The purpose of this research is to evaluate aerodynamic loads on large span hyperbolic paraboloid shaped roofs. This geometrical shape is specific to the design of tension roofs with a cable structure. In this case, however, the roof structure is a rigid body which enables us to evaluate the pressure coefficients for this particular geometrical shape. In the future, attention will also be paid to analysing the pressure coefficients variation that occurs with structural deformation. The parabolic shape selected is often used to build tension structures. These kinds of structures are light and characterized by innovative construction materials and technical elements such as air conditioning, lighting, etc. The design of tension roofs is always striving towards technological and structural innovation in order to build ever lighter structures to cover equally ever larger spans. Tension structures are in line with the new contemporary architectural concept of space, allowing for the construction of large open spaces where the flexibility and the modifiability of the structures in question are the most important prerequisites. They also meet the demand for structures that only need basic planned maintenance and can also withstand seismic pressure too. In Italy, this constructive typology has so far been largely neglected and to a certain extent even ignored by building regulations. In fact no mandatory standards have been set for the design and construction of these structures, except for temporary constructions. There is also a lack of information about wind action on hyperbolic paraboloid shapes. While there are precise indications for shells, slopes and domes, there are currently no wind regulations for this shape in Italy. No prescriptions are provided in the new CNR-2008 for the calculation of wind action, either. This research followed three consecutive steps: the first one was aimed at developing an optimized procedure of preliminary design for the cable structure; the second one focussed on the study of the wind action on these structures. The third phase of this research is illustrated in “Aerodynamic behaviour of roofs with hyperbolic paraboloid shapes – part II: P.O.D. and C.F.D. analysis”. The procedure of preliminary design consists in evaluating prefixed cable spans and sags, the minimum values of pretensions and areas of the two series of cables (load bearing and stabilizing) so as to maintain the cable stress within the limit value under the two opposite load configurations: maximum snow load and maximum wind depression. By using the procedure for a set of values of spans and sags, a statistical sample of different roof shapes has been produced (Fig.1.a, b). Having in mind the design of sport arenas, swimming-pools and meeting rooms, we have taken into account another geometrical parameter (in the following Hb) measuring the distance between the roof and the ground floor. This parameter has been added to the span/sag ratio in the experimental tests in the wind tunnel. In fact, the model is built in two different heights. In the second phase of the research, experimental tests were performed in the CRIACIV wind tunnel, in Prato, in order to assess the wind action on tension roofs with a hyperbolic paraboloid shape.

Aerodynamic behaviour of hyperbolic paraboloid shaped roofs: wind tunnel tests

D'ASDIA, Piero;
2009-01-01

Abstract

The purpose of this research is to evaluate aerodynamic loads on large span hyperbolic paraboloid shaped roofs. This geometrical shape is specific to the design of tension roofs with a cable structure. In this case, however, the roof structure is a rigid body which enables us to evaluate the pressure coefficients for this particular geometrical shape. In the future, attention will also be paid to analysing the pressure coefficients variation that occurs with structural deformation. The parabolic shape selected is often used to build tension structures. These kinds of structures are light and characterized by innovative construction materials and technical elements such as air conditioning, lighting, etc. The design of tension roofs is always striving towards technological and structural innovation in order to build ever lighter structures to cover equally ever larger spans. Tension structures are in line with the new contemporary architectural concept of space, allowing for the construction of large open spaces where the flexibility and the modifiability of the structures in question are the most important prerequisites. They also meet the demand for structures that only need basic planned maintenance and can also withstand seismic pressure too. In Italy, this constructive typology has so far been largely neglected and to a certain extent even ignored by building regulations. In fact no mandatory standards have been set for the design and construction of these structures, except for temporary constructions. There is also a lack of information about wind action on hyperbolic paraboloid shapes. While there are precise indications for shells, slopes and domes, there are currently no wind regulations for this shape in Italy. No prescriptions are provided in the new CNR-2008 for the calculation of wind action, either. This research followed three consecutive steps: the first one was aimed at developing an optimized procedure of preliminary design for the cable structure; the second one focussed on the study of the wind action on these structures. The third phase of this research is illustrated in “Aerodynamic behaviour of roofs with hyperbolic paraboloid shapes – part II: P.O.D. and C.F.D. analysis”. The procedure of preliminary design consists in evaluating prefixed cable spans and sags, the minimum values of pretensions and areas of the two series of cables (load bearing and stabilizing) so as to maintain the cable stress within the limit value under the two opposite load configurations: maximum snow load and maximum wind depression. By using the procedure for a set of values of spans and sags, a statistical sample of different roof shapes has been produced (Fig.1.a, b). Having in mind the design of sport arenas, swimming-pools and meeting rooms, we have taken into account another geometrical parameter (in the following Hb) measuring the distance between the roof and the ground floor. This parameter has been added to the span/sag ratio in the experimental tests in the wind tunnel. In fact, the model is built in two different heights. In the second phase of the research, experimental tests were performed in the CRIACIV wind tunnel, in Prato, in order to assess the wind action on tension roofs with a hyperbolic paraboloid shape.
2009
9788864530383
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11564/130726
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