*JU774*

JU – 774

VIII Semester B.E. (Civil) Degree Examination, Jan./Feb. 2014 (2K6 Scheme) CE 801 : FUNDAMENTALS OF EARTHQUAKE ENGINEERING Time : 3 Hours

Max. Marks : 100

Note : 1) Answer any five full questions. 2) Use of IS: 1893-2002 code is permitted. 3) Additional data if required may be suitably assumed. 1. a) A single degree of freedom system is subjected to free vibrations. Obtain the general solution for the undamped natural frequency of the system.

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b) An empty elevated water tank is pulled by a steel cable by applying a force of 30 kN. The tank is pulled horizontally by 50 mm. The cable is suddenly cut and the resulting free vibration is recorded. At the end of five complete cycles of vibrations, the time is 2 seconds and the amplitude is 20mm. Determine a) Damping ratio b) Natural frequency of undamped vibration c) Effective stiffness d) Effective weight and e) Damping coefficient.

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2. a) Explain logarithmic decrement with its practical significance. For a system with damping ratio of 3.7%, determine the number of free vibration cycles required to reduce the displacement amplitude to 10% of the initial amplitude if the initial velocity is zero.

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b) What is magnification factor ? Show that maximum magnification occurs at resonance condition.

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3. a) List and explain the various types of vibration isolation techniques and discuss about the effectiveness of vibration isolation.

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b) The total weight of a machine inclusive of foundation is 450 kN. The soil stiffness and damping ratio may be assumed as 75×103 kN/m and 0.5 respectively. An exciting force F(t) = 6 sin25t induces vertical vibrations in the machine. Find the amplitude of vertical displacement.

10 P.T.O.

*JU774*

JU – 774

4. a) Explain the various strong ground motion parameters indicating their practical significance. 10 b) What is the significance of moment magnitude scale of measuring an earthquake ? During a major earthquake, the depth of fault rupture was estimated to be 18 km, the length of surface faulting was determined to be 700 km and average slip along the fault is 2.8 m. Based on these measurements, determine the magnitude of the earthquake in terms of moment magnitude, 10 Use a shear modulus of rock equal to 4×1010 N/m 2. 5. a) Explain how dynamic problems are solved by Wilson- θ method.

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b) A single degree of freedom system subjected to a pulse loading has m = 6 kg, k = 5000 N/m, and c = 3 N-s/m. The excitation force of 1000 kN. Initial velocity and displacements are zero. Obtain the displacement history using 10 Wilson- θ method. 6. a) Bring out clearly the difference between response spectra and design response spectra of an earthquake motion highlighting their practical significance.Also explain how a smooth response spectra cab be developed. 10 b) Discuss about the factors that influence earthquake resistant design of structures.

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7. a) Explain (a) Maximum considered and design basis earthquakes (b) Principles of seismic design approach.

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b) A two bays and three storey RCC school building is to be constructed in seismic zone V. The foundation soil is medium stiff. The storey height is 3.5 m. and bay width is 4 m. It is proposed to design the building with a special moment resisting frame with brick infill. The load from the roof is 740 kN and the load from each floor is 788 kN. Determine the design seismic load on the structure as per 1893-2002 and distribute the seismic load along the height of the building. Also sketch the shear force diagram for whole height of the building. 12 8. Write short notes on any four of the following : i) Degrees of freedom iii) Newmark method

ii) Earthquake magnitude iv) Body waves

v) Surface waves. ———————

(4×5=20)