Failure Mechanisms and Parameters of Elastoplastic Deformations of Anchorage in a Damaged Concrete Base under Seismic Loading

The article addresses mechanisms of anchorage failure in a concrete base studied within the framework of physical experiments. The authors investigated the most frequently used types of anchors, such as the cast-in-place and post-installed ones. The anchorages were studied under static and dynamic loading, similar to the seismic type. During the experiments, the post-earthquake condition of a concrete base was simulated. Within the framework of the study, the authors modified the values of such parameters, such as the anchor embedment depth, anchor steel strength, base concrete class, and base crack width. As a result of the experimental studies, the authors identified all possible failure mechanisms for versatile types of anchorages, including steel and concrete cone failures, anchor slippage at the interface with the base concrete (two types of failure mechanisms were identified), as well as the failure involving the slippage of the adhesive composition at the interface with the concrete of the anchor embedment area. The data obtained by the authors encompasses total displacements in the elastic and plastic phases of deformation, values of the bearing capacity for each type of anchorage, values of the bearing capacity reduction, and displacements following multi-cyclic loading compared to static loading. As a result of the research, the authors identified two types of patterns that anchorages follow approaching the limit state: elastic-brittle and elastoplastic mechanisms. The findings of the experimental research allowed the authors to determine the plasticity coefficients for the studied types of anchors and different failure mechanisms. The research findings can be used to justify seismic load reduction factors to be further used in the seismic design of anchorages.

Investigation of SiC Trench MOSFETs’ Reliability under Short-Circuit Conditions

In this paper, the short-circuit robustness of 1200 V silicon carbide (SiC) trench MOSFETs with different gate structures has been investigated. The MOSFETs exhibited different failure modes under different DC bus voltages. For double trench SiC MOSFETs, failure modes are gate failure at lower dc bus voltages and thermal runaway at higher dc bus voltages, while failure modes for asymmetric trench SiC MOSFETs are soft failure and thermal runaway, respectively. The shortcircuit withstanding time (SCWT) of the asymmetric trench MOSFET is higher than that of the double trench MOSFETs. The thermal and mechanical stresses inside the devices during the short-circuit tests have been simulated to probe into the failure mechanisms and reveal the impact of the device structures on the device reliability. Finally, post-failure analysis has been carried out to verify the root causes of the device failure.

Flexural Behaviour of Different Stiffener Section Area on Full Height Rectangular Opening Castellated Steel Beam

Vierendeel is one of failure mechanisms in a castellated steel beam. Vierendeel mechanism is the main failure that occurs in a full high rectangular opening castellated beam. Vierendeel decrease castellated flexural capacity compare to the original wide flange section beam. One solution to prevent the vierendeel mechanism is by installing a diagonal stiffener in form of a steel bar on a castellated beam. The research’s purpose is finding the effect of different size of steel bar diameter on the flexural capacity. Four different sizes of steel bar diameter used in this research: 10 mm, 12mm, 16 mm, and 19 mm. Castellated beam flexural capacity is analysed with the method of truss analysis and pushover analysis. This study shows it can be infer that the bigger size of steel bar diameter does not always determine the higher flexural capacity of the castellated beam. Optimum value of the beam’s flexural capacity is affected by the strength of the flange section. The largest increment of flexural capacity between original wide flange compare to the castellated beam is 139.4% by using 16 mm diameter of the diagonal stiffener.