双钢筋混凝土梁的受弯试验及裂缝计算

双钢筋系由两根纵向平行的纵筋与之垂直的短横筋按一定间距焊接组成梯格型骨架,采用双钢筋技术,可以改善钢筋混凝土的粘结作用,从而改善钢筋混凝土受弯构件的裂缝分布,减小裂缝宽度,使裂缝开展呈现细而密的特征。然而,目前使用的双钢筋类型主要是由冷拔低碳钢丝或冷轧钢筋制成的双钢筋,这些双钢筋大多用于小跨度的单向板、过梁、楼梯等构件中,而采用大直径热轧带肋三级钢筋制成的双钢筋混凝土构件国内外尚未见有报道。为了充分发挥双钢筋的技术优势,拓宽双钢筋技术的使用范围,对热轧带肋三级钢筋焊制的双钢筋构件作了较全面的分析研究,重点研究了双钢筋受弯构件的裂缝及变形计算,对双钢筋构件的裂缝特征作了较完整的理论分析。通过试验观察和理论分析,并针对热轧带肋三级钢筋制成的双钢筋混凝土构件,提出了裂缝计算的建议公式。并与普通构件对比进行技术经济分析,可取得良好的经济效益。

BENDING TEST AND CRACK CALCULATION OF BI-STEEL CONCRETE BEAM

A bi-steel ladder framework is formed by two parallel longitudinal reinforcements and short transverse reinforcements plumbing longitudinal reinforcement. In theory adopting bi-steel technique can improve bending function between reinforcement and concrete and decrease width and space of cracks of bending member, thus producing fine cracks appear slight and dense. However, at present bi-steel is made from cold-drawn wire or cold-rolled fibbed steel, and is often used in some members such as small span one-way concrete slab, lintel and stairs. The study on bi-steel made of Ⅲ grades big-diameter hot rolled ribbed steel has not been reported at present in China and abroad. In order to take enough advantage of bi-steel and extend application, it is analyzed the bi-steel structure which is welded by hot relied ribbed steel, and emphasized the methods of calculating the cracking and deformation, and also analyzed the feature of cracking completely. At the same time, it is presented the suggested formula of calculating cracks on a bi-steel concret structure with hot rolled ribbed steel by the observation and theoretical analysis. A nice technical and economic benefit may be got by comparing it with common beam.