Shape Function Limitations within Equivalent Single-Degree-of-Freedom Analysis for Structural Elements Subject to Blast Loading

Publication Year:
2016
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Downloads 128
Abstract Views 39
Repository URL:
https://preserve.lehigh.edu/etd/2738
Author(s):
Mullen, Evan
Tags:
Blast; SDOF; Structural; Civil and Environmental Engineering; Engineering; Structural Engineering
thesis / dissertation description
This thesis presents an investigation into the potential inaccuracies when analyzing structural elements under blast loads using equivalent single-degree-of-freedom (SDOF) systems. An equivalent SDOF system converts a continuous element into a single mass-spring-damper system, where the displacement of the mass equates to the largest deflection of the continuous element. The potential inaccuracies arise from the fact that this equivalent system uses the static deflected shape of the element. The Single-Degree-of-Freedom Blast Effects Design Spreadsheet (SBEDS) is an example of an industry accepted software package that is used for this type of simplification.To identify inaccuracies in results from SDOF methods, the results were compared to a more accurate model. This model is a multi-degree-of-freedom (MDOF) system, which is able to better represent a structural element, due to discretizing the element into smaller segments. These smaller segments are able to respond with a more realistic deflected shape when subjected to blast loading. This is more accurate than lumping all of the information about the element to a single degree of freedom.Using MATLAB, blast analysis of single structural elements were performed to replicate the corresponding results from two software packages: SBEDS (for SDOF analysis) and SAP2000 (for MDOF analysis). Once the MATLAB solutions were verified and calibrated, analyses were performed using both MATLAB scripts for combinations of input parameters, such as boundary conditions, magnitude of load, and section size. After results were obtained from these analyses, they were compared, which allowed for identification of static-shape limitations of SDOF analysis.