ABSTRACT
When designing high-speed railway bridges, the dynamic analysis of the solutions becomes an important topic that should be included in the design. With the advent of the High Speed 2 project in UK, the suitability of precast elements produced by Shay Murtagh was evaluated. Three types of precast solutions bridges were studied: two isostatic bridges with a span of 25 m, one with Artesa beam sections and other with W beam sections, and one hyperstatic bridge, with three spans (20 + 25 + 20) with a length of 65 m consisting of four W beam sections. The dynamic analyses were performed assuming a linear elastic response, and based on the moving load method with superposition of effects, which revealed efficiency and competitive calculations times. This method was implemented in Robot Structural Analysis (RSA) through a Time History analysis based on the modal superposition method. The dynamic analyses of the different solutions were performed for the HSLM-A Trains, for velocities between 140 km/h and 480 km/h, and considering damping values of 1.0% and 2.5%. The results showed that in isostatic bridges, higher values of vertical accelerations and displacements occurred, and the vertical acceleration limit state of 3.50 m/s2 was not accomplished. On the other hand, in case of hyperstatic bridges, the values of vertical displacements and accelerations are relatively low and always below the recommended thresholds. In relation to the remaining limit state checks (torsion, vertical and transversal deflection of the deck, support lifting and passenger comfort) all solutions verified the correspondent regulamentar limit values. It was also concluded that a significant decrease of the dynamic effects, about 40%, can be achieved with the increase of damping values, with a noticeable impact in resonance situations. Finally, it was shown that the hyperstatic bridge solution is viable for built in site, while the isostatic bridge solution will require an increase of the deck’s height.
