Test Floor

Floor plan for the structures lab

The main test floor of the Structures Laboratory is a heavily reinforced concrete slab providing 8400 sq ft (780 sq m) of useable test area.

3D rendering of a section of the laboratory floor

This area is serviced by two 25 ton (222 kN) overhead cranes with a clear height of approximately 32 ft (10 m).

The laboratory floor measures 150 x 56 x 3 feet, length x width x thickness (45 x 17 x 0.91 m).

The lab also features about 2000 tie down holes on a 2 x 2 foot (0.61 x 0.61 m) grid.

The floor was designed as a one-way slab supported by two north-south basement walls, three intermediate bearing walls and a footing slab at grade.

Principal reinforcement includes top and bottom mats of #14, grade 60 bars at 12 in (305 mm) centers in both directions.

All slab-wall and wall-footing joints are monolithic. As a result, the test floor, basement walls, and footing slab form a box girder that is 15 ft (4.5 m) deep, 56 ft (17 m) wide and 101 ft (31 m) long. Specified concrete strengths were 4000 psi (28 MPa). Test cylinder strengths at 28 days reached 5000 psi (34 MPa).

Laboratory floor showing Dywidag tie-downs of a safety frame
Laboratory floor showing Dywidag tie-downs of a safety frame
Underside of laboratory floor showing capped ends of Dywidag tie-down bars
Underside of laboratory floor showing capped ends of Dywidag tie-down bars

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 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).

Natural lighting is provided by skylights in the roof and a bank of windows in the north wall. Electric power (110 and 220 volt), compressed air and water outlets are provided around the perimeter wall and in the basement (except for 220 volt lines). A control room is available on the west side of the test floor.