Dynamic testing and stiffness evaluation of a six-storey timber framed building during construction

This paper is concerned with the dynamic testing and stiffness evaluation of a six-storey timber framed building. The principal reason for undertaking the measurements was to quantify the difference between the stiffness of the bare frame, which is used in design, and the stiffness of the complete building. Two types of measurements were taken. Laser measurements, where the buildingʹs natural frequencies were determined at eleven stages during construction; and forced vibration tests, where all the characteristics of the fundamental modes were measured at three key stages. The buildingʹs stiffness at the various stages was derived from the measured natural frequencies, as the buildings mass was known. The tests showed the decreasing stiffness of the bare timber frame with increasing height during construction. The addition of the stairway and internal plasterboard had a considerable stiffening effect in the translational directions but a relatively minor effect in the torsional direction. The erection of the brickwork cladding provided further significant increases in stiffness in all directions. In one translation direction the complete building was 17.7 times stiffer than the bare timber frame.