Evaluation of Racking Performance of Wood Portal Frames with Different Wall Configurations and Construction Details

Abstract

The performance of portal frame walls was studied using a finite-element model verified with results from tests of full-size portal frame walls. Parameters such as wall height, metal strap type and location, doubling of the bottom plate, sheathing placement, and nailing pattern were investigated. Results indicate that in all cases, lateral load capacity and stiffness are greatly reduced with the increase of wall height. Considering the effect of different metal strap types and locations, the tensile strength of metal straps has the greatest impact on the lateral load capacity and stiffness. Walls with metal straps placed directly on the framing members outperform walls with metal straps placed over the sheathing. For walls with a double bottom plate and two rows of nails fastening the bottom plate, the stiffness and lateral load capacity are slightly increased compared with walls with a single bottom plate. For walls with unblocked sheathing at midheight, the lateral load capacity is the same as in walls with continuous sheathing running from the bottom of the wall to the top, but the stiffness is slightly less.