P. Martinez-Vazquez

The Flight of Wind Borne Debris : An Experimental, Analytical, and Numerical Investigation : Part I (Analytical Model)

The destructive effects that storms or hurricanes have had over the infrastructure of urban areas, illustrates the necessity of investigating the behaviour of wind borne projectiles. Tachikawa (1983, 1988), Willis , et.al. (2002), Wang and Lechtford (2003), Holmes (2004), Holmes, et.al. (2006), Baker (2007), and Richards, et. al. (2005), have all examined this phenomenon. For example, Tachikawa established the relationship between the magnitude of drag and lift force coefficients with auto-rotational response of flat plates; Willis examined compact and rod-like objects and found a method to assess the velocity that results in their flight, and established a damage function using the kinetic energy of the moving object; Wang and Lechtford (2003) carried out experiments to observe flight trajectories of sheet type debris in a wind tunnel; Holmes (2004), and Holmes, et.al. (2006), proposed a mathematical model to determine the trajectory of compact and sheet-type debris, assessing the risk of damage and incorporating Magnus effects; Baker (2007) solved the equations of movement for compact and sheet-type debris and carried out a parametric study to identify the variables that control the phenomenon; whilst Richards, et.al. (2005) put together a three-dimensional model which was compared to wind tunnel tests over sheet-like debris. The present paper builds on these contributions and intends to provide a mathematical solution for the prediction of the trajectory of sheet-type debris by taking into account frictional forces and evaluating the magnified forces

Numerical studies on the effect of plan irregularities in the progressive collapse of steel structures

Abstract This research examines the effect of plan irregularities on the progressive collapse of four steel structures located in regions with different seismic activity. The plans of the first and second structure are irregular, whilst those of the third and fourth structures are regular. The collapse patterns of the four buildings are examined and compared under seven loading scenarios using non-linear dynamic and static analyses. In the non-linear dynamic analyses, node displacements above the removed columns and the additional force on the columns adjacent to them are discussed. Furthermore, the strength and capacities of the columns are compared to determine their susceptibility to collapse. In the non-linear static analyses, the pushdown curve and yield load factor of the structures are obtained after column removal. The results indicate that an irregular structure designed in site class C seismic zone, collapses in most of the column-removal scenarios. Moreover, when comparing regular and irregular structures designed in site class E seismic zone, the demand force to capacity ratio (D/C) of the columns in the irregular structures is on average between 1.5 and 2 times that of the regular ones.