Closed-form equations for hardening of sand-lime mortar joints

Experimental and analytical investigations have shown that sand-lime mortar joints harden in a nonlinear manner after initial yield; then upon reloadi ng, respond in a linear elastic manner under certain conditions of thrust a nd moment. This paper presents a method to predict this behavior using an e xponential hardening model for the sand-lime mortar. Equations are develope d to predict: (1) the joint rotation and shortening for three unique stress states; and (2) the moment/thrust yield conditions under which linear elas tic responses are possible upon reloading the joint after the mortar harden s. Results show that joint rotation and shortening are influenced greatly b y the thrust intensity and eccentricity. Once the material yields, the nonl inear hardening characteristics of the mortar significantly affect the join t's behavior under loading. Plots of moment/thrust hardening surfaces are p resented for various loading conditions of the joint. The results are consi stent with earlier findings obtained by using a nonlinear finite element mo del of a sand-lime mortar joint.