What was the revolutionizing secret that enabled medieval builders to reach skyscraping heights?
Many of the basic laws of physics were established years later
and material science was basically non-existent at that time. Yet,
hundreds of years later, we still observe some of their brilliance encoded in these medieval giants.
Check out their simple secret that requires no knowledge of physics or mathematics.
Throughout the history of humankind there has been a continual quest to build higher. Ancient
civilizations built enormous monuments to honor their gods and kings. Starting with the Egyptian
pyramids, Greek and Roman temples and so on. However, the materials, the engineering, and
construction techniques available 3000 years ago could only go to a certain limit. It was common
for structures from that time to have a large base to distribute the loads to a larger area. The
great pyramid of Giza held the title for tallest structure for nearly 4 thousand years. During the
middle ages, several cathedrals overtook the title of tallest structure in the world but
most of them did not last and ended up collapsing. Cathedrals were built with high ceilings to give
a feeling of monumentality and absolute power of god above everything else. However, building tall
structures was not an easy feat 600 years ago. The laws of motion had not been established yet
so building cathedrals was more of a trial and error rather than actual design work and
additionally builders from the middle ages did not have the same materials available as we do today.
Building any type of structure without steel or concrete is already a difficult task. Steel
can be shaped in many different forms and it's strong compared to other materials.
To put that into perspective a bar made out of steel can handle about five times more load than
the same bar made out of wood. On top of that, in the middle ages pressure treatment methods were
not available so the wooden structures were highly susceptible to rotting which was not great for
cathedrals that were supposed to last hundreds of years. The only other material they had at
their disposal was masonry stones. Masonry stones or blocks perform extremely well in compression
and were great for gravity bearing members like columns and arches. Most cathedrals used stone
blocks at the base which were heavy and hard to overturn. Strong binding materials like concrete
were not available so blocks were often stacked on top of one another with little to no tensile
resistance. Stones performed poorly when subjected to tension loads, gravity loads from the roof
would create lateral forces that would push the walls outwards and initiate a collapse mechanism.
Larger walls could solve this issue but that would drastically increase the amount of material needed
and would block potential openings in the walls for windows which were also essential
for medieval cathedrals. This is where the flying buttress comes into play. Buckling of the walls
under high gravity loads was a common failure in medieval cathedrals, to prevent buckling
many of the cathedrals used flying buttresses as lateral support systems. The flying buttress can
be seen on nearly all cathedrals from that time which is part of the reason why they're still
standing. The concept of the flying buttress is extremely simple and fairly effective,
it transfers lateral loads to the ground using inclined compression arches. Looking closer to
the connection system it can be seen that when lateral loads are applied one side of the wall
experiences tensile forces. With rainforest concrete this issue can be easily solved by
providing steel reinforcement in the tensile side of the member. However, concrete was not available
in medieval times so builders added the flying buttress that in a clever way avoided unwanted
tensile behavior. The buttresses were usually made large and heavy so they themselves don't overturn.
Sometimes additional weight was placed on top of them in the form of decorative spires.
This way the medieval builders manage to avoid tensile behavior within the structure. Modern
buildings do not employ this method in resisting lateral loads, the disadvantage of the buttress is
that it requires additional space making the base of the building fairly large. Most common lateral
resisting systems today are still bracing, moment frames, or concrete sheer walls all of which can
be integrated within the building and go by unnoticed by most non-engineering visitors.
Thank you for watching! Next time you are around one of these monumental buildings
try locating the flying buttress and imagine the transfer of loads
and of course don't forget to like and subscribe see you next time you.