Construction and dynamic identification of aeroelastic test models for flexible roofs

Abstract

The aeroelastic wind tunnel testing of flexible roofs made of hyperbolic paraboloid cable nets is a challenging task for designers and researchers, with very limited documented experiences in the literature. The reduced-scale model construction and its dynamic identification are the main issues to address when approaching this problem, mainly because of (i) the very small mass of the roof, (ii) the strict aeroelastic criteria to satisfy and (iii) a large number of very closely spaced significant natural frequencies. To suggest an approach to follow to investigate the wind—structure interaction for this structural typology, this paper discusses the aeroelastic scaling, the aeroelastic model construction, the dynamic modal identification and the FEM predictive numerical modelling of hyperbolic paraboloid roofs (HPRs) with square, rectangular and circular plan shapes and two different curvatures. Modal identification is especially challenging due to the presence of several closely spaced modes and it is here tackled by different methods such as Welch’s method, random decrement technique (RDT), Empirical mode decomposition with a time-varying filter (TVF-EMD) and frequency domain decomposition method (FDD). The satisfying accuracy of the aeroelastic scaling has been verified by comparing the wind-induced vertical displacements of the prototypes against those of the experimental models. Furthermore, an extensive qualitative investigation of the natural mode shapes has been carried out revealing that test models reproduce most of the prototype modes.

Non-Linear Behaviour and Analysis of Innovative Suspension Steel Roof Structures

“…It should be noted that the cylindrical surface of such suspension structures complicates their construction, operation, and maintenance, especially under wind loads [23][24][25]. Dynamic loads also have a great influence on the behaviour of suspended structures [26,27]. Spiral wire cables are vulnerable to corrosion [28,29].…”

Statistics of wind-induced vibrations for a flexible roof

“…A cable net and membrane tensile structure is a large span roof with a hyperbolic paraboloid (HP) shape, which is characterized by small permanent loads and a complex structural dynamic as they are very flexible and sensitive to the wind load. In addition, they tend to have very low natural frequencies, often very close to each other [1][2]. For this reason, wind-induced roof excitation should be investigated carefully during the design phase [3][4][5].…”

“…Each structural type behaves differently, so this aspect, added to a general lack of information, has led to many studies on this topic. It is possible to group the tensile structural types into five different categories [2]: Domes; Canopies and open roofs [4,5]; Air-supported structures; Cantilevered; Hyperbolic-paraboloid, cable-net/membrane roofs [1][2][3][4][5][6]. One of the most common design practices relies on applying the wind load as a static nodal force estimated by pressure coefficients (i.e., mean or peak) given by a code [7,8] or by parametric pressure coefficients maps obtained through wind tunnel (WT) tests [6] by performing static analyses.…”

“…One of the most challenging aspects is the scaling of masses and stiffness because the prototype mass is minimal, and the stiffness is relatively large. Another important aspect is the role of the membrane, which is still firmly neglected in structural analyses; however, it affects the roof stiffness and structural damping [1,2]. Finally, the dynamic identification of the model is complicated because these structures have several close natural frequencies [1,2].…”

“…Another important aspect is the role of the membrane, which is still firmly neglected in structural analyses; however, it affects the roof stiffness and structural damping [1,2]. Finally, the dynamic identification of the model is complicated because these structures have several close natural frequencies [1,2]. Therefore, a correct model identification is essential to calculate the WT velocity scale, which significantly affects the results.…”