Investigations and Repairs – Forensic Projects

This page contains a selection of forensic projects completed by Scroggie Consulting Engineers from 2015 to present.

Glass Breakage Diagnostics

We have reviewed the cause of glass breakages and provide reports to stakeholders. Some or the examples include:

1. Failure due to impact - An object impacted the edge of a toughened laminated glass causing the breakage.

2. Failure due to shading - The erection of a scaffold led to differential temperature in around 8 pieces of glass that broke due to thermal stress

3. Failure due to metallic contact with glass - a signage contract drilled holes through the joint between the glass but impacted the edge. The glass slowly cracked over months.

4. Nickel sulphide failure diagnosis - we have reviewed many instances of nickel sulphide failures in toughened glass.

Reports were carefully prepared for each case to explain the cause and allow stakeholders to enter negotiations to have the glass replaced with the appropriate party.

Swimming Pool Trusses

Steel trusses at the Richmond Swimming Pool were corroding in a highly corrosive indoor pool environment. Council engaged us to prepare a report on the condition, prepare repair recommendations and oversee the repairs.

The steel work on 4 trusses was severely corroded, mainly within 2m of the ground level. In some cases the 10mm thick steel members had reduced in thickness down to 2 or 3mm. Seem welds along the length of the members had corroded and could be penetrated with a screw driver.

After the concrete around the bases was removed the extent of corrosion was found to be much greater under the floor. Options were provided to either cut out the affected sections and replace them or to stiffen the existing sections with welded plates. The existing paint was removed and a modern paint system installed to increase the life of the trusses. The concrete was replaced and included additives to extend the life of the structure by 50+ years.

Mitchell House Melbourne

Works carried out for this heritage listed building have been the preparation of extensive repair documentation for the facade. We undertook non-destructive investigations together with removal of concrete to determine the condition of the reinforcement. We proposed repair methods and carried out trial repairs to confirm their suitability. A tender specification was prepared and repair works are to be carried out in late 2015.

A trial break-in was undertaken to determine the condition of the reinforcement and chemical testing was undertaken to determine the alkalinity and chloride content of the concrete. This gives an indication of how well the concrete is protecting the reinforcement. It was found that the original concrete was in good condition despite its age. Many of the defects were due to differential movement of the various substrates or cracking of the render that allowed water to enter the building. 

Other works have been undertaken around the building. We reviewed some structural cracking in the stairs of the building that had caused damage to internal finishes.

Given the age of the building it was important to understand the cause of the damage so that the correct solutions could be specified. We undertook a search of the State Archives to find the original building drawings. Finding these drawings was invaluable as it allowed us to understand the construction, diagnose the likely causes of damage and ensure that the solutions addressed the root cause. We undertake archive searching for many of the projects that we work on.

Another review was to determine the capacity of the existing roof to support live loads. The existing drawings allowed the theoretical capacity to be determined.

A number of other issues were uncovered during our investigations and we produced a report to summarize the risks and suggested time-frames for repairs as a basis for future works. One of the recommendations was that the client should install a restraint system for the existing brick parapet to give it stability in the case of an earthquake. Existing masonry parapets that have a height-to-thickness ratio of 3:1 or more should be strengthened in accordance with Australian Standard 3826. The photo below shows the structure that we designed. The outer skin of masonry was re-tied to the inner skin with Helifix brick ties and the structure was designed to support rope access loads to allow for abseiling (including allowance to support a person in accidental free-fall off a rope).

Public Building, Review of Fence Design

This project involved the review of a series of pedestrian gates, vehicle gates and fences that had been installed around a public building. Our brief was to determine methods by which a member of the public could structurally fail the barriers so as to gain access to the grounds.

These recommendations could then be used to strengthen the gates if necessary.

The report had to be written carefully so that non-technical stakeholders could understand the risks and our recommendations and make appropriate decisions.

Foundation Settlement Repairs, Clifton Hill

The foundation of an existing dwelling settled after previous underpinning due to poor placement of the pins and installation to inadequate depth. This caused serious damage to the façade and internal walls and stress for the elderly occupant. We provided design drawings for underpinning and acted as project manager including seeking approvals from Council, tendering the works, acting as Superintendent during construction and as the clients advocate.

Before photos:

The footing was jacked up to restore the walls as close to their original position as possible. While the cracks closed by around 20mm they could not be fully closed as the brick walls had been previously re-pointed. The main lesson for property owners is that the cause of the damage needs to be addressed before cosmetic repairs are undertaken. Always consult an engineer or builder when cracks occur in your building.

After photos:

Condensation Review

We were asked to review and provide recommendations on a widespread condensation problem following the refurbishment of an existing building. A new fixed glazing suite was installed behind the original glazing to improve the acoustic insulation of the facade. Condensation formed on many of the windows.

Technical explanation: Cold air cannot hold as much water as hot air. In general terms, surface condensation can occur when warm moist air comes into contact with a colder surface. The air that contacts the surface cools down and releases moisture forming condensation on the cold surface.

In this case the condensation occurred on the inside face of the external glass where the air is warmer and moist and the glass was cold. To prevent condensation from occurring it is necessary to either:

• Remove the moisture from the air, or
• Remove or reduce the difference in temperature so that the air retains its moisture.

Typically it is easier to remove or reduce the amount of water than to control the difference in temperature. Our report outlined a trial method of removing the moisture from the air.

As a rule of thumb, do not install new fixed glazing behind existing glazing to try to create double glazing. Condensation is almost certain to occur, even if a desiccant is added to the new cavity. Your options are to install new factory sealed double glazing or to make the new internal glass openable by using a sash. This allows access to the cavity to replace desiccant and clean the glass.

Discuss your ideas with a facade consultant if considering an upgrade to your glazing.