1,721,000 research outputs found
The Economic and Social Value of Fostering Entrepreneurs in a regional system: the role of education
No full textRethinking entrepreneurship education within universities: knowledge sharing as value proposition
No full textA Resilience and Robustness Oriented Design of Base-Isolated Structures: The New Camerino University Research Center
Full text linkThis paper analyses the new Research Centre designed for the University of Camerino and entirely financed by the national Civil Protection Department (DPC), following the seismic events in Central Italy in 2016. The building has been designed to guarantee speed of execution as well as a high level of safety, especially regarding seismic actions. The structural solution was to create an isolated system with a steel braced super-structure with pinned joints and r.c. sub-structures able to adapt to the complex morphology of the area. As described in the first part of the paper, design choices have been made to achieve a high level of resilience and robustness, i.e., to limit damage to structural and non-structural components and equipment under moderate and design seismic actions and to avoid disproportionate consequences in the event of extreme actions, larger than the design ones. In the second part of the paper, specific risk analyses have been carried out to evaluate the real performance of the building under increasing intensity levels, with reference to both serviceability and ultimate conditions. To this purpose a site-specific hazard study was first conducted, then non-linear analyses were performed using a hazard-consistent set of records with return periods ranging from TR = 60 years to TR = 10000 years. The main demand parameters of both the isolation system and the super-structure were recorded and capacity values corresponding to different ultimate and damage limit conditions were defined. The results obtained in terms of demand hazard curves show that the building performances in terms of robustness and resilience are very high, confirming the efficacy of the strategies adopted in the design
Effects and Outcomes of Entrepreneurship Education in Italy. Evidence from the Case of clab by Università Politecnica delle Marche
No full textThe creation of new firms and businesses is seen as a key factor in reaching economic goals at the regional and national levels. Universities can support entrepreneurial dynamics by increasing the motivation and competence of their graduates to become individuals involved in innovative and entrepreneurial activity. Many initiatives and educational programs on entrepreneurship are increasingly becoming more action-oriented, emphasizing the aspect of learning by doing. The aim of this paper is to assess the effects and the outcomes of an Italian educational program about entrepreneurship named Contamination Lab (clab), which has been implemented so far in several Italian universities. We specifically consider the clab experience at one medium-sized University, Università Politecnica delle Marche (upm), which was launched in 2014. Considering the newness of the investigated phenomena, this is a qualitative study that takes an exploratory approach. The reference population for the study comprises 450 students who took part in the clab at upm between 2014 and 2020. Data were collected through an e-mail survey carried out in 2020. The results show that the participation in the program improved the entrepreneurial intention of students, and some of them were supported in starting a new business. Although the number of entrepreneurial programs at the university level has grown considerably over the past two decades, the effects and contributions of such entrepreneurial educational initiatives in Italy are still not completely clear. This paper represents a first attempt to evaluate the first effect (perceived by students) and the first outcomes of a clab program (in terms of number of start-ups and gestation activities carried out by students)
Seismic behaviour of a RC frame isolated by HDNR bearings under increasing intensity levels
No full textHigh Damping Natural Rubber (HDNR) bearings are characterized by stiffness and damping capacity that significantly depend on the shear deformation amplitude. More in details, at low deformations stiffness and damping increase, whereas at large deformations the stiffness remarkably increase but the damping capacity decreases. Additionally, this kind of bearings show a loading hysteresis dependence, due to the internal damage of the rubber occurring as the deformation history progresses. This effect, also known as stress-softening, becomes significant for large deformation amplitudes and represents a source of uncertainty, which has recently caused a limitation of the use of this kind of isolators. However, consequences of this nonlinear behaviour of HDNR bearings on the response of isolated structures are not comprehensively investigated, primarily because advanced models have been only recently developed. In this paper some investigations are carried out by using a nonlinear constitutive law recently developed by some of the authors describing the behaviour of a HDNR with significant stress-softening complying with the limits of European code on anti-seismic devices. Analyses are carried out on a multi-degree of freedom system by considering different seismic intensity levels and different response parameters, including floor response spectra. A linear visco-elastic model calibrated at each seismic intensity level is also adopted in the analyses. The obtained results show that some response amplifications happen due to the higher modes of the superstructure, which are underestimated by linear models and may cause damages to non-structural components and equipment
Variability of Dynamic Properties of Rubber Compounds for Elastomeric Bearings
No full textThe λ-factors for stiffness and damping of rubber bearings should be experimentally assessed during the qualification process or deduced from tests performed on material specimens. Moreover, the -factors suggested in the informative annexes of EN 15129 and of EC8-part 2 can be also used as reference values. However, they are derived from outdated experimental campaigns and do not refer to all the sources of variability. In this paper, a statistical analysis on a significant set of rubber compounds, certified according to EN 15129 from different suppliers, is carried out to assess the current variability of the dynamic properties of such compounds. Different sources of variability may be identified by distinguishing between behavioural and environmental effects. For elastomeric bearings, especially high-damping rubber (HDR) ones, the main behavioural effects are strain amplitude, strain rate dependence, and cyclic degradation, whereas the environmental effects are due to temperature variation and ageing. All these sources of variability have been analysed in this paper. The results of the statistical analysis have been used to propose a new set of -factors for all the source of variability studied. Such new values have been compared with the ones suggested by the codes when available. The main inconsistencies found have been highlighted and commented in this paper. Finally, some considerations about the influence of such variability on the structural response of base-isolated structures have been drawn by focusing on both the isolation system and the superstructure
INFLUENCE OF DESIGN PARAMETERS ON THE SEISMIC RELIABILITY OF BASE ISOLATED SYSTEMS
No full textSeismic isolation is considered an effective solution to protect buildings and reduce seismic losses. However, the reliability level achieved by code-conforming base-isolated structures can be not uniform due to the different behavior of the most used isolation bearings (elastomeric or sliding bearings) as well as the different design choices that strongly influence the seismic reliability of base-isolate structures. In this paper High Damping Rubber Bearings (HDRBs) are considered and a parametric analysis is performed to assess the overall reliability of base-isolated buildings designed according to Eurocodes and Italian seismic codes. In particular, the case of ordinary residential buildings is considered, and the following parameters have been considered and varied, within the range of most common values: the bearings design shear deformation and the superstructure design over-strength ratio. Probabilistic analyses are performed using a robust direct simulation approach (Subset Simulation) and a bidirectional stochastic ground motion model. For each case analyzed, results are provided in terms of demand hazard curves of the most relevant response parameters characterizing the isolation system and the superstructure
Seismic reliability of base isolated systems: sensitivity to design choices
Full text linkSeismic isolation is considered an effective solution to protect buildings and related content from earthquakes, and consequently reduce seismic losses. However, the overall reliability levels achieved on these systems by following the design rules suggested by codes are not uniform and they may be strongly influenced by some choices made in the structural design. This study aims to investigate the seismic reliability of structural systems equipped with high-damping rubber bearings, which is a widely used class of isolators. An extensive parametric analysis is performed to assess the influence of design choices on the failure probability, considering design parameters concerning both the isolation system and the superstructure, such as: isolation period; bearings shear strain; percentage of flat sliders (i.e., bearing shape factors); superstructure overstrength ratio. A set of case studies have been configurated by varying and combining all the aforesaid parameters. A stochastic model is used for the bidirectional seismic input and the generation of horizontal ground motion components, whereas full probabilistic analyses are performed via Subset Simulation to achieve accurate estimates of the demand hazard curves up to very small failure probabilities. To reduce the computational effort, a 3D-model with a reduced number of DOFs (Degrees of Freedoms) is adopted for each case study. It consists of an uncoupled bidirectional elastoplastic model of the superstructure, and an advanced nonlinear 3D model of the rubber isolators, accounting for the coupling between vertical and horizontal response in large displacements. For each case analysed, demand hazard curves are evaluated to illustrate the probabilistic properties of the seismic response for both isolation system and superstructure. Results show a noticeable sensitivity of the system reliability with respect to the examined design choices and in some cases the achieved structural performance can be far from the safety levels required by the Codes
Behaviour of Structures Isolated by HDNR Bearings at Design and Service Conditions
Full text linkHigh-Damping Natural Rubber (HDNR) bearings are widely employed for seismic isolation. These bearings are characterized by a remarkable nonlinear behaviour and often by a degrading cyclic response, induced by the addition of filler to enhance its dissipation capacity. This latter phenomenon, denoted as stress-softening or Mullins effect, can significantly influence the nonlinear dynamic response of isolated structures leading to a variability of the seismic response of isolated buildings. Moreover, the behaviour of HDNR bearings may produce an amplification of response, due to higher modes contribution, which can affect the performance of non-structural components and equipment. Models providing an accurate description of the nonlinear behaviour of HDNR bearings with significant stress-softening have been proposed only recently. Thus, the studies in the literature are generally based on simplified models. In this paper, an advanced HDNR model, accounting for variation of stiffness and damping with the strain amplitude and deformation history, is used to analyse the seismic performance of isolated structures at different intensity levels. First, a parametric analysis is carried out on a two-degree of freedom system to study different configurations of practical interest. Subsequently, a multi-degree of freedom system representing a realistic building is analysed to evaluate the response at different floors and the contribution of higher modes of vibration. The influence of practical aspects, such as the superstructure damping and the friction of the sliders, is also investigated
BUILDING BACK BETTER: THE CASE STUDY OF THE FAZZINI COLLEGE
Full text linkPassive protection systems have proven to be efficient solutions for the seismic protection of both new and existing buildings. Recently an increasing attention is paid towards their use in external configurations, especially for existing structures since their lower interferences with both the structures to protect and the activities carried on within the buildings. Retrofit and seismic upgrading based on external dissipative elements, indeed, are very promising in post-earthquake phases, making it possible a notable reduction of building downtime and impacts on users. This paper concerns the seismic retrofit of the Fazzini college, an existing r.c. frame building of the University of Camerino severely damaged during the 2016 Central Italy seismic sequence. The retrofit has been designed with an external passive system equipped with fluid viscous dampers aiming to prevent damage to both structural and non-structural components up to severe earthquakes
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