Tomas Echaveguren

Proposal of an Integrated Index for Prioritization of Bridge Maintenance

The bridge rating used in bridge management systems commonly uses only a structural condition. Factors such as seismic risk, hydraulic vulnerability, and strategic importance are commonly used in an isolated fashion. However, these factors are relevant when there is no possibility to calibrate deterioration models. This research uses the needs-based framework for developing an integrated bridge index (IBI) as an aid for prioritization and decisions made on maintenance and rehabilitation of bridges. The index weighs the structure distresses, hydraulic vulnerability, seismic risk, and strategic importance of the bridge. The index was calibrated using visual inspection, survey to experts, and regression analysis. After, the index was applied on six bridges placed on a primary road of Chile. To organize visual inspection, bridge inventory, and compute IBI and rank bridges, a software was developed. The calibration of the IBI index shows a correlation of 98% and all the parameters obtained were significant. Further research is needed to integrate cost with the proposed index and allocate maintenance activities.

Friction Reliability Criteria Applied to Horizontal Curve Design of Low-Volume Roads

Design of road horizontal curves usually considers geometric characteristics and surface pavement condition by means of friction, superelevation, and speed equations in a deterministic point of view: a unique radius and superelevation are selected, considering a uniform behavior of drivers and pavement surface condition. However, empirical evidence shows that operating speed usually exceeds design speed when design speed is lower than 100 km/h. This means that the aggregated friction demand exceeds the design friction. The friction threshold and variability are not considered in design at the present time. Therefore, the designer does not know the remaining friction available and cannot estimate the margin of safety provided by the design. This problem is important in low-volume roads (LVRs) because the design speed usually considered is lower than 100 km/h. In this paper a methodology to design horizontal curves for LVRs is proposed, considering the variability of skid resistance, pavement texture, driver behavior, and geometric design elements. Critical speed is obtained for two conditions: consistency between design and operational conditions and consistency between friction thresholds considered for the pavement surface and operational condition. For this purpose, a reliability index is estimated by using the Hasofer–Lind method. Results show that a more realistic design is obtained when an aggregated friction demand based on driver behavior is considered. A good design is obtained when design speed ranges around 60 km/h and the standard deviation of curve radius is lower than 20% of the mean radius.

Long-term behaviour model of skid resistance for asphalt roadway surfaces

Skid resistance (SR) is relevant to road safety. Several researchers have showed that SR diminishes its value over time depending on the traffic-aggregated interactions, and the presence of heavy vehicles in the traffic stream. The classical SR model shows that its value drops from a starting value to an equilibrium value over time. However, this behaviour in low-volume roads is not entirely true. In this paper, an SR model in a single mathematic specification is proposed, which considers the polishing effect of heavy traffic through the polishing equivalence factor. The model was calibrated by using data measured with a SCRIM device from 1100 test sections in Chile. Considering speed and temperature factors calibrated for Chile, data were processed and corrected. It was concluded that the model for long-term behaviour of SR is satisfactory, but it is necessary to include the seasonal effects for a more realistic model.