Structure And Mechanical Properties Of Photovoltaic Brackets In Collapsible Loess Area

More and more photovoltaic brackets(PVB)were built in collapsible loess areas with the wide application of solar energy,and the problem of damage of PVB due to the settlement of foundation is becoming serious.Although the method of foundation treatment or pile foundation can solve this problem,but its cost is relatively high.Therefore,the new PVB which can adapt to the foundation settlement has a broad application prospect.This paper firstly analyzes the mechanical properties of the fixed PVB and points out that the bracket may be damaged and affecting the safety of power supply when the foundation is settled unevenly in collapsible loess area.Then,the large-span truss PVB that can adapt to foundation settlement was put forward,which pulsating wind and the wind vibration response of the bracket was simulated and analyzed by MATLAB respectively.Then the modal analysis and the influence of prestress on the deflection of the bracket was carried out by SAP2000 software.Finally,PVB with adjustable purlin for uneven settlement of foundation is proposed,including slotted hole and sleeve node.8 slotted hole and sleeve node specimens were designed and the static loading test was carried out.The failure characteristics and the load-deflection curves were observed and recorded respectively.The calculation method of the settlement amount of the foundation that the bracket can adapt to was put forward after analyzing the bearing capacity and the deformation capacity of the specimens.The main conclusions are as follows.(1)The bracket's ability of resisting the pull-down load is weak when the front support at the end of the fixed PVB settled,the settlement of a support will cause large deformation of the nearby PVB structure and significant internal force of this and adjacent bracket structure,of which purlins and rear columns are most likely to be damaged.(2)Large span-truss PVB is sensitive to fluctuating wind load,and the wind-induced vibration coefficient is recommended to be1.89.This bracket requires large cross-section size to meet the requirement of bearing capacity and deflection,which is not economical.The application of prestress can't effectively reduce the deflection value of members.(3)The specimens of the PVB with adjustable purlin all bent and damaged in the middle span of the purlin and the nodes are not damaged.The difference of bearing capacity between slotted hole type and sleeve type is within 6.29%.Both types of bracket can adapt to the settlement of foundation.