lateral-force-resisting elements?

A. Diaphragm

B. Column splice only

C. Isolated footing only

D. Expansion joint

Correct Answer: A. Diaphragm

Question 3

For a beam with probable end moments of 240 kN·m and 300 kN·m over a 6 m clear span, and 60 kN gravity shear, the capacity-design shear in the additive direction is:

A. 90 kN

B. 120 kN

C. 150 kN

D. 600 kN

Correct Answer: C. 150 kN

Question 4

Why is transverse reinforcement closely spaced in RC column hinge regions?

A. To eliminate all axial load

B. To confine concrete, restrain bars, and support cyclic ductility

C. To reduce concrete cover to zero

D. To prevent every crack from forming

Correct Answer: B. To confine concrete, restrain bars, and support cyclic ductility

Question 5

A dual seismic system combines:

A. Two different concrete mixes only

B. Moment frames with walls or another primary lateral system

C. Gravity beams with plumbing walls only

D. A diaphragm with a foundation slab only

Correct Answer: B. Moment frames with walls or another primary lateral system

Question 6

If a footing has axial load N = 1,000 kN and overturning moment M = 250 kN·m, its eccentricity e = M/N is:

A. 0.025 m

B. 0.25 m

C. 2.5 m

D. 4.0 m

Correct Answer: B. 0.25 m

Question 7

Which is a brittle seismic failure mode?

A. Stable beam flexural yielding

B. Controlled wall rocking designed for the system

C. Diagonal shear failure after flexural overstrength develops

D. Recoverable elastic deformation

Correct Answer: C. Diagonal shear failure after flexural overstrength develops

Question 8

The interstorey drift ratio is calculated as:

A. Storey shear divided by mass

B. Relative floor displacement divided by storey height

C. Base moment divided by footing area

D. Axial force divided by beam span

Correct Answer: B. Relative floor displacement divided by storey height

Question 9

A major risk of an open ground storey beneath stiff infilled floors is:

A. Uniform drift in every storey

B. Concentration of drift and damage in the ground storey

C. Elimination of torsion

D. Automatic improvement of column ductility

Correct Answer: B. Concentration of drift and damage in the ground storey

Question 10

Which statement best describes responsible use of AI in seismic engineering?

A. AI output replaces code compliance and professional review

B. AI may assist analysis or inspection but requires engineering verification

C. AI guarantees accurate prediction for every building type

D. AI removes the need for construction inspection

Correct Answer: B. AI may assist analysis or inspection but requires engineering verification