assessing construction

Boone, S.J. (2001). Assessing construction and settlement-induced building damage: a return to fundamental principles. Proceedings, UndergroundConstruction, Institution of Mining and Metalurgy, London, 559 – 570.

1

Assessing construction and settlement-induced building damage: a return tofundamental principles

S.J. BooneGolder Associates Inc., Irvine, California, United States

Abstract

Assessing the potential for construction and settlement-induced building damage is critical forunderground and new building construction projects. Simplified criteria including “angular distortion”and “deflection ratio” have been used for this task; however these methods do not reflect the diversityof building structures or the effects of nearby construction. This paper summarises a method ofexamining the problem of building damage by combining ground deformation patterns, well-knowndamage category criteria, strain superposition and critical strain concepts.

Introduction

Settlement or heave of structures, whether from nearby construction or other causes, can result innoticeable damage. Such damage can be significant and costly. Usually, the most settlement sensitivebuildings are those with masonry load bearing walls or frames with masonry in-fill walls. Assessingthe potential for damage to new or existing structures has been the subject of many studies undertakenover the last 45 years. Simplified criteria including “angular distortion” and “deflection ratio” havebeen used for this task. Subsequent modifications to these methods have included horizontal strain asan additional criterion. These methods have been useful tools but they do not reflect the diversity ofbuilding structures or the effects of nearby construction. Such simplifications can over- or under-estimate the real potential for damage. The key problems with the common assessment methods are:

• the criteria are often very generalised;• multiple geometric definitions have been used for the “angular distortion” parameter;• new or existing buildings are constructed with a wide variety of dimensions;• clear definitions should be used when analysing potential building damage; and• the results of evaluations should have relevance to physically observable damage classifications.

By combining ground deformation patterns, well-known damage category criteria, strainsuperposition and critical strain concepts, the potential effects of building deformations can be readilyassessed without undue oversimplification.

Background

Skempton and MacDonald examined 98 case histories to identify a basis on which to determineallowable total and differential foundation settlements.1 Only 13 of these cases related to load-bearingwall structures, and over half of all the cases suffered no damage at all. From their work, theysuggested that “...the settlement characteristic causing cracking is probably the radius of curvature.But a characteristic which is more readily evaluated, and which is only slightly less logical, is theangular distortion; this conveniently expressed by the ratio of the differential settlement d and thedistance l between two points.” A preliminary limit of angular distortion of 1/300 was recommendedfor load bearing walls or masonry in-fill panels in frame buildings. No consideration was given to therelative length to height ratio of the affected parts of the structures. Categorisation of degrees ofdamage was limited to the distinction between “cracking” and “structural damage.” Meyerhof andBjerrum also utilised the “angular distortion” approach yet considered some influence of the buildingtype and dimensions and provided additional criteria.2, 3 An upper limit of angular distortion of 1/150was suggested by Bjerrum as the limit before structural damage could be expected.2 Within theliterature, many different simple parameters and definitions of “angular distortion” have been used(see Appendix A). Rigid-body tilt is sometimes neglected, either in published works or in practice.These approaches, while recognisably limited, are still often used in general practice and repeated intexts.


2

Burland and colleagues compared the behaviour of load bearing masonry walls undergoing settlementto the bending of a deep beam subjected to a point load at the beam centre.4, 5 They chose the ratio ofthe central deflection, ∆, and the equivalent beam length, l, to characterise structure deformation(deflection ratio), this being directly related to the “curvature”. It was generally considered that“hogging” deformation was more severe than “sagging” and the neutral axis for bending in “hogging”was considered to be at the bottom of the beam/wall. They then combined the equations for bendingof the deep beam and a “critical strain,” εc, to relate the onset of cracking to deformation and therelative height, H, and length of the deep beam (see Fig. 1). The critical strain was considered to beabout 0.03%. One of the more important aspects of their work included a summarisation of damageseverity based on observed crack width (see Table 1). This damage categorisation is widelyreferenced and is intuitive, practical, and related to measurable evidence. Yet, the deformation andcritical strain criteria were not directly linked to damage category.

DamageCategory

Description of Typical Damage ApproximateIndividual Crack

WidthNegligible (0) Hairline cracks < 0.1 mmVery Slight (1) Very slight damage includes fine cracks which can be easily treated during normal

decoration, perhaps an isolated slight fracture in building, and cracks in externalbrickwork visible on close inspection.

1 mm

Slight (2) Slight damage includes cracks which can be easily filled and redecoration wouldprobably be required, several slight fractures may appear showing the inside of thebuilding, cracks which are visible externally and some repointing may be required,and doors and windows may stick.

< 5 mm

Moderate (3) Moderate damage includes cracks that require some opening up and can be patchedby a mason, recurrent cracks that can be masked by suitable linings, repointing ofexternal brickwork and possibly a small amount of brickwork replacement may berequired, doors and windows stick, service pipes may fracture, and weather-tightness is often impaired.

5 mm to 15 mmor a number ofcracks > 3 mm

Severe (4) Severe damage includes large cracks requiring extensive repair work involvingbreaking-out and replacing sections of walls (especially over doors and windows),distorted windows and door frames, noticeably sloping floors, leaning or bulgingwalls, some loss of bearing in beams, and disrupted service pipes.

15 mm to 25 mmbut also dependson the number of

cracksVery Severe (5) Very severe damage often requires a major repair job involving partial or complete

rebuilding, beams lose bearing, walls lean and require shoring, windows are brokenwith distortion, and there is danger of structural instability.

> 25 mm

Table 1: Severity of Cracking Damage4, 5

Boscardin and Cording illustrated the importance of direct horizontal extension in initiating damage.6Fig. 2 illustrates the combination of angular distortion, defined in this case as the maximum change inslope along the “beam” or wall, and horizontal strain. Damage categories were based on the criteriasuggested by Skempton and MacDonald and the work of the U.K. National Coal Board and were alsogenerally related to the criteria of Table 1.1, 6, 7 These were then compared to limited case history dataand Fig. 2 was produced as a tool to assess structures with a length to height ratio of 1.

A later modification of the critical strain approach by Burland included lateral strain based on thework of Boscardin and Cording and adapted different values of critical strain to reflect differentdamage categories, as illustrated by Fig. 3.8 However, this approach was also limited to the case of l/H= 1 unless successive graphical constructions and interpretation are carried out. He also consideredthat there was no evidence to suggest that a strain of 0.3% could cause severe damage in spite of dataprovided by the National Coal Board and Boscardin and Cording.6, 7

Strain Superposition Method - Fundamental Principles

The strain superposition approach is based on fundamental considerations of ground movement, thedeformations that these might exert on a structure supported by the ground, and observed crackformation and enlargement in real building walls.9, 10, 11 When a structure is subject to some induceddeformation, as in tunnelling or excavation projects, the stiffness of the building will have some effecton the final ground profile. Quantification of this effect is difficult, though some advances in this area


3

0 1 2 3 4 5 6 7

0

1

2

3S

g

Self-weight

Deep

mines EVERE TO V. SEVERE

NEG buildin settlement

Shallow mines,

and tunnelsbraced cuts

MODERATETO SEVERE

Angular Distortion, x 10β 3

Hor

iz. S

train

, x

10

ε h3

Fig. 2: Relationship between angular distortion, horizontal strain, and damage category (afterBoscardin and Cording 1989)

l/H0 1 2 3 4 5 6

0.0

0.5

1.0

1.5

2.0

Fig. 1: Threshold of damage for hogging ofload bearing walls, with the bending neutralaxis at the wall base and E/G = 2.6 (afterBurland and Wroth 1974)

∆ε

/()

lc

Figure 3. Relationship of damage categoryto deflection ratio and horizontal tensilestrain for hogging and /H = 1 (afterBurland 1997).

l

0.0 0.1 0.2 0.30.0

0.1

0.2

0.3

0.4

Severe to

Very

Severe

Moderate

Slight

∆/l (

%)

Horizontal Strain (%)

Actual Building

Idealized "Beam"

Shear Deformation

Bending Deformation

Figure 4: Idealized model of buildingwall as simple beam shown in "sagging"deformation mode (modified afterBurland et al. 1977)

ShearCritical

BendingCritical

Fig. 5: Definition of geometry parametersfor building deformation problem (after Boone 1996 and Boone et al. 1999)

S = total settlementS = differential settlement

= length within deformation profile = angle of rotation relative to chord

between ends of g = slope of deformation profile relative horizontal = slope of deformation curve relative

to chord between ends of = maximum displacement from

curve chord

∆

θ

ν

ν

l

l

lmax

∆

l

L

ν'1

ν'2

θ1

θ2

g1

g2

νmax

∆S S2S1

tilt


4

have been recently made with centrifugal modelling and examinations of case histories.12 However,for the large majority of relatively small one to four-story masonry structures that are common inolder urban environments, it is reasonable and somewhat conservative to assume that the buildingdeforms to match the ground.6, 11 Provided that the final deformation profile can be estimated (an oftendifficult task in itself) the strain superposition method described in this paper remains applicable.Estimation of ground deformation profiles is beyond the scope of this paper and reference should bemade to numerous detailed studies of this subject.13, 14

The strain superposition method of analysis considers that deformation of bearing walls is analogousto deformation of deep beams. In contrast to earlier methods, however, this approach considers that auniformly loaded beam best represents load bearing walls, as the self weight and load distributed tothe wall is more likely uniform than a single point load (see Fig. 4). The position of the neutral axis ofthe beam in “hogging” has in the past been considered to be near the wall bottom considering thatmasonry will tend to separate if not restrained at the top in “hogging” deformation as might beobserved if the masonry were not mortared.4, 5 It is recognised that the foundation will offer restraintto deformation, and that the top of the wall might also be freer to deform. However, walls andfoundations may be separated by a damp-proof course in older structures, there will likely beopenings on all floor levels, and the floor and roof levels will likely be restrained in tension by thefloor and roof beams and joists intimately joined to the walls. For these reasons, this strainsuperposition method considers the neutral axis to remain near the mid-height of the wall, though themethod itself is adaptable to any chosen neutral axis location.

Deformation of building walls can be reduced to three basic modes: bending, shear, and directextension. These modes and geometry definitions are illustrated in Figs 4, 5 and 6. Using well-knownequations for beam deformation and assuming a ratio of the elastic (E) and shear (G) modulus ofcommon masonry materials of about 2.4 to 2.6, the proportions of the total maximum centraldeformation, noted herein as νmax, due to bending and shear can be readily defined (see Fig. 7).15

Using the relationship illustrated by Fig. 7, the shear strain, γ, and bending tensile strain, εM, can beseparately determined. By adding the direct lateral extension strain, εle, to the bending strain, andsubsequently applying plane-strain mechanics, the maximum principal tensile strain (“diagonal”), εp,can be determined. Trajectories of principal strain in deep uniformly loaded beams are illustrated inFig. 8. As illustrated by this figure, the trajectories of principal strain are not linear. Near the base ofthe beam, they are nearly vertical, and near the top of the beam, they are nearly horizontal. For asimple element, the direction of the principal strain can also be found as illustrated in Fig. 9. Whencalculating a finite deformation, a length to which the strain is applied must be derived or assumed.For simplicity, a “diagonal” average length is developed using the minimum length determined usingeither half the wall length or the wall height and the principal strain angle (see Fig. 9). Though thisconcept calculates the strains and deformations in one location relative to the principal straintrajectories as illustrated in Fig. 8, in reality, shear and tensile strains occur throughout the wall andthe associated cracking can develop in many areas.

Masonry and concrete are notoriously intolerant of tensile strain. A critical strain threshold for the on-set of cracking for fully intact materials can be defined based on laboratory and case studies. Criticalshear strains are about twice the tensile strain values. Critical strains for poor mortar and brickconstruction can be as little as 0.01% as summarised in Table 2. Consider a simple wall with a lengthof 10 m that is subjected to a 0.3% strain. If this deformation is fully manifested in only 1 crack, thenthe damage could be considered “severe” according to Table 1. Alternatively, if the deformation isfully manifested in 10 cracks of no more than 3 mm each, the damage might be categorised as“moderate.” The degree to which masonry and concrete materials can withstand strain withoutcracking depends on their age, composition, and quality. Small fissures and micro-cracks in masonryare also common without ground-movement-related deformation as a result of construction defects,temperature, and other factors. Therefore, within the analytical approach described in this paper, lowvalues of tolerable strain are generally assumed (between 0.01% and 0.03%). Once cracking initiatesthe distribution of cracks and their sizes need to be considered. The strain superposition methodconsiders that beyond the critical strain, cracks will widen in general preference to new cracksforming. Based on existing and new case history data, for buildings with wall heights ranging between


5

Fig. 6: Separation of deformation modes,example shown in "hogging"

Fig. 8: Principal stress trajectories insimple beam, dashed lines representcompression, solid lines representtension (after Gere and Timoshenko1974)

Fig. 10: Crack width frequency forbrick and block walls, C = individual crack width

i

0.0 0.2 0.4 0.6 0.80

20

40

60

Relative Crack Width, C

(C = C / C per wall)

w

w i Σ

Rel

ativ

e Fr

eque

ncy

(%)

y

x

x

y

dx

dy1

1

ds

γ θxydycos

θ

γxy γxydy

yx

x

y

dx

dy

1

1

ds

ε θxdxcos

θ

ε1 = ε ε ε ε γx y x y xy+ + ( + )/2} + { /2}2 2

2

tan2 = θP γxy

ε εx y +

Fig. 9: Plane strain mechanics (after Gereand Timoshenko 1984)

Original Wall Length

Wall Length + Lateral Extension

θM

Bending radius, RM

γ

νmax Extension

Bending

Shear

Deformed Shape

Bendingcurvature angle, θM

Shear strain, γ

0

2

4

6

l/H

0 2 4 6 8 10

Nor

mal

ized

Def

lect

ion

Shear

Bending

Perc

ent o

f Tot

alD

efle

ctio

n

νmax = 5q + 3q 384EI 16GA

l l4 2

Fig. 7: Contributions of shear andbending to total deformation of deep,uniformly loaded beams (after Boone 1996, Gere and Timoshenko 1974)

100 80 60 40 20 0

Bending (E/G = 2.4)

Shear

n

=1i

εxdx


6

one and four stories and lengths of 3 to 20 m, the maximum crack width will be about two thirds ofthe cumulative crack width along the wall (see Fig. 10).

Test Conditions Mode of Deformation Critical StrainBrick buildings with L/H>316 Tensile from flexure 0.05%Full scale frames with brick in-fill 17, 18 Diagonal-tensile 0.081% to 0.137%

Shear approximation 0.16% to 0.27%Hollow tile & clinker block, brickwork17, 18 Shear distortions 0.22% and 0.33%Hollow tile & clinker block, brickwork17, 18 Diagonal-tensile 0.11% to 0.16%Full scale brick walls with supporting concrete beams, 1.2<L/H<3.0 19 Tensile from flexure 0.038% to 0.06%Concrete beams supporting brick walls 19 Tensile from flexure 0.035%Fibreboard or plywood on wood frame 20 Shear strain 0.6% to 1.66%Gypsum/fiberboard/plaster on wood frame 20 Shear strain 0.37% to 0.7%Structural clay tiles with cement-lime mortar 20 Shear strain 0.1%Clay brick with cement-lime mortar 20 Shear strain 0.1% to 0.2%Cement-lime mortared concrete blocks20 Shear strain 0.1%Core samples of brick and mortar 21 Tension 0.001% to 0.01%Full scale brick walls in field test 22, 23 Tension 0.02% to 0.03%Re-evaluation of full scale wall panel tests 24 Principal tensile 0.02% to 0.03%

Table 2: Summary of Critical Cracking Strain Data

Cracking damage for frame buildings must be examined differently than damage to load bearing wallsbut many of the same fundamental principles apply to this problem as well. In general, shear strainsdominate distortions of in-fill walls in framed buildings as a result of differential settlement or heaveand the confining effect of the columns and beams. Concrete frames produce different in-fill walldeformation patterns than steel frames as the concrete frame connections provide nearly “fixed-end”conditions, while it is difficult to achieve fixed-end conditions with welded or bolted connections forsteel frames. Once the deformations of the beams are determined, however, these deformations can bedirectly applied to the in-fill walls.

Having defined the deformation geometry, separated the deformation modes, applied plane-strainmechanics principles, and applied these to reasonable estimations of building dimensions, finitecumulative crack widths for total and principal tensile strains can be calculated. These cumulativecrack widths then can be compared to the relative distribution of crack widths and Table 1 todetermine damage category (also see Figs 10 and 19). It is also assumed in this approach that whileneither principal nor total tensile crack widths may exceed the crack width threshold individually,their combined effects may produce sufficient cracking to exceed the generalised threshold criteria.

Figs 11 and 12, illustrate the basic steps for evaluating the potential damage category for bothmasonry load-bearing walls and in-fill walls within frames. The disadvantage to the strainsuperposition method is that it requires careful calculations (spreadsheets work well for this), a morethorough definition of the problem conditions, and does not lend itself well to generalised graphicalconstructions. The benefits of the strain superposition approach, however, outweigh suchdisadvantages and these advantages are:

• reliance is not placed on graphical charts that only include selected deformation modes;• differences in building geometry are accounted for;• all deformation modes are accounted for;• potential cumulative and maximum crack widths are directly calculated to permit a direct

correlation to building damage categorisation schemes (as in Table 1) with physical meaning; and • the approach provides a transparent method for evaluating the effects of building distortion using

fundamental geometry and engineering principles.

Discussion

Data from over 100 case histories of damage to masonry bearing walls and masonry in-fill wallswithin concrete frames have been reviewed and examined using the methods described above.Damage categories as illustrated in Figs 13 through 17 are based directly on the descriptions of


7

1. Find mathematically or graphically (slope of settlement curve - divide profile at inflection points)2. tilt = S/L3. ' = tan[tan ( ) - tan (tilt)]4. Find = ' /4 or graphically5. Deformation due to bending:

= . ' = . (1+ 2.88H / ) (1+ 2.88H / )

g

gl

l l

∆ν

ν ν

ν ν

-1 -1

2 2 2 2

max

max(M) max (M) ' ν ν

'

l

L

∆Sν'θ

νmax

g

h1 h2

Displacement

Horizontal Displacements and h h1 2

Approximate "Diagonal" Length for Use in Estimating Cracking from Principal Tensile Strains

ldθ γ ε

θ

P le

d

= tan [ /( )]/2minimum of: = 0.5 /(cos ) or

-1

l l P

d Pl = H/(sin )θ

Fig. 11: Evaluation of potential damage toload-bearing wall

L

l

1. = 2. = min. of /(cos ) or H/(sin )3. = 4. 0.5 + [(0.5 ) +(0.5 ) ]5. C = max( - , 0)6. C = max( - , 0)

γ γθ θ

ε εε ≅ ε ε γ

ε εε ε

avg max

d P P

t le

p t t avg

t t c

p p c d

l l

ll

2 2 1/2

γ∆S

L

H

1. = 1.5 S/L - tilt2. minimum of = 0.5 /(cos ) or H/(sin )3. = 4. 0.5 + [(0.5 ) +(0.5 ) ]5. C = max( - , 0)6. C = max( - , 0)

γ ∆θ θ

ε εε ≅ ε ε γ

ε εε ε

avg

d P P

t le

p t t avg

t t c

p p c d

l l

ll

2 2 1/2

CONCRETEFRAMES ANDIN-FILL WALLS

IN-FILL WALLS INSTEEL FRAMES

ld

∆S

tilt

γ for infill walls

νmax for beamanalysis

ld

Fig. 12: Evaluation of potential damage to in-fill walls and beams in frame structures

6. Deformation due to shear:

= - ; ' = - ' ; = tan ( ' )

7. Radius of bending: R = . 2sin[tan ( ' )]8. bending strain = H/(2R )9. lateral extension strain = ( - )/10. total tensile strain = + 11. shear strain = /212. principal = 0.5 + [(0.5 ) + (0.5 ) ]13. cumulative tensile crack width C = max( - ,0)14. cumulative principal crack width C = max( - ,0)

ν ν ν ν ν ν γ ν

νε

εε ε ε

γ γε ε ε γ

εε

max(V) max max(M) (V) max (M) max (V)

M

(M)

M M

le 1 2

t M le

avg max

p t t avg

t t

p p d

-1

-1

2 2 1/2

l

h h l

ll

εε

c

c

0 1 2 3 4 50

1

2

3

4

Severe

Slight

Moderate

Negligible

Fig. 13: Comparison of with central deflection and /H, after Burland et al.l 5, 8"hogging" walls

∆/ (x

10

)l

3

l/H

Reported Damage

NegligibleVery SlightSlightModerateSevereVery Severe

+

tilttilt

VSV

Damage ThresholdsBased on Strain

ModerateSevere

Very Severe

Superposition Method

VSV++

++ ++


8

0 1 2 3 4 5 6 7

0

1

2

3

Angular Distortion, x 10β 3

Hor

iz. S

train

, x

10

ε h3

Fig. 14: Comparison of bearing wall case history data to chart of Boscardin and Cording (1989)

Fig. 15: Comparison of "hogging" case history data to chart of Burland (1997)

0.0 0.1 0.2 0.30.0

0.1

0.2

0.3

0.4

Severe to

Very

Severe

Moderate

Slight

∆/l (

%)

Horizontal Strain (%)

+++++++++

Severe to Very Severe

Moderateto Severe

Slight

0 5 10 15 20 25

20

15

10

25

5

0

Fig. 19: Comparison of case historiesand strain superposition method estimation of damage

CumulativeTensile Crack Width (mm)

Cum

ulat

ive

Prin

cipa

l Cra

ck W

idth

(mm

)

Fig. 16: Damage thresholds for load bearing walls, H = 8 m, = 0.01%,see Table 1 for categories

εc

0 1 2 3 4 5 6

12

3

4

5

β = 1/300β = 1/

150

80

60

40

20

0

H = 12 m = 0.03%εc

Cen

tral D

efle

ctio

n (m

m)

l/H

Fig. 17: Damage thresholds for in-fillwalls in steel frames (dotted lines) and concrete frames (solid lines), see Table 1 for categories

0 1 2 3

100

80

60

20

0

40

Diff

eren

tial S

ettle

men

t (m

m)

l/H

β = 1/300

β = 1/150

2

3

4

5

0 1 2 3 4 5 6 >6

16

12

8

4

0

l/H

Freq

uenc

y

Fig. 18: Length to height ratio of case histories of damaged bearing walls

3

4

5

Moderate

Severe

Slight


9

damage provided in the original references and Table 1. In all data analyses, critical cracking strainwas not included as a criterion (i.e. εc = 0%). The simple cumulative deformation was used directlyconsidering that the buildings may have exhibited some initial cracking due to construction defects,thermal cracking, or from age. Fig. 13 illustrates data trends using the methods of Burland andcolleagues without consideration of horizontal strain and the data scatter relative to damage categoriesis evident. Fig. 14 illustrates some reasonable agreement between the method of Boscardin andCording and the reported damage categories. However, it can also be seen that the method both under-and over-predicts the damage category in some cases, some of these by several categories. Fig. 15compares the data to ∆/l and horizontal strain for cases of “hogging damage.” Using the strainsuperposition method, thresholds for damage for load bearing and in-fill walls are illustrated in Figs16 and 17 along with conventional angular distortion criteria. The differences between the estimatedand reported damage categories for each of the methods described above arise for two basic reasons.First, though many of the case histories exhibited an l/H between 0.75 and 1.25 (near 1), more than70% of the cases exhibited other values of l/H (see Fig. 18). Second, horizontal strain is notconsidered in some methods.

Fig. 19 illustrates the results of detailed re-examinations of published case histories in accordancewith the strain superposition method described in this paper illustrating good agreement with reporteddamage categories. Fig. 20 compares the difference between the estimated and reported damagecategories for the three methods that consider horizontal strains. Of these, the strain superpositionmethod provided the best results with about 44% of the 93 cases of load bearing walls correctlycategorised with the results approximating a normal distribution around a mean of 0 (correctestimated category). The critical strain method was applied only to 76 structures with “hogging”damage. The other two approaches produced less satisfactory results, often with the potential damagecategory under-predicted, largely because of the differences in l/H ratio and critical strain thresholdsas discussed above.

Conclusions

The use of “angular distortion” as a damage criterion should be abandoned to avoid future confusionand over-simplification. Using other generalised criteria involves inherent simplifications that canunder- or over-predict building damage. The fundamental principles related to geometric changes inthe structure and ground can reasonably be applied to building damage problems through applicationof clear structural engineering methods (deep beam deformation, strain superposition, and plane-strainmechanics). The strain superposition method provides a reasonable and clear approach to buildingdamage estimation problems and is the logical extension of work that has come before. As stated byBurland and colleagues, however, it must also be remembered that the crack width (estimated orobserved) is not the only index of damage category. The method can suitably be adapted tospreadsheet calculations using simple building and ground deformation geometry such that efficientexaminations of many structures can be completed. Following parametric evaluations of particulartunnel or excavation influences, structures that appear to be more sensitive or might experience

Estimated Damage Category - Reported Damage Category

Freq

uenc

y of

Occ

uran

ce (%

)

Fig. 20: Comparison of damage category estimation methods of Boscardin and Cording, strain superposition method, and Burland 6, 9 & 11, 8

-4 -3 -2 -1 0 1 2 3 4-4 -3 -2 -1 0 1 2 3 4-4 -3 -2 -1 0 1 2 3 40

10

20

30

40

50

60 Strain SuperpositionBurland (1997)Boscardin &Cording (1989)


10

unacceptable damage can be examined through use of numerical models or more intensive structuralanalyses in a two-step approach.25, 26 For future examinations of this problem, it would also bebeneficial for published case histories to include detailed measurements of crack widths such thatbetter comparisons can be made to available prediction methods and the nature of cracks and theirdistribution in real buildings.

References

References indicated * include damaged building data used in preparation of this paper.

1. A.W. SKEMPTON and D.H. MACDONALD: “The Allowable Settlements of Buildings,” Proc., Inst.of Civ. Engrs., 1956, Part III, 5, 727-768.*2. G.G. MEYERHOF: “Some Recent Foundation Research and its Application to Design,” TheStructural Engineer, 1956, Vol. 31, 151-167.3. L. BJERRUM: “Discussion,” Proc. of the Eur. Conf. on Soil Mech. and Found. Eng., 1963, Vol. III,Wiesbaden, 135.4. J.B. BURLAND and C.P. WROTH: “Settlement of Buildings and Associated Damage,” BuildingResearch Establishment Current Paper, 1975, Building Research Establishment, Watford. 5. J.B. BURLAND, B.B. BROMS, and V.F.B. DEMELLO: “Behavior of Foundations and Structures:State of the Art Report,” Proc. of the 9th Int. Conf. on Soil Mech. and Found. Eng., 1977, Tokyo, 495-546.*6. M.D. BOSCARDIN and E.J. CORDING: “Building Response to Excavation-Induced Settlement,” J.of Geotech. Eng., 1989, ASCE, 115( 1), 1-21.7. NATIONAL COAL BOARD: Subsidence Engineer’s Handbook. National Coal Board ProductionsDepartment, London, 1975.8. J.B. BURLAND: “Assessment of risk of damage to buildings due to tunnelling and excavation,”Earthquake Geotechnical Engineering, Ishihara (ed.), 1997, Balkema, Rotterdam, 1189 - 1201.9. S.J. BOONE: “Ground Movement Related Building Damage,” J. of Geotech. Eng., 1996, ASCE,122(11), 886 - 896.*10. S.J. BOONE: “Ground-Movement-Related Building Damage: Closure,” J. of Geotech. andGeoenvironmental Eng., 1998, ASCE, 124(5), 463 - 465.11. S.J. BOONE, J. WESTLAND, and R. NUSINK: “Comparative Evaluation of Building Responsesto an Adjacent Braced Excavation,” Canadian Geotech. J., 1999, Vol. 36, 210-223.*12. R.N. TAYLOR and D.M. POTTS: “Centrifuge modelling of the influence of surface structures ontunnelling induced ground movements,” Tunnels and Metropolises, Balkema, 1998, 261 - 266.13. B.M. NEW and M.P. O’REILLY: “Tunnelling Induced Ground Movements; Predicting theirMagnitude and Effects,” Proc. of the 4th Int. Conf. on Ground Movements and Structures, Cardiff,Wales, Pentech Press, 1991, 671-697.14. G.W. CLOUGH and T.D. O’ROURKE: “Construction Induced Movements of Insitu Walls,”Design and Performance of Earth Retaining Structures, Geotech. Special Publication No. 25, ASCE,P.C. Lambe and L.A. Hansen, eds., 1990, 439 - 470.15. J.M. GERE and S.P. TIMOSHENKO: Mechanics of Materials, PWS Publishers, Boston, 1984.16. D.E. POLSHIN and R.A. TOKAR: “Maximum Allowable Non-Uniform Settlement of Structures,”Proc. of the 4th Int. Conf. on Soil Mech. and Found. Eng., 1957, Vol. 1, 402-405.17. R.J. MAINSTONE: “On the Stiffness and Strengths of In-filled Frames,” Proc. of the Inst. of Civ.Engrs., 1971, Supplemental Vol. IV, Paper 7360S, 57-90. 18. R.J. MAINSTONE and G.A. WEEKS: “The influence of a Bounding Frame on the RackingStiffness and Strengths of Brick Walls,” Proc. of the Second Int. Brick and Masonry Conf., England,1970, 165-171.19. J. BURHOUSE: “Composite Action Between Brick Panel walls and their Supporting Beams, Proc.,Inst. of Civ. Engrs., 1969, Part III, 5, 782-783.*20. M. BOZOZUK. “Soil Shrinkage Damages Shallow Foundations at Ottawa Canada,” TheEngineering Journal, 1964, Canada, July, 33-37.21. W.W. FRISCHMANN, J.E. HELLINGS, and C. SNOWDON: “Protection of the Mansion HouseAgainst Damage Caused by Ground Movements Due to the Docklands Light Railway Extension,” Proc.of the Inst. of Civ. Eng., Geotech. Eng., 1994, Vol. 107, 65-76.*


11

22. G.S. LITTLEJOHN: “Observations of Brick Walls Subjected to Mining Subsidence,” Proc. of theConf. on Settlement of Structures, Cambridge, 1974, 384-393.*23. G.S. LITTLEJOHN: “Discussion,” Proc. of the Conf. on Settlement of Structures, Cambridge,1974, 764-767.*24. R.J. MAINSTONE: “Discussion,” Proc. of the Conf. on Settlement of Structures, Cambridge, 1974,771-773.25. S.J. BOONE, B. GARROD, and P. BRANCO: “Building and Utility Damage Assessments, Riskand Construction Settlement Control,” Tunnels and Metropolises, Balkema, 1998, 243 - 248.26. W.J. RANKIN: “Ground movements resulting from urban tunnelling: predictions and effects,”Engineering Geology of Underground Movements, F.G. Bell et al. (eds), Geological Society, London,1988, 79 - 92.27. J.E. CHENEY and D. BURFORD. “Damaging Uplift to a Three-story Office Block Constructed ona Clay Soil Following the Removal of Trees,” Proc. of the Conf. on Settlement of Structures,Cambridge, 1974, 337-343.*28. M.D. BOSCARDIN, E.J. CORDING, and T.D. O’ROURKE: “Case Studies of building Behavior inResponse to Adjacent Excavation, Report No. UMTA-IL-06-0043-78-2,” U.S. Department ofTransportation, 1979.*29. E.W. BRAND and N. LUANGDILOK: “A Long Term Foundation Failure Caused by Dragdown onPiles,” Proc., 4th Southeast Asian Conf. on Soil Eng., Kuala Lumpur, Malaysia, 1974, Vol. 4, 15 - 24.*30. E.J. CORDING, T.D. O’ROURKE, and M.D. BOSCARDIN: “Ground Movements and Damage toStructures,” Proc., Int. Conf. on Evaluation and Prediction of Subsidence, Florida, 1978, 516-537.*31. R. DRISCOLL: “The Influence of Vegetation on the Swelling and Shrinking of Clay Soils inBritain,” Geotechnique, 1983, 33(2), 93-105.*32. S. FJELD: “Settlement Damage to a Concrete-Framed Structure,” Norwegian GeotechnicalInstitution, Publication No. 58, 1963, NGI, Oslo, 37-45.*33. R. GRANT, J.T. CHRISTIAN, and E.H. VANMARCKE: “Differential Settlement of Buildings,”J.of the Geotech. Eng. Div., 1974, ASCE, 100(9), 973-991.34. D.I. HARRIS, R.J. MAIR, J.P. LOVE, R.N. TAYLOR, and T.O. HENDERSON: “Observations ofGround and Structure Movement for Compensation Grouting During Tunnel Construction at WaterlooStation,” Geotechnique, 1994, 44(4), 691-713.*35. I.A. MACLEOD and J.G. PAUL: “Settlement Monitoring of Buildings in Central Scotland,”Geotechnique, 1984, 34(1), 99-117.*36. G.G. MEYERHOF: “The Settlement Analysis of Building Frames,” The Structural Engineer, 1947,Vol. 25, 369.*37. T.D. O’ROURKE, E.D. CORDING, and M. BOSCARDIN: The Ground Movements Related toBraced Excavations and Their Influence on Adjacent Structures, Report No. DOT-TST 76T-23,” U. S.Department of Transportation, 1976.*38. R.B. PECK, D.U. DEERE, and J.L. CAPACETE: “Discussion on “Allowable Settlements ofBuildings”, Proc., Inst. of Civ. Engrs., 1956, Part III, 5, 778-781.*39. K. TERZAGHI: “The Actual Factor of Safety in Foundations,” The Structural Engineer, 1935, Vol.13, 126-160.*40. W.H. WARD: “Discussion on Allowable Settlements of Buildings,” Proc., Inst. of Civ. Engrs.,1956, Part III, 5, 782-783.*41. D.WL. WEBB: “Observed Settlement and Cracking of a Reinforced Concrete Structure Founded onClay,” Proc. of the Conf. on Settlement of Structures, Cambridge, 1974, 443-450.*42. G.M.J. WILLIAMS: “Discussion on Allowable Settlements of Buildings,” Proc., Inst. of Civ.Engrs., 1956, Part III, 5, 772-773.*43. J.G. WILSON, T.G. GARWOOD and R.W. SARSBY: “The Settlement of Low BuildingsConstructed Over Peat,” Proc. of the Conf. on Large Ground Movements and Structures, Cardiff,Pentech Press, 1984, 527-538.*

Appendix A - Damage Parameters of Prior Works

∆/L Central Deflection Ratio: maximum deflection between the beam deflection line and the straightline between the two end points (chord) divided by the chord length2

δ/l Angular Distortion: differential settlement of two points divided by the distance between thosetwo points less the tilt of the entire structure 1


12

f Relative Deflection: "...comprising the ratio of deflection to the length of the deflected part..." 16

β Inclination of levelled groove as related to infill wall panel 32

α Inclination of levelled groove as related to horizontal 32

γ Inclination of panel as a whole to building as a whole 32

∆/L Deflection Ratio: maximum deflection between the beam deflection line and the straight linebetween the two end points (chord) divided by the chord length4

β Relative Rotation: rotation of the straight line joining two reference points relative to the tilt,equal to Skempton and MacDonald's δ/l 4

δ/l Maximum Net Slope of Deflection Curve 33 ∆ Curvature Parameter: maximum deflection between the settlement curve and the chord joining

the two endpoints divided by the chord length 33

β Angular Distortion: maximum change in slope along the beam, or the slope at the support 6

Appendix B - Notation

C = cumulative crack width, subscripts t and p represent tensile and principal-tensile directionsE, G = shear and elastic modulusg = slope of deformation curve related to horizontal at tangent or inflection points of curveI = moment of inertiaL, l = original span length and length of straight line between curve endpointsq = uniformly distributed loadRM = radius of curvature defined by moment (bending) portion of total deflection∆S = differential settlement between endpoints of lθ, θ M = angle of rotation at support of simple beam, angle due to bending (moment)θ P = angle of maximum principal tensile strainε = tensile strain; subscripts c, le, M, and P represent critical, lateral extension, bending, and

principle tensile strain, respectivelyεt = total tensile strain = εM + εg + εle

γ = shear strain (radians)ν = deflection of beam in relation to chord between beam endpoints - ν is retained as the

general notation for deflection consistent with Timoshenko's work where ν max = δ, and toavoid confusion with prior uses of δ in this particular subject; subscripts max, (M), and (V)indicate maximum and proportions of deformation associated with bending (moment) andshear, respectively

ν ' = slope of deflection curve, or δν/δx, related to angle of chord between deformation curveendpoints; subscripts max, (M), and (V) indicate maximum and proportions of deformationassociated with bending (moment) and shear, respectively

assessing construction

Documents