## 1 Introduction  
Resonance vibration of a structure occurs when frequencies of regularly shedding wake vortices coincide with one of its natural frequencies. Moreover, the resonance vibration locks the vortex shedding frequency to the vibrating frequency and persists in the wind speed range beyond the initial velocity, thus achieving vortex-induced vibration lock-in. The vortex-induced vibrations (VIV) may occur at relatively low wind velocities and would affect the safety and the comfortability of the structure. This is a serious problem for flexible structural components and for other offshore structures exposed to flowing fluids that have been investigated extensively [1; 2; 3]. The evaluation of VIV responses, especially the maximum amplitude prediction, is one of the most important aspects of the wind-resistant design of flexible structures. Various empirical methods have been proposed and investigated for the prediction of the maximum amplitude owing to VIV [4; 5]. Structural mass, damping, Strouhal number, and aerodynamic force coefficients are essential two-dimensional (2D) parameters and are used to predict the VIV amplitudes. Moreover,three-dimensional parameters (3D), such as the mode shape and spanwise correlation, are indispensable for maximum amplitude prediction of flexible structures [6; 7; 8]. Given that the effects of the complexities of the nonlinear fluid-structure interaction have been identified, wind tunnel tests are still the primary test type used for the evaluation of the susceptibilities of flexible structures owing to vortex-induced vibrations. Generally, a rigid section model with finite length is [PERSON] elastically in the cross-flow to consider the 2D effects on vibration amplitudes [9], while the evaluation of 3D effects on the VIV amplitudes has stimulated researcher interest. This is attributed to the fact that the effects of the modal shapes and the spanwise correlations have not been considered in the wind tunnel tests of section models [10; 11; 12; 13; 14]. [PERSON] and [PERSON] [15] illustrated that the VIV amplitude of the full-scale model of the Tokyo Bay Bridge was approximately 50% larger than that of its corresponding section model. [PERSON] et al. [16] showed that the measured amplitudes of VIV on the Second Severn Bridge were larger than the results from the section model tests and concluded that the modal shape correction factor can likely explain the differences. [PERSON] et al. [17] investigated the VIV amplitudes of the full-scale model of the Xihoumen suspension bridge, and these amplitudes were significantly larger than the results of the section model tests. [PERSON] et al. [18] employed both a wind tunnel test of the large-scale sectional model and computational fluid dynamics to investigate the aerodynamic appendices and the mechanism responsible for VIV suppression. [PERSON] et al. [19] and [PERSON] et al. [20] demonstrated that the maximum amplitudes of VIV from field measurements were larger than the wind tunnel test results measured at two damping levels in the case of the Great Belt Suspension Bridge. Moreover, measurements of some flexible aeroelastic models and their section models in well-controlled wind tunnel flow conditions showed the same trend [21; 22]. For the evaluation of three-dimensional effects on VIV maximum amplitude, most of the previous works used field measurements and scaled model wind tunnel tests results. However, field measurements cannot provide controllable flow conditions, while scaled model wind tunnel tests are affected by the Reynolds number, with the comparison accompanied by several uncontrollable parameters. This study aims to perform research based on the elimination of these disturbances. A 3D long prism with a length of 4.5 m and a cross-section of 50 mm \(\times\) 70 mm in fixed-fixed boundary conditions and its 1:1 2D section model with the same cross-sectional size are tested in the same wind tunnel.