922
4326.009
Thorkildsen, Eric; Mervyn Kowalsky; Nigel Priestley - Editors: I. Holand, T.A. Hammer, F. Fluge
International Symposium on Structural Lightweight Aggregate Concrete, 1995 Proceedings
Paper
Norwegian Concrete Association
1995
June 20-24, 1995
299-311
Y
The California Department of Transportation (Caltrans) historically has used structural lightweight concrete for bridge construction, although not indiscriminately as a substitute for normal weight concrete. The most recent policy memo written in 1986 suggests the use of lightweight concrete in deck replacement and rehabilitation, at locations where local aggregates are unsuitable, and as a cost effective material for long span superstructures. Preliminary plans to bridge two large bodies of water on Northern California with long span structures over 2 km in length has prompted Caltrans to review and update their overall policy on lightweight concrete incorporating the latest technological developments. This paper will explore several general areas of bridge construction where Caltrans is considering the increased use of lightweight concrete. An overview of the current research at the University of California San Diego on Lightweight Concrete Bridge Columns will also be presented. Caltrans intends to use lightweight concrete in whatever applications prove to be cost effective. Research will continue on material performance in high seismic zones. Current policy will be updated to encourage the expanded use of the aggregate.
Tests performed at UCSD on lightweight concrete bridge columns indicate that the non-ductile shear strength of the concrete is not significantly altered. However, the ductile shear strength appears to be lower based on strain levels in the transverse steel as well as observations on aggregate cracking. More detailed analyses are underway to develop design recommendations for lightweight concrete.