1,721,086 research outputs found
Retrofitting RC infills by a glass fiber mesh reinforced overlay and steel dowels: experimental and numerical study
No full textMany existing Reinforced Concrete (RC) buildings infilled with masonry panels are vulnerable to seismic actions due to lack of proper seismic detailing. For buildings located in low-moderate seismicity regions, a possible retrofitting option could be a reinforced mortar coating applied on the building facades in order to significantly increase its seismic resistance. The present paper studies thin glass fiber mesh reinforced mortar overlays for strengthening RC weak frames infilled with hollow brick masonry. Attention is devoted to the steel dowel connection between the masonry panel and the RC frame to reduce shear sliding. An experimental evaluation of the effectiveness of this enhanced technique is presented and compared against previous results in which shear sliding significantly limited the structural response. In addition, a finite element model has been developed and calibrated to properly simulate the response of the test specimens
Behavior of lightly reinforced fiber reinforced concrete panels under pure shear loading
No full textThe load-deformation response of Fiber Reinforced Concrete (FRC) elements subjected to pure shear is still matter of strong debate within the scientific community. In this paper, the tests on six fiber reinforced concrete panels under pure shear are presented and discussed. The tests were conducted under displacement control and a peculiar loading frame was designed to ensure that a pure shear state of stress was established. Steel fibers were added in relatively low amounts (20 and 50 kg/m3), and two steel reinforcements (0.21% and 0.74%) were selected, aiming at simulating lightly reinforced elements. A critical discussion on the influence of fibers on both global and local behavior (tension stiffening, cracking formation and propagation, post-cracking stiffness and residual strength) is presented. Finally, a novel crack spacing formulation, extended to FRC, is proposed and compared against available experimental data
How Can We Verify Structural Members Made of FRC Only?
No full textThe fib Model Code for Concrete Structures 2010 (MC2010) recognizes fiber reinforced concrete (FRC) as a new structural material, favoring its usage in innovative structural applications. According to MC2010, FRC can be adopted as the only reinforcement in structures provided that both strength and ductility requirements are fulfilled. This paper presents a discussion on the MC2010 requirements for FRC structures applied to both experimental and numerically simulated structural elements, proposing a refined set of equations for the ULS and SLS verification of FRC structures (not containing any classical reinforcement)
Multi-stage optimization and multi-criteria decision-making for HVAC system energy retrofit of a lecture room
No full textThe energy retrofit of a partial recirculation all-air HVAC system serving a university lecture room located in southern Italy is analysed. Mmulti-objective optimization and multi-criteria decision-making are used to find optimal design alternatives and rank them considering two different decision-makers, i.e., public and private stakeholders. The results show that, in the post-pandemic era, baseline retrofit scenarios for infection reduction that do not involve installation of inverter devices and automatic dampers cause energy consumption increase from negligible values up to 59%. Contrariwise, baseline retrofit scenarios involving the installation of inverter and automatic dampers cause energy consumption decrease between 5% and 38%. In this last scenario, for the implementation of further deep retrofit intervention solutions, there is no agreement between decision-makers on the preferable retrofit solution. In the case of operation of the system with 100% outdoor air + inverter and automatic dampers, both stakeholders agree on the same deep retrofit solution
Experimental tests on fiber-reinforced alkali-activated concrete beams under flexure: Some considerations on the behavior at ultimate and serviceability conditions
No full textAlkali-activated concrete (AAC) is an alternative concrete typology whose innovative feature, compared to ordinary concrete, is represented by the use of fly ash as a total replacement of Portland cement. Fly ash combined with an alkaline solution and cured at high temperature reacts to form a geopolymeric binder. The growing interest in using AACs for structural applications comes from the need of reducing the global demand of Portland cement, whose production is responsible for about 9% of global anthropogenic CO2 emissions. Some research studies carried out in the last few years have proved the ability of AAC to replace ordinary Portland cement concrete in different structural applications including the construction of beams and panels. On the contrary, few experimental results concerning the structural effectiveness of fiber-reinforced AAC are currently available. The present paper presents the results of an experimental program carried out to investigate the flexural behavior of full-scale AAC beams reinforced with conventional steel rebars, in combination with fibers uniformly spread within the concrete matrix. The experimental study included two beams containing 25 kg/m3 (0.3% in volume) of high-strength steel fibers and two beams reinforced with 3 kg/m3 (0.3% in volume) of synthetic fibers. A reference beam not containing fibers was also tested. The discussion of the experimental results focuses on some aspects significant for the structural behavior at ultimate limit states (ULS) and serviceability limit states (SLS). The discussion includes considerations on the flexural capacity and ductility of the test specimens. About the behavior at the SLS, the influence of fiber addition on the tension stiffening mechanism is discussed, together with the evolution of post-cracking stiffness and of the mean crack spacing. The latter is compared with the analytical predictions provided by different formulations developed over the past 40 years and adopted by European standards
An innovative multi-stakeholder decision methodology for the optimal energy retrofit of shopping mall buildings
No full textWith the European Green Deal, innovative strategies for building retrofits should focus on implementing
advanced energy efficiency measures and exploiting renewable energies for the reduction of operational CO2
emissions. The energy retrofit process of buildings typically involves several stakeholders with diverse and often
conflicting interests, evaluating potential energy efficiency measures a multi-criteria decision-making (MCDM)
issue that must consider different perspectives of various parties. This paper proposes a hybrid MCDM methodology that integrates several traditional approaches to robustly evaluate and rank feasible building energy
retrofit interventions and applies it to the renovation of an existing shopping mall near Naples, Southern Italy.
The building’s energy model is calibrated and validated using actual energy consumption data from bills, while
the analyses of the building-HVAC system are conducted using the EnergyPlus dynamic energy simulation engine. The alternative retrofit interventions are assessed using three key performance indicators: electric energy
savings, net present value and discounted payback period. The new hybrid MCDM approach is used to rank the
solutions from the different perspectives of various stakeholders: policymakers and building tenants. This
methodology enhances the robustness of the decision-making analysis by reducing method-related uncertainties
and separately addressing different stakeholder perspectives. The results underscore the relevance of renewable
energy sources in building retrofits, both from the energy and environmental standpoint. Moreover, stakeholder
comparative and regret analyses reveal that no common solution exists for the mall retrofit and provide
important insights into how competing interests affect reaching a compromise
New genetic algorithm-based workflow for multi-objective optimization of Net Zero Energy Buildings integrating robustness assessment
No full textNet Zero Energy Buildings (NZEBs) play a key role to save energy. However, unpredictable scenarios and uncertainties about stability of energy production from renewables frequently cause measured performance of the building-plants system that differs from predictions. So, it is crucial to individuate the best alternatives in the early-stage design of the building and related energy systems, also considering uncertain circumstances. Hence, the aim of this paper is to enhance reliability of the building design process by providing an innovative workflow based on multi-objective optimization that encompasses robustness assessment of different design alternatives against uncertain scenarios. The standard genetic algorithm optimization routine has been deeply improved to set as a key performance indicator the robustness of energy performance of several building-HVAC system configurations, also considering the financial aspects optimization. Compliance with NZEB target of the obtained optimal solutions is then automatically verified by the algorithm. The new methodology combines open-source coding language Python and the dynamic energy simulation engine EnergyPlus. The robustness of each solution is evaluated through Taguchi method. First obtained results are related to energy-efficient solutions for the building envelope. Regarding the HVAC system, ground source (instead of air source) heat pumps and variable refrigerating flow systems are preferable. Finally, medium–high size of photovoltaic panels is preferred, although with high investment costs
Influenza del fibrorinforzo sulla duttilità locale, globale e sull’aderenza in travi in c.a. soggette a flessione
No full textL’interesse attualmente rivolto allo studio ed applicazione di calcestruzzi fibrorinforzati è testimoniato dalla recente bibliografia e dallo sviluppo di specifiche normative per la progettazione e controllo di strutture in c.a. rinforzate con fibre.
L’efficacia del rinforzo fibroso nell’incrementare la tenacità degli elementi e la resistenza in fase fessurata è provata in molteplici applicazioni strutturali e non, quali pavimentazioni industriali, pannelli prefabbricati e chiusini.
Obiettivo del presente lavoro è la valutazione dell’influenza delle fibre sulla duttilità strutturale di travi in c.a., attraverso modellazioni teoriche e sperimentali. In particolare un set di sette travi in scala reale realizzate in calcestruzzo con l’aggiunta o meno di fibre di acciaio, e con presenza o meno di aderenza delle barre longitudinali è stato soggetto a prove di flessione su quattro punti. I risultati ottenuti consentono di avere indicazioni sul comportamento in fase fessurata, sui meccanismi resistenti, sullo sviluppo del quadro fessurativo e sulle modalità di collasso. E’ inoltre possibile evidenziare l’influenza delle fibre sulla localizzazione e sviluppo della fessurazione, in presenza o assenza di aderenza.
Le risposte sperimentali sono infine confrontate con i risultati di una modellazione analitica, sviluppata dagli autori. Il modello adottato si basa sullo studio del comportamento di un elemento tra due successive fessure e può tener conto della fessurazione, della non-linearità dei materiali, dell’aderenza tra acciaio e calcestruzzo e degli effetti di localizzazione in prossimità delle fessure.
L’indagine teorico-sperimentale consente di approfondire la conoscenza dell’influenza delle fibre sulla deformabilità e sulla duttilità locale di elementi trav
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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