Rethinking on Timber Structures

Wood is an organic-based building material with a fibrous texture obtained from a living organism, the tree. Humanity has been using wood as one of the oldest building materials for shelter and protection since ancient times. Today, the use of wood as a structural element in buildings, especially in cities, has remained quite limited.

One of the biggest psychological barriers to the use of wood as a structural element (1) is the concern about the flammability of wood in case of fire. However, precisely because of these prejudices, in order to rethink wood, in this article we will take a closer look at the structure of wood and consider the perspectives on its use in our country and in the world.

Although wood is unlikely to be seen as an alternative in structural system designs in our country, there are many examples, including high-rise buildings, where wood is used as a structural system in many parts of the world (2). Examining these examples is of great importance in order to see what wood can do when used correctly (a, b, c, d).

Despite the psychological barriers we have today, it is seen that wooden structures are preferred in the light of the lessons learned and knowledge gained after many earthquakes in the past of Istanbul, which has witnessed countless earthquakes in history. For example, after the Great Istanbul Earthquake of 1509, Architect Hayrettin, who was also the master of Architect Sinan, realized that wood was more resistant to earthquakes than other building elements, and the sultan issued an edict that all buildings to be built in the capital should be made of wood-framed materials (3).

In other earthquakes in Istanbul's history, it was determined that wooden buildings suffered much less damage than other buildings in earthquakes and this was seen as the main reason for the low loss of life (4). Thus, most of the masonry buildings destroyed in the May 22, 1766 earthquake are rebuilt in wood. Although the state did not want to build wooden buildings due to the risk of fire, the people preferred wood, despite the high risk of fire in wooden buildings under the conditions of that time (5). Today, with the current technology, wood is becoming much more suitable against such risks in terms of both earthquake and fire.

One of the advantages of wood is that it is 5 times lighter than concrete and 15 times lighter than steel. Thanks to its physical advantages, it can pass through wide openings, has a high load-bearing capacity and is energy-friendly in terms of thermal insulation as a sustainable material (6). Thanks to this feature, it can maintain its load-bearing properties longer than steel and concrete in case of fire.

In order to understand the behavior of wood in case of fire, it is necessary to look at its chemical properties. First of all, a fire needs oxygen to continue (7). Wood materials, on the other hand, remove the oxygen from the carbon dioxide in the air and keep the carbon in its body. In case of fire, it can survive longer than other materials because it releases the oxygen in its own structure. Despite the explosion risk of concrete and the rapid melting of steel, wood provides an important advantage at this point by providing the necessary time to evacuate the building.

When wood burns, the carbon around it provides thermal insulation. Therefore, as in the image below, we can see that while the steel materials melt after the fire, the wood continues its carrier.

The Difference Between Steel and Wood After Fire - Prof. Dr. Ahmet Türer TED Speech (8)

Of course, focusing on the advantages of one material while declaring others guilty or leaving them completely in the background would be to ignore the unique characteristics of each material. Regardless of the material, in order to use the right method at the point of design and application, it is necessary to understand the language of the material and take all precautions by applying it as required by this method. The real problem is not the material itself; any structure that is not in accordance with the construction technique can cause a disaster. Therefore, while removing some of our psychological barriers, we should always continue to "rethink" in order not to add new ones in their place.

Writer: İlayda Köroğlu
(Architect & Editor)

Sources

1. Woodlife Symposium - Psychological Barriers: Safety and Regulations: https://youtu.be/6k4URyFAM1U 

2. https://www.archdaily.com/996319/the-meteoric-rise-of-cross-laminated-timber-construction-50-projects-that-use-engineered-wood-architecture 

   a.https://www.archdaily.com/794170/worlds-tallest-timber-tower-tops-out-in-vancouver 

   b.https://www.dezeen.com/2020/02/12/france-public-buildings-sustainability-law-50-per-cent-wood/ 

   c.https://www.globalconstructionreview.com/japan-plans-take-timber-high-rise-construction-new/

   d.https://www.archdaily.com/989552/haut-amsterdam-residential-building-team-v-architecture

3. Ali Nusret (17 Ağustos 2021). "İstanbul'un altüst olduğu gün: Küçük Kıyamet Depremi". The Independent. 

4. Sakin, O. (2002). Tarihsel kaynaklara göre İstanbul depremleri (Vol. 173). Kitabevi.

5. Afyoncu, E., Mete, Z., (2000), 1766 İstanbul Depremi ve Toplum Yaşantısını Tesirleri,Tarih Boyunca Anadolu’da Doğal Afetler ve Deprem Semineri, 22-23 Mayıs 2000, İstanbul Üniversitesi Edebiyat Fakültesi Tarih Araştırma Merkezi

6. https://protectaqua.com/Sayfa/1/Ahsap-Nedir-ve-Neden-Tercih-Edilir 

7. ÇANAKÇIOĞLU, H. (1970). Yangın emniyet yolları ve yangın emniyet şeritleri. Journal of the Faculty of Forestry Istanbul University, 122-152.

8. https://www.ted.com/talks/ahmet_turer_medeniyet_muhendisligi?language=tr

Cover image: https://perkinswill.com/project/ubc-gateway/