Search results for "seismic"
showing 10 items of 338 documents
Dynamic shakedown of structures under repeated seismic loads
1995
Elastic, perfectly plastic structures are considered under the action of repeated short-duration exitations of seismic type acting in an unknown time sequence, but belonging to a given polyhedral excitation domain. The basic excitations (vertices of the polyhedron) are chosen as discrete-spectrum waves each with frequencies coincident with the first natural frequencies of the structure, and amplitudes related to the ground features and earthquake intensity (according to the Kanai and Tajimi filter model) in such a way that every admissible excitation-obtained as a linear convex combination of the basic ones-has a maximum power not exceeding a given value. In the framework of unrestricted dy…
Cyclic behavior of composite truss beam-to-RC column joints in MRFS
2016
In the present paper, the cyclic behavior of beam-to-column joints made up of Hybrid Steel Trussed Concrete Beams (HSTCBs) connected to Reinforced Concrete (RC) piers is investigated. HSTCBs are a typology of composite beam generally constituted by a steel truss with end zone added rebars embedded within a block of concrete cast in place. HSTCBs represent a structural solution for light industrialization in the civil constructions; the main advantages in their use are the higher construction speed with the minimum site labor, the possibility of covering wide spans with low depths and a final economical convenience. For these reasons, they are also increasingly adopted within seismic framed …
Stochastic seismic analysis of MDOF structures with nonlinear viscous dampers
2009
Fluid damper devices in civil structures such as buildings or bridges are commonly used as energy absorbers for seismic protection. The problem in the response analysis of structures with filled dampers mainly consists in the fact that, due to the strongly nonlinear behavior of such equipments, the response spectrum (RS) technique fails. In this paper by using the concept of power spectral density function compatible with the elastic RS and the statistical linearization technique, the equivalent damping ratio is obtained. It is shown that once the system is linearized, results obtained by Monte Carlo simulation and those obtained by stochastic analysis are in good agreement. Copyright © 200…
Fundamental period of infilled reinforced concrete frame structures
2016
AbstractThe fundamental period of vibration appears to be one of the most critical parameters for the seismic design and assessment of structures. In the present paper, the results of a large-scale analytical investigation on the parameters that affect the fundamental period of reinforced concrete structures are presented. The influence of the number of storeys, the number of spans, the span length, the infill wall panel stiffness and the percentage of openings within the infill panel on the fundamental period of infilled RC frames was investigated. Based on these results, a regression analysis is applied in order to propose a new empirical equation for the estimation of the fundamental per…
Passive-damping design for vibration control of large structures
2013
In this work, a systematic strategy to design passive damping systems for structural vibration control is presented. The proposed design methodology is based on the equivalence between decentralized static velocity-feedback controllers and passive damping systems. By using recent developments in static output-feedback control, the design of passivedamping systems can be formulated as a single optimization problem with Linear Matrix Inequality constraints. Moreover, this optimization problem can be efficiently solved with standard numerical tools, even for large dimension systems. Due to its computational effectiveness, the proposed methodology can be applied to the design of passive damping…
Incremental dynamic based fragility assessment of reinforced concrete structures: Stationary vs. non-stationary artificial ground motions
2017
Abstract Artificial and natural records are commonly employed by researches and practitioners to perform refined seismic assessments of structures. The techniques for the generation of artificial records and their effectiveness in producing signals which are significantly representative of real earthquakes are still debated as well as results of the consequent seismic assessment to expect from their application. The paper presents an in-depth comparative study highlighting the effect of employing different typologies of artificial ground motion records on seismic assessment results, especially addressing seismic fragility curves. Three sets of 50 stationary, nonstationary evenly modulated a…
Upwards - Vertical extensions of masonry built heritage for sustainable and antifragile urban densification
2021
Abstract Urban densification represents one of the biggest universal challenges of contemporary cities: the increase of urban population requires new spaces to accommodate the growing demand for housing, working and tertiary activities. However, the land available for new constructions in highly urbanized areas is very limited. In this framework, the vertical extension of existing buildings is the most sustainable strategy and fascinating. Masonry structures , constituting a major part of the built stock in the historical city centres of several European countries, are particularly suitable for vertical addition of extra-floors, since they generally exhibit an adequate overstrength for bear…
Steel based retrofitting interventions for existing masonry walls: a comparative numerical investigation
2021
Masonry buildings constitute a significant portion of the architectural heritage all over the world, also in regions affected by a high seismic hazard. Since this constructional material is character-ized by lack of tensile strength, as well as small deformation capacity, masonry structures could result hugely damaged if shaken by seismic forces. In order to avoid collapses and reduce struc-tural damage, innovative retrofitting interventions are necessary to improve the seismic behavior of masonry structures. In this context, steel-based techniques could be considered among the most suitable solutions. In fact, by using such a high-performant material, additional strength and ductility may …
Influence Of Lateral Load Distributions On Pushover Analysis Effectiveness
2008
The effectiveness of two simple load distributions for pushover analysis recently proposed by the authors is investigated through a comparative study, involving static and dynamic analyses of seismic response of eccentrically braced frames. It is shown that in the upper floors only multimodal pushover procedures provide results close to the dynamic profile, while the proposed load patterns are always conservative in the lower floors. They over-estimate the seismic response less than the uniform distribution, representing a reliable alternative to the uniform or more sophisticated adaptive procedures proposed by seismic codes. © 2008 American Institute of Physics.
The Bell-Tower Facade: An Aseismic Device in Sicily Between the 12th and 18th Centuries
2014
Imposing tower facades with belfries in the last order were built in Sicily Italy, from the Middle Ages to the late Baroque period. Until the 16th century, this model, which was inspired by northern European examples, also had a parallelepiped forepart leaning against the facade, working as containment for the pressure imparted by the inner longitudinal arches on the front, and amplified in case of earthquakes. The lacking static efficiency of these early structures is demonstrated by collapses during the strong earthquakes that hit the island in the modern age. Despite numerous cases of destruction, the memory of some prototypes survived in Sicilian constructive memory through the elaborat…