Learning Column

Column Illustration (trim)

The learning column is a non-structural hollow steel column in the Tea Room (Room 100). It is used as a teaching tool to help students grasp the concepts of force, stress versus strain, and beam bending.

Strain is defined as the amount of deformation that an object undergoes because of an applied force. It is important to measure strain when analysing a structure in order to learn how the material behaves. Strain data can also help predict failure. The I-beam and the column foundation were built into the architectural plans for Beamish-Munro Hall. The structural engineer who designed the experiment recommended that the experiment apply no more than 50 kilo-newtons (kN) of extra load to the building.

The column illustrates how I-beams and steel columns handle dead loads (the load of the building itself) versus live loads like people — or, in this case, a hydraulic jack which mimics live loads. Using the jack, force can be applied to the base of the column, raising the column slightly. It in turn applies a force to the I-beam above it. This causes both the beam and the column to deform slightly, and that deformation is measured by strain gauges on the column and on the beam.

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In total, four strain gauges are mounted on the I-beam and four are mounted on the column. There are linear displacement gauges located against the beam and above the hydraulic jack, to measure the column’s compression and the beam’s total displacement. A load cell under the column measures the applied force from the jack.

Details

Strain gauge: A strain gaugeA strain gauge

The strain gauges on the column and I-beam are manufactured by Measurements Group, Inc. There are eight 120 Ohm foil strain gauges, four around the column and four on the I-beam above. They receive an excitation voltage of 2.5V every 1s.

The gauges operate in a broad temperature range (-75 C to 175 C) along a curve, but the curve is flat enough in the operating range (between 19C - 25C) that it does not need to be taken into account during readings. Data from all of the strain outputs is read by a National Instruments Compact FieldPoint strain gauge device.

Strain gauges on iBeam: The three strain gauges on the iBeam.The three strain gauges on the iBeam.

Two linear potentiometers are placed on the column, one to measure the column's height from the floor before and after applying the load, and the other to measure the beam's displacement before and after the load is applied. The potentiometers are manufactured by Penny & Giles, and have a range of 0-20mm. The outputs (two linear pots as well as the load cell) are fed into a Micro-P signal conditioner and displayed on the box at the bottom left of the frame. The data also goes into the live building system.

The hydraulic jack, placed between the column and the foundation, is manufactured by Enerpac and rated to carry a load of 10 tons (approximately 90kN). The load cell is also rated for 125kN - this is a maximum rating. The structural engineer recommends that the maximum applied load be 50kN, so the pump is limited to 5000psi (approximately 47kN of applied force), so that is there is no possible way of accidentally applying more force than the structural rating.

Strain graph: A strain curve of the gauges as tested on 1018 (low-carbon) steel. The gauge factor of the gauges is 2.060.Strain graph: A strain curve of the gauges as tested on 1018 (low-carbon) steel. The gauge factor of the gauges is 2.060.
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Learning Column CAD drawing14.84 KB
Learning Column CAD (from above)2.42 KB