1,721,151 research outputs found
Fragility Curves and Loss functions for RC structural components with smooth rebars
No full textFragility and loss functions are developed to predict damage and economic losses due to earthquake loading in Reinforced Concrete (RC) structural components with smooth rebars. The attention is
focused on external/internal beam-column joints and ductile/brittle weak columns, designed for gravity loads only, using low-strength concrete and plain steel reinforcing bars. First, a number of damage states are proposed and linked deterministically with commonly employed methods of repair and related activities.
Results from previous experimental studies are used to develop empirical relationships between damage states and engineering demand parameters, such as interstory and column drift ratios. Probability distributions are fit to the empirical data and the associated statistical parameters are evaluated using statistical methods. Repair costs for damaged RC components are then estimated based on detailed quantity survey of a number of pre-70 RC buildings, using Italian costing manuals. Finally, loss functions are derived to predict the level of monetary losses to individual RC components as a function of the experienced response demand
Re-centring Capability of Flag-Shaped Seismic Isolation Systems
No full textThe re-centring capability is identified by the current design codes as a fundamental feature of seismic isolation systems. In this paper, the re-centring capability of seismic isolation systems characterised by a flag-shaped hysteretic cyclic behaviour is investigated through an extensive parametric study of single-degree-of-freedom hysteretic systems subjected to different natural records. A remarkable example of this kind of isolation system derives from the combination of flat steel-PTFE sliding bearings with auxiliary re-centring devices based on the superelastic properties of Shape Memory Alloys. The results of the parametric analyses are processed statistically and regression analysis relations are derived that show the dependence of the residual displacement after the earthquake on the governing parameters of the isolation system. Based on the analysis results, the features of the flag-shaped system that guarantee sufficient re-centring capability are identified
Nonlinear Static Methods vs. Experimental Shaking Table Test Results
No full textThree different Nonlinear Static Methods (NSM’s), based on pushover analysis, are applied to a 3-story, 2-bay, RC frame. They are (i) the Capacity Spectrum Method (CSM), described in ATC-40, (ii) the Displacement Coefficient Method (DCM), presented in FEMA-273 and further developed in FEMA 356, and (iii) the N2 Method, implemented in the Eurocode 8. Pushover analyses are conducted with DRAIN-3DX by using four different lateral force distributions, according to the acceleration profile assumed along the height of the structure: uniform, triangular, modal-proportional, and multimodal fully adaptive. In the numerical model, RC members are modeled as fiber elements. The numerical predictions of each method are compared to the experimental results of the shaking table tests carried out on two similar 1:3.3-scale structural models, with and without infilled masonry panels, respectively. The comparison is made in terms of maximum story displacements,
interstory drifts, and shear forces. All the NSM’s are found to predict with adequate accuracy the maximum seismic response of the structure, provided that the associated parameters are properly estimated. The lateral load pattern, instead, is found to little affect the accuracy of the results for the three-story model considered, even if collapse occurs with a soft story mechanism
Displacement limits and performance displacement profiles in support of direct displacement-based seismic assessment of bridges
No full textDisplacement limits and performance displacement profiles (PDPs) for the direct displacement-based assessment of existing bridges are proposed. The PDPs are defined as the bridge inelastic deformed shapes associated with the attainment of selected damage states in some critical elements of the bridge. In the paper, displacement limits are provided for piers, abutments, joints, bearing devices and shear keys. Moreover, different approaches for the definition of the PDP are examined, including adaptive pushover analysis, effective modal analysis, and rational analysis of simplified bridge models. In the paper, the key aspects and modeling assumptions of the proposed direct displacement-based assessment procedure are presented first. This is followed by some examples of application to typical Italian highway bridge configurations, differing in pier layout, deck type, and pier-deck connections
Seismic Rehabilitation of Existing Reinforced Concrete Buildings with Seismic Isolation: A Case Study
No full textThe use of seismic isolation for the seismic rehabilitation of existing buildings is very attractive but often very tricky due to several aspects related to its implementation. In this paper, a case study of seismic rehabilitation of a high-rise residential building with seismic isolation is presented. The building under consideration is located in southern Italy and it is placed next to another building from which it is separated by a gap of 400 mm. In the paper, all the steps of the seismic rehabilitation process are described. First, the target objective of the seismic rehabilitation and the choice of isolation system type and location are discussed. The design of the isolation system, carried out following a direct displacement-based approach, is then examined. Finally, the main phases followed in the installation of the isolation system are described. Some comments on costs and time needed to complete the intervention are also reported
Valutazione delle caratteristiche degli elementi strutturali degli edifici esistenti e della sicurezza sismica mediante metodi approssimati
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