EXPERIMENTAL STUDY ON IN-PLANE DYNAMIC STABILITY OF GFRP CIRCULAR ARCH UNDER A VERTICAL HARMONIC BASE EXCITATION
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摘要: 该文为探究铺层角度对基础竖向激励下GFRP圆弧拱平面内动力稳定性能的影响,开展了系统的实验研究。设计了6组不同铺层角度的圆弧拱试件,利用TIRA激振器模拟输出基础竖向周期激励,采用NDI三维动态采集仪采集圆弧拱的竖向动位移,根据测得拱的面内自由振动响应,分别通过快速傅里叶变换和自由衰减法获得拱的自振频率和阻尼比。通过扫频实测了GFRP拱的动力不稳定域边界,并与有限元计算结果进行对比,基本吻合。研究表明:当外部频率约为结构自身频率两倍时,结构会出现激烈的面内反对称振动现象,即为参数共振失稳;当激励加速度小于临界激发加速度时,拱处于定态振动;外激励大于临界激发加速度时,GFRP拱出现参数振动,并且随着加速度的增大,拱的振动愈发激烈;随着铺层角度的增大,拱的自振频率和临界激发加速度逐渐减小,阻尼比与不稳定域范围逐渐增大。Abstract: The purpose of this study is to investigate the dynamic stability of GFRP circular arches with different lay-up angles under vertical excitations. Thusly, a systematic experimental study is performed. Six groups of circular arches with different lamination are designed, the vertical periodic vibration of foundation was simulated by applying TIRA series vibrator. The vertical displacement of circular arch was collected by NDI 3D dynamic acquisition instrument. According to the displacement data, free vibration frequency and damping ratio of the arch are obtained by fast Fourier transform and free attenuation method. The boundary of dynamic instability region of GFRP arch was measured by frequency sweep. The experimental results were compared with the finite element results, and the results show that when the external load frequency is about 2 times of the natural frequency of the structure, the structure has an intense in-plane antisymmetric parametric resonance. When the excitation acceleration is less than the critical excitation acceleration, the structure will not be unstable. The greater is the acceleration of external excitation, the easier does the parameter resonance phenomenon occur. With the increase of the lamination angle, the structural frequency and critical excitation acceleration decreases, and the damping ratio and the range of instability region increase gradually.
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表 1 基本力学性能数据
Table 1. Basic mechanical property data
弹性模量E1/GPa 弹性模量E2/GPa 剪切模量G12/GPa 剪切模量G23/GPa 泊松比μ12 泊松比μ23 32.632 7.451 2.879 1.698 0.3 0.4 表 2 试件设计参数
Table 2. Design parameters of test piece
工况组 矢跨比 铺层数 跨径/
mm截面
高度/mm截面
宽度/mm铺层
设计1 1/7 6 800 0.9 20 [0] 6 2 1/7 6 800 0.9 20 [±15] 3 3 1/7 6 800 0.9 20 [±30] 3 4 1/7 6 800 0.9 20 [±45] 3 5 1/7 6 800 0.9 20 [±60] 3 6 1/7 6 800 0.9 20 [±75] 3 表 3 自振频率及模态测试结果
Table 3. Natural frequency and modal test results
分析方法 有限元法 OMA 分析 误差/(%) 自振频率 理论一阶振型 自振频率 实测一阶振型 [0]6 14.55 面内反对称 14.55 面内反对称 0.00 [±15]3 13.34 面内反对称 13.39 面内反对称 0.39 [±30]3 10.50 面内反对称 10.41 面内反对称 −0.89 [±45]3 7.83 面内反对称 7.41 面内反对称 −5.35 [±60]3 6.89 面内反对称 7.03 面内反对称 2.00 [±75]3 6.88 面内反对称 7.02 面内反对称 2.04 表 4 阻尼比测试结果
Table 4. Test results of damping ratio
分析方法 自由衰减法阻尼比/(%) OMA分析阻尼比/(%) 误差/(%) [0]6 0.3562 0.3621 1.63 [±15]3 0.4168 0.4223 1.30 [±30]3 0.5381 0.5584 3.64 [±45]3 0.7453 0.7572 1.57 [±60]3 0.7513 0.7674 2.09 [±75]3 0.9142 0.9379 2.53 表 5 有限元边界频率与实测边界频率对比
Table 5. Comparison with the measured critical frequency and finite element critical frequency
激振力大小/(%) 上边界 下边界 实验值/Hz 有限元值/Hz 误差/(%) 实验值/Hz 有限元值/Hz 误差/(%) 40 29.14 28.93 0.72 29.14 29.14 0.00 50 29.07 28.78 0.99 29.19 29.23 0.12 60 29.05 28.67 1.31 29.22 29.29 0.24 70 28.97 28.62 1.21 29.27 29.36 0.31 80 28.92 28.59 1.14 29.33 29.43 0.34 90 28.9 28.57 1.15 29.35 29.47 0.39 -
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