Mass Timber And Tall Wood Buildings
Picture of a tall wood building in Norway
Tall buildings made of the traditional materials of steel and concrete have been sculpting metropolitan skylines for more than a century. These materials have exceptional structural qualities and have been used for the construction of towering buildings. The possibilities of concrete and steel have been thoroughly investigated by architects and engineers, who have also gained a thorough grasp of how well they operate in a range of situations, including those with strong seismic and wind loads.
These materials have made it possible for skyscrapers to reach vast heights and be continuously pushed around the globe. Over the past century, both the fire protection of these materials and our understanding of how to adequately secure a building, its occupants, and fire fighters in the event of a fire have considerably improved. There is a new perspective today that questions these two traditional materials and wonders if there are any alternatives that might have less of an influence on climate change.
Up until recently, mid-rise and big structures simply didn't require any new structural innovations. The effects of climate change make it necessary to explore for alternatives to steel and concrete. The use of wood will play a key role in the solution.
New mass timber building materials and modernized design rules have opened up a world of tall wood building potential. Since the early 1900s, large wooden constructions up to nine storeys tall have been built, but by the middle of the 20th century reinforced concrete and steel had replaced wood as the preferred material for tall structures until now. Tall wood structures used for residential, commercial, and institutional reasons are changing skylines all over the world and providing a more environmentally friendly option than conventional building materials.
Tall Wood Buildings
A tall wood building is one that has more than six stories and uses mass timber materials as a useful part of its structural support system. Modern mass timber products like glued-laminated timber (glulam), cross-laminated timber (CLT), and structural composite lumber (SCL) make it possible and even practical to build tall structures out of wood.
Advantages of Tall Wood Buildings
Reduction of Green House Gases(GHG)
Wood structures dramatically lower greenhouse gas (GHG) emissions compared to standard building materials, helping to meet Carbon dioxide reduction goals. Tall wood structures are also a part of a renewable carbon cycle, which is an advantage.
Economical Nature
The circular economy model, which encourages the use of recycled, repaired, and reused materials, includes wood products.
Durability And Ease of Construction
The cost of building tall using wood is decreasing, and tall wood buildings can be constructed with lifespans that are comparable to those of steel and concrete structures.
The construction industry is gradually adopting the design for flexibility and disassembly method of building, which is utilized to lessen waste and consumption’s negative environmental effects. Wood construction lends itself to that strategy. The construction sites use prefabricated, precut, and predrilled elements that are subsequently welded and screwed together. The order of disassembly makes it simple to reverse it, allowing individuals to reuse the wood.
Some other benefits of tall wood building’s include:
The capacity to construct higher structures in regions with weak soils since the superstructure and foundations are lighter than other types of construction.
Building on-site is quieter, which means workers are not subjected to loud noises and neighbors are less likely to complain.
Working off huge mass timber floor plates can increase worker safety during construction.
Construction time can be shortened by using prefabricated parts with exacting specifications.
Design Considerations For The Construction of Tall Wood Buildings
Tall wood buildings should take into account the following design criteria: integrated design, authorizations and construction technique, differential shrinkage between different materials, acoustic performance, behavior under wind and seismic loads, fire performance, service life, and construction planning to minimize exposure of wood to the elements.
Ensuring that a mass wood supplier is involved early on is crucial because they may offer design support services that can further cut manufacturing costs by optimizing the overall building system rather than just individual components. The cost and time of erection can be affected by even small adjustments in connection designs. Mechanical and electrical trades should also be invited early on in the project to participate in a design-assist capacity. This enables a more thorough virtual model, more prefabrication options, and quicker installation.
Basic Components of Wooden Buildings
Studs
The vertical wooden elements of the walls are known as studs.
Joists
The wooden horizontal beams that hold up the floors are called joists.
Rafters
The wood beams that support the roof’s slope are referred to as rafters.
Sheating
Sheathing refers to the sheets that are fastened over the studs in order to join them firmly and create the wall surfaces.
Siding
The outside cladding that encircles the walls from the outside is known as siding.
Construction Materials Used For Tall Wood Buildings
Listed below are some of the structural materials used for the construction of tall wood buildings. They are:
Mass Timber
Structural Composite Lumber
Heavy Timber
Timber Concrete Composites
Mass Timber
A brand-new category of wood products called mass timber has the potential to revolutionize American building. It is extremely strong and stable since it is constructed of many solid wood panels that have been glued or nailed together. It provides a reliable, low-carbon alternative to concrete and steel. Greater areas for us to live and work are now possible thanks to new code amendments that were authorized for the 2021 code cycle and allow mass timber structures to be up to 18 stories tall.
Mass timber construction employs enormous, solid wood panels, columns, or beams that are usually manufactured off-site for the construction of load-bearing walls, floors, and roofs, in contrast to light-frame wood structure, which uses large, solid wood panels, columns, or beams.
Mass timber is significantly lighter than concrete and steel and is built for high strength ratings. Mass timber products, which are constructed of thick layers of wood that are robust, load-bearing structural sections, can be used to create panelized components. To form them, fasteners, adhesives, or lamination are typically utilized. Mass timber is a more environmentally friendly alternative to carbon-intensive building materials and technology and may supplement light-frame and hybrid options.
Mass Timber Products
Today’s market is flooded with mass timber items, each of which employs a distinctive technique to transform little pieces of wood into a robust, sturdy item. The following goods are currently utilized in mass timber construction the most frequently.
Cross Laminated Timber(CLT)
One of the materials that is most frequently utilized in mass wood construction is cross-laminated timber (CLT). Layers of wood are stacked perpendicular to each other to create CLT panels, which are joined together with a powerful glue. The alternating grain structure of the planks makes them stronger and more durable than conventional boards, and any knots or other flaws in the wood are eliminated before manufacturing. CLT is used for ground covering at construction sites; floors, walls and roofing.
Nail Laminated Timber (NLT)
Similar to CLT, nails are used to affix several layers of wood together to create a huge panel or beam. Instead of stacking the layers perpendicularly, the wood is fastened together with nails rather than adhesive. NLT panels can be put together on or close to the construction site because they don’t need to be made in a factory. Nail Laminated Timber (NLT) is used for floors, roof and other horizontal surfaces.
Dowel Laminated Timber (DLT)
The only mass timber product available that is made entirely of wood is dowel-laminated timber (DLT). It doesn’t need chemical adhesives, and wooden dowels are used to join the layers rather than nails. Because of this, it is a well-liked option for producers that want to cut panels into visually beautiful or acoustically pleasant forms without having to worry about ruining their cutting tools on nails. DLT is used for floors, roofs as well as acoustics.
Glue Laminated Timber (GLT)
Similar to CLT, glue-laminated timber (GLT) is constructed from several layers of wood bonded together using powerful adhesives. GLT is frequently used to support panels created from other timber products since the pieces can be placed parallel to one another to form beams and vertical columns. GLTs are mainly used as columns and beams.
Structural Composite Lumber
A class of engineered wood products known as structural composite lumber (SCL) is made by layering dried and graded wood veneers, strands, or flakes with moisture-resistant adhesive into material blocks known as billets, which are then resawn into certain sizes.
Structural Composite Lumber Products
Laminated veneer lumber (LVL)
Laminated veneer lumber (LVL) is a type of SCL that is created by laminating graded and dried wood veneers with moisture-resistant adhesive into billets that are subsequently resawn into desired sizes. It frequently appears in uses including edge-forming material, headers, beams, rails, and rim boards. It can also be used for decking on roofs, floors, and walls.
Laminated Strand Lumber (LSL)
Laminated strand lumber (LSL) is a kind of SCL that is constructed from soft wood or wood strands that are pressure-bonded together using a water-resistant glue and then fabricated into uniform shapes that provide strength and stiffness. Walls, floors, door cores, sill plates and support beams are frequently made of LSL.
Oriented Strand Lumber (OSL)
Made from shorter flaked wood strands than LSL, OSL is a similar product to LSL. The strands are aligned, made into a sizable billet or mat using an adhesive, and then pressed. OSL looks similar to oriented strand board (OSB) since both are made from the same wood species and contain flaking wood strands, however in OSL the strands are organized parallel to the longitudinal axis of the member, unlike OSB.
Parallel Strand Lumber (PSL)
PSL (parallel strand lumber) is a type of SCL made from longer flaking wood strands than those used to make LSL. Using a waterproof adhesive, these strands are then assembled into a big billet, which is then dried to produce engineered wood that is uniform in appearance. PSL can be utilized in columns, lintels, beams, and headers.
Heavy Timber
Solid sawn lumber is referred to as “heavy timber.”
Timber Concrete Composites
Timber concrete composites (TCC) are a hybrid system that structurally joins wood and concrete. Connectors might be custom-made, exclusive, or made by drilling screws into the concrete and lumber. TCC can be applied to floor panels to expand spans or decrease cross-sections.
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