COMPUTATIONAL ASSESSMENT OF STEEL-JACKETED BRIDGE PIER COLUMN PERFORMANCE UNDER BLAST LOADS

Open Access
Author:
O'Hare, Edward Vincent
Graduate Program:
Civil Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 08, 2011
Committee Members:
  • Dr Daniel G Linzell, Thesis Advisor
Keywords:
  • Computational
  • Bridge Column
  • Blast
  • Steel Jacket
Abstract:
Due to recent malicious acts on civil structures, bridge blast resistance has become a subject of extreme interest from both research and design perspectives. Bridge engineers have a unique challenge when considering security during design due to the valuable role that our country’s infrastructure provides with respect to safety and commerce coupled with the inherent vulnerability that exists. Summarized herein is research focusing on the use of a steel jacket retrofit for circular, reinforced concrete, bridge columns to increase their resistance against blast loads. A computational parametric study utilizing LS-DYNA was performed to investigate column blast performance to establish critical failure modes and levels of parameters that provide protection against these failures. Finite element models were created using constitutive models for concrete, steel jackets and steel reinforcement that have been evaluated at high strain rates in the literature and have shown favorable results compared to experimental tests. Elemental constraints were evaluated to correctly represent the interaction between concrete and steel. Critical parameters including: aspect ratio, transverse reinforcement ratio, steel jacket thickness ratio and steel jacket gap ratio were varied using a 2k factorial design process evaluated at minimum and maximum limits achieving sixteen parametric models. The blast load was defined by scaled distance that remained constant throughout the parametric study and was applied using the Conventional Weapons (CONWEP) functions that are imbedded into LS-DYNA. CONWEP is considered coupled with the structure and is capable of accounting for incident and reflective blast waves. Models were validated using theoretical and experimental data to ensure proper static and dynamic column behavior. Direct shear, flexure and transverse shear failure modes were evaluated through selected result parameters. Results were used to observe if steel jackets can be detailed to improve retrofitted column blast performance and to provide guidance for designers that would choose this as a retrofit option.