STATIC AND DYNAMIC BEHAVIOR OF CONCRETE LIFT JOINT INTERFACES

Displacement controlled shear tests on concrete lift joint specimens w ith different surface preparations are conducted to compare dynamic sl iding joint behavior with the static behavior. Experimental results in dicate that the coefficient of friction decreases with the increase in normal load, under both static and dynamic shear The shear strength i s dependent on surface preparation. Monolithic specimens and water-bla sted joints show higher shear strengths than untreated joints and plan e independent joint surfaces. No strength degradation is noticeable un der dynamic sliding shear tests since hysteresis loops are very stable . No dependency of shear strength on frequency content of the imposed shear displacements is observed. An empirical lift joint constitutive model is developed as a function of a basic friction coefficient and a roughness friction coefficient that is dependent upon the type of sur face preparation. The proposed Lift joint constitutive model is used t o study the seismic sliding response of a 90-m concrete gravity dam.