Attach (8) Pier_PAPA_Load_Restriction_Clarification.pdf

Subj: PIER PAPA LOAD RESTRICTION CLARIFICATION

A. Clarification of the 500 psf load restriction on the 1960s Section of Pier PAPA:

As per the Base Charleston Pier Papa load restriction memo dated January 22nd, 2018, the uniform load limit for the 1960's section of the pier is 500 psf. This limit is based on the design load of the 1960s pier section and the observed condition of the double tee beams documented during the 2016-2017 Collins Engineering Inspection.

A 500 psf load is a uniformly distributed live load, this means that the structure can safely support having 500 lbs of force on every square foot of its entire surface area. For visualization, 500 psf would be the equivalent of an 8 ft tall water bladder on top of the pier. The structural load limit is based on maximum moment or shear force created by this 500 psf distributed load.

The loading on the 1960s section was analyzed for each Prestressed Double Tee Beam as a simply supported span between each bent. Each Double Tee Beam has width of 5 ft, and a span of 20 ft from bent to bent. It is assumed that each of these beams can support a 500 psf distributed load, which equates to a maximum moment force (and shear force) that the beam can withstand.

Forces that are not distributed over the entire beam, such as point loads from equipment, also generate a moment and shear force on the beam. The point loads are considered to be within the load limit so long as the moment force (and shear force) they induce on the beam does exceed the one created by a hypothetical 500 psf distributed load.

Roughly speaking, a 25,000 lb Point Load located at the center of a 20 ft beam would create the same max moment force as a 500 psf distributed force.

All the loads on a beam contribute to reaching the maximum supportable force, or capacity of the structure. Therefore, all the equipment on a span section of the pier contributes to reaching the 500 psf limit, but the amount of this contribution depends on the location of the load.

The following load combinations would likely exceed the 500 psf restriction for the 1960s Section:

1) More than two 18,000 or 20,000 lb sinkers centered on a single 5ft wide beam section between bents.

2) Fully Flooded 8X26 LR or LWR Buoy with single point of contact at center of span.

3) Two 67,000 + lb conex boxes supported by corner footings (assumed point loads), positioned perpendicular to pier length so that two footings are within 5 ft of each other centered on the same beam between bents.

Given weights of various equipment likely to be stored on the 1960s Section of Pier PAPA, it is not expected that the 500 psf load limit will impact the majority of equipment/gear storage.

B. Safe Vehicle Transit on Pier:

As per the Jan 22nd, 2018 load restriction memo, trucks and boat trailers may be operated on the 1940s section of the pier, no more than one vehicle at a time. The load rating analysis was based on AASHTO Legal Load configurations for typical trucks and trailers, which are typically less than 80,000 lb (40 Ton)

Attachment (8) Solicitation No.: 70Z08522QLREP0001

Pier PAPA Load Restriction Clarification

GVW. Therefore, up a 40 Ton GVW truck may be operated on the pier, as long as the guidelines from the memo are followed.

C. Cranes with Outriggers:

The Jan 22nd 2018 Memo states that cranes may be used for lifting on the 1960s section of the pier so long as the outriggers are, “not positioned with 10 ft of the edge of the pier section…”. This would prohibit crane lifting within the first 997 ft of the 1960s section, which is not the intention of the load restriction. Given this realization, the restriction is now modified so that crane outriggers are, “not positioned within 5 ft of the edge of the pier section (to include the centerline joint)”.

LT Bohdon Wowtschuk

CEU Miami – Ocean Engineer