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This research is based on the testing of the impact of the board (particleboard and medium density fiberboard (MDF)) and hardware type used to connect the sides and the bottom or top of the storage furniture on the joint strength. The hardwares of the following trade mark were used: the confirmat screw, Minifix, Maxifix, Stablofix, RV and Solo 32. Such hardwares make it possible to disassemble the furniture as well as to assemble it (when moving the furniture) without reducing joint strength when reassembling it due to wear and tear on the material (with the exception of the confirmant screw). Research results showed that assemblies with the Maxifix hardware installed in the MDF base exhibited the highest values of bending moment (the average bending moment of 85.88 Nm). On the other hand, assemblies with the Minifix hardware installed in the particleboard exhibited the lowest values of bending moment (over three times lower than the Maxifix) (the average bending moment of 24.50 Nm). Assemblies with the confirmat screw exhibited satisfactory results, although, aesthetic requirements seem to be the main problem here (the average bending moment of 40.38 Nm for the particleboard and of 64.24 Nm for the MDF)., Istraživanje se temelji na ispitivanju utjecaja vrste drvne ploče (iverice i MDF ploče) i tipa okova koji služi za povezivanje stranice i poda ili stropa namještaja za odlaganje na čvrstoću kutnog spoja. Kao spojni okov rabljeni su oni trgovačkog naziva confirmat vijak, minifix, maxifix, stablofix, RV i solo 32. Navedeni okov omogućuje rastavljanje i sastavljanje namještaja (npr. prilikom selidbe namještaja) a da pri ponovnom sastavljanju ne bude narušena čvrstoća spoja zbog habanja materijala (izuzetak je confirmat vijak). Prema rezultatima istraživanja, najveće vrijednosti momenta savijanja zabilježene su u sastava s maxfix okovom ugrađenim u podlogu od MDF ploče (prosječni moment savijanja 85,88 Nm). Najmanje vrijednosti momenta savijanja (preko tri puta manje u usporedbi s maxifixom) izmjerene su za sastav s minifix okovom koji je ugrađen u ploču ivericu (prosječni je moment savijanja 25,40 Nm). Spojevi s confirmat vijkom pokazuju zadovoljavajuće rezultate momenta savijanja, ali su estetski zahtjevi glavni problem tog načina povezivanja elemenata (prosječni moment savijanja za troslojnu ploču ivericu iznosi 40,38 Nm, a prosječni je moment savijanja za MDF ploče 64,24 Nm).

The system for measuring the welding temperature with measuring probes has been developed for the requirements of this but also of future research (at the Faculty of Forestry and Wood Technology, University of Zagreb). The research is based on determining the welding temperature and its impact on the joint strength or the embedded force of the dowel. Based on research results, the impact of the dowel rotation frequency and temperature on the joint strength has been determined. The measured welding temperature increased as the rotation frequency increased (the rotation frequencies of 865 min-1 and 1520 min-1 were used in the research). The maximum welding temperature in pine samples welded at the rotation frequency of 1520 min-1 amounts to 217 °C, while in samples welded at the rotation frequency of 865 min-1 it amounts to 179 °C (weld penetration of 20 mm). The maximum welding temperature in beech samples welded at the rotation frequency of 865 min-1 amounts to 181 °C, and 213 °C at the rotation frequency of 1520 min-1 (weld penetration of 20 mm). The impact of the wood type on the welding temperature has not been proven. In order to avoid difficulties encountered in contact measurement of the welding temperature, a heat transfer model was developed for a more precise determination of the welding temperature., Za potrebe ovoga, ali i budućih istraživanja na Fakultetu šumarstva i drvne tehnologije Sveučilišta u Zagrebu razvijen je sustav za mjerenje temperature zavarivanja uz pomoć mjernih sondi. Istraživanje se temelji na određivanju temperature zavarivanja te na njezin utjecaj na čvrstoću spoja odnosno na izvlačnu silu moždanika. Na temelju rezultata istraživanja utvrđen je utjecaj frekvencije vrtnje moždanika i temperature na čvrstoću spoja. S povećanjem frekvencije vrtnje povećava se i izmjerena temperatura zavarivanja (u istraživanju su primijenjene frekvencije vrtnje od 865 min-1 i 1520 min-1). Najveća temperatura zavarivanja uzoraka borovine frekvencijom vrtnje od 1520 min-1 iznosila je 217 °C, dok je za uzorke zavarene frekvencijom vrtnje od 865 min-1 najviša temperatura zavarivanja iznosila 179 °C (dubina zavarivanja bila je 20 mm). Za uzorke bukovine zavarene frekvencijom vrtnje od 865 min-1 najviša temperatura iznosila je 181 °C, dok je za uzorke zavarene frekvencijom vrtnje od 1520 min-1 najviša temperatura zavarivanja bila 213 °C (dubina zavarivanja iznosila je 20 mm). Utjecaj vrste drva na temperaturu zavarivanja nije dokazan. Kako bi se izbjegle poteškoće pri kontaktnom mjerenju temperature zavarivanja, radi preciznijeg određivanja temperature zavarivanja razvijen je model prijenosa topline.

A rotary welded joint is a combination of wood in which chemical and physical reactions occur due to friction. During the welding process, heat is generated which softens and melts the wood structure. In this way, interlocked wood fibres in the lignin melt are created within the joint. As the welded joint cools down, it becomes a tight weld. The paper describes the research based on studying the impact of individual factors on the welded joint. Outcome variables are the average ring width, the water content in the wood, and the influence of different humidity levels on the strength of rotary welds. Samples were subjected to the influence of different humidity levels achieved by air conditioning, magnesium chloride and sodium chloride. Absolutely dry samples exhibited the lowest embedded force values (the average embedded force value for heartwood amounted to 1901 N and for sapwood 1920.36 N), while the air conditioned samples (the average embedded force value amounted to 2649.06 N; for sapwood 2679.6 N and for heartwood 2619.6 N). The samples exposed to sodium chloride (the average embedded force value amounted to 2907.7 N; for sapwood 2766.07 N and for heartwood 3049.33 N) exhibited the highest embedded force values. This paper presents a descriptive statistical analysis of the strength of rotary welded dowels in the pine base. The aim of the study was to research the influence of different air humidity levels on the embedded force of Scots pine rotary welds. As the air relative humidity and temperature change during the daily application of the product (which affects the moisture content in the wood), the knowledge on the influence that humidity and water content in the wood exert on the welded joint strength turns out to be of great importance for its use.

Thermal comfort is related to human physiological reactions. In order to maintain a constant internal temperature, the human body must dissipate heat in a warm climate, and prevent heat losses in a cold climate. The overall sensation of comfort accompanies the warmest part of the body in a warm environment and the coldest one in a cold environment. Chair design and clothing may affect the difference in sensitivity between certain parts of the body, that is, they may affect thermal comfort. This research focused on subjective sensation of warmth and moisture while sitting on offi ce chairs. The subjective method of evaluating thermal discomfort is based on ISO7730:2005 standard, according to which a questionnaire was made for this research. Six subjects took part in the research. They were sitting on fi ve different offi ce chairs as they performed their usual jobs in controlled conditions. From the point of view of the evaluation of the sensation of warmth, all chairs were evaluated neutrally. The sensation under the buttocks and thighs was reported to be somewhat warmer, while the sensation on the back was reported to be somewhat colder, which was affected by the design of the back of the chair. No correlation has been proven between the actual temperature and moisture measurements and subjective evaluations of thermal comfort, in spite of a number of direct links. The use of the present method offers the possibility of further research into this subject, which would prove more thoroughly a correlation between design and construction solutions of office chairs and the comfort perceived by sitting persons.

Experimental determination of the elastic constants of orthotropic composite materials and their bearing capacity (strength) for furniture intended for sitting, and numerical verification of the experiment results by analysing with the final elements, was performed on the basis of the theory of elasticity of orthotropic and anisotropic composite materials. The requisite and sufficient material constants were determined in the experiments: moduli of elasticity and Poisson’s coefficients (longitudinal and tangential) and skate modulus for plain stress. These constants, calculated by 3D measurements of deformation, are sufficient for determining the constitutive matrix of the lamina, and for reducing stiffness of the composite irrespective of the thickness of the layers, fibre orientation and choice of material. Experiments were conducted for the stiffness, shear and flexing of uniformly and complexly layered beech veneer sheets, while for new materials experiments for stiffness and shear in a uniform orientation were sufficient. Analysis of stiffness and deformations were conducted layer by layer, as well as by reduced volume stiffness for multi-layered orthotropic shells of chair systems by a method of final elements by application of a composite final element, where combined reduced membrane matrices and flexing matrices are used. Numerical verification of the experiments, including systems of furniture intended for sitting – chairs – was conducted using the KOMIPS software system, which contains in its library a composite final element of the sheet. Experiments with chairs were performed with the aim of determining the stiffness of such systems, and they were confirmed by analytical results and measurement of the real movements on selected models. The results of research provide the design, re-design, construction and determination of the dimensions of not just chairs, but also of any other girder or surface system based on laminates.

Tehnika rotacijskog zavarivanja drva noviji je način spajanja drvenih dijelova bez upotrebe ljepila, uz pomoć topline koja nastaje trenjem elemenata koje spajamo. Tijekom procesa zavarivanja zbog utjecaja tlaka i topline rastali se površinski sloj drva (lignin i drvne polioze) koji je u međusobnom kontaktu. Istraživanje se temelji na ispitivanju utjecaja toplinske modifikacije i vode (sobne temperature) na čvrstoću zavarenog spoja. Ispitni su uzorci bili dužinski spojeni tokareni elementi izrađeni od bukovine. Toplinski modificirano drvo može se uspješno zavarivati. Rezultati istraživanja pokazali su da se s porastom temperature toplinske modifikacije i potapanjem uzoraka u hladnu vodu (20 °C) izvlačna sila, odnosno čvrstoća spoja smanjuje s porastom gubitka mase pri termičkoj modifikaciji smanjuje se izvlačna sila. U uzoraka koji su bili izloženi utjecaju vode najveća je čvrstoća spoja zabilježena pri zavarivanju drva modificiranoga na 140 °C, a najmanja pri zavarivanju drva modificiranoga na 180 °C.

Construction of the seat and back of the office chair, as an actual object of the human working environment, is important in its final design since these are the elements that are in a direct and close contact with human body. The sitting position is the most frequent working position of the modern man in the developed world. Independently of the type of work, a sound and physiologically correct sitting position diminishes fatigue during work and strain of the spine, and suitable posture during sitting significantly contributes to the increase of concentration and efficiency. Sitting as a working position can be examined through coordination of anthropometric sizes and form of the seat and back, or mechanically, by determining the relation between the user and the seat quality, where the comfort index or support factor has a great influence. The comfort index as one of the factors of sitting comfort is the result of mechanical characteristics of the observed chair. This paper shows the results of ‘’mechanical comfort’’ that the chair can offer to the user. The results of determining the seat comfort on office chairs are featured through comfort index obtained from elastic characteristics of materials in the seat, but also of the chair itself according to Technical Specifications HRS ENV 14443.

The studies of office chair constructions have identified differences in perception of comfort provided by different types of seats. Four seat constructions and the comfort provided to the users were compared by means of subjective indicators. After a two-day sitting on each of the studied chairs, the subjects scored their perception of comfort and discomfort, using the questionnaire with 17 statements. Unlike most similar studies, subjects evaluated seats on their own work places and in the environment to which they are accustomed. Constructional forms of the seat and materials that contributed more to the sense of comfort by minimizing fatigue and pains developed by sitting were determined. Results have shown that the chair with a net is significantly more comfortable than other chairs. The chair with molded PU foam is significantly more comfortable than the chair with springs, but statistically it does not differ significantly from the chair with slabstock PU foam. It has been concluded that the chair with a net got higher scores, which might be attributed to its frame construction and the absence of a hard base under the sitting surface., Istraživanjem konstrukcija uredskih stolica utvrđene su razlike u osjećaju udobnosti sjedenja na različitim sjedalima. Uspoređene su četiri konstrukcije sjedala i njihove udobnosti za korisnika, i to na temelju subjektivnih pokazatelja. Ispitanici su nakon dvodnevnog sjedenja na stolici ocjenjivali osjećaj udobnosti ili neudobnosti odgovarajući na upitnik sa 17 ponuđenih tvrdnji. Za razliku od većine sličnih istraživanja, ispitanici su ocjenjivali sjedala na svojim radnim mjestima i u okolini na koju su naviknuli. Ispitivanjem su određeni konstrukcijski oblik sjedala i materijali izrade stolica koje pridonose osjećaju veće udobnosti time što minimaliziraju osjećaj zamora i pojavu bolova pri sjedenju. Rezultati su pokazali da je stolica s mrežom znatno udobnija od ostalih. Stolica s hladno lijevanom PUR spužvom mnogo je udobnija od stolica s oprugama, ali se statistički ne razlikuje od stolica s rezanom PUR spužvom u sjedalu. Zaključeno je da je stolica s mrežom najbolje ocijenjena zbog njene okvirne konstrukcije i zato što ispod površine za sjedenje nema tvrde podloge.

At the moment there are more than 40 framesaws in use in Croatia, and many framesaw operators have a serious spine problem. Complex measurements have been carried out in order to determine the vibration level on the operator's seat. This paper reports and analyzes the measurement results of the whole-body vibration transmitted to a framesaw operator during an ordinary working day. Vibrations were measured at all operations performed during the normal framesaw working cycle. For all the measurements frequency spectra were obtained and the results graphically represented according to the ISO 2631-1-1986 recommendations. The weighted r.m.s. acceleration was also calculated and the duration of each single framesaw operation was measured. The energy-equivalent vibration level, corresponding to the total duration of exposure was calculated, too. The values so obtained were compared with the daily exposure limits according to the ISO 2631-1-1997. The measurement results showed that the framesaw operator, under the given measuring conditions, is exposed to a higher vibration level than the given daily exposure limits. Also, the energy-equivalent vibration level calculated according to the guidelines given in the new ISO 2631-1-1997 is higher than the limits recommended for an effective 4-h daily exposure.

This paper presents a numerical procedure for the analysis of complex laminate structures. The procedure is based on the application of reduced stiffness of complex laminate. Introduction of reduced stiffness of composite facilitates both linear and nonlinear numerical integration, i.e. the tangential stiffness matrix is translated in the classical plate theory problem. The formulated numerical procedure was implemented in the program system KOMIPS. Special subroutine REDKRUT that calculates reduced stiffness of the laminate was written, and its application in numerical verification of experiments conducted on chairs was presented in (Nestorovic, 2010). At the end of this work, for 3D stress and strain analysis of veneer composites, recommendations were given for experimental determination of all nine independent material constants Ex, Ey, Ez, vxy, vxz, Gxy, Gxz, Gyz, fi ve of which were determined in the previous paper of the author (Nestorović, 2010)., Rad prikazuje numeričku proceduru za analizu struktura izrađenih od kompleksnih laminata. Postupak se temelji na primjeni reducirane krutosti komplesnog laminata. Uvođenjem reducirane krutosti kompozita numerička se integracija, kako linearne, tako i nelinearne, odnosno tangencijalne matrice krutosti, prevodi u problem klasične teorije ploča. Formulirana numerička procedura implementirana je u sklopu programskog paketa KOMIPS. Napisana je posebna subrutina REDKRUT, kojom se proračunavaju reducirane krutosti laminata, a njegova primjena u provjeri numeričkih eksperimenata provedenih na stolcima prikazana je u radu (Nestorovic, 2010.). Za 3-D analizu naprezanja i deformacija furnirskih kompozita na kraju ovog rada dane su preporuke za eksperimentalno određivanje svih devet neovisnih materijalnih konstanti: Ex, Ey, Ez, vxy, vxz, Gxy, Gxz, Gyz, od kojih je pet određeno u prethodnom autoričinu radu (Nestorović, 2010.).

When using an office chair, a person comes into direct contact with the seat, where the contact surface creates a microclimate that affects the person’s positive or negative mood, depending on temperature and humidity. Relative to temperature and moisture, this microclimate may produce either a positive or a negative effect on a seated person. Foam based padding of seats and backrests have upholstery with insulating properties that prevent the escape of bodily heat and moisture. The present work, carried out with six subjects, was aimed at studying temperature and moisture as the contributing factors to sitting comfort during performance of usual tasks under controlled conditions. The study method employed temperature and moisture measurements on fi ve different offi ce chairs using the probes placed on or in the seats. The statistically evaluated results of objective measurements show signifi cant differences in distribution of temperature and moisture among the tested seats and through different layers of padding materials and upholstery of individual seats. Generally, it may be concluded that the temperature on the seat surface is always higher than inside the seat. On the other hand, humidity is always lower on the seat surface. Temperature and moisture on the surface of moulded foam seats are higher than on other kinds of seats.

Thermal comfort is related to human physiological reactions. In order to maintain a constant internal temperature, the human body must dissipate heat in a warm climate, and prevent heat losses in a cold climate. The overall sensation of comfort accompanies the warmest part of the body in a warm environment and the coldest one in a cold environment. Chair design and clothing may affect the difference in sensitivity between certain parts of the body, that is, they may affect thermal comfort. This research focused on subjective sensation of warmth and moisture while sitting on offi ce chairs. The subjective method of evaluating thermal discomfort is based on ISO 7730:2005 standard, according to which a questionnaire was made for this research. Six subjects took part in the research. They were sitting on five different office chairs as they performed their usual jobs in controlled conditions. From the point of view of the evaluation of the sensation of warmth, all chairs were evaluated neutrally. The sensation under the buttocks and thighs was reported to be somewhat warmer, while the sensation on the back was reported to be somewhat colder, which was affected by the design of the back of the chair. No correlation has been proven between the actual temperature and moisture measurements and subjective evaluations of thermal comfort, in spite of a number of direct links. The use of the present method offers the possibility of further research into this subject, which would prove more thoroughly a correlation between design and construction solutions of office chairs and the comfort perceived by sitting persons., Toplinska ugodnost povezana je s fiziološkim reakcijama osoba. Kako bi zadržalo stalnu unutarnju temperaturu, tijelo mora oslobađati toplinu u toploj klimi, a sprečavati gubitke topline u hladnoj klimi. Ukupan osjećaj udobnosti prati najtopliji dio tijela u toplom okružju i najhladniji u hladnom okružju. Dizajn stolca i odjeća mogu utjecati na razliku u osjetljivosti između nekih dijelova tijela, odnosno mogu utjecati na toplinsku ugodnost. U radu su istraživani subjektivni osjećaji topline i vlage pri sjedenju na uredskim radnim stolcima. Metoda subjektivne procjene toplinske udobnosti temelji se na normi ISO 7730:2005, prema kojoj je napravljen upitnik za ovo istraživanje. U ispitivanju je sudjelovalo šest ispitanika koji su sjedili na pet različitih uredskih stolaca za vrijeme obavljanja uobičajenih radnih zadataka u kontroliranim uvjetima. Sa stajališta procjene osjećaja topline, svi su stolci ocijenjeni neutralno. Ispod stražnjice i bedara osjećaj topline procijenjen je nešto većim, a osjećaj na leđima hladnijim, na što je utjecao dizajn naslona. Korelacije realnih mjerenja temperature i vlage sa subjektivnim procjenama toplinske udobnosti nisu dokazane, unatoč nekolikim izravnim poveznicama. Rad i prikazana metoda otvaraju mogućnost za daljnja istraživanja te problematike kojima bi se detaljnije dokazala korelacija između oblikovno-konstrukcijskih rješenja radnih stolaca i udobnosti sjedenja na njima.

Spajanje drva klinovima bez ikakva lijepljenja i zavarivanja bilo je koristeno stoljecima. Ako ti klinovi (u ovom istraživanju moždanici) rotiraju prilikom spajanja s podlogom (u kontroliranim uvjetima), uz određene parametre nastaje cvrsti spoj znatne cvrstoce. Zavarivanje drva je proces u kojemu se zbivaju kemijsko-fizikalne reakcije, zbog trenja nastaje toplina koja tali i omeksava strukturu drva, a hlađenjem tako nastale taline dobiva se cvrsti spoj. U radu su prikazane dosadasnje svjetske spoznaje, ali i rezultati vlastitih istraživanja utjecaja trajanja procesa zavarivanja na izvlacnu silu između bukova moždanika i podloge. Najbolje rezultate izvlacne sile (4 994 N) imali su spojevi kod kojih je proces zavarivanja moždanika trajao od 0, 56 do 0, 9 s (po svakom okretaju moždanika pomak je bio 1, 41 do 0, 88 mm), a najmanja izvlacna silu (2 869 N) zabilježena je pri trajanju zavarivanja od 1, 81 od 2, 61 s. Prosjecna izvlacna sila spoja lijepljenih spiralno nažlijebljenih moždanika iznosila je 5 028 N.

Spajanje drva klinovima bez ikakva lijepljenja i zavarivanja bilo je korišteno stoljećima. Ako ti klinovi (u ovom istraživanju moždanici) rotiraju prilikom spajanja s podlogom (u kontroliranim uvjetima), uz određene parametre nastaje čvrsti spoj znatne čvrstoće. Zavarivanje drva je proces u kojemu se zbivaju kemijsko-fizikalne reakcije, zbog trenja nastaje toplina koja tali i omekšava strukturu drva, a hlađenjem tako nastale taline dobiva se čvrsti spoj. U radu su prikazane dosadašnje svjetske spoznaje, ali i rezultati vlastitih istraživanja utjecaja trajanja procesa zavarivanja na izvlačnu silu između bukova moždanika i podloge. Najbolje rezultate izvlačne sile (4 994 N) imali su spojevi kod kojih je proces zavarivanja moždanika trajao od 0,56 do 0,9 s (po svakom okretaju moždanika pomak je bio 1,41 do 0,88 mm), a najmanja izvlačna silu (2 869 N) zabilježena je pri trajanju zavarivanja od 1,81 od 2,61 s. Prosječna izvlačna sila spoja lijepljenih spiralno nažlijebljenih moždanika iznosila je 5 028 N., Bonding of wood by virtue of wedge, without any adhesives and welding, has been done for centuries. If such wedge (in this research wood dowels) are rotated during the bonding with the surface (in controlled conditions) at certain parameters, a firm joint is formed. Welding of wood is a process where chemical and physical reactions take place, heat is formed during the friction that melts and softens the structure of wood, and a firm joint is formed by cooling of the melt. The paper shows world findings so far, as well as the results of our own research of the influence of welding process on the dowel embedded force between the beech wood dowel and the beech surface. The joints with the best results concerning the dowel embedded force (4994 N) were the joints where the process of impressing wood dowels lasted from 0.56 to 0.9 s (with each turn of the wood dowel, the movement was 1.41 to 0.88 mm) and the lowest dowel embedded force (2869 N) was recorded when the duration of the impressing lasted from 1.81 to 2.61 s. The average embedded force of glued spirally grooved dowels amounts to 5028 N.

Background and purpose: Primary schoolchildren spend most of their time in classrooms seated in chairs in some manner, but sitting behaviour and working postures of pupils are rarely observed as an important criterion in school furniture design. Yet, correctly designed children workspace in school is, among the others, one of the most important key factors in regular development of all abilities of youths. This research focused primarily on the pupils' behaviour at work, their movements and frequent activities during usage of tables and chairs in primary school classrooms, with the aim to identify main working postures and define them as notable criteria when designing school furniture for the future. Materials and methods: The research was conducted in one elementary school in Zagreb, Croatia, with 18 pupils from 2 to 8 grades. The method employed was video recording. Results: Forty three characteristic postures and semi-postures, classified in four main groups were recorded. The results showed that there are major differences in the subjects’ behaviour and in the habits of using the task chair and table with respect to age, gender, daytime, studied subjects, tasks and the teachers’ behaviour. Conclusions: Design of the school task furniture must take into account the age and anthropometrics of the child as well as analysis of characteristic postures of the pupils as one of the crucial design criteria and to be observed both in 3D and 2D system. New school furniture design has to encourage sitting dynamics and fits psychological, ergonomic, physical, social and cognitive aspects of their users.

Konstrukcije sjedala i naslona uredske stolice kao predmeta čovjekove radne okoline važni su u njezinom konačnom rješenju jer su to elementi koji su izravno i usko povezani s ljudskim tijelom. Sjedeći je položaj najčešći radni položaj modernog čovjeka u industrijski razvijenom svijetu. Neovisno o vrsti posla, pravilan i fiziološki ispravan sjedeći položaj smanjuje zamor pri radu i opterećenje kralješnice, a odgovarajući povoljan položaj pri sjedenju uvelike pridonosi povećanju koncentracije i radnog učinka. Sjedeći radni položaj moguće je razmatrati usklađivanjem antropometrijskih veličina s oblikom sjedala i naslona ili, mehaničkim pristupom, utvrđivanjem odnosa između korisnika i kvalitete sjedala, pri čemu velik utjecaj ima indeks udobnosti. Indeks udobnosti stolice kao jedan od pokazatelja udobnosti sjedenja proizlazi iz mehaničkih svojstava promatrane stolice. U radu su prikazani rezultati tzv. mehaničke udobnosti koju stolica može pružiti korisniku. Rezultati određivanja udobnosti sjedenja na uredskim radnim stolicama prikazani su indeksima udobnosti stolica dobivenih iz elastičnih svojstava materijala sjedala i stolice prema tehničkoj specifikaciji HRS ENV 14443., Construction of the seat and back of the office chair, as an actual object of the human working environment, is important in its final design since these are the elements that are in a direct and close contact with human body. The sitting position is the most frequent working position of the modern man in the developed world. Independently of the type of work, a sound and physiologically correct sitting position diminishes fatigue during work and strain of the spine, and suitable posture during sitting significantly contributes to the increase of concentration and efficiency. Sitting as a working position can be examined through coordination of anthropometric sizes and form of the seat and back, or mechanically, by determining the relation between the user and the seat quality, where the comfort index or support factor has a great infl uence. The comfort index as one of the factors of sitting comfort is the result of mechanical characteristics of the observed chair. This paper shows the results of ‘’mechanical comfort’’ that the chair can offer to the user. The results of determining the seat comfort on office chairs are featured through comfort index obtained from elastic characteristics of materials in the seat, but also of the chair itself according to Technical Specifications HRS ENV 14443.

Human health is becoming an increasingly important issue in contemporary hectic lifestyle imposed at work and by struggle to save time and money. Sitting comfort and quality of chairs which we use for the most of our time have, thus, become essential for healthy lifestyle. Sitting discomforts arise from prolonged sitting on the inappropriate chairs, which failing to provide sufficient support to the body cause discomfort and tiring. The studies of the office chair constructions have identified differences in perception of comfort provided by different types of seats. Four seat constructions and the comfort they provide to the sitters were compared by means of subjective indicators. After a two-day sitting on each of the studied chairs the subjects scored their perception of comfort and discomfort, using the questionnaire with 17 statements. Constructional forms and materials which contributed more to the sense of comfort by minimizing fatigue and pains developed by sitting were determined.

The present study aimed at determining the relationship of anthropometric dimensions of pupils from grades 1 to 8 in primary school with the dimensions of school chairs. Two dimensions of the chairs in daily use were evaluated to ascertain whether the fit is sufficient and the effect on pupils' sitting posture. The work included a sample of 556 pupils from three primary schools in Zagreb, Croatia and two types of furniture. Dimensions of school chairs were compared with three anthropometric variables of the pupils. Descriptive statistics were analysed for all variables. These study results have shown that furniture of appropriate dimensions is not available to a large number of students in Croatia. Currently supplied classroom equipment is provided in only two sizes and does not fit the users. It is recommended that task chairs may be acceptable if they are issued in four heights or individually adjustable chairs be introduced in Croatian schools. Furthermore it is strongly recommended that schools actively promote appropriate active sitting behaviour.

U radu su prikazane dosadašnje svjetske spoznaje o novijoj metodi spajanja drva, a rezultati eksperimentalnog zavarivanja drva dobiveni su na Šumarskom fakultetu Sveučilišta u Zagrebu. Tehnika zavarivanja drva razvijena je kao nov način spajanja drvenih dijelova uz pomoć topline koja se razvija zbog trenja i tlaka. Drveni se elementi spajaju bez upotrebe ljepila. Tijekom procesa zavarivanja rastale se površinski slojevi drva (lignin) u međusobnom kontaktu, a to se događa zbog utjecaja tlaka i topline, koja se najčešće postiže trenjem elemenata koje zavarujemo. U međupovršinskoj zoni stanična je struktura drva u potpunosti uništena, a u zoni zavarivanja znatno je povećana gustoća drva jer su drvne stanice sasvim uništene. Stijenke stanica popucaju zbog utjecaja topline, tlačne sile i kemijske reakcije tijekom hlađenja drva. Zahvaljujući upotrebi isključivo prirodnih materijala, tako spojeni proizvodi ekološki su prihvatljivi. Pri recikliranju ili spaljivanju zavareni proizvodi, kao ni prirodno drvo, ne oslobađaju toksične tvari., This paper presents the up-to-date knowledge and results of the application of wood welding techniques at the Faculty of Forestry University of Zagreb. Wood welding technologies have been developed as a new way of bonding timber by using high temperature generated by friction and pressure. Timber is assembled without any adhesives. During the process the surface layer of timber (lignin), which is in direct contact with its counterpart, melts due to high pressure and temperature, which is usually generated by mechanical friction of the elements being connected. The cell structure in the interface area of timber is completely destroyed, while in the welding area the density is increased due to the destruction of wood cells. The cell walls are broken, as a result of exposure to high temperatures, mechanical pressure and chemical process, which occur during the cooling stage. Only natural materials are used in wood welding, which makes these products eco-friendly. In case of recycling, welded products may be disposed of just as natural timber, without the release of toxic substances.

Današnji ritam života, tehnološka dostignuća, inovacije i zagađenje okoliša odražavaju se na ponašanje, navike i osjećaje suvremenog čovjeka, kao i njegovo psihofizičko stanje. Zdravlje čovjeka je sve ugroženije, a želja za poboljšanjem načina života i oblikovanja ljudskog okruženja postaje jedna od glavnih zadaća ljudskog opstanka. Jedan od načina kako preventivno djelovati na čovjekovo zdravlje ogleda se kroz namještaj te osviješten pristup njegovom oblikovanju, konstruiranju, proizvodnji i krajnjoj uporabi. U tom pristupu najvažniju ulogu imaju ergonomski i ekološki parametri. U radu je dan osvrt na ove dvije važne razine u sustavnom pristupu nastajanja namještaja koji potiče i održava zdravlje. Budući da se svakodnevna aktivnost čovječanstva pretežito svodi na sjedenje i ležanje, u odnosu na anatomsko-ergonomski parametar razmatra se namještaj za sjedenje pri radu i spavanje, dok je u odnosu na ekološki parametar dan osvrt na svojstva drva, kao jedne od značajnijih prirodnih i biološki čistih sirovina za proizvodnju namještaja, ali i opasnosti koje se nalaze u tom materijalu za zdravlje čovjeka ako se ne provodi određena kontrola u preradi, proizvodnji i uporabi., The modern-day dynamics of life, technological achievements, innovations and environmental pollution have an impact on the behaviour, habits and emotions of the modern man and on his psychophysical state. Human health is being increasingly more compromised, and a desire for a better way of life and a better-designed human environment is becoming one of the chief considerations of human survival. One of the modes of preventing damage to human health is to improve furniture design, its construction, manufacture and end use. Ergonomic and environmental considerations are key issues in this effort. The paper outlines the importance of these two chief considerations in furniture manufacture aimed at stimulating and maintaining good health. Human activities today are restricted mainly to sitting and lying down. Furniture designed for sitting and sleeping is studied from the point of view of anatomic and ergonomic features, while environmental issues are addressed in the consideration of the materials used in furniture manufacture, mostly of wood as one of the more important natural and biologically pure raw materials, but a material not free of hazards to human health if the processing, manufacture and use are not suitably controlled