Vertical Wind-induced Vibration Response For Single-story Light-weight Steel Structures With Gabled Frames

In recent years, as the rapid development of modern science and technology, the productionand quality of steel has improved substantially in China, coupled with the strong support ofnational policy and advocacy, portal frame structure has been rapidly developed, and it has beenwidely used in industrial buildings, commercial buildings, transportation facilities and other civilprojects. However, due to the impact of global climate change, the vertical wind-induced effectsof portal frame structure becomes more and more prominent, including the roof structure is rentand blown, the steel frame structure is thrown off.As portal frame structure has the characters of light weight, great flexibility, lower dampingand natural frequency, so it is very sensitive to wind loads. Wind load is one of the control loadsin the structure design. However, Load Code for Design of Building Structures and TechnicalSpecification for Steel Structure of Light-weight Buildings with Gabled Frames are not clearlydefined the vertical wind vibration coefficient of this type structure. In the design of the portalframe structure, there are many different opinions on whether considering the impact of thevertical wind-induced vibration to the portal frame.The article first use PKPM to design five different solid models of portal frame structurefrom12m to36m, then, use the modal analysis of ANSYS to get the natural frequencies andmode shapes of them. At the same time, the article select the junction of the purlin and roof asthe research node of reflecting vertical wind-induced vibration response, furthermore, adoptfrequency domain analysis to discuss the influence of parameters such as high order modeshapes, different roof spans, different damping ratio, vertical fluctuating velocity spectrum andsupport restraints, which are usually critical to the vertical wind-induced vibration responses ofthe portal frame structure. Finally, according to a practical structure, the article gets the verticalwind-induced displacement vibration coefficient based on frequency method and considering thecombined effect of the variable parameters.By changing the different parameters, the article use a wind power spectral analysis methodto analyze vertical wind-induced vibration responses of the portal frame structure and draw someimportant conclusions:The natural frequency of portal frame is very close to the frequency of wind, and thesmaller the span, the greater the frequency of the portal frame; when we analyze verticalwind-induced vibration response of portal frame structure, the contribution of the first two ordermodal is the maximum, and consider the first two order modal can meet the accuracy.Changing the roof span of the portal frame has a great effect to the vertical wind-inducedresponse and vertical wind-induced displacement vibration coefficient. The bigger the span, thegreater the vertical wind-induced displacement vibration coefficient, the increased value from 5.242%to21.897%; increasing the damping ratio and adopting rigid connection can effectivelyreduce the vertical wind-induced vibration response of the portal frame, but changing supportrestraints has little effect to vertical wind-induced displacement vibration coefficient.Not only consider the effect of level fluctuating wind speed spectrum and ignore the verticalfluctuating velocity spectrum in the analysis; the article finally taking a true engineering as anexample, the results showed that: vertical wind-induced vibration has a prominent effect to theportal frame structure and the designer should take into account the vertical wind-induceddisplacement vibration coefficient in the design.