4 - Ultra-high performance concrete columns

Abstract

Over the past several decades, iconic and public buildings have become targets of terrorist bomb attacks, but most of these buildings were built without consideration of blast loading scenarios. Key load-carrying elements such as concrete columns are probably the most critical structural components for structural protection against bomb threats. Failures of columns may trigger catastrophic progressive collapse if there is insufficient structural redundancy. In this chapter, field blast tests on columns made of ultra-high performance concrete (UHPC) material that developed in Chapter 2, Development, testing, and numerical simulation of ultra-high performance concrete at material level, are presented. Test results showed that UHPC columns had excellent blast-resistant capability, only small mid-height deflection and minor concrete damage was observed after the blasting tests. Meanwhile, to quantify blast-induced damage and assess residual loading capacity of UHPC columns, static axial loading tests on postblast UHPC columns were carried out. Undamaged control samples were tested to provide benchmarks. Damage index and residual loading capacity of UHPC columns after various blast loadings were obtained. It was found that column cast with microsteel fiber-reinforced UHPC preserved more than 70% of its loading capacity after 35kg TNT detonation at 1.5m standoff distance, while high-strength concrete column only maintained 40% loading capacity after 8kg TNT detonation at 1.5m standoff distance. Finite element analysis and finite difference analysis are also conducted to reproduce the column response under these blast loads and yield damage evaluation curves for UHPC columns.