On the Assessment of the Plaka Bridge Collapse Using Non-Linear Analysis Preventable or Doomed?

Abstract

The collapse of the historic Plaka Stone Bridge due to extreme flooding and in particular the pinpointing of the causes or possibly weak structural points that led to the structural failure is studied using high fidelity, three-dimensional non-linear numerical analysis and sensitivity studies. Specifically, the potential of a number of postulated scenarios in initiating failure and leading to the eventual collapse of the bridge are explored aided by sensitivity analyses relying on non-linear finite element modelling and is augmented by actual material properties of the structural elements deduced from laboratory tests following the collapse (i.e. stone and mortar). Presented in detail is the scenario which appears to closely replicate the mode of actual bridge failure observed (damage extend and debris distribution) and deemed by the authors to be most likely sequence of events that occurred. This scenario postulates the undermining of the central pier by support or shear section failure leading to large deformation and displacements on the lower part of the pier eventually leading to shear failure of the primary arch. Based on the failure mode predicted by simulation and corroborated with observed damage the vulnerability of the Plaka Bridge to this "beyond design basis event" even for an uncompromised structure is assessed by asking the question whether any preventive maintenance and upkeep could have saved this particular bridge or that its collapse was beyond human intervention.

Investigating Stone Masonry Arch Bridges in Greece Employing In-situ Measurements and Numerical Predictions

“…The potential of a number of postulated scenarios in initiating failure and leading to the eventual collapse of the bridge were explored aided by sensitivity analyses relying on non-linear finite element modeling, augmented by actual material properties of the structural elements deduced from laboratory tests following the collapse. More information can be found in Simos et al (2017). The numerical analysis and the failure scenario postulated and presented in detail in this study tend to support that the triggering of the collapse and the most-likely cause was the undermining by the flood (scouring of the river bed and hydrodynamic loads) of the central pier.…”

“…The lack of specific studies towards clarifying in a systematic way all these uncertainties represents a serious limitation in the numerical simulation process. The approximation adopted in this study is a process of back simulation (Manos et al 2015a(Manos et al ,2015bSimos et al 2017Simos et al , 2018. This is done by adopting values for these unknown mechanical stone masonry properties, respecting at the same time all the measured geometric details, which result in reasonably good agreement between the measured and predicted in this way eigen-frequency values.…”

“…13b). Simos et al (2017). Investigated the collapse of the Plaka Stone Bridgedue to extreme flooding using high fidelity, three-dimensional non-linear numerical analysis and sensitivity studies.…”

“…At the same location, the horizontal in-plane displacement is equal to 4.5 mm (y-y direction), whereas the out-of-plane horizontal displacement (x-x direction, flow of river) is equal to 0.87 mm. The maximum (tensile) stress response is depicted in Fig.13b and c. As can be seen, at the central arch region (Fig.13c) the maximum stress value is equal to 0.764 MPa whereas at the left relief arch region the maximum stress value us equal to 2.579 MPa (Fig.13b) Simos et al (2017)…”

Studying the Performance of Stone Masonry Arch Bridges Employing in-Situ Measurements and Numerical Predictions

“…As can be seen, at the central arch region (figure 18c) the maximum stress value is equal to 0.764MPa whereas at the left relief arch region the maximum stress value us equal to 2.579MPa (figure 18b). Simos et al (2017). Investigated the collapse of the Plaka Stone Bridge due to extreme flooding using high fidelity, three-dimensional non-linear numerical analysis and sensitivity studies.…”