A combined footing is to be used to support columns A and B with a center-to-center spacing of 15 ft. The columns carry the following loads: Column A Column B P V P V Ultimate loads Service Loads 200 150 50 0 400 300 50 0 ons and Practice Problems 345 The underlying soil is a well-graded sand with c’ = 0, $’ = 36Â°, y = 126 lb/ft?, with a very deep groundwater table. Using LRFD, design a rectangular footing to meet the ultimate limit states using a resistance factor of 0.45. Assuming the average CPT tip resistance of the sand is 300 kg/cmÂ², check to see if your design meets serviceability limits. Adjust the design as needed.