From the results it can be seen that the influenceof the polycar-bonate is quite significant. The flexuralstiffness is reduced to be-tween 26% and 69% of the stiffness based the stone alone. The panels using Stoke Hall stone showed the greatest reduction in stiffness.
Comparison with the earlier initial test, constructed using con-ventional mortar is quite interesting. The test sample was 100 mm in thickness. The flexuralstiffness, prior to cracking, corrected to a width of 320 mm was 60.1 109 mm2 compared with 196 and 33 109 for the 100 mm deep panels using Clashach and Stoke Hall stone respectivel y. Both the depth and the spacing of joints was the same for all beams. The initial test panel was constructed with a variety of available stones. The Woodkirk and Cat Castle stones share asimilar petrographic history to Stoke Hall, being
geologically earlier coarse grained gritstones compared with the finer grained mudston e Clashach. The stiffness is clearly less than the stiffness of the stone itself (assumingpropertie s similar to Stoke Hall. The interaction between bedding layers and brick or stone is complex, with relatively little research. Hendry [13] reported on tests on the compressive strength of brick masonry using differing bed joint materials including mortar, steel and rubber.
Thin steel increases the strength brick assembly by more than
40% of the strength of the brick itself whilst rubber joints resulted in a 87% reduction in strength. More recently [14] tests on sand- stone have shown that the stiffness of sandstone in axial compression is strongly affected by the nature of the bed-joint, with dry joints exhibiting greater stiffness than mortar joints.
The significance of the reduction in flexuralstiffness of the pa-nel due to the incorporation of the polycarbona te spacer can be checked by considering the maximum deflectionof apanel in a realistic application. Consider a panel 1.0 mwide spanning 3.0 m between floors subjected to amaximum wind pressure of 2.0 kPa.