A Skeleton That Sways
The traditional houses in Safranbolu, a UNESCO World Heritage site, appear rigid, but they are engineered to move. Their survival in one of the world's active seismic zones is not accidental. The design relies on a construction method called hımış, a composite system with a flexible timber skeleton and non-structural infill. This technique has been used in Anatolia for centuries. The upper stories of the houses are built with a timber frame made from local pine, fir, or chestnut wood. The builders joined these timbers using mortise-and-tenon connections, which are assembled without nails or glue.
This timber frame acts as the primary load-bearing structure. The spaces between the timbers are filled with materials like sun-dried adobe bricks, rubble stone, or fired bricks, held together with a lime or mud mortar. This infill adds mass and insulation but does not contribute to the structural rigidity. During an earthquake, the timber frame is designed to deform and sway, while the infill may crack or crumble. The design philosophy is to not rigidly resist the seismic forces, and dissipate the energy through controlled, plastic deformation. The houses essentially go with the flow of the ground motion, preventing the catastrophic, brittle failure seen in rigid masonry structures. The upper timber-framed floors often overhang the heavier stone masonry of the ground floor, a feature which also adds to the structural dynamics of the building during a quake.