Compressive strength and constitutive behavior of clay tile prisms

Thirty - one structural clay tile prisms were tested in uniaxial compression. Twenty - three of these prisms were 8" thick, and the remainder were 13" thick. The prisms were constructed with running bond, a full bed joint, and face shell bedding for the head joint. The 8" prisms were tested at various angles to bed joint. The 13" prisms were tested with the bed joint either horizontal or vertical. The prism failure pattern depended on the bed joint angle. The failures were the result of slipping along the bed joint, cracks along principal stresses, or a combination of the two. The stress - strain relations were determined by linear variable displacement transducers over gage lengths that included mortar joints. The stress - strain curve was approximately linear up to about 33% of ultimate stress. From 33% of ultimate to ultimate, an exponential fit was more appropriate to model the curve. This non-linear behavior in the upper portion of the stress - strain curve was influenced by mortar joint deformations. Several of the prisms were loaded, unloaded, and reloaded during the test to observe the effect of the cycling load. There appeared to be little difference in the results with this loading pattern and the monotonically loaded prisms. Beyond ultimate stress, plastic deformations were apparent in the prisms under a cyclic load. When the prism was reloaded, the strain increased dramatically from what it had been at unloading. The testing program showed the wide variation that can exist in prism testing. Many factors, including construction practices, affect the results.