Manufacture building lumber
United States. Agriculture and Forestry Committee. The subcommittee met, pursuant to adjournment, at Hence there are now seven representatives at work in Scandinavia, whereas before we had only one in Denmark and one in Sweden. Appointments are made from a long list of applicants through one of the most efficient and independent organizations in our entire government machine, the Bureau of Foreign and Domestic Commerce in the Department of Commerce. The candidates are given individual and highly technical examinations, and the selection is made on a basis of education, businessVIDEO ON THE TOPIC: Complete production line for CROSS LAMINATED TIMBER CLT by Ledinek
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This chapter provides information related to commonly used wood construction methods i. It briefly discusses the manufacturing of four major lumber-based mass timber products i.
The discussion also addresses primary lumber products, such as dimension lumber, machine stress-rated lumber, and finger-joined lumber, which are the building blocks from which mass timber products are manufactured. Advantages of using wood in construction are illustrated by examples largely from North American practices.
The life cycle assessment concept is also introduced. Timber Buildings and Sustainability. Prior to the availability of rolled steel and reinforced concrete, wood was the primary structural material in North America and other timber-rich regions of the world [ 1 ].
However, the raw material resources keep changing in more recent times, e. This has permitted economic construction of residential and nonresidential buildings, bridges, and industrial structures. From a technical perspective, modern EWP commonly provide better and more predictable physical and mechanical properties than traditional wood products, such as more uniform structure, greater dimensional stability, greater strength, and stiffness. Initially, much development of EWP was focused on creating substitute products capable of replacing small dimension sawn lumber and boards as primary elements in light-frame building superstructures; but in recent decades, much attention has been switched to creation of mass timber products MTP.
The term MTP describes a family of EWP of large section size that offers the construction industry a viable alternative to use structural steel and reinforced concrete [ 3 ].
SCL refers to products manufactured by layering dried and graded wood veneers or strands bonded together by moisture-resistant adhesive into panel-like products of a width of up to 2. In principle, SCL is only limited in width and length by transportation considerations. Use of terms in the literature can be colloquial, with timber-concrete composite TCC and other hybrid elements sometimes grouped into the meaning of MTP. Overall, MTP offers architects and builders many opportunities to express their concepts creatively, while satisfying various technical performance requirements applicable to engineered structures of many types [ 4 ].
This chapter places emphasis on the types of lumber-based MTP illustrated in Figure 1. Figure 2 illustrates three types of wood construction methods, namely light-frame, post-and-beam, and mass timber. Dimension lumber is used for framing members and plywood or OSB for sheathing materials.
Light-frame construction is an economical choice for the construction of low- and mid-rise buildings, which makes use of dimension lumber in a range of grades and dimensions [ 7 ]. Light-frame wood structures can be also used for shopping centers, plazas, service and maintenance buildings, and institutional and municipal facilities.
Prefabrication of components such as wall and roof panels, even complete homes or office units are efficient extensions of this framing technique [ 7 ]. However, the structural system of a light-frame building is not well-defined, resulting in much redundancy. Design of a light-frame building often only includes architects unless the building is large. Wood building construction methods. Traditionally, posts and beams were made of large solid timbers, which were connected with mortise and tenon joints locked into place with hardwood pegs, with diagonal braces for stabilization of a structure [ 7 ].
The post-and-beam construction is commonly used to construct custom-designed homes, commercial buildings, recreation centers, and industrial structures, for reasons of ease of fabrication and consequent economy [ 7 ]. Unlike the light-frame construction, the structural system of a post-and-beam building is well-defined and engineered, generating very limited or no redundancy.
Design of a post-and-beam building is usually formal, involving both architects and engineers, especially if the building is relatively large. Hybrid post-and-beam and light-frame construction features the exposed heavy timber components, but allows insulation to be placed in the wall space, with finishes applied to both the inner and outer faces of the studs [ 7 ].
Mass timber construction complements traditional light-frame and post-and-beam construction methods due to emergence of various types of MTPs, Figure 2—bottom. It creates single or multiple material hybrid superstructures for building and other structures. Since beams are not always required, new technology and terminology, such as post-and-panel construction, have emerged.
What codes and standards permit architects and engineers to do is not yet uniform; but in the broad sense, construction codes and standards in various countries have transitioned, or are transitioning, away from prescriptive provisions to performance-based provisions in a manner that enables greater use of EWP, including MTP.
Most important in this respect is the revision of fire performance provisions related to buildings [ 4 , 6 ]. Mass timber systems are widely reported to be cost-competitive, carbon-efficient, sustainable and reliable, which stem from the scientific data generated from full-scale fire, seismic, durability, acoustic, and vibration tests being conducted internationally by researchers and engineers [ 3 , 4 ].
It is now reasonable to claim that the use of EWP and MTP has the same level of supporting technical understanding as that underpinning any other major class of construction material. Latter sections of this chapter demonstrate the use of MTP as parts of high-performance buildings meeting needs of society and occupants. Lumber is a manufactured product derived from logs, including boards elements with limited thickness , dimension lumber elements with relatively small section dimensions , and timbers elements with relatively large section dimensions.
Dimension lumber is widely used in light-frame construction, which is categorized into four groups in the Canadian practice: structural light framing, structural joists and planks, light framing, and studs. Dimension lumber is usually graded by visual inspection in terms of appearance characteristics, such as knots and slope of grain. For example, the grades of dimension lumber used for structural light framing construction are Select Structural SS , No.
It should be noted that there is not a strength difference between No. Therefore, the product mix of No. Alternatively, dimension lumber can be mechanically evaluated and sorted into grades using so-called machine stress-rated MSR lumber or machine-evaluated lumber MEL [ 6 ]. The MSR machine is widely used in wood industry to nondestructively test each piece of dimension lumber to determine its stiffness so that it can be assigned a permitted design stress based on the established relationship between the stiffness and bending strength.
Uses of dimension lumber and timbers widely range with differences in whether the former or latter is suitable depending on the type of structural system, and performance requirements applicable to a structural system. In general, dimension lumber is used in systems where multiple parallelly arranged elements act together to resist effects of particular structural design loads.
Timbers, on the other hand, can be used in situations where multiple elements or a single element is designed to resist effects of particular structural design loads. Another important difference is that dimension lumber elements must always be protected from effects of design fire situations; whereas, depending on specifics of a situation, timbers may not require such protection. Finger-joints are commonly used to join short pieces of lumber together to make longer pieces. The joint profile governs the strength of a joint, and is defined by the finger length, tip thickness, tip gap, and finger pitch, slope, and depth.
For example, a mm-long finger joint is commonly used Figure 3—left. Also, it is noted that cutting out strength reducing features like large knots then finger joining lumber is a highly effective way of upgrading properties of dimension lumber, increasing value, and enabling higher value uses like creation of high-performance MTP [ 6 ]. Another advantage of finger joining lumber is that it increases dimensional stability under changing environmental conditions prior to or after installation of lumber in structures.
Adhesives used in finger-joints are usually phenol-resorcinol formaldehyde for lumber products intended for general applications or incorporated in GLT elements, or polyvinyl acetate for lumber products used as studs [ 6 ].
Two finger joint profiles left: mm long; right: mm long used for joining short pieces of lumber. GLT also widely known as glulam is a structural product composed of multiple pieces of finger-joined dimension lumber, or other types of EWP, adhesively face-to-face bonded to create a desired form. GLT was first used in Europe in the early s. A patent from Switzerland signaled the true beginning of GLT construction [ 9 ].
A significant development in the GLT industry was the introduction of fully water-resistant phenol-resorcinol adhesives in , which allowed GLT to be used in exposed exterior environments without concern of glueline degradation [ 9 ].
The manufacturing of GLT is deemed as a one-dimension additive process. The grain of all laminations runs parallel with the lengths of straight members, Figure 4. Each lamination is visually inspected based on both faces of the piece, and then assigned one of four grades: B-F, B, D, or C [ 7 ], in which B-F indicates the highest grade and C the lowest grade.
Laminations of higher grades are used in the top and bottom portions of a GLT beam, Figure 5 , where bending stress is greatest. Specified laminations are also nondestructively graded by machine before assembly to meet both visual and stiffness requirements for particular grades of GLT.
Sometimes layers of other materials, such as glass fibers, are incorporated among lumber laminations to add strength or stiffness or to locally reinforce GLT [ 10 ]. Durable cold-setting waterproof-structural adhesives are used, such as phenol formaldehyde and phenol-resorcinol formaldehyde [ 7 ]. Because finger-joined lumber is employed, dimensions of GLT members are in principle only limited by manufacturing and transportation capabilities of a manufacturer.
Those capabilities are highly variable, with the most advanced involving fully automated manufacturing processes based on advanced integrated design and manufacturing methods. The automated processes can include robot handling of materials and elements from the arrival of logs at a manufacturing plant to installation of elements at a construction site. GLT is commonly used as beams and columns Figure 4—left and middle , but can be also used as flexural members Figure 4—right.
Usually, GLT is used in dry service conditions or is protected in some way if used under outdoor conditions. GLT members with laminations suiting resistance of bending forces: Upper—Member with a balanced layup intended to maximize material use when the member is loaded in tension on both top and bottom faces EX grade under Canadian system , and Lower—Member with an unbalanced layup intended to maximize material use when the member is loaded in tension on the bottom face E grade under Canadian system.
Design stiffness and strength properties of GLT of a given grade are calculated based on engineering properties of the laminations using equivalent linear elastic mechanics theories.
A wide range of GLT grades are available with some involving deliberate placements of laminations of different grades to achieve the design properties of GLT elements suited to their particular applications [ 11 ]. In general, there are two grade categories for GLT, stress grade and appearance grade [ 7 ].
The former defines specified strengths of a GLT member, and the latter the quality of finish on the exposed surfaces of the member. For example, some grades suit uses of GLT elements as beams, columns or tension members, Figures 6 , 7 , 8.
Within those designations, numbers 20 and 24 are indicative of the associated specified design strength in bending. E indicates that associated grade properties apply to elements without an inflection in their deformed shapes, with the proviso faces intended to be stressed in tension are correctly oriented.
EX indicates that associated grade properties apply to elements with inflections in their deformed shapes. Similar approaches are adopted by other international standards which define rules for engineering design of timber structures. Source: Photos obtained from Lefebvre and Richard . NLT is manufactured with dimension lumber laminations, stacked on edges, and fastened with nails, to create large-flat structural components, Figure 9. Spikes and screws are sometimes used as well.
In addition, NLT has been used to create deck and diaphragm elements of bridges and buildings for centuries [ 6 ]. Single laminations are commonly employed if the length of prefabricated panels is less than 6 m [ 14 ].
The spliced laminations of specific pattern [ 11 , 14 ] or finger joined lumber laminations [ 14 ] are used if longer panels are required. For example, mm-long nails should be used to fasten mm-thick laminations, and mm-long nails for mm-thick laminations. Such requirements are based on practical experience and ensure integrity of NLT in various end use situations. The drawbacks of using NLT are its slow fabrication process and after-fabrication machining problem due to existence of nails.
In North America, many timber decks of rural bridges constructed from s through the mids were made of NLT [ 15 ].
Mostly, the NLT was oriented so the lumber laminations were transverse to the bridge span and supported by bridge girders, but for short bridges lumber laminations were sometimes orientated parallel to the span [ 15 ], Figure Another common traditional use of NLT is in floors of industrial and commercial buildings.
The reasons for choosing NLT are as follows: it is well suited to onsite fabrication; it is capable because of the nails of absorbing energy damping vibrations caused by transient or sustained dynamic force e. Disadvantages of NLT include that it is not particularly mechanically efficient if NLT elements are required to have high rigidity when loaded in-plane or as flexural elements, also there have been durability issues associated in particular with bridge applications.
The disadvantages stem from the flexibility of nailed interconnections between laminations, and proneness to gaps to form at those interconnections e. Recently, use of NLT has undergone resurgence as part of the modern mass timber movement in buildings [ 3 , 4 ], Figure
Lumber-Based Mass Timber Products in Construction
Lumber North American English or timber used in the rest of the English-speaking world is a type of wood that has been processed into beams and planks , a stage in the process of wood production. Lumber is mainly used for structural purposes but has many other uses as well. There are two main types of lumber. It may be supplied either rough- sawn , or surfaced on one or more of its faces.
Engineered wood , also called mass timber , composite wood , man-made wood , or manufactured board , includes a range of derivative wood products which are manufactured by binding or fixing the strands, particles, fibres, or veneers or boards of wood, together with adhesives , or other methods of fixation  to form composite material. The panels vary in size but can range upwards of 64 by 8 feet 20m x 2. Engineered wood products are used in a variety of applications, from home construction to commercial buildings to industrial products. Typically, engineered wood products are made from the same hardwoods and softwoods used to manufacture lumber. Sawmill scraps and other wood waste can be used for engineered wood composed of wood particles or fibers, but whole logs are usually used for veneers, such as plywood , MDF or particle board.
Lumber The Traditional House-building Material M ost North American homes today, as in the past, are constructed with wood framing using dimensional lumber. What is Dimensional Lumber? Dimensional lumber is the product of the sawmill where it is mechanically shaped to industry standard dimensions - width, thickness and length. How is Lumber Manufactured? Sawmill operations are varied as they are numerous. Typically, logs are transported to the mill by truck where they are graded for size and suitability for different uses. Various types of saws may be employed to cut the logs into rough lumber of different lengths, widths and thicknesses. The boards are then stacked and placed in drying kilns. Once dry, the boards are planed to final dimensions and to provide a smooth finish before being shipped. The sawmill process creates a lot of waste material that in many modern mills is used as an energy source.
This chapter provides information related to commonly used wood construction methods i. It briefly discusses the manufacturing of four major lumber-based mass timber products i. The discussion also addresses primary lumber products, such as dimension lumber, machine stress-rated lumber, and finger-joined lumber, which are the building blocks from which mass timber products are manufactured. Advantages of using wood in construction are illustrated by examples largely from North American practices. The life cycle assessment concept is also introduced.
Черт побери, я должен был сообразить .
Макс встал и медленно направился к указанному тоннелю, стараясь излишне не приближаться к октопауку. Когда он оказался у входа, вокруг головы инопланетянина побежала очередная волна цветовых пятен.
- Премного вам благодарен, - вежливо ответил Макс, вступая в проход. В трех-четырех сотнях метров от входа в тоннель он остановился, чтобы свериться с картой.
По-моему, Наи озабочена тем, как ее отношения с Патриком могут повлиять на близнецов. Все глаза обратились к гостю, появившемуся в дверях. - Доброе утро, Геркулес, - произнес Макс, вставая с кресла.SEE VIDEO BY TOPIC: Overview: Engineered Wood Products in Structural Systems for Residential Construction
Сперва Ричард не пошевельнулся. Но, когда Николь прикоснулась к нему во второй раз, он медленно открыл. - В чем. - спросил он. - Мне кажется, здесь небезопасно, - ответила. - По-моему, пора Включив фонарик, Ричард медленно повел лучом вокруг комнаты.
На Земле он не видел ничего, достойного сравнения с этим великолепием. Наконец, Макс добрался до логова октопауков и поспешно спустился по пандусу, оказавшись в зале, от которого в подземелье разбегались четыре тоннеля. Макс ввел в компьютер два "Л", и на крошечном мониторе появилась схема подземелья октопауков. Макс был настолько поглощен ее изучением, что сперва не расслышал за спиной шелеста механических щеток, сопровождаемого тонким писком.
Он не отрывал взгляда от компьютера, пока звук не сделался громким.
Ты невозможен. И тем не менее я люблю. Макс был возбужден.
Элли торопливо утирала кровь. Патрик развернул Макса кругом, обнял его за плечи и увел в гостиную. Николь поглядела на картинку, едва только она появилась на стене. Маленький Мариус находился в идеальном положении.
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А ты ничего не сказал Арчи.
Существенное различие между ними заключалось в том, что один из полов способен по достижении зрелости оплодотворять царицу. Сексуально настроенные взрослые копулировали удовольствия ради, но, поскольку этот контакт не имел последствий, различия между полами стирались.
Более того, долгосрочные связи в колониях чаще завязывались среди представителей одного пола, испытывавших сходные ощущения и разделявших общие точки зрения. Теперь ситуация усложнилась.
Подумав, добавил пытливый молодой человек. - Я пока не знаю, но надеюсь, что нет, - ответила Элли. Она едва не проговорилась. Так легко сказать все этим детям. но хватит одной ошибки.
"Фтизические, - говорил Ричард. - Вот это слово. Это уже не старческие, это совершенно дряхлые. Вот уж не думала, что придется прибегнуть к .