The FAILNOMORE project – Practice‐oriented design recommendations against progressive collapse in steel and steel‐concrete buildings

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Steel frames subjected to a column removal typically exhibit a complex load resisting mechanism characterised by three contributions: i) beam yielding mechanism, ii) compressive arch, and iii) catenary action. The development of compressive arch actions in the beams bridging over the lost column has not been yet thoroughly investigated in steel frames, although such effects proved to significantly contribute to the collapse‐resistance of reinforced concrete frames.This paper aims at shedding light on the compressive arch actions of steel beams in case of column removals accounting for various boundary conditions. Numerical and analytical methods were employed for quantifying the contribution of these effects to the structural robustness of steel frames. A simplified analytical model that allows estimating the magnitude of arching effects in steel beams with various types of end‐connections and horizontal restraints provided by the surrounding structure was introduced. The agreement between numerical and analytical results suggests that the proposed analytical model allows for accurate predictions. This validates the model's use for practical applications and gives promising prospects for its inclusion in consistent analytical methods for predicting the activated alternative load path in steel frames subjected to a column loss scenario.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Compressive arch action in beams of steel frames subjected to a column loss

Golea,

Vermeylen,

Jaspart

et al. 2023

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“…The "indirect" robustness (and progressive collapse resistance) resulting from seismic design is however limited to the members of the lateral load resisting system. When the local damage affects elements of the gravity-load resisting system, which are generally connected using shear connections, the damage may propagate and ultimately lead to disproportionate collapse [3]. The consideration of progressive collapse in a non-seismic part of the structure, or in a non-seismic resistant structure may therefore involve the use of connections with flexural capacity (partial or full).…”

Section: Introductionmentioning

confidence: 99%

“…In addition, there is a significant contribution of the concrete floor slabs to the structural robustness. When the slabs are adequately connected to the steel beams, so developing a composite action, they have a positive benefit (beam mechanism / arching effect / catenary effect) [3], also reducing the local demands in beam-tocolumn connections. When properly proportioned, the slab-beam interaction and level of continuity at beam-tocolumn connections (flexural, axial) can enhance the overall performance of the structure and increase the progressive collapse resistance.…”

Section: Introductionmentioning

confidence: 99%

“…Even though the problems related to the progressive collapse present a great risk for the building safety, there are still limited design procedures in the field of structural robustness. The FAILNOMORE project [3], which aimed to improve the robustness of structures against natural and man-made disasters, has provided valuable documentation on the use of steel and composite structures and enhancing structural performance. It presented the potential benefits of composite structures in improving safety and resilience, particularly against extreme loading conditions.…”

Section: Introductionmentioning

confidence: 99%

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The influence of the steel beam‐concrete slab interaction on the robustness capacity of steel frames

Jakab,

Dinu,

Neagu

et al. 2023

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Seismic resistant multistorey steel frames are expected to mitigate progressive collapse even when subjected to extreme loading events. The use of high redundant structural systems and ductile members and connections are key features that provide such structural robustness. The composite action between the steel beam and the concrete slab may also help increasing the robustness, but in practice it is difficult to quantify this contribution if the joint behaviour is not detailed. The paper presents the results of a numerical study that aimed to investigate the contribution of the composite action to the progressive collapse resistance of steel frame structures. The main parameters investigated in the study were the level of the composite action in beams and strength and stiffness properties of beam‐to‐column joints. The numerical model was calibrated using two reference experimental column loss tests, one with steel beams and one with composite beams. The model considers the interaction between the steel beams and concrete slab by means of shear studs and reinforcement detailing. The results showed that the contribution of the slab lessens the demands on the joints when compared with bare steel systems and provides and adequate behaviour at large deformation stage. The progressive collapse resistance may be further controlled by means of joint flexural and axial strengths.

Robustness evaluation and design of steel and steel‐concrete buildings according to current standards and recent research results

Candeias,

Obiala,

Demonceau

et al. 2023

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In terms of mitigation of progressive collapse, structural robustness is a specific safety consideration, which requires particular attention from all professionals involved in the construction industry, including architects, designers and constructors. The design of buildings considering robustness has evolved considerably over the last two decades, during which different research activities have been developed, leading to new methods and design processes. These practice‐oriented methods and concepts have been recently summarized in a design manual prepared in the framework of the FAILNOMORE RFCS project (grant No 899371), providing to the designer a general design strategy for robustness based on these methods as well as easy to follow worked examples. The proposed design strategy allows to ensure the global stability and the mitigation of progressive collapse of steel and composite structures when subjected to exceptional events, such as vehicle impact, explosion, cascading events involving localized fire or events which are not explicitly specified in the typical structural design process. In this paper, the application of these recommendations is demonstrated by means of realistic worked examples. Typical steel and steel‐concrete composite office buildings, designed according to the current European standards, are evaluated for robustness against identified and unidentified threats. The results obtained with simple and more advanced verification approaches are compared, and possible solutions to improve the robustness of the structures are provided.