Wind forces on single and shielded angle members in lattice structures

• Evaluation of the effect of the thickness, edge, Reynold's number and turbulence on force coefficients of angle members.
• Evaluation and correction of the blockage effect.
• Evaluation of the shielding effect of an angle member on another one.
• Application to simplified lattice towers and comparison with design code predictions.

In this paper, the aerodynamic loads on simplified lattice structures are evaluated taking into account the force on each individual member rather than the conventional methods accounting for the overall truss through solidity ratio and global shielding coefficients. Wind tunnel tests were conducted on single angle members to determine the aerodynamic force coefficients corrected for a blockage effect. Aerodynamic force coefficients were also determined for angle members in the wake of an upstream one to assess the shielding effects. The results show that blockage plays a critical role in the determination of aerodynamic force on angle members with wind tunnel measurements. The experimental results also show three phases for the effect of shielding. The proposed approach based on the contributions of each member of lattice structures allows for the determination of the side force in addition to the drag force. The wind force on typical trusses calculated by this method is compared to the results of methods proposed in different codes.