How do you inspect and test bridge structures in the field?

1 Visual Inspection

The most basic and common method of bridge inspection is visual inspection, where you observe the condition of the bridge components, such as the deck, beams, columns, joints, bearings, and foundations. You look for any signs of damage, corrosion, cracking, spalling, settlement, or misalignment that may affect the structural performance or serviceability of the bridge. You also check for any drainage issues, vegetation growth, or debris accumulation that may cause deterioration or obstruction. You can use a checklist, a camera, a binocular, or a drone to assist you in visual inspection.

2 Non-Destructive Testing

Sometimes, visual inspection is not enough to detect the internal defects or hidden problems of bridge structures. In such cases, non-destructive testing (NDT) techniques can be used which do not damage or alter the material or structure being tested. Ultrasonic testing, for example, uses high-frequency sound waves to measure the thickness and detect flaws in bridge materials like steel or concrete. Magnetic particle testing uses a magnetic field to reveal surface and near-surface cracks or discontinuities of ferromagnetic bridge materials such as steel or iron. Radiographic testing utilizes X-rays or gamma rays to produce an image of the internal structure of bridge materials like concrete or metal. Additionally, thermographic testing uses infrared cameras to measure surface temperature and detect anomalies or defects in bridge materials like delamination or moisture.

4 Corrosion Testing

Corrosion can significantly reduce the strength, ductility, and durability of bridge materials, as well as increase maintenance and repair costs. Thus, it is essential to inspect and test the corrosion level and rate of bridge structures in the field. Some of the corrosion testing methods that can be used are half-cell potential testing, which measures the electrical potential difference between the bridge material and a reference electrode; linear polarization resistance testing, which measures the electrical resistance of the bridge material to a small applied current; and galvanostatic pulse testing, which measures the charge transfer resistance of the bridge material to a short pulse of current to assess the corrosion rate and condition of the protective coating.

5 Geotechnical Testing

The last method of bridge inspection and testing that we will discuss is geotechnical testing, which focuses on the soil and foundation conditions that support the bridge structure. Geotechnical testing can help you identify and evaluate any geotechnical hazards and risks that may affect the stability and performance of the bridge structure, such as liquefaction, erosion, settlement, or slope failure. There are a few geotechnical testing methods you can use in the field, including standard penetration testing, cone penetration testing, dynamic cone penetration testing, and vane shear testing. Standard penetration testing measures the resistance of the soil to a standard hammer and sampler to determine the soil density and strength. Cone penetration testing measures the resistance and pore pressure of the soil to a cone-shaped probe to obtain the soil profile and properties. Dynamic cone penetration testing measures the penetration depth of a cone-shaped tip driven by a drop hammer to estimate the soil strength and stiffness. Lastly, vane shear testing measures the torque required to rotate a vane in the soil to measure the soil shear strength.

6 Here’s what else to consider

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