Earthquake Engineering EGCE 305

Earthquake Engineering EGCE 305

Earthquake Impact on Structures

Michael Mann

Week 8

Class Schedule

Aug 26 Plate tectonics and faults, causes of earthquake

Sep 02 NO Class (Campus Closed)

Sep 09 Strength of shaking – what controls it?

Sep 16 Predicting shaking

Sep 23 Ground failure,

Sep 30 Historical earthquake damage, Exam 1

Oct 07 California seismic rules and regulations; life safety issue

Oct 14 Building & bridge performance; effect of faults on structures

Oct 21 Performance of schools, hospital, and other types of structures

Oct 28 Retrofitting buildings & bridges, preventing non-structural damage

Nov 04 Impact of earthquakes on society; large structures & high-rises, Exam

Nov 11 NO Class (Campus Closed)

Nov 18 Damage in recent California earthquakes; reconstruction

Nov 25 Fall Recess (No Class)

Dec 02 Building safety for moderate & severe earthquakes

Dec 09 Mitigation earthquake hazard; summary

Dec 16 Final Exam (7:30-9:20 pm)

Information from the book Peace of Mind in Earthquake Country by Yanev and Thomposon, 2008.

AND myself unless otherwise noted

Structures

Major structural elements of a building are as follows

Distributing Structural Elements – roof, floors, beams, trusses

Resisting Structural Elements – walls, columns, bracing

Foundation – transfers the weight of the structure to the earth

Connections – nails, blocking, joints, connect all the elements together.

FEMA

Foundations

Large structures

Slab (also called Mat foundation)

Piles

Footings

Houses

Slab

Crawl-space – typically for houses

Foundations must be designed by …

Engineer – designs what type of foundation based on load from the building, soil/rock type, earthquake loading, etc..

Geologist – Tells Engineer what type of soil/rock conditions are under the site, landslide risks, bearing capacity (how much weight the ground can hold), etc..

Foundations

Foundation connections are vitally important for the performance of a structure during an earthquake.

Large buildings – usually the building is will be directly bolted or rebar to the slab, pile, or footing

Houses – need good connections and reinforcement

Slabs

make sure the houses is firmly bolted/nailed to the slab foundation

Crawl-space foundations

make sure the house is bolted/nailed to the existing siding

Make sure the siding of the crawl-space is reinforced with shear walls

Consult with a licensed contractor or engineer

Earthquake damage

Because earthquake loading acts from the Horizontal direction, the most common types of earthquake damage

Sliding off foundation

Walls, columns can break or crack

Connectors between floors and walls/columns failing

Bracing

For the walls and columns, we need bracing to distribute the earthquake load

for wooden structures, the bracing can be made of wood, steel, or concrete. For all other types of structures the bracing is made of steel, concrete, or masonry

Frame – adds strength to the columns, is flexible

Shear Walls – solid continues wall, stiff, non bending, transfers loads to foundation, does not look as good

Diagonal or X-Bracing – adds strength and stiffness, transfers loads to foundation, looks better

https://www.air-worldwide.com/siteassets/airimages/publications/air_currents/2017/images/mfghomes_eq_fig2.gif

https://lh3.googleusercontent.com/proxy/fbZrLTzyt5hRVNAXU88Fegi5KbMzPHXhLz20hDJMQxrMchzQKBMFzOL6Z5DIee79onZm5rrq8hxcWDif3xboOscc5vT5yVRvfsaV0kPO-x__sPbbtmqxTTZxMQDGpaVbi5QGkbfpBJQoSp4MR-0qVw

https://qph.fs.quoracdn.net/main-qimg-d5343cf055791e091fe5fb61e00c9545.webp

Overview

In general, the problem with different types of structures stem from the following factors

The best structures in an earthquake are made from materials that are strong but not brittle and that are flexible but not too flexible.

The cost element is always a factor, which is part of way we have codes to keep everyone honest.

Wood Frame Buildings

Constructed of wood materials, usually connected with metal nails

Pros: Lightweight, flexible, one of the best for earthquake resistance.

Retrofit/supports

Use plywood for shear walls, lateral bracing,

Cons: poor performance if…

Built on unstable, soft ground

Old construction

Not bolted to foundation

No bracing in crawl-space or cripple walls

No lateral bracing

Heavy roof

Soft story

Wood Frame Buildings

Other factors – Veneer

Stuccoed walls – can crack and break

Masonry Veneer – can crack, fall

http://www.understandconstruction.com/uploads/1/7/0/2/17029032/9522746_orig.jpg

https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcSetk0wAdQO4gGqYlOjSb9wkQpOxnUPXU1slWTApE6rvNBhxdnJ

Concrete block buildings

Constructed of concrete blocks that are stacked with the blocked connected with mortar. Properly constructed with rebar and concrete in the holes of the blocks.

Retrofit – steel frames,

Pros: cheap, strong, act as shear wall

Cons: poor performance if…

If not constructed properly, can fall apart

Old construction

https://s3-us-west-1.amazonaws.com/contentlab.studiod/getty/34565dbc533a4fbda21a58898585fc06.jpg

https://www.nbmcw.com/images/nbm-media/Articles/Precast-Construction/37557-heat-ingress.jpg

https://www.mercurynews.com/2019/07/12/newer-smaller-buildings-may-have-limited-ca-quake-damage/

 

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Earthquake Engineering EGCE 305 was first posted on March 24, 2020 at 9:36 am.
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