Jean-François Demonceau

Robustness of steel and composite buildings suffering the dynamic loss of a column

Abstract In case a vehicle impacts a building frame, one or several columns may be damaged or even completely destroyed. Nowadays, it is a concern to mitigate the risk of progressive collapse of the whole structure further to such a localised exceptional event. Although this robustness requirement is part of several design codes, very few precise practical guidelines are provided, especially as far as dynamic failures are concerned. This paper focuses on building frames suffering the loss of one internal column. The dynamic response is more specifically investigated, with the aim to understand this behaviour in order to eventually derive simplified procedures for robustness assessment. This paper first briefly presents the main previous achievements relate d to the prediction of the static response of a plane frame suffering a column loss. The investigations into the dynamic behaviour are then summarised, which constitute the core topic of the paper. For the sake of simplicity, the dynamic response is described using a basic substructure that was proved to show many similarities in behaviour with a global frame that looses a column. A simplified model is finally developed for the prediction of the considered system’s dynamic response.

Behaviour of single sided composite joints at room temperature and in case of fire after an earthquake

In 2003, a European research program entitled “PRECIOUS-Prefabricated composite beam-to-concrete filled tube or partially reinforced-concrete-encased column connections for severe seismic and fire loadings” and funded by the Research Fund for Coal and Steel (RFCS) was initiated for three years (Bursi et al., 2008). The objective of this project was to develop fundamental data, design guidelines and prequalification tools for two types of composite beam-to-column joints able to ensure a suitable behaviour during an earthquake and its eventual subsequent fire. At the University of Liege, as part of this project, analytical and numerical investigations were conducted mainly on single-sided beam-to-column composite joints at room and at elevated temperatures. The present paper summarizes the activities developed within this project and presents the main achievements.

How can a steel structure survive to impact loading? Numerical and analytical investigations

Abstract: Recent events such as natural catastrophes or terrorism attacks have highlighted the necessity to ensure the structural integrity of buildings under exceptional events. For more than 10 years, the University of Liege is strongly involved in researches further investigating the response of structures to such exceptional events [1, 2]. The present paper gives a global overview on recent or on-going developments performed at the University of Liege in the field of robustness of steel building structures subjected to impact loading leading to the loss of a column. The conducted studies are founded on a combination of experimental, numerical and analytical approaches with the final aim to propose simplified procedures useful for practitioners and allowing ensuring an appropriate level of robustness to structures for the considered scenario.

Robustness of steel building structures following a column loss

The present paper gives a global overview on recent developments performed at Liege University in the field of robustness of building structures for the specific scenario “loss of a column”. In particular, the static non-linear response of a steel building structure following a column loss will be first presented and then, a global overview of some recent achievements and ongoing researches will be given with the global strategy aiming at deriving design requirements for practitioners.

Experimental and analytical investigations on the response of structural building frames further to a column loss

Recent events such as natural catastrophes or terrorism attacks have highlighted the necessity to ensure the structural integrity of buildings under exceptional events. Design requirements are proposed in some codes but are generally not satisfactory. In particular, it is not demonstrated that, even if these requirements are respected, a structure subjected to an exceptional event will really behave properly. A European RFCS project called Robust structures by joint ductility has been set up in 2004, for three years, with the aim to provide requirements and practical guidelines so as to ensure the structural integrity of steel and composite structures under exceptional events through an appropriate robustness. The investigations performed at the University of Liege, as part of this European project, are mainly dedicated to the exceptional event loss of a column in a steel or steel-concrete composite building frame; the main objective is to develop a simplified analytical procedure to predict the frame response further to a column loss. The development of this simplified procedure is detailed in two complementary PhD theses: the thesis of Demonceau J.-F. and the thesis of Luu N.N.H. Present paper describes experimental and analytical studies carried out in [Demonceau, 2008]. In particular, a simplified analytical procedure for the prediction of the global frame response when significant membrane forces develop further to a column loss will be described; it allows: (i) to predict the development of the catenary action in a frame with joints subjected to combined bending moment and tension loads and (ii) to compute the requested rotation capacity at the joint level according to the loads applied on the frame.

Recent investigations on composite sway frames

Abstract A modern design code for composite construction such as Eurocode 4 limits its scope to “non‐sway buildings” with efficient bracing systems. Therefore it gives mainly rules to analyse and to check structural elements like beams, columns, slabs and joints. However, in the last years, the construction of taller buildings and larger industrial halls without wind bracing systems is susceptible to make global instability a relevant failure mode, what is not yet covered by Eurocode 4. For three years, in the framework of a European research project funded by the European Community for Steel and Coal (ECSC), in which Liege University was deeply involved, intensive experimental, numerical and theoretical investigations have been carried out. The latter aimed at improving the knowledge in the field of sway composite frames and at developing appropriate design rules. The rotational behaviour of the beam‐to‐column composite joints is one of the key aspects of the problem to which a special attention has been...

On the Robustness of Earthquake-Resistant Moment-Resistant Frames: Influence of Innovative Beam-to-Column Joints

Received: October 1, 2017 Revised: November 1, 2017 Accepted: December 1, 2017 Abstract: Background: The deformation capacity of beam-to-column connections strongly influences the robustness of earthquake-resistant Moment Resistant Frames (MRFs) when subjected to a loss-of column scenario. As a consequence, with the aim of foresee the structural response up to the failure, an accurate modelling of the ultimate behaviour of the joints is needed.

PRELIMINARY STUDY ON BEAM-TO-COLUMN JOINTS UNDER IMPACT LOADING

Received: October 1, 2017 Revised: November 1, 2017 Accepted: December 1, 2017 Abstract: Background: Recent catastrophic events have pointed out the need to ensure the integrity of structures under “exceptional” events. Since many years, the University of Liège is involved in different activities and projects related to the robustness assessment of structures. The robustness of a structure is the ability of the system to remain globally stable after events not directly accounted for in the design, like impact, fire or consequences of a human error, which should lead to a reasonable damage when compared to the original cause.

Preliminary Finite Element Analyses on Seismic Resistant FREE from DAMage Beam to Column Joints under Impact Loading

Nowadays, the interest on structural robustness is increasing because of the recent terroristic attacks. Although a large number of research projects have been carried out in this field, limited design guidelines as well as code recommendations are nowadays available. Leading to the fact that the design for robustness is far from being current practice. Conversely, the design for natural hazards as the earthquake is a well-consolidated practice and modern codes implement effective and well-recognized design rules. Even though seismic design philosophy based on the concept of hierarchy of resistance enables structural robustness for conventional structural systems, this is not demonstrated for structures equipped with anti-seismic devices as well as innovative dissipative systems. Recently, the use of friction based dissipative joints has been proved to be a promising solution for seismically design steel moment resisting frames. However, the robustness and the resistance against impact loading of this type of joints is not yet investigated. With the aim to develop an experimental campaign based on impact tests, preliminary finite element analyses have been carried out to identify the main criticisms and to drive the rational design of the joint specimens. With this regard, in the present paper, the results of a numerical parametric study on the preliminary push-down test are presented and discussed.

Composite joints under M-N at elevated temperatures - Experimental investigations and analytical model

The Eurocodes recognise robustness as a way to ensure the structural integrity of a building frame subjected to an unforeseen event and therefore to avoid a so-called “progressive failure” mode in extreme loading situations. However few practical guidelines exist nowadays which would allow a designer to design a structure accordingly. Within the European RFCS ROBUSTFIRE project, the behaviour of steel and composite car parks subjected to localised fire leading to a column loss was investigated. Under such a scenario, the beam-to-column joints play a key role in the global structural response. Indeed, these joints, initially loaded in bending, may be subjected to elevated temperatures and to combined axial load “N” and bending moment “M”. In this paper, a methodology to predict the mechanical response of bolted composite beamto-column joints at elevated temperatures under M-N is presented and validated through comparison to experimental tests conducted at the University of Coimbra.