The current structural design of Jackson Crossing uses a concrete base supporting a wood truss and bearing wall system. This system was found to be more than sufficient for the design loads determined through Submission A to Submission C.
For a design alternative, a complete concrete system will be investigated for both the gravity and lateral system. The gravity system will be two-way reinforced flat plates suppoted by columns. The lateral system will be intermediate concrete moment frames. While the existing structural system of Jackson Crossing is a light and low cost solution, a concrete structure is worth considering as it is durable and provides a thin floor system. The design alternative will not increase the overall height of the building and will keep the same typical floor to floor height unless the alternative floor system decreases the floor to ceiling height.
One problem with the design alternative is how the added weight of a complete concrete system compared to the existing wood frame system will impact the transfer beams at the ground floor level. One of these critical beams is highlighted in red in Figure 1. In this figure the column transferring loads from the five floors above it is marked with a green circle and an arrow pointing to its location. The existing specifications of the highlighted transfer beam are 48” by 36” with 14 #10 bottom bars and 8 #9 top bars. The loads on this transfer beam from the alternative design will be analyzed to determine the impact of the revised dimensions on the garage level clearance below the beam.