Progressive collapse: the case of composite steel-concrete frames

Residual strength and alternate load paths are two fundamental design strategies to ensure adequate resistance against progressive collapse of structures. This paper presents an experimental study carried out on two full-scale steel and concrete composite frames to investigate their structural behaviour in case of a column collapse. The study focusses on the redundancy of the structure as provided by the beam-slab floor system as well as by the ductile beam-to-column joints. The specimens were ground floor sub-frames ‘extracted’ from two reference buildings designed in accordance to the Eurocodes. The frames have the same overall dimensions, but a different, symmetric and asymmetric, configuration of the column layout. In both tests, the collapse of an internal column was simulated. The paper presents the main features of the frames and the principal outcomes of the test on the symmetric frame

Steel-concrete frames under the column loss scenario: An experimental study

Accidental events, such as impact loading or explosions, are rare events with a very low probability of occurrence. However, their effects often lead to very high human losses and economic consequences. An adequate design against these events should reduce the risk for the life of the occupancy, minimize the damage extension and enable a quick rebuilding and reuse. A structure fulfilling these requirements is ‘robust’. Different strategies can be pursued for accidental events, and among them, methods based on the residual strength or the alternate load path are frequently adopted because applicable to a vast range of structures. Adequate design strategies based on them require an in-deep knowledge of load transfer mechanisms from the damaged to the undamaged part of the structure. As to the frames, the important role of joint ductility was pointed out in recent studies. Besides, the flooring systems substantially affect the spread of the damage, but the research on this subject is still very limited. The present study focuses on steel-concrete composite frames under the column loss scenario. It aims to better understand the influence of both frame continuity and floor systems in the development of 3D membrane action. Two geometrically different 3D steel-concrete composite full-scale substructures were extracted from reference buildings and tested simulating the column collapse scenario. This paper illustrates the preparatory studies, the main features of the specimens and the outcomes of the first test. The test provided an insight in the need for an enhanced design of joints and pointed out the key features of the response of the floor system

Lateral Loading Response of CFS Framed Shear Wall with Cement Board Panels

Shear wall panels are commonly used as lateral load resisting elements to provide stability of the cold-formed steel-framed houses in Australia against wind and earthquake actions. The effectiveness of their lateral resistance behavior is obtained usually by experimental testing although it can also be done by analytical modeling. This paper presents racking test results of steel-framed wall panels with different aspect ratios sheathed with fibre cement board subjected to monotonic and cyclic loading protocol. Performance parameters of the wall panels are obtained from the experimentally observed load-deflection curves using various existing methods and evaluation method is proposed. The evaluation method considers various performance characteristics including ductility modification factor, residual displacement recovery and load levels satisfying ultimate and serviceability limit state conditions

Robustezza Di Sistemi Intelaiati Misti Acciaio-Calcestruzzo: Il Caso Di Collasso Di Una Colonna // Robustness Of Framed Steel-concrete Composite Systems: The Case Of A Column Collapse

Negli ultimi anni, la ricerca di soluzioni costruttive finalizzate alla mitigazione dei danni causati da eventi eccezionali ha suscitato un grande interesse da parte della comunità scientifica internazionale. Tali azioni possono essere fronteggiate sia attraverso criteri di sovraresistenza che di ridondanza strutturale e la combinazione di questi criteri può portare alla definizione di metodi di progetto efficaci ed economicamente efficienti. Uno dei principali obiettivi delle strategie di intervento è quello di realizzare sistemi strutturali in grado di attivare meccanismi di ridistribuzione dei carichi in modo che questi possano essere trasferiti, dalla parte danneggiata alla parte non danneggiata della struttura. Il lavoro svolto fa parte di un Progetto di Ricerca Europeo che ha l'obiettivo di definire nuovi criteri di progetto per strutture miste acciaio-calcestruzzo nei confronti di azioni eccezionali. La prima parte della ricerca si concentra sul comportamento di due telai 3-D nei confronti del collasso di una colonna interna. Due prove a scala reale saranno eseguite su una parte di queste strutture. Simulando il collasso completo di una colonna sarà possibile studiare la ridondanza del sistema tridimensionale fornito dalla soletta attraverso l'attivazione delle forze membranali. Il presente articolo illustra lo studio preliminare condotto in fase di progetto delle prove. // The last years were characterized by a growing interest about the development of strategies for the mitigation of the damages caused by accidental events. Accidental actions can be resisted by residual strength and alternate load path methods and combination of these strategies can lead to an effective and cost efficient design procedure for progressive collapse mitigation by redistributing the loads within the structure. One of the main objective of these strategies is the development of structural systems able to activate mechanisms to transfer the loads from the damaged to the undamaged part of the structure. This paper illustrates the preliminary work carried on within a European Research Project, aimed at developing new design concepts for steel-concrete composite frames against accidental actions. The first part of the study investigates the behavior of two geometrically different steel-concrete 3-D composite frames subjected to the loss of an internal column. Two full-scale experimental tests will be performed on a part of these structure. By simulating the total loss of the impacted column, the experiments enable investigation of the redundancy of the 3-D slab system in terms of activation of membrane effects. The present paper presents the preliminary study for the design of the tests

Robustness of steel-concrete flooring systems - An experimental assessment

Recently, the interest in the mitigation of the damages caused by accidental events increased significantly. The knowledge of loads transfer mechanisms from the damaged to the undamaged part of the structure is the key for developing adequate design strategies. Despite the potential important role of flooring systems, research of this subject is still limited. A European Research Project aims at achieving an insight into the case of steel-concrete composite frames with solid concrete slabs. Two geometrically different 3D composite sub-frames are subjected to the loss of an internal column. The sub-frames are a full-scale portion of 5 stories 3D frames. Equivalence between the sub-frames and the full-frames required a series of careful numerical analysis, which enabled definition of the boundary restraints of the specimens and of the loading sequence in the test. The present paper illustrates these preparatory studies and gives some preliminary information about the outcomes of the first test. Robustheit von Verbunddecken – Eine experimentelle Bewertung. In den letzten Jahren ist das Interesse an der Begrenzung von durch Unfälle bedingten Schäden gewachsen. Die Kenntnis der Lastübertragungsmechanismen von den beschädigten zu den unbeschädigten Tragwerksteilen ist der Schlüssel zur Entwicklung geeigneter Bemessungskonzepte. Trotz der wichtigen Erkenntnis über den Einfluss der Deckenwirkung stehen keine ausreichenden Forschungsergebnisse zu dieser Thematik zur Verfügung. In einem europäischen Forschungsprojekt werden Tragsysteme aus Verbundrahmen mit Stahlbetonplatten untersucht. Dabei werden zwei geometrisch unterschiedliche 3D-Versuchsrahmen auf die extreme Annahme eines Stützenausfalls untersucht. Die Versuchsrahmen sind vollmaßstäblich ausgebildet und repräsentieren den unteren Teil des Rahmentragwerks eines fünfstöckigen Gebäudes. Die Auflagerbedingungen und die Belastungssequenzen der Versuchsrahmen wurden durch zahlreiche numerische Untersuchungen ermittelt, um denjenigen des Rahmensystems vom Gebäude zu entsprechen. Der vorliegende Beitrag zeigt diese Vorstudien und berichtet über einige experimentelle Ergebnisse aus dem ersten Versuch

Robustness of Moment Resisting Steel-Concrete Composite Frames: The floor resisting mechanism in the case of column collapse

This paper illustrates the preliminary work carried on within a European Research Project, aimed at developing new design concepts for steel-concrete composite frames against accidental actions. Accidental actions can be resisted by residual strength and alternate load path methods. Combination of these strategies can lead to an effective and cost efficient design strategy for progressive collapse mitigation by redistributing the loads within the structure. The first part of the study investigates the behavior of two geometrically different steel-concrete 3D composite frames subjected to the loss of an internal column. Two full-scale experimental tests will be performed on a part of the structure, and the present paper presents the preliminary studies for the design of the tests. By simulating the total loss of the impacted column, the experiments enable investigation of the redundancy of the 3D slab system in terms of activation of membrane effects. Another important structural resource is the redundancy of the global structure through ductile joint design; this is a further major issue investigated by the project

Moment resisting steel-concrete composite frames under the column loss scenario: design of an experimental study

Robustness is a very topical research issue, and several research work have been carried out in recent years. The University of Trento was involved in the project‘Robust impact design of steel and composite building structures’ (acronym ROBUSTIMPACT). The project was financially supported in the framework of the European RFCS program (Research Fund for Coal and Steel). This document concerns the experimental activities carried out at the Laboratory of Material and Structural Testing (LMST) of the University of Trento. The project focuses on the behaviour of composite steel and concrete framed buildings subject to accidental actions. Within the project, several experimental analyses were performed by the partners, ranging from the local to the global response. As to the global behaviour, at LMST two 3D full-scale tests on steel-concrete composite sub-frames simulating the total loss of an impacted column were performed. The purpose of the study is to improve the state of knowledge on the contribution offered by the joints and by the 3D slab system in terms of activation of an alternative mechanism of resistance. The research assumes two reference case studies of steel and concrete five-story buildings differing for in-plane column layout. Two sub-frames were ‘extracted’ from these structures and tested in the laboratory. The plan of the experimental tests required preliminary studies devoted to: selection and definition of a reference buildings assumed as case studies; design of the reference buildings according to the Eurocodes; identification of representative substructures (slab-beam system, columns and joints) from the reference structures to be experimentally investigated; design of the testing set-up. This report concern the design of the case studies, of the specimens and of the testing set-up. In particular, Section 2 illustrates the design, based on the relevant Eurocodes, of the reference structures for both the geometric configurations. Section 3 reports the design of the sub-structures including also the numerical analysis and the design of the testing setup. Finally, Section 4 provides the details of the components of the two specimens as needed for their fabrication, and of the testing set-up. All the related drawings are reported in Annexes A-C

Steel and steel-concrete composite structures in seismic area: advances in research and design. The Research Project RP3 of the ReLUIS-DPC 2014-2018. Activity carried out during years 2014-2016

This book collects the main outcomes of the research activity carried out within the line “Steel and Steel-Concrete Composite Structures” of the ReLUIS project 2014-2016 (Italian Civil Protection research project), which was chaired by Raffaele Landolfo and Riccardo Zandonini. Ten research units were involved in the scientific programme coming from the following Universities: Napoli “Federico II”, Salerno, Pisa, Sannio, Marche, Campania “Luigi Vanvitelli”, Chieti-Pescara “G. d’Annunzio”, Trento, Trieste and Genova. The research line was mainly devoted to the development of innovative approaches for the design of steel and steel-concrete composite buildings. Starting from the outcomes achieved during the previous ReLUIS project, novel results were obtained in the last years that are herein presented considering the four main investigated area, which are: steel and steel composite beam-to-column joints, conventional steel and steel-composite buildings, non-conventional steel buildings, steel and steel-composite bridges