配电线路支盘扩底桩风振响应分析

Analysis of Wind Vibration Response of Expanded Bottom Pile in Distribution Line

在土质较差地区,直埋式配电杆力学分析模型仍按照简化的固结约束考虑不再适用,支盘扩底桩作为一种新型配电杆基础型式,能显著提升抗风性能,但目前针对这种基础型式电杆的受力特性和风振响应研究较少。为考虑土质较差地区桩-土-结构相互作用(PSSI)对配电杆受力特性的影响,建立了杆-桩-土有限元模型,开展了桩周土弹性约束下的新型电杆动力特性分析,进行了脉动风激励下的简化固结约束模型、考虑PSSI效应弹性约束直埋桩模型和新型支盘扩底桩模型的风振响应分析。结果表明,考虑PSSI作用后,结构的自振频率要比简化的固结模型频率有所降低,降低幅度可达12.6%,相应振型也有所滞后;PSSI效应对动力响应影响更为明显,支盘扩底桩可有效减小动力响应下PSSI效应对结构的影响;支盘扩底桩与传统等径桩相比,结构刚度增加甚微,但可降低结构风振响应的加速度峰值,从而起到减小配电杆风振动力荷载的作用,还可降低沿电杆分布的弯矩峰值,从而提高电杆的抗风性能。

In areas with poor soil quality,the mechanical analysis model of directly buried distribution poles is no longer applicable according to the simplified consolidation constraints.As a new type of power distribution pole foundation,the support-pan expanded bottom pile can significantly improve the wind resistance performance.At present,there are few studies on the mechanical characteristics and wind vibration response of this foundation type of pole.In order to consider the influence of pile soil structure interaction(PSSI)on the mechanical characteristics of distribution poles in poor soil areas,the pole pile soil finite element model is established,the dynamic characteristics of new poles under elastic constraints of soil around piles are analyzed,and the simplified consolidation constraint model under fluctuating wind excitation is carried out Considering PSSI effect,the wind-induced vibration response of elastic constrained directly buried pile model and new branch belled pile model are analyzed.The results show that the natural frequency of the structure considering PSSI is lower than that of the simplified consolidation model,and the reduction range is up to 12.6%,and the corresponding mode shape is also delayed.The PSSI effect has a more obvious influence on the dynamic response,and the support plate and expanded bottom pile can effectively reduce the influence of the PSSI effect on the structure under the dynamic response.Compared with the traditional equal-diameter piles,the structural stiffness of the support-disk expanded-bottom piles has little increase.The support plate and expanded bottom pile can reduce the acceleration peak value of the wind vibration response of the structure,so as to reduce the wind vibration force load of the distribution pole,and also reduce the peak value of the bending moment distributed along the pole,thereby improving the wind resistance performance of the pole.