Name: wood drying for stronger construction
Uploaded: 2024-09-12T16:16:32.000Z
Duration: 1 min 15 s
Channel: JoVE

Prendi in considerazione un legname non stagionato utilizzato per la pavimentazione: il legname si contrae quando l'umidità evapora, creando spazi vuoti alle giunture del pavimento.
Il legno si gonfia quando assorbe l'umidità e si contrae dopo l'essiccazione.
La quantità di umidità nel legno che corrisponde all'aria circostante è nota come contenuto di umidità di equilibrio.
La stagionatura impedisce al legno di restringersi dopo la costruzione, evitando danni strutturali ed estetici alla struttura costruita.
L'essiccazione all'aria è un metodo di stagionatura in cui il legname viene accatastato in modo lasco, adeguatamente sollevato da terra, tenuto separato per una corretta ventilazione e allineato per evitare che si pieghi. Ogni pila è protetta da pioggia e neve sotto un tetto impermeabile.
La stagionatura avviene anche mediante essiccazione in forno, in cui il legname viene stagionato disponendolo nel forno come nell'essiccazione all'aria.
Il legname standard viene essiccato al 19% di umidità per una maggiore stabilità. Per il controllo del restringimento, il legname strutturale viene essiccato al 15%.
Nel legname stagionato si osservano distorsioni che variano in base alla posizione originale del pezzo di legno all'interno dell'albero.

stagionatura del legno

La stagionatura del legno è un processo fondamentale che mira a ridurre e stabilizzare il contenuto di umidità nel legno per prevenire futuri restringimenti, danni strutturali o problemi estetici una volta che il legno viene utilizzato nella costruzione. Il legno si gonfia naturalmente quando assorbe umidità e si contrae mentre si asciuga.

L'obiettivo della stagionatura è raggiungere un contenuto di umidità in equilibrio; questo è il punto in cui il contenuto di umidità del legno si stabilizza per allinearsi ai livelli di umidità dell'ambiente circostante. Una stagionatura adeguata assicura che il legno non si restringa dopo la costruzione, mantenendo l'integrità strutturale e l'aspetto.

Esistono due metodi principali per stagionare il legno: essiccazione all'aria ed essiccazione in forno. L'essiccazione all'aria comporta l'accatastamento del legname in strati, sollevati da terra, adeguatamente distanziati per consentire una buona circolazione dell'aria. Vanno poi protetti dalla pioggia e dall'umidità con un tetto impermeabile. In questo metodo il legno viene allineato per evitare deformazioni durante l'essiccazione.

L'essiccazione in forno, d'altra parte, accelera il processo di essiccazione all'interno di un ambiente controllato, disponendo il legno in modo simile al metodo di 'essiccazione all'aria, ma all'interno di un forno. Il legname da intelaiatura standard viene in genere essiccato a un contenuto di umidità del 19 percento per garantire stabilità, mentre il legname strutturale può essere essiccato a un contenuto di umidità del 15 percento per controllare efficacemente il restringimento.

Il legname stagionato potrebbe presentare distorsioni, che variano a seconda della posizione originale del legno all'interno dell'albero. Questi metodi di stagionatura sono essenziali per preparare il legno ai suoi vari usi nell'edilizia, garantendo durevolezza e longevità.

Stagionatura del legno

Prendi in considerazione un legname non stagionato utilizzato per la pavimentazione: il legname si contrae quando l'umidità evapora, creando spazi vuoti alle giunture del pavimento.
Legno...

Education

Didattica

JoVE Core

Civil Engineering

Ingegneria Civile

Unit 1

Unità 1

Wood

Legno

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

Seasoning of Wood

wood drying for stronger construction

Seasoning of wood is the drying process used to lower and stabilize moisture content before wood is used in construction. Fresh wood can swell when it takes in moisture and contract as it dries. Seasoning helps reduce that movement so the wood stays more stable after it is built into a structure.

The main goal is to reach equilibrium moisture content. This is the point where the wood’s moisture level matches the moisture in the surrounding environment. When wood is seasoned properly, it is less likely to shrink after construction and cause structural damage or changes in appearance.

There are two common methods of seasoning wood: air drying and kiln drying. In air drying, lumber is stacked loosely in layers, raised off the ground, and spaced to allow good air circulation. A waterproof roof protects the stack from moisture, and the arrangement helps the wood dry without warping.

Kiln drying speeds up the process in a controlled setting called a kiln. The wood is arranged in a similar way to air drying, but the environment is managed more closely. Standard framing lumber is often dried to about 19 percent moisture content, while structural lumber may be dried to about 15 percent to better control shrinkage.

Seasoned lumber can still show some distortions. These changes depend on the wood’s original position in the tree. Seasoning prepares lumber for use in construction and helps improve durability and long-term performance.

Wood Drying for Stronger Construction

introduction to wood

Wood Structure and Uses in Building

Wood is a construction material made from trees. A tree trunk has several layers. The outside is a protective layer of dead bark. Under that is living bark, then the cambium, then sapwood. As sapwood matures, it becomes heartwood. The pith sits at the center of the trunk. The age of a tree can be read from its growth rings. These rings are concentric bands seen in a trunk cross-section. Wood strength also depends on grain. Grain refers to elongated, tubular cells that run along the length of...

softwoods and hardwoods

Wood Grain in Softwoods and Hardwoods

Softwoods and hardwoods come from different kinds of trees, and their leaf structures and cell makeup help explain how they are used. Softwoods come from cone-bearing trees with needle-like leaves. Hardwoods usually come from trees that shed broad leaves seasonally. Softwoods are made mostly of long cells called tracheids and a smaller number of rays, which are radial cells. This simpler structure gives softwoods a rougher grain. Because of this, they are often used in construction for...

lumber

Lumber Cutting Methods

Lumber is made from logs that are harvested, debarked, and processed into long pieces with a rectangular cross-section. The process starts when an automated saw slices a log into slabs. Those slabs then move on a conveyor belt to smaller saws, where they are cut into square-edged pieces of specific widths. Freshly cut lumber usually has rough surfaces. Its dimensions may also vary slightly from one end to the other. The way wood is cut affects both the lumber’s appearance and how it is used. <br...

structural properties and dimensions of lumber

structural-properties-and-dimensions-of-lumber

Wood Strength Tests and Lumber Sizes

Wood strength depends on how its fibers are aligned along the length of the tree. This alignment gives wood much greater tensile strength along the grain than across it, sometimes up to twenty times higher. Wood also tends to perform better under compression than under tension. Fiber length varies by wood type. Hardwoods have fibers about one twenty-fifth of an inch long. Softwoods have longer fibers that range from one-eighth to one-third of an inch. Laboratory tests help measure how wood...

seasoning of wood

Seasoning of wood is the drying process used to lower and stabilize moisture content before wood is used in construction. Fresh wood can swell when it takes in moisture and contract as it dries. Seasoning helps reduce that movement so the wood stays more stable after it is built into a structure. The main goal is to reach equilibrium moisture content. This is the point where the wood’s moisture level matches the moisture in the surrounding environment. When wood is seasoned properly, it is...

wood surfacing

Wood Surfacing for Smooth, Safe Lumber

Wood surfacing smooths lumber, improves its size accuracy, and makes it safer to handle. It is a key finishing step in woodworking and construction. The process also helps correct small distortions that can form as wood dries. Before surfacing, the wood may be sized slightly larger to account for shrinkage during seasoning, which is the drying stage. A plane, a tool with rotating blades, is used to remove material and smooth the surface. The same tool can also round the edges a little, which...

lumber defects

Common Wood Flaws in Lumber

Lumber defects are flaws in wood that can change both its appearance and its strength. These defects come from tree growth and from the way lumber is processed. Knowing the main defects helps explain why some boards are better for construction and manufacturing than others. Some defects begin in the tree itself. Knots form where branches were once attached to the trunk, and knotholes appear when those knots fall out. Decay and insect damage are also natural defects that can weaken wood and...

wood fasteners

Wood Fastener Types and Uses

Wood fasteners connect parts of a wood structure and help keep members in place. The strength of the connection depends mainly on direct bearing between the wood members. Different fasteners are chosen for different jobs and structural needs. Nails are the most common wood fasteners. They are sharp-pointed metal pins that are driven into wood with a hammer or a mechanical nail gun. Nails come in many diameters, head styles, and lengths. Nailing methods also matter. Face nailing places the...

veneer

How Veneer Is Cut and Used

Veneer is a thin sheet of wood that is usually about one-eighth of an inch thick or less. It is made to show the look of wood while using timber more efficiently. Veneer is common in furniture and other finished wood products. One common way to make veneer is rotary cutting. In this method, a log is mounted in a large lathe and spun against a knife edge. As the knife moves deeper into the turning log, it peels off a continuous strip of wood. This creates rotary-cut veneer. Other veneer...

wood products

Engineered Wood Products in Construction

Engineered wood products are made from wood strands, veneers, lumber, and even waste wood shreds. They are used in both structural and nonstructural building applications. These materials are designed to improve strength, durability, and versatility in modern construction. Glue-laminated wood, or glulam, is made by bonding several smaller pieces of dimensional lumber with adhesive. Cross-laminated timber uses solid lumber panels with layers placed so the grain direction alternates. This layer...

wood panel products

Types of Wood Panels in Construction

Wood panels are common construction materials used for flooring, siding, and roofing. They usually come in standard 4-foot by 8-foot sheets. Their thickness can range from one-quarter of an inch to one and one-eighth inches. Plywood is one of the most familiar wood panels. It is made by gluing thin wood veneers, or layers, under pressure. The outer veneer grain runs lengthwise, while the inner layers run widthwise. Plywood also has an odd number of layers, which helps keep the panel...

key terms and concepts

Learn how seasoning reduces wood moisture, limits shrinkage, and prepares lumber for construction with air drying and kiln drying methods.

Wood Drying for Stronger Construction | JoVE K12

JoVE Core Civil Engineering provides a foundational exploration of essential construction materials in civil engineering, focusing on bricks, stones, steel, wood, and concrete through easy-to-understand animated videos. This collection covers the properties, manufacturing processes, and practical applications of these materials. Additionally, the accompanied science-in-action videos demonstrate the research experiments performed in laboratories.

civil engineering

Wood Drying for Stronger Construction

Description

Transcript

Tags