Blast Injuries to People in Buildings
Knut B. Holm; Norwegian Defence Research Establishment (FFI); Kjeller, Norway
Keywords: Explosives safety, Blast injuries
Abstract
A study has been performed to estimate primary blast injuries to humans inside buildings that are exposed to blast
waves. The blast wave propagating into the building through openings can cause injuries similar to blast injuries in
free-field. By numerical simulations the pressure inside a building is found for a series of incident blast waves with
different values of peak pressure and specific impulse. The simulations include the building damage that creates the
openings. The simulations are verified by experimental data.
From the pressure the velocity of the human chest wall and the corresponding lethality is found by methods based on
the Axelsson model, which takes account of the complete time history of the pressure.
The lethality from blast injury is compared with estimated values of the lethality caused by building debris. In
concrete structures the blast injury is significant at incident pressures down to 500 kPa. PI-curves are fitted to the
results for concrete structures. In wooden constructions the injury from building debris is much larger, and the blast
injury can be neglected for incident pressures below 3 MPa.
Introduction
When the blast wave from an explosion damages a building, people inside can get injured from impact by building
parts. In addition the blast wave propagating into the building through openings can cause injuries similar to primary
blast injury in free-field.
The small openings originally in the exterior of a building (e.g. ventilation) only allow a relatively slow pressure
build-up inside. However, if the building damage caused by the blast wave creates larger openings, the subsequent
part of the blast wave can easier propagate into the building. Inside the building reflections will lead to a blast wave
with a complex shape.
The injuries caused by complex blast waves can be estimated from the pressure-time history. Numerical simulations
can give the pressure-time history at any position in a building. The dynamic response of the building can also be
included. A series of such simulations is described in this paper. The simulation model is verified by comparing the
results with experiments.
This study is a part of the development of the Norwegian-Swedish computer tool for quantitative risk analysis,
AMRISK
1
. The work is made by the support of the Norwegian Defence Materiel Agency.
Blast Injury Model
For people exposed to blast, two injury mechanisms are normally considered.
2
The first one is the direct or primary
effect against the body and particularly the lungs. The second is the indirect effect of impact of the body against the
ground or a wall after being accelerated by the blast wave. Indirect effects are not considered here, but some results
indicate that they are of less importance than the direct effects.
3
For the estimation of direct blast effects from simple shock waves the modified Bowen’s model
4, 5
is generally
accepted. Inside a building the pressure wave may have a complicated shape and be without a sharp shock front, in
which case this model cannot be used. To be able to estimate the direct effect of such complex blast waves,
mechanical models of the chest have been developed. The model of Axelsson and Yelverton
6
, which is the most
prevalent, describes the movement of the chest or the chest wall in a single degree of freedom model.
