by ir prof paul pang assistant director/existing buildings 1 buildings department tackling concrete...
TRANSCRIPT
by
Ir Prof Paul PANGAssistant Director/Existing Buildings 1
Buildings Department
Tackling Concrete Problems in
Old Buildings and their Control
Advantages
Durable Economical Environmentally friendly Fire resistant Easy maintenance Versatile Customized design
To assess the overall condition
To ascertain the extent and cause of problems
To determine structural performance and integrity
Investigation and Assessment
Visual Inspection
Physical Appearance intact, loose, stained, cracked, deformed
Concrete Colour below 300℃ normal 300 – 600 ℃ pink to red
600 – 950 ℃ gray to buff above 950 ℃ buff
Detailed Investigation
In-situ Tests destructive, non-destructive
Structural Assessment upon inspection/investigation results
Investigation & Assessment
Diagnostic Tests
carbonation depthtell-taleresistivity measurement
infrared thermography half-cell potential mapping cover-meter
Diagnostic Testsground penetration radar impact echo test Schmidt hammer test
rebar tensile test concrete coring ultrasonic test
The Worst Credible Strength (WCS) is used for assessment
WCS = 1/n . Σfi (1-0.2/√n)
where n = no. of samples (n ≥3) fi = sample strength
Investigation & Assessment
Determine overall repair regime
Stop at source
Provide protection
Replace defective concrete and re-bars
Provide structural strengthening
Mitigation Measures
Control
Legislation Enforcement Support and assistance to building
owners Publicity and public education
Legislation
Buildings Ordinance (B.O. s24, s26, s26A, s28)
Minor Works Control System (MWCS)
Mandatory Building Inspection Scheme (MBIS)
Mandatory Window Inspection Scheme (MWIS)
Enforcement on Dilapidated Buildings
Respond to reports from public & other parties
Issue advisory letters and repair orders
Prosecution
Government contractor action
Planned programmes (large scale operations)
Enforcement on Dilapidated Buildings
Statutory orders issued in the past 3 years
Repair orders (building) – about 2 300 Repair orders (drainage) – about 1
500 Investigation orders – about 450 Demolition orders – about 10
Government contractor action on repair – about 1 350
Planned Programmes
Operation Building Bright (OBB)
Large Scale Operation on repair and investigation
Mandatory Building Inspection Scheme (MBIS)
Mandatory Window Inspection Scheme (MWIS)
Operation Building Bright
One-off operation launched in 2009 by DEVB, HKHS and URA
Financial and technical assistance to owners
About 1 500 Category 2 composite and domestic buildings aged 30 or above will benefit
Large Scale Operation
Repair or Investigation of Buildings, for Enhancement, with Age Under Thirty Years (REIN-BEAUTY)
- 500 target buildings per year, aged below 30
Inspection of buildings aged 50 or above - about 4 000 buildings
Inspection of cantilevered slab canopies - about 3 700 buildings
MBIS and MWIS
Preventive Measures
Owners of target buildings are required to inspect and repair their buildings and windows regularly
2 000 MBIS target buildings per year
5 800 MWIS target buildings per year
MBIS
MBIS Features
Target BuildingsPrivate buildings aged 30 years
or above (except domestic buildings of 3 storeys or less)
Inspection ItemsCommon parts of buildings
and features on theExternal walls
Inspection Cycle10 years
MWIS
MWIS Features
Target BuildingsPrivate buildings aged 10 years
or above (except domestic buildings of 3 storeys or less)
Inspection ItemsAll windows of individual units and common parts of buildings
Inspection Cycle5 years
Minor Works Control System (MWCS)
Simplified System for the carrying out of
minor building works
Class 1: 44 items Class 2: 40 items Class 3: 42 items
Support and Assistance to Owners
OBB MBIS
Building Safety Loan Scheme
Integrated Building Maintenance Assistance Scheme