By Engr.Ghulam Haider
Once again a sad and depressing news surfaced on our regional newspapers: the girders of an RCC bridge collapsed in Hunza. One thinks, are our bridges made of Lego! Were they built by playing cards! Were the foundations floating in air! Eventually some important questions arise in our minds! Why is this much careless behaviour from the respective department and their management? Is contractor qualified enough to carry out this job? Has he deployed the adequate resources? Was there any project management plan? To the dismay of the common people, most of the questions are answered with a big NO!!
This news is equally saddening and worrying. Saddening in the sense that we lost millions of public money and we failed a development project which the area needed the most. And worrying in the sense that there is a serious shortcoming in the Engineering section of PWD, project management and handling the contractors.
Being an engineer with the knowledge of project management, I have some experience of projects, its phases and project management. It is worth mentioning that each phase of a project requires special set of expertise from FEED (Front End Engineering Design) to project planning and from execution to its monitoring and control.
Coming back to the topic, I want to highlight the possible causes of the failure of the bridge. These points need to be considered during the investigation of the failure as they are the design basis and ignoring any one can result in such fiascos.
1) Soil Bearing Load Calculations
This aspect is the starting point of any civil works. This calculation is derived from soil investigation report. All successive designs and calculations depend upon this report. This report should be reviewed and checked either the designing is based correctly on this report or not. The failure will repeat if the designing isn’t as per suggestion and requirements of the Soil Investigation Report.
2) Differential Settlement of the Column/Pillar/Piling
It is a phenomenon that occurs due to difference of load on two different structural components. This phenomenon can be seen in buildings. Cracks appear in walls due to this effect. The effects of differential settlements are catastrophic in case of bigger structures or load carrying structures like bridges. It is possible that the girders might have failed due to difference settlement of piling and resulting difference in height of the pillars.
3) Bar Arrangement, Concrete/Steel Ratio
This is one often under-estimated aspect during designing of any structure. It is a common misconception that by using higher diameter re-bars will strengthen the structure. The strength of a structure depends upon right Bar Arrangement and Concrete/Steel Ratio (It’s an analogy to using of braided steel rope for Hanging Bridges where small wires are meshed together resulting in high strength rope that holds all the load of bridge and the vehicles).
4) Poor Concrete
Poor concrete, as the name implies, needs no explanation. This is the meanest technique used by contractors to save money. All the engineering and management fails if the concrete is not prepared as per standards and recommendations of the engineering team. A structure may collapse due to its own weight if the concrete is made poor; bearing some load is a far cry. A simple Compression Test will reveal the concrete condition. This test can be carried out in Civil Department in UET Lahore and Taxila (there might be more agencies for such tests)
5) Column Bar Arrangement
Seemingly irrelevant but it may be the cause of failure. Buckling is a phenomenon in which the vertical structure bends and takes it position after shedding off its load. This occurs if the column is too slender. The column bar arrangement should be checked and reviewed.
Apart from these possible causes there might be more reasons for the failure. A qualified third party like NESPAK can easily find the causes of the failure. I have penned down these causes for the information of the common man and for the attention of the relevant secretary (Secretary Works possibly). I would also like to add the following two points;
1) Exclude the absurd reason of failure: the wind
Please for God sake don’t mock yourself by saying that the high winds tumbled the girders (I heard that someone in the department came up with this cause. I remembered the words of a genius in the department when he claimed that the cracks in the penstock of Naltar Hydropower Plant were caused by worms. A face-palm!! )
2) The investigation committee should not include the people from PWD/Contractors.
The investigation should be carried out by the Third Party. Both the PWD and the contractors are responsible for the delays and failure of the project. They can’t be unbiased. The report should be prepared in minimum allotted time(a month is more than enough).
I will suggest that the secretary works should hire the services of a qualified third party to investigate the causes of the failure. It should be remembered that the existing intact parts of the bridge should be evaluated and tested for conformance. The failure will continue if the cause lies in differential settlement of the existing columns of the bridge.
Furthermore one should know that the success lies in the matching your steps with the latest engineering and management practices. The staff in PWD and the contractors should take refresher courses to get updates about the recent practices and Standards in their relevant fields. It should be assured that the qualified personals are deployed on projects by the contractors for execution of the projects with quality and standard.
Note: I am highly thankful to Engr.Malik Shehzad for being a part of brainstorming session to figure out the possible causes of the failure.
Engr.Ghulam Haider, hailing from Hunza, an Engineer and project management professional. He can be reached at “firstname.lastname@example.org, 03425619008)