Forensics

Architectural Glass Claims

Forensic Services Newsletter

Fracture pattern on sheet glass after dropping a ball bearing from a height of one metre.

Architectural glass failures can be visually arresting, so this month's newsletter is lavishly adorned with photographs from our files, going back decades.

Storage

The most costly architectural glass claims tend to be ones that occur when glass sheets are damaged in storage, before they are even installed on a building. One reason is the huge numbers of sheets involved, and our consultant Aini Ling was involved in one claim in 2004 involving 40 million sheets.

By design, glass facades are exposed and therefore vulnerable during construction. Image on right shows welding spatter, embedded in glass surface.

Another curious feature of storage claims is that damage occurs at all! After all, it is usually plain water that is the culprit. It seems illogical that glass can be installed on buildings and exposed to the elements for decades without damage, but can be irreparably damaged by water in a few weeks in storage. However this is the case and we are skilled in the identification of such damage, from site inspection to laboratory microscopic examination.

Installation

There are a host of other damage mechanisms that can occur during installation and these include welding spatter, inappropriate cleaning or removal of cementitious material and accidental scratching by one or other of a myriad of contractors on a building site. We can examine glass windows insitu and advise on the origin of such damage.

Fracture originating from inside the glass window fixture. Glass window shattered at a power station in Taiwan. The turbine behind had oversped and fragments had been expelled. Needless to say we were investigating the turbine failure rather than the window!

In-Service Damage

After windows are installed and occupants move in, glass windows can begin to fail. These might simply involve single cracks, or windows can fail in a spectacular manner, with the internal stress of tempered glass causing total crazing in the familiar way that some windscreens shatter.

Analysis of a window failure. Crazed fracture pattern on left in tempered glass on an elevator wall. Fracture origin is shown above.
Staining of windows by mist from evaporative cooling towers. Fracture pattern on tempered glass on side of an escalator. Ginza Plaza explosion in Singapore in 1992.
Location of cracked storefront window glass in Hong Kong. Fracture pattern on glass indicates crack origin.

Sometimes there is a history of problems involving dozens of windows over years, but when we are finally consulted there are no actual failures to examine at that time. Insurers become exasperated when they hear that they need to wait until the next failure occurs before anything can be done. Failure analysts have a better chance of getting an answer when they have an actual failure to work with.

Float Glass

In carrying out these types of claims it is important to have knowledge of the six different types of float glass used in architectural applications. Each has its characteristics, not only in terms of the types of failures that occur, but in practical considerations in terms of going about the investigation and taking samples.

One of a series of glass failures in a building, but evidence largely lost. Meandering pattern typical of heat-induced cracking.

Fractography

A knowledge of glass fractography can be useful during investigations into thefts and suspicious fires. Sometimes these investigations hinge on access, and whether a glass window was broken by impact or heat can be important. In one Singapore court case this question arose during the trial, held 8 years after the event. We were able to go back to the site during the trial, 8 years later, and recover glass shards that revealed the answer.

If you have any questions regarding this newsletter, please direct them to us by clicking on "Ask a Consultant" button.

Regards,





Barry Dillon