Feature Article of Sunday, 18 November 2012
Columnist: Ohemeng, Yaw
Since the collapse of the 5-storey building that used to house the Melcom superstore at Achimota, there have been numerous comments from groups and individuals. Some are professional observations and some are emotional responses to a national tragedy. As tragic as the situation is, it offers the opportunity for the nation to learn and to put in place better practices. After the Ministry of Foreign Affairs fire, I wrote a professional piece expressing the fear then that the nation might not learn any lessons from the fire due to the composition of the investigative committee and the remit they were given. Then, as it is now with the Melcom tragedy, we are preoccupied with finding people to blame instead of using the tragedy to come up with lasting solutions.
It is my opinion that we should take time to have at least two sequential investigations. There should be an initial one to be conducted by technical experts who will determine the cause(s) of the collapse. Their report should feed into a much wider investigation that will look at institutional arrangements and failings, the lessons to be learnt, and any legislative response, should that be found necessary. It is to the initial technical investigations that I humbly make this input.
To determine the cause(s) of the collapse any technical committee that is set up should endeavour to answer these four broad questions:
1. What was the initiating event that precipitated the collapse of the building?
2. How did the building structure respond to the initiating event?
3. How did the structure fail? And
4. Was the mode of failure to be expected, given the initiating event and the structural provisions, and if not, why was that so?
It is only after answering these questions that we can explain what happened and ensure that future occurrences are minimised, if not altogether avoided.
Even though the prosecuting authorities and the public are eager to punish those whose actions or omissions led to the tragedy, we cannot establish culpability without knowing what the initiating event was. Most people who have commented on the tragedy are of the opinion that some shoddy work might have been done. If this is the case, it would have to be formally established. Thus one of the questions any technical committee should answer is: was it an external or internal event that precipitated the collapse? External events could include extreme environmental events (i.e. wind, earth tremors, etc.) or vibrations from nearby activities or external vehicular impact that took out some of the load-resisting systems or a nearby deep excavation that undermined the building foundations or an explosion. Internal events could include an explosion or impacts that took out some important load-resisting systems and elements or misuse of the structure: was the use of the structure in accordance with the design intent? The initiating event could be accidental or malicious or an act of God.
Every structure responds to the application of loads in a manner that depends on the magnitude of the load; the nature of the load; the mode of application of the load and the structural systems provided to resist the loads. The technical committee should find out what the building owner’s requirements were, set against what was provided. Did he intend to build a shop, an office or a mixed use facility? This may be inferred from the architectural drawings (if not explicitly recorded) or even from the title blocks of the drawings. Once this is established, the next task is to assess the competence of the designer in terms of the provisions he made to satisfy the building owner’s requirements.
In satisfying the owner’s requirements, the designer should have chosen suitable construction materials and selected suitable and appropriate structural and foundation systems within the spatial and site constraints. In addition, the designer should have sized and detailed the structural members and foundations with the aim of providing a stable structure:
a. That is sufficiently strong to carry the anticipated imposed loads and selfweight, and to transmit them safely into the ground;
b. That is sufficiently stiff to limit deformations of structural members and frames when subject to the most frequent loading regimes;
c. Whose foundation types and sizes limit settlement and most importantly differential settlement; and
d. That is sufficiently robust to limit the extent of damage when subject to accidental or unanticipated loading.
If it is established that the designer made provisions to achieve all the above objectives, the technical committee should be able to determine how the structure should have responded to the initiating event.
After establishing the initiating event and determining how the structure should have responded, the last leg of the technical investigation is to compare how the structure should have failed to how it actually failed. The stage would then be set to find explanations for the mode(s) in which the structure failed. The structural failure could have been as a result of: design and detailing flaws; the use of inferior, incorrect or inappropriate construction materials; construction flaws; misuse of the building or a combination of some or all of these.
A properly designed, detailed and constructed building should not totally collapse even when subject to unanticipated loading. The way to ensure this is to detail the structure for robustness where all structural elements are adequately tied together in the vertical and horizontal planes. This design step is separate from designing the structure to resist the anticipated loading regime. The aim of designing for robustness is to avoid the situation where damage to a portion of a structure can lead to other structural systems and elements (remote from the damaged part) progressively collapsing. Some refer to this as the ‘domino’ effect. UK design codes and Building Regulations have had robustness provisions since the Ronan Point incident in 1968. The provisions have been tightened further and clarified in the last few years. Lack of robustness also led to the collapse of the Murrah Federal Building in Oklahoma City in 1995 following a terrorist bomb. Since that time the USA has also incorporated robustness provisions in their building codes. Those who want to learn more about these two incidents can read about them by ‘googling’.
At the end of the investigations, the technical committee should issue a report that gives an engineering explanation to the tragedy by providing answers to the four broad questions posed at the beginning of the article. The report should also contain technical recommendations with regards to design provisions and building construction and supervision practices. As I have earlier pointed out, the technical committee report should be one of the inputs into a wider investigation that will address institutional arrangements, failings and challenges as well as legislative and enforcement inadequacies.
The prosecuting authorities are seeking to hold some actors responsible for the tragedy and there is no doubt that the technical report would be useful in this regard. Culpability has to be established between the building owner, the designer and detailer, the Specifier of the materials (if different from the designer); the contractor, the supplier of the construction materials; and the user. At this early stage, though, all of them (if they have been identified) can be nothing more than suspects in the investigation. All the police need to do, at this stage, is to inform them formally that they are suspects in the ongoing investigation; obtain caution statements; and then admit them to bails. It is premature to have taken two individuals (i.e. the building owner and a former official of the AMA) to court to have them placed in remand custody. What is even more baffling is the arrest and detention of the former AMA official without his employer being held corporately liable for his alleged commissions and omissions. There are a number of questions to ask about this particular arrest: did his employment contract state that he would be held personally liable for his actions whilst in the employ of the AMA? Was he given enough tools, training and resources to adequately perform his duty? All said, it is premature to detain anybody, let alone a public official whose actions probably reflected institutional inadequacies and failings rather than a personal dereliction of duty.
From a legal standpoint, the state may even struggle to establish culpability. Since the tragedy, a lot of people have mentioned non-adherence to the Ghana Building Code as a contributory factor. I spent four years studying civil engineering at KNUST and never once did I see or use the national building code. Does this code identify dutyholders with clearly stated responsibilities who can be held liable if something goes awry? Does the building code provide a list of approved design, loading and material codes to be used by building professionals? At KNUST, we were taught to British Codes and never once did we use an indigenous design code or standard. This was nearly thirty years ago. If it happens that we still do not have indigenous design codes and standards, on what bases is the state going to demonstrate negligence on the part of those arrested? This is of course for the lawyers and the courts to determine.
Whatever happens though, we must and should learn from this tragedy. We do lose lives needlessly in Ghana. This time let us act properly as a lasting tribute to those who lost their lives and all who have been traumatised by this tragedy. Our thoughts should be with them at this trying moment.
Dr Yaw Ohemeng