Saturday, March 19, 2005

Tsunami and its implications for civil and structural engineers

The following article that appeared in the ISLAND on 03/19/05 was sent in by Ananda

By Felix Weerakkody
The recent Tsunami brings into focus the devastating consequences of earthquakes and their effect on Civil and Structural Engineering works. Prior to the tsunami, the buildings in Sri Lanka were designed and constructed on the assumption that Sri Lanka was too far distant from tectonic plate boundaries and therefore not susceptible to earthquakes. Consequently Structural Design Engineers were not required to design to a Seismic Code of Practice and structures designed and constructed to date have not been designed to withstand earthquakes of any magnitude.

Risk of earthquakes

The article titled "How Vulnerable Is Sri Lanka To Earth Tremors?" by Professor C. B. Dissanayake ( Daily News of 31st December 2004,) raises concerns with regard to future structural designs. Prof. Dissanyake draws attention to the formation of a new plate boundary close to the South Western coast of Sri Lanka stating that Sri Lanka is no longer far away from a hyperactive plate boundary. He proceeds to state that a strong earthquake hitting Sri Lanka cannot be ruled out and that in future builders and architects will have to bear this fact in mind.
Prof. Tissa Vitharana, the Minister for Science & Technology in the article ‘Tsunami: some misconceptions and misrepresentations ‘(Daily News 12th February 2005) states "in view of the separation fault that is developing about 400 kms south of Sri Lanka in the Indo-Australian tectonic plate, both local and foreign geologists have warned that the present increasing trend of earth tremors would lead eventually to damaging earthquakes in Sri Lanka.

It is also relevant to consider the obviously strong earthquake in Sri Lanka in 1615. Considering the fact that the population was small and that there were no multi storey structures, the destruction indicates that it was a major one.

If risk from earthquakes now becomes inherent or inevitable due to the formation of a new plate and its proximity to Sri Lanka, it has to be faced and dealt with. It is imperative that appropriate measures be taken. The basis on which Structural Engineering has developed is that it deals with risk and uncertainty by simplifying the structural analysis and codifying the essence of knowledge gained through a rigorous process of analysis and research.

Considering both the earthquake of 1615 and the concerns expressed by Prof Dissanayke and the Minister for Science & Technology, could Civil and Structural Engineers continue to design to a code of practice that does not take seismic loading into account? Should they incorporate seismic design loads into their analysis and use a seismic design code of practice?

What of the existing structures, particularly the high rise reinforced concrete structures which are known to be more vulnerable to earthquakes due to the low ductility of concrete?

Earthquake Engineering

Since the first world conference in Earthquake Engineering held in 1956, there have been significant developments in knowledge of the nature of earthquakes and the manner in which structures respond to earthquakes. The dissemination and collation of knowledge backed by research has enabled analytical techniques and codes of practice to be developed. These have been used to design and construct structures which can withstand earthquakes.

The new Eurocode 8 which addresses the design of structures for earthquake resistance adopts a design procedure to satisfy a life safety objective. This implies that a structure may be damaged but that it must not collapse. In this way loss of life can be prevented. This objective is achieved by designing a structure which combines essential characteristics ie. Strength to resist the earthquake forces and ductility to enable the energy transmitted to the structure by or from the earthquake to be dissipated. The code also recognizes the fact that existing structures may be found to be vulnerable and consequently need to be assessed and retrofitted to withstand future earthquakes.
The Professional Civil /Structural engineer

The structural design of buildings and other civil engineering work is carried out by civil and structural engineers who can be categorized as Professional Engineers. A professional is one who is in possession of specialized knowledge and skills judiciously collated from a continuously developing, vast and complex body of knowledge through a process of rigorous training and study. They belong to a professional body which requires them to follow a specific code of conduct in their professional affairs and directs them towards social good. Their advice is sought by clients who accept their guidance without question. Civil and structural engineers belong to such professional bodies as the Institution of Engineers Sri Lanka or its equivalent such as the Institution of Civil Engineers or the Institution of Structural Engineers etc. In the execution of structural design work a Structural Design Engineer is required to conform to a code of conduct laid down by the professional body to which he belongs. Some relevant excerpts from the Institution of Structural Engineer’s Code of Conduct are that its members, Have regard to the public interest and to the interests of all those affected by their professional activities. Take reasonable care to ensure the safety and serviceability of structural engineering work entrusted to them. The Institution of Structural Engineers defines Structural Engineering as the Science and art of designing and making with economy and elegance buildings, bridges, frameworks and other similar structures so that they can safely resist the forces to which they may be subjected.
Some cynics might say that a vast number of buildings are neither elegant nor economical but no ‘Professional’ Engineer will deliberately compromise on safety. He/she will design a structure able to safely resist the forces to which it may be subjected during its design life.
Legal implications, negligence and the standard of skill and care

In Civil Law, liability can arise under the tort of negligence for the death or injuries that may occur as a consequence of an act of omission or incompetence on the part of a professional in the course of his profession. The standard of skill and care required of a professional in the execution of his profession was established in the case of Bolam v Friern Barnet Hospital Management Committee [1957] 1 WLR 582 and further exemplified in the case Eckersley v Binnie and Partners [1988] 18 Con. LR 1 which is more relevant to Engineers. The judgement in this case reads thus. A professional man should command the corpus of knowledge which forms part of the professional equipment of ordinary members of his profession. He should not lag behind other ordinary, assiduous and intelligent members of his profession in knowledge of new advances, discoveries and developments in his field. He should be alert to the hazards and risks inherent in any professional task he undertakes to the extent that other ordinary competent members of his profession would be alert. He must bring to the professional tasks he undertakes no less expertise, skill and care that ordinarily competent members would bring but need bring no more. The standard is that of the reasonable average. The law does not require of a Professional man that he be a paragon combining the qualities of polymath and prophet. A professional is therefore required not only to avail himself of current and new knowledge with respect to his profession but also to be alert to the hazards and risks inherent in any task he undertakes. Failure to do so could leave him vulnerable to litigation. A claim for negligence based on ‘the duty of care’ against a professional may require the following.

a) Conduct which falls below the standard expected of a professional in the execution of his expertise.
b) A co-relation between the work performed by the professional and the adverse consequences that may have resulted.
c) That it was foreseeable that the conduct of the professional concerned was likely to result in the adverse consequences that have occurred.

It takes a minimum of 7 years of study, training and skill for an engineer to acquire the first of his professional qualifications. Along with the privilege of having a few letters after one’s name comes the duties, obligations and liabilities of the profession. We now have a new generation of Sri Lankans who are better informed, and are well aware of the universality of common law, technical standards and rights of the individual. The word tsunami and earthquake are entrenched in the national consciousness. No longer will it be possible for any individual to plead ignorance or excuse lower levels of technology. Inhabitants and owners of any structure will be aware of safety issues. An expert of the calibre of Prof. Dissanayake has stated that there is a distinct possibility of seismic activity affecting Sri Lanka. Under such circumstances a Structural Engineer who continues to design without taking seismic conditions into account could be said to be failing in "duty of care" Should he not utilize the body of knowledge available with regard to seismic design when executing future design work? If he fails to use a seismic design code and in the event of an earthquake which results in injury or loss of life will there not be a direct link between his work and the consequences? His conduct would then be considered ‘likely to result in the adverse consequences’. Therefore a structural engineer who continues to design as in the past may unknowingly place himself in a susceptible position and be liable for legal action. At present it is not mandatory that the structural design of any building be executed by a certified and registered structural engineer. Furthermore there is no mandatory requirement to archive a set of the structural design drawings and design calculations for future reference if a retrofit is required.

These are some of the issues that require immediate attention. One can only hope that steps will be taken to appoint a group of professionals to consider the following.

a). To set the design criteria for future structural design
b). To set policy for the appraisal of existing structures that could be vulnerable to seismic activity for the purpose of retrofitting them.
c). To formulate a policy with regard to structural design procedure

So that structural designs for multi-storey buildings be undertaken only by professionals certified by the Institution of Engineers Sri Lanka. and copies of all design drawings and design notes to be archived in a repository so that in the event of a calamity, investigators will have the information to protect the innocent and compensate the affected.

Conclusion

It may be relevant to consider the statistics obtained from some recent earthquakes. Iran (Bam, 6.3 on the Richter scale on the 26 Dec 2003 with 30,000 fatalities) India (Bhuj Gujarat 7.6 on the Richter scale on the 26 Jan 2001 with 19,000 fatalities) Turkey (Izmit 7.4 on the Richter scale on the Aug 17 1999 with 16,000 fatalities).

In the aftermath of these three events, investigations conducted on the collapsed buildings clearly indicated that the vast numbers of deaths and injuries were caused by the collapse of buildings that did not conform to required structural design standards. The damage was compounded by shoddy construction where it was obvious that specifications had been disregarded or compromised.

In Bhuj, Gujarat, whilst some structures were able to withstand the earthquake and remained intact, other multi storey reinforced concrete buildings were subject to complete collapse, indicating that poor quality construction had aggravated the damage. Soon after the earthquake, 37 cases were filed against builders, architects and engineers for culpable homicide and criminal conspiracy.

There cannot be a statute of limitations for liability where poor design and construction leads to loss of life.

It may be relevant to compare the earthquake that struck California on the 23 of December 2003 with the earthquakes mentioned above and in particular with the earthquake that struck Iran. The magnitude of the earthquake to strike California which was 6.3 on the Richter scale was of the same magnitude as the earthquake in Iran. In the California earthquake there were only three fatalities. There were 30,000 recorded deaths in Iran. The principle reason for the very low incidence of fatalities in California is that the buildings are designed to earthquake resistant design codes and constructed to the required specifications under strict supervision and stringent standards.

In conclusion I would like to quote Prof Tissa Vitharna (Daily News 12th February 2005) "In the above context the ongoing reconstruction programme should not be a return to the past with all its dangers to life and property. It must be a scientifically planned modern approach that would ensure minimal loss of life and property in the future".

Felix Weerakkody B.Sc.(Eng.) Hons.(Sri Lanka), Grad.Dip.Struct.Eng.(Australia), MBA(Sri Lanka), FICE (U.K), C.Eng. FIE (Sri Lanka), MIE (Australia.) CP.Eng, is working overseas at present as a senior lecturer in the Institute of Technology Brunei. He has over 30 years experience in civil engineering design, construction and management having managed a variety of diverse projects in Sri Lanka, Brunei, Australia and Indonesia. Major projects executed include large housing schemes, irrigation and river diversion schemes, roads and bridges, water supply, flood control and drainage schemes, industrial complexes and multi storied buildings.

Tsunami and its implications for civil and structural engineers

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