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).