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Design Criteria (Load Ratings)
The test floor was designed as a continuous one-way slab spanning the narrow direction of the Laboratory from one exterior wall to the other, and supported on three intermediate load-bearing walls. Two-way plate action was considered at boundaries, discontinuities and for the distribution of large point loads applied to the slab. The capacity of the floor for loads distributed over large areas, is determined by the flexural reinforcement. Based on ACI, and using appropriate strength reduction factors, the flexural capacity per unit length of slab is estimated to be 300 K-ft/ft (1335 kN-m/m).For concentrated loads, the capacity is controlled by shear and this is estimated to be 40 K/ft (584 kN/m),again based on ACI. Using load factors of 1.4 for dead loads and 1.7 for live loads, the rated load of the test floor is estimated as follows:
Uniform loads and patch loads of any size, in balanced or unbalanced configurations, in any direction up or down: 3.4 K/sq ft(163 kN/sq m) North-south line loads, in any single slab, in any direction up or down: varies linearly from 35 K/ft (511 kN/m) at mid span to 23 K/ft (336 kN/m) at 3 ft (0.93 m) from the supports Single point loads, with no other load applied within 12 ft (3.7 m) of the load, and not adjacent to the basement stair openings: 300 K (1335 kN) upward, 240 K (1068 kN) downward
A lower live load factor of 1.4 may be used for experimental live loads that are controlled and monitored. In this case the above load ratings may be increased by 20%.
The strong wall on the east side of the Laboratory is intended for small-scale experiments. It is a vertical cantilever projecting from the exterior wall of the basement. Reinforced with mild steel, the wall has been post-tensioned to a uniform compression of 950 psi (6.5 MPa). Load rating is limited by the allowable tensile and compressive stresses in the precompressed zone at the base of the wall.
The box girder test floor weighs about 5000 K (22,250 kN). Desirable mass ratios of between 50 and 100 imply that specimen weights for dynamic tests should be in the range of 50 to 100 K (222 to 445 kN).
