Bruno J.A. Costa

Testing and monitoring of a centenary arch bridge

The present article summarizes relevant aspects concerning the monitoring system adopted during a load test carried out on the Luiz I steel bridge in the city of Porto, Portugal. The instrumentation is described and some results obtained from the load test and from a short observation period before and after the test are presented. Additionally, the performance of fibre optic Bragg grating sensors is appraised in measuring field strains and temperatures. The results are compared with those given by using a bridge numerical model, in which some integrity parameters are to be assessed by the monitoring data.

Modal analysis for the rehabilitation assessment of the Luiz I Bridge

Dynamic testing in the condition assessment of existing bridges to support their rehabilitation and strengthening designs is becoming a common procedure, yet additional dynamic testing after rehabilitation is rare. Nevertheless, combining the results of dynamic testing before and after bridge rehabilitation produces unique and valuable information regarding changes occurred in a bridge’s dynamic properties. Such dual testing would allow researchers to verify the behavior predicted at the design stage and to assess the stiffness variation, which would eliminate the need for mandatory field static testing. This article reports the modal analysis of a unique centenary steel-arch bridge that was recently rehabilitated and strengthened. The ambient vibration test conducted after the construction works is described, and the data are compared with those collected before the rehabilitation. Structural identification is completed by means of experimentally validated three-dimensional (3D) finite-element (FE) models simulating both phases. The results bring to light important findings concerning variation in bridge stiffness, changes in the modal parameters, and the impact of support conditions and structure of decks in bridge dynamic properties.

Assessment of traffic load events and structural effects on road bridges based on strain measurements

AbstractSeveral technical and scientific publications have been made available focussing on Bridge Weight-in-Motion (BWIM) concerning railway bridges. On the contrary, BWIM analysis on road bridges are more scarce and therefore, this work intends to provide a contribution by presenting the BWIM analysis performed on two major road bridges in Portugal – Leziria Bridge and Pinhao Bridge. These bridges are equipped with electric and optical strain gauges, acquisition systems with features that allow high sampling rates. Based on the collected data and focussing on the bridges’ lifetime, a probabilistic approach to quantify extreme traffic loads was implemented using extreme distribution functions. The bridges’ behaviour to these extreme traffic loads is numerically evaluated and a comparison with the alarm levels established by the bridge designers is performed. Although the bridges safety is not compromised, it was concluded that the representativeness of the observation period is a critical issue and the ...

Experimental Validation of the Finite Element Modelling of Pinhão Bridge

The Pinhao Bridge is a Portuguese metallic roadway bridge constructed in 1906 over the Douro river, whose state of degradation requires the development of rehabilitation works (Figure 1). In this context, an ambient vibration test of the bridge was recently performed. The collected data was processed using the Peak-Picking method that allowed the identification of the most relevant natural frequencies (Figure 2) and mode shapes. The experimental identified modal parameters were used to improve the numerical model developed by the consultancy office responsible for the rehabilitation design. The updated finite element model provides very well correlated natural frequencies and vibration modes with regard to the corresponding experimental estimates (Figure 3). Open image in new window Figure 1 View of Pinhao Bridge Open image in new window Figure 2 Average normalized power spectra used in the identification of the natural frequencies associated with the vertical bending modes of the 2nd span. Open image in new window Figure 3 Experimental vs numerical vertical bending mode shapes (lateral view of the bridge)