| As protective design engineering becomes more prevalent, cold-formed steel rectangular hollow sections (RHS) are often desired components for blast-resistant design. In addition to the energy-dissipating characteristics of steel, RHS have good torsional characteristics and square RHS have no weak axis in flexure, all ideal properties for response to blast loading. RHS have the added benefit of enabling the use of concrete-filling to create composite members which take advantage of the added mass and local stability provided by the concrete. Accordingly, the behaviour of unfilled RHS, concrete-filled RHS, and concrete-filled double-skin tubes (CFDSTs) subjected to air-blast loading is investigated.;An important aspect of the response of RHS subject to air-blast loading is the material response of cold-formed steel under elevated strain-rates. Dynamic tensile tests have hence been performed on sub-size tensile coupons taken from the flats and corners of cold-formed RHS members. Dynamic yield stresses were obtained at strain rates from 0.1 to 18 s-1. The dynamic increase factor was calculated for each data point and synthesized with previous cold-formed RHS tests at even higher strain rates (100-1000 s-1). The data set was used to determine Cowper-Symonds and Johnson-Cook parameters. The resulting material models can be used to determine the strength increase of cold-formed RHS subject to a wide range of impulsive, elevated strain-rate loads.;For the first time, the behaviour of unfilled RHS, concrete-filled RHS, and CFDSTs subject to air-blast loads has been investigated through large-scale testing. These arena trials illustrated the excellent performance and ductility of both the unfilled and composite cold-formed tubular steel members under extreme blast loads, without any fractures experienced in the cross-section. These instrumented tests provided much performance data that enabled the validation of subsequent models, using both single-degree-of-freedom and explicit finite element analysis. A parametric study was conducted with the validated finite element model to further characterize the response of RHS under air-blast loading. The influence of several key variables on the response of the various tubular members was determined and design guidance is provided. |
