Infrastructure Sustainability: Vulnerability of Axially Loaded Columns Subjected to Transverse Impact Loads

Abstract

Infrastructure engineering and sustainable design are among the important drivers of sustainable development. Increased industrialisation has brought to the forefront the susceptibility of concrete columns (in both buildings and bridges) to vehicle impacts. Accurate vulnerability assessments are crucial in the design process due to the possibly catastrophic nature of the failures that can occur. This chapter reports on research undertaken to investigate the impact capacity of columns of low to medium raised buildings designed according to the Australian standards. Numerical simulation techniques were used in the process and validation was done by using experimental results published in the literature. The investigation thus far has confirmed the vulnerability of typical columns in five story buildings located in urban areas to medium velocity car impacts. Hence, these columns need to be re-designed or retrofitted. In addition, accuracy of the simplified method presented in EN 1991-1-7 to quantify the impact damage was scrutinised. A simplified concept to assess the damage caused by all collision modes was introduced. The research information will be extended to generate a common database to assess the vulnerability of columns in urban areas to the new generation of vehicles.

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Validation Of The Finite Element Model

Experimental Set-Up and Material Properties of the Tested Columns

Experimental results of the Feyarabend (Feyerabend, 1988) column tests were used in the validation process. The column was tested in a horizontal position, as shown in Figure 1. Fixed support conditions were achieved by stationary steel sections fixed at the ground, and the other end being hinged and free to slide parallel to the longitudinal axis of the column while being restrained by a 20t mass. The mass can slide over horizontal low friction rails. The axial load is applied by using prestressing wires located either side of the column, and impact load was generated by dropping the 1.14t mass onto the column at mid span.

Figure 1.

The test set-up by Feyerabend (Feyerabend, 1988)

The testing procedure involved impact test on 300x300mm rectangular column specimens made out of Grade 47 concrete. Under the mid span impact, the column has reached near failure conditions. The properties of the test specimen are tabulated in Table 1.

Table 1.

Characteristics of Feyerabend’s (Feyerabend, 1988) test specimens

Test	SB2
Cross-section (mm) Span (m) Cube strength, fcu (MPa) Yield stress, fy (MPa) Main bars, As Shear reinforcement, Avs Restraining mass (t) Initial axial load (kN) Striker mass (t) Impact velocity (m/s) Velocity at which fy was reached (m/s)	300×300 4.0 47 548 4ϕ25 12ϕ@150 20 -197 1.14 3.0 ±1.8

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