39,749 research outputs found
Recent advances and experimental findings on the structural behaviour of an innovative dry-assembled precast concrete wall system
No full textThe paper presents the evolution of the research related to the structural behaviour of an innovative dry-assembled precast concrete wall system named Domus® performed over the last 10 years. This system is made with hollow bearing walls which can be fully prefabricated and assembled in-situ through dry joints. The wall element, named Master®, has been experimentally tested under simulated earthquake loadings as a bracing wall into a full-scale 3-storey precast building prototype with regard to its flexural performance within the framework of the Safecast (FP7-SME-2007-2 with GA 218417/2009) European research project. The preliminary results of a recent test programme concerning the mechanical characterisation of (a) the shear behaviour of a single wall modulus, which is peculiar due to the presence of the hollow cavities and of the discrete mechanical wall-to-wall (or foundation) vertical connections, and (b) the shear behaviour of mechanical wall-to-wall horizontal connections are also presented. This experimental programme has been carried out within the framework of a joint research between Politecnico di Milano and DLC Consulting-Milan aimed at the exploitation of a registered invention patent and has been partially funded by the programme “Brevetti+” (g.u. 179 of 02/08/2011)
Structural modelling and probabilistic seismic assessment of existing long-span precast industrial buildings
No full textPrecast concrete frame structures constitute a major construction technology of the industrial built heritage within the Italian territory. Most of these buildings were conceived according to obsolete seismic design criteria with lower hazard than currently recognised standards, whilst the most industrialised areas spread over the Italian territory were declared seismically active since less than 20 years. This paper focuses on seismic performance assessment of long-span flat-roof industrial buildings, representative of modern design technologies. Buildings located in areas with increasing seismic hazard over the Italian territory were designed following an archetype existing building based on standards in force after 1996. Seismic performance is investigated by modal response analysis, non-linear static pushover analysis, and non-linear time-history analysis with a multi-stripe approach. The flexibility of the horizontal diaphragm and the interaction of the resisting frame with the cladding system are addressed by exploring progressively advanced modelling strategies up to a detailed assembly comprising roof members, peripheral panels, and all related connections. Mechanical non-linearities regarding column elements, dowel beam-to-column and slab-to-beam connections, strap tie-back and bracket bearing panel-to-frame connections are modelled with lumped plasticity employing experimentally calibrated constitutive laws. Seismic risk is assessed by estimating via multi-stripe analysis failure rates encompassing performance levels from usability preventing damage to global collapse. The results are site-dependent, and the need for retrofit of these typical precast systems is deemed to be urgent for both buildings designed in areas of average and high seismicity
Structural vulnerability of old precast building stock: case studies from the period 1940s-1970s
No full textThis work aims at evaluating the structural performance indexes of different typologies of reinforced concrete precast industrial buildings built in the 40-70s of last century. Precast industrial buildings belonging to the pioneer era of this technology are quite common all over Italy and were mostly devoted to house industrial activities. As a matter of fact, they were designed according to criteria which are now obsolete, mainly for lower static actions as compared to current codes and without any concept for seismic or fire resistance. As such, they potentially feature strong vulnerability. With reference to two industrial complexes located in Brianza (Northern Italy), both built with successive expansions from the ‘40s to the ‘70s, the structural performances of 10 different typologies representative of the Italian precast building stock of this period are evaluated under static, seismic and fire actions. These typologies include vault roofs with truss systems, restrained arches, tapered beams, and moment-resisting portal frames. A preliminary assessment of the vulnerability associated to these types of structures is performed based on their geometry and reinforcement details. Tentative ranges of cost associated to their retrofit are calculated based on the experience of past interventions gained by the technical partner of the paper
LINEAR DYNAMICS OF PRECAST VERTICAL PANELS CLADDING INDUSTRIAL FRAMES UNDER EARTHQUAKE ACTION
No full textThe dynamic interaction of heavy vertical cladding panels with single-storey precast industrial frame structures plays a relevant role upon the generation of seismic actions in the connection devices out of the plane of the panels. Nevertheless, the current design approaches consider the panels as “non-structural members” and the forces at the connections are evaluated with approximate expressions available in the literature and mainly conceived for suspended masses. This paper, starting from a rigorous definition of the problem, highlights a minimal set of parameters that control the linear dynamics of the system and presents a novel analytical solution for the evaluation of the system response under seismic excitation. This task is indeed complex due to the peculiar kinematics of the panel and to the different accelerations imparted to the panels, at the same time, in foundation and in correspondence of the connection to the frame. Applications of the code expeditive evaluation of the maximum forces at the top and bottom connections of the panel highlight large discrepancy with respect the newly proposed rigorous solution, albeit being on the safe side
Numerical assessment of seismic retrofit interventions on a long-span precast industrial building
No full text
Numerical assessment of seismic retrofit interventions on a long-span precast industrial building
No full textMost of the industrial buildings of the Italian territory is characterised by precast concrete frame structures. Furthermore, subsequent reviews of the Italian seismic design code updated the classification of most industrialized areas in Italy as seismically active. Therefore, a consistent part of the industrial built heritage may be deemed to be seismically inefficient according to current standards, potentially highlighting issues concerning flexural performance of columns and support connections of both horizontal members and cladding panels. This paper investigates a seismically retrofitted benchmark structure representative of monostorey industrial buildings characterised by large height and structural grids. Rational retrofit solutions of increasing impact and efficiency are presented and implemented into a structural model explicitly including not only structural members, but also cladding panels and connections characterised by non-linear constitutive laws. The beneficial impact of the adopted seismic retrofit strategies is analysed through modal and non-linear static analysis
Local modelling of cast-in threaded dowel bar connections of precast joints under lateral loading
No full textLinear dynamics of precast vertical panels cladding industrial frames under earthquake action
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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