Abstract

This work aims to perform a comparative analysis between the Hec-RAS and IBER models, in the hydraulic evaluation of rivers with structures such as bridges. The case of application was the La Guardia creek, located in the road that communicates the cities of Barquisimeto-Quíbor, Venezuela. The first phase of the study consisted in the comparison of the models from the conceptual point of view and the management of both. The second phase focused on the case study, and the comparison of the results obtained from the hydraulic analysis. It was observed that the behavior in both models presented great similarity in the flow profile as in the regime. Upstream of the two bridges predominate the subcritical regime, where the highest depths and the lowest velocities are present. The opposite occurs downstream of the two bridges, where the supercritical regime prevails, high speeds and minimum depths. It is concluded that, for rivers with simple geometry and preferably with a single bridge, the Hec-RAS one-dimensional software is presented as the best alternative of use due to the ease of data entry, providing reliable results in a shorter time. While the IBER package is two-dimensional, it represents a better option for modeling rivers with more irregular geometries, when there is a special interest in the hydraulic behavior of the flow through stirrups and stacks, and having two or more bridges with separation reduced.

Abstract

Composite structures have not been able to compete in Spain with more conventional prestressed concrete bridges in the lower range of medium spans (30 - 90 m.). In this context, twin-girder sections are revealed as a more competent typology because of its sobriety, ease of construction and good structural performance.

At present the optimal character of the designs in structural projects is rarely challenged. The present study undertakes an in-depth analysis of the twin-girder section, involving a complete optimisation for the deck. To this end a specific 2D grillage model has been developed, integrating the composite and evolutive character of twin-girder decks, as well as the instability phenomena inherent to thin-walled structures.

Several conclusions are drawn after a parametric calculation using this model, regarding the optimum dimensions of all the variables that define the twin-girder section. These conclusions crystallise in a series of formulas that can be used as a design guide. 

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The Hillman-Composite Beam (HCB®), is an innovative structural member for use in highway and railroad bridges as well as marine facilities. The HCB is essentially a lightweight reinforced concrete beam strengthened and protected by a corrosion-resistant and resilient Fiberglass Reinforced Polymer (FRP) shell. The beam is comprised of three main components, a concrete arch (compression reinforcement), an FRP bottom flange encapsulating steel strands tying the ends of the arch together (tension reinforcement) and the FRP shell. Galvanized Rebar “shear connectors” are used to make the beam composite with the concrete deck in the same manner as pre-stressed concrete beams. The HCB has been deployed throughout North America and is currently being sought out by transportation agencies worldwide: projects using the HCB over the last 10 years, several State DOTs, Class 1 Railroads, the US Army Corps of Engineers among others have successfully completed projects using HCB. In all cases, the owner received a low-maintenance, high performance beam with a minimum 100-year service life.

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The evolution of the state of a structure is characterized by deterioration. This is mainly due to corrosion of the steel reinforcement and damage from mechanical solicitations. The maintenance of existing infrastructures involves a good grasp of their condition and a high level of expertise on the part of the project managers. An accurate assessment of the bridge state condition is required to plan maintenance and repair activities for better durability, and to maintain the level of service of the road network. In this paper, an effective management framework for bridge is proposed using field observations from visual inspections. Each element of the bridge was evaluated separately by a visual inspection from which were derived ratings to quantify the structural performance and the material condition. The element ratings were also combined to obtain an overall rating for the bridge considering its defects and impact on the behavior of the complete structure. The modelling approach proposed in this work can better represent the deterioration of concrete-built bridges when the defect is visible. A representative structure in Quebec was studied to illustrate how to apply the methodology for the assessment of a real structure condition at specific times.