超高层建筑风重耦合效应及等效静力风荷载研究

发布时间：2018-07-26 06:23

【摘要】：随着城市化进程的加快,越来越多的超高层建筑往轻柔方向发展,结构设计也出现许多急需解决的问题,风重耦合效应就是其中之一。风重耦合效应是指高柔结构在风荷载作用下产生的水平位移,重力的存在,使结构弯矩增大,从而进一步增大水平位移,这样的作用机理在静力方面表现为结构水平位移的增大,在动力上表现为结构固有频率的改变和和结构响应的变化。在实际工程中,超高层建筑的风重耦合效应已有报道,进一步细化分析风重耦合效应的影响显得十分必要。本文主要目的是为了分析风重耦合效应的影响因素,发现高柔结构由于重力影响在风振中的特性改变,同时给出一般超高层结构分析计算方法。总体而言主要做了以下几个方面的工作。利用悬臂梁模型,推导出计入结构大变形和重力的作用的风重耦合的动力方程,利用差分法可以求解风振时程响应,时程计算表明风重耦合效应使脉动风的幅值比传统计算的结果要大。结构顺风向随机风振计算可以按平均风荷载和脉动风荷载将方程分解成平均风方程和脉动风方程,其中平均风方程相当于静力非线性方程,求解容易；另一个脉动风方程是非线性动力方程,通过振型分解和等效线性化处理可以得到结构响应的解。参数分析表明,重刚比是影响风重耦合效应最重要的参数,其值越大,结构振动固有频率越小,结构响应越大。当结构重刚比较小时,地面粗糙度、结构固有阻尼和平均风速对风重耦合效应影响不大,但当重刚比较大时,风重耦合效应随着结构固有阻尼和平均风速的增大而减小。等效静力风荷载是工程设计中常用的方法。本文采用结构恢复力等价的原则,经推导可以得到沿高度分布的荷载。结果表明,计入风重耦合效应的等效风荷载表达式比常规高层建筑风荷载多了附加重力等效风荷载项。加入各分项的峰值系数可以得到设计等效静力风荷载。计入风重耦合效应后的顺风向风振系数与规范给出的风振系数存在着差异,风重耦合效应引起在建筑物中风振系数中下部分布值减小和上部分布值增大,结构的重刚比是影响风振系数的重要因素,其他因素影响不大。横风向风重耦合效应与顺风向类似,对横风向风重耦合效应来说重刚比仍旧是一个决定性因素,但横风向作用机理与顺风向不同,其风重耦合效应与顺风向存在一定的差异,特别是平均风速的影响有所不同,当平均风速较小时,结构响应随着重刚比增长而增长,当平均风速加大时,结构响应先是随着重刚比增长而增长,达到峰值后随着重刚比增长而下降。风重耦合效应使整条响应对重刚比曲线左偏。对于矩形截面的超高层结构,风重耦合与截面深宽比有关,当在深宽比小于2时,风重耦合效应先是减小再是增大,当深宽比大于2时,没有确切的规律。横风向静力等效荷载的变化规律和顺风向类似。对于一般超高层建筑的风重耦合的计算除了考虑顺风向和横风向的风荷载还必须考虑扭转向的风荷载。为了实现频域分析一般结构的方法,本文以每层的三个自由度为未知数建立计入风重耦合效应的有限元方程。分析表明,在质量偏心率较小情况下固有频率随着重刚比增大而减小,但当结构质量偏心率较大时,固有频率反而随着重刚比增大而增大,对于刚心偏位的情况也有类似结论。对于偏心结构,风重耦合效应使顺风向和横风向响应增大,但对于扭转向是减小的。不同角度对风重耦合的影响是发生周期性变化,偏心率较小时,偏心位置的角度对风重耦合效应影响不大,而随着偏心率的增大,角度影响就很明显。本文以LCVA作为实例分析调谐减振器在超高层建筑中减振规律。各参数分析表明质量比是减振中一个重要参数,质量比加大能明显起到减振作用,实际上只要水体质量达到建筑物质量1%-2%时就可以起到较好的减振效果。水管截面比、长度比以及水头损失系数亦是关系减振率的重要参数。在优化设计中要使减振器达到较好的减振效果,必须使减振器的振动频率接近或等于主结构的固有基频。当主结构计入风重耦合效应后,计算结果会与传统计算方法产生较大的差异,一般规律是主结构重刚比较小时计入风重耦合效应的结构减振率大,而主结构重刚比较大时风重耦合计算结果就比传统结果要小。对高柔结构减振设计必须考虑风重耦合效应,才能正确分析减振效果。在顺风向和横风向计算结果的对比分析中,本文提出了比规范更为严格的刚度限制要求,供设计者借鉴。超高层结构风重耦合效应研究是一个新的方向,本文只做了部分工作,建议今后进一步深入这一领域相关问题研究。
[Abstract]:With the acceleration of urbanization process, more and more super high-rise buildings are developing in the light and soft direction, and there are many urgent problems to be solved in structure design. The wind weight coupling effect is one of them. The wind weight coupling effect is the horizontal displacement produced by the high flexible structure under the wind load, the existence of gravity makes the structural bending moment increase and thus advance. In the static aspect, the horizontal displacement increases with the increase of the horizontal displacement, which shows the change of the natural frequency of the structure and the change of the structural response. In the actual project, the wind weight coupling effect of the super high rise building has been reported, and the influence of the analysis of the wind weight coupling effect is very important. It is necessary.
The main purpose of this paper is to analyze the influence factors of the wind weight coupling effect and find that the characteristics of the high flexible structure change in the wind vibration due to the influence of gravity. At the same time, the general super high rise structure analysis and calculation method is given. In general, the main work is done in the following aspects.
Using the cantilever beam model, the dynamic equation of wind load coupled with large deformation and gravity is derived. The time history response of the wind vibration can be solved by the difference method. The time history calculation shows that the wind weight coupling effect makes the amplitude of the fluctuating wind larger than that of the traditional calculation.
The stochastic wind vibration calculation can be decomposed into the average wind equation and the fluctuating wind equation according to the average wind load and the fluctuating wind load. The average wind equation is equivalent to the static nonlinear equation, and the solution is easy. The other fluctuating wind equation is a nonlinear dynamic equation, which can be obtained by the vibration mode decomposition and the equivalent linearization treatment. The parameter analysis shows that the weight stiffness ratio is the most important parameter affecting the wind weight coupling effect. The greater the value of the structure, the smaller the natural frequency of the structure, the greater the response of the structure. The ground roughness, the inherent damping of the structure and the average wind speed have little influence on the wind weight coupling effect when the structure weight is relatively small, but when the weight stiffness is larger, the wind weight is larger. The coupling effect decreases with the increase of inherent damping and average wind speed.
The equivalent static wind load is a common method in engineering design. This paper adopts the principle of equivalent structural restoring force, and the load along the height distribution can be obtained by derivation. The result shows that the expression of the equivalent wind load in the wind load coupling effect is more than that of the conventional high rise wind load. The coefficient can be designed to be equivalent to the static wind load. There is a difference between the wind vibration coefficient after the wind load coupling effect and the wind vibration coefficient given by the standard. The wind weight coupling effect causes the decrease of the lower part of the distribution of the vibration coefficient and the increase of the upper part of the cloth. The weight stiffness ratio of the structure is an important factor affecting the wind vibration coefficient. Other factors have little influence.
The coupling effect of cross wind and wind is similar to the wind direction, and it is still a decisive factor for the heavy coupling effect of cross wind and wind heavy coupling effect. However, there is a certain difference between the wind weight coupling effect and the wind direction, especially the average wind speed is different, when the average wind speed is small, the structure is ringing. When the average wind speed increases, when the average wind speed increases, the structure response first increases with the increase of the heavy stiffness ratio, and then decreases with the increase of the heavy stiffness ratio. The wind weight coupling effect makes the whole response to the heavy stiffness ratio curve left. For the super high rise structure of the rectangular section, the wind weight coupling is related to the depth width ratio of the cross section, when it is in depth and width. When the ratio is less than 2, the wind weight coupling effect is first reduced and then increased, and there is no definite rule when the ratio of depth to width is greater than 2.
In order to realize the general structure of the frequency domain analysis, in order to realize the general structure of the frequency domain analysis, in order to realize the general structure of the frequency domain analysis, this paper establishes a finite element equation to calculate the coupling effect of wind weight with three degrees of freedom in each layer. When the rate of heart rate is small, the natural frequency decreases with the increase of the weight stiffness ratio, but when the mass eccentricity is larger, the natural frequency increases with the increase of the weight stiffness ratio, and there is a similar conclusion to the case of the rigid center deviation. For the eccentric structure, the wind load coupling effect increases the wind direction and the transverse wind response, but the torsion steering is reduced. The influence of different angles on wind coupling is periodic change, the eccentricity ratio is small, the angle of eccentric position has little influence on the wind weight coupling effect, but with the eccentricity increasing, the angle influence is very obvious.
This paper takes LCVA as an example to analyze the vibration damping law of a tunable damper in a super high rise building. The analysis of the parameters shows that the mass ratio is an important parameter in the vibration reduction. The mass ratio and the greater can obviously play a damping effect. In fact, a better damping effect can be achieved when the mass of the water body reaches the building mass of 1%-2%. The ratio of the pipe cross section and the length of the water pipe can be obtained. In the optimization design, the vibration frequency of the damper must be close to or equal to the inherent fundamental frequency of the main structure. When the main structure is included in the wind weight coupling effect, the calculation result will have a great difference with the traditional calculation method. The structure of the structure of the structure of the main structure is smaller than the traditional result. The wind weight coupling effect must be taken into consideration for the vibration damping design of the high flexible structure, so that the vibration effect can be correctly analyzed.
In the comparative analysis of the calculation results of the downwind and cross wind, this paper puts forward a more stringent stiffness limit than the specification, which is for designers to draw lessons from.
It is a new direction to study the coupling effect of wind and weight of super tall buildings. This paper only does some work, and suggests further research on related issues in this field.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU973.213

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