construction practices : the good, the bad & the …...alam md. nurul senior structural...
TRANSCRIPT
Alam Md. NurulSenior Structural Engineer, ADPC
Senior Structural Engineer
Construction Practices : The Good, The Bad & The Ugly!
(Case studies)
The only alternative to risk management is crisis management --- and crisis management is much more expensive, time consuming and embarrassing.
JAMES LAM, Enterprise Risk Management, Wiley Finance © 2003
Without good risk management practices, government cannot manage its
resources effectively. Risk management means more than preparing for
the worst; it also means taking advantage of opportunities to improve
services or lower costs.Sheila Fraser, Auditor General of Canada
Why do we need Risk Management?
The column sizes were comparatively small, compared to a standard 8-9 storied Industrial
building, which might facilitated the sudden collapse.
Building Collapse in Savar
Heavy Overhang The presence of heavy overhang is another major cause to as appeared from
the original shape of the building (Please see photo). This might have caused the failure of the
on the upper floors of the building.
Source: The Daily Star
6’ Heavy Overhang
A Fatal Crack & Progressive Collapse
It was the rebar or the cement that
might be insufficient, for which a crack
was spotted on Rana Plaza's seventh
floor by workers on Tuesday, a day
before it collapsed. News media
reported that cracks had been
discovered in the building the day before
and people were requested to evacuate
the building. The shops and the bank on
the lower floors immediately closed, but
garment workers were told to return the
following day, their supervisors declaring
the building to be safe. The crack might
be due to lack of sufficient
reinforcement, since the collapse was
sudden and brittle in nature. The top
floor fell on the floor beneath and the
impact was too strong for the lower
story to withstand, and the entire
structure collapsed, [3] which might show
the characteristics of progressive
collapse.
A Fatal Crack followed by the progressive collapse happened due to heavy weights from 6 Generators and also from Industrial Use
Occurs when first story
much less stiff than
stories above
Typical damage –
collapse of first story
Gujarat EQ
Soft story
13
Soft Storey
14
Soft Storey
15
Soft Storey
Without soft storey
Soft storey
Effects of 1997 Earthquake
HOUSES, GOOD AND BADFor shape of the house, the simpler and more symmetrical the better. When lateral forces work to pull the building apart, shapes with roughly equally sized walls distribute that force more efficiently.
Footing on Soft Soil
The building was located in the marshy
land which is recently filled in with
garbage and loose soil. The collapse
after shaking in the nearby buildings
gives the evidence of the low laying
areas of the surrounding communities.
Mr. Russel, a local resident said,
“people residing neighboring areas felt
a shaking effect while the building was
collapsing”. The quality of the
underneath soil may have the major contribution in the collaps
Recent infill lands Adjacent to the Collapse Site
Recently filled area
liquefaction
Poor Workmanship and use of Low Strength Materials might be another issue for the collapse.
From the site it seemed that the quality of the materials and workmanship was not complying
with the standard practice.
Poor Construction Materials Used in the Building
• Low Strength • Brittle • Strong beam, weak column • Beam-column joint failure
Ductility
BAD BRICKEarthquake-resistant houses rely on workmanship and materials, including high-quality bricks. Build Change advises homeowners to avoid curved or warped bricks with cracks or chips
GOOD BRICK"When hit together, good bricks make a clink sound, not a dull thud," says the Build Change builder's manual.
BAD GRAVELWhen choosing gravel for mixing concrete, crushed, angular rocks are better. Rounded rocks decrease the available bonding area for concrete particles and lessen overall strength.
GOOD GRAVELThe best kind of gravel for mixing concrete is crushed stone.
BAD MASONRYBad masonry means weak walls. Here, thedistance between bricks is uneven, thejoints between bricks are not staggered farenough apart, and the joints themselvesare not completely filled with mortar.
GOOD MASONRYHere, the bricks are horizontally straight,vertically plumb and the joints betweenbricks are 1.2 cm thick or smaller.
Building collapses on adjacent houses in Old Dhaka, 2012
(a) Collapsed portion in other
building (b)Improper Reinforcement (c)Assessment Survey (d)Narrow Stairway
Building collapses on adjacent houses in Old Dhaka, 2012
Collapsed Portion Demolished portion by the owner
Building collapses on adjacent houses in Old Dhaka, 2012
Short column effectsShort column problem may arise due to arrangement of infill walls or other non-structural, architectural member. Sometimes, the infill walls are shorter than the column. The top of the walls may be opened for lightening purposes in schools, hospitals and apartments.
Vulnerability Factors
Short column effect…...
What do you think about it?
