PSI - Issue 5

C.A. Prato et al. / Procedia Structural Integrity 5 (2017) 332–339 C.A. Prato/ Structural Integrity Procedia 00 (2017) 000 – 000

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Fig. 10. Fourier amplitude spectra of measured accelerations

5. Conclusions

The foregoing study conducted for the purpose of estimating the accelerations induced by road traffic for a new stayed highway bridge in the process of design lead to the following conclusions:  The damping rate measured on an existing stayed bridge with similar structural configuration confirms the IAP 11-prescribed value of 1% for design calculations aimed at determining the maximum accelerations of a pre stressed concrete bridge deck.  Dynamic testing and numerical modeling of the existing bridge allowed a direct comparison between the natural frequencies obtained from simple dynamic tests and those computed by a suitable numerical model. General good agreement between experimental and numerically calculated frequencies was obtained first hand without need of adjustment of inertia or stiffness data.  Measured accelerations at mid-span turned out approximately twice those obtained from calculations based on the numerical model subject to a moving force at constant velocity over the bridge. Since the numerical model reproduced the measured natural frequencies, the source of discrepancy is partially attributed to the simplifications of the IAP-11-prescribed loading condition for predicting deck accelerations, where the passing truck is modeled as a moving load without associated mass and neglecting dynamic interaction with the bridge. Another possible contribution to the discrepancy is associated with the details of the erection procedure. It should also be recognized, however, that the IAP-11 specifications clearly limits the applicability of such simplified analysis procedure to estimate accelerations at design stage to standard structural configurations with main spans less than 50 m, which is not the case of the bridge under design that motivated the present study.

Acknowledgements

The present work was partially supported by the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and the Secretaría de Ciencia y Tecnología, Universidad Nacional de Córdoba, Argentina.

References

1. IAP-11 Spanish Design Code, 2011, Instrucción sobre las acciones a considerar en el proyecto de puentes de carretera, Madrid, España.

2. SAP2000 Advanced 14.1.0, 2009, Structural Analysis Program: “Analysis for Moving Load”, Computers and Structures Inc.