Seismic retrofit of an existing reinforced concrete building with buckling-restrained braces

Background: The seismic retrofitting of frame structures using hysteretic dampers is a very effective strategy to mitigate earthquake-induced risks. However, its application in current practice is rather limited since simple and efficient design methods are still lacking, and the more accurate time-history analysis is time-consuming and computationally demanding. Aims: This paper develops and applies a seismic retrofit design method to a complex real case study: An eight-story reinforced concrete residential building equipped with buckling-restrained braces. Methods: The design method permits the peak seismic response to be predicted, as well as the dampers to be added in the structure to obtain a uniform distribution of the ductility demand. For that purpose, a pushover analysis with the first mode load pattern is carried out. The corresponding story pushover curves are first idealized using a degrading trilinear model and then used to define the SDOF (Single Degree-of-Freedom) system equivalent to the RC frame. The SDOF system, equivalent to the damped braces, is designed to meet performance criteria based on a target drift angle. An optimal damper distribution rule is used to distribute the damped braces along the elevation to maximize the use of all dampers and obtain a uniform distribution of the ductility demand. Results: The effectiveness of the seismic retrofit is finally demonstrated by non-linear time-history analysis using a set of earthquake ground motions with various hazard levels. Conclusion: The results proved the design procedure is feasible and effective since it achieves the performance objectives of damage control in structural members and uniform ductility demand in dampers

On some properties of the Laplacian matrix revealed by the RCM algorithm

In this paper we present some theoretical results about the irreducibility of the Laplacian matrix ordered by the Reverse Cuthill-McKee (RCM) algorithm. We consider undirected graphs with no loops consisting of some connected components. RCM is a well-known scheme for numbering the nodes of a network in such a way that the corresponding adjacency matrix has a narrow bandwidth. Inspired by some properties of the eigenvectors of a Laplacian matrix, we derive some properties based on row sums of a Laplacian matrix that was reordered by the RCM algorithm. One of the theoretical results serves as a basis for writing an easy MATLAB code to detect connected components, by using the function “symrcm” of MATLAB. Some examples illustrate the theoretical results.The research has been supported by Spanish DGI grant MTM2010-18674, Consolider Ingenio CSD2007-00022, PROMETEO 2008/051, OVAMAH TIN2009-13839-C03-01, and PAID-06-11-2084.Pedroche Sánchez, F.; Rebollo Pedruelo, M.; Carrascosa Casamayor, C.; Palomares Chust, A. (2016). On some properties of the Laplacian matrix revealed by the RCM algorithm. Czechoslovak Mathematical Journal. 66(3):603-620. doi:10.1007/s10587-016-0281-yS60362066

Seismic performance of a reinforced concrete building retrofitted with self-centering shape memory alloy braces

Self-centering earthquake-resistant structures have received increased attention due to their ability to reduce post-earthquake residual deformations and, thus, repair time and cost. This stimulated the development of recentering shape memory alloy (SMA) dampers that use superelastic nitinol wires to dissipate energy and self-center the structure. However, there are still a few case studies applications on full-scale RC buildings in the literature. Moreover, general guidelines or even simplified approaches for the practical design of SMA damped braces are still lacking. This paper focuses on evaluating the effect of using self-centering shape memory alloy dampers for buckling-restrained braces applied for the seismic retrofit of a complex RC building structure. A design method originally proposed for elastoplastic dampers was implemented to size the SMA dampers to be placed on selected spans and stories of a building. The effectiveness of the design procedure was demonstrated by nonlinear time-history analyses under different sets of earthquake strong ground motions. The analysis results show that the recentering shape memory alloy bracing system is effective in limiting the maximum transient inter-story drifts and reducing the residual inter-story drifts after strong seismic events, due to its excellent recentering behavior together with its not negligible energy dissipation capacity

A cost-benefit analysis of the metro line 1 in Naples, Italy

The metro Line 1 in Naples (Italy), also called “Metrò dell’arte” (art in the Metro), is a high-quality line where many international architects were involved to ensure high aesthetic quality standards for the new stations. The “Daily Telegraph” and the CNN, have defined the new Toledo Station, one of the Line 1 metro station, the most impressive station of Europe. The aim of the paper was to evaluate, after five years its realization, the economic convenience of the most impressive section of the metro line. A cost-benefit analysis was the evaluation method performed according to both the National and the EU guide lines. The strengths in developing an “ex-post” analysis are: i) the realization and maintenance costs are exactly known (because just spent); ii) the travel demand (passenger moved by the metro line) are counted through the monitoring system and not estimated through models/surveys. Among the benefits estimated were: travel time and costs saved; hedonic value in using the high-quality metro line; environmental benefit; pollutant reduction; accident reduction; congestion reduction. Overall, the investment cost was about 897 million euro (price 2000), while the architectural high-quality standards cost was only the 6% of the total (50 million euro). Estimation results show that benefits produced by the hedonic value (perceived quality) of the high-quality stations, in 30 years, are 3.3 times higher than its realization costs with about 164 million euros (price 2000) of benefits, the 12% of the total benefits (1,367 million euro). The benefit/costs ratio (one of the measures of effectiveness used in the analysis) was equal to 1.6, sowing the high socio-economic convenience produced by this transport project

The role of particle resuspension within PM concentrations in underground subway systems

High particulate matter (PM) concentrations have been measured on subway networks worldwide, with serious implications for human health. Such concentrations are known to be mainly produced by wear and friction of the metal parts and can accumulate in subways over time, causing a sort of age effect. Surveys have also shown that particle resuspension, caused by train arrivals and departures, significantly increases particulate matter concentrations. The research aim was threefold: (1) to provide a literature review on particulate matter concentrations in urban subway systems; (2) to measure the influence/incidence of the resuspension of PM2.5 and PM10 caused by subway train transit; and (3) to investigate the presence of a subway age effect. A sampling campaign was carried out on the station platforms of the Naples (Italy) Subway Line. The results show that particle resuspension significantly influences PM concentrations, reaching daytime values up to + 1200% greater than those at nighttime. Furthermore, to investigate any age effect, the results were compared with those of a previous study performed in 2014, concluding that, in the absence of tunnel cleaning and/or washing and with a standard ventilation system on station platforms, no statistically significant difference was observed between PM concentrations over the two measurement periods. These results suggest that the particles generated by mechanical wear-and-tear and friction processes constitute a very slow phenomenon. A useful solution could be tunnel washing, thereby removing fine particles that would no longer be available for resuspension

A multi-criteria analysis as a rational evaluation process for building a new highway in Italy

The low accessibility of transportation to the main Italian touristic places (during the summer period) produces road congestion that is often high and negative environmental impacts (externalities). This is the case of the coastal area between Cesena and Venice, which is particularly affected by this phenomenon because of a unique local road, the Romea: it allows car trips among all these touristic places. Beginning from these considerations, the realization of a new highway was proposed, to improve transport accessibility to this area. A Multi-Criteria Analysis (MCA) was identified as the rational evaluation process to verify the sustainability (economic, social and environmental) of this transportation project. The aim of this paper is to describe the MCA evaluation analyses applied to this case study, underlining the main results obtained. One of the main findings of the research was the applied evaluation methodology. A rational and participated weights definition criterion process was implemented, through a “Delphi method” within a Public Engagement process. The MCA results show that the best design alternative is the construction of a highway plus the realization of a “green-way”. Furthermore, we found that the estimated non-user's benefit incidence was about 80% of the total, underlining the appropriateness in using this evaluation method, useful to better quantify non-monetary externalities (versus the cost-benefit analysis). Finally, to verify the robustness of the results we also performed a sensitivity analysis, confirming the main results

Towards E-mobility: Strengths and Weaknesses of Electric Vehicles

One of the greatest environmental challenges worldwide is mobility. In future, increasingly sustainable solutions will be proposed and incentivized and the new technologies, like electric mobility, could (positive) influence mobility performances/habits. The paper aims at critically analyze weaknesses, strengths and application fields of the electric mobility in Italy. Specifically, the electric vehicle today has high production costs, low autonomy and not “zero” environmental impacts deriving from the production, motion and recycling of the vehicle. However, the “local emissions” are null and this pone this technology useful for urban mobility, where high population density often occurs. Furthermore, e-mobility is useful within the new forms of mobility (e.g. MaaS - mobility as a service) where micro mobility, shared mobility, urban bus fleet, freight distribution and an overall higher willingness to pay for users/operators could emphasize the strengths of e-mobility, reducing its weaknesses

Strong sustainability in public transport policies: An e-mobility bus fleet application in sorrento peninsula (Italy)

Sustainability can be defined as the capacity to satisfy current needs without compromising future generations. Sustainable development clashes with the transport sector because of the latter’s high fossil fuels usage, consumption of natural resources and emission of pollutant and greenhouse gases. Electric mobility seems to be one of the best options to achieve both the sustainability goals and the mobility needs. This paper critically analysed weaknesses, strengths and application fields of electric mobility, proposing a real case application of an e-mobility bus fleet in Sorrento peninsula (Italy). The aim and the originality of this research was to propose a public transport design methodology based on a “strong sustainability” policy and applied to a real case study. To be precise, the renewing of the “old” bus fleet with a diesel plug-in hybrid one charged by a photovoltaic system was proposed, aiming to both improve environmental sustainability and perform an investment return for a private operator in managing the transport service. The proposed case study is particularly suitable because the peculiar morphology of the Sorrento peninsula in Italy does not allow other types of public transport services (e.g., rail, metro). Furthermore, this area, rich in UNESCO sites, has always been an international tourist destination because of the environment and landscape. Estimation results show that the new e-mobility bus service will be able to reduce the greenhouse gases emissions up to the 23%, with a financial payback period of 10 years for a private investor

Video tracking for the detection of external load to establish proper parameters in elite soccer players during high intensity training

The video recording and following analysis of games allows sport scientists and coaches to evaluate physical performances of professional soccer players. In particular, can be useful to allows and analyse speed thresholds, accelerations, decelerations and total amount of energy expenditure expressed with metabolic power. It is well known that accelerations are essential to establish sport specific metabolic loads (Di Prampero et al., 2010). Given the obvious importance of a correctly quantifying of metabolic of the various football movements, the aim of this study is to analyse accelerations, decelerations and speed thresholds player by player during matches. Given the obvious importance of a correct metabolic load of the various football movements, the aim of this study wants to analyse accelerations, decelerations and speed thresholds, players by players during matches. The study will also highlight players, into their own field roles, for a better optimization of individual and team project planning