# Characteristics of a new UT-type prefabricated joint for rectangular steel tubes under combined axial-moment loading

## TL;DR

This paper introduces a new UT-type prefabricated joint for steel tubes that handles construction tolerances and improves performance under combined loads.

## Contribution

The UT-type joint with adjustable sleeves and an energy-dissipating segment is a novel solution for managing construction tolerances and plasticity.

## Key findings

- Axial tension increases initial stiffness by 42.6% while axial compression reduces yield moment by 24.5%.
- Cyclic loading tests show the joint has good energy dissipation capacity.
- High axial forces can cause brittle failure, requiring attention to buckling in the energy-dissipating segment.

## Abstract

This study proposes a UT-type prefabricated joint incorporating adjustable sleeves (±5 mm tolerance) and an energy-dissipating segment to address the practical demands for construction tolerance management and plasticity assurance. Through systematic static and cyclic loading tests, the paper examines the mechanical behavior of UT-type joints under the combined axial force and bending moment. The results demonstrate that axial force significantly influences joint performance. Specifically, axial tension enhances the initial stiffness by 42.6% (μ = 0.4), while axial compression reduces the yield moment by 24.5%. Cyclic loading tests confirm the joint’s notable energy dissipation capacity. However, high axial forces induce brittle failure risks; thus, practical engineering applications require attention to buckling in the upper connecting plate of the energy-dissipating segment. Additionally, a simplified trilinear restoring force model is proposed, with an error margin of less than 10%. This model adapts to various loading conditions via axial force-dependent parameter adjustments and demonstrates satisfactory accuracy across validations.