ponte serravalleEdit profile
Introduction to the Serravalle footbridge. Both technology and aesthetics are the central themes of this project: the new aesthetic shape characterizes the structure empathizing its slenderness while the new technical device designed to fit the dynamic performance of the footbridge (Tuned Mass Damper) addresses the wellness of people crossing over the structure. Safety is another key feature: in fact the project was born by the Republic of San Marino increasing concerns over young and old people crossing the motorway which the footbridge now steps over. The Republic of San Marino run an international competition for the footbridge design. The requirement was a new structure that would connect the main square of Serravalle with a bus stop, frequently used by old people, and with the sports centre, mainly attended by young people. The Authors at first were frequently on site to see how people reacted to the presence of the loud motorway, and also to future possibility of crossing the road in an easy and safe way. It was clear for us that the bridge should have been comfortable to walk through but we also wanted to create a fascinating structure, both during the day and the nigh-time. We achieve the desire effect as follows. During the day, the footbridge forecasts the beautiful green landscape, visible through the glazing facade erected on the south side of the bridge. The glass protects the crossing people from the wind and at the same time let them see through due to its transparency. On the other side of the deck a smoothed semi-transparent wall made up of hole fitted grey plates provides safety and helps the passers-by in crossing quietly over the loud street at over six meter high. During the night-time small lights marks the steps along the deck and some others switch on to indicate the existence of the handrail. No lights coming from the top are installed along the footbridge. Finally the choice of friendly materials, like concrete for pillars, steel for the main trusses, glass for the vertical façade and wood for the deck walkway are strictly conceived to make a pleasant and comfortable walk in the best safely and highest aesthetic manner. Main remarks on the Serravalle footbridge. This footbridge was conceived to respond to an international competition won by the Authors in 2006. The structures is forty meters long; the bridge was erected six meters above the main road linking the Republic of San Marino to the town of Rimini and the Adriatic sea. Three are the main peculiarities of this footbridge; namely, (a) its shape and special static behaviour, (b) the presence of an innovative material “Sentry Glas®Plus “interlayer (by DuPont) used to create a stronger glass balustrade against wind storms, and finally (c) a Tuned Mass Damper (TMD) put in the midspan to prevent excessive displacement and accelerations that would affect the people crossing over. Concerning the first feature, the shape: it was achieved by the aid of only two arched steel pipes bowed on to different planes, (vertical the first and sloped the second one), to create a curved trussed beam which alone sustains the cantilevered walkway, giving the footbridge a surprising aesthetic view. The second feature of the bridge has to do with material employed in the laminated glass which is also widely used for -hurricane resistant windows. We selected the SentryGlas®Plus interlayer to be able to achieve the maximum transparency at the highest safety for the glass balustrade. Finally the last feature, the Tuned Mass Damper was investigated since the early design steps to give the footbridge the sufficient comfort against the oscillations due to its intrinsic flexibility. The right position compatible with the aesthetic demands was chosen for the strong reduction of the footbridge oscillations by tuning the values of mass, springs and dashpot of the TMD device. The design was approached in a multidisciplinary way, and always taking into account the aesthetics, safety, comfort and economy. Materials’ choice, details’ design and construction needs were addressed trying to minimize the difficulties and potential derailers . Much effort was taken on limiting the time for launching the footbridge. The whole structure was erected in only one night using two cranes and closing the motorway to the traffic. A test was performed just after the footbridge erection: the structure was filled with water to reach 400KN and hence simulating the design live load over the footbridge. The client was really impressed with the results for both technical and esthetical reasons. Moreover the test data were satisfactory and matched very well with the design’s ones.