Calculation methods of high temperature distribution within structural components and application of these methods to fire resistance assessment

Fire resistance of a building structure is one of important properties which describes the behaviour of the structure exposed to fire. Performance based on codes allows to use calculation methods. Given a satisfactory characterisation of the heat exposure, the designer may then compute how quickly temperatures will increase at various sections within the structural component. There are many calculation methods. They can divided into three groups (Fig 1): using experimental data, using both temperature conduction process and non-stationary thermal conduction. Thermal conduction, temperature conduction and thermal capacitance are general properties for temperature prediction methods. Usually building materials have thermal characteristics for normal environment, which can not exactly describe material properties at high temperatures. But many calculation methods lack accurate thermal characteristics describing building material properties at high temperatures. This article is intended for the analysis of this question. First Published Online: 30 Jul 201

Fire tests on wood products subjected to different heat fluxes

The paper analyses three different wood products used for research exposing them to the surface heat flow density of 30 kW/m2, 50 kW/m2 and 70 kW/m2 and applying the test method described in ISO 5660–1 Reaction‐to‐fire tests – Heat release, smoke production and mass loss rate – Part 1: Heat release rate (Cone calorimeter method). Research was performed applying 18 mm and 29 mm thick laminated wood chipboards and 24 mm thick medium density fibreboard. The paper provides an overview of the fire properties of wood products and discusses testing methods and the percentage composition of the tested wood products. Mean time to their ignition was determined. The mean values of the maximum heat release rate and time required to achieve them were investigated. Furthermore, the measurements of the released heat and efficient heat of combustion were taken. Further research covers the performance of statistic analysis, deriving empiric equations, correlation and determination coefficients, standard errors and Student criterion. The results of research are summarized. Conclusions are provided at the end of the paper. Santrauka Straipsnyje nagrinejami trys skirtingi medienos gaminiai, su kuriais atlikti tyrimai veikiant 30 kW/m2, 50 kW/m2bei 70 kW/m2 paviršiniais šilumos srautais taikant ISO 5660–1 “Reaction‐to‐fire tests – Heat release, smoke production and mass loss rate – Part 1: Heat release rate (Cone calorimeter method)” bandymo metoda. Tyrimai atlikti su 18 mm ir 29 mm storio laminuotomis medžio drožliu plokštemis bei 24 mm storio vidutinio tankio plaušo plokšte. Darbe apžvel‐giamos medienos gaminiu gaisrines savybes. Aptariama bandymo metodika ir tirtu medienos gaminiu procentine sudetis. Nustatytas vidutinis laikas iki ju užsidegimo. Ištirti vidutiniai maksimalios šilumos išsiskyrimo greičio ir laiko iki ju pasiekimo dydžiai, taip pat išmatuota visa išskirta šiluma ir efektyvi degimo šiluma. Atlikta statistine analize, gautos em‐pirines lygtys, koreliacijos bei determinacijos koeficientai, standartines paklaidos bei Stjudento kriterijai. Apibendrinami tyrimo rezultatai. Darbo pabaigoje suformuluojamos išvados. First Published Online: 10 Feb 2011 Reikšminiai žodžiai: laikas iki užsidegimo, laikas per kuri pasiektas maksimalus šilumos išsiskyrimo greitis, maksimalus šilumos išsiskyrimo greitis, visa išskirta šiluma, medienos gaminiai, gaisrines savybe

The regulation of structural parameters of ceramics depending on the drying regime

Always in the shaped semimanufactures of ceramics is some humidity, which we must eliminate before burning. Drying process is to safeguard the satisfactory strength of semimanufactures. Additionally, changes of ceramic samples capacity is to end the drying process, associated with elimination of humidity that would not compose defects ‐ gaps, fractures, fragmentation etc. In this work it was shown, how the selected stages of drying regime influence the structural parameters of ceramics (reserve of porous volume, heterogeneity degree of structure, maximum rate of capillary rise according to watering front, capillary rate of mass flow, water absorption) and vice verse, how the selection of the dimensions of the stages for drying regime depends on the desired values of the of ceramics. Santrauka Džiovinimas gaminant keraminius dirbinius yra labai svarbus technologinis procesas, nes džiovinant turi baigtis keraminių bandinių tūrio pokyčiai, susiję su drėgmės pasišalinimu, kad neatsirastų defektų – plyšių, įtrūkių, nuskilimų ir t. t. Darbe buvo išnagrinėta, kaip džiovinimo režimo parinkimas gali lemti defektų atsiradimą ir tokias struktūrines keraminių bandinių charakteristikas, kaip poringosios erdvės rezervas, struktūros nevienalytiškumo laipsnis, maksimalus kapiliarinio pakilimo pagal drėkinimo frontą greitis, kapiliarinis masės srauto greitis ir vandens įmirkis. Tikslui pasiekti keraminiai bandiniai buvo paruošti parinkus 8 džiovinimo režimus, o kitus technologinius veiksnius (formavimo mišinio sudėtis, degimo temperarūra, temperatūros kėlimo greitis degant ir kt.) palikus nekintamus. Nustačius keraminės šukės struktūrines charakteristikas ir atlikus gautų duomenų statistinę analizę, buvo sudarytos empirinės lygtys. Pagal jas buvo pagrįsta, kaip kiekvienas parinktas džiovinimo režimo etapo dydis lemia struktūrinių rodiklių verčių kitimą ir kaip galima reguliuoti džiovinimo režimą, norint gauti tam tikras struktūrinių charakteristikų vertes. Reikšminiai žodžiai: keramika, struktūriniai rodikliai, džiovinimo režimas, statistinė analizė. First Published Online: 14 Oct 201

The effect of concrete composition and aggregates properties on performance of concrete

The properties of the hardened concrete depend on the selected raw materials: size and amount of the particles of coarse aggregate, as well as on the ratio of other components. Particular countries use various methodologies for the selection of concrete composition to select the components of the concrete mixture. However, the properties of the concrete, selected by using any methodology for the selection of the concrete composition and hardened by following the defined conditions, must satisfy the values of certain necessary characteristics. The results of the implemented research indicate that the most optimal solution is to use the coarse aggregate of multi‐fractional or discontinuous fractional composition. The optimal composition of the concrete must be selected to ensure that the binding material is not overdosed. Yet, all components must be selected in such a way, that the required properties of the final product are retained after concrete mixture hardens. When catalyst waste materials from the reactor of the catalytic cracking (15%) are used for the lightweight concrete, the density of the expanded‐clay lightweight concrete investigated and compressive strength increases even for the higher water/cement ratio, more heat is dissipated during the hydration of the cement and this exothermic effect occurs several hours earlier. Santrauka Sukietėjusio betono savybės priklauso nuo betonui parinktų žaliavų: stambaus užpildo dalelių dydžio ir jų kiekio, taip pat nuo kitų sudedamųjų dalių santykio. Betono mišinio sudedamąsias dalis šalys parenka įvairiais betono sudėties parinkimo metodais, tačiau pagal bet kurį betono sudėties parinkimo metodą parinkto ir pagal nustatytas sąlygas sukietinto betono savybės turi tenkinti tam tikrų būtinųjų charakteristikų vertes. Darbe atliktų tyrimų rezultatai parodė, kad optimaliu naudoti daugiafrakcį arba trūkiosios frakcinės sudėties stambųjį užpildą. Betono sudėtis turi būti parinkta nepereikvojant rišamosios medžiagos, tačiau visas sudedamąsias dalis parenkant taip, kad, sukietėjus betono mišiniui, išliktų reikiamos galutinio produkto savybės. Lengviesiems betonams naudojant katalizatoriaus atlieką iš katalitinio krekingo reaktoriaus (15 %), padidėja tiriamojo keramzitbetonio tankis, gniuždomasis stipris net esant didesniam V/C santykiui, o hidratuojantis cementui, išsiskiria daugiau šilumos, ir šis egzoterminis efektas įvyksta keliomis valandomis anksčiau. First Published Online: 14 Oct 2010 Reikšminiai žodžiai: betonas, užpildai, keramzitas, struktūriniai rodikliai, katalizatorius, egzotermijos temperatūra

Research of natural wood combustion and charring processes

Wood is a material widely used for construction purposes and – in some cases – it is the main element of building structures. In comparison with other materials, wood has a number of advantages, such as lightness, strength, resistance to impacts and vibration, simplicity in terms of processing and etc. However, one of the largest drawbacks of wood is flammability. Charring of wooden structures is the most apparent feature of combustion in case of fire in wooden buildings or buildings made of wooden structures. This property is important in identifying causes of fire; therefore it is necessary to relate charring of wooden structures with certain significant effects of fire, such as its duration or temperature. The article addresses the wood characteristics that impact on combustion and charring. It describes test methods and properties of wood samples under research. Research of charring rate of natural softwood and hardwood as a function of heating time, and regressive analysis of data were carried out. Empiric equations were derived. The calorific value of carbon residue resulting in different temperatures was determined in accordance with LST EN ISO 1716. Thermographic research of oak and pine wood was carried out in different gaseous environments. The research results were summarised in the form of conclusions

Research on the electrical capacitance and electrical conductivity of char resulting from natural and treated wood

Wood is a material widely used for construction purposes and having quite a number of advantages. However, one of the major drawbacks of wood are its flammability. In case of fire in wooden buildings or constructions made of timber structures, the most noticeable feature of combustion is charring these structures. This property is important for identifying the cause of a fire. Therefore, it is necessary to relate charring timber structures with certain significant effects of fire such as its duration or temperature. It is also particularly important to identify whether timber has been treated with fire retardant solutions before the fire break-out. The values of electrical capacitance and conductivity for the media obtained from char resulting from natural wood and that treated with fire retardant solutions and dispersed in distilled water depending on heating time have been determined. Moreover, it has been stated that the electric conductivity of char resulting from natural wood is 100 times lower, and the electrical capacitance of such char is 1000 lower than those resulting from treated wood. The regression analysis of the obtained data has been performed. The empirical equations have been derived. The results of the conducted research have been summarised. Priority has been given to the application of the method evaluating electrical conductivity

Possibilities to recycle auto glass waste in building ceramics

Substantial amounts of glass waste end up in landfills because unlike ordinary glass, auto glass is unsuitable for recycling in the glass industry due to organic additives. However, it was determined that the additives make auto glass waste appropriate for the production of building ceramics, which results in improved physical-mechanical and structural properties. The optimum quantity of the additive contained in auto glass waste amounts to 15% of the formation mixture, and the most appropriate burning temperature is 1080 °C. The density of such ceramic chip is 2059 kg/m3 , the water absorption determined after 72 h is 1.2%, and the forecasted frost resistance at the beginning of decomposition is 1343 cycles, but amounts to 2188 cycles at the end of decomposition

Prediction of temperature of standard fire exposure

 This article describes equations derived to predict the duration of local pyrolytic charring under standard fire conditions. The equations consist of five variables: electrical capacity, electrical conductivity, calorific value, depth and rate of char. The equations are split up into two groups: one for the formation of non-impregnated carbonaceous residue, and one for impregnated carbonaceous residue during pyrolysis. This means that before predicting the local duration of charring, it is necessary to determine whether the wood has been impregnated with a fire retardant solution before the fire. Electrical conductivity and electrical capacity measurement methods were used for this purpose. The temperature of standard fire local exposure is calculated by predicting the duration of local pyrolytic charring according to the standard temperature and the time dependence of fire

Peculiarities of destruction mechanism of polymeric intumescent fire protective coatings

The article describes the destruction mechanism of intumescent fire protective paint coatings at the time of their aging under the impact of simulated climatic factors. Steel plates covered in anti-corrosion varnishes and intumescent fire protective paint coatings of several types and different composition were used in the research, while certain samples were also additionally covered in protective coatings protecting from environmental effects. SEM, DTA and FT-IR researches were conducted on control samples and samples after aging. Aging was performed in 3 ways: according to regimes I and II in the laboratory and having stored them for 12 months under the outdoor conditions under the roof. The aging mechanism of materials was determined to be very similar when using different methods of aging: with increasing number of cycles, the extent of damage to the surfaces and their diversity increase. In all cases, chemical material changes were observed after artificial aging cycles compared to control samples. In aged samples, there were some new connections occurring, while others changed or disappeared judging from the number of waves and intensity of peaks, which shows that certain compounds form, while others change and disintegrate under the influence of environmental heat and mass exchange

Substantiation of new standard methods for definition of operational frost resistance of facing protections and concrete/Atitvarų apdailos ir betono eksploatacinio atsparumo šalčiui nustatymo naujų standartinių metodų pagrindimas

Darbe pateikiamas analizinis ir eksperimentinis naujų standartinių metodų, kuriais nustatomas konstrukcinių kompozitų ir betonų atsparumas šalčiui vienpusio šaldymo būdu, pagrindimas. Remiantis ilgamečių tyrimų rezultatais stebėta ir tirta statinių ir atitvarų būklė ir jos kitimas eksploatacijos sǎjygomis, taip pat ir panašių medžiagų bei konstrukcijų irimo procesai modeliuojant eksploatavimo sǎlygas laboratorijoje. Bandinių ar gaminių atsparumas šalčiui buvo tiriamas klasikiniu tūrinio šaldymo ir mūsų pasiūlytu vienpusio šaldymo būdu specialiu režimu. Tyrimų rezultatai buvo apdorojami matematikos statistiniais metodais. Nustatyta, kad eksploatacinio atsparumo šalčiui markę lemia ir konkreti bazinė metodika, ir gaminių kokybė įvairų savybių požiūriu ir kad apdailos medžiagos irsta panašiai kaip fasadinė keramika. Manyta, kad mūsų gauti rezultatai netinka betonui. Abejonėms išsklaidyti buvo atliktos dvi serijos tyrimų su įvairių rūšių betono bandiniais. Nustatyta, jog ir mūsų sukurtu vienpusio šaldymo, ir klasikiniu tūrinio šaldymo būdu gauti rezultatai pasižymi didele sklaida. Tai pagrindžia būtinumą mūsų metodą taikyti minėtoms medžiagoms ir gaminiams. Iki šiol Lietuvoje galiojančiose statybos normose ir taisyklėse sienų konstrukcinių medžiagų ir gaminių, ilgalaikiškumo ir atsparumo šalčiui markės sąryšis neatitinka tikrovės. Ši problema standartuose sprendžiama atitinkamų medžiagų bei gaminių eksploatacijos sąlygų arba ilgalaikiškumo bei eksploatacinio atsparumo šalčiui markių nauju sąryšiu ir klasifikacija. First Published Online: 26 Jul 201