Report on High-Strength Concrete Columns

Description

The majority of reported studies12-27 in the field of HSC columns concern the behavior of columns subjected to con-centric loads. Understanding the behavior of columns under concentric loads assists in quantifying the parameters affect-ing column performance. However, conclusions from thistype of loading should not necessarily be extended to the case of combined loading, a situation most frequently encountered in columns used in buildings.

Reported data indicate that stress-strain characteristics of high-strength concrete, cover concrete, and parameters related to confining steel have the most influence on response of HSC columns subjected to concentric loads. The effect of the first parameter is discussed in Sec. 3.1. The remaining two parameters are discussed in the following sections.

Two major questions must be addressed when designingHSC columns. First, does the rectangular stress block de-scribed in Section 10.2.7 of ACI 318-89 apply to HSC? Sec-ond, are the confinement rules given in ACI 318-89 Sections10.9.3 and 21.4.4 adequate for HSC? In regions of high seis-micity, a major concern has been the ductility of HSC col-umns, resulting in a reluctance to use HSC in these areascompared with regions of low seismicity.

As a result, the focus of most reported investigations32,35-43 on performance of HSC columns under combined loading has been primarily to comprehend the seismic behavior of these columns. Some of these studies also have presented data that could be used to as-sess the flexural capacity of HSC columns subjected to com-bined loading. However, available data for HSC columns subjected to combined loading are relatively limited compared with HSC columns subjected to concentric loading.