Investigation Progressive Collapse of K-Model Steel Truss Bridge under Additional Live Load Following Bridge Repairs

The main purpose of this study is to investigate the progressive collapse of the K-truss Bridge under additional live load caused by bridge repairs. In this case, the effect of several parameters such as length of members, bridge span ratio, steel grade, and load cases, were evaluated. The initial design of the bridge models was carried out using AASHTO LRFD Bridge Design Specifications. Bridge models were constructed with two different span ratios: bridge Model A with a common ratio of 1:2:1, and bridge Model B with a 1:1.3:1 span ratio. The results were obtained by a numerical finite element method using SAP2000 software. Results showed that the 1:1.3:1 span ratio is a more reasonable ratio for K-truss bridges. In all conditions, models with a span ratio of 1:1.3:1 had higher ultimate strength and more bearing capacity. In all load cases, models with a member length of 6m and a total height of 12m reduced the load-bearing capacity before reaching the yield displacement. Different lengths were provided for horizontal and vertical members of the trusses. Models with four-meter lengths had a higher bearing capacity than the three and six-meter models. The collapse process was different depending on the model details. All bridge models collapsed due to the buckling of the compression members.