for Highway Construction Page 298 of 715 SECTION 500 – STRUCTURES for Highway Construction Page 299 of 715 SECTION 501 – STRUCTURES
501.01 Description.
Construct structures .
501.02 Materials.
Not specified.
501.03 Construction Requirements.
A.General. Before placing concrete , obtain approval for the excavation depth and the foundation materials .
B.Cofferdams and Cribs . Construct cofferdams and protect fresh concrete against damage from a sudden stream rise or from erosion. Do not place timber or bracing inside cofferdams or cribs that cannot be removed without damage to the concrete. Use cofferdam or crib material of sufficient length to a llow a 2 -foot lowering of footings. Prevent concrete materials from being carried away when pumping from the foundation enclosure interior. Do not pump when placing concrete or for at least 24 hours thereafter, unless it is done from a suitable sump or well point separated from the concrete work. Remove cofferdams, cribs , sheeting, and bracing down to the elevation of the original ground l ine or to the new stream bed elevation for a channel change or to the top of footings in dry holes. Remove so there is no damage to the new structure.
C.Foundation Seal. Construct a concrete foundation seal when specified. Pump out the foundation enclosure and place the masonry in the dry. Ensure the seal has set sufficiently to withstand the hydrostatic pressure before pumping to dewat er a sealed cofferdam . When weighted cribs are used and the weight is used to partially overcome the hydrostatic pressure acting against the bottom of the foundation seal, provide special anchorage (e.g., dowels, keys) to transfer the entire weight of the crib into the foundation seal.
D.Drainage of Substructure . Thoroughly and effectively drain the material behind abutments, retaining walls, and wing walls by using granular backfill .
E.Bearing and Anchora ge. Set bearing plates in exact position to have a full and even bearing on the masonry. Ensure that anchor bolts are in the correct location and elevation. Adjust the position of expansion bearings to correspond with the temperature at the time of installation.
F.Placing Concrete . Place the concrete in slab spans, T -beams, or deck girders in 1 continuous operation.
Source: Idaho Standard Specifications for Highway Construction, 2023 Edition. Pages 334–334 of 768.