text: It is important for a few reasons. \n\nThermal Expansion--temperature changes cause the metal to expand and contract.--Without the joint the concrete would crack.\n\nBuilding settlement.   With a parking garage, there is a lot of weight coming on and off during the day and night.   It is a much heavier building when it is full of cars.  This causes a sponge effect with the ground.   The joint acts as a sort of shock absorber.