1,721,011 research outputs found
Masonry infilled r.c. frames Implementation and experimental verification of models for nonlinear analysis
No full textProposal and application of the Incremental Modal Pushover Analysis (IMPA)
No full textIn recent years, many research activities were undertaken to develop a reliable and practical analysis procedure to identify the safety level of existing structures: Incremental Dynamic Analysis (IDA) is considered to be one of the most accurate methods to estimate the seismic demand and capacity of structures. However, the executions of many complex and computationally heavy nonlinear response history analyses (NL-RHA) are required. This paper deals with the proposal of an efficient Incremental Modal Pushover Analysis (IMPA) to obtain capacity curves by replacing the nonlinear response history analysis of the IDA procedure with Modal Pushover Analysis (MPA). In this work, the MPA is extended and applied to three-dimensional asymmetric structures and finally it is used in order to obtain a "multimodal" capacity curve: therefore MPA method is used to evaluate both displacements, as in the standard method, and base shear (this is a novelty). According to this approach the proposed procedure (IMPA) is defined and applied to estimate the structure's seismic response and capacity for given seismic actions. This new procedure is finalized to obtain a capacity curve, as commonly done performing pushover, but it accounts also higher modes effects. Finally IMPA is applied to an existing irregular framed building and compared with NL-RHA
A design procedure of dissipative braces for seismic upgrading structures. 2ECEES Second European conference on earthquake engineering and seismology
No full textThe research presented in this paper deals with the seismic retrofitting of existing frame structures by
means of passive energy dissipation. An iterative displacement-based procedure, based on capacity
spectrum is described and some applications are discussed. The procedure can be used with any
typology of dissipative device and for different performance targets. In this work the procedure has
been applied to an existing r.c. frame building, which shows both vertical and plan irregularities. In the
application presented the buckling restrained braces have been used in order to prevent damages to
both the structure and non structural elements. The evaluation of commonly Nonlinear Static
Procedures (NSPs) for seismic response of the existing and retrofitted structure is presented to check
the suitability of the use of NSP in the design procedure: the use of conversional NSPs to be not
suitable for the case of irregular building but, once this building is retrofitted, and therefore
regularized, with a bracing system, the use of NSPs for seismic response of the braced structure is
effective
A design procedure of dissipative braces for seismic upgrading structures
No full text"Existing reinforced concrete frame buildings with non-ductile detailing could suffer severe damage and caused loss of life during earthquakes. In recent years many research activities have been paid to develop innovative and more reliable structural control devices and different rehabilitation systems have been studied to upgrade the seismic performance of this kind of structures. The research discussed in this paper deals with the seismic protection of frame structures by means of passive energy dissipation. A displacement-based procedure to design dissipative bracing for the seismic protection of frame structures is proposed and some applications are discussed. The procedure, based on the displacement based design and using the capacity spectrum method, aims to be used as a professional tool as it does not require sophisticated dynamic nonlinear analyses but only common non linear static analyses. Two performance objective have been considered developing the procedure: to protect the structure against structural damage or collapse and avoid non-structural damage, this is done limiting global displacements and interstorey drifts. In the paper the argument is discussed and compared to other different existing approaches. After the presentation the procedure is applied to case studies. The applications are: two 2D r.c. frames, one infilled and one bare, and finally a real application on an existing 3D.
Experimental tests and global modeling of masonry infilled frames
No full textThe effects of infill panels on the response of r.c. frames subjected to seismic action are widely recognized. Numerous experimental investigations were effected and several analytical models were developed on this subject. This work, which is part of a larger project dealing with specific materials and structures commonly used in Italy, discusses experimental tests on masonry and samples of bare and infilled portals. The experimental activity includes tests on elemental materials, and 12 wall samples. Finally, three one-bay one-story reinforced concrete frames, designed according to the outdated Italian technical code D.M. 1996 without seismic details, were tested (bare and infilled) under constant vertical and cyclic lateral load. The first cracks observed on the framed walls occurred at a drift of about 0.3%, reaching its maximum capacity at a drift of 0.5% while retaining its capacity up to a drift of 0.6%. Infill contributed to both the stiffness and strength of the bare reinforced concrete frame at small drifts thus improving overall system behavior. In addition to the experimental activities, previously mentioned, the recalibration of a model proposed by Comberscue (1996) was evaluated. The accuracy of an OpenSees non linear fiber based model of the prototype tested, including a strut element was verified through a comparison with the final experimental results. This work has been partially supported by research grant DPC-ReLUIS 2014
Proposal of a modal pushover based incremental analysis
No full textExisting reinforced concrete frame buildings designed for vertical load only could suffer severe damage during earthquakes. In recent years, many research activities have been paid to develop reliable and practical analysis procedure to identify the safety level of existing structures. The research discussed in this paper deals with proposal of an efficient incremental procedure to estimate seismic capacity of irregular structures performing few pushover analysis (one for every relevant modal shape) and applying a series of Modal Pushover Analysis (MPA). This approach, similar to the Incremental Dynamic Analysis (IDA), replaces the Nonlinear Response History Analyses (NL_RHA) by simple pushover analyses. In this work, this idea, named IMPA (Incremental Modal Pushover Analysis), is proposed for a 3D complex building and this application is described and discussed
Compression tests on masonry walls realized with a single or double masonry panel
No full textIn this paper, the results of the experimental tests, carried out at the Laboratory on Materials and Structures of the University of Roma Tre to characterize masonry panels behavior are shown and discussed. 36 single and 12 double panels have been considered: 12 single panels are made of 80x160x330 mm3 bricks with horizontal holes, 24 of 120x250x120 mm3 half-full bricks with vertical holes and two different mortars and 12 double panels coupling the two previous types of simple panels. The panels have been built with a level of accuracy similar to the one adopted in buildings therefore they are well done but not lacking some defects that unavoidably would be found in real constructive practice. Compression tests in horizontal, vertical and diagonal directions were performed to evaluate their “constitutive relationships” in term of force-displacement diagrams and in particular their strength and elastic modulus.
Experimental tests also included the characterization of the bricks and of the mortar used to realize the panels
Seismic upgrading of structures: a design procedure for dissipative buckling restrained braces
No full textExisting reinforced concrete frame buildings with non-ductile detailing suffered severe damage and caused loss
of life during earthquakes. Different rehabilitation systems have been developed to upgrade the seismic
performance of this kind of structures.
The research discussed in this paper deals with the seismic upgrading of frame structures, in particular for the
application presented buckling restrained steel braces (BRB) have been selected.
A displacement-based procedure to design dissipative bracing for the seismic protection of frame structures,
together with an optimization criteria for the bracing, is proposed and some applications are discussed.
The procedure does not require sophisticated dynamic nonlinear analyses but only common non linear static
analyses: it is based on the displacement based design and using the capacity spectrum method.
Two performance objective have been considered developing the procedure: to protect the structure against
structural damage or collapse and avoid non-structural damage.This latter is done limiting global displacements
and interstorey drifts.
Finally the procedure has been applied to some case studies and existing r.c. frames both 2D and 3D
Discussione, applicazione e validazione di una procedura progettuale per la protezione sismica di telai tamponati mediante controventi dissipativi.
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