Catarina Fernandes

Weldable fibre Bragg grating sensors for steel bridge monitoring

For applications related to the structural health monitoring of steel bridges, novel weldable strain and temperature sensors based on fibre Bragg gratings were developed. These sensors, which can be directly welded to metallic structures, reveal linear responses over typical required measurement ranges and stability over thousands of load and temperature cycles. Proper installation procedures and in-field mechanical protection were also developed and implemented. The significance of the developed sensors was demonstrated through the installation of a complete sensing network on a new circular pedestrian bridge in Aveiro, Portugal, where it was used for loading tests, and also for in-service monitoring of its structural health.

Cyclic Behavior of Substandard Reinforced Concrete Beam-Column Joints with Plain Bars

ACI Structural Journal, V. 110, No. 1, January-February 2013. MS No. S-2011-088.R1 received April 13, 2011, and reviewed under Institute publication policies. Copyright

Comparative structural response of two steel bridges constructed 100 years apart

This paper presents a comparative numerical analysis of the structural behaviour and seismic performance of two existing steel bridges, the Infiernillo II Bridge and the Pinhão Bridge, one located in Mexico and the other in Portugal. The two bridges have similar general geometrical characteristics, but were constructed 100 years apart. Three-dimensional structural models of both bridges are developed and analysed for various load cases and several seismic conditions. The results of the comparative analysis between the two bridges are presented in terms of natural frequencies and corresponding vibration modes, maximum stresses in the structural elements and maximum displacements. The study is aimed at determining the influence of a 1 century period in material properties, transverse sections and expected behaviour of two quite similar bridges. In addition, the influence of the bearing conditions in the global response of the Pinhão Bridge was evaluated.

Comparative analysis of the cyclic behaviour of beam-column joints with plain and deformed reinforcing bars

Damage reports after recent earthquakes proves that slippage between steel reinforcing bars and the surrounding concrete is one the common causes of damage and collapse of existing RC building structures. The bond-slip mechanism assumes particular importance in RC building structures built until the 70’s, with plain reinforcing bars, previously to the enforcement of modern seismic codes. This type of structures is usually characterized by poor reinforcement detailing, poor bond properties and inadequate concrete confinement. In RC buildings subjected to cyclic loads, as the induced by earthquakes, high stress concentration occurs at the beam-column joints, making this regions prone to the occurrence of severe damage. Beam-column joints are particularly sensitive to the bond-slip mechanism due to the stress concentration, but also due to the fact that anchorage of beam and column longitudinal reinforcing bars is typically made in the joint vicinity. In this paper are presented the main results of the cyclic tests performed on two full-scale beam-column joints with the same geometry and reinforcement detailing, representative of interior joints in RC building structures built until the mid-70’s, without adequate seismic detailing. One specimen was built with plain reinforcing bars (poor bond properties) and the other with deformed bars (good bond properties). For a better comprehension of the bond properties influence on the cyclic behavior of the beam-column joints, a comparison is established between the main experimental results obtained for the two specimens. The comparative analysis shows that the bond-slip mechanism has a strong influence in the cyclic response of RC structural elements.