Abstract
Structural response of reinforced concrete (RC) elements for analysis and design are often obtained using the positive phase of the blast pressure curve disregarding the negative phase assuming insignificant contribution from the negative phase of the loading. Although, some insight on the effect of negative phase of blast pressure based on elastic single-degree-of-freedom (SDOF) analysis was presented before, the influence of negative phase on different types of resistance functions of SDOF models and on realistic finite element analysis has not been explored. In this study, the effects of inclusion of pulse negative phase on structural response of RC elements from SDOF analysis and from more detailed finite element analysis have been investigated. Investigation of SDOF part has been conducted using MATLAB code that utilizes non-linear resistance functions of SDOF model. Detailed numerical investigation using finite element code DIANA was conducted on the significance of the negative phase on structural response. In the FE model, different support stiffness was used to explore the effect of support stiffness on the structural response due to blast negative phase. RESULTS from SDOF and FE analyses present specific situations where the effect of large negative phase was found to be significant on the structural response of RC elements. © Owned by the authors, published by EDP Sciences, 2016 Language: en
Highlights
Due to the high degree of uncertainty involved in blast load prediction, complex time consuming detailed structural analysis is often not justified
In CEDAW [1], it has been indicated that the negative phase loading only affects component response when scaled pressure is high relative to scaled impulse, which corresponds to cases where the positive phase blast load durations are relatively short compared to the component response time
The results indicate that the negative phase has a significant effect when the blast waveform parameter is less than unity and becomes insignificant in contribution for the cases were that negative phase can be presented by the Friedlander equation with an α-value larger than one
Summary
Due to the high degree of uncertainty involved in blast load prediction, complex time consuming detailed structural analysis is often not justified. Single-degree-of-freedom (SDOF) analysis has the potential of giving a good prediction of final response of the critical point of a structure. All commonly used design manuals for blast loading like PDC-TR 08-07 [1] and UFC 3-340-02 [2], and widely used design tools such as Single-Degree-of-Freedom Blast Effects Design Spreadsheets (SBEDS) [3] and Facility and Component Explosive Damage Assessment Program (FACEDAP) [4], are based on the SDOF response calculation of structural components. Different support stiffness was used for the FE model to explore the effect of support stiffness on the structural response due to blast load with large negative phase. Results from both SDOF model and FE analysis are presented to establish the effect of large negative on structural response of RC elements
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