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  Numarul 2/2021

Volumul 12 (2021), Nr. 2 - Vizualizare numar complet

Scurta prezentare a tehnologiei de dezinfectie UVGI
Brief overview on the UVGI disinfection technology
Catalin I. LUNGU, Ilinca NASTASE

The information in this document is useful for HVAC professionals, facility engineers and specialists like employers and building owners and administrators seeking basic knowledge about ultraviolet germicidal irradiation (UVGI) technology. This article explains the specific terms used in the UV field, reasons why UVGI is used for virus inactivation and the main features of UV-C lamps. UVGI device typology is presented, and some general rules and limitations for safe usage are provided. Given the complexity of the UV transmission physics, specific software is needed for sizing UV systems. The sizing guidelines and design examples for different UV-C devices are not included in this document. This annexe scope is general and not limited to any specific building category (e.g., office buildings, educational buildings, shopping areas, sports premises, hospitals, healthcare settings, even residences). However, considering the negative effects on human health and some materials that UV-C radiation could generate when the design is defective, the most important rule is to use only certified products that are properly sized and tested.

Keywords: covid-19, coronavirus, uvgi, uv-c, dose, disinfection

Studiul durabilitatii impotriva carbonatarii betonului formulat cu inlocuirea partiala a cimentului cu pulbere de marmura
Study of the durability against carbonation of the concrete formulated with the partial replacement of cement with marble powder

The first aim of this study is the use of marble waste powder as a partial replacement with cement (CEMI 42.5) in concrete in order to reduce greenhouse gas emissions results in the cement production and consequently on the manufacturing concrete with less environmental impact. Moreover, the carbonation phenomenon influences significantly the durability of reinforced concrete structures, in this context, the second aim of this work is the study of the effect of the accelerated carbonation on the durability of concretes formulated with the cement containing the marble waste (MDP) with different percentages. For this purpose, four concrete mixtures containing 0%, 10%, 15%, and 30% MDP as cement replacement by weight basis have been prepared. These mixtures of concretes were submitted to accelerated carbonation to study their durability against this phenomenon. The series of tests are conducted to study the effect of 10%, 20% and 30% replacement of cement with marble powder on carbonation depth and compressive strength and compare it with the conventional concrete. The result of this present investigation indicates that the carbonation depth increases with the increase of the rate of the replacement of cement with waste marble powder (10 % to 30%) and the compressive strength decreases slightly with the increase of replacement. the compressive strength remains within the acceptable range of M25 concrete.

Keywords: carbonation, concrete, marble powder

Calculul densitatii sarcinii termice pentru birouri clasa A si B
Calculation of fire load for class A and B offices
Ovidiu MIHALACHE, Ion ANGHEL, Iulian-Cristian ENE

Densitatea de sarcina termica din interiorul unui compartiment de incendiu, alaturi de fluxul caldurii degajate de incendiu, reprezinta doi parametri esentiali in domeniul ingineriei securitatii la incendiu, fiind utilizati in special ca parametri de intrare in modelarea incendiilor. Acest studiu incepe cu o prezentare a evolutiei modului in care a fost calculata, de-a lungul timpului, densitatea sarcinii termice. In continuare, sunt redate doua metode de calcul a densitatii sarcinii termice, prima metoda fiind utilizata in conformitate cu standardul SR EN 10903-2: 2016, iar cea de-a doua, in conformitate cu standardul SR EN 1991-1-2-2016. In cadrul celor doua metode sunt analizate doua scenarii: un spatiu cu destinatia de birou clasa A, utilizata de 120 lucrători, caracterizata de o suprafata de 10 m^2 aferenta unui lucrator; un spatiu cu destinatia de birou clasa B, utilizata de 216 lucratori, caracterizata de o suprafata de 5 m^2 aferenta unui lucrator. In ambele scenarii, suprafata celor doua birouri este identica, avand valoarea de 1232,50 m^2. In urma analizei rezultatelor obtinute prin utilizarea celor doua metode se constata ca spatiile cu destinatia de birou utilizate de un numar mai mare de lucratori au o sarcina termica mai mare decat in cazul spatiilor utilizate de mai putini lucratori. Folosind metoda SR EN 10903-2: 2016 se obtin valori mai mari ale densitatii sarcinii termice decat prin folosirea metodei SR EN 1991-1-2-2016. De asemenea, se constata ca riscul de incendiu este mic, valorile densitatii sarcinii termice fiind sub valoarea de 420 MJ/m^2

Cuvinte cheie: densitate de sarcina termica, metode de calcul, birou clasa A si B

In the field of fire safety engineering there are two key parameters being used mainly as input parameters in fire modeling, namely the fire load inside a the fire compartment, along side the heat flow released by the fire. This study begins with a presentation of the evolution of the calculation mode of the heat load density, over time. There are presented two methods of calculating the heat load density, the first method used is according to standard SR EN 10903-2:2016, and the second, in accordance with the standard SR EN 1991-1-2-2016. Two scenarios are analyzed under the two methods: A „class A office room” used by 120 workers, each worker having atributed an area of 10 m2; A „class B office room” used by 216 workers, each worker having atributed an area of 5 m2. In both scenarios, the area of the two offices is identical, at 1,232.50 m2. The results obtained through the use of the two methods show that office rooms used by a higher number of workers have a higher thermal load than the ones used by a smaller number of workers. By using the SR EN 10903-2:2016 method, there were obtained higher values of the fire load as opposed to using the SR EN 1991-1-2-2016 method. The analysis also shown that the fire risk is low, the values of the fire load being under 420 MJ/m^2.

Keywords: fire load, calculation methods, class A and B office

Efectul porozitatii granulelor asupra evolutiei conductivitatii termice a unui beton rasinat expus la temperaturi ridicate
The effect of granulate porosity on the evolution of the thermal conductivity of an resin concrete exposed to high temperatures
Benoudjafer imane, Benoudjafer ibtissam, Tomoaia-Cotisel Maria

As the aggregates occupy about three-quarters of the volume of concrete, it’s not surprising that their properties can, not only, to limit its resistance, but also to affect the durability and structural performance of concrete. In this context, the study's main objective to study the influence of the aggregate porosity on the evolution of the thermal conductivity of a resin concrete exposed to high temperatures. the experimental results show that the porosity of the aggregates has a significant influence on the evolution of the thermal conductivity of the concretes tested.

Keywords: aggregates, porosity, durability, thermal conductivity, concrete, temperature

Studiu comparativ privind coroziunea in timp a electrozilor in sol, Partea 2 – Analize microbiologice
Comparative study regarding corrosion in time of the ground electrodes, Part 2 – Microbiological analyses
Stefan PAVEL, Ioan Bogdan PASCU, Nicoleta NEMES, Romeo NEGREA, Emilia DOBRIN, Oana BURIAC

Obiectivul lucrarii este de a prezenta, aspecte referitoare la: coroziunea metalelor acoperite si neacoperite cu zinc in solul orasului Timisoara (electrozi de impamantare a Instalatiei de Legare la Pamant aferenta Instalatiilor Electrice din Constructii), analiza parametrilor de sol, prototipuri de electrozi, masuratori electrice, microbiologice si analiza de prognoza-predictie matematica, materiale si dictionare de termeni aferenti. Un alt aspect prezentat in acest material este efectuarea de masuratori ale spectrului campului elecromagnetic oscilografiat al elementelor de metal acoperite si neacoperite cu zinc din sol.

Cuvinte cheie: coroziune, electrod de impamantare, sol, legare la pamant, microbiologia solului

The objective of this paper is to present aspects related to: corrosion of metals covered, and not covered with zinc in the soil of Timișoara (grounding electrodes of a grounding installation related to Electrical Installations of Constructions), analysis of soil parameters, prototype electrodes, electrical, microbiological analysis and mathematical prognosis analysis-prediction, materials, and dictionaries of related terms. Another aspect presented in this material are the measurements related to the spectrum of the oscillograph electromagnetic field of the grounding electrodes, which are covered, and not covered with zinc.

Keywords: corrosion, ground electrode, soil, grounding, soil microbiology

Efectul metakaolinului ca inlocuire partiala a cimentului asupra rezistentei la compresiune a mortarelor standard
Effect of metakaolin as partially cement replacement on the compressive strength of standard mortars
Amrane Belaid, Souici Khaled, Hami Brahim, Kennouche Salim, Safi Brahim, Nadir Mesrati

This study presents the effect of incorporating synthesized metakaolin on the compressive strength of standard mortars for a constant water/binder ratio of 0.5. Synthesized metakaolin mixtures with cement replacement of 5, 10, 15 and 20% were tested. From the results, it was observed that 15 % replacement level was the optimum level in terms of compressive strength. Beyond 15 % replacement levels, the strength was decreased but remained higher than the control mixture. Compressive strength of 52 MPa was achieved at 15 % replacement. This investigation has shown that it is possible to produce high strength mortars using local kaolin.

Keywords: metakaolin, mortar

Studiu comparativ intre materialele utilizate pentru proiectarea palelor unui parc eolian
Comparative study between the materials used to design the blades of a wind farm

Aceast studiu a luat in considerare patru alternative, adica materiale plastice din fibre de sticla ranforsate, materiale ranforsate pe baza de fibre de sticla, materiale ranforsate pe baza de fibre de carbon, Kevlar, aliaje de Al5754, Al6082, Al7075 pentru a determina cel mai bun material pentru palele unei turbini eoliene

Cuvinte cheie: materiale compozite, materiale plastice armate cu fibra de sticla, materiale armate pe baza de fibra de sticla, materiale armate cu fibra de carbon.

This study considered four alternatives, namely reinforced fiberglass plastics, fiberglass reinforced materials, carbon fiber reinforced materials, Kevlar, Al5754, Al6082, Al7075 alloys to determine the most good material for the blades of a wind turbine.

Keywords: composite materials, glass fiber reinforced plastics, reinforced materials based on fiberglass, carbon fiber reinforced materials.

Efect de cauciuc reactionat si activat asupra modulului de rigiditate si rezistenta la fisurare a amestecurilor bituminoase
Reacted and activated rubber effect on stiffness modulus and cracking resistance of bituminous mixtures
Zeine E. Boudnania, Bachir Glaoui, M'hamed Merbouh, Jorge B. Soussa

Traditionally, asphalt rubber (AR) mixtures have been difficult to produce. Their production requires specialized plants and equipment, which has resulted in their high cost to manufacture. In part this difficulty is due to the need to produce AR binder by blending it at high temperatures for a significant period of time (typically at about l90°C for 45 min to 1 h). A new technology that produces a reacted and activated rubber (RAR), which is an elastomeric asphalt extender, has been developed by hot blending and activation of a rubber granulate with a selected asphalt binder and activated mineral binder stabilizer. The objective of this study was to evaluate and characterize the performance of Reacted and Activated Rubber (RAR) modified dense graded asphalt mixtures in order to recommend a suitable RAR content to produce a mix that provides superior pavement performance characteristics. The research effort encompassed investigation of shear stiffness modulus and cracking resistance for performance evaluation of six dense graded asphalt mixtures, including one conventional and five modified mixes covering 48 samples. The stiffness modulus was increased as RAR increases, the cracking resistance results showed an increase of fracture energy as RAR increased. 15% RAR was found as the most appropriate content based on its performance characteristics.

Keywords: RAR, bitumen, stiffness, cracking resistance, performance

Sistem de securitate pentru zonele de acces din instalatiile electrice de distributie
Security system for access areas in electrical distribution installations
Cristina Gabriela SĂRĂCIN, Cornel-Ovidiu IVAN

Aceasta lucrare prezinta o solutie viabila pentru asigurarea securitatii instalatiilor fixe de alimentare ale sistemului de distributie electrica. Transmisia energiei electrice catre consumatori casnici sau industriali se face prin retele locale private si prin reteaua publica. In aceste conditii, devine posibil accesul persoanelor neautorizate la instalațiile electrice de distributie. Avand in vedere acest aspect, lucrarea pune accentul pe securitatea distribuitorilor de energie electrica si metodele lor de securizare a zonelor de acces in instalatiile de distributie a energiei electrice. Pentru fiecare zona din cadrul unei instalatii de distributie electrica este identificat nivelul ei de accesibilitate rezultat din gradul de vulnerabilitate. Avand in vedere acest aspect, trebuie luate masuri de securizare a statiilor de distributie pentru a preveni potentialele consecinte negative asupra sistemului de distributie a energiei electrice. Securitatea instalatiilor de distributie electrica in contextul managementului de energie electrica in timp real din cadrul unui dispecerat energetic, conduce la cresterea nivelului de protectie al infrastructurilor critice nationale si europene.

Cuvinte cheie: instalatii electrice de distributie, securitate zone de acces

This paper presents a viable solution for ensuring the security of the fixed power supply installations of the electrical distribution system. The transmission of electricity to domestic or industrial consumers is done through local private networks and through the public network. Under these conditions, it becomes possible for unauthorized persons to access the electrical distribution installations. Given this aspect, the paper focuses on the security of electricity distributors and their methods of securing access areas in electricity distribution facilities. For each area within an electrical distribution installation, its level of accessibility resulting from the degree of vulnerability is identified. In view of this, measures must be taken to secure the distribution stations in order to prevent potential negative consequences for the electricity distribution system. The security of electricity distribution installations in the context of real-time electricity management within an energy dispatcher, leads to increasing the level of protection of national and European critical infrastructures.

Keywords: electrical distribution installations, security access areas

Materiale noi pentru poduri – sticla celulara
New materials for bridges – foam glass
Iulia Andreea Singeorzan

Sticla celulara este un material nou, prietenos cu mediul si economic pe termen lung. Este 100% mineral, produs din sticla reciclata, produsul finit poate fi sub forma de placi sau granule. Sticla celulara este un material foarte usor, rezistent la inghet-dezghet, nedeformabil, rezistent la compresiune, umiditate, temperaturi extreme, daunatori si foc, si poate fi utilizat si in combinatie cu alte materiale precum cimentul, caramida, betonul. O aplicatie inca noua este in domeniul podurilor, unde ofera o alternativă a betonului de umplutura din trotuare. Principalul avantaj fiind greutatea redusa, care duce la o reducere a incarcarii suprastructurii.

Cuvinte cheie: sticla celulara poduri umplutura

Foam glass is a new, environmentally friendly and long-term economic material. It is 100% mineral, made of recycled glass, the finished product can be in the form of plates or granules. Foam glass is a very light material, resistant to frost, non-deformable; resistant to compression, humidity, extreme temperatures, pests and fire and can be used in combination with other materials such as cement, brick, concrete. A still new application is in the field of bridges, where it offers an alternative to concrete filling in sidewalks. The main advantage is the low weight, which leads to a reduction in the load of the superstructure.

Keywords: foam glass bridges filling

Analiza comparativa a influentei principalilor parametri asupra eficientizarii stingerii cu apa a incendiilor
Comparative analysis of the main parameters influence on the efficiency of fire extinguishing using water
Alexandru-Florin CHIOJDOIU, Ion ANGHEL, Valeriu Nicolae PANAITESCU

This study highlights the importance of the concept of firefighting efficiency using water. Thus, are presented the general mechanisms of water for firefighting,manually, using nozzles, and automatically, using fixed system of sprinklers and water mist. A comparative analysis of the influence of the main characteristics of the water jet obtained by the use of nozzles and fixed installations on fire-extinguishing efficiency is carried out, such as the drop size distribution, the flux density and the spray momentum. Also is shown the influence of other parameters on manual and automatic fire extinguishing, such as the size of water droplets, discharge nozzle techniques, longitudinal ventilation speed, and flow rate.

Keywords: efficiency of firefighting, water droplet dimension, sprinklers, water mist

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