基于舒适度的钢桁架-混凝土组合楼板动力特性研究

大跨楼盖结构的振动舒适度问题在结构设计中不可忽视，钢桁架-混凝土组合楼板是大跨结构中常用的楼板形式。针对该类型楼板的振动舒适度问题，建立简化层合梁模型以及精细的层合板模型，分析结构动力特性的影响因素和影响机理，并建立某真实结构的参数化有限元模型，计算细部构件对楼板振动频率影响规律。研究表明：当混凝土板和钢桁架的弹性模量比、质量密度比满足一定条件时，存在“分界点”使得随着混凝土板厚增加，组合楼板基频先降低后增加。进行舒适度计算或减振设计时，应注意是否存在“分界点”以及“分界点”位置；增大混凝土板弹性模量或减小密度能提高楼板基频，但对基频改变不明显；工程上可通过适当提高下弦杆和腹杆截面惯性矩、提高桁架高度和减小楼板跨度等方法提高组合楼板频率。

Research on dynamic characteristics of steel truss-concrete composite floor based on serviceability

The vibration serviceability of large-span floor structures is an important issue that cannot be ignored during structural design. Steel truss-concrete composite floor are commonly used in the design of large-span structures. Aiming at the vibration serviceability of this type of floor, a simplified multi-layer beam model and a fine multi-layer board model were established to theoretically analyze the influencing factors and mechanism of structural dynamic characteristics. Further, parametric finite element model of a real structure was established to study the influence of detailed components on floor frequency. The research shows that when the elastic modulus ratio and density ratio of the concrete slab and the steel truss meet certain conditions, there is a ‘boundary point’ where the fundamental frequency of the composite floor decrease first and then increase as the thickness of the concrete slab increases. When carrying out serviceability calculation or vibration reduction design, attention should be paid to whether there is a ‘boundary point’ and where is the ‘boundary point’. Increasing the elastic modulus of concrete slabs or reducing the density can increase the fundamental frequency of the floor slab, but not significantly change the fundamental frequency. In engineering practice, the frequency of the composite floor can be increased by appropriately increasing the moment of inertia of the lower chord and web members and the height of the truss as well as reducing the span of the floor.