Name: how masonry walls gain extra strength
Uploaded: 2024-09-12T16:16:29.000Z
Duration: 1 min 15 s
Channel: JoVE

ポストテンション石積み壁は、基礎に固定され、石積みユニットのコア内または2つの石積みワイスの間に垂直に伸びる、ねじ山付きの高強度鋼棒または柔軟な腱を使用して構築されます。
壁の建設が完了し、モルタルが硬化すると、特殊な油圧ジャッキを使用して非常にしっかりと引き伸ばすことにより、腱に張力がかかります。次に、腱のワイヤーをつかむスチールチャックを使用して固定されます。
一方、ねじ棒は、壁の上部に取り付けられた鋼板に対してナットを締めることによって張力がかけられます。
この張力は、壁に大きな垂直圧縮プレストレスを誘発し、これは壁の自重と壁に作用する外部荷重による応力よりもはるかに高くなります。
壁に発生するこの圧縮プレストレスは、風や地震荷重に起因する引張力に抵抗する強度を高めます。
その結果、ポストテンション組積造壁は、従来の補強組積造壁に比べて薄い組積造壁の施工が可能となり、室内空間の拡大に貢献しています。

ポストテンション ブロック壁

ポストテンション ブロック壁は、高強度の鋼棒または柔軟な緊張材を使用して、ブロック構造の強度と効率を高めます。これらの要素は基礎にしっかりと固定され、ブロックのコア内またはブロック間の垂直方向に伸びます。建設プロセスでは、これらの緊張材を配置した状態で壁を建設し、モルタルが完全に硬化するまで待ちます。

硬化プロセスの後、緊張が始まります。壁の上部にある鋼板にナットを締め付けて鋼棒に緊張材を張ります。柔軟な緊張材の場合、緊張材をしっかりと伸ばす特殊な油圧ジャッキを使用して緊張材を張り、その後、緊張材ワイヤをつかむ鋼チャックを使用して固定します。この緊張方法により、壁にかなりの垂直方向の圧縮プレストレスが与えられ、壁の自重や外部荷重によって生じる応力を大幅に上回ります。

このような圧縮プレストレスの適用は、風や地震活動などの環境要因によって通常誘発される引張力に対する壁の耐性を高めるため、非常に重要です。グラウトコアを少なくしてより薄い壁構造を使用できるようにすることで、ポストテンション石積みは材料を節約するだけでなく、人件費を削減し、利用可能な内部スペースを増やすため、現代の建築においてコスト効率が高く、構造的に有利な選択肢の1つです。

ポストテンション石積みの壁は、基礎に固定されて延長されたねじ山付きの高強度鋼棒または柔軟な腱を使用して構築されます...

Education

JoVE Core

Civil Engineering

土木工学

Unit 1

ユニット1

Masonry

組積造

KEY TERMS AND CONCEPTS

主要用語と概念

Posttensioned Masonry Walls

how masonry walls gain extra strength

Post-tensioned masonry walls gain extra strength from high-strength steel rods or flexible tendons. These tensioning elements are anchored to the foundation and run vertically through the wall. In some walls, they sit inside the cores of the masonry units. In others, they are placed between the masonry wythes, or layers.

The wall is built first with the tensioning elements already in place. After the mortar cures fully, the wall is tightened. Steel rods are tensioned by turning nuts against steel plates at the top of the wall. Flexible tendons are stretched with special hydraulic jacks. Steel chucks then hold the tendon wires in place.

This tightening creates a strong vertical compressive prestress in the wall. Prestress means the wall is put under compression before outside loads act on it. That compressive force is much greater than the wall’s own weight and the stresses from later loading. It helps the wall resist tensile forces, which can come from wind and seismic activity.

Post-tensioned masonry can also make construction more efficient. Thinner walls may be used, and fewer grouted cores are needed. That can save materials and reduce labor costs. It can also leave more usable interior space, which makes this method both practical and structurally useful in modern construction.

How Masonry Walls Gain Extra Strength

composite masonry walls

Bonding and Materials in Composite Masonry

Composite masonry walls use two or more wythes, or vertical layers, of masonry to form one unified wall. The wythes may use the same material or different masonry materials. They are joined to work together as a single structure. These wythes can be bonded in several ways. Builders may use mortar-filled collar joints, grouted spaces, or rigid metal ties with reinforcement. Masonry header units can also connect the layers, but this method is rare. Metal ties are often preferred because they...

masonry cavity walls

Masonry Cavity Walls and Moisture Control

Masonry cavity walls use two wythes, or layers, with a hollow space between them. The outer and inner wythes are linked only by corrosion-resistant metal ties. This design helps manage water and improve wall performance. When rainwater passes through the outer wythe, it moves down through the cavity. Flashing catches the water and directs it toward weep holes, where it can leave the wall. The inner wythe often has damp-proofing on the cavity side. This layer also works as an air barrier. The...

masonry loadbearing walls

How Masonry Walls Support Buildings

Masonry load-bearing walls support floors and roofs and carry those loads down to the foundation. They are built from brick, stone, or concrete masonry units. These walls rely on compressive strength, which means they can resist pushes from above very well. Masonry walls may be reinforced or unreinforced, depending on the building needs. They carry dead loads and live loads while using working stresses that stay below the materials' ultimate strength. That safety margin helps the structure...

masonry curtain walls

Masonry Curtain Walls and Support Systems

Masonry curtain walls use brick or stone veneer as an exterior cladding system. The veneer is supported by the building structure, so the wall can be both attractive and functional. Two main construction methods are used for these walls. One method builds the masonry units in place through traditional layering. The other uses prefabricated panels that are assembled on the ground and then lifted into position. In traditional construction, steel shelf angles attached to the spandrel beam carry...

posttensioned masonry walls

Post-tensioned masonry walls gain extra strength from high-strength steel rods or flexible tendons. These tensioning elements are anchored to the foundation and run vertically through the wall. In some walls, they sit inside the cores of the masonry units. In others, they are placed between the masonry wythes, or layers. The wall is built first with the tensioning elements already in place. After the mortar cures fully, the wall is tightened. Steel rods are tensioned by turning nuts against...

cavity drainage and flashings in masonry walls

cavity-drainage-and-flashings-in-masonry-walls

Moisture Control in Masonry Cavity Walls

Masonry cavity walls use a gap between two wythes, or wall layers, to help control moisture. The cavity is usually at least 2 inches wide, and it may contain insulation. Even with insulation, a clear space of at least 1 inch is kept so water can drain away. Some walls also use a continuous drainage mat to reduce the needed space while still moving moisture out. Weep holes are another key part of cavity drainage. These openings sit at the base of the cavity and let collected water escape. They...

thermal insulation in masonry walls

Masonry Wall Insulation Options

Masonry wall insulation can be placed on the outside, inside the wall, or on the interior surface. The best choice depends on the climate, the building design, and whether the wall is being built new or retrofitted. In hot, dry climates, masonry can help smooth indoor temperatures by absorbing heat during the day and releasing it at night. In many other climates, extra insulation is needed to improve thermal resistance. One common exterior method is an Exterior Insulation and Finish System, or...

expansion and contraction in masonry walls

expansion-and-contraction-in-masonry-walls

Masonry Wall Joints for Temperature and Moisture

Masonry walls change size slightly as temperature and moisture change. Builders account for this movement so the wall does not crack or shift out of place. Thermal movement is usually easy to measure and plan for. Moisture movement is harder to predict. New clay masonry units often absorb water and expand over time in normal outdoor conditions. New concrete masonry units behave differently. They usually shrink as they lose extra moisture gained during production. These opposite changes make...

movement joints in buildings

How Buildings Handle Structural Movement

Buildings are designed to handle movement from temperature changes, moisture changes, and structural deflection. If these changes are ignored, they can cause visible damage or even unsafe conditions. Movement joints give building materials room to move without creating distress. Working joints are the simplest type. They are placed during construction and help materials cope with change as the building goes up. Shingled roofs and wood bevel siding are common examples because they can move with...

types of building separation joints

Building Joints for Movement and Stability

Building separation joints help large or complex buildings move in a controlled way. They split a structure into smaller, separate units. This reduces stress when the building shifts under different forces. The joints are grouped into three main types: volume-change joints, settlement joints, and seismic separation joints. Volume-change joints handle expansion and contraction caused by temperature changes and moisture changes. They are placed where the building mass has discontinuities,...

efflorescence in masonry

Stopping White Salt Crystals on Masonry

Efflorescence is the white, fluffy crystal layer that can form on masonry walls. It happens when water-soluble salts in brick, stone, concrete, or mortar are dissolved by water and carried to the surface. When the water evaporates, the salts are left behind as a powdery deposit. New efflorescence is often seen soon after construction. In many cases, it can be cleaned with water and a brush. It may also fade over time as rain leaches salts out of the masonry surface. If efflorescence appears...

mortar joint deterioration in masonry

Repairing Damaged Mortar Joints in Masonry

Mortar joints in masonry can break down when water collects in them and freezes. The repeated freezing and thawing makes the water expand and shrink. That process creates cracks in the joints and can spread damage over time. As the mortar worsens, pieces may spall, or break off from the joint surface. Loose masonry units can follow, and the wall becomes weaker. Damaged joints also let moisture move into the wall, which adds to the problem. Good construction helps protect mortar joints. Using...

masonry in cold and hot weather conditions

masonry-in-cold-and-hot-weather-conditions

Protecting Mortar During Weather Changes

Masonry work changes in cold and hot weather because mortar must stay at the right temperature and moisture level. If mortar freezes before it cures, its strength and watertightness can drop. For proper hydration and curing, mortar should stay between 60°F and 80°F. When the weather is below 40°F, the water used for mortar must be heated. The water should not exceed 120°F, because very hot water can reduce compressive strength and bond strength. Masonry units and sand should also stay dry and...

masonry paving

Masonry Paving Materials and Base Layers

Masonry paving uses bricks, stones, and concrete masonry units to create durable walking and driving surfaces. These materials are selected for their shape, color, strength, and resistance to abrasion and weathering. Masonry units can be used in different paving setups depending on the site and the load they must carry. Some paving systems are installed dry on a thin sand layer over a gravel base. Others are set in mortar or asphalt on a concrete slab. For areas with heavy vehicular loads, a...

key terms and concepts

See how post-tensioned masonry walls use steel rods or tendons, prestress, and anchoring to boost strength against wind and seismic forces.

How Masonry Walls Gain Extra Strength | 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

How Masonry Walls Gain Extra Strength

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