Assessing The Load-Carrying Capacity Of RC Beams Under Impact Loading

Noosha Madjlessi, Pegah Behinaein, Demetrios M Cotsovos

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Abstract

Data obtained from drop-weight tests reveals that the response exhibited by reinforced concrete (RC) beam specimens under impact loading differs significantly from that established during equivalent static testing. This shift in structural behaviour predominantly takes the form of an increase in the maximum sustained load as well as a reduction in the portion (span) of the RC beam reacting to the imposed action which tends to concentrate around the area of impact. However, measurements obtained from drop-weight tests concerning certain important aspects of RC structural response (e.g. maximum sustained load or deflection) often correspond to a specimen physical-state characterised by high concrete disintegration in combination with low residual load-bearing capacity and stiffness. This stage of structural response has little practical significance as it depends heavily on post-failure mechanisms for transferring the applied load to the specimen supports. In view of the above, the available test data cannot provide insight into the mechanisms underlying RC structural response nor can it identify the true ultimate limit state of the subject specimens when subjected to impact loading. To achieve insight into the mechanics underlying RC structural response under impact two well established structural analysis packages (ADINA and ABAQUS) are employed in the present study. Both packages are capable of carrying out three-dimensional dynamic nonlinear finite element analysis while realistically accounting for the nonlinear behaviour of concrete and the characteristics of the problem at hand i.e. a wave propagation problem within a highly nonlinear medium. The numerical predictions obtained concerning various aspects of RC structural response are initially validated against relevant data obtained from drop-weight tests. A parametric investigation is then carried out aiming to study the dynamic response exhibited by RC beams when subjected to specific rates and intensities of impact loading. The latter investigation reveals that the true load-bearing capacity is often significantly lower than the maximum sustained load recorded experimentally. In fact, the higher the loading rate and intensity of the impact load the larger the latter difference becomes.
Original languageEnglish
Publication statusAccepted/In press - 2016
Event9th International Concrete Conference 2016 - Dundee, United Kingdom
Duration: 4 Jul 20166 Jul 2016

Conference

Conference9th International Concrete Conference 2016
CountryUnited Kingdom
CityDundee
Period4/07/166/07/16
OtherEnvironment, Efficiency and Economic Challenges for Concrete

Keywords

  • Reinforced concrete beams
  • Finite elements
  • nonlinear dynamic analysis
  • loading rate
  • Impact
  • drop-weight tests

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