I believe most expansion joint (xj) catalogs provide either effective diameter or effective area for their joints. Use this value to specify effective diameter in CAESAR II xj input if you wish the program to include a structural load in any load case with pressure. This structural load is the specified pressure (e.g. P1 or P2) times the effective area of the pipe. This load is placed on either end of the xj, pointing away from the xj.