Seismic Vulnerability Assessment of Malawian buildings. · earthquake 1) OUT OF PLANE 2) IN PLANE...

UK - Malawi Disaster Research Workshop

MUST, 6 -10 August 2018

Seismic Vulnerability Assessment of

Malawian buildings.

Day 4: Structural and Earthquake Engineering

Dr Viviana Novelli



Self-weight

Wind

Earthquake

Strength

Durability

Cost efficiency



The walls lying

perpendicular to the

direction of ground shake

will fail first.

If walls are connected

properly, houses behave as

a box and walls do not

collapse in out of plane.

Good connections between walls



This can be achieved by

ensuring good

interlocking of the

masonry courses at the

junctions,

employing horizontal

bands at various levels,

particularly at the lintel

level.



PIER: vertical element. Ex: panel between openings PIER: vertical element. Ex: panel between openings, or

between the edge of a façade and an opening



Dimension of bricks

Opening distribution



SPANDREL: Horizontal element. Panel on the top or bottom of an

opening.

Timber lintel (??) Timber lintel (??) bricks Bamboo lintel (??)

Concrete lintel Concrete band

Lintel type and size

timber post bricks bamboo post

concrete beam concrete ring





Team 1 Team 2 Team 3 Team 4



Team 13 Team 14

Yesterday..

23 Buildings 46 forms

Excellent!



Did the field experience help you to look at the buildings in a different way?

Why?



Some of the few buildings of yesterday



PORTICO: a structure consisting of a roof supported by columns at regular intervals,

typically attached as a porch to a building.

length

depth

# pillars/columns = 3



1.2 13.1

14.1 3.2



• Big house

• Fired brick +cement

• Ring beam

• Portico (NO)

12.3

13.1 Single skin

double skin



3.2

(E1)



2.1

big house - single skin – B1- M/C

7.1

big house - single skin – B1- C

Too slender



13.2



13.2



7.2

Thatch

roof



6.3

buttress



13.2 Connection 6.3 buttress



5.1

Double skin

Bad construction detail

Beam sagging



Inspection form FOR HOUSES in MALAWI

1. URBAN DATA

2. GEOMETRY CHARACTERISTICS OF THE FAÇADE (vertical additional are excluded)

3. GEOMETRY CHARACTERISTICS of OPENING

4. GEOMETRY CHARACTERISTICS in PLAN GEOMETRY

5. STRUCTURAL CHARACTERISTICS

6. VULNERABILITY ELEMENTS

7. DAMAGE AND MECHANISMS IDENTIFICATIONS (section 7.2 FAILURE MODES)



A FAILURE MODE is a manner in which a building collapse can occur

when an earthquake hits a construction

After an earthquake (if buildings are

damaged by cracks due to the seismic

event)

Failure modes can be identified on site

by observation

Before an earthquake

Failure modes can be identified

analytically with numerical approaches

using models for the estimation of the

failure modes that have the highest

probability of occurrence



FAILURE CAUSES

Geometric and

structural features of

the buildings +

deficiencies (bad

connections, poor

constructional materials,

low quality constructions

FAILURE MODE

FAILURE EFFECTS

Crack patterns and

severity of the damage

Section 1 to 6 in the

inspection form

Section 7.1 in the

inspection form

Section 7.2 in the

inspection form

The damage observed on

the houses in Kanjedza is

not caused by an

earthquake, therefore it is

not always straightforward

to understand if a failure

mode is taking place, since

the observed cracks may

be only a partial

development of a failure

mode or caused by

deterioration of materials

due to weathering or lack

of maintenance



Combined Mechanisms

B1: façade

overturning with

one side wall

B2: façade

overturning with two

side walls

C: overturning with

diagonal cracks

involving corners

F: overturning

constrained by ring

beams or ties

In plane Mechanisms

H1: diagonal cracks

mainly in piers

H2: diagonal cracks

mainly in spandrel

M1: soft storey due

to shear

M2: soft storey due

to bending

Out of Plane Mechanism

A: façade

overturning with

vertical cracks

D: façade

overturning with

diagonal crack

E: façade

overturning with

crack at spandrels

G: façade

overturning with

diagonal cracks

Type of failure

modes

(mechanisms)

due to an

earthquake

1) OUT OF PLANE

2) IN PLANE

3) COMBINED

Combined Mechanisms

B1: façade

overturning with

one side wall

B2: façade


side walls

C: overturning with

diagonal cracks

involving corners

F: overturning

constrained by ring

beams or ties

In plane Mechanisms

H1: diagonal cracks

mainly in piers

H2: diagonal cracks

mainly in spandrel

M1: soft storey due

to shear

M2: soft storey due

to bending


A: façade

overturning with

vertical cracks

D: façade

overturning with

diagonal crack

E: façade

overturning with

crack at spandrels

G: façade

overturning with

diagonal cracks

Combined Mechanisms

B1: façade

overturning with

one side wall

B2: façade


side walls

C: overturning with

diagonal cracks

involving corners

F: overturning

constrained by ring

beams or ties

In plane Mechanisms

H1: diagonal cracks

mainly in piers

H2: diagonal cracks

mainly in spandrel

M1: soft storey due

to shear

M2: soft storey due

to bending


A: façade

overturning with

vertical cracks

D: façade

overturning with

diagonal crack

E: façade

overturning with

crack at spandrels

G: façade

overturning with

diagonal cracks



Out of plane failure

modes

A:

Overturning

caused by

lack of

connection

of both sides

of the wall

(Vertical

cracks)

D: Overturning of the top corner due

to lack of connection on one side of

walls (Diagonal + vertical cracks)

E:

Overturning

of a portion of

the façade in

corresponden

ce of the

piers

(Vertical

cracks)

G:

Overturning of

the gable

(Arch crack

pattern)

a) Overturning due to lack of connection of both side of the façade

b) Overturning of a portion of the

façade in correspondence of

the piers

c) Overturning due to lack of

connection of one side of the façade

A D E

Arch failure due to out-of-plane

Failure mode G

Failure mode



In plane

failure modes

Buildings

characterised by

good connections

among walls Global in-plane failure modes due to shear

Failure mode H2

Local in-plane failure modes due to shear

a) on spandrels b) on piers

H1 spandrels H1 piers

H1: Regular opening layout (Diagonal or X cracks)

H2: Irregular opening layout (Diagonal cracks)



House

inspected

in Salima, used

during Day 2

for the

workshop



E2: Overturning of a portion of

the façade in correspondence of

the piers (Vertical cracks)



A: Overturning caused by lack of

connection of both sides of the

wall (Vertical cracks)

E2: Overturning of a portion of

the façade in correspondence of

the piers (Vertical cracks)



Before an earthquake, it is not always easy to identify the possible failure modes

that may occur on a building by using observation.

The observed cracks

• point out the presence of deficiency in a building (lack of connections – low

quality of materials – bad maintenance) and

• exclude or include the possibility that some failure modes occur during an

earthquake.

TOTAL NC TOTAL LD


MUST, 6 -10 August 2018 Global

In plane Failure

Vertical crack along

the edge wall. The lack

of connection point out

that the wall will fail in

Out of plane during an

earthquake

The diagonal and

vertical crack on

the gable point out

a high probability

of an overturning

of the gable during

an earthquake

Vertical crack

outlining a strip

that has high

probability to fail

in Out of plane

during an

earthquake



Before an earthquake

Failure modes can be identified

analytically with numerical approaches

using models for the estimation of the

failure modes that have the highest probability of occurrence

Dr. Viviana Novelli

FaMIVE

Failure Mechanism Identification and Vulnerability

Evaluation method

Ref: Novelli and D’Ayala 2015, D’Ayala 2005, D’Ayala and Speranza 2003



FaMIVE estimates the seismic

vulnerability of building type by using

mechanical models developed to simulate

the seismic performance of masonry

buildings.

describes the probability of a building (or

BUILDING TYPES) to be damaged or to

collapse for a given hazard (Coburn, et al.,

1994).

VULNERABILITY



On site inspection

Structural/geometric/mechanical properties deficiencies



FaMIVE Ultimate Limit State

Analysis Load factor multiplier

(λA... λM) for all failures

Possible approach to assess the

performance of masonry buildings

Combined Mechanisms

B1 B2 C F

Out-of-plane Mechanisms

A D E G

In-plane Mechanisms

H1 piers H1 spandrels H2



Estimation of the seismic performance On site inspection

Drift

a (

%g

)

Derivation of an equivalent SDOF system

Derivation of the capacity curves



Class C1

Fired brick with cement mortar and

concrete lintels

FROM MEDIUM TO HIGH QUALITY

(single and double skin)

Class C2

Fired brick with mud mortar

MEDIUM QUALITY


Class C3

Unfired/Fired brick with mud mortar

LOW QUALITY

(single skin)

2.1, 7.1, 7.2, 10.3, 12.3, 13.1, 13.3, 14.1

7.2

3.2 6.2

11.3 8.2 1.2 , 4.2, 5.1, 6.3, 8.2, 9.1

9.3, 11.3,13.2, 14.2

2.2, 3.2, 6.2, 9.2



2.1, 7.1, 7.2, 10.3

12.3, 13.1, 13.3, 14.1

1.2 , 4.2, 5.1, 6.3, 8.2, 9.1

9.3, 11.3,13.2, 14.2

2.2, 3.2, 6.2, 9.2 Good

quality

Medium

quality

Low quality



Dr. Viviana Novelli

IP:

In plane

failure mode

OOP:

Out of plane

failure mode

COMB

Corner failure

mode

GABLE

Arch

failure

mode

No connection yes connection



IP:

In plane

failure mode

OOP:

Out of plane

failure mode




Dr. Viviana Novelli

COMB

Corner failure

mode

GABLE

Arch

failure

mode



Dr. Viviana Novelli

IP:

In plane

failure mode

OOP:

Out of plane

failure mode

COMB

Corner failure

mode

GABLE

Arch

failure

mode




Class C1

Fired brick with cement mortar and

concrete lintels

FROM MEDIUM TO HIGH QUALITY


Class C2

Fired brick with mud mortar

MEDIUM QUALITY


Class C3

Unfired/Fired brick with mud mortar

LOW QUALITY

(single skin)

2.1, 7.1, 7.2, 10.3, 12.3, 13.1, 13.3, 14.1

7.2

3.2

11.3

1.2 , 4.2, 5.1, 6.3, 8.2, 9.1

9.3, 11.3,13.2, 14.2

2.2, 3.2, 6.2, 9.2



C3 C1 C2

Derivation of capacity fragility curves

C3

C1

C1

C3 C2



plan - Regularity

Opening layout (piers spandrels)

Material quality

Roof material

Connections

Wall plates

Ring beam

Buttresses

Portico

Re-entrant corner

Chimney

geometry

Structural features

Vulnerability elements

Restraining

elements

Impact on

the

building

behaviour

ARE MASONRY HOUSES RESISTANT TO EARTHQUAKE?

Conclusion



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Seismic Vulnerability Assessment of Malawian buildings. · earthquake 1) OUT OF PLANE 2) IN PLANE...

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