rapid visual screening of buildings in guwahati city

RAPID VISUAL SCREENING OF

BUILDINGS IN

GUWAHATI CITYDr. Indrani Gogoi

Department of Civil EngineeringNITK Surathkal

DISASTERS IN THE BRAHMAPUTRA BASIN

• EARTHQUAKE• FLOOD• LANDSLIDE• EROSION• CYCLONIC STORMS

Major Earthquakes in the Northeastern Region in Recent Past

Railway lines, culverts and bridges cracked

7.1 July 2, 1930 Dhubri

Property damage 7.1 September 9, 1923

SW Assam

4500 km2 area suffered damage

7.6 July 8, 1918 Srimangal

Property damage 7.5 December 12, 1908

Myanmar

Property damage 7.0 August 31, 1906

Sibsagar About 1542 people died 8.7 June 12, 1897 Shillong plateau

Numerous earth fissures and sand craters

7.8 March 21, 1869

Cachar RemarksMagnitud

eYearPlace

Training Programme on RVS Study

• 22nd Review Meeting of State Hazard Safety Cell

• Chairman: Mr. V.K. Pipersenia, Principal Secretary to the Govt. of Assam, Revenue & Disaster Management Deptt.

• Decision to conduct a training programme on conducting RVS study as an earthquake safety initiative for Government/lifeline buildings





A five day programme was organised by the Department of Revenue & Disaster Management, DRM programme in coordination with Department of Civil Engg., Assam Engineering Institute, Guwahati for Engineers from different State Government Departments at Assam Administrative Staff College, Khanapara, Guwahati from 16th -20th July, 2007 and 2nd-6th March,2009.

• RVS Technique • Potential damage due to soil problems • Identifying Building types & Damage

scales based on Earthqukae Intensities Identification based on photographs – assignments

The Participants introduced to the following concepts:

IS: 1893 Part-I 2002

Technique Adopted for RVS:

Building Types in IndiaFrom the damage vulnerability considerations buildings in

India are classified as:Masonry load bearing wall building

Semi-dressed, rubble, brought to courses, with through stones and long corner stones; unreinforced brick walls with country type wooden roofs; unreinforced CC block walls

B

As above but one storey only having light roofA+

Rubble (Field stone) in mud mortar or earthen walls

A

DescriptionBuilding Type

As at C but having horizontal RC bands (IS: 4329, 13828).

C+

Masonry construction as at C but reinforced with bands & vertical reinforcement, etc (IS: 4329), or confined masonry using horizontal & vertical reinforcing of walls.

D

Fully dressed stone masonry or CC block or burnt brick walls built using good lime or cement mortar. Unreinforced walls but having RC floor/roof.

C

As above of only single storeys and/or better quality of construction

B+

_ Masonry load bearing wall building_ Masonry load bearing wall building

Reinforced Concrete Frame Buildings (RCF) and Steel Frames (SF)

MR-RCF with ordinary ERD without special details as per IS: 13920, without ordinary infill walls (Such walls may be earlier similar to C in masonry buildings; MR-SF with ordinary ERD without special details as per plastic design handbook SP: 6(6)-1972.

DMR-RCF/MR-SF of ordinary design without ERD or WRDC+

RCF without Earthquake Resistant Design (ERD) or WRD built in non--engineered way; RCF with hollow plinth (open ground storey); SF without bracings having hinge joints without ERD or WRD; RCF of ordinary design without ERD or WRD.

C

DescriptionFrame Type

MR-RCF with high level of ERD as per IS: 1893-2002 and special detail as per IS: 13920-1993 MR-SF with high level of ERD as per IS: 1893-2002 & special detail as per Plastic design handbook SP: 6(6)-1972.

E

MR-RCF as at E with well designed & detailed RC Shear walls MR-SF as at E with well designed & detailed steel braces & cladding; MR-RCF/MR-SF with well designed base Isolation

F

MR-RCF as at E with well designed Infill walls MR-SF as at E with well designed braces

E+

…………Reinforced Concrete Frame Buildings (RCF) and Steel Frames (SF)Reinforced Concrete Frame Buildings (RCF) and Steel Frames (SF)

Classification of damage to masonry buildings

Grade 2:Moderate damage (Slight structural damage, moderate non-structural damage)•Cracks in many walls fall of fairly large pieces of plaster.•Partial collapse of smoke chimneys on roofs.

[Restoration]

Grade 1: Negligible to slight damage (no structural damage, slight non-structural damage)• Hair Hair-line cracks in very few walls.• Fall of small pieces of plaster only.• Fall of loose stones from upper parts of buildings in very few cases. [Restoration]

Grade 5: Destruction (very heavy structural damage)•Total or near total collapse of the building

[Debris Removal & Reconstruction]

Grade 4: Very heavy damage (heavy structural damage, very heavy non-structural damage)•Serious failure of walls (gaps in walls), inner walls collapse; partial structural failure of roofs & floors.[Reconstruction & Restoration with partial Rebuilding/ Retrofitting]

Grade 3: Substantial to heavy damage (moderate structural damage, heavy non-structural damage)•Large & extensive cracks in most Large & extensive cracks in most walls, roof tiles detach.•Chimneys fracture at the roof line; failure of individual non-structural elements (partitions, gable walls).

[Restoration & Retrofitting]

GRADES OF DAMAGE TO RCC BUILDINGSClassification of damage to buildings of reinforced concrete

Grade 2 : Moderate damage (Slight structural damage, Moderate non- structural damages)•Cracks in columns & beams of frames & structural walls.•Cracks in partition & Infill walls; fall of brittle cladding & plaster.•Falling mortar from the joints of wall panels.

[Restoration]

Grade 1:Negligible to slight damage (no structural damage, slight non-structural damage)•Fine cracks over plaster over frame members or in walls at the base.•Fine crack in partitions & Infills. [Restoration]

Grade 4: Very heavy Damage ( heavy structural damage, Very heavy nonstructural damage)•Large cracks in structural elements with compression failure of concrete & fracture of rebar’s, bond failure of beams reinforcing bars; tilting of columns.•Collapse of few columns or a single upper floor.

[Demolition or Extensive Restoration & Retrofitting]

Grade 3: Substantial to heavy damage (moderate structural damage, heavy nonstructural damage)•Cracks in columns & beams column joints of frame at base & at joints of coupled walls. •Spalling of concrete cover, buckling of steel rods.•Large cracks in partition & infill walls. Failure of individual infill panels. [Restoration & Retrofitting]

Grade 5: Destruction (Very heavy structural damage)• Collapse of ground floor parts (e.g. Wings) of the building.

[Debris Removal & Reconstruction]

Probable damageability in few/ many buildings is determined using the above given tables and classified Given format is used for each building in the region of study Time required to do RV for any building is around 30 minutes

Format forRapid Visual Screening of Indian Buildings

for Potential Seismic Hazards

Site Visit: Assam Engineering InstituteGUIDED WALKING TOUR – ASSAM TYPE/ MASONRY BUILDING

AEI, Workshop Chandmari AEI, Auditorium, Chandmari

• To increase the capacity of the building so that at least it could be in the class D type

G4G3

CD

AEI • Workshop• Auditorium

RecommendationsDamage Grade

TypeBuilding

Interpretation of RVS

PWD Office Chandmari

•Retrofitting and upgradation to D type

G4B+


Type

Veterinary College Store House

GUIDED WALKING TOUR – RCC BUILDING

PWD Office Building ASEB Quarters

RCC Buildings

Veterinary College

Library Building

Recommendations – RCC BUILDING

Restoration/RetrofittingG3DLibrary

Retrofitting/DemolishG5/G4C/C+ASEB Housing, Ulubari

Repair and restorationG3DPWD Office, Chandmari


TypeBuilding

Outcome of the Program:• 5-day course proved fairly effective to train as

rapid Visual Screeners • Evaluation technique of many ill constructed or

seismically hazardous structures discussed• Participants were Engineers from: PWD, ASEB,

Water Resources, GMDA, Agriculture, GMC, Assam State Housing Board, PHE and Town & Country Planning.

Discussions:

• The type and damage grades associated with RCC buildings were found to be adequate for preliminary investigations

• No special scores (numerical) associated with the maintenance or state of degradation of these buildings

• Damage grade specific to Assam type houses in Seismic Zone V need to be addressed

• Flexible wall material, light roof, provision of timber bands/ lintels – higher score

• RVS format for Assam type houses need to be developed

Discussions:

• Basic Scores and the Modifiers as in FEMA 154 (2002)8 – different structural forms of buildings– pre-code penalty – post-benchmark positive attribute – different types of soil - dense, stiff and soft.

• Summation of scores is accurate– do not depend on the screener’s in depth knowledge

and judgment.• Helps in ranking the buildings for prioritizing the

repair and retrofitting process

rapid visual screening of buildings in guwahati city

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