Large-Scale Structures Laboratory

The Large-Scale Laminar Soil Box system provides an unprecedented experimental facility for evaluating the complex manner in which such structural systems as buildings and bridges interact with the surrounding, supporting soil during a large earthquake. Design and construction were supported by the U.S. Department of Energy (DOE) and National Nuclear Security Administration as part of the DOE’s long-standing commitment to earthquake safety and resilience of critical infrastructure. This new experimental capability will inform the DOE’s specific interests in facility safety, but also will be available to a broad spectrum of earthquake safety stakeholders.

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.

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).

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.

The foundation slab of the four-cell box girder provides a basement area for locating the blow-down and other accumulators for the servo-hydraulic actuators, access to the underside of the tie-down floor for the anchoring of test fixtures, and general storage. Headroom in the basement is about 8 ft, and the space is used to run electric power and hydraulic lines to and from experimental equipment on the floor above. The basement also houses an experimental preparation area.

Hydraulic hardlines feed the laboratory from an external pump house just outside the southeast corner of the building. Also, seven ports along the centerline of the laboratory floor provide access to feed, return and drain lines to reduce the need for long runs of hydraulic hose.

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.

Load rating is limited by the allowable tensile and compressive stresses in the pre-compressed zone at the base of the wall. The wall is 20 ft wide, 19 ft high and 2 ft thick. It is perforated with tie-down holes on the same 2 ft by 2 ft grid as the test floor. The wall may be used in conjunction with modular reaction blocks to permit a variety of reaction and anchorage loading configurations including L-shaped systems.

Direct access to the test floor for heavy vehicles is available through roll-up doors at the northern, eastern, and southern ends of the building.

A ramp also provides vehicle access to the basement from the northern end of the storage yard. A removable grate and staircase permits crane access to the basement at the east side of the floor.

Researchers can contract with local companies or arrange to have test-specimens built and stored in the fabrication yard prior to testing in one of our labs.