1,721,465 research outputs found
Case study: Seismic upgrade of a masonry bell tower by GFRP ties
No full textIn many cases masonry buildings present structural problems related to development of local mechanisms under seismic
actions. The solution to this weakness has to be chosen taking into account several aspects if the construction is ancient and is gifted of
monumental significance. In this paper the case of the Bell Tower of Santa Maria del Carmine Napoli, Italy is discussed; the construction
has been deeply examined by the writers performing experimental inquires in situ and theoretical analysis with three-dimensional models.
While the results obtained in the hypothesis of compact behavior of the structure have pointed out a low risk condition under seismic
actions, in contrast the study of local out-of-plane mechanisms, dealt with in detail in this paper, have evidenced an unsafe situation. To
avoid such mechanisms, connective systems with tie rods made of glass fiber-reinforced polymer laminates have been designed to be
inserted where local verifications are not satisfied. Design, application, and monitoring procedures of this innovative intervention are
discussed in detail herein
Deformability of base connections in shotcreted concrete sandwich load bearing perforated walls
No full textFast construction of structural walls made of reinforced concrete for buildings or industrial warehouses in single panel is a cost-effective system in terms of both the quality of construction and the economy. Anti-seismic constructions can be built with additional reduction of heat dispersion and noise attenuation. In this study the structural system is composed of a factory produced corrugated panel of polystyrene covered on both sides by an electro-welded zinc coated mesh of galvanized steel and shotcreted concrete poured to build the vertical structural walls. This system allows economic savings compared to the traditional systems; however, deformability of the base connections can alter significantly the structural behaviour and seismic response. This study deals with both experimental tests on a real scale structure and numerical simulations, with the goal to provide an efficient formulation to model the deformability of base connections in such sandwich concrete structures, while the materials are modelled either linear elastic or nonlinear
Stick-IT: A simplified model for rapid estimation of IDR and PFA for existing low-rise symmetric infilled RC building typologies
No full textThe prediction of seismic performances of buildings in terms of engineering demand parameters EDP, such as interstorey drift ratios IDR and peak floor accelerations PFA, represents a fundamental step towards the assessment of potential direct economic losses. This paper proposes a simplified model for the rapid assessment of EDPs in infilled moment resisting frames subjected to seismic loadings suitable for large scale assessment studies. The proposed model, named Stick-I (Stick model for Infilled frames), is a multi-degree of freedom MDOF system consisting of a series of lumped masses connected by means of nonlinear shear link elements. The shear link behavior is suitably calibrated adopting a multi-objective Genetic Algorithm procedure that employs the results of nonlinear cyclic pushover analyses performed on refined nonlinear FEM. Based on the regression study performed on a suitably generated Stick-I model database, a more general Stick-IT model, representative of RC Infilled frame Typologies of assigned storey number and dimensions in plan, is introduced. Simplified formulas for the definition of Stick-IT model are proposed depending on low-level information data that can be easily retrieved from rapid on-site surveys or remote sensing techniques. Both Stick-I and Stick-IT models are validated comparing the results of NRHA performed on refined FEMs with the results obtained adopting the simplified models and good agreement in terms of maximum EDP values and distribution along the building height is obtained. The typological Stick-IT model, which is defined as a function of few geometric and mechanical parameters, can be easily applied for simplified evaluation of expected response for building typologies. Hence, it can also be usefully employed for assessment of direct losses at the large scale, with a significant reduction in computational burden with respect to more refined methods
Considering structural modelling uncertainties using Bayesian cloud analysis
No full textQuantifying the impact of modelling uncertainty on the seismic performance assessment is a crucial issue for existing buildings, considering the partial information available related to material properties, construction details and the uncertainty in the capacity models. The effect of structural modelling uncertainties on the seismic performance of existing buildings can be -under certain circumstances- comparable to that of uncertainty in ground motion representation. In this work, a modified version of Cloud analysis considering the (eventual) cases of global dynamic instability and adopting the critical demand to capacity ratio as the damage measure/decision variable, based on coupling the simple regression in the logarithmic space of structural response versus seismic intensity for a suite of registered records with logistic regression, has been implemented to consider the record-to-record variability, structural modelling uncertainties and the uncertainties in the parameters of the adopted fragility model. For each of the registered records within the suite of ground motion records, a different realization of the structural model has been generated through a standard Monte Carlo Simulation procedure. A Bayesian version of the Cloud method is employed, in which the uncertainty in the structural fragility model parameters is considered. This leads to a robust fragility estimate-reflecting both record-to-record variability and structural modeling uncertainties-- and a desired confidence interval defined around it -reflecting the uncertainty in the fragility model parameters. The longitudinal frame of an existing building in Van Nuys, CA, modeled in OpenSees considering the flexural-shear-axial interaction, has been employed in order to demonstrate this procedure. The critical demand to capacity ratio adopted as the damage measure/decision variable, corresponding to the component or mechanism that leads the structure closest to the onset of limit state (e.g., near collapse), is adopted as the structural response parameter. This structural response parameter can encompass both ductile and fragile failure mechanisms. Moreover, it can register a possible shift in the governing failure mechanism with increasing intensity. The selection of the suite of ground motion records has been based on a set of criteria that ensure the statistical significance of the linear regression in predicting the structural response as a function of the intensity measure
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