Search

Mexico highway network has more than 14,000 bridges. Most of them are reinforced concrete (RC) structures. The bridges design process incorporates the use of an overstrength factor that is not justified and has received little attention in published works. Mexican regulations allow using an overstrength factor for buildings in the range of 2?3, to reduce the design spectra as a function of the selected seismic behavior factor. However, for bridges, a single factor of 1.5 is proposed independent of any design parameter. The bridges in Mexico are mostly simply supported structures with maximum span lengths of 50 m. A relevant and distinctive aspect of the bridges designed in Mexico is the large load amplitudes of the trucks used to define the live load and the high seismic activity in the country. This study determines overstrength factors of a family of medium-length RC bridges composed of simply supported superstructures and substructure made up of single and multi-column RC piers. Non-linear dynamic analyzes using a set of 80 accelerograms were carried out. The results show that the height of the bridges and their seismic location are relevant parameters in the overstrength of the structures. Finally, analytical expressions are proposed to assess the overstrength factors of a very common bridge typology in Mexico and the world. 6612-034D-AE05 | PEDRO DA SILVA DELGADO N/A

Beam-to-column connections are a crucial element in industrial precast reinforced concrete (PRC) buildings. They are also the source of several damages reported after recent earthquakes. This typology of buildings is very common both in the Portuguese industrial park and throughout Europe. In order to have a better knowledge of the connection behaviour an extensive experimental work was done and it is here presented to characterize, under cyclic loading, the pure friction behaviour and friction and dowel beam–to–column behaviour. The research was focused on the parameters that might influence the seismic performance of the connections. These are the friction between elements, the absence or presence of dowels and their position on the column's corbel, and finally the different axial load level applied on the connections. The results presented in this study pointed to the importance of using neoprene pad between concrete faces, with the main objective of damage control. The use of mechanical connectors (dowels) was also highlighted as a source of increasing the strength of the beam–to–column connection in values greater than 50%. published

Temporary ambient vibration monitoring of the suspended roof of the new Braga Sports Stadium was developed with the purpose of identifying modal properties through operational modal analysis. This experimental work allowed the validation of a numerical modeling that takes into account the geometric nonlinear structural behavior and the progressive application of loads during the construction phase. Special attention was given for the identification of modal damping ratios, owing to the necessity of analyzing the susceptibility of the suspended roof to buffeting effects. Modal damping ratios were estimated from data provided by free, forced, and ambient vibration tests, using an improved implementation of the enhanced frequency domain method and the covariance-driven stochastic subspace identification (SSI-COV) method. Keywords: suspended roof; ambient vibration test; free vibration tests; output-only modal identification; geometric nonlinearities; finite element correlation

The Vasco da Gama Bridge is a 17-km crossing over the river Tagus in Lisbon that was constructed and opened to traffic on the occasion of the World Exhibition Expo'98. As part of the dynamic tests required at the commissioning stage, ambient and free vibration tests were developed on the five viaducts and on the main cable-stayed part that form the bridge, with the purpose of assessing the most relevant dynamic parameters in order to validate design studies and verify the safety condition of the structure. Focusing on the main cable-stayed bridge, the efficient strategy followed in order to form an extensive and high-quality database and the different techniques successively employed to identify modal properties are described, showing the potential of operational modal analysis in the assessment of the dynamic behavior of a complex structure and the usefulness of free vibration tests in the accurate identification of modal damping ratios. The full characterization of the dynamic behavior of the bridge provides the definition of the so-called zero-state condition of the bridge and has been used as reference in the subsequent surveillance and monitoring of the bridge that has been implemented by Lusoponte, the consortium that owns the concession of the bridge. Keywords: ambient vibration; free vibration; cable-stayed bridges; operational modal analysis; wireless measurements