; A six story commercial building collapse in Accra, Ghana
in November 2012. Is been over six months since the Melcom building collapse and yet still we are still waiting on the government to explain the cause of the collapse and the way forward. Initially my view was to wait on the investigation been conducted by the government as to the cause of collapse especially as I wasn’t privy to the forensic data obtained from the site which will shed more light to the cause of the building collapse. However with the passing months, it has become apparent that after the initial hype, nothing will be done to address this issue. Since the Melcom disaster, we have experienced at least two more building failures and nothing has been done to address the issue. Thus from my bird’s eye view and general knowledge in geotechnical engineering and project management, I have attempted to at least shed more light on this recurring menace in Ghana.
Probable Cause of Building Collapse
Eye witness accounts documented in the print media noted the building had developed varying degrees of cracks. Cracks were evident in the buildings walls and columns. In addition on the day in question, a loud bang was heard in the lower floors of the building just before the building collapsed. All these developments help provide clues as to the reason some of the contributory factors to the building collapse.
Building foundations are required to be proportioned to withstand all anticipated loads. A limit state is reached when a structure no longer fulfills its performance requirements. An ultimate limit state corresponds to the maximum load carrying capacity of the foundation and can be reached either through structural or geotechnical failure. A serviceability limit state corresponds to loss of serviceability, and occurs before collapse. Based on the eye witness accounts, the building most likely suffered a bearing capacity failure. The bearing capacity failure was a result of a punching shear failure of the building foundation elements. Typically punching shear failures are characterized by the vertical shearing around the perimeter of the footing and compression of the soil immediately below the footing. This failure mode occurs when the building loads exceeds the shear strength of the foundation soils. The punching shear failure led to large settlement of the building structure and this was evident through the large diameter cracks that had developed throughout the building. Often large settlements of the structures occur prior to a bearing capacity failure and such settlements lead to the impairment of the serviceability of the structure. Thus although the building had not reached an ultimate limit state of failure, the building had reached its serviceability limit state and should have been evacuated when these cracks were first evident. On the day of collapse, I believe segments of the already failed building foundations rotated or tilted due to excessive loading on the already weakened structure. This could have occurred through the high patronage of the shop on this date or cumulative excessive loading from the stores merchandise. The sudden tilt or rotation of the building foundations most likely led to cracking in the lower floor slabs and columns. This helps explain the sudden loud noise some witness described as a “bomb” in the lower floors prior to the building collapse. Once the slabs and footings on the lower floors collapsed, the whole building collapsed through a progressive collapse failure mechanism.
The foundation failure in my view was the primary cause of the building failure but this does not negate the importance of other factors such as shoddy construction and the use of inferior or building materials for the building construction. All these factors contributed to a certain degree to the building collapse. A forensic investigation of the failed building by the Ghana Institute of engineers should shed more light on this. Threats To The Facility The main categories of threats were likely to have an impact on the building collapse includes; faulty construction and the lack of standard building code enforcement. Under a microscopic view, the main factors driving these threats stemmed from “accidents” which are defined as human errors which will likely impact the performance of the facility and can be prevented and the prevailing economic conditions in developing countries. Random threats such as natural disasters resulting from seismic activity could also be a factor as the building was located in a known seismic prone region.
Accidents were identified as the most dominant threat likely to affect the building. Various levels of human error and negligence during the buildings construction and utilization periods led to the ultimate failure of the building. Some of the human errors included; Contractors/Owners: The lack of financial resources for the contractor or the financial stability of the owner is always a major source of risk to the project.
Contractors can become an inherent risk to the facility depending on their level of technical knowledge. The contractor’s construction means and methods also pose an inherent risk to the building facility. Aje et al (2009) study on contractor management capabilities on cost and time performance on construction projects in Nigeria concluded that contractor management was one of the most important factors likely to determine the success of any construction project.
Factors such as contractor experience, management knowledge and contractor quality control program were very relevant to the success and long term performance of any construction project.
The preliminary report on the cause of failure indicated the contracted used inferior quality concrete which ultimately had an effect on the integrity of the building and its ultimate failure. In a country where concrete is mostly batched onsite, it is believed the building contractors did not utilize adequate cement during the concrete batching process. The concrete placed was likely to have exceeded the water cement ratios due to excessive watering down of the concrete or not using the adequate amount of cement during the batching process improper onsite. A move which would have likely been intended to cut down on costs without the contractor or owners with total disregard to public safety. Routine sampling and testing of construction materials is only done on large scale government projects and thus was not done during the construction of this building to ascertain the strength of the concrete that was being batched on site. In addition, bearing capacity tests were not done on the building subgrade soils to ascertain the bearing capacity of the foundation soils to ensure the subgrade soils met the design bearing requirements for the anticipated building loading. The building is likely to have suffered a bearing capacity failure due to settlement and rotation of the building foundations which was evident in the numerous cracks that was experienced in the building walls, slabs and columns.
Accra Metropolitan Authority (AMA): AMA’s culpability in this failure as a state agency cannot be overemphasized. The Accra Metropolitan Authority is responsible for ensuring the safety and structural integrity of buildings in the Accra Metropolis. Representatives of AMA were quick to blame the failure on the fact that the building was constructed without adequate the necessary permits in place. It is unimaginable to think this structure was erected and utilized and the AMA claim total ignorance of its existence. Financing for projects in developing countries like Ghana is always a threat to the success of many projects in Ghana. Due to the harsh economic conditions, contractors and owners alike are always looking for ways to cut costs on their project. The lack of oversight from this cost cutting measures can always lead to severe consequences for the project. Thus the AMA and other government agencies alike need to formulate an effective means of monitoring upcoming projects.
The AMA serves as the main form as the main form countermeasures put in place to monitor construction projects in Ghana. They issue building permits after reviewing designs and also occupancy permits prior to approving the structure for use. The threats of projects being halted or not receiving occupancy permits always serves as a deterrent to building owners, however as discussed, due to the scarcity of resources, these institutions are almost rendered in-effective. The rich in society always by pass the law by bribing building officials who then turn a blind eye to their projects.
Building Management: The competence of the building management also has a significant impact on the long term performance of the building. The lack of a periodic maintenance procedure for the building was also a failure of the part management staff of the facility and also a direct threat to the long term performance of the facility as designed. In addition, the facilities end user is also alleged to have used the upper floors as a warehouse facility. This development could have led to the building being overloaded or exceeding the safe design loads. Seismic Activity: Risk from the natural environment was also a factor that could impact the success and long term performance of the project. Although Ghana as a whole is not very prone to natural disasters, the building being located in a seismic zone was always prone to natural disasters from earthquakes and earth tremors.
According to a study done by Dr. Paulina Amponsah of the Ghana Survey Department published in the Annals of Geophysics" Historical Earthquakes of magnitude greater than 6.0 and current local tremors with magnitudes ranging from 1.0 to 4.8 on the Richter scale have been recorded since the establishment of the seismograph station in Ghana" (Amponsah, 2004). This study shows the daily threat that was eminent to structures that have been built in Accra and its environs. The effect of the building foundation and structural integrity of the building as a whole cannot be over emphasized especially if the building was not designed to withstand seismic activity.
According to the Ghana Geological survey department, the last known major seismic activity in Accra was recorded in 1997, since then minor earth tremors have been recorded periodically in the region reported . Any major seismic activity would have been detected or reported by the survey department. In addition, the effect of seismic activities are usually not localized to one structure and would have been felt by multiple structures in the vicinity, thus the likelihood of a seismic activity causing the failure was very minimal. HISTORICAL FAILURES OF PUBLIC INFRASTRUCTURE 5 The Way Forward The economic situation in Ghana is also a major driving factor when building failures are analyzed. The decision to use inferior quality products, poor construction methods and the in-action of the building management can all be traced to the economic factors in the country. The inefficiencies in the work of the building officials are all a direct result of the economic conditions in the country. According to a study done by Ofori (1994), technological advancement always requires a certain level of financial resource input, favorable economic conditions, the required administrative support, physical infrastructure and institutions that can spearhead the new technology. In developing countries such as Ghana, these factors tend to be non-existent or very weak. In an environment where all these factors are lacking, there is always the threat of structural failures emanating from the lack of one or more of the reasons mentioned above.
Traditionally risks in the construction industry in Ghana have been managed instinctively, with risks remaining implicit based on judgement and experience over the years by stakeholders. For example Agyakwa-Baah (2007) observed that project risks are dealt with in an arbitrary way by adding 10% to the project cost as contingency. According to Godfrey (1996), a systematic approach will help identify, assess and rank risks thus making the risks explicit. The government should utilize such an approach to get a handle on the degree of vulnerability in the current system. Surveys can be conducted amongst stakeholders in the building industry such as contractors, designers, owners and building regulators to get an idea of what constitutes the greatest risk to construction projects in Ghana. The risk factors identified can then be ranked and dealt with accordingly. At a minimum, the government should adopt a multi-level approach to ensure that building projects are built to the acceptable design standards. There should be a change in government policy regarding the acceptance of construction projects in Ghana. Construction material testing is currently enforced only on government projects. These laws need to be extended to the private sector as well. In addition, contractors have to undertake routine certification programs prior to being issued licenses as builders. These certifications must be renewed periodically to ensure the contractors stay current on the acceptable building practices. The government should privatize construction material testing to civil engineering firms who can then be held accountable if any projects they certify fail. The government inspectors can then perform a final inspection on construction projects once the private HISTORICAL FAILURES OF PUBLIC INFRASTRUCTURE 6 firms have certified the projects just as a precautionary measure to check on the private firms. This will not only create a new stream of jobs for upcoming graduates in the construction industry but will also help save the government institutions like the AMA money on the already scarce resource they have to go by.
Design professionals also have to be held liable for their designs, due to the lack of prosecution; design professionals do not take a serious approach to their designs as they are seldom held accountable even in the event of failure. In the same regard, owners, public officials, contractors etc. whose negligence lead to building failures have to be prosecuted accordingly. These measures should raise the standard of professionalism amongst all the stakeholders in the construction industry. With such a multifaceted approach, the number of structural failures should reduce dramatically.
The author of the piece was not privy to any of the design data or forensic data for the failed building. The views proposed are based on the general acceptable standards of civil engineering practice and is in no way conclusive on the subject matter. The identified threats and the methodologies proposed are intended to serve as the basis of a risk management tool to help prevent the re-occurrence of such national disasters in the near future and not serve as the basis for prosecution of any parties involved.
The author is a practicing geotechnical engineer in the United States. Any views or comments can be directed to the email below or shared on this platform.
Author: Janis Asare-Bediako, PE, PMP
Tel: 001-5714676155
Email: ([email protected])
REFERENCES
Agyakwa-Baah, A. (2007). Stakeholders Perceptions of the causes of Delay on Construction Projects. Bsc. Dissertation. Kwame Nkrumah University of Science and Technology, Ghana. Aje, O.L., Odusami, K.T. and Ogunsemi, D.R. (2009). The Impact of Contractors Management Capability on Cost and Time Performance of Construction Projects in Nigeria. Journal of Financial Management of Property and Construction, 14(1):171- 187. Amponsah, (2004). Seismic Activity in Ghana, Past, Present and Future. Annals of Geophysics, Volume 47. April/June 2004.
Godfrey, P. (1996), Control of Risk: A Guide to the Systematic Management of Risk from Construction, Construction Industry Research and Information Association, London.
Mills, A. (2001). A systematic approach to risk management for construction. Structural Survey, 19 (5): 245-252.
Ofori, G. (1994). Construction Technology Development: Role of an Appropriate Policy. Engineering, Construction and Architectural Management, 1(2): 147-168.