Ziad AzziFollow

Document Type



Doctor of Philosophy (PhD)


Civil Engineering

First Advisor's Name

Arindam Gan Chowdhury

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Amal Elawady

Second Advisor's Committee Title

Co-Committee Chair

Third Advisor's Name

Ioannis Zisis

Third Advisor's Committee Title

Committee Member

Fourth Advisor's Name

Seung Jae Leee

Fourth Advisor's Committee Title

Committee Member

Fifth Advisor's Name

Peter Irwin

Fifth Advisor's Committee Title

Committee Member

Sixth Advisor's Name

Nipesh Pradhananga

Sixth Advisor's Committee Title

Committee Member

Seventh Advisor's Name

Caesar Abi Shdid

Seventh Advisor's Committee Title

Committee Member


aeroelastic modeling; lattice towers; transmission lines; Wall of Wind; system identification; aerodynamic damping; buffeting response; dynamic amplification factors; gust effect factors.

Date of Defense



The transmission infrastructure in the U.S. faces substantial risk from hurricanes. Wind-induced damage poses an immense threat to the electric power grid; such hazards have significantly impacted the supply, generation, and delivery of power to large portions of the U.S. in the past. When exposed to strong winds, critical demands in several elements in transmission tower-line systems may exceed corresponding capacities and trigger various modes of failure. Enhancing the resilience of the transmission grid against increasing threats from hurricanes and strong winds is therefore of critical importance. The results of 1:50 aeroelastic scaled models of a self-supported steel lattice tower and a multi-span transmission lines system under simulated hurricane wind speeds are presented. The aeroelastic tests are conducted at the NSF Wall of Wind Experimental Facility (WOW EF) at the Florida International University (FIU). The models are tested at various wind speeds ranging from 35 m/s to 77 m/s (full-scale) for wind directions varying between normal and parallel to the alignment of the transmission line. Two system identification (SID) techniques are utilized to validate the analytical along-wind aerodynamic damping of the model and provide insights on its crosswind counterpart. A buffeting analysis is conducted to estimate the response of the tower, the conductors and the entire system and compare it to measured values at the WOW. Similarly, drag and moment coefficients are calculated from the measured response, and dynamic amplification factors (DAF) are computed. Results show that the coupling effects between the transmission tower and the conductors are significant. In some instances, such effects are favorable and in others, unfavorable. Other findings also show that there is a need to include the change in turbulence intensity along the height of the tower in the established analytical modeling approach. The drag coefficients are shown to be in agreement with values proposed in the standards. However, there is a need to consider moment in lattice tower design to account for bending in the members that might be introduced by any rigid connection. The resonance contribution is shown to reach a maximum of 18% and 30% of the peak response for the single tower and multi-span transmission lines systems, respectively.






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