Cellular buckling in I-section struts

An analytical model that describes the interactive buckling of a thin-walled I-section strut under pure compression based on variational principles is presented. A formulation combining the Rayleigh--Ritz method and continuous displacement functions is used to derive a system of differential and integral equilibrium equations for the structural component. Numerical continuation reveals progressive cellular buckling (or snaking) arising from the nonlinear interaction between the weakly stable global buckling mode and the strongly stable local buckling mode. The resulting behaviour is highly unstable and when the model is extended to include geometric imperfections it compares excellently with some recently published experiments.Comment: 23 pages, 12 figures. Submitted for special issue of Thin-Walled Structure

Cellular buckling in stiffened plates

An analytical model based on variational principles for a thin-walled stiffened plate subjected to axial compression is presented. A system of nonlinear differential and integral equations is derived and solved using numerical continuation. The results show that the system is susceptible to highly unstable local--global mode interaction after an initial instability is triggered. Moreover, snap-backs in the response showing sequential destabilization and restabilization, known as cellular buckling or snaking, arise. The analytical model is compared to static finite element models for joint conditions between the stiffener and the main plate that have significant rotational restraint. However, it is known from previous studies that the behaviour, where the same joint is insignificantly restrained rotationally, is captured better by an analytical approach than by standard finite element methods; the latter being unable to capture cellular buckling behaviour even though the phenomenon is clearly observed in laboratory experiments.Comment: 22 pages, 9 figures, 1 table, accepted for publication. Proceedings of the Royal Society A, 201

A 10-year review of fatal community assault cases at a regional forensic pathology facility in Cape Town, South Africa

Background. An increase in autopsied community assault (CA) fatalities was observed at the Tygerberg Forensic Pathology Services (FPS), Cape Town, South Africa (SA). There is a paucity of information on the incidence and prevalence of these cases in SA.Objectives. To determine the patterns and trends of injuries sustained in so-called CA fatalities.Methods. A retrospective and descriptive study was conducted. Fatal CA cases admitted to the Tygerberg FPS over the 10-year period 1 January 2003 - 31 December 2012 were reviewed. Data were collected from autopsy/postmortem reports, contemporaneous notes, attached hospital records, the South African Police Services (SAPS) 180 form (completed by the SAPS representative) and other FPS documentation.Results. A total of 424 cases of fatal CA were seen during the study period, with an annual increase between 2003 and 2007 and a second peak in 2012. The cause of death in most cases was multiple injuries (42.0%), with blunt-force trauma being the basis of most injuries sustained. The area with the greatest burden of injury was the township of Mfuleni (73 CA deaths per 100 000 population). There was a predominance of males, with only one female fatality recorded.Conclusion. Adequate policing in prevalent areas is essential to address unnecessary loss of life and the burden imposed by these cases on the criminal justice system and healthcare services

A call to action: Temporal trends of COVID-19 deaths in the South African Muslim community

Letter by Omar on letter by Jassat et al. (Jassat W, Brey Z, Parker S, et al. A call to action: Temporal trends of COVID-19 deaths in the South African Muslim community. S Afr Med J 2021;111(8):692-694. https://doi.org/10.7196/SAMJ.2021.v111i8.15878); and response by Jassat et al

A call to action: Temporal trends of COVID-19 deaths in the South African Muslim community

No abstract