When the history of Civil Engineering unfolds its chapters, load testing enjoys a special place. This highly specialized branch came to counter the structural loads. According to Wikipedia, Structural Loads are forces or accelerations applied to a structure that leads to structural damage or even demolition. The first recorded incident that emphasized the architectural load testing dates to 1930 when significant cracks extending from basement to cellar were recorded at a football stadium in the United States.
What’s the Purpose of Load Testing?
A load test is the approved process to test the integrity and strength of the piles to ensure that it would support the structure even during adversities such as natural calamities or other accidents. To perform the structural load test, the structure should at least be 50+ days old as per the American Concrete Institute (ACI).
There are two widely accepted load testing—Static Load Testing and Dynamic Load Testing. Although both have their own merits, let us delve into the advantages of these both.
Static Load Testing:
Considered to be the traditional form of load testing, static load testing will help an engineer determine the bearing capacity of the deep foundations. The pressure that is applied to the pile is relatively slow and is time-consuming in a static load testing. During static load testing, calibrated load cells are leveraged to monitor the load while the electrical displacement transducers would record the pile settlement. As the name suggests, the weight of static load testing would be consistent. Static load testing is standardized by ASTM DD1143.
Some of the advantages of Static Load Testing include:
- Feasibility to get swift results
- Can be performed without an execution plan such as a walkthrough, inspection, etc.,
Dynamic Load Testing:
Unlike static load testing, dynamic load testing doesn’t follow a consistency is exerting the pressure on the piles. Standardized by ASTM D4945, dynamic load testing helps in ascertaining the end bearing and the shaft resistance. Since it’s less time consuming, a geo-technical engineer can perform multiple dynamic load testing in a day, and it’s for the same reason that dynamic load testing has been widely accepted by geo-technical engineers over the past couple of years. Several studies suggested that a dynamic load test is relatively crucial in determining the capacity and integrity of the pile if performed by expert engineers.
Since many debates surrounding static load testing v dynamic load testing are rife, many universities and engineering professors conducted several studies to ascertain as to which form of testing gives an edge over the other. According to a study by Y.K Tandel, Research Scholar with NIT, dynamic test load is carried out owing to low operational costs. Also, the study revealed that the settlement measured through static load test was higher when compared to dynamic load testing. The report further mentioned that the static load test was ideal in case the test load is low while the dynamic load test is perfect to provide a holistic picture of the pile integrity.
Based on the many such studies, it was concluded that a static load test should be carried out initially before dynamic load testing to ensure the overall strength of the structure. However, based on your structure’s size, a geo-technical engineer would be the right person to tell which test should be performed.