1,720,978 research outputs found
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
Design, testing and implementation of a Cu-SMA-based device for improving the thermal behavior of steel tie-rods
No full textSteel cables, tendons and tie-rods are the key components of many structures including masonry arches and vaults, timber roof trusses and several post-tensioned structures. In this paper, a device prototype based on the superelastic properties of Cu-based Shape Memory Alloys (SMAs), is proposed to enhance the thermal behavior of such structural elements. The thermal behavior of steel tie-rods with and without SMA is evaluated through comprehensive experimental tests in thermal room. During the tests, different temperature-time histories are considered, with air temperature varied between -10°C and 40°C. The results of the experimental tests confirm the great effectiveness of the proposed SMA device, with reductions of force changes due to air temperature variations of the order of 80-90%, compared to steel tie-rods without SMAs. In the paper, the main structural components and basic functioning principles of a SMA-based device prototype for masonry arches and vaults are presented and aspects related to its implementation in practice are discussed in detail
Experimental evaluation of the mechanical behavior of elastomeric materials for seismic applications at different air temperatures
No full textThis paper presents the results of an experimental study aimed at investigating the sensitivity of the cyclic behavior of elastomeric materials to air temperature variations. The experimental tests have been performed on several elastomeric specimens, purchased from two different Italian manufacturers of structural bearings and seismic isolation devices. Six different types of elastomers, with shear modulus (G) ranging from 0.5 MPa to 1.2 MPa at 100% shear strain, have been examined. During the tests, the specimens have been cycled under shear strains of increasing amplitude (from 25% to 125%), at three different frequencies of loading (0.01Hz, 0.1Hz and 0.5Hz). The tests have been carried out at six different air temperatures, ranging between -20 °C and 40 °C. The effects of prolonged exposure to low temperatures have been also investigated. The cyclic behavior of the specimens is described in terms of (i) shear stress at zero cyclic strain, (ii) maximum shear stress,(iii) secant shear modulus at the maximum strain amplitude, (iv) energy loss in one fully reversed cycle and (v) corresponding equivalent viscous damping ratio. In the paper, the most important results of the experimental investigation are described
Sviluppo di Approcci agli Spostamenti per il Progetto di Strutture dotate di sistemi di controllo passivo
No full textLateral Force Distributions for the Linear Static Analysis of Base-Isolated Buildings
No full textThis paper presents a new approach for the evaluation of accurate lateral force distributions for the Linear Static Analysis (LSA) of Base Isolated (BI-) buildings. In essence, the proposed lateral force distributions depend on a factor measuring the degree of nonlinearity of the Isolation System (IS) and on the ratio between the effective period of the BI-structure (Tis) and the fundamental period of the Fixed Based (FB-) structure (Tfb). The proposed approach is fully compatible with the Direct Displacement-Based Design (DDBD) method, recently developed by Priestley and co-workers. The proposed lateral force distributions have been derived from the results of a large number of Nonlinear Time-History Analyses (NTHA), carried out on six numerical models of multi-storey buildings, differing in storey number (3, 5 and 8, respectively) and fundamental period of vibration (from 0.25 to
0.8 s) in the fixed-base configuration. A great variety of Isolation Systems (ISs), characterised by either Elasto-Plastic with Hardening (EPH) or Flag-Shaped (FS) force-displacement behaviour, have been considered in the NTHA. The numerical parameters of the IS models have been varied in such a way as to reproduce the actual mechanical behaviour of the main currently used ISs, including: (i) Lead Rubber Bearings (LRB), (ii) High-Damping Rubber Bearings (HDRB), (iii) Friction Pendulum Bearings (FPB), (iv) combinations of flat Sliding Bearings (SB) and Low-Damping Rubber Bearings (LDRB) and (v) Combinations of flat SB
and re-centring devices based on Shape Memory Alloys (SMA). Comparisons between the storey shear forces derived with the proposed method and those obtained from NTHA clearly show the great improvements in the accuracy of LSA predictions, when using the proposed lateral force distributions
Ideazione, progettazione, caratterizzazione e verifica sperimentale di dispositivi a base di leghe a memoria di forma per catene orizzontali per strutture spingenti e ritegni antisismici per impalcati da ponte
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