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Eight years ago, when this engineer began in the welded wire industry, it was unclear what the capabilities of welded wire reinforcement were, let alone what the strength of materials and mechanical properties or testing methods were all about. Test books at that time placed WWR in a low strength and low ductility category. Until recently, WWR was a lesser extent, for structural applications. Now, with the latest technology and practices of cold-working rod to wire plus controlling speed and temperature of wire welding, the industry is producing reinforcement with much higher strengths and higher ductilities for more structural concrete applications. There has been excellent growth in this industry in recent years in structural WWR. It's being specified and used in many more building and bridge structures today. This paper deals principally with high strength steel reinforcement recognized and documented in the latest ACI 318 Structural Building Code and the latest ASTM Standards, A 82, A 185, A 496 and A 497. Reinforcing yield strength today are up to 80,000 psi (550 Mpa) Since AASHTO/LRFD and ACI specifications coincide for the most part, ACI references will be discussed. Being associated with the Wire Reinforcement Institute, this paper makes reference more to welded wire reinforcement. The paper will address code provisions related to all types of steel reinforcement in general. The name of the successful project game is to use the most readily available and most efficient reinforcing materials. There has been a considerable amount of performance research on reinforced slabs and paving done in recent years. Luke Snell of Southern Illinois University has done work on this subject. His paper, titled: "Cover of Welded Wire Fabric in Slabs and Pavements" was presented at another ACI Technical Session in Seattle, Washington on Jobsite Quality, Part 1. It implies that performance is achieved when steel reinforcement is placed and located property.

The use of high strength reinforcement in seismic zones 3 and 4 dates back to 1979, in the design and construction of the Continental Plaza Building, Seattle, Washington, a 37-story concrete building. The design team comprised of Whitley-Jacobson Company, engineer of record; Neil Hawkins, Professor of Engineering, University of Washington; the fabricator, supplier of WWR, and the architect. A combination of shear wall and moment frame design was selected as the most economical lateral force resisting syst4em. Grade 75 WWr was used as horizontal reinforcement to confine the column cores.

Theoretical moment-curvature analyses were performed in this study for analyzing the effects of cyclic behavior of reinforcing steel on seismic performance of reinforced concrete members. Cyclic stress-strain relations for reinforcing steel were estimated from an analytical model proposed in the literature and considering the onset of buckling of a steel rebar defined according to an approach proposed in this study. The ACI318-95 provisions for evaluating probable flexural strength are used for relating interstory drift and strain demands in longitudinal reinforcement of typical sections of reinforced concrete members subjected to earthquake loading.

Headed reinforcement uses one or more anchorages, called heads, attached to the ends of steel reinforcing bars. Such heads serve to develop a bar in a relatively short distance, and can also better confine the interior concrete. For over a decade, headed reinforcement has had extensive field use in major structures subjected to cyclic fatigue and dynamic loading, as well as thorough laboratory testing on both bare steel bars as well as on concrete members with headed reinforcement. Such test have also demonstrated the superior performance of headed reinforcement under seismic loading conditions, even in high moment zones, and joint regions. This paper addresses both: (I) aspects of design and detailing with headed reinforcement for seismic resistance, and (ii) aspects of the concrete material performance as it is modified by headed reinforcement. Specific advanced design tools are discussed including empirical equations, strut-tie modeling procedures, a new membrane stress theory, and a new cyclic reinforcing bar bond-slip theory, together with design examples for bridge structures. Currently, ACI 349, CSA 474, and several overseas codes provide design rules for headed reinforcement. Where necessary these rules may be supplemented by experience, engineering judgment, empirical guidelines, and test results. New standards, regarding the use of headed reinforcement in concrete, are pending with both ASTM and ACI 318; which when incorporated should further facilitate the design process.

The application of headed reinforcement as a replacement for conventional reinforcement was investigated in two projects relating to the seismic design of bridges. In the first project, a test unit composed of a column, cap beam, footing and knee joint was designed entirely with headed reinforcement, and in footing and knee joint was designed entirely with headed reinforcement, and in the second project a test unit representative of a multi-column bridge bent was investigated, having a cap beam design utilizing both headed reinforcement and a mechanical coupler system. In both investigations the use of recently developed reinforcement products facilitated simplified detailing, particularly in the cap beam/column joint region, resulting in reduced reinforcement congestion the joint zone and improved constructability. The design and performance of the test units under simulated seismic loading are presented.