2.5
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…
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。
View the full transcript and gain access to JoVE Core videos
Q1: What are the main components used in post-tensioned masonry walls?
Post-tensioned masonry walls use high-strength steel rods or flexible tendons anchored to the foundation and extended vertically within masonry unit cores or between wythes. Steel rods are tensioned by tightening nuts against steel plates at the wall top, while flexible tendons are stretched using hydraulic jacks and anchored with steel chucks gripping the tendon wires.
Q2: How does tensioning create compressive prestress in masonry walls?
After mortar cures, tendons are stretched tightly using hydraulic jacks or by tightening nuts against steel plates. This tensioning induces significant vertical compressive prestress throughout the wall, far exceeding stresses from self-weight and external loads. This prestress enhances the wall's ability to resist tensile forces from environmental factors.
Q3: Why do post-tensioned masonry walls resist wind and seismic loads better?
The vertical compressive prestress developed during tensioning strengthens the wall's resistance to tensile forces caused by wind and seismic activity. This enhanced strength allows walls to withstand lateral loads more effectively than conventional reinforced masonry, improving structural performance during environmental stresses.
Q4: What are the construction advantages of using post-tensioned masonry?
Post-tensioned masonry enables construction of thinner walls with fewer grouted cores compared to conventional reinforced masonry. This design conserves materials, reduces labor costs, and increases interior room space. The technique provides a cost-effective and structurally advantageous option for modern construction projects.
Q5: When does the tensioning process occur during wall construction?
Tensioning occurs after wall construction is complete and mortar has fully cured. The tendons are then stretched tightly using hydraulic jacks or by tightening nuts, depending on whether flexible tendons or threaded rods are used. This timing ensures the mortar provides adequate strength before prestress is applied.
Q6: How do threaded rods differ from flexible tendons in post-tensioning?
Threaded rods are tensioned by tightening nuts against steel plates installed on the wall top. Flexible tendons are stretched using specialized hydraulic jacks and then anchored with steel chucks that grip the tendon wires. Both methods achieve vertical compressive prestress, but use different anchoring mechanisms.
Q7: What role does mortar curing play in post-tensioned masonry construction?
Mortar must fully cure before tensioning begins to ensure the wall has adequate strength to support the compressive prestress. The curing period allows the mortar to develop sufficient bond between units and provide a stable base for the tensioning process. This sequence is critical for proper wall performance.