For more than a century, the country most vulnerable to earthquakes in the world, and one with a high level of timber use in construction, has been working to make its buildings more resilient.
Although earthquakes are an extremely rare occurrence in Northern Europe and the Baltics, various aspects of how timber is used in construction elsewhere are very interesting and important for promoting the popularity of this modern, multifunctional material here too. In Latvia, which we often call a “forestry and wood industry superpower”, we still see no widespread use of timber in building construction with state and municipal backing — only isolated “success stories” and “awards of the year”, which is very, very far from enough. Positive experience of innovative and successful applications of timber in construction also has a crucial part to play in today's conditions in meeting the environmental policy targets we have set ourselves.
Tokyo was recently shaken by yet another earthquake – one of hundreds of earthquakes to strike Japan this year. As we may recall, on New Year's Eve last year a magnitude 7.5 earthquake struck central Japan, prompting the country's first tsunami warning since the so-called Tohoku “nuclear accident” of 2011.
The strongest earthquake in Japan in recent decades destroyed buildings, started fires and cut off vital infrastructure on the Noto Peninsula while families were celebrating New Year's Day. Yet despite a series of earthquakes and aftershocks, Japan has coped with the problem far better than, for example, Turkey. There, a magnitude 7.8 earthquake in February 2023 caused extraordinarily heavy losses and an enormous number of deaths. Japan's success in reducing earthquake damage is largely explained by the resistance of its buildings to structural collapse.
A lesson for the future
For more than a century Japan has been at the forefront of seismic architecture and structural engineering, changing its building regulations to reduce the risks posed by thousands of earthquakes every year. Japan has adapted its structural standards, turning past disasters into hard lessons for the future. Timber structural design has come to the fore in Japanese building practice.
In February the publication Wood Central interviewed Japanese Lumber director Graeme Sayer, who said that other countries could learn a great deal from the Japanese about using timber so that buildings withstand earthquakes and other natural disasters. Japan has built mainly wooden buildings for centuries, adapting them to the conditions at hand.
“The culture of timber construction is bound up with the fact that brick was only introduced as a material in Japan around 1860, when builders arrived from Germany,” Sayer stressed. The Japanese Lumber director was born in New Zealand and has close ties with sawmills and traders across the country. Graeme Sayer stresses that Japan “is not a civilisation built on brick (or stone), as the cultures of many European countries are.”
From a policy point of view, the change began in 1923, when a magnitude 7.9 earthquake razed Yokohama to the ground, killing more than 140,000 people and destroying hundreds of thousands of buildings. Many of Japan's ancient timber buildings were not suited to frequent earthquakes. That tragedy allowed Japan to introduce the world's strictest and most modern seismic standards into its building regulations, now known as the Building Standards Act. These standards underpinned the use of new and existing timber and concrete structures, particularly in heavily urbanised districts such as central Tokyo.
In Japan, one of the world's largest consumers of timber, the rule is that “buildings must not collapse during an earthquake, whatever damage they suffer”, including detached houses, which since 1981 have had to be built so as to “ensure sustainable human life” during an earthquake.
Timber Engineering Research examines seismic protection technologies
Japan is now turning to taller mass timber buildings in order to advance decarbonisation, and seismic protection technologies (SPTS) have become a pressing question in timber engineering research. They include seismic dampers and base isolation, described as the “Cadillac of performance options for protecting buildings in areas of high seismic activity”, according to California-based structural engineer Krista Looza, who highlights the resilience of Japan's timber buildings to violent shaking. “There are almost three times as many earthquakes there as in California, which is itself considered a region of high seismic activity. So you can imagine just how well prepared people in Japan are, aware of the hazards they live with.”
As Architecture Digest writes, seismic dampers are placed between the columns and beams of each storey of a building and use piston heads in silicone oil cylinders so that, during an earthquake, vibrations are transferred to the fluid rather than to the structure. Base isolation comes in various forms and at various prices, from rubber “pads” installed at the building's foundations that act as shock absorbers, through to detaching the whole structure from its foundations and mounting it on a flexible bearing so that, as the ground shakes, the building's structure remains intact and stable.
The most economical way of protecting a structure from cracking and collapse is to reinforce it, making walls, columns and beams thicker so that they better withstand the loads during a natural disaster. When a building is being constructed, architects can opt for precast concrete walls, which help absorb lateral loads, or steel moment frames, to build support directly into the structure.
Reinforced concrete and structural steel reinforcement are the standard of the modern construction industry. These materials were long considered a better choice than timber, yet the US Forest Service has recently demonstrated that cross-laminated timber (CLT), for example, is resistant to lateral pressure, which led to changes in the building code approving the use of CLT structures in seismically active zones.
An earthquake simulator – the “shake table”
In California, which also has high seismic activity, researchers are using an earthquake simulator, or shake table, to test a ten-storey cross-laminated timber building at the University of California San Diego. Science Blog reported earlier that this experiment, known as the TallWood Project, involves the tallest timber building ever tested on an earthquake simulator.
Using this earthquake simulator, quakes of varying strength on the Richter scale can be reproduced – from magnitude 4 to 8 – replicating the seismic activity of earlier earthquakes, including the Northridge earthquake that struck Los Angeles in 1994.
“The combination of the world's largest payload capacity, an outdoor setting and the recently added six-degrees-of-freedom earthquake capability makes the UC San Diego earthquake simulator a powerful and unique facility,” said Joel Conte, a professor at UC San Diego's Jacobs School of Engineering and chair of the Department of Structural Engineering in the university's engineering faculty. “It is the only place where the TallWood project's tests could be carried out,” Professor Conte stressed.
Mass timber buildings are becoming ever more popular as greener and faster alternatives to concrete and steel structures – among them the 11-storey Port Plus building erected in Tokyo last year. Given the new building regulations allowing more high-rises to be built from mass timber, questions arise as to how such buildings will withstand earthquakes.
“Mass timber is part of a major trend in architecture and construction, but the seismic performance of tall buildings constructed with these new systems is not as well understood,” said lead researcher Shiling Pei, associate professor of civil and environmental engineering at the Colorado School of Mines.
Japanese engineers maintain that preparing in advance is the best way to counter the potentially lethal consequences of an earthquake. After every earthquake, Japanese scientists inspect buildings to find out where they are structurally deficient. That knowledge helps ensure that the impact of each successive earthquake is less devastating than the last.