Structural Forensic Investigation on

Seismic Induced Damages to Buildings

in Ranau

Presented by:

Dr. Sophia C. Alih

Faculty of Civil Engineering, Institute of Noise and Vibration,

Universiti Teknologi Malaysia, Johor Bahru

Factors affecting level of damages induced by seismic load:

Architectural design Structural design & detailing Soil beneath Proximity to other buildings Earthquake intensity

Irregularity in building configuration

Non-compliance structural design (beam/column size)

Non-compliance reinforcement bars detailing

Case study: Reinforced concrete buildings in Ranau following the 2015 Sabah Earthquake (M6.0) i) 5 stories residential quarters of Ranau Hospital ii) 2 story hotel cabin in Kundasang iii) 3 stories residential quarters of Kundasang hotel iv) 3 stories school buildings in SMK Ranau and SMK(A) Ranau v) 3 stories school buildings in SMK Agama Ranau

Investigated Buildings in Ranau

18.5km

19.5km 16.9km

18.5km

i) Ranau Hospital ii) SMK Ranau iii) SMK Agama Ranau

Soft-first story phenomenon

5-Story MRF Concrete Residential building in Ranau Hospital

X Y

Front View 3D View

Observed damage to infill panels

5 Story MRF Concrete Residential building in Ranau Hospital

X Y

Y X

View from behind the building View from behind the building

Observed damage to infill panels

Diagonal crack in the infill panel

X-direction Diagonal crack in the infill panel

Y-direction

Observed damage to infill panels

Crushing of the corner

Y-direction Diagonal crack in the infill panel

Y-direction

Observed damage to infill panels

Shear-friction failure

Y-direction

Crushing of the corner

Y-direction

Y X

Observed damage from infill panels to Columns

Shear force transfer from infill

panel to column Shear failure of column

60

30

Observed damage from infill panels to Columns

Shear force transfer from infill

panel to column

Shear failure of column

Observed damage from infill panels to Beams

Shear failure of beam to column joint Shear failure of beam to column joint

Other types of damage to beams and columns

Strong beam weak column

Resulted in Shear failure of column Damage to stairs slab due to lack of beam

Other types of damage to beams and columns

Short beam behaves in shear mode Shear damage to a short beam

Diagonal reinforcement is required

Other types of damage to beams and columns

Damage to column

Lack of hook at the end of rebar

Force concentration

Major Findings:

1- Damages have only occurred in the ground floor.

2- Damages mostly concentrate on stair case region.

3- Damages occurs mostly in infill panels.

Staircase at the first floor of damaged

building

WHY?

An Intact Building in the Hospital area

1- Soft Story phenomena due to removal of infill

panel in the ground level.

k1

k1

k2

k1

k1

K2<<k1

k1

k1

k1

k1

k1

1.5

1.75 1.85 3.15 3.04 3.5 3.0 3.5 3.04 3.15 1.85 1.75

3.7

2.2

2.2

1.0

Units: meter

2- Irregularity in Plan Causing Torsional Forces

CM

CS

Earthquake Force

How to avoid such seismic induced damages?

Soft story damage to a building

Are infill panel useful elements against seismic loads or

not?

Answer is “Yes” if the following conditions are considered in the design:

1- The distribution of infill panels in the plan is symmetrical. (to avoid torsional behavior)

2- The distribution of infill panel along the height is continuous. (to avoid soft-story)

3- They are included in the calculation of natural period of structures. ( to increase base shear)

4- They are anchored to the adjacent columns. ( to avoid out of plane failure)

Investigated buildings in Kundasang

10.4km 8km

10.8km

i) Dream World Resort

ii) Kinabalu Pine Resort

iii) Mount Kinabalu Heritage & Spa

iv) Wooden Structures in the town

Building on sloping ground- Short column phenomenon

Dream World Resort

3-story MRF building 2-Story MRF building

2-Story MRF Concrete building in Dream World Resort

2-Story MRF Concrete building in Dream World Resort

Measuring size of Beams and Columns

2-Story MRF Concrete building in Dream World Resort

Schmidt hammer test on damaged column

Concrete strength: 30 – 35 N/mm2

2-Story MRF Concrete building in Dream World Resort

Measuring the size of reinforcement bars and stirrups

Distance of stirrups in the damaged column

2-Story MRF Concrete building in Dream World Resort

Structural plan

2.1m

4.6m

1.7m

1.4m

2.2m 1.9m 2.1m 2.0m

Side elevation

2.7m

Wooden structure

Ceiling: Fall

2.9m

1.5m

RC beam and column

2-Story MRF Concrete building in Dream World Resort

Column details: Reinforced concrete

2Ø12mm

2Ø12mm

200mm

200mm

Ø10mm @ 300mm

Beam details: Reinforced concrete

500mm

150mm

• Rebar size unknown • Improper detailing at

beam-column joint

2-Story MRF Concrete building in Dream World Resort

i) Overlapping reinforcements at the Joint ii) Large spacing of stirrups in columns

2-Story MRF Concrete building in Dream World Resort

iii) Poor concrete quality

iv) No reinforcements at the joint

2-Story MRF Concrete building in Dream World Resort

1.0m

2.7m

Shear force distribution is based on relative stiffness of columns. K=3EI/L^3 K(c1)=3EI/L(c1)^3 K(c5)=3EI/L(c5)^3 V1/V5= K(c1)/K(c2)

V1= 20 more than V5

Ground motion

F

C1 C2 C3

C4 C5

Short Column

V1

V5

Increase in Damage of columns

2-Story MRF Concrete building in Dream World Resort

Short Column

How to avoid such seismic

induced damages?

300mm

How to avoid such seismic

induced damages?

How to avoid such seismic induced damages?

How to avoid such seismic induced damages?

Dream World Resort

3-story MRF concrete building

A closer view of 3-storey MRF building A view from bottom of the building

Earthquake direction

Proportional size of beam against size of column

Short Column

Dream World Resort

3-story MRF concrete building

Shear cracks

Shear damage to short column Minor cracks in the beam to column joint

Plaster for repairing cracks

Investigated Buildings in Ranau

18.5km

19.5km 16.9km

18.5km

i) Ranau Hospital

ii) Ranau Mosque

iii) SMK Ranau

iv) SMK Agama Ranau

SMK Ranau

Shear failure of the column due to short column phenomena

Short Column Phenomena

Seismic

force to

the joint

Shear

Failure of

Column

Support

SMK Ranau

Damage to the connection zone of L shape building

Damaged

Zone

SMK Ranau

Damage to the corner of L shape building

SMK Ranau

Seismic induced Damage to L shape structures

SMK Ranau

Block A

Block B

SMK Ranau

Minor damage to infill panels located in

transverse direction

Block B

Minor damage to infill panels located in

transverse direction

Repairable cracks

Repairable cracks

SMK Ranau

Severe Damage to the only infill panel in longitudinal direction

Column

Short Column Phenomena

View “A”

View B

Imposed force

SMK Ranau

View “A” Concrete Spalling due to excessive compressive force at joint

Min. size of shear reinforcement is 8mm

Plain bars are not allowed (not ribbed)

Closely spaced

stirrups 5 cm

Damaged Zone Rebar is

outside

column’s

core

No stirrup at the joint

SMK Ranau

View “B”

Concrete Spalling due to excessive compressive force at joint

Damaged Zone Seismic force to the joint

No stirrup at the joint

Rebar is

inside

column’s

core

SMK Ranau

Damage to the brick walls Coverage of Columns to hide sewerage pipe

Concrete Column

Brick Wall

Intact Column

Sewerage Pipe

Fallen Brick Wall

Required rebar Anchorage

Tensile force

~60 cm

Required Anchorage

SMK Ranau

Hazardous Non-structural Components- After shocks can easily tumble them

SMK Agama, Ranau

Fallen brick walls and damage to non-structural components

Ranau Mosque

Non-structural damage to the

minaret

Fallen brick walls ( no anchorage to the structure)

Flat surface

without

anchorage

Flat surface

without

anchorage

Ranau Mosque

Non-structural damage to the minaret Damage to the adjacent ceilings due to fallen

brick walls

Forgotten

anchorage

~60 cm

“Thank you for your attention…”

Acknowledgements: Universiti Teknologi Malaysia for supporting the investigation, and Dr. Mohammadreza Vafaei (Faculty of Civil Engineering, UTM) for leading the investigation works in Ranau (11-15 June 2015).