DrSaid1 Structural Dynamics

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Lecture 1:Structural DynamicsConcepts, Design and Implementation

4th year Final Project

Structural Engineering Project

Dr. Said El-kholy


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Structural Dynamics

Introduction

What is Dynamic Loading?

Structural Dynamics

Concepts

Seismic Loadings Method, Codes

Prevention

Advancements

Responsibilities as Engineer, Architect Introduction to TMD


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Inside Earth


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Geographical Plates Location


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Slips and Faults


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Slips and Faults


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Intensity Measuring Instruments


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Tsunami Attack


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Effect of Earth Quake


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Resonance of Structure


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Soft Story

A common buildingdesign flaw is to make thefirst story much moreflexible than the upper stories. During anearthquake the upper floors tend to move as aunit while the first floor flexes a great deal. Thiscan cause collapse of thefirst floor, as happenedduring to some apartmentbuildings during the 1994

Northridge earthquake inCalifornia


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Seismic basics


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Intensity of Earth Quake


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Many building collapses during earthquakes may be

attributed to the fact that the bracing elements, e.g.

walls, which are available in the upper floors, are

omitted in the ground floor and substituted by

columns. Thus a ground floor that is soft in the

horizontal direction is developed (soft storey). Often

the columns are damaged by the cyclic displacementsbetween the moving soil and the upper part of the

building. The plastic deformations (plastic hinges) at

the top and bottom end of the columns lead to a

dangerous sway mechanism (storey mechanism) with a

large concentration of the plastic deformations at the

column ends.


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Asymmetric bracing is a frequent cause of building

collapses during earthquakes. In the two above sketches

only the lateral bracing elements are represented

(walls and trusses). The columns are not drawn

because their frame action to resist horizontal forces

and displacements is small. The columns, which only

have to carry the gravity loads, should however be able

to follow the horizontal displacements of the structure

without loosing their load bearing capacity.


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Large re-entrant corners creating a crucifix

form would mean irregular configuration.


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CENTRE OF MASS CENTRE OF

STIFFNESS

ECCENTRICITY


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PLAN IRREGULARITIES


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VERTICAL IRREGULARITIES -

STIFFNESS


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VERTICAL IRREGULARITIES - MASS

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DrSaid1 Structural Dynamics