Cost of concrete flyover just half that of steel bridge, says expert

IRC tech panel member says alternative takes less space, time too

The Basaveshwara Circle-Hebbal steel flyover can actually be built using concrete at a cost of Rs 957 crore, almost half the amount quoted by the project contractor.

This is the finding of an Indian Roads Congress (IRC) technical committee member, who based his calculations on the detailed project report (DPR) uploaded on the website by the Bangalore Development Authority.

The structural analysis, which questioned the hefty Rs 1,791-crore price tag for the initial 6.7-km structure, also found the proposed project time span of 549 days too long. The entire work, the member concluded, can be completed in less than 300 days.

Here’s how the cost was worked out if the flyover were to be made of concrete.

The six-lane, 24.2-metre-wide and 6,687-metre-long main structure will cover a total area of 1,61,825.4 sq metres. Add another 41,973 sq metres of ramp area and the total plan area will be 2,03,798.4 sq metres. The flyover cost at Rs 35,000 per sq metre of plan area will work out to Rs 713.30 crore. The addition of underpasses as mentioned in the DPR takes the total cost to Rs 956.44 crore.

Excess pillars

The analysis found another glaring factor driving up the cost of the steel structure. The number of pillars are 40% in excess of the requirement. The DPR estimates that a pillar is required for every 25-metre span of the steel flyover. So, for the 11,625 metres of the flyover and ramps, 466 pillars will have to be erected.

However, the IRC expert, R K Jaigopal, contends that the number of pillars can be reduced to 333 if 35-metre spans are considered. In effect, the project plan has 133 pillars in excess, due to which the cost for pile foundations has also gone up.

“Spans of 20-metre/25-metre cannot be called optimal. The agency should have worked out optimum spans which can be about 35-metre. This way, the number of piers (pillars) can be reduced and environmental damage due to more digging for piles minimised,” he says.

Questioning the rationale that steel piers require less space than concrete, the expert reasons, “More than four to five times of pier area is required for piling and pile cap, which needs to be barricaded. Then, where is the area saving by steel?”

The contention that steel pillars require less time to erect is also challenged. “Nowadays, an entire concrete pier is cast in one pour within a few hours. Then, why spend more money on steel? All these details should have been compared and discussed in the DPR.”
The DPR shows that eight steel girders for the main span and three girders for the ramps will be manufactured in the workshops.

“Suppose all the girders are converted to concrete, the same can be manufactured in the casting yard. It will then make no difference and the cost can be reduced to half,” explains the expert.

‘Steel bridge toll Rs 150’

BJP leader and former deputy chief minister R Ashoka on Thursday said the state was planning to impose a minimum toll of Rs 150 per trip for using the steel flyover proposed between Basaveshwara Circle and Hebbal.

He was speaking on the sidelines of a BJP event in Bengaluru. Ashoka, however, did not reveal the source of his information but stated it was authentic.