NEW DELHI: Delhi Metro Rail Corporation ( DMRC ) is running behind schedule on the much-delayed Phase-IV project and, to save time in construction, it is now going to extensively use a technology that has only been used on a few occasions previously.Over the years, DMRC has used different types of precast structures, such as box girders, I-girders and U-girders, to construct its corridors. For the Phase-IV project, however, DMRC has decided to standardise the usage of U-girders for the entire 104km network on the six proposed corridors to save time as well as lower construction cost. The U-girders will also have built-in sound barriers, apart from built-in cable support.Compared to other types of girders, the much longer U-girders drastically reduce construction time. However, due to their length, they require absolute precision during construction. Also, their length makes transporting them from the casting yard to the site a tricky proposition.While the conventional box girders and I-girders are 2.2m to 2.5m long, the length of U-girders varies between 22 and 27 metres. The longer length means a span between two pillars can be constructed overnight compared to 5-6 days in case of conventional girders. DMRC has used these girders in Airport Express Line, the Badarpur to Faridabad section of Violet Line and a section in Noida.“We have decided to standardise the design and drawings of pre-tensioned U-girders and precast pier cap for Phase-IV project. Standardisation will mean that time and cost are reduced in redesigning, re-checking and employing different construction schemes. It will also help in ensuring that no human error creeps in while preparing a new set of drawings by various consultants,” said a DMRC official.Standardisation would also ensure that designs are available before the commencement of construction, thus reducing delays and helping in better management of the worksite. “If the drawings are provided at the tender stage, the contractor can precisely calculate the cost of construction, which will ensure there are no future variation claims,” said the official.DMRC will be engaging a detailed design consultant for the standardisation of the structures. “The consultant will have to make rigorous permutation and combinations, taking into consideration various span lengths and curvature,” the official said.