Failure Analysis at DMRC On July 12th 2009 a metro bridge that was under construction collapsed due to negligence by an office in-charge of the Badarpur Metro line. The failure of the bridge killed 6 and injured another 15 when the pier cap sheared from the connecting pillars. The Delhi Metro Rail Corporation took major heat from this incident because the roadway was a major milestone of providing a reliable and easy mean of transportation to the capitol of India.
The DMRC is considered the most reputed infrastructure organization of India and neglecting roadways to the point where they fail is not an option. During that day the pier cap collapsed causing the collapse of the launching girder, p between p-66 and p-67 piers which had already been erected and pre-stressed, and also segments of the superstructure for the p between p-67 and p-68. The pier cap (p-67) sheared from the connecting point of the pier and pier cap.
The top reinforcement of the cantilever beam did not have any development into the pier itself which caused the shear itself. The launching girder has failed due to the failure of the pier cap. This failure also caused the p between piers 67 and 68 causing it to be inclined supported by the ground on one end and the pier cap on the other. With the failure of the pier cap and p between piers the crane used for lifting the launching girder also failed on July 13th 2009.
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Bending of the crane shows the clear sign of overloading which was caused by not analyzing the amount of stress the crane could handle. The causes of the failure are many and once one portion of the roadway failed it caused a chain reaction to the entire infrastructure collapsing. The pier (p-67) was initially designed as a leg of a portal frame between piers but then was changed to support the pier cap. The same method was used for piers p-66 and p-68.
The top reinforcement was poorly engineered; the pier cap had a reinforcement of 36mm diameter and a length of 500mm which was an insufficient bond length for the structure. During the launching operation the launching girder itself developed a crack that was grouted in crack areas and further strengthened by introducing prop or jacketing. During the launching of superstructure 6 segments where lifted and the whole system collapsed when the seventh segment was hooked up for lifting.
It was concluded that the failure of the pier cap occurred to the improper jacketing done when a crack had occurred. This was also coupled with inadequate length of support and reinforcement of the cantilever pier cap. The failure of the cranes was the fact that the capacity of 2 cranes where not able to hold the weight of the superstructure which caused the larger 3rd crane to fail. The Delhi Metro Rail Corporation sacked the official in charge of the Badarpur Metro line, Vijay Anand for neglecting his duty.
Structural designs should have been proof checked by an experienced structural engineer. Also once failure had been observed the structure should have been abandoned and a new structure should have been built. Make shift reinforcement to save a failed structure was a major neglecting issue and engineering failure. The lack of professionalism that lead to the superstructure failure started with trying to fix the failed pier cap and neglecting the fact that the cranes used to lift the structure where not engineered to hold the amount of weight that needed to be supported.
The support reinforcement should have been checked by an experienced engineer that should have easily seen the reinforcement issue between the pier and pier cap. The information for this case study was found from www. engineeringcivil. com/theory/civil. engineering-disaster. com and www. thaindian. com. The entire structural failure was found on these sites including who was a fault and why the structure failed.
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