Experimental Studies on the Lateral Load Carrying Capacity of Pier Foundations for Bridges-Paper

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The study examines how embedded length and diameter affect the lateral-load behavior of cylindrical bridge pier foundations in sand, particularly when scour reduces the soil supporting the pier. Model tests at IIT Delhi used single piers embedded in uniform dry sand, with different length-to-diameter ratios and lateral loading.<br /><br />The tests found that increasing embedded length reduced lateral deflection at the sand surface but increased maximum bending stresses. As the length-to-diameter ratio increased, the center of rotation moved upward; simply extending the pier therefore did not produce a proportional gain in lateral-load capacity. Conversely, reducing the ratio—such as by increasing pier diameter—lowered the center of rotation and mobilized greater passive soil resistance.<br /><br />Measured centers of rotation were lower than predictions from traditional rigid-bulkhead and subgrade-reaction theories. The study also notes that soil response becomes nonlinear as loading increases, limiting the applicability of approaches that assume a constant relationship between soil pressure and displacement.<br /><br />When additional lateral resistance is needed, the authors favor increasing pier diameter rather than embedded length. Greater diameter can improve passive resistance without increasing the maximum bending moment for a given lateral load, potentially allowing a thinner, lighter pier. Increasing embedded length, by contrast, raises bending demand and may require a heavier structure, while also presenting construction difficulties. These conclusions are based on model tests of single cylindrical piers in sand.

Keywords

bridge pier foundations

lateral-load behavior

embedded length

pier diameter

scour effects

sand soil

bending stress

center of rotation

passive soil resistance

model tests