Performance of Composite Plate Girder Bridges with Full-Depth Precast Concrete Deck Systems

Recently, the construction of composite steel plate girder bridges that uses precast concrete deck planks has significantly increased due to their ease of construction, rapid installment, relatively low cost, and lightweight. Recent structural failures have been reported for this type of bridge system, which include the total collapse of one section of the Mexico City Metro Overpass in May 2021. The bridge collapse killed 23 people, and dozens were injured. This study provides an overview of the causes of the failure of the Mexico City Metro Overpass. It highlights important structural deficiencies that are currently overlooked in design codes and could cause future catastrophic collapses in existing bridges that utilize the same type of bridge. Therefore, a detailed finite-element model of a composite steel girder bridge that uses precast deck planks was established. The bridge dimensions, properties, and loading conditions that were used in this study were obtained from the Mexico City Metro Overpass parameters with some modifications. The performance of the bridge structure was investigated under different conditions with consideration of joint deterioration between the precast concrete planks. The results indicated that the deterioration in the transverse joints due to long-term exposure to moisture, environmental conditions, and vibrations affected the amount of force that was transferred between the concrete deck and the bare steel girder and, therefore, hindered the composite action. The gradual loss of composite action could cause a significant increase in the demands that are imposed on the bare steel section and result in high deflections in the bridge deck. Further deterioration in the transverse joints could be ongoing due to the repetitive vehicle loading on the compromised composite girder. Vibrations and exposure of the cracked joints to moisture and weather could worsen these conditions. Catastrophic failure of the bridge could occur if the deterioration issues were not observed and addressed in a timely manner. This study concludes by providing recommendations for design considerations to improve bridge performance, extend service life, and prevent such failures.Practical ApplicationsThe collapse of the Mexico City Metro Overpass killed 23 people and injured many others and inspired this study. The system used in this bridge is a composite plate girder with full-depth precast concrete (FDPC) deck, a recent system that allows rapid construction. The best way for engineers to prevent repeating these accidents is to understand the factors that lead bridges to fail. This study starts by exploring the causes of failure in bridges when focusing on the expected deterioration effects in the long run. Simulation techniques are employed to build a model for a bridge that is similar to the system that collapsed in the Mexico City Metro Overpass. It was used to understand the factors that led to the collapse under the moving train load. The results showed that adhering to current design codes and guidelines is not sufficient to prevent the failure of a bridge. This is a serious issue, because the codes are expected to provide the minimum requirements that guarantee the safety of structures during their service life. Therefore, this study concludes by providing recommendations for design considerations to improve bridge performance, extend service life, and prevent such failures.