Abstract: [Purposes] Complete bridge BIM models typically contain a large amount of detailed information，leading to difficulties in real-time visualization，transmission，and processing.Lightweight processing of bridge BIM models is a practical necessity to achieve efficient model visualization，transmission，and processing operations.Based on this,This paper proposes a lightweight method for bridge BIM models based on an improved QEM algorithm. [Methods] The method addresses issues such as loss of feature information，missing boundary data，and the generation of narrow triangular surfaces encountered when applying the classic QEM algorithm for lightweight processing of bridge BIM models.Improvements are made by refining boundary collapse conditions and optimizing the processing method for triangular patch contraction. [Findings] Experimental results on lightweight continuous girder bridge BIM models show that the improved QEM algorithm significantly reduces model data volume while effectively suppressing the occurrence of surface ruptures and better preserving key geometric features. [Conclusions] This enhances data transmission efficiency and improves the visual quality of the model．

Key words: QEM algorithm, bridge, BIM models, light weighting, feature information