MCEGS203 Dynamics of Soil & Design of Machine Foundations M.Tech Model Question Paper : mgu.ac.in
Name of the University : Mahatma Gandhi University
Department : Civil Engineering
Degree : M.Tech
Subject Code/Name : MCEGS 203/Dynamics Of Soil And Design Of Machine Foundations
Sem : II
Website : mgu.ac.in
Document Type : Model Question Paper
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Dynamics of Soil & Design of Machine Foundations :
M.TECH. Degree Examination :
Model Question Paper – II :
Second Semester
Related : MGU MCEGS201 Ground Improvement Techniques M.Tech Model Question Paper : www.pdfquestion.in/5257.html
Branch: Civil Engineering
Specialization: Geomechanics and Structures
MCEGS 203 Dynamics Of Soil And Design Of Machine Foundations :
(Regular – 2011 Admission onwards)
Time: 3 Hrs
Max Marks: 100
Answer all Questions :
Assume suitable data wherever necessary :
1. a) Explain the terms, damped natural frequency, magnification factor and logarithmic decrement. (4 X 3 = 12)
b) A foundation block of weight 30 kN rests on soil for which stiffness may be assumed as 25000 kN/m. The machine is vibrated vertically by an exciting force of 3Sin 30t kN. Find the natural frequency, period, natural circular frequency and the amplitude of vertical displacement. (13)
OR
2. From first principles obtain the equation of motion for over damped, critically damped and under damped systems. (25)
3. a) Describe the development of mass spring dashpot model from elastic half space theory. (12)
b) In a block test according to Indian standards, resonant frequency of 18 Hz was observed in the vertical direction. The base size of concrete test block was 1.5m X 0.75 m. The thickness of the block was 0.75m. Unit weight of concrete = 24kN/m3. Determine Cu. If a machine weighing 100kN is to be supported on a rigid block 6m X 8m X 2.5m, what is the natural frequency in the vertical direction? (13)
OR
4. a) Describe the methods of determining the damping factor. (12)
b) The following data refer to vertical vibration test conducted for a compressor foundation of size 10m X 8m in contact with soil. Size of M15 concrete block used in 1.5m X 0.75m X 0.7m. fm?=35Hz, Xm? = 0.06375m, ?= 0.3. Find E. (13)
5. Starting from fundamentals derive the expression for natural frequencies and amplitudes for block foundation subjected to horizontal forces FxSin?t and a moment MySin?t at the combined center of gravity of machine and foundation. (25)
OR
6. A concrete block shown in figure is used as foundation for a reciprocating engine operating at 500rpm and mounted symmetrically with respect to the foundation. The weight of the engine is 10kN.
It is likely that the operation of the machine exerts the following.
Unbalanced vertical force = 1.8 Sint kN.
Unbalanced moment = 6 Sin t kNm.
The values of dynamic elastic constants are Cu=4.5 X 104kN/m3. G= 4.8 X 104kN/m2, µ= 0.34, ?soil=17 kN/m3, ?concrete=24 kN/m3. Determine the natural frequencies and amplitude of the block by linear elastic spring mass approach. (25)
7. a) Write a detailed description of vibration isolation and isolation materials. (12)
b) Discuss the criteria for design of impact type machines. (13)
OR
8. Design a hammer foundation for following specifications.
i) Soil at site – Clay soil mixed with some sand and silt.
ii) Static allowable bearing pressure = 20 T/m2
iii) Elastic uniform compression with correction applied CuI= 3Cu = 12 X 103 T/m3
iv) Weight of dropping parts = 3.5T
v) Height of drop = 100cm
vi) Piston area = 0.15m2
vii) Base area of anvil = 4.75m2
viii) Thickness of pad under anvil = 60cm
ix) E of pad = 50 X 103 T/m2
Determine :
a) Amplitude of vibration of foundation and anvil
b) Amplitude of anvil together with frame
c) Dynamic stress in the pad under anvil (25)
Syllabus :
Module 1 :
Introduction to Soil Dynamics Vibration of elementary systems- free and forced vibration with and without damping, Analysis of systems with Single degree and multi-degree of freedom. Natural frequencies of continuous systems, resonance . Effect of vibration on soil properties.
Module 2 :
Bearing capacity of dynamically loaded foundations .Nature of dynamic loads -stress conditions on soil elements under earthquake loading -methods of analysis of machine foundations -methods based on linear elastic weightless springs methods based on linear theory of elasticity (elastic half space theory) -nature of damping -geometric and internal – Elastic Constants of soil and their experimental determination.