ENGINEERING TRIPOS PART IIB - 2011/2012

Module 4D6 - Dynamics in Civil Engineering

AIMS

This module is an introduction to the behaviour and design of civil engineering structures subjected to time-varying loads. Earthquake-resistant design, dynamic soil-structure interaction, machine foundation design, blast effects on structures and the fundamentals of wind engineering will be introduced.

LECTURE SYLLABUS

STRUCTURAL DYNAMICS (4L)

Linear Elastic Dynamics

• Introduction to dynamic loads in Civil Engineering; dynamic amplification factors.
• Approximate single-degree-of-freedom analysis of complex structures; sway frames; structures with distributed mass.
• Rayleigh's principle; natural frequency of simple systems using energy methods.
• Linear models to represent structures and their relevance; analysis in frequency domain; mode superposition method.
• Modal analysis of vibration; use of finite element packages.

Non-linear Systems

• Sources of nonlinearity in structures and foundations.
• Analysis in time domain; numerical integration of equations of motion.

APPLICATIONS OF DYNAMICS IN CIVIL ENGINEERING STRUCTURES

PART A: Soil-Structure Interaction (5L)

Machine foundations

• Machine-induced vibrations; active and passive vibration isolation.
• Simple analytical models; design of machine foundations with active isolation, protection of sensitive buildings with passive isolation.

Seismic design

• Earthquake loading on structures; response and design spectra.
• Structures subject top ground motion; deformations due to lateral accelerations; Newmark's sliding block analysis' concept of threshold acceleration.
• Foundations effects; stiffness of soil foundation and soil-structure interaction.
• Pore pressure build-up during earthquakes; partial liquefaction; degradation in soil stiffness; non-linear soil models.
• Liquefaction resistant design, simple examples.

PART B: Seismic resistant design, blast effects and wind engineering(5L)

Seismic resistant design

• Structural design and detailing considerations.

Blast loading

• Physics of blasts; blast effects on structures; blast-resistant design.

Wind loading

• Nature of wind.
• Wind forces on structures.
• Response of structures to buffetting. Fluid-structure interaction (vortex-shedding, galloping and flutter). Long-span bridge case study.

COURSEWORK

Seismic analysis of an existing tall building using the ABAQUS finite element package and a study of the effect of foundation softening on the overall structural response. Total time 8 hours.

OBJECTIVES

On completion of the module students should:

• Be able to identify cases where a static model of a structure is inadequate, and a dynamic model should be used;
• Be able to produce a simple estimate of the natural frequency and fundamental natural mode of any linear-elastic structure;
• Be able to estimate linear-elastic spring parameters for a given foundation;
• Be able to compute the natural frequencies and natural modes of structures using the ABAQUS package and include simple soil models to account for soil-structure interaction;
• Be able to estimate the response of complex linear-elastic structures to earthquakes using modal superposition and the response spectrum;
• Be able to use elastic and inelastic design spectra, and to understand their form;
• Be able to perform simple designs for vibration isolation;
• Be able to perform simplified soil stiffness calculations accounting for partial liquefaction, and to use this approach in simple liquefaction resistant designs;
• Be able to describe some standard methods of seismic-resistant structural design;
• Be able to describe blast processes and their effects on structures;
• Be able to appreciate the factors involved in the estimation of wind climates and of structural response to wind;
• Be able to understand the various measures that characterise atmospheric turbulence;
• Be able to anticipate the circumstances under which aeroelastic phenomena may be problematic;
• Be able to estimate the dynamic response of a tall structure in a given wind environment;

REFERENCES

Please see the Booklist for Group D Courses for references for this module.

Last updated: August 2011