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Two sizes (2x4 and 2x10) and two grades (2250f-1.9E and No. 2 KDl5) of Southern Pine lumber having three different test span lengths of 30, 90 and 120 inches were tested in tension parallel-to-grain. Results obtained from the tests indicated that the tensile strengths of the 30-inch test specimens were significantly higher than the tensile strengths of the 90- and 120-inch test specimens. A tensile strength-length effect model was developed for generating tensile strength values of lumber taking the length effect into consideration. The model generates tensile strength values for lumber longer than 30 inches in multiples of 30 inches, ie. 60-, 90- 120-inch lengths. The two sizes and two grades of Southern Pine lumber formed the data base for developing the model. The tensile strength-length effect model utilized an MOE variability model which generated serially correlated MOE's along 30-inch segments for a piece of lumber using a second order Markov model. The segment MOE values were then used in a first-order Markov model to generate serially correlated tensile strength residuals for each 30-inch segment. The segment MOE values and the segment tensile strength residuals were then inputted into a weighted least squares regression to obtain the tensile strength parallel-to-grain for each 30-inch segment. The tensile strength of the generated piece of lumber was then determined using the weakest-link concept; the minimum segment tensile strength value was selected as the tensile strength of the generated piece of lumber. / Master of Science

Pressure tests on wood have been conducted to determine its properties. The resultswere not as expected, and it is therefore difficult to obtain the parameters of thewood. This project examines how a specific defect in the wood sample affects theresult.The pressure test is simulated with numerical modeling. In the numerical model thecube’s top side is non-parallel with the bottom side, it is in other words somewhattilted.The results from the model agreed with the findings from some pressure tests. Withthose we can easily calculate the wood's properties. For other pressure tests, otherfactors might need to be examined before we can draw any conclusions. / Tryckprover på trä har utförts för att ta reda dess egenskaper. Resultaten blev intevad som förväntades, och det blir därför svårt att få fram träets egenskaper. Dettaprojekt undersöker hur en viss defekt i träprovet påverkar resultatet.Tryckprovet simuleras med numerisk modellering. I modellen är kubens toppsida inteparallell med bottensidan, den är med andra ord något sned.Resultatet från modellen stämde med resultat från vissa tryckprover. Då kan man fåfram träets egenskaper. För andra tryckprover kan andra faktorer behöva undersökasinnan man kan dra några slutsatser.

Research has established that correlations exist between bending and tension, and bending and compression strength of lumber. Because of this correlation, improvement in bending strength may be realized from proofloading in tension or compression. The data utilized in a reliability analysis was from Galligan et al. (1986) that characterized the properties of 2-inch softwood dimension lumber with regressions and probability distributions. Randomly selected groups of 2 by 4 1650f-1.5E Hem-fir and No.2 KD Southern Pine were evaluated for bending strength. One group from each species was selected as a control and tested in bending. The other groups were proofloaded in tension and compression at two stress levels and the survivors were tested in bending to failure. Based on the concept of equal reliability and utilizing the load distributions from Thurmond (1986), the tensile and compressive proofloaded strength distributions were compared to the control. The probability of failure for the control group is found, then with an iterative approach, the bending strength values of the proofloaded sample distribution are artificially altered by a factor K until the probabilities of failure for the proofloaded and control groups are similar. The K is a shift factor relating the amount the proofloaded strength distribution must be shifted on the x-axis to give the same reliability as the control. Simple 5th percentile comparisons, the advanced first order second moment (AFOSM) and numerical integration analysis methods were used to evaluate increases in allowable bending strength from proofloading in tension and compression. Proofloading in tension or in compression both produced significant increases in allowable bending strength for the Hem-fir grade. Proofloading in tension to a target 15 percent breakage level, or 2,838. psi, yielded for the survivors an increase of 72 percent in allowable bending strength. The allowable bending strength increased 60 percent due to a compressive proofloading to a target 15 percent breakage level. The allowable bending strength increased as the proofloading level increased for both tension and compression proofloading with the Hem-fir grade. The southern pine visual stress grade did not show a consistent trend between proofloading level and improvement in allowable bending strength. The lack of a trend between proofloading level and allowable bending strength was attributed to possible sampling error. The fifth percentile analysis method, the AFOSM method and numerical integration method were compared. For lumber strength comparisons, a simple fifth percentile analysis was not the preferred method. The AFOSM method and the numerical integration method provided identical results in terms of their application in adjusting allowable bending stresses. It was not possible to show that the approximate AFOSM method can be used exclusively in lieu of the numerical integration method for reliability calculations. / Master of Science

In an attempt to relate different pressing parameters to changes in test flake properties, eight hot-press cycles were used in the manufacture of 24 flakeboard panels, with 2 levels each of platen temperature, initial mat moisture content, and press closing time. Temperature and gas pressure occurring at the face and core of the mat, along with platen pressure, were recorded throughout the press cycles. Data is presented graphically as a function of press time. Face and core equilibrium moisture content conditions throughout the press cycle were estimated for each panel based on corresponding temperature and gas pressure information. Time-integral data on temperature, gas pressure, and platen pressure were determined. Simple linear regressions were performed in an attempt to relate the actual test flake environment to changes in properties. Two hundred and fifty yellow-poplar (<u>Liriodendron tulipifera</u>) test flakes were consolidated within the face and core of flakeboard mats and recovered. Their individual pre- and post-pressing thickness and specific dynamic bending modulus values were determined and compared with respect to changes in pressing parameters. Platen temperature, initial mat moisture content, and test flake location within the mat were all involved in significant two-way interactions in their effects on flake properties. / M.S.

Rational design of wood pallets requires estimates of average flexural properties of pallet lumber of many species and visual grades. The objective of this study was to develop procedures for estimating these design values for use in a first-order second-moment design format. Preliminary studies were performed to assess the effects of increased loading rates on in-grade flexural data, size effects between deckboard and stringer properties, and the effectiveness of the ASTM strength ratio concept as applied to pallet shook. An increased load rate (ten times the ASTM rate) resulted in an 8.0% increase in average MOR and a 4.7% increase in average MOE. No definite conclusions could be reached concerning the relative strength of deckboards vs. stringers. Several factors, other than a statistical size effect, may influence their relative strength. Estimated strength ratios (ESR) generally underpredicted the experimentally determined actual strength ratios (ASR). As knot size increased, the ESR increasingly underpredicted the ASR. Two approaches were used to values. The best is full-size commercial material. However, derive pallet shook design in-grade testing of only yellow-poplar and eastern oak species have currently been evaluated in this manner. For all other species, a modified procedure based largely on the methods of ASTM D 2555 and D 245 was recommended. This procedure yields conservative estimates of strength for grades allowing large knots. / M.S.

Thesis (PhD(For))--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Pinus patula is the most intensively planted conifer in the tropics and sub‐tropics. In South Africa Pinus patula plantations are the main saw‐log resource for structural lumber production. Improved intensive silvicultural practices and tree breeding have resulted in marked increases in the rate of growth. To reap the financial benefits of the faster growth, plantation managers are more and more inclined to reduce rotation ages, which inevitably results in the production of higher proportions of juvenile wood at final harvest, and lumber which often does not meet the minimum requirements for stiffness for structural lumber. Knowledge of the variation and the accurate prediction of the mechanical properties of the timber of standing trees can have various benefits for growers and processors of trees. It can be used for tree allocation to different processing facilities, for processing production planning, and to assist tree breeders to screen and select for superior breeding material. The objectives of this study were (1), to examine the within‐ and between‐tree variation in wood properties of young South African grown Pinus patula trees known to have important impacts on the suitability of sawn lumber for structural purposes and (2), to develop empirical prediction models for the flexural lumber properties from standing Pinus patula, based on variables that could be assessed non‐destructively from standing trees. Sample material was obtained from 170 trees (16‐20 years old) established in 17 compartments along the Mpumalanga escarpment of South Africa. A large number of variables which could be obtained non‐destructively from the trees while they were still standing, were measured. The trees were subsequently felled and two logs, 2.1 m in length, were extracted from each tree at two height positions. The 340 logs were processed into 1402 pieces of lumber for further measurements and destructive testing. Results showed that the mean modulus of elasticity measured on edge (MOEedge) was far below the limits set for structural grade softwood timber in South Africa. All the desirable properties for structural lumber improved with distance from the pith with the exception of the 5th percentile value for modulus of rupture (MOR), which was higher at the pith than for the boards processed adjacent to the pith. Boards processed from the lower part of the stem were superior in most of the important properties compared to those higher up in the stem. Separate multiple regression models for predicting the average dynamic MOE (MOEdyn) of individual boards, trees and compartments were developed. The models managed to explain 68%, 60% and 95% of the variation in MOEdyn respectively. The models developed for MOR explained 40% and 42% of variability at board and tree level respectively. At compartment level, 80% of the variation in the 5th percentile MOR value could be explained by the model. Sensitivity analyses showed that site index at base age of 10 years, acoustic time‐of‐flight, wood density and ring width were the most influential variables in the MOE models. The models indicated that tree slenderness during early growth seems to play a major role in determining the dynamic MOE and MOR of lumber. This is in agreement with Euler’s buckling theory and the bending stress theory. Microfibril angle (MFA) and density were measured on radial strips taken from a sub‐sample of trees with the Silviscan 3 technology. The mean microfibril angle per year ring in Pinus patula varied between 7o and 29o. In general MFA decreased with distance from the pith and height above ground level. A multiple regression model including microfibril angle, density and ring width explained 71% of the variation in the dynamic MOE of boards. Sensitivity analysis on the model showed that microfibril angle and density had roughly equal influences on predicting the MOEdyn of Pinus patula boards. / AFRIKAANSE OPSOMMING: Pinus patula is die mees aangeplante naaldhoutspesie in die tropiese en sub‐tropiese areas van die wêreld. Dit is die grootste bron van saagblokke vir die produksie van strukturele hout in SA. Intensiewe boskultuurpraktyke en boomteling het gelei tot ‘n merkbare verhoging in die groeitempo van die spesie. Plantasiebestuurders is gevolglik geneig om rotasie‐ouderdomme te verlaag, wat lei tot ‘n groter persentasie jeughout wat nie aan die minimum styfheidvereistes van strukturele hout voldoen nie. Kennis van die variasie en die akkurate voorspelling van die meganiese eienskappe van staande bome kan voordele inhou vir beide die verbouers en verwerkers van bome. Dit kan byvoorbeeld van hulp wees met die toewysing van bome aan verwerkingsfasiliteite, vir produksiebeplanning, en vir ondersteuning met die keuse van teelmateriaal vir boomtelers. Die doelwitte van hierdie studie was (1), om die binne– en tussenboomvariasie in die houteienskappe, wat ‘n bepalende invloed het op die geskiktheid van jong Suid Afrikaanse Pinus patula bome vir strukturele hout produksie, te ondersoek en (2), om empiriese modelle vir die voorspelling van die buigeienskappe van planke te ontwikkel, gebaseer op veranderlikes wat niedestruktief op staande Pinus patula bome ge‐evalueer is. Monsters vir die studie is verkry vanaf 170 bome (16‐20 jaar oud), geplant in 17 vakke op die Mpumalanga platorand van Suid Afrika. ‘n Groot aantal veranderlikes is nie‐destruktief gemeet op die staande bome waarna die bome gevel is en twee saagblokke, 2.1m in lengte, is op twee hoogte posisies uit elke boom verwyder. Die 340 blokke is verwerk tot 1402 planke vir verdere metings en destruktiewe toetse. Resultate het getoon dat die gemiddelde modulus van elastisiteit gemeet op die dwarskant (MOEedge) aansienlik laer was as wat vereis word vir strukturelegraad hout in Suid Afrika. Al die gewenste eienskappe het toegeneem met afstand vanaf die murg behalwe die 5de persentiel breekmodulus (MOR), wat hoër was vir murgplanke as vir aangrensende planke. Planke afkomstig van die laer dele van die stam het oor die algemeen beter eienskappe gehad as planke afkomstig van die hoër dele. Veelvuldige regressiemodelle kon 68%, 60% en 95% van die variasie in die gemiddelde dinamiese MOE (MOEdyn) op die vlak van onderskeidelik individuele planke, bome en vakke verklaar. Die modelle vir MOR kon 40% en 42% van die variasie op onderskeidelik plank‐ en boomvlak verklaar. Die model vir 5de persentiel MOR van vakke kon 80% van die variasie verklaar. ‘n Sensitiwiteitsanalise het aangetoon dat groeiplekindeks op ouderdom 10, akoestiese vlugtyd, digtheid en jaarringwydte die belangrikste veranderlikes was wat MOEdyn beïnvloed het. Die modelle het aangetoon dat die slankheid van bome tydens vroeë groei vermoedelik ‘n belangrike invloed op die MOEdyn en MOR van planke het. Dit is in ooreenstemming met Euler se knikteorie en die buigsterkteteorie. Die mikrofibrilhoek en digtheid van ‘n steekproef van die bome is gemeet met die Silviscan 3 apparaat. Die gemiddelde mikrofibrilhoek per jaarring het tussen 7 o en 29o varieer. Hierdie variasie was hoofsaaklik afhanklik van boomhoogte en aantal jaarringe vanaf die murg. ‘n Veelvuldige regressiemodel wat mikrofibrilhoek, digtheid en jaarringwydte insluit, kon 71% van die variasie in MOEdyn verklaar. ‘n Sensitiwiteitsanalise op die model het aangetoon dat mikrofibrilhoek en digtheid ongeveer ewe belangrik was wat betref hulle invloed op die voorspelde MOEdyn van Pinus patula planke.

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Orientador: Elias Taylor Durgante Severo / Banca: Claudio Angeli Sansigolo / Banca: Vladimir Eliodoro Costa / Banca: Ricadro Marques Barreiros / Banca: Fabio Minoru Yamaji / Resumo: No Brasil, a espécie pioneira Schizolobium parahyba (Vell.) Blake, conhecida como Guapuruvu, tem potencial para os projetos de restauração ecológica da Floresta Atlântica, e quando atingem cerca de 15 anos podem ser retiradas mediante plano de manejo. Entretanto, uma característica indesejável da sua madeira é a presença acentuada de lenho juvenil e uma das suas limitações é a baixa durabilidade natural. Uma forma de minimizar este problema é a modificação térmica logo após a sua secagem. Porém, esses tratamentos provocam mudanças na cor da madeira. Assim, o objetivo desse estudo foi avaliar o efeito do tratamento de modificação térmica nas propriedades físicas, químicas e colorimétricas e na resistência dos lenhos juvenil e adulto de S. parahyba aos organismos xilófagos e ao intemperismo. Para tanto, foram usadas tábuas provenientes de toras de Guapuruvu, com cerca de 15 anos de idade, retiradas de uma área de recuperação florestal da Faculdade de Ciências Agronômicas, da UNESP, de Botucatu-SP. Cada tábua foi seccionada de modo a fornecer peças controle e outras destinadas para os tratamentos de modificação térmica, com temperaturas finais de 180ºC, 200ºC e 220ºC. Corpos de prova foram retirados para a caracterização tecnológica dos lenhos juvenil e adulto através dos ensaios de propriedades físicas, químicas, de caracterização colorimétrica da madeira e de resistências aos fungos de podridão parda Gloeophyllum trabeum e de podridão branca Pycnoporus sanguineus, ao cupim de ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: n Brazil, the pioneer plant species Schizolobium parahyba (Vell.) Blake, known as Guapuruvu, has potential for ecological restoration projects in the Atlantic Forest, and when they reach about 15 years can be taken by the management plan. However, an undesirable feature of this wood is the pronunced presence of juvenile wood and a limitation is low biological resistance. An attractive way to mitigate this problem is this thermal modification process after its drying. However, these thermal treatments cause changes in color of wood. The aim of this study was to evaluate the effect of thermal modification on physicochemical and colorimetric properties and biological resistance of juvenile and mature woods from S. parahyba to xylophagous organisms and weathering. Boards were taken from a 15-year-old S. parahyba forest recovery area of Agronomy Sciences College from UNESP, located in Botucatu, SP, Brazil. Each board was sawed into smaller pieces measuring 0.60 m in length. One small piece was kept in its original condition (untreated wood), whereas the other pieces were reserved for the thermal treatments at final temperature of 180ºC, 200ºC, and 220ºC. Subsequently, samples were cut from all the boards (untreated and thermally modified woods) to technological characterization for both juvenile and mature wood across to tests of physical and chemical properties, colorimetric characterization of wood, decay resistance at brown-rot fungus Gloeophyllum trabeum and white-rot fungus Pycnoporus sanguineus, biological resistance to térmite dry wood Cryptotermes brevis, and weathering resistance. The results showed that: (1) the increase in the thermal modification temperature causes significant decreases of up to 9,1% in the density at 21ºC and 65% relative humidity of the S. parahyba wood and reduces the equilibrium moisture content and volumetric swellings in up to 51.1% and 54.1%, respectively; ... / Doutor

Orientador: Nilson Tadeu Mascia / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-12T16:59:12Z (GMT). No. of bitstreams: 1 Todeschini_Rodrigo_M.pdf: 5391907 bytes, checksum: 209282e318155e52af17d68ae99c2ffb (MD5) Previous issue date: 2009 / Resumo: A realização de ensaios uniaxiais e biaxiais permite uma melhor compreensão do comportamento mecânico de um material que possui direções principais de resistência e é sem dúvida uma forma que pesquisadores encontraram para obter resultados condizentes com a situação real que uma determinada estrutura apresenta. O presente trabalho teve como objetivo o estudo do critério de resistência proposto por Tsai e Wu, realizando-se ensaios uniaxiais e biaxiais. A avaliação do critério ficou restrita ao ensaio de compressão, devido às dificuldades de se realizar ensaios biaxiais de tração. Com o ensaio biaxial de compressão, tensões em duas direções principais foram simultaneamente desenvolvidas, utilizando-se um equipamento de ensaio tradicional para uma direção e na direção perpendicular um equipamento tipo alicate desenvolvido para este fim. O parâmetro estudado foi o 12 F , parâmetro este que designa a possibilidade da superfície de ruptura ser aberta ou fechada, considerando-se que para a segurança de um projeto é imprescindível obter uma superfície fechada para o critério de resistência adotado. Observa-se, além disso, que o parâmetro 12 F foi obtido no ensaio biaxial de compressão de forma direta. Para as espécies de madeira Pinus elliottii e Goupia glabra (Cupiúba), obtiveram-se valores experimentais satisfatórios, sendo algumas inconsistências observadas em função da heterogeneidade do material. / Abstract: The completion of the uniaxial and biaxial tests permits a better understanding of the mechanical behavior of a material that has main failure directions and it is undoubtedly a method that researchers identified to achieve consistent results with the actual situation that a particular structure presents. This study aimed at studying the strength criterion proposed by Tsai and Wu, performing uniaxial and biaxial tests. The evaluation of this criterion was restricted to compression biaxial tests due to the difficulties presented by tension biaxial tests. With a compression biaxial test, the stresses in two main directions were simultaneously carried out, using a standard equipment test for one direction and for the perpendicular direction an equipment type pliers especially developed for this purpose. The failure parameter studied was 12 F , which evaluates the possibility of failure surface to be opened or closed, also considering that for the safety of design it is essential to obtain a closed surface for the failure criterion adopted. Furthermore, it was noted that in the compression biaxial test the parameter 12 F was obtained directly. For the species of wood Pinus elliottii and Goupia glabra (Cupiúba), the experimental values obtained were satisfactory with some inconsistencies observed in the light of the heterogeneity of the material. / Mestrado / Estruturas / Mestre em Engenharia Civil