(SEM VIII) THEORY EXAMINATION 2017-18 EARTHQUAKE RESISTANT DESIGN OF STRUCTURES

EARTHQUAKE RESISTANT DESIGN OF STRUCTURES (NCE-064)

According to the uploaded question paper 

The Earthquake Resistant Design of Structures examination is divided into three sections: A, B, and C. The paper is structured to test fundamental seismology concepts first, then structural dynamics and design principles, and finally advanced vibration analysis and failure mechanisms.

Below is a detailed explanation of each section in descriptive format.

Section A – Fundamental Seismology and Structural Basics (20 Marks)

Section A consists of ten compulsory short-answer questions, each carrying two marks. This section focuses on fundamental concepts related to earthquakes and structural behavior during seismic activity.

The questions include drawing the Earth’s mantle, defining body wave magnitude, identifying basic elements of a vibrating system, types of damping, difference between tsunami and normal sea wave, Modified Mercalli (MM) scale, soft storey failure, non-structural elements, masonry failure modes, and factors affecting ductility.

This section tests your understanding of both geological and structural fundamentals. For example, the basic vibrating system consists of mass, stiffness, and damping. Soft storey failure refers to collapse of a floor with significantly less stiffness compared to other floors. Ductility is influenced by material properties, reinforcement detailing, confinement, and loading conditions.

Although the answers are short, they require conceptual clarity in earthquake engineering principles.

Section B – Structural Dynamics and Design Considerations (30 Marks)
 

Section B requires you to attempt any three questions, each carrying ten marks. This section combines structural mechanics with earthquake-resistant design concepts.

Topics include differentiation between strike-slip and dip-slip faults, calculation of natural period of a system, effects of structural irregularities, advantages and disadvantages of masonry construction, and design of confining spiral ties for a circular column.

For example, the natural period question requires understanding of single-degree-of-freedom systems and vibration theory. The structural irregularities question requires explaining plan irregularity, vertical irregularity, mass irregularity, and stiffness irregularity with neat sketches.

The spiral tie design question involves reinforced concrete design principles, where confinement improves ductility and seismic performance.

This section evaluates structural dynamics knowledge and practical design skills under seismic loading.

Section C – Advanced Seismic Analysis and Failure Mechanisms (50 Marks)

Section C carries the highest weightage and requires you to attempt one part from each question. This section focuses on advanced seismic wave theory, vibration analysis, damage mechanisms, and irregularities in buildings.

Topics include seismic waves with diagrams, tectonic plate theory and major plates, damping calculation using logarithmic decrement, causes and characteristics of earthquakes, natural frequency of two-degree-of-freedom systems (as shown in the diagram on page 2), damage and failure of bearing walls, improvement of seismic behavior of masonry buildings, in-plane and out-of-plane failure of masonry walls, and mass and geometric irregularities.

For example, in the damping problem, you must calculate logarithmic decrement using amplitude reduction over cycles. The natural frequency problem involves solving eigenvalue equations for a two-degree-of-freedom system with given masses and stiffness values (as illustrated in the diagram on page 2 of the paper).

When explaining seismic waves, you should describe P-waves, S-waves, and surface waves (Love and Rayleigh waves). In masonry failure discussion, you must differentiate between in-plane shear failure and out-of-plane bending failure.

This section evaluates deep understanding of structural dynamics, vibration analysis, and seismic damage mechanisms.

 Overall Paper Structure and Preparation Strategy

The paper is structured progressively:

Section A tests basic seismology and structural concepts.

Section B evaluates vibration theory and seismic design practices.

Section C examines advanced vibration analysis, failure mechanisms, and irregularity effects.

To score well:

Understand basic vibration theory (mass–spring–damper system).

Study seismic waves and tectonic plate theory.

Practice natural frequency and damping calculations.

Learn masonry failure mechanisms and structural irregularities.

Focus on ductility and confinement design concepts.