טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentGrisaro Hezi
SubjectEffect of a Rear Face Protective Layer on Scabbing in Walls
of RC Protective Structures
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Avraham Dancygier
Full Thesis textFull thesis text - English Version


Abstract

A protective barrier can suffer internal damage due to external impact even if it is not breached. This phenomenon is known as ”spalling”. An important aspect in the design of protective structures is minimization of the spalling phenomenon at the protected faces of its walls. One way to solve this design aspect is to attach a protective steel sheet,  to the rear face of a protective barrier. The available experimental data of targets with a rear steel plate are very limited. The main objective of the current research is to investigate the available models, methods and experimental data and propose tools for the design of such targets. The models presented here focus on the impact of a non-deformable projectile, which is common in impact problems.

The first part of the present work proposes a model to assess the perforation resistance of a composite RC barrier with a rear steel liner to an impact of a non-deforming projectile. The model uses an integration of existing perforation models for steel and for concrete and it shows very good agreement with available experimental results. The proposed calculation procedure enables evaluation of a concrete thickness reduction factor of a composite barrier compared to a bare RC barrier. It also enables examination of alternative design solutions according to the various resistance levels that are predicted by the model. The other part of the present work presents a model to predict the residual deformation of a rear steel plate connected by stud bolts to the concrete target. The model is based on representation of the decoupled steel response of the rear liner to the impact of the ejecting concrete fragments by an SDOF equivalent system. Predictions of the proposed model show good agreement with published experimental results.  Allowable deformation, serve as a reference for design curves that consist of combinations of minimum steel and concrete thicknesses and are based on the proposed model. The proposed simplified model has been compared with full numerical simulations. It is shown that the simplified model requires much less CPU time than the simulations to reasonably predict deformations of the steel liner.

The current work proposes new approaches and simplified models to quantitatively predict the perforation limit and the residual deformations of a rear steel plate used in RC barriers. The parameters predicted by the suggested models will be an important factor in the design of new protective structures.