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SEAoT Houston January 2021 Webinar

  • 01/21/2021
  • 12:00 PM - 1:00 PM
  • online webinar
  • 23


Registration is closed


Noon-1:00 pm (1 PDH)

Online Webinar via Zoom


Horizontal Shear Transfer for Unreinforced Interfaces: Are the ACI Design Provisions Too Conservative?


Carl J. Larosche, PE, F.ACI, Senior Principal, Wiss, Janney, Elstner Associates, Inc.


The design for horizontal shear transfer at an interface between concretes placed at two different times occurs in several scenarios in new construction and repair applications. The ACI 318-19 and ACI 562-19 design requirements for interface shear transfer limit the nominal strength of an intentionally roughened, unreinforced interface to 80 psi. This limit can be punitive for some applications, such as toppings on precast hollow-core slabs and double-T beams, partial-depth repairs on slabs, and bonded overlays. When interface areas are large, requirements to add interface reinforcement can result in considerable time and expense.

This presentation by Chuck Larosche, PE, F.ACI will provide an overview of an ongoing research study on interface bond funded by ACI and PCI with additional support from the WJE In-House Research program. They will review the ACI design requirements for horizontal shear transfer and will present the findings of a laboratory investigation of interface shear strength for repair applications and toppings in precast construction. The research explored the use of the direct shear (guillotine) method to assess the interface shear bond strength and investigated the correlation between the direct shear strength and direct tensile pull-off strength. The research results indicate that interface shear strengths significantly higher than the ACI nominal shear strength of 80 psi can be achieved. Potential applications of the research findings will be discussed, including the use of mock-ups for shear and tensile bond testing to evaluate design strength and for quality control.


Carl Larosche joined WJE in 2004 with more than twenty years of experience specializing in consulting services for the preservation and restoration of historic and existing structures. In addition to his preservation work, Mr. Larosche has extensive experience in building envelope, including traditional building materials as well as current state-of-the-art materials.

Prior to WJE, Mr. Larosche was a Principal of Sparks, Larosche & Associates and worked for The Texas Department of Transportation (TxDOT). Mr. Larosche's diverse background includes structural design, investigation, and evaluation of existing structures and materials. He has successfully combined his broad construction background with his knowledge of material behavior in existing structures to provide rare insight and knowledge in the area of masonry, concrete, and steel evaluation, including strengthening and repair of these materials.

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