Direction-Dependent Changes in Traffic-Induced Vibrations Following Rehabilitation of a Low-Rise Masonry Building: A Before-and-After Field Study

Structural rehabilitation modifies the stiffness and continuity of masonry buildings and may therefore alter their response to environmental vibrations. However, its influence on traffic-induced vibration transmission and human perception remains insufficiently documented. This study presents a before-and-after field investigation of a low-rise masonry building that had experienced severe settlement-induced cracking and was subsequently rehabilitated using flexible polyurethane joints and local strengthening. Controlled passages of the same passenger vehicle over a speed bump were performed at several increasing speed levels, with repeated runs under comparable measurement conditions. Vibrations were recorded at a structural point at ground level and at two floor locations representative of human exposure. Structural effects were assessed using WODB, the maximum ratio of one-third-octave peak acceleration to the corresponding SWD-II line A reference value, while human vibration perception was assessed using WODL, the maximum ratio of one-third-octave RMS acceleration to the corresponding perception threshold. Mean WODB increased in one horizontal direction and decreased in the other, whereas mean WODL increased in all three directions at both floor measurement locations. The governing assessment bands also tended towards lower frequencies after rehabilitation. All indices remained below their respective thresholds, with the highest WODL equal to 0.658. For the investigated building and vehicle-passage conditions, the observations indicate direction-dependent changes in structural assessment indices and increased mean floor-level perception indices, rather than a uniform vibration reduction.