DYNAMIC RESPONSE ANALYSIS OF CONCRETE STRUCTURES: SIMPLIFIED DESIGN METHOD AND ITS LIMITATIONS

The behaviour of dynamically loaded structures, like concrete containment structures and blast resistant control buildings, can be analysed with advanced numerical techniques as well as with less laborious engineering methods. Most used simplified method is the Single Degree of Freedom (SDOF) method, or the so-called Biggs method [1]. This paper focuses on the application of a simplified dynamic analysis using the SDOF-method for analysing a concrete protective structure under a blast loading. The structure is translated to mass and spring properties and the equation of motion is solved analytically or numerically. The key-issue for the application of the simple approach is the validity of the assumption, or simplification, that the dynamic response is governed by a single deformation mode. Especially under extreme dynamic loading conditions of impact and explosion, multiple eigenmodes are activated and the deformation mode changes in time. Depending on load duration and response time of the structure, the higher eigenmodes have to be taken into account. Fortunately in many cases the higher eigenmodes do not dominate the final failure mode and the simplified SDOF method can be applied for design or damage assessment purposes. The method is illustrated by an example of a concrete shelter submitted to an internal blast.

• ABSTRACT

• INTRODUCTION

• CALCULATION METHOD

• EXAMPLE

• CONCLUSIONS

• REFERENCES