a. In parallel with the seismic modeling presented above, a similar programme of work has utilised the combined finite/discrete element technology to investigate the strengthening of masonry walls subjected to blast loading. Both unstrengthened
and strengthened walls were simulated and compared against field test results performed at COTEC2 and Spadeadam3.
b. In the field tests, various types of masonry walls consisting of regular brick and concrete block, with and without window apertures have been subjected to variety of blast loads. The aim of the tests was to investigate the behaviour of the
retrofitted reinforced masonry support system under realistic conditions and develop the best techniques for design and installation.
c. The representation of the interaction of the blast wave with the masonry structure was accomplished using a semi-coupled approach. A CFD4 analysis was used to predict the propagation of the blast wave and a combined
finite/discrete element analysis to predict the response of the masonry wall.
d. Analysis of the blast wave propagation was undertaken using Air3d5 assuming that the masonry structure was stationary. Since the blast wave passes the wall within 4ms this assumption is valid. The pressure history predicted on the
face of the wall was subsequently applied as a loading to the finite/discrete element model.
e. The finite/discrete element (f/de) model comprised the masonry wall, a steel reaction frame, concrete support blocks and reinforcing anchors as depicted in Figure 11. A detailed representation of the masonry wall was provided. Each brick was
modelled as a discrete elastic solid, with a mortar interface model employed between the brick surfaces to account for the behaviour of the grout. The steel frame utilised an elasto-plastic material model to enable plastic deformation to be
captured.
f. In the case of the reinforced wall, non-linear anchor elements were used to represent the Cintec anchor reinforcement. These anchor elements account for elasto-plastic behaviour of the steel bars and the stiffness of the anchor grout in the
direction along the bars.
g. Loading applied to the structure was gravity and a time-history pressure (obtained from the CFD results) defined for each brick face. Gravity was applied as a first stage to obtained initial conditions for the subsequent pressure loading.
2 COTEC – Cranfield University Ordnance Testing Evaluation Centre, West Lavington Down, Wiltshire, UK. Tests undertaken in 1999-2000
3 Advantica (formerly British Gas), Test Facility at RAF Spadeadam, Cumbria, UK. Test undertaken in June 2001
4 Computational Fluid Dynamics
5 Air3d developed by Dr Tim Rose at the Royal Military College of Science, Cranfield University, Shrivenham, Wiltshire, UK.
