Structural monitoring is concerned with the safety and serviceability of the users of structures, especially for the case of building structures and infrastructures. When considering the safety of a structure, the maximum stress in a member due to live load, earthquake, wind, or other unexpected loadings must be checked not to exceed the stress specified in a code. Although the steel will not fail at yield, excessively large deflections will deteriorate the serviceability of a structure. Therefore, to guarantee the safety and serviceability of steel beams, the maximum stress and deflection in a steel beam must be monitored. However, no practical method has been reported to monitor both the maximum stress and deflection. In this paper, assessment model for both safety and serviceability of a steel beam is proposed. The model was tested in an experiment by comparing stress level estimated by LiDAR system and stress level directly measured from electrical or fiber optic sensors. The maximum deflection measured from LiDAR system is also compared with the maximum deflection directly measured from LVDTs. In addition to displacement measurement, the proposed system can provide information on deformed shapes of steel beams.