Building Damage Assessment - GeoSS Event Seminar 10 Nov 2009_slides

8/23/2019 Building Damage Assessment - GeoSS Event Seminar 10 Nov 2009_slides

1/41

1

Wen Dazhi, BSc, PhDPE, PE(Geo), AC(Geo), CE, MICE, MIEAust, CPEng

BUILDING DAMAGE ASSESSMENT

amage ca egor es

Basis of damage assessment

Staged design approach and design assumptions

Case studies of buildings on mixed foundations

GeoSS 10112009 2


2/41

2

DAMAGE CATEGORIES

1) Visual appearance or aesthetics;

2) Serviceability or function; and

GeoSS 10112009 3

3) Stability.

DAMAGE CATEGORIESCategory Typical crack

width (mm)Effects

Negligible 0.1mm Hairline cracks only

25mm Beams lose bearing, walls requireshoring. Windows broken withdistortion. Danger of instability.


3/41

3

DAMAGE CATEGORIES

Category Typical crackwidth (mm)

Repair

Negligible 0.1mm Hairline cracks only

V. Slight 25mm Major repairing work involvingpartial or complete rebuilding.

AS2870 DAMAGE CLASSIFICATION

FOR WALLS

Description of typical damage and required repair Approximatecrack width limit

Damagecategory

Hairline cracks


4/41

4

AS2870 - DAMAGE CLASSIFICATION

FOR CONCRETE FLOORS

Description of typical damage Approximate crack width limitin floor

Changein offset

Damagcate or

Hairline cracks, insignificantmovement of slab from level.


5/41

5

Not economic to restrict to no damage.

DAMAGE CATEGORIES

Typically allow up to slight damage for

most structures.

Restrict to very slight damage for

GeoSS 10112009 9

significance, such as heritage buildings.

BASIS OF BUILDING DAMAGE

ASSESSMENT

r er on or onse o v s e crac ng:

Limiting tensile strain.

Local strain at onset of cracking much

GeoSS 10112009 10

sma er an m ng ens e s ra n.


6/41

6

MODES OF MOVEMENT

- NOT DAMAGING

GeoSS 10112009 11

UNIFORM

SETTLEMENTUNIFORM TILT

RIGID BODY TILT

GeoSS 10112009 12


7/41

7

MODES OF MOVEMENT

- DAMAGING

GeoSS 10112009 13

BENDING/SHEARHORIZONTAL

EXTENSION

MODES OF MOVEMENT - DAMAGING

AND

SHEARSTRAINS

THAT

GeoSS 10112009 14

DAMAGE


8/41

8

LIMITING TENSILE STRAIN VS DAMAGE

CATEGORIES FOR MASONRY BUILDINGS

Limiting tensile Damage Class Typical crackstrain (%) width (mm)

0.0 - 0.05 Negligible


9/41

9

TOTAL CALCULATED STRAINS

Horizontal strain and the bending strain

Horizontal strain combined with diagonal

strain using a Mohrs circle of strain.

GeoSS 10112009 17

INTERACTION DIAGRAM, /L, h & L/H

GeoSS 10112009 18


10/41

10

Stage 1 - if settlement


11/41

11

ASSUMPTIONS FOR STAGE 2

Building simply follows the green fieldsettlement.

Building is made of masonry.

Settlements due to consolidation are even,and do not induce bending or horizontal

strain.

GeoSS 10112009 21

First two assumptions are consideredconservative i.e. they over-predict strainand damage.

STAGE 3 ASSESSMENT

Refinement of Stage 2 assessment.

Foundation details are considered.

Ground beams will reduce horizontalextension to a negligible value.

Piles will reduce settlements and

GeoSS 10112009 22

.

Continuous foundations, e.g. strip

footings or rafts are less prone to

damaging differential settlements.


12/41

12

STAGE 3 ASSESSMENT

ec s o so -s ruc ureinteraction: building stiffness will

modify Green Field settlements,

typically making them wider and

GeoSS 10112009 23

.

BUILDING DAMAGE ASSESSEMENT SUMMARY SHEET

Project/ Contract Number

Name of Building:

Address:

Description of Structure:

PHOTO

Description of Foundations

Drawings available YES/NO

Result of Preliminary AssessmentMaximum settlement:Maximum slope:

Second stage assessment required YES/NO

Summary

Sheet

GeoSS 10112009 24

Maximum settlement:Maximum ground slope:Maximum tensile strain:

Detailed evaluation required YES/NO

Detailed Assessment attached YES/NOProtection measures needed YES/NO

Protection measures proposed:


13/41

13

BUILDING DAMAGE ASSESSMENT

The theory works well in buildings on

uniform foundations.

Reliance should not be placed on

theoretical assessment alone.

Careful inspection of buildings should be

carried out. There would be tell-tale si ns

GeoSS 10112009 25

that indicate problems in the buildings.

Detailed structural assessment will be

necessary for those buildings.

CONSOLIDATION SETTLEMENTS -

COMMON ASSUMPTIONS

Consolidation settlements are generally

relatively uniform if the depth and

compressibility of the soft soils are uniform.

If uniform,consolidation settlements do not

GeoSS 10112009 26

cause tensile strain and do not cause damage.

Consolidation settlements commonly assumed

to have negligible effect.


14/41

14

CASE STUDIES OF BUILDINGS ON

MIXED FOUNDATION

For buildings on mixed foundations orfounded over varying depths of soft clay, the

common assumptions:

That it is conservative to assume that the

building moves with the ground

That consolidation settlements do not induce

GeoSS 10112009 27

significant differential settlement or tensilestrain

ARE NOT APPLICABLE

FOOCHOW METHODIST CHURCH

GeoSS 10112009 28


15/41

15

Sunda


School

Newkindergartensection

Old Church,wrapped inextension

GeoSS 10112009 29

Farrer Park StationLittleIndiaStation Cut & cover tunnel

RaceCourseRoadRotan Lane


Foochow Methodist ChurchKerbau Road RaceCourseLane Kinta Road Robert LaneRoad

N

LittleIndiaStation Farrer Park StationCut & Cover TunnelBored Tunnel Bored Tunnel

GeoSS 10112009 30

Old Alluvium

Kallang Formation

J urong Formation

90.00

70.00

80.00

100.00


16/41

16

FOOCHOW

METHODIST

CHURCH

GeoSS 10112009 31

17.5m

105

-40 -20 0 20 40 60 80 100

Deflection (mm)

l

-10 0 10 20 30 40 50 60

Deflection (mm)


75

85

95

Red

uced

Leve

90

100

Reduced

Level

GeoSS 10112009 32

55

65

PredictedMeasuredFormation Level

70

80

PredictedMeasuredFormation Level


17/41

17

1ststrut00


Consolidation settlement

2ndstrut3rdstrut

4thstrut

5thstrut

6thstrut

5

10

15

20

25

50

100(mm)

Settlement at final excavation level

GeoSS 10112009 33

30

35

(m)

40 20 0 (mm)

Wall deflection at finalexcavation level

base slab


0

20

40

1 10 100 1000Days

t(mm Excavation at 3rdstrut level

60

80

100

120

Settlemen Excavation resumed

from 3rdto 4thstruts

Excavation at finalformation

-212-Sep-9

8

11-Nov-9

8

10-Jan-9

9

11-Mar-9

9

10-May-9

9

09-Jul-99

07-Sep-9

9

06-Nov-9

9

05-Jan-0

0

05-Mar-0

0

04-May-0

0

03-Jul-00

01-Sep-0

0

31-Oct-0

0

30-Dec-0

0

28-Feb-0

1

29-Apr-01

28-Jun-0

1

27-Aug-0

1

GeoSS 10112009 34

0

2

4

6

8

10

Drawdown(m

GWP3071 GWP3081 GWP3051-1 GWP3051-2 GWP3051-3

Excavation completed and baseslab cast


18/41

18


RaceCourseRoadStruts for cut & covertunnel

Kindergartenon H-steel piles

3-storey sanctuaryon pad footings

ton to t esanctuary on H-steelpiles

. m

GeoSS 10112009 35

RotanLane

Sunday Schoolon Bakau piles

Chander L ane


Moderate toComputer

Severe

damage

(12mm crack)

at 15mm

settlement,

Room

GeoSS 10112009 36

e ore

excavation

started


19/41

19


GeoSS 10112009 37

Computer Room

-Nov-98

-Dec-98

-Jan-99

-Feb-99

-M

ar-99

-Apr-99

-M

ay-99

-Jun-99

-Jul-99

-Aug-99

-Sep-99

-Oct-99

-Nov-99

-Dec-99

m)


0

10

20

30

05

05

05

05

05

05

05

05

05

05

05

05

05

05

lSettlement/Cra

ckwidth(

GeoSS 10112009 38

40

50Differentia

CME404 CME405 CMA3641 CMD3772 Differential Settlement

Second Floor Third Floor First Floor First Floor Between L351 / L381


20/41

20


0.00E+00

5.00E-04

1.00E-03

05-Nov

-98

05-Dec

-98

05-Jan-9

9

05-Feb

-99

05-Mar

-99

05-Apr

-99

05-May

-99

05-Jun-99

05-Jul-9

9

05-Aug

-99

05-Sep

-99

05-Oct-99

05-Nov

-99

05-Dec

-99

otation(Radiant)

GeoSS 10112009 39

. -

2.00E-03

R

Rotation (Radiant) TM3211


GeoSS 10112009 40

Junction of Sunday

School and

Kindergarten


21/41

21


Original building

pos onNeighbouring

unit

GeoSS 10112009 41

For buildings in a terrace, rigid body tilting will lead to

tearing at the junction with the neighbour unit.

posi tion

148 RACE COURSE ROAD

GeoSS 10112009 42


22/41

22


No 148 Race

Course Road

No 146

GeoSS 10112009 43Shirlaw, Wen, Algeo & Patterson-Kane (2003)


Settled by 107mmNo 146, piled

GeoSS 10112009 44

Building tilting away

from the adjacent

structure


23/41

23


GeoSS 10112009 45


GeoSS 10112009 46

Adjacent buildings on different foundations: Old buildings on footings

butted against newer buildings on deep foundations.


24/41

24

Original building


posi tion

Settled building

GeoSS 10112009 47

Racking action causes damage, in particular at door /

window frames / arches.

Masjid Wak Tanjong

GeoSS 10112009 48


25/41

25

Masjid Wak Tanjong

GeoSS 10112009 49

Masjid Wak Tanjong

Cross

Walls

GeoSS 10112009 50

CCL Paya Lebar

Station D/W Layout


26/41

26

Masjid Wak Tanjong

GeoSS 10112009 51

Interface between Kallang Formation and OA

Excavation Level: RL85.7m

Masjid Wak Tanjong

Typical

Excavation

Sequence16.7m

GeoSS 10112009 52


27/41

27

Masjid Wak Tanjong

GeoSS 10112009 53

Masjid Wak Tanjong

GeoSS 10112009 54


28/41


29/41

29

Masjid Wak Tanjong

in piezometric level:

At 9m below ground: 1.5m

At 15m below ground level: 3m

GeoSS 10112009 57

27m below ground level: 6m

20/03/03 01/08/04 14/12/05 28/04/07 09/09/08

Masjid Wak Tanjong

-70.00

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

0.00

GeoSS 10112009 58

-90.00

- .

505 519 520

Building Settlements


30/41

30

Masjid Wak Tanjong

GeoSS 10112009 59

Masjid Wak Tanjong

GeoSS 10112009 60


31/41

31

Masjid Wak Tanjong

GeoSS 10112009 61

Part of the building on piles and part on footings

Damaging at small differential settlements.

Other Examples

GeoSS 10112009 62


32/41

32

GeoSS 10112009 63

Annex structureon footings

abutting buildings

on piles

PiledFootings

GeoSS 10112009 64

CIRCLELINESTAGE 1

Nicoll Highway Station

FILL (6.5m THICK)

SOFT MARINE CLAY

(33m THICK)

OLD ALLUVIUM


33/41

33

GeoSS 10112009 65

Singsation

GeoSS 10112009 66

.

SOFT MARINE CLAY

(33m THICK)

SANDY OLD ALLUVIUM

SETTLEMENT


34/41

34

STAR SINGSATION KTV CLUB

GeoSS 10112009 67

GeoSS 10112009 68

Walkway - piled

Main load bearing

column - shallow

foundations


35/41

35

No 7 CANTONMENT ROAD

136mm 72mm 55mm 20mm 9mm72mm

No 7 No 9

GeoSS 10112009 69

Fill & Organic clay Weathered Jurong Formation

Shirlaw, Wen, Algeo & Patterson-Kane (2003)




36/41

36


Party Wall

to No 9


Buildings over varying depths of soft

clay - usually a terrace problem

GeoSS 10112009 72

Pocket of soft clay


37/41

37

GeoSS 10112009 73

GeoSS 10112009 74


38/41

38

POSSIBLE MEASURES

o en y u ngs a are unusua ysensitive to settlement

To carry out protective measures

GeoSS 10112009 75

IDENTIFICATION

To identify buildings on mixed foundations -

A&A drawings

To identify locations of variation in geology, in

particular along terrace houses

GeoSS 10112009 76

A general walk around the site building

inspection


39/41

39

IDENTIFICATION

Look at the geological profile / soilinvestigation data - consolidation often

(marine/estuarine)

Sensitive buildings often show some signs ofdamage or repair - existing cracks / spalling

Watch out for additions to old buildings or new

GeoSS 10112009 77

buildings abutting old buildings With terrace houses, signs of local dips in theroof line, local settlements in the road outside

or local damage to drains / aprons

PROTECTIVE MEASURES

Recharge wells to control consolidation-

tight wall and with wells installed before

excavation starts)

Separate the parts of the structure on differentfoundations

GeoSS 10112009 78

Prop (where necessary for safety) and repairafterwards

Underpinning


40/41

40

Methods of Mair, Taylor and Burland to be

CONCLUSIONS

.

Stage 1 - if < 10mm, no need to considerfurther

Stage 2 - green field assessment. Assumes

GeoSS 10112009 79

Stage 3 - Detailed evaluation, taking intoaccount building stiffness and foundations

CONCLUSIONS

Buildings on mixed foundations are

extremely sensitive to settlement and more

susceptible to damage than other buildings.

GeoSS 10112009 80

foundations are required.


41/41

THANKS

GeoSS 10112009 81

Building Damage Assessment - GeoSS Event Seminar 10 Nov 2009_slides

Documents

Transcript of Building Damage Assessment - GeoSS Event Seminar 10 Nov 2009_slides