23 November 2009

Ensuring the safety of built structures

By Dr Ling Tong Wei

(Published in ‘Campus & Beyond’, a weekly column written by Swinburne academics in the Borneo Post newspaper)

In October this year, 22 students fell into Kampar River when the Kuala Dipang suspension bridge collapsed. The tragedy caused the death of three of the students. Why did this happen?

Every year, many engineering students graduate and join the workforce as engineers in the various disciplines of the profession. With advanced technologies and knowledge, the world should be a better and safer place than before. However, there have been many building and structure collapses around the world this year. For instance, Terengganu Stadium Roof collapsed on 2 June (no death reported) in Malaysia; a 13-storey apartment under construction at Shanghai’s Lotus Riverside fell to its side in June (one death) and Jinjin Expressway Ramp Bridge collapsed at Tian Jin in the following month (six deaths); a portion of a partially built bridge for New Delhi’s metro rail network collapsed in July (five deaths).

With proper maintenance carried out from time to time, old buildings and structures can last for few centuries. However, the structures in Malaysia, China and India mentioned above, including the suspension bridge at Kuala Dipang, are newly built. Sponsored by a company, the Kuala Dipang bridge was built recently.

The failure of a structure may be due to many factors. The suspension iron-cable bridge at Kuala Dipang has a limit of 10 persons at any one time. If the limit of 10 persons is based on the weight of adults, we may assume that the weight of 10 adults is equivalent to that of approximate 20 children. However, when the bridge plunged into the river, it had at least 22 students, and this had overloaded the bridge. Moreover, a student said that a few students were jumping on and shaking the bridge before it gave away.

In this incident, the question that might arise from our doubt: is the limit of the weight of 10 adults appropriate? Especially, the bridge is used for the 1Malaysia camp with 298 primary school students, aged between 10 and 12.

According to news reports the iron-cable bridge is about nine metres long over the river. On the bridge, the distance between two people can be estimated to be 0.5 metre. With a nine-metre long bridge, it is possible to have 18 adults on the bridge at any one time, and this could overload the bridge easily. At this stage, it is still inappropriate to draw any assumptions or conclusions on the bridge collapse at Kuala Dipang. Clearly, an investigation is needed. No matter what the outcome of the investigation is, there is a lesson to be learned to prevent such tragedies from happening again.

In the construction profession, any construction involves a qualified person (QP), professional engineer and a builder. A QP basically is the one who assesses and endorses the feasibility of the proposed works, and submits the structural plans and calculations to the authority for approval. In building and structure design, structural adequacy and safety of structures are determined based on the ultimate limits, and the design actions (loading) have to be smaller than the design capacities (strength).

Even when there are no construction faults, a structure may fail if the loading is underestimated or the design capacities are miscalculated. To minimise mis-design, the Building and Construction Authorities (BCA) like the BCA of Singapore, require an accredited checker’s certificate in most QP’s submission for approval. The role of an accredited checker is to provide an evaluation report with independent structural analysis and design check calculations based on the QP’s submission.

QPs should be well experienced in the field, but independent review and checking should be encouraged even if it is not requested.

The authorities should also work closely with the Institution of Engineers Malaysia and other engineering organisations to review the submissions. Due to the confidential concerns, the QPs or the authority may engage a university to carry out the independent review and checking. Liability should not be borne by the lecturers or the university, since they engage in this kind of activity only in an advisory capacity. The industry benefits by having an independent third party expert review their construction.

For the university, the practice can provide industry-based learning for its students, and focused industry exposure and research to the lecturers. The lecturers will be able to illustrate their lectures with the real-world scenarios and equip students with the knowledge and problem-solving skills that are needed by the industries. Thus, the students will be more job-ready for the industries upon graduation. Otherwise, students may not be prepared to meet the real-life engineering challenges.

This year, there have been many tragedies around the world. For instance, the typhoons that hit the Philippines and Taiwan killed hundreds of people. An earthquake in Java, Indonesia, killed at least 57 people. Tragedies that are caused by natural disasters cannot be avoided. However, the tragedies due to structure collapses can be avoided or minimised. As engineers, public safety should be our first concern when structures and buildings are designed, constructed and maintained. This is not only to protect our reputation, but more importantly, the community.

Dr Ling Tong Wei is a lecturer with the School of Engineering, Computing and Science. He can be contacted at twling@swinburne.edu.my.