۱- Introduction

۲- Finite element model of steel frame

۳- Finite element model validation

۴- Massive explosion scenario inside a building

۵- Comparison of the existing analytical methods about progressive collapse

۶- Substructure method

۷- Conclusion

References

Abstract

As a massive explosion happens inside a building, a number of structural members (columns, beams, slabs and so on) are damaged or failed, along side with non-zero initial conditions (displacement, velocity, acceleration and so on), and the progressive collapse of the building structures is most likely to occur. However, limited research works about blast load effect of structural members inside a building can be found. In view of this, based on the substructure model, a new method for progressive collapse analysis of steel frames under blast load is proposed. First, the massive explosion scenario inside a building is introduced. Then, the substructure model within effective areas of blast influence is established. After that, the calculation method of non-zero initial conditions and initial damage for structural members is given, and finally the specific steps of the proposed method are described. By way of example of a steel frame with 5 stories in height, 4 bays in the longitudinal direction, 3 bays in the transverse direction, direct simulation method, alternative load path method and proposed method are all employed to simulate the progressive collapse process, respectively. Through the example analyses, it is shown that blast load effect of structural members cannot be ignored on the ground floor, and it can be ignored on the other floors by the effect of the reinforced concrete slab. The non-zero initial conditions and initial damage of structural members can be predicted well by the substructure model, and the proposed method is also reliable and accurate.

Introduction

In recent years, with the soaring urban population and the tightening supplies of land resources, land prices are rising sharply, which provides a vast development prospect and an infinite market potential for mushroom development of super-tall buildings. High-rise civil buildings and large-scale mixed-use buildings are constantly emerging, and developing towards large-scale, complexity and diversification. In the long service life, the building structures may encounter different types of accidental disasters, such as an extremely rare earthquake, vehicle or aircraft impact, gas explosion, bomb attack, human error, fire and so on. It brings indelible potential risk to the building structures. With the constant progress of the society and the sustainable development of the economy, natural and man-made disasters that occur suddenly with great destruction emerge in endlessly. As a special type of disaster, the explosion enters into our daily life. Taking into account the peculiarity of blast load, the dynamic response characteristics and failure modes of the structural members become very complicated, especially in the case of a massive explosion inside the building. A number of structural members (columns, beams, slabs and so on) are damaged or failed, along side with non-zero initial conditions (displacement, velocity, acceleration and so on). It has become an important and hot topic, and the researchers and engineers make greater efforts in this connection.