Study On Dynamic Property And Wind Induced Fatigue For Large-span Bidirectional Beam String Structure

In recent years,the beam string structure has been widely applied in the roof construction of various large-scale public buildings like stadiums,airports,railway stations,exhibition centers.Because the beam string structure is constructed by virtue of prestressing technique and it belongs to a highly flexible structure which is characterized in large span,light quality,small damping and great flexibility,so the structural fatigue problem under the effect of wind load has attracted attention of the engineering field.In this paper,the study on large-span bidirectional beam string structures includes the following aspects:①Based on data collected through the linear filtering method,a wind speed time history simulation was carried out on a 100-year frequency storm of southeastern coastal area in this paper.Vertical and horizontal fluctuating wind pressures of the bidirectional beam string structure are respectively simulated by Panofsky spectrum and Kaimal spectrum.The analysis on time-history simulation indicates that vertical and horizontal wind speed time histories are well matched with the corresponding wind spectrums.②Based on the self-balancing structure of beam string structure,this paper firstly analyzes the static performance and stability of the structure so as to better grasp the basic loading characteristics of the structure and help carry on subsequent researches.Then adopt the parametric study method and take many influence factors into account including tension coefficient of lower chord,central angle of upper beam bending,beam-to-rope stiffness ratio,vertical span ratio,quantity of jackstays and the like so that obtain the change rules of structural displacement and the internal force of jackstay.An eigenvalue buckling study of unidirectional and bidirectional beam string structures with initial imperfection is carried out based on the data.The result shows that the bidirectional beam string structure has a good stability.③This paper.studies the dynamic property and wind-induced response of the bidirectional beam string structure and analyzes frequency characteristics and vibration mode of large-span bidirectional beam string structure.It is concluded that the fundamental frequency of beam string structure increases as the tension coefficient,but the tension coefficient has a little influence on high-order frequencies;the increase of structural vertical span ratio is advantageous to enhancing the stiffness of structure and enlarging its fundamental frequency;the decrease of case bay in the beam string structure can obviously increase the fundamental frequency of structure.Then calculate the wind-induced response of structure by adopting the time domain method.It shows that the structural dynamic response can be controlled by increasing the vertical span ratio and damping of structure.Increasing the initial prestress can result in decreases of the whole structural displacement and stress on the upper chord,at the same time,lead to an increase of tress on partial draglines.④Based on Miner linear cumulative damage rule,utilizing the rain-flow counting method,the wind-induced fatigue of bidirectional beam string structure is researched in this paper.It is concluded that the most destructible positions are near the sidebeam string structure.Increasing the structural damping is very advantageous to the fatigue life of the structure.On the whole,the fatigue life of structure increases with the increase of vertical span ratio,but the fatigue life of some components weakens with the increase of vertical span ratio.