ce 555-l23-24-ndt of wood masonry

8/17/2019 CE 555-L23-24-NDT of Wood Masonry

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Neithalath , Spring 2006, CE 455/555 Structural Damage: Assessment, Repair, and Strengthening

NDT and Evaluation of Timber andMasonry Structures

Lectures 22,23


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Timber structures


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Visual grades of lumber

http://www.woodtruss.com/projects/


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Visual grade stamps

Assigned grade

Species group

Moisture contentdesignation

Mill ID

Gradingagency



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Machine graded lumber

Machine stress rated (MSR)lumber

Each piece is non-destructivelytested

Bending test and E beforesubjected to visual examination

Machine evaluated lumber(MEL)

Also subjected to NDT

Grades M-5 (lowest) to M-28(highest)

Assigned to no particularproperty

Bending stress 2400 psiE = 2.0 million psi



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Visual inspection of wood damage

Fruiting bodies on the surface (fungi etc)

Sunken faces Localized depressions

Staining, discoloration

Moisture effects

Bulging at beam supports

Reduces bearing capacity of wood Insect infestation – wood powder

Plant or moss growth (moisture)


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Probing and Pick test

Probing

Locate soft areas using a pointed tool If easily removable or penetrable, defect might

exist

Relative test Pick test

Driving a metal pick or screwdriver

Bending the tool back to pry off a small area

Good wood splinters in long silvers

Crumbling or breaking indicates decay


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Moisture meter for wood

Prongs driven into thewood

Resistance or a dielectricprinciple

Usually detects 4-40% ofmoisture


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Hammer sounding

Wood rapped with a hammer

Hollow sound, no rebound indicates somedecay

Inexact test


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Stress wave timing


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Stress wave paths and speeds

Timber Glulam beam


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ransmission time vs. Annual ring

orientation


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Relating comp stress, transmission

time and degradation


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Impact Echo


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Masonry structures


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Stress wave methods

Ultrasonic pulse velocity


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Stress wave methods

Impact test


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Impulse Radar testing

At Princeton University's Whig Hall

almost 100 years of weatheringand a fire caused extensive damageto the masonry portico

http://www.cr.nps.gov/

Impulse radar testing


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In-situ stress test

Determines the existingcompressive stress in themasonry

Accurately measure gage pointlocations

Remove bed joint – localizeddeformations

Insert a flat jack and exertlifting pressure to restore gagepoints

Approximately equals thecompressive stress in the wall

Unequal stresses on oppositesides can indicate presence offlexural stresses


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In-situ stress test


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In-situ shear test

To measure in-situ joint shear resistance

between masonryunits and mortar

Remove 1 masonryunit and head joint

Horizontal forceneeded to cause thefirst movement of test

unit noted


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Joints in Masonry


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In-situ deformability test

To estimate masonrycompressive modulus

Measures the stress-strain response ofmasonry

Mortar bed removed attwo levels and stressapplied using a flat jack

Stress increased

gradually, and thenunloaded


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In-situ deformability test


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Bond shear strength

Triplet test

τ = Fult /2A

ce 555-l23-24-ndt of wood masonry

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