Transcript case for adequate structural supervision to prevent collapse

THE NIGERIAN SOCIETY OF ENGINEERS
VICTORIA ISLAND BRANCH
PUBLIC LECTURE & PANEL DISCUSSION
ON INFRASTRUCTURE FAILURE AND COLLAPSE
Tuesday, 24th May, 2016
@ Oriental Hotel, Victoria Island, Lagos
TOPIC:
“CASE FOR ADEQUATE STRUCTURAL SUPERVISION TO
PREVENT COLLAPSE OF BUILDINGS IN NIGERIA”.
BY
PROFESSOR OBANISHOLA MUFUTAU SADIQ
M.Sc (Civil Eng), Ph.D (Struct. Eng) Kiev, MIASS, FNSE, FNIStruct.E,
Regd. Engr. (COREN).
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STRUCTURAL SPECIMENS FROM
DESIGN TO CONSTRUCTION
 DESIGN
 UNDER CONSTRUCTION
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STRUCTURAL SPECIMENS:
COLLAPSED AND IN-SERVICE
 COLLAPSED
 IN-SERVICE
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CASE FOR ADEQUATE STRUCTURAL
SUPERVISION TO PREVENT COLLAPSE OF
BUILDINGS IN NIGERIA
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Major structural collapses have occurred throughout recorded history. In fact,
collapses historically have helped to lead to better understanding of
structural performance and have contributed much to the art and science of
building design and construction.
This spate of collapse of engineering structures (Buildings, Bridges,
Masts, Towers, Dams etc) in the past years and the attendant loss of
lives and properties has been giving professionals serious concern.
The spate of collapse of buildings and other engineering structures in recent
years has called for great concern on the part of both government and
professionals especially in the built environment that something drastic and
urgent still needs to be done.
When one considers the fact that these structural collapses and failures
either under construction or in service are usually accompanied with loss of
lives and properties then there is need for more concern. If properties that
were lost during the collapse of a structure could be quantified, the price for
a life is unquantifiable.
Several engineers and researchers have conducted investigations into past
failure incidences and several reasons and causes have been identified
for these collapses.
But one should recognize and commend the Lagos state Government for
the serious steps and measures being taken to reduce the incidence of
building collapses in Lagos State. Some of these measures include:
 Demand for soil test report of a proposed building site with more than two
floors.
 Mandatory testing of building materials on site by the developer.
 Non-destructive testing of structural elements for strength before
completion of the structure.
 Filling of FORM C – certificate of structural stability and fitness for
habitation by professionals.
 Enactment into law the Lagos State Urban and Regional Planning and
Development Bill 2010.
 Forfeiture of a site on which a building collapsed.
 Criminal prosecution of the Engineers handling the project.
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CASE FOR ADEQUATE STRUCTURAL SUPERVISION TO CURB
BUILDING COLLAPSE
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The former president of the Nigerian Institution of Structural
Engineers (NIStructE) Engr. Dr. Victor Oyenuga (2010) enumerated general
causes of building collapse to include:
i.
ii.
iii.
iv.
v.
Design errors
Poor construction method/technology
Poor material quality
Poor steel reinforcement quality
Operational errors (putting additional storeys/floors for which the
original building was not designed or conversion of the structure)
vi. Non-existent geotechnical studies or inadequate soil investigation
or wrong interpretation of results of site investigation, leading to
adoption of wrong/inadequate foundation type(s)
vii. Corruption.
When a building collapses whether under construction or in service, the
issue of who is responsible among the professionals for its collapse has
never been resolved. Even the filling of form C – certificate of structural
stability and fitness has not pinned responsibility for collapse on any of the
professionals who signed the form.
In an attempt to establish a case for adequate structural supervision to curb building collapses the lecturer carried
out critical error analysis of the roles of each of the professionals in the built environment vis-à-vis their actions
and inactions in preventing the collapse of a structure. In order words, what amount of efforts
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does a professional put in to prevent collapse of a building? Or how much can the error of a
professional bring about the collapse of a structure?
Professor T.A.I. Akeju, an eminent professor of structural engineering, posited that involvement of
competent professionals to handle a building project doesn’t entirely guarantee its stability. The project
competently created on paper must be faithfully reproduced on the site. A structure is said to be as good
as its construction and NOT as its design. However, it is forbidden in engineering practice to go into
construction of a project without prior analysis and design. Now let me go into error analysis of the professionals.
1.
2.
3.
4.
The Architect: if the Architect commits an error in his architectural design, and the error is carried to
construction, so long as all other things are alright what we may have is a building that is defective in
aesthetics but the structure may not necessarily collapse. Furthermore, the power of the Architect in
preventing collapse of a building is minimal. The efforts of the Architect in preventing collapse of a
structure can be rated as 10%.
The Quantity Surveyor: if the QS commits an error in his project cost estimates, the result may be high
project cost or under estimated cost, but not necessarily collapse of the structure. The efforts of the
Quantity Surveyor in preventing collapse of a building can be rated as 7.50%.
The Mechanical & Electrical Engineer: if the Mechanical Engineer commits an error in the mechanical
services, the results may be that water is not getting to the top floors or sewage is not properly flowing. All
these may not lead to the collapse of the structure. Also, if the electrical services were faulty, part of the
building may not be getting light the fans/air conditioners may be malfunctioning, but the stability of the
building is not threatened by these errors. The efforts of the M & E in preventing collapse of the
structure can be rated as 3.00% each.
The Project Manager: The duty of the Project Manager is mainly organizational, in ensuring that materials
get to site on time and also timely completion of the project. The errors of the project manager hardly
contribute to building collapse. His efforts in preventing collapse of the structure is rated as 1.50%.
The Structural Engineer: The inability of the structural engineer to carry out proper site
investigations and errors in calculating design loads accurately can lead to collapse of a structure
either during construction or in service. Conversely, the good efforts of the structural engineer can
prevent ALL the causes listed above from causing the collapse of the structure. Therefore, the
efforts of the structural engineer in preventing collapse of a structure can be rated as 75%. To
stem the spate of building collapses in the country therefore, greater emphasis should be shifted to
construction supervision and the structural engineer should take the lead since major responsibility for
the safe delivery of the structure rests on him.
CASE IN
POINT:
ST. DENNIS
CATHOLIC
CHURCH
PLATE 1
PLATE 2
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To buttress the case for adequate structural supervision, three case studies are presented
here: one – a building that collapsed under construction; and two other buildings
that were salvaged through the good efforts of the structural engineer
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consultant who happened to be the lecturer of today.
Collapse of St. Dennis Church at Bariga
The building St. Dennis Catholic Church situated at Bariga collapsed under construction in
March, 2000. Two people were reported to have died. The inaugural lecturer led a team of
engineers from NSE Lagos Branch to investigate the collapse of the building which
comprised of detailed site examination of the debris and laboratory assessment of the
structural elements used in the construction.
The findings of our investigation were as follows:
I. Plate No.1 shows a heavily reinforced concrete column meant to carry four beams. The
column has Y10 and Y16, and each of the over reinforced beams was to be
supported by the column. Observation showed that this arrangement was faulty
structurally, in that a single column could not have been made to carry such heavy
loads, where there are other columns on which part of the loads could have been
distributed or transferred.
II. Plate No.2 shows the reinforcement of one of the beams. As can be seen, the stir-ups
are too many and too closely parked which did not conform to the spacing between stirups as required by the Code of Practice. Close observation of the arrangement of
reinforcing bars for the beams showed that Y25 bars were used as top reinforcement
from the beginning till the end of the beam while Y20 bars used as bottom
reinforcement terminating at the support (column) and not tied. Furthermore, as can be
observed in plate No.2, two of Y20 bars were used as the bottom reinforcement, while
four of Y25 were used as top reinforcement. This is structurally wrong, because for
suspended beams, the bottom reinforcement should be heavier than the top
reinforcement.
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iii. It was observed that one of the columns buckled at about 1.2m from the
base where column reinforcements were joined. Close observation also
revealed that the base of the column was started with 25mm diameter bars
up to the 1.2m mark. They were thereafter joined with 16mm diameter bars;
this definitely was a very wrong structural arrangement. This one ALONE
could cause collapse of the whole structure. In conclusion, collapse of
ST DENNIS CATHOLIC CHURCH building was due to poor construction
techniques, poor materials qualities and inadequate structural
supervision.
THE UNILAG COMPUTER CENTRE BUILDING.
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The computer Centre building of University of Lagos, located along
Oduduwa Rd, in UNILAG was initially designed as one storey block of
classrooms and offices. The contract was awarded and construction started
in March, 2002.
Around September, 2002, the University Council Committee on
infrastructure carried out inspection of some university’s projects. As at that
time, the first floor slab of the computer centre had already been cast. The
project was being executed under the ETF grants. When the committee got
to the computer centre project, the then Bursar intimated the committee that
the University had received more funds from the ETF and that more funds
were available for the centre. It was there and then decided by the
committee that one additional floor should be added to the structure.
THE CITS BUILDING
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PLATE 3:INTRODUCED PERIMETER COLUMNS TO SUPPORT ADDITIONAL
FLOOR
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PERIPHERAL COLUMNS AT THE REAR
Among the options that came to mind, the one that was found most
appropriate and cost effective was to introduce the round columns at the
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perimeter of the first floor slab. (Plate No. 3).
The column was designed for 225 mm diameter with 6Y16. They were
placed at 6m intervals in the front, back and left side views.
The purpose of these peripheral columns was to absorb the additional
loads from the incoming second floor slab thereby reducing to the
barest minimum the additional loads to be transferred to the foundation
as a result of the incoming additional floor.
Not only that, we also designed the incoming second floor slab as hollow
clay pot, with rib beams of 250mm depth by 100mm thickness and 75mm
rib slab thickness. The ribs were placed at 500mm centers. These were
done to further reduce the additional floor load coming to the foundation
which was already in place. Necessary checks were carried out to
ascertain the adequacy of the foundation to carry the entire structure.
Till date the computer centre is still standing. Construction was
completed in February 2003.
FACULTY OF ENGINEERING BLOCK OF CLASSROOMS AND
OFFICES
As a further emphasis on the case for adequate structural
supervision the completed faculty of Engineering block of
classrooms and offices is presented here.
Construction started in November, 2013. During excavation a deep
ditch was discovered at some parts of the site, and three of the
column bases were discovered to fall into the ditch.
The solution proffered was that the width of the three columns
that fell into the ditch were doubled and tied together, before they
were then tied to the other columns of the building.
The building has been completed and has since been in use as
shown in the background.
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DITCHES ENCOUNTERED ON SITE BUT NOT CAPTURED IN DESIGN
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DOUBLE-SIZED COLUMNS WITH TIE-BEAMS
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EINGINEERING
BUILDING UNDER
CONSTRUCTION
EINGINEERING
BUILDING IN
SERVICE
CASE FOR ADEQUATE STRUCTURAL
SUPERVISION
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Most of the causes of collapse listed above can be prevented during
supervision of the construction. So, a major way of steaming building
collapses is adequate and professional supervision. When there are
design errors, they can be corrected during supervision.
This therefore calls for critical review of the scale of fees as it is presently
configured. It appears the originators/designers of the present scale of fees
considered majorly the conceptual and design stages while undermining the
role of supervision. Now that the role of adequate supervision has been
brought to the fore, there is urgent need to review the scale of fees for
consultants in the built environment. Understandably the ACEN, NSE and
NIStructE are looking into this.
The present scenario in the scale of fees is that: Conception (25%),
Design (50%) and Supervision (25%). Taking the importance of
supervision into consideration now, the distribution should be as
follows: Conception (25%) Design (25%) and supervision (50%).
PROPOSAL FOR NEW SCALE OF FEES
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A new scale of fees that will incorporate the R F is hereby proposed,
taking into consideration the issue of Responsibility Factor as
enunciated in this presentation. This Responsibility Factor is
assigned 5% of the project cost and to be distributed amongst the
consultants as follows:
Structural Engineer
Architect
Quantity Surveyor
Mechanical Engineer
Electrical Engineer
Project Manager
-
2.5%
1.0%
0.75%
0.3%
0.3%
0.15%
5.00%
A new Professional scale of fees that incorporates the RF and the
strategic role of the structural engineer in preventing collapse of
buildings is being proposed.
CONCLUSION
 It is clear from the foregoing that one of the major ways to curb collapse of
buildings is through very adequate and thorough professional supervision
of the construction and the structural engineer has a major role to play in
this direction.
 A 5% Responsibility Factor against collapse is recommended to be
incorporated in the professional scale of fees, which is distributed among
the consultants based on critical analysis of the actions and inactions of
each of the consultants in preventing collapse of a structure.
 A new professional scale of fees that takes into account the recommended
5% responsibility factor and the strategic role of the structural engineer in
preventing collapse of structures is being proposed. This scale of fees can
serve as a working document for the committees of ACEN, NSE and
NIStructE that are presently working on the review of the professional
scale of fees.
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RECOMMENDATIONS
 The percentage distribution of the R.F can also serve as a guide for
professional charges for production of structural integrity report, which may
now be mandatory to be produced to Insurance Companies for issuance
of “a General Contractors All Risks Insurance Policy Certificate”.
Section 48 of the Lagos State Urban and Regional Planning and
Development Bill (2010) now compels a developer or owner of a
structure of more than two floors to submit to the Building Control Agency
All Risks Insurance Policy Certificate. Strict enforcement of this law can
curb building collapse.
 It is necessary to sound a note of warning to the Insurance Companies in
this regard, that they should demand for a Structural Integrity Report on
a structure before issuance of this Insurance Policy Certificate, and that
this structural integrity report should be signed by no other
professional other than a COREN Registered Structural Engineer or a
Corporate Member of the Nigerian Institution of Structural Engineers.
 Criminal prosecutions of ALL professionals handling the project
including the owner of the project.
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RECOMMENDATIONS FOR BUILDINGS
IN SERVICE
 It is recommended that every building be subjected to Structural
Integrity Test every three(3) years. This will then lead to the provision
of
Structural Integrity Report to be approved by the State
Government.
 Government should demand Structural Integrity Report for every
building that is:
1. Five years old and above and
2. More than two floors.
 This can be added to the responsibility of the building control
agency in the same manner they monitor/collect land charges.
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THANK YOU FOR LISTENING
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