Abstract The use of high strength steel (HSS) in the construction of concrete encased steel (CES) composite columns is often limited by the strain incompatibility issue between HSS and concrete at peak-load. This study proposes an alternative approach to confine the high strength concrete with Engineered Cementitious Composite (ECC) to improve its compatibility with high strength steel. The main purpose of this study is to experimentally evaluate the axial compressive performance of the proposed composite column cross-section configuration. Behaviours of fifteen short columns including twelve ECC-CES columns are investigated in terms of failure modes, load-deformation curves, ductility and energy absorption capacity. The test parameters included ECC and concrete strengths, ECC cover thickness, steel section shape and column section’s aspect ratio. It was found that ECC generally improved the failure behaviour of high strength steel CES columns and increased the deformation and energy absorption capacity. On average ECC-CES columns showed around 12% and 8% higher ductility and toughness than control concrete column, respectively. A detailed 3D nonlinear finite element model was developed and validated against experimental results. Applicability of current design codes to predict the ultimate strength of ECC-CES columns was also evaluated. Finally, a method to calculate the ECC-CES column’s capacity considering effective material stresses at peak-load was proposed.

中文翻译：

---

ECC-混凝土包裹高强钢组合柱的抗压性能

摘要 高强度钢 (HSS) 在混凝土包钢 (CES) 复合柱的建造中的使用常常受到峰值载荷下 HSS 与混凝土之间应变不相容性问题的限制。本研究提出了一种替代方法，用工程水泥基复合材料 (ECC) 限制高强度混凝土，以提高其与高强度钢的相容性。本研究的主要目的是通过实验评估所提出的复合柱横截面配置的轴向压缩性能。包括 12 个 ECC-CES 柱在内的 15 个短柱的行为在失效模式、载荷-变形曲线、延展性和能量吸收能力方面进行了研究。测试参数包括ECC和混凝土强度、ECC覆盖层厚度、钢截面形状和柱截面纵横比。发现ECC普遍改善了高强度钢CES柱的破坏行为，增加了变形和能量吸收能力。平均而言，ECC-CES 柱的延展性和韧性分别比对照混凝土柱高约 12% 和 8%。开发了详细的 3D 非线性有限元模型，并根据实验结果进行了验证。还评估了当前设计规范在预测 ECC-CES 柱的极限强度方面的适用性。最后，提出了一种考虑峰值载荷下有效材料应力的 ECC-CES 柱容量计算方法。平均而言，ECC-CES 柱的延展性和韧性分别比对照混凝土柱高约 12% 和 8%。开发了详细的 3D 非线性有限元模型，并根据实验结果进行了验证。还评估了当前设计规范在预测 ECC-CES 柱的极限强度方面的适用性。最后，提出了一种考虑峰值载荷下有效材料应力的 ECC-CES 柱容量计算方法。平均而言，ECC-CES 柱的延展性和韧性分别比对照混凝土柱高约 12% 和 8%。开发了详细的 3D 非线性有限元模型，并根据实验结果进行了验证。还评估了当前设计规范在预测 ECC-CES 柱的极限强度方面的适用性。最后，提出了一种考虑峰值载荷下有效材料应力的 ECC-CES 柱容量计算方法。