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

Evaluation of Bond Mechanics in Prestressed Concrete Applications

Successful designs of prestressed structural elements include considerations for transfer and development lengths of prestressing strand. The effectiveness of bond strength at the strand-concrete interface controls the transfer and development lengths. Three major mechanisms contribute to bond strength: adhesion at the strand-concrete interface, frictional forces enhanced by radial forces in the strand at prestress release (the Hoyer effect), and mechanical resistance (interlock) due to axial bearing forces on the helical strand. Current tests for bond strength use untensioned strand and thus only incorporate adhesion and interlock mechanisms in the specimen. In this research program, several tests will determine the relative contribution of each of these three major mechanisms.

The research program includes testing on self consolidating concrete (SCC) and high early strength concrete (HESC) specimens to compare the effectiveness of bond strength development in each material. Other influences, like the affect of confining reinforcement on strand length development, will also be explored through additional specimen series.

Clay Naito, Principal Investigator
Tyler Tate, Graduate Student Researcher

Pennsylvania Infrastructure Technology Alliance
Schuylkill Products, Inc.

1. Tate, T., and Naito, C., "Evaluation of Bond Mechanics in Prestressed Concrete Applications," ATLSS Report No.05-09, ATLSS Center, Lehigh University, July 2005, 134 pages.

Page Last Updated Friday, 24-Jun-2005 18:23:32 EDT