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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). 1 STRUCTURAL SPECIMENS FROM DESIGN TO CONSTRUCTION DESIGN UNDER CONSTRUCTION 2 STRUCTURAL SPECIMENS: COLLAPSED AND IN-SERVICE COLLAPSED IN-SERVICE 3 CASE FOR ADEQUATE STRUCTURAL SUPERVISION TO PREVENT COLLAPSE OF BUILDINGS IN NIGERIA 4 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. 5 CASE FOR ADEQUATE STRUCTURAL SUPERVISION TO CURB BUILDING COLLAPSE 6 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 7 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 8 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 9 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. 10 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. 11 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 12 13 PLATE 3:INTRODUCED PERIMETER COLUMNS TO SUPPORT ADDITIONAL FLOOR 14 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 15 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. 16 17 DITCHES ENCOUNTERED ON SITE BUT NOT CAPTURED IN DESIGN 18 DOUBLE-SIZED COLUMNS WITH TIE-BEAMS 19 EINGINEERING BUILDING UNDER CONSTRUCTION EINGINEERING BUILDING IN SERVICE CASE FOR ADEQUATE STRUCTURAL SUPERVISION 20 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 21 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. 22 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. 23 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. 24 THANK YOU FOR LISTENING 25