Reinforcement by polyurethane to stiffness of air-supported fabric formwork for concrete shell construction

Abstract

By spraying concrete on inner surface, air-supported fabric structures can be used as formwork to construct reinforced concrete shell structures. The fabric formwork has the finished form of concrete structure. Large deviation from the desired shape of concrete shells still remains as central problem due to dead weight of concrete and less stiffness of fabric formwork. Polyurethane can be used not only as a bonding layer between fabrics and concrete but also as an additional stiffening layer. However, there is little research on mechanical behaviors of the polyurethane shell structure. This paper presents experimental studies on an inflated fabric model with and without polyurethane, including relief pressure tests, vertical loading tests and horizontal loading tests. Experimental results show that the additional polyurethane layer can significantly enhance the stiffness of the fabric formwork. Compared with the experiment, a numerical model using shell layered finite elements has a good prediction. The reinforcement by polyurethane to improve stiffness of air-supported fabric formwork is expected to be considered in the design and construction of the concrete shell, especially dealing with the advance of shape-control.

摘要

通过内部喷射混凝土的方法, 气承式充气膜结构可以被用作建造混凝土薄壳结构的模板。气膜 模板施工变形后的形状决定了混凝土薄壳结构的最终形态, 而较小的模板刚度将导致混凝土凝固成形 后薄壳结构的形态与设计值偏差较大。实际施工情况表明, 气膜模板中用作结合层使用的聚氨酯层可 以为其提供一定的刚度, 然而, 与聚氨酯层力学性能相关的研究却很少。本文对气膜模板喷涂聚氨酯 前后的模型分别进行了泄压、竖向加载和水平加载的试验研究, 对比结果表明聚氨酯层可以显著增强 气膜模板试验模型的刚度。采用分层壳单元进行的非线性有限元数值模拟的结果与试验现象较为吻 合。在气膜钢筋混凝土结构的设计和施工中应当考虑聚氨酯层对气膜模板刚度的强化作用, 尤其在提 升结构形态控制方面。