Comparative Mechanical Performance Analysis of Steel Tube Concrete Lattice Wind Tower Nodes

Literature Overview and Research Context

This paper by Li Bin, Zhao Zhenzhong, and Cheng Yachao, published in the Journal of Chongqing University of Technology in 2020, addresses a critical structural engineering challenge in the rapidly growing wind energy sector. Steel tube concrete (CHC) lattice structures are increasingly used for wind turbine towers due to their favorable strength-to-weight ratio and economic advantages. The connection nodes between members are the critical structural elements that govern the overall performance of lattice towers, and the selection of appropriate connection types directly impacts structural safety, constructability, and economic viability. The research was supported by the National Natural Science Foundation of China (Grant No. 51768056).

Core Technical Content

The authors designed and tested four plane model towers: two with CHC (chord-cutting) nodes and two with tube-plate (gusset plate) nodes. Both static horizontal loading and low-cycle cyclic horizontal loading were applied to evaluate the mechanical performance of each node type. The comparison encompasses failure modes, bearing capacity-deformation relationships, and ductility characteristics.

Comparative Performance Summary

Performance Metric	CHC Node Configuration	Tube-Plate Node Configuration
Static failure mode	Node region failure	Node region failure
Cyclic failure mode	Radial tearing of parent material at diagonal brace connections combined with column base fracture	Radial tearing of parent material at diagonal brace connections combined with column base fracture
Bearing capacity	Higher	Lower
Plastic deformation capacity	Higher	Lower
Suitability for wind tower construction	More favorable	Less favorable

The key finding is that CHC node connections provide higher bearing capacity and superior plastic deformation capacity compared to tube-plate node connections. This conclusion holds for both static and cyclic loading conditions, which is particularly significant for wind tower applications where cyclic loading from wind gusts and turbulence is a primary design consideration.

Failure Mode Analysis

Loading Condition	CHC Node Failure	Tube-Plate Node Failure
Static horizontal load	Node region localized failure	Node region localized failure
Low-cycle cyclic load	Radial parent material tearing at diagonal brace connections + column base fracture	Radial parent material tearing at diagonal brace connections + column base fracture

The identical failure modes under cyclic loading for both node types suggest that the fundamental failure mechanism—parent material tearing at brace connections—is governed by the stress concentrations at the intersection of braces and chords rather than by the specific connection type. However, the CHC nodes delay the onset of this failure through higher initial bearing capacity and greater ductility.

Engineering Practice Implications

For wind turbine tower design engineers, this research provides clear guidance on connection type selection. The superior performance of CHC nodes in both bearing capacity and ductility makes them the preferred choice for CHC lattice wind towers. However, the practical implications extend beyond mechanical performance:

Constructability: CHC nodes require precise pipe cutting and fitting, which demands higher fabrication accuracy but results in cleaner structural geometry.
Cost: The fabrication complexity of CHC nodes may be offset by reduced material usage due to the elimination of gusset plates.
Maintenance: The absence of gusset plates in CHC nodes reduces the number of potential corrosion initiation sites and simplifies inspection procedures.

Standards and Design Considerations

Consideration	CHC Node	Tube-Plate Node
Design standard reference	ASME B31.3, GB 50936-2014	GB 50017, ASME B31.3
Fabrication tolerance requirement	High (pipe cutting precision)	Moderate (plate fabrication)
Welding complexity	High (multi-axis intersections)	Moderate (plate-to-tube welds)
Inspection difficulty	Higher (complex geometry)	Lower (accessible welds)

Study Insights and Reflections

This research makes a compelling case for CHC nodes in wind tower applications, supported by both experimental testing and finite element analysis. The finding that both node types exhibit similar failure modes under cyclic loading but differ significantly in capacity and ductility is particularly important for seismic and wind design, where ductile behavior is essential for energy dissipation. The paper's contribution to the wind energy structural engineering community is significant, as the rapid deployment of wind farms worldwide demands well-understood structural details that can be reliably fabricated and inspected. For practicing engineers, the recommendation to prefer CHC nodes over tube-plate nodes for CHC lattice wind towers is well-supported by the comparative test data. The research also highlights the importance of considering both static and cyclic loading in connection design, as wind towers are subjected to millions of load cycles over their service life.