28 July 2005
Apply an impact factor of 25 percent to the maximum listed wheel loads for the
design of deck slab, crane girders, and pile caps. The impact factor is not applicable
to the design of piles and other substructure elements.
Mobile Crane Loadings.
The deck design for open and floating structural types of piers and wharves is
usually controlled by mobile crane loading. However, the operational constraints
imposed by under specifying mobile crane loadings are severe. Consequently, take
care to specify realistic loading. Refer to Table 3-2 for designated mobile cranes
applicable to each functional type of pier and wharf. As a minimum design the pier
or wharf for the designated mobile crane, however, check with the local activity to
confirm whether a crane larger than that designated could be used at the facility.
See Figure 3-3 for wheel loads for 50-, 70-, 90-, 115-, and 140-ton capacity mobile
cranes. The information in Figure 3-3 is for typical truck cranes, although rough-
terrain type mobile cranes are also used on piers and wharves. Tire contact area
should be as defined by AASTHO. As a rule of thumb, ground pressures for "on
rubber" lifts are about 10 percent higher than tire inflation pressure. Crane
manufacturers recommend that the majority of lifts be made on outriggers. In
addition, capacities for "on rubber" lifts are substantially less than for "on outrigger"
lifts. Hence, loads for "on rubber" lifts are not listed. Design all piers and wharves
and their approaches for the wheel loads from the designated truck crane.