Clay J. Naito, Ph.D., P.E.
Professor of Structural Engineering
Dept. of Civil and Environmental Engineering

Contact Information

Current Research:

NSF: Development of a Blast and Ballistic Resistant Precast Concrete Armored Wall System

NEES-CR: Impact Forces from Tsunami-Driven Debris

Inspection Methods & Techniques to Determine Non Visible Corrosion of Prestressing Strands in Concrete Bridge Components

Daniel P. Jenny PCI Fellowship: Analytical Assessment of the Resistance of Precast Strucutres to Blast Effects

Development of a Seismic Design Methodology for Precast Diaphragms

Development of a Welding Procedure Specification for Field Welding of Precast Concrete Connections

Use of Polyurea for Blast Hardening of Concrete Construction

Estimation of Concrete Respone Under Varying Confinement

Evaluation of Bond Mechanics in Prestressed Concrete Applications

Horizontal Shear Capacity of Composite Beams Without Ties

Lateral Resistance of Plywood and Oriented Strand Board Sheathing After Accelerated Weathering

Past Research Projects

Performance of Bulb Tees with Self Consolidating Concrete

FRP Bridge Decks with RC Parapets

Blast Resistance of a Load Bearing Shear Wall Building

Lehigh@NEES Equipment Site

Reserarch Experinece for Undergraduates

Seismic Evaluation of a Three Story WoodFrame Apartment Building with Tuck-Under Parking

Design of RC Bridge Beam-Column Connections

Response of Waffle Slab Building Systems to Seismic Loads

Horizontal Shear Capacity of Composite Beams Without Ties

In current US bridge construction, precast Bulb Tee, box beam, or AASHTO-I beams up to 160 ft. in length are used. These beams span between the supporting bridge bents or abutments. To provide integrity to the bridge system a field cast deck is installed. The deck is often designed to act as both a wearing surface and as a composite section with the beam. If the demand is great enough, the bond (or cohesion) between the topping and beam could be compromised and the elements will begin to slide relative to one another. The role of horizontal shear ties is to help maintain monolithic behavior after cohesion is lost. Typically horizontal shear ties are made up of an extension of the shear reinforcement from the precast beam section and are subsequently cast into the deck.
To enhance the economics of precast/prestressed members in bridge construction a research program on horizontal shear ties is underway. The project is examining the viability of increasing the nominal horizontal concrete shear stress capacity between precast/prestressed bridge beams and field cast decks. The current requirements prescribed by ACI and AASHTO provide a conservative but potentially unrepresentative estimate of shear capacity for bridge beams. A rational increase in the horizontal shear interface capacity of the concrete topping to beam will provide considerable advantages to precast bridge construction. In particular, the research has the potential for reducing fabrication costs, improving construction safety, and providing numerous initial and long-term economic benefits to the producer and owner.

Clay Naito, Principal Investigator
Dean Deschenes, Research Assistant
Matt Walsh, Research Assistant

Pennsylvania Infrastructure Technology Alliance
Schuylkill Products, Inc.

1. Walsh, M., Deschenes, D., Naito, C., "Horizontal Shear Capacity of Composite Concrete Beams Without Ties Literature Review and Test Program," ATLSS Report No.05-09, ATLSS Center, Lehigh University, June 2005, 70 pages.

2. Kovach, J., Naito, C., "Horizontal Shear Capacity of Composite Concrete Beams Without Interface Ties," ATLSS Report No.08-05, ATLSS Center, Lehigh University, June 2008, 236 pages.
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