Getting nostalgic about the future for wood

Published: 22/06/2016 00:00

Matt Collins, Sales Director at Metsä Wood, explains why the engineered timber specialist's "reimagining" of some iconic buildings from the past has resonated so strongly with the contemporary design community, as well as the reasons its high performance, sustainable systems are increasing their share of the construction market.

It is a characteristic of mankind that we are fascinated by the lives of our ancestors, right back to the times of the early cave dwellers and hunter-gatherers. Archaeologists research what they ate and wore, as well as the tools they made and the shelters which prehistoric man fashioned from the materials available.  

Museums across the globe are full of fascinating artefacts, but often of even greater interest are the early structures that remain: famous heritage sites such as the Colosseum in Rome. Tourists visit the ruins in their thousands throughout the year, listening to guides recounting stories of how the gladiators fought to entertain the crowds, and to wonder at the scale of the place.  

Archaeologists and academics are also keen to rediscover the skills of the ancients – from 'napping' flints to firing pots – but suppose we wanted to look again at the way they had set about their most iconic building projects; or even consider ways of providing a modern interpretation.     

The challenge of reimagining these great structures from the past, re-engineered to take advantage of todays most advanced and sustainable building systems, is the task that has been set for some of the world's most notable design professionals by a major international timber engineering specialist.   

Historians have expended a lot of time and energy pondering how ancient structures such as the pyramids and Stonehenge were built, without the use of cranes or other heavy lifting and cutting equipment. Through its project simply named 'Plan B', Metsä Wood has now enabled some internationally renowned consultants to explore how three very different edifices might have been improved upon, and there is more to come.  

Furthermore, to share these fresh insights into how these wonders – wrought from stone and then steel – could be redesigned and enhanced thanks to modern timber technologies, Metsä Wood has made the visualisations available through a new microsite -> planb.metsawood.com. It gives access to a plethora of plans and technical information stretching from the original concepts, through to 3D models.  

CASE 1: THE ROMAN COLOSSEUM

As one of the most recognisable ruins remaining from the time of the Romans, the Colosseum is both vast and the subject of interest from historians conjecturing over the way the spaces functioned; and aspects such as what sort of roof or canopy it might have featured.  

The Plan B project team elected to work with Antti Laiho from Finnish based Helin & Co Architects to try and create a contemporary visualisation of how it might look and function if it had been built using modern timber systems. In essence: to produce a recognisable replacement, which relies on wood as its main raw material rather than stone.  

 

Also emphasising the reduction of waste and compressing the construction time required, as well as cutting overall cost, the decision was taken to base the redesign on the use of laminated veneered lumber for the columns and beams. This product not only being highly sustainable, but offering great load-carrying capacity: providing tensile and torsional strength in addition to compressive strength.  

The process was started by utilising a satellite image of the Colosseum to pinpoint all of the salient details on a scaled grid of the site. More information was also abstracted from existing cross-sections and detail drawings of the various elements.   

The next step was to identify relevant loading values for the structure and the crowds which massed there during events, in order to complete a proper structural analysis upon which new designs could be based. 

The design team assumed that people would be packed onto the terraces and other viewing areas at a density of four persons per square metre: taken as an equivalent load of 400 kg or 4 kN per square metre. An additional 2 kN was calculated for the structure itself: relating to a seven metre span beam typically weighing 500 kg plus the floor elements, at 1000 kg each. The new timber columns, at 15 metres in height, would weigh some three tonnes.  

A maintenance load of 0.4 kN was added to the dead load and, along with the relevant spans or other dimensions, input into AutoCAD; while the designers further made use of Finnwood and Tekla software.   

The LVL elements were, not surprisingly, shown to be well able to accommodate such load conditions – being at some 60% of the ultimate limit state - and it was the need to control low frequency vibration in the structure which dictated many of the beam sizes. The Finnish standard adopted set a maximum frequency of 9 Hz. The maximum deflection allowed was 0.5 mm for a load of 1 kN at the centre of span. 

Antti Laiho asserted: "At 190 metres by 158 metres, the Colosseum is a huge building – almost three times the size of an average sports arena. Initially, I thought that wooden construction to such an extent wouldn't be feasible in reality. As the project proceeded, I changed my mind. It would not only be possible, but easy as well."  

 

 

The renowned architect worked with Metsä Wood's structural engineer, Jussi Bjorman, to produce a new structural solution employing various LVL products in order to recreate the Colosseum's distinctive elliptical form, as well as its arrangement of columns, arches and beams. Crucially though, the offsite fabricated laminated elements would be erected far faster and more cost effectively than the large masonry vaults.  

Interestingly, the concept of substituting LVL for massive masonry forms would not only allow larger spans while maintaining such physical qualities as loadbearing capacity and fire resistance, but it would also create 12% additional space in the vaults below the seating arena. This could, for example, now potentially accommodate VIP facilities and retail outlets. It is also certain that health and safety standards would be unrecognisable from the workplace of 72 AD. 

EMPIRE STATE BUILDING GETS PLAN B TREATMENT

After the success of the Colosseum exercise, Metsä Wood identified a truly outstanding 20th century property to be given the Plan B treatment.  

Some of the film footage that survives of erecting the Empire State Building back in the late twenties (it was completed in 1931) is hair-raising in its own right: with the spider-men stepping from one moving girder to another, hundreds of feet above the street.  

 

Almost a century ago, the construction method was viewed as dynamic and cost effective, but for this second re-imagination, Metsä Wood recruited Michael Green of architects MGA and timber specialist, Equilibrium Consulting, to determine if it could stand just as tall in LVL; while also exploring other aspects of the Manhattan skyscraper's specification.  

Once again, the expert use of modern structural analytical techniques and the different software packages enabled the highly experienced project team to extract the ultimate in potential from LVL: optimising section sizes, reducing weight compared to the hot rolled steel I-beams of 80 years ago, and accelerating the programme times. 

Michael Green confirmed: "I believe that the future belongs to tall wooden buildings. Significant advancements in engineered wood and mass timber products have created a new vision for what is possible for safe, tall, urban wood buildings. The challenge now is to change society's perception of what's possible." 

Significantly, the third in the Plan B series has been the seat of the German parliament, the Reichstag: where much of the debate concerns environmental legislation. This project has involved FH Finnholz, a leading German construction company, and its engineer Andreas Rutschmann; with the iconic domed roof offering one of the main technical challenges.    

 

So how do the Plan B re-imaginings of the Empire State Building and other structures resonate with and empower the architects and engineers confronted by the challenges set by today's client aspirations, codes of practice, price constraints and other issues? 

Modern Methods of Construction

It is now widely accepted, including in Government circles, that Modern Methods of Construction (MMC) and especially offsite fabrication are crucial to the UK building sector increasing its capacity; and being able to meet such challenges as providing sufficient housing to accommodate a rapidly growing population.  

Compared to traditional construction methods, factory fabrication offers many advantages, with the workforce having dry and comfortable conditions which help achieve higher productivity levels; while they are also far less at risk of accident or injury. Their output is also acknowledged as being of a higher quality, while what is often a repetitive and highly mechanised process is also much more accurate.    

Importantly, offsite manufacturing is helping offset the constraints affecting the wider construction market, caused by the shortage of traditional skills after the recession.   

Although offsite takes many forms, timber based systems dominate in terms of both volume and value within residential development, where the big housebuilders are at last coming to understand the full benefits. In other sectors also – such as education, commercial, retail and hospitals – engineered timber is increasing its market share, and being seen as the sustainable answer.  

Unlike steel, aluminium and cement or concrete based alternatives, engineered timber systems involve very low embodied energy within their production cycles. In the case of LVL, not only does the majority of the raw material come from sustainable, well-managed forests offering a fully certified and traceable chain of custody, but also where slow grown timber from northern latitudes is employed, it provides enhanced strength and durability.  

The ultra slim sections of timber which go to make up the various laminated veneered elements that comprise each structure lock in carbon for the life of the building and beyond, while providing totally predictable performance.  

With sawn timber, disconformities such as knots, shakes and splits represent weaknesses, and can compromise the overall performance of a section. For the production of LVL the round wood is cut into 3 mm laminates and exposed to detailed automated examination so that unsuitable material is rejected. The laminates are then re-oriented and glued before being subject to high pressure; forming a composite where the effect of knots and other irregularities is greatly reduced.  

The resulting load-bearing capacity far exceeds that of solid timber beams and columns, while such problems as dimensional stability and susceptibility to moisture are ruled out. Structural engineers are therefore able to design even multi-storey properties, knowing exactly how every element or component will behave.  

For instance, the shrinkage that affects traditional timber frames and that typically discouraged designers from considering them for buildings of more than four to five storeys, are much less of a concern.  

The fire resistance of engineered timber structures is also noticeably superior to that of traditional timber frame methods, making them far safer; not just during the service life of a building, but also during the vulnerable build phase.  The multi-layered but essentially homogenous make up of LVL offers heat and flames far less surface striations to attack: and this limits the charring rate for the material to just 0.7 mm per minute. In the absence of any other source of fire or accelerants, LVL will tend to self-extinguish, with very limited tendency for the surface spread of flame. 

The designer is therefore at liberty to expose and express the elegance of the timber structure and the beauty of the wood itself, rather than rushing to protect it with fire boarding or heavy sprayed intumescent coatings as they would in the case of sawn timber, or even steelwork. This resistance to fire is effectively endorsed by the extensive use of LVL and cross-laminated timber (CLT) for education projects across the UK. 

The many advantages of LVL for forming complex arrangements of columns and beams – including flexibility of design and buildability – can be continued on through the building, with the engineered timber manufacturing industry also producing advanced solutions for both walling and flooring applications.  

These similarly combine the benefits of responsibly produced timber as an environmentally friendly raw material, with those of factory prefabrication, to enhance the build process. Their quality and dimensional accuracy can further facilitate the completion of a much more airtight, fabric first building envelope which is far less reliant on the post-erection installation of tapes, membranes and mastic sealants. Therefore, the energy performance of both domestic and non-domestic properties can be brought down to within the parameters of the PassivHaus standard or other near-to-zero carbon designs. 

BIM

While in the UK the Government is widely regarded to be driving the agenda for the uptake of Building Information Modelling (BIM) due to making its use mandatory at Level II for new public sector projects, many manufacturers who operate abroad had embraced the technology some years ago. Specifiers will therefore be pleased to know that most contemporary engineered timber components and systems are available to download as BIM components or objects. You can view Metsä Wood's range of BIM components here -> BIM components.

Importantly BIM not only has the potential to inform the design process and make manufacture more efficient, it can also radically influence construction management, project management and cost control. This in sequence stretches right through to the future facilities management of properties; making them far more economic to operate and own throughout the lifetime of the building.  

Properly incorporated into the design, manufacture and erection process, BIM represents a truly holistic advancement for the future of construction and a process to which leading manufacturers are fully committed. In the production process, BIM facilitates the generation of precise cutting schedules and reducing waste, while the technology has also been shown to help avoid 'clashes' between, for instance, structural components and building services.   

Accordingly recognised for the proven benefits of sustainable production based on well managed sources – with certified chain of custody – state-of-the-art design support and innovative manufacturing techniques delivering high quality components on schedule, engineered timber systems have earned inclusion for some of the most architecturally acclaimed projects of recent times.  

For example the iconic Metropol Parasol in Seville represents one of the largest timber constructions in the world and also happens to be one of the most sustainable – being that it has been manufactured using a 100 per cent traceable wood value chain, from sapling to product. 

Click here for more information on the Metropol Parasol.

Constructed from 3,400 individual timber elements and employing 3,000 load-bearing connection nodes, the structure creates an urban space within the medieval inner city of Seville. Its stunning, curving and twisting parasols feature wood elements of up to 16.5 metres in length with thicknesses ranging from 68–311 mm; protecting the people under it from the often-fierce heat of the sun over the city.  

According to the German architect Jürgen Mayer H. who designed it, "Metropol Parasol has 'revitalised' the Plaza de la Encarnacion to become the new, contemporary urban centre. Its role as a unique urban space within the dense fabric allows for a great variety of activities such as history, leisure and commerce. Its highly developed infrastructure has fashioned the square into an attractive destination for tourists and locals alike." 

The Metropol Parasol additionally houses an archaeological museum, a farmers market, an elevated plaza, multiple bars and restaurants both beneath and inside the parasols – or 'mushrooms' as some have described them. Plus there is as a panoramic terrace on the very top of the four floors; accessed via the 'stems' to the mushrooms which contain stairs and lifts. 

Comprising six parasols, the design was inspired by the vaults of the city's cathedral and the Ficus trees in the nearby Plaza de Cristo de Burgos – indeed, the structure is organic in appearance, projecting a sense of fluidity and movement.    

The whole structure is approximately 50m long, 75m wide and 28m high. As with some other free-flowing, organic designs that have been created elsewhere using engineered timber solutions, the individual elements – in this case formed from laminated veneered lumber – have been arranged in an orthogonal grid pattern.  

The architect confirmed that only an engineered timber system would be suitable for the construction of such large and complex structures as the Metropol Parasol due to their excellent strength-to-weight ratio. LVL in particular is proven as an incredibly strong yet light and ultimately versatile building material. For the parasols, a plant in Germany produced a total volume of approximately 2,500 cubic metres of parallel laminated veneer lumber. Then the wooden structure is covered by 2-C Polyurethan varnish to protect the elements against the weather. 

The design process was further facilitated through the intense electronic exchange of data between all parties in the planning process as an essential element to the development and construction of Metropol Parasol. The data generated by the architectural model was directly integrated into the programs of the internationally acclaimed engineers, Arup, and the construction company.  

CONCLUSION

Wood was prehistoric man's most accessible, flexible and plentiful building material, with the strength to create defensible structures as well as rudimentary shelters.  

Looking back over the UK and the world's built environment, the material is also very widely and articulately represented as a key element to some of the most striking buildings: from the magnificent hammer beam roof of Westminster's great hall to some of the present day's most inspired architectural creations.      

We have also seen within the scope of this article how contemporary timber technology could be employed to reengineer and even improve upon iconic buildings from history. For timber is not only a highly aesthetic and sustainable raw material that is constantly being replanted and regenerated, but one with the potential to create more energy efficient, faster to construct and highly durable structures.  

Thanks to engineered timber's combination of lightness, strength and flexibility, it offers the opportunity to create longer spans with lower imposed loads on foundations or sub-structures. In fact, many leading architects and structural engineers are now of the opinion that engineered timber solutions offer the ideal option for creating the rapid build, high rise properties which our ever expanding urban populations require to accommodate businesses as well as families.  

Recent years have already seen real progress in the development of better and more efficient systems from leading manufacturers like Metsä Wood, with substantial investment in research helping bring new ones to the market.  

It is reasonable to conclude that with the design guidance and support available to project teams across all the construction sectors, the only limitations on the use of timber are the client's own imagination.