Chacao Live Load Study


ROD-IS has recently performed a traffic loading assessment for the Chacao Bridge in Chile, a two-span suspension bridge which will be comprised of two main spans of about 1100 m and will connect the island of Chiloé with mainland Chile. Construction is expected to begin in 2015 with a planned opening date in 2019.

The bridge is being designed to the AASHTO HL-93 live load model which is used for bridge design in the USA. ROD-IS were commissioned to assesses whether the traffic data from Chile be used to evaluate if the US HL-93 load model is appropriate for modelling Chilean traffic loading. Weight data, available for 25,076 trucks, which was statically weighed near the site by the Chilean Road Department, was used as the basis for modelling traffic loading on the bridge. As congested traffic is critical for long span bridges, different traffic mixes of cars and trucks were modelled on the bridge in fully jammed conditions. The calculated loading was then compared with that of the HL-93 load model and the critical traffic mix was identified. A deterministic modelling approach was subsequently used, assuming different mixes of cars and trucks and the resulting loading compared with that of the HL-93 load model.