Description
In Japan, mid-size electric transmission towers are composed of steel angle members connected with snug-tightened high-strength bolts. The dominant load for these structures is wind load; specific Ministerial Ordinances are used for structural design. Seismic design was omitted due to the small seismic effective mass. However, collapses have occurred recently due to the increasing wind intensity caused by drastic climate change. Consequently, there is a high demand to reinforce conventional towers currently in operation.
Typically, lap joints are used to connect the steel angle members in the construction field. This is done for workability purposes, and minimizing components is recommended for safety reasons. The lap joint employs snug-tightened high-strength bolts, accommodating slippage and introducing an eccentricity that generates a secondary bending moment. The design guideline explains how to evaluate the amount of eccentricity at the joints. However, the evaluation method when reinforcing the main members was not shown in the past due to its perceived unnecessary nature.
This paper reports the flexural buckling strength evaluation method of reinforced steel angle members under eccentric load. A theoretical approach is used to derive the evaluation formula, considering the effect of eccentric load and the amount of reinforcement. Finally, small-scale experiments are conducted to validate the proposed design formula. The test results confirm that the proposed formula can reasonably evaluate the strength of reinforced steel angle members.
