Unreinforced Masonry Testing

1. What is Unreinforced Masonry Testing?

Unreinforced masonry (URM) testing consists of non-destructive and intrusive investigations on brickwork and stonework, which are common and often used in heritage building systems throughout New Zealand. Tests can be done on the individual masonry units, the bonding mortar, or the combination of these.

The non-destructive tests include:

  • Scanning. Utilising GPR, magnetic induction, UT, or a combination of these techniques, scanning can be done on most structural masonry types. The following information can often be collected through scanning
    • Identifying unfilled cells within concrete block masonry structures
    • The presence of voids or delamination
    • The presence of metal ties
  • Camera inspection. Once the presence of reinforcement or ties have been confirmed, our inspection camera can be utilised to check the condition of these elements; whether they are well-maintained or corroded. This service may be done in conjunction with a localised break-out (intrusive testing)

The intrusive tests include:

  • Mortar joint shear strength test
  • Compressive strength test
    • On an extracted prism of URM
    • On individual masonry units, i.e. bricks or mortar cubes
  • Anchor test. There are two categories of tests that can be performed on anchors imbedded in URM.
    • Proof test, to check the quality of installation.
    • Ultimate test, to check the maximum load that can be sustained before failure
    • The above tests can be applied in shear or tensile (pull-out) testing.
  • Scratch test for mortar strength estimation in-situ.

2. When would you use Unreinforced Masonry Testing?

URM testing will be very useful when structural engineering consultancies are required to perform retrofitting design on URM structures. URM structures have been shown to perform poorly during earthquakes and it is now mandatory to strengthen these structures in the most seismically active regions in New Zealand, such as Wellington and the Canterbury area. Our service can provide the information required by the design engineers to perform their calculations for the retrofitting purpose.

3. What are the Benefits of Unreinforced Masonry Testing?

Just like any other construction materials, it is important to know the actual properties of the masonry units constituting the concerned structures before any reliable retrofitting design can be performed. However, masonry structures, especially those composed of clay bricks or stones, are so inhomogeneous that their strength properties highly depend on a range of factors, primarily workmanship. It is not advisable to perform the retrofitting design using the value of these strength parameters obtained from literature. Through our service, the representative value of these parameters can be provided. Beside the information obtained through scanning, the following strength parameters required for retrofitting design can be obtained through the services above

  • The shear strength of the mortar bed joint under different axial load intensities
  • Single unit as well as prism masonry compressive strength to see the slenderness effect
  • Anchor pull-out or shear capacity of the masonry unit through anchor test. Anchors are the means of attaching structural steel members to masonry structures required for strengthening.

When the representative values of these parameters are known, design engineers can perform their retrofitting design with higher confidence.

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