Abstract

Concrete tilt-up buildings are a common subset of a class of building referred to as rigid-wall-flexible-diaphragm (RWFD) structures. Common diaphragm types are plywood, oriented strand board, or metal deck. Masonry wall buildings with flexible diaphragms are also examples of RWFD buildings. Tilt-ups have performed poorly in past earthquakes, with the primary weakness being the anchorage between walls and roof. In the seismically active western United States, design was governed primarily by the Uniform Building Code (UBC) until the advent of the International Building Code (IBC). Before the 1973 UBC, it was common practice by design engineers to use the nailing of the plywood roof diaphragm to the wood ledgers (which are bolted on the inside face of the walls) as the de facto anchorage for out-of-plane wall forces (Figure 1). This indirect tie arrangement relied on the wood ledger in cross-grain bending and the plywood panel in tension near its edge. Cross-grain bending and tension are both very weak material properties of wood. Wall anchorage design forces before the 1973 UBC were specified as 0.2Wp under allowable stress design (ASD), where Wp is the tributary wall weight being anchored. In the 1971 San Fernando earthquake, the wall anchorage in many tilt-up buildings performed poorly. The use of this indirect wall tie led to wood ledgers failing in cross-grain bending and to plywood edge nailing tearing through panel edges from the wall anchorage tension loads. Partial roof collapses and wall collapses were common in the areas of strong ground motion.

Disciplines

Architectural Engineering

Number of Pages

3

Publisher statement

STRUCTURE is a registered trademark of the National Council of Structural Engineers Associations (NCSEA). Articles may not be reproduced in whole or in part without the written permission of the publisher.

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URL: https://digitalcommons.calpoly.edu/aen_fac/184