Anchor bolt load cells, also commonly known as centre hole load cells, are extensively used to determine the load in rock bolts, tiebacks, foundation anchors, cables or struts depending on the application. They are also used for compressive load measurement between structural members i.e. tunnel supports or at the junction between a beam and top of a pile strut.
Encardio Rite provides different types of anchor load cells as follows:
Resistive Strain gauge load cells
These are most commonly used. load cell and provide very accurate and reliable data.
It is a resistive strain gauge type load cell used to determine the load in rock bolts, tieback anchors etc through a centre hole. It is based on the Wheatstone bridge principle and has eight 350 Ohm resistance strain gages, wired to form a 700 Ohm bridge, inside a cylinder of high steel strength. These eight gages are mounted around the circumference at 45 degrees to each other.
Model ELC-30S-H High Capacity Center Hole Load Cell
The ELC-30S-H is a high capacity centre hole resistive strain gauge type load cell. It comprises sixteen 350 Ohm resistance strain gages, wired to form a 1400 Ohm bridge, inside a stainless steel cylinder of high steel strength, in a load cell with a capacity above 5000 kN. The 3500/185 and 5000/202 load cells are welded using the electron beam welding technique.
Hydraulic load cells
These are fluid-filled with a vibrating wire pressure sensor attached to them, to convert the load into a frequency output. These are low cost but are less accurate as they are affected by temperature.
Model ELC-31V Hydraulic Center Hole Load Cell
It is filled with fluid with a vibrating wire pressure sensor attached to it, to convert the load into a frequency output.
A solid load cell for stress measurement in tunnel supports and struts is also available on request.
Vibrating load cells
These generally use three vibrating wire strain gauges mounted at 120° to each other to minimize the effect of uneven and eccentric loading. If specifically required, six vibrating wire strain gauges are also used. To determine the load, the average of the three (or six) readings are taken.
It comprises a cylinder of high strength martensitic stainless steel with three vibrating wire strain gauges mounted at 120 degrees to each other to minimize the effect of uneven and eccentric loading. To determine the load, an average of 3 readings is taken.