Common Non-Destructive Methods of Testing Timber for Structural Strength
Timber is slowly replacing other materials such as stone and concrete as the primary construction material for modern homes. It can be attributed to the many benefits of timber, such as its recyclability and structural strength. However, if you are working on a renovation project for a timber house, it is vital to conduct tests on the existing wood. The tests allow contractors to assess the structural strength of the material. This article highlights the non-destructive tests builders use to establish the structural strength of timber structures.
Stress Wave Timing -- The first type of timber test is the stress wave timing, and it is primarily used to test decay within a piece of timber. To determine the possibility of decay, the wood being tested is struck with an impact device fitted with an accelerometer. The first accelerometer is crucial because it emits the start signal to the timer. Another accelerometer contacts the other end of the timber and sends a stop signal to the timer. The time it takes for the stress wave to travel between the two accelerometers indicates the level of decay in the piece of timber. If it takes a short time, then the timber has a high level of decay and vice versa.
Drilling Resistance Test -- Another method used by builders to test timber for structural integrity is drilling resistance. As the name suggests, drilling resistance is based on measuring how much resistance the timber exerts on a drilling needle. A drilling needle is drilled into the wood and placed under constant drive. As the needle drills, a resistograph machine measures the energy needed to drill through the timber depending on the needle's drilling depth. The measurement is recorded electronically and transmitted to a personal computer for processing. If the energy needed to drill the centre of the timber is high, then it is a sign that the wood is in good condition. However, if the needle drills with very little energy, then the wood is not structurally sound.
X-Ray Testing -- Wood properties vary, and this affects the load-bearing capacity. One way to grade wood based on strength is through X-ray testing. The X-rays travel through the lumber and hit a detector on the other end. During the process, the wood absorbs the radiation and the unabsorbed radiation reaches the sensor. If the density of the wood is high, it absorbs much of the radiation and only allows a small amount to reach the detector. However, if the wood's internal density is low, a lot of the radiation reaches the detector, thus indicating low-grade timber which is not fit for load-bearing purposes.
For more information on structural timber, contact a contractor.