Performance of linkage bars for restraint of bridge spans in earthquakes
DOI:
https://doi.org/10.5459/bnzsee.46.1.25-39Abstract
Many New Zealand bridge decks consist of simply supported spans, which are interconnected with steel linkage bars. The main purpose of the bars is to restrain and prevent the bridge spans falling in an earthquake. The prediction of the forces imposed on the linkages is quite indeterminate because of the many variables that affect the response of adjacent bridge spans during strong earthquake motions. For economic reasons it is also usually not practical to make the linkages so strong that they will never fail under the strongest likely shaking. Linkage bars are therefore designed for a reasonable and practical strength, and are then detailed to yield and have large plastic extensions before failing in tension.
The paper presents the results of laboratory tensile testing of a range of linkage bar types and conclusions are made regarding the most suitable bar assemblies, taking into account tensile ductility and cold temperature fracture toughness.
Recommendations are made regarding methods of predicting earthquake loads in linkage system and on design detailing for linkage assemblies.
References
AS 1252:1983 “High-strength bolts with associated nuts and washers for structural engineering”.
AS/NZS 1252:1996 “High-strength bolts with associated nuts and washers for structural engineering”.
AS/NZS 4291.2:1995 “Mechanical properties of fasteners. Part 2: Nuts with specified proof load values – Coarse thread”.
AS/NZS 4671: 2001 “Steel reinforcing materials”.
Chapman, H.E., Lauder, M.K. & Wood, J.H. (2005). “Seismic Assessment and Retrofitting of New Zealand State Highway Bridges”. Proceedings NZSEE Annual Conference.
Clifton, G.C. (2011). Personal Communication.
DIN EN ISO 4032 “Hexagon nuts, style 1”.
Macalloy (2012). “Bar and Cable Systems”. Macalloy 650 Stainless Specification.
Mandeno, W.L. (2010). Personal Communication.
NZS 3402:1983. “Steel Bars for the Reinforcement of Concrete”.
NZS 3404: Part 1:2009. “Steel Structures Standard”. Standards New Zealand.
NZTA (2003). “Bridge Manual”, Second Edition, Including amendments to December 2004. New Zealand Transport Agency, Wellington.
Reid Construction Systems (2008). “Product Catalogue and Design Guides”.
Roberts, B. (2010). Personal Communication. DOI: https://doi.org/10.1016/B978-0-240-81475-9.50013-X
Wood, J.H., (2012) “Performance of Linkage Bolts for Restraining Bridge Spans in Earthquakes”. Report prepared for New Zealand Transport Agency, Wellington.
