Boundary Condition Effects on Static Response of Ultra-High-Performance Concrete (UHPC) Slabs

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Title: Boundary Condition Effects on Static Response of Ultra-High-Performance Concrete (UHPC) Slabs

Author(s): Bradley Foust and Theodor Krauthammer

Publication: Special Publication

Volume: 321

Issue:

Appears on pages(s): 5.1-5.14

Keywords: Blast; Compressive membrane; Protective design; Shock; UHPC slabs

Date: 9/29/2017

Abstract:

The boundary conditions at the supports of reinforced concrete slabs, specifically the amount of lateral and rotational restraint, dictate how they respond to particular loads. Membrane (in-plane) forces are present in slabs when their boundaries are sufficiently stiff, therefore restricting the slabs from lateral translations in addition to rotations. Increases in compressive strength and ductility in ultra-high-performance concrete (UHPC) introduce additional strength enhancement not present in Normal-Strength Concrete (NSC).

Ten reinforced concrete slabs were quasi-statically tested in a static water chamber that allowed hydrostatic forces to be utilized as a loading technique on the slab. Of the 10 slabs, 4 were simply supported, and the remaining 6 were rigidly restrained. The load-deformation responses of laterally restrained slabs were then compared to those of simply-supported slabs to determine the enhancement due to the boundary conditions (i.e., compression membrane action). The results of these experiments were then compared to the results of response calculations based on plastic theory.

Valuable data on rigidly-restrained UHPC slab response were obtained from the experiments. The experimental results were compared to the results of the associated numerical analyses. Existing plastic theory should be used with caution when calculating the ultimate resistance of UHPC slabs. The experimental and numerical results showed that UHPC slabs with sufficiently rigid boundary conditions have a static resistance two-and-a-half-times greater than the traditional yield-line theory resistance for UHPC slabs due to compressive membrane effects.