SFPE 12th International Conference on Performance Based Codes and Fire Design – Hawaii

Members of our team attended the SFPE fire conference in Hawaii last week. Team member Hailey Quiquero gave a fantastic presentation on modelling timber structures in fire from a FEM point of view. Her work is a collaboration with the University of Canterbury. Dr. Gales gave a presentation regarding steel connections based on team alumni Matt Smith’s work as he could not make the conference.

Grenfell

Carleton student Chloe Jeanneret visiting Imperial College and research team alumni and now ARUP Intern Arlin Otto were able to visit Grenfell Tower after the fire in July.

A lot will be said in the coming months, if not years regarding the fire seen at Grenfell. The few things Id say, is that cladding fires are not the only challenge we face in the community of fire engineering. Tunnels, Developing countries, Wild fires, New building materials, Risk based methodologies, etc., and I can go on, are all areas for the last decade we as a community have been stating require additional attention – many are receiving attention.

GFRPs, Heritage Timber, Education, Sustainable Concretes, Performance Based Fire, New Instruments and More!

Summer conferences

We have an exciting two weeks ahead. The research team will be visiting 4 conferences in the coming weeks to present 6 presentations. In addition we will have a 7th presented at ASFE and this will be announced at a later date. The below are brief descriptions of each. Open access versions will appear at a later date.

CSCE Symposium in Vancouver (May 31st to June 3rd)

Mass Heritage Timber Performance in Fire presented by Arlin Otto. The paper looks at a comparison of timber performance in fire of three unique types of timbers. The paper will also discuss adhesive bleeding seen in LVL panels .

Creep of Prestressing Steels in Fire

Measured creep strain at high temperature for three different prestressing steels.
Measured creep strain at high temperature for three different prestressing steels.

Our new paper, Creep of Prestressing Steels in fire, is now in press in the journal Fire and Materials (you can access it here; an open access version is to come). It is a great piece about prestressing steels used in Post-tensioned structures. We show how high- temperature creep is effected by the chemical composition of the steel. While it may seem obvious to some, the effect this can have for prestressing steel in high temperatures seen in real fires is astounding.

Consider several different prestressing steels, all behaving the same in ambient service temperatures, but when stressed and heated (700 MPa and 427C) as if they were in a fire, one fails after 5 hours, were the others fail below 1.5 hours. All likely due to the chemical composition from the production process of the steel (see the above figure). These tests are described in the paper (that and about 80 others). The same trends shows the same effect in simple strength tests at high temperature.

The paper also describes the use of digital image correlation to measure the strain at high high temperature. An innovated technique, but leading to important insights about true areas and strains as the steel fails in high temperature. A compiled video of a creep test is provided below which illustrates how quickly tertiary (third stage) creep takes effect before failure.

The above video shows the prestressing steel coated in a black and white speckle texture pattern. Image correlation is a powerful technique for measuring high temperature strains. Its a very simple process described below

Digital image correlation is an excellent strain measurement technology. This figure shows two images taken using image correlation techniques on a piece of prestressing steel. The top image illustrates time zero with an applied stress of zero. The second photo below shows the specimen at 100 seconds, with an applied stress state of 1950 MPa. The speckle pattern seen allows a software to track movement of the bar as it deforms (strains) between different pictures. The software tracks tiny patches. Think of them loke a box. The software can then be used to tell the user how much these patches move between the images.
Digital image correlation is an excellent strain measurement technology. This figure shows two images taken using image correlation techniques on a piece of prestressing steel. The top image illustrates time zero with an applied stress of zero. The second photo below shows the specimen at 100 seconds, with an applied stress state of 1950 MPa. The speckle pattern seen allows a software to track movement of the bar as it deforms (strains) between different pictures. The software tracks tiny patches. Think of them loke a box. The software can then be used to tell the user how much these patches move between the images.

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Steel Stub Column Undergrad Lab

We did a very ad hoc style image correlation test using a steel stub column in the undergrad labs. Though not really an accurate way to adhere image correlation paint though, however; it was a good illustration of observing yielding and buckling effects on the column as the test progressed. Images in this video were taken at 1 second intervals, and the video represents 100s of image put together. Images were taken using a Canon 5d Mark 3.

Hauntings and the Denver Equitable Building

The Denver fire tests can be considered first attempt at ‘organised’ floor tests in North America, however; their modern legacy are for the building they supported and the ghost stories it tells today
The Denver fire tests can be considered first attempt at ‘organised’ floor tests in North America, however; their modern legacy is also for the building they supported and the ghost stories it tells today.

The Denver Fire tests of 1890 were revolutionary to the practice of fire safety engineering. The tests were performed under direction of architectural firm, Andrews, Jaques and Rantoul. The objective was to compare three allegedly ‘fire-proof’ flooring arch systems which had been proposed for the Denver Equitable Building through a competitive bid process. For the building contract, the Pioneer fire proof construction company had the lowest bid. The Wight Fire proof company bid slightly more. These companies proposed similar structural systems of floor arches of dense fire-clay. Thomas Lee, who bid the highest for the building contract, proposed an arched system of  porous terra-cotta structural system (see the below floor configurations). Lee realized he out bid

Three competing floor arch systems for the Denver Equitable Building
Three competing floor arch systems for the Denver Equitable Building. Lees system differed to the other proposed systems. These differences included: the orientation of the arch; the choice of material; and the configuration of the the tile itself.

his competitors, but also feeling his product much more superior in fire he asked the architects to consider comparative testing of all three proposed flooring systems. The architects and building owner agreed on the provision that all three companies were willing to participate. The three companies agreed to the terms and the architectural firm drafted a testing schedule of: A still load test- increasing until failure of the arch system; shock (impact) loading repeating until failure; Fire and water test alternating until failure; and continuous heating of “high heat” until failure. After testing, the architects came to the conclusion, that although Thomas Lee out bid his competitors his flooring system had out performed those of his competitors in this test series.

Today, we consider these tests revolutionary in the advancement of our fire science field by motivating progress towards organized fire testing of building materials. The building that inspired these tests, the Denver Equitable Building was built shortly after that test series and still stands today.  The building even survived a major fire in the 1930s. However, the occupants of the building have different stories to tell. Stories of a more ‘spookish’ nature. Fittingly for Halloween it is appropriate to share these.

The Denver tests were photographed. In this photo you can see the ghostly camera effect of the man in the black suit. Because images needed time to develop, he inspects the first beam then proceeds to the next; the picture is not done processing so it appears like a ghost is captured in the photo
The Denver tests were photographed. In this photo you can see the ghostly camera effect of the man in the black suit. Photography in the 1800s needed time to develop images. The photo shows the man inspecting the first floor then in the same image you can see he proceeds to the next. The picture though appears like a ghost is captured in the photo.

After publishing earlier on this topic on the Edinburgh Fire Research Blog in 2012, I was alerted to the writings of Kathleen Barlow on the Denver Equitable Building. Kathleen’s article, Spirits and Scandals tells of several ghost stories related to the Denver Equitable Building. She writes of two crimes of passion conducted by two jealous husbands on two separate occasions at the building site. Also recounted are tales how an individual died in the building shortly after constructed, and how a janitor, Andrew Anderson, fell to his death washing windows from the ninth floor. These aren’t the ghost stories though they may explain them. Today, she reports the occupiers of the building occasionally report the smell of aftershave in areas of the building. A person could be sitting there move a few metres and the smell would disappear. Some claim the smell to be from the deceased janitor of the building. Others report that when they speak ill things of the building strange events happen to them and their possessions. And the most spooky of all, stories of figures that resemble people that vanish. Usually when asked who they were and what they were doing in the building, they disappear. Yet one figure did not; a women who entered the building early one morning saw a man in very classical overall garments cleaning the halls. The man looked at her and spoke “you shouldn’t be here so early. Don’t you know the building is haunted.” When she contacted the company responsible for cleaning, they informed her that they had no one working there that morning, and certainly no one fitting the description she provided….

These old buildings have history to tell. Some scientific, some not so. But still interestingly enough for a scare on Halloween.