Compression Tests for Wall Panels

Function

• The primary purpose of a compression test is to assess how shear walls — structures that transfer and support loads — behave while supporting loads. Compression tests measure how well walls resist and absorb tension and compression forces. For example, the end studs or chords in walls must be capable of supporting lateral and gravity loads. Lateral loads include wind force and seismic activity, while gravity loads include roofs and floor joists. If the walls fail and buckle under the compression forces, this can lead to structural failure in the building.

Testing Conditions

• Generally, wall panels are assembled adjacent to each other and tested using vertical axial compression methods according to STM standards. Wall panels are anchored to the laboratory floor using tension rods and spreader beams to prevent movement during testing. However, more than one type of setup may be used to assess how walls react to loads in different situations. For example, compression tests can introduce vertical forces that are controlled or not controlled to assess behavior under changing conditions.

  Additionally, compression tests measure the load bearing capacity of different types of wall panels. Tests assess panels with reinforced concrete framing, steel framing or no framing at all. During compression tests, wall panels may be of varying heights and thickness. Wood panels are also used to compare the load bearing capacity with concrete or masonry walls.

Measurement Tools

• Tools such as hydraulic rams apply force along steel beams placed in the center of the wood and concrete panels. Electronic load cells and amplifier units measure the amount of force applied on the beam using electronic signals. Other devices used to gauge tension and pressure during compression testing include deflection transducers and dial indicators. These are placed on both the back and front surfaces of the wall to test axial strain. An axial strain measurement indicates how well the panels stretch or yield while continuing to carry loads. Deflection transducers assess the rate of lateral deflection or curvature in walls under loads. Typically, the rate of a wall's deflection during testing indicates the likelihood of its structural failure.

Considerations

• Although compression tests attempt to mimic real conditions for wall panel performance in buildings, structural planning strongly influences the behavior of wall panels in buildings, according to the Portland Cement Foundation. For example, the type of connections used to join wall panels to footings, roofs and floors will impact how well walls transfer loads to the structure's foundation and shear walls. Moreover, the positioning of walls in relation to floors and roofs will also affect how well they transfer loads throughout the building.