Keywords: progressive collapse potential, seismic design, low-rise buildings, demand capacity ratio.

In this paper results concerning the progressive collapse potential of low-rise reinforced concrete structures are presented. Low-rise structures with three and six floors were designed according to the provisions of Eurocode 2 [1] and P100-1/2006, the active Romanian Seismic Code [2], for a low and a high seismic zone. The particular behaviour of low-rise buildings in comparison with similar located mid-rise buildings is discussed.

Applying four damage scenarios, as specified in the GSA (2003) Guidelines [3], demand capacity ratio (DCR) values for flexure are computed for each model. The main objectives of the study and corresponding findings are presented as follows:

1. The effect of prescribed damage scenarios on progressive collapse potential:
   • For a given model, the magnitude of maximum inelastic demands only slightly differs when different "missing column" scenarios are considered, and consequently, the final conclusion concerning the risk level was the same;
   • This finding is original and highly valuable because, on its basis, the final conclusion regarding the progressive collapse potential of a building could be drawn by investigating only one damage scenario instead of four.
2. The general progressive collapse behaviour of low-rise reinforced concrete framed structures versus mid-rise structures:
   • Low-rise buildings present a higher risk of progressive collapse compared to mid-rise buildings.
3. The influence of the floors number on the robustness of low-rise structures:
   • The robustness of low-rise buildings located in low seismic zones is not significantly affected by the number of storeys;
   • On the contrary, if the building is designed for a high seismic zone, its robustness strongly depends on the number of floors;
   • The progressive collapse risk decreases when the number of stories increases.
4. The influence of the seismicity of the area:
   • For the first time in the technical literature, the paper illustrates in a quantitative manner, differentiated with respect to the number of storeys, the positive effect of seismic design and detailing on the progressive collapse resistance of reinforced concrete framed structures.

1

SR EN 1992-1-1: 2004, "Eurocode 2: Design of Concrete Structures - Part 1-1: General Rules and Rules for Buildings", ASRO, Bucharest, 2004. (in Romanian)

2

P100-1/2006, "Seismic design code - Part I: Design Rules for Buildings", MTCT, Bucharest, 2006. (in Romanian)

3

U.S. General Service Administration, "Progressive Collapse Analysis and Design Guideline for New Federal Office Buildings and Major Modernisation Projects", Washington D.C., June 2003.

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