Four-Point Bending

Four-point bending is used effectively to measure the bond strength. In four-point bending a uniform maximum moment and an area of tension at the bottom of the specimen is achieved. Failure always occurs at the brick mortar interface and generally occurs at the center joint of the specimen.

Modified ASTM E518 and C67

 

The basic test setup for the four-point bending test is shown above.

The moment in the center mortar joint is

and thus the stress at midspan is found with

 

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