Toxicidade de produtos sintetizados a partir de extratos de plantas e do bistrifluron para o cupim subterrâneo Coptotermes gestroi (Wasmann, 1896) (Isoptera; Rhinotermitidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Caracterização físico-mecânica de elementos estruturais roliços perfilados de Amaru

The study of physical and mechanical properties of wood is essential for its structural use and it is of great importance to the construction industry. Thus, this study aimed to determine the physical and mechanical properties of the wood Amaru - a hybrid of Eucalyptus, developed by Plantar Projects and Forest Products Ltda. In order to determine the properties of Amaru, round samples were used, which were provided to the Laboratory of Wood and Wooden Structures of the School of Engineering of São Carlos, University of São Paulo - LaMEM / EESC / USP. For the characterization of the physical properties, the apparent specific gravity and moisture content of the samples were determined. To the mechanical characterization, the following properties were evaluated: strength and stiffness in compression, strength and stiffness in bending, shear and tension. The procedures of the tests performed in this study were done according to the recommendations of the Brazilian Wood Standard ABNT NBR 7190:1997. The specimen used were confectioned in actual dimensions, according to as those used in the construction system proposed by Plantar. The results obtained from the tests performed showed that the mechanical properties approached the values proposed by the Wood Standard NBR 7190. The visual grading was important to provide a primary idea about the failure modes to be obtained from the tests performed. The bending test showed the modulus of elasticity (MOE) and Modulus of Rupture (MOR), which resulted in 15822 MPa and 101,7 MPa, respectively. The compression test resulted in values Ec0,m and fc0, 15698 MPa and 50,7 MPa. The tensile strength (ft0) of this hybrid was calculated and its value obtained was 60,8 MPa. The shear strength (fv0) was 8,2 MPa. The results obtained from the tests are the basis for engineers and architects to design structures using wood species Amaru

Pile-dwellings of the Neolithic and the Bronze Age in Switzerland. Long-term research and future tasks

Swiss lake-side settlements dating between 4300 and 800 BC were first recognized in the early 19th century and between 1854 and 1880 early research boomed due to the first scientific studies and the artificial lowering of lakes in Western Switzerland. In the 20th century underwater and wetland archaeology experienced an enormous surge not only because of large rescue excavations, due to extensive motorway construction projects but also due to the evolution of modern IT technology in the 1970s. For the first time huge quantities of ancient wooden structures could be dated by dendrochronology. This produced a quantum leap in the 150 years of pile-dwelling research. In 2011, the UNESCO World Heritage Committee recognized the outstanding universal value of these sites. This article presents an overview about Swiss pile-dwellings of the Neolithic and the Bronze Age and the results of two recent diploma works (case study Sutz-Lattrigen Haupstation innen and case study Seedorf Lobsigensee) as examples of research and cooperation between universities and government agencies for cultural heritage management.

Análisis de elementos de madera reforzados con materiales compuestos

Gran parte del patrimonio construido cuenta con edificios cuya estructura está compuesta por elementos de madera. El volumen económico que supone el mantenimiento y renovación de dicho patrimonio es considerable, por ello, es de especial interés el estudio de las diferentes técnicas de refuerzo aplicables a este tipo de estructuras. Las estructuras de madera han sido tradicionalmente reforzadas con piezas del mismo material, aumentando la sección de los elementos dañados, o con acero. La aparición de los materiales compuestos de polímeros reforzados con fibras, y su progresiva aplicación en obras de construcción, hizo que a principios de la década de los noventa se comenzara a aplicar este material en refuerzos de estructuras de madera (Puente de Sins, 1992). La madera es un material natural con una excelente relación entre sus características mecánicas y su peso. Con el uso de materiales compuestos como refuerzo ésta característica se mantiene. En cuanto a su modelo constitutivo, se admite un comportamiento elástico lineal a tracción paralela a la fibra hasta la rotura, mientras que a compresión, se considera un comportamiento lineal elástico inicial, seguido de un tramo plástico. En vigas de madera aserrada sometidas a flexión predomina el modo de fallo por tracción localizándose la fractura frecuentemente en el canto inferior. Los FRP tienen un comportamiento elástico lineal a tracción hasta la rotura y cuentan con excelentes propiedades mecánicas en relación a su peso y volumen. Si se refuerza la viga por el canto inferior se aumentará su capacidad de absorber tracciones y por tanto, es previsible que se produzca un incremento en la capacidad de carga, así como un aumento de ductilidad. En este trabajo se analizan los beneficios que aportan distintos sistemas de refuerzos de materiales compuestos. El objetivo es contribuir al conocimiento de esta técnica para la recuperación o aumento de las propiedades resistentes de elementos de madera sometidos a flexión. Se ha llevado a cabo un estudio basado en datos obtenidos experimentalmente mediante el ensayo a flexión de vigas de madera de pino silvestre reforzadas con materiales compuestos. Las fibras que componen los tejidos utilizados para la ejecución de los refuerzos son de basalto y de carbono. En el caso de los compuestos de fibra de basalto se aplican en distintos gramajes, y los de carbono en tejido unidireccional y bidireccional. Se analiza el comportamiento de las vigas según las variables de refuerzo aplicadas y se comparan con los resultados de vigas ensayadas sin reforzar. Además se comprueba el ajuste del modelo de cálculo no lineal aplicado para predecir la carga de rotura de cada viga reforzada. Con este trabajo queda demostrado el buen funcionamiento del FRP de fibra de basalto aplicado en el refuerzo de vigas de madera y de los tejidos de carbono bidireccionales con respecto a los unidireccionales. ABSTRACT Many of the buildings of the built heritage include a structure composed by timber elements. The economic volume involved in the maintenance and renewal of this built heritage is considerable, therefore, the study of the different reinforcement techniques applicable to this type of structure is of special interest. The wooden structures have traditionally been reinforced either with steel or with pieces of the same material, increasing the section of the damaged parts. The emergence of polymer composites reinforced with fibers, and their progressive use in construction, started to be applied as reinforcement in timber structures at the beginning of the nineties decade in the 20th century (Sins Bridge, 1992). Wood is a natural material with an excellent ratio between its mechanic characteristics and its weight. This feature is maintained with the use of composites as reinforcement. In terms of its constitutive model, linear elastic behavior parallel to the fiber up to fracture is admitted when subjected to tensile stress, while under compression, an initial linear elastic behavior, followed by a section plasticizing, is considered. In sawn timber beams subjected to bending, the predominant failure is mainly due to tensile stress; and frequently the fracture is located at the beam lower face. The FRP have a linear elastic behavior until fracture occurs, and have excellent mechanical properties in relation to their weight and volume. If the beam is reinforced by its lower face, its capacity to absorb tensile stresses will increase, and therefore, an increase in its carrying capacity is likely to be produced, as well as an increase in ductility. This work analyzes the benefits different reinforcement systems of composite materials provide, with the aim of contributing to the knowledge of this technique for recovering or increasing the strength properties of timber elements subjected to bending loads. It is a study based on data obtained experimentally using bending tests of pine timber beams reinforced with composite materials. Fibers used for the execution of the reinforcement are basalt and carbon. Basalt fiber composites are applied in different grammages, whereas with carbon composites, unidirectional and bidirectional fabrics are used. The behavior of the beams was analyzed regarding the reinforcement variables applied, and the results are compared with those of the tested beams without reinforcement. Furthermore it has been proved adjunting the nonlinear calculation model applied to predict the failure load of each reinforced beam. This work proves the good behavior of fiber reinforce plastic (FRP) with basalt fiber when applied to timber beams, and that of bidirectional carbon fabrics as opposed to the unidirectional ones.

Rapid polyether cleavage via extracellular one-electron oxidation by a brown-rot basidiomycete

Fungi that cause brown rot of wood are essential biomass recyclers and also the principal agents of decay in wooden structures, but the extracellular mechanisms by which they degrade lignocellulose remain unknown. To test the hypothesis that brown-rot fungi use extracellular free radical oxidants as biodegradative tools, Gloeophyllum trabeum was examined for its ability to depolymerize an environmentally recalcitrant polyether, poly(ethylene oxide) (PEO), that cannot penetrate cell membranes. Analyses of degraded PEOs by gel permeation chromatography showed that the fungus cleaved PEO rapidly by an endo route. 13C NMR analyses of unlabeled and perdeuterated PEOs recovered from G. trabeum cultures showed that a major route for depolymerization was oxidative C—C bond cleavage, a reaction diagnostic for hydrogen abstraction from a PEO methylene group by a radical oxidant. Fenton reagent (Fe(II)/H2O2) oxidized PEO by the same route in vitro and therefore might account for PEO biodegradation if it is produced by the fungus, but the data do not rule out involvement of less reactive radicals. The reactivity and extrahyphal location of this PEO-degrading system suggest that its natural function is to participate in the brown rot of wood and that it may enable brown-rot fungi to degrade recalcitrant organopollutants.

Fire behaviour of tabique walls

This paper present a study on the behaviour of tabique walls, concerning its fire resistance. This work is based on the experimental analysis of real scale tabique panels. Such walls were made in pine wood with an earth-based mortar finishing. In order to assess the earth-based mortar thickness effect on the fire resistance of the wall, three specimens were tested with three different mortar thicknesses of 15 mm, 10 mm and 5 mm. The earth-based mortar was previously analysed in the laboratory. The wooden structures were constructed based on traditional tabique technique. The experimental models were tested in a fire-resistance furnace, according to the ISO 834 standard fire. Temperatures were recorded using two data acquisition systems (spot measuring and field measuring). Fire resistance of test elements is expressed as the time during which the appropriate criteria have been satisfied so that one can predict the time before collapse, increasing both people and property safety. The obtained results are of great importance as they allow to improve the knowledge on tabique walls behaviour subjected to fire conditions. Two performance criteria were verified: the integrity criteria and the insulation criteria.

A Review of the Environmental and Health Effects of Termiticides under Australian Conditions

There exists a major cost issue as regards termite damage to wooden structures. A factor in this cost has been the increasing trend towards slab-on-ground construction. Current literature has been reviewed in relation to concerns about the possible public/environmental health consequences of the repeated use of termiticides in large quantities. The previous, current and projected future use patterns of termiticides are reviewed in the context of techniques appropriate for termite control and treatment priorities. The phasing out of organochlorine termiticides in Australia was undertaken to minimise impact of these substances on the environment and to a lesser extent on public health. These persistent chemicals were replaced by substances with high activity but relatively low persistence in the soil. There has also been an increase in the use of alternative methods (e.g. physical barriers) for the control of termites. The transition away from organochlorine termiticides has led to a realisation that significant information gaps exist with regard to replacement chemicals and other technologies. Although relatively persistent, the organochlorine chemicals have a limited lifespan in soils. Their concentrations are gradually attenuated by processes such as transport away from the point of application and biodegradation. Wooden structures originally treated with these substances will, with the passing of time, be at risk of termite infestation. The only available option is re-treatment with chemicals currently registered for termite control. Thus, there are likely to be substantial future increases associated with the cost of re-treatment and repairs of older slab-on-ground dwellings. More information is required on Australian termite biology, taxonomy and ecology. The risks of termite infestation need to be evaluated, both locally and nationally so that susceptible or high risk areas, structures and building types can be identified and preventive measures taken in terms of design and construction. Building regulations and designs need to be able to reduce or eliminate high-risk housing; and eliminate or reduce conditions that are attractive to termites and/or facilitate termite infestation.

Influence of stiffness in bolted connections in wooden plane structure of truss type

Trusses are structural systems commonly used in projects, being employed mainly in roof structures, present in most rural buildings. The design of trusses, as well as other structural systems, requires the determination of displacements, strains and stresses. However, the project is developed from an ideal model of calculation, considering free rotation between the elements of a connection. This paper presents a computer program for the analysis of bidimensional wooden trusses with connections formed with two screws per node. The formulation is based on the flexibility method, taking into account the influence of the effect of semi-rigid connections formed by two screws. An example of a structure is presented and analyzed by the program developed here, highlighting the importance of behavior analysis on semi-rigid connections.

Wooden cellular slabs with and without insulation submitted to fire conditions

The wooden cellular slabs are lightweight structures, easy to assemble, and with excellent architectural features, as thermal and acoustic conditions. The wooden cellular slabs with perforations are typical and very common engineering solutions, used in the ceiling or flooring plates to improve the acoustic absorption of compartments, and also have a good insulation and relevant architectonic characteristics. However, the high vulnerability of wooden elements submitted to fire conditions requires the evaluation of its structural behavior with accurately. The main objective of this work is to present a numerical model to assess the fire resistance of wooden cellular slabs with different perforations. Also the thermal behavior of the wooden slabs will be compared considering material insulation inside the cavities

Thermal model for charring rate calculation in wooden cellular slabs under fire

Wood is a natural and traditional building material, as popular today as ever, and presents advantages. Physically, wood is strong and stiff, but compared with other materiais like steel is light and flexible. Wood material can absorb sound very effectively and it is a relatively good heat insulator. But dry wood does bum quite easily md produces a great deal ofheat energy. The main disadvantage is the high levei ofcombustion when exposed to fíre, where the point at which it catches fire is fi-om 200-400°C. After fu-e exposure, is need to determine if the charred wooden stmctures are safe for future use. Design methods require the use ofcomputer modelling to predict the fíre exposure and the capacity ofstructures to resist fhose action. Also, large or small scale experimental tests are necessary to calibrate and verify the numerical models. The thermal model is essential for wood stmctures exposed to fire, because predicts the charring rate as a fünction offire exposure. The charring rate calculation ofmost stmctural wood elements allows simple calculations, but is more complicated for situations where the fire exposure is non-standard and in wood elements protected with other materiais.

National Conference on Wood Transportation Structures /

Cover title.

Different coordination modes for disulfoxides towards diorganotin(IV) dichlorides. X-ray crystal structures of 1,2-cis-bis-(phenylsulfinyl)ethene (rac-,cis-cbpse) and adducts [{Ph2SnCl2(meso-bpse)}n] and [{n-Bu2SnCl2(pdtd)}2]

The reactions of meso-1,2-bis(phenylsulfinyl)ethane (meso-bpse) with Ph2SnCl2, 2-phenyl-1,3-dithiane trans-1-trans-3-dioxide (pdtd) with n-Bu2SnCl2 and 1,2-cis-bis-(phenylsulfinyl)ethene (rac-,cis-cbpse) with Ph2SnCl2, in 1:1 molar ratio, yielded [{Ph2SnCl2(meso-bpse)}n], [{n-Bu2SnCl2(pdtd)}2] and [{Ph2SnCl2(rac,cis-cbpse)}x] (x = 2 or n), respectively. All adducts were studied by IR, Mössbauer and 119Sn NMR spectroscopic methods, elemental analysis and single crystal X-ray diffractometry. The X-ray crystal structure of [{Ph2SnCl2(meso-bpse)}n] revealed the occurrence of infinite chains in which the tin(IV) atoms appear in a distorted octahedral geometry with Cl atoms in cis and Ph groups in trans positions. The X-ray crystal structure of [{n-Bu2SnCl2(pdtd)}2] revealed discrete centrosymmetric dimeric species in which the tin(IV) atoms possess a distorted octahedral geometry with bridging disulfoxides in cis and n-butyl moieties in trans positions. The spectroscopic data indicated that the adduct containing the rac,cis-cbpse ligand can be dimeric or polymeric. The X-ray structural analysis of the free rac-,cis-cbpse sulfoxide revealed that the crystals belong to the C2/c space group.

Nanochromics: old materials, new structures and architectures for high performance devices

Due to the development of nanoscience, the interest in electrochromism has increased and new assemblies of electrochromic materials at nanoscale leading to higher efficiencies and chromatic contrasts, low switching times and the possibility of color tuning have been developed. These advantages are reached due to the extensive surface area found in nanomaterials and the large amount of organic electrochromic molecules that can be easily attached onto inorganic nanoparticles, as TiO2 or SiO2. Moreover, the direct contact between electrolyte and nanomaterials produces high ionic transfer rates, leading to fast charge compensation, which is essential for high performance electrochromic electrodes. Recently, the layer-by-layer technique was presented as an interesting way to produce different architectures by the combination of both electrochromic nanoparticles and polymers. The present paper shows some of the newest insights into nanochromic science.

Two dimensional analysis of inflatable structures by the positional FEM

This paper presents a, simple two dimensional frame formulation to deal with structures undergoing large motions due to dynamic actions including very thin inflatable structures, balloons. The proposed methodology is based on the minimum potential energy theorem written regarding nodal positions. Velocity, acceleration and strain are achieved directly from positions, not. displacements, characterizing the novelty of the proposed technique. A non-dimensional space is created and the deformation function (change of configuration) is written following two independent mappings from which the strain energy function is written. The classical New-mark equations are used to integrate time. Dumping and non-conservative forces are introduced into the mechanical system by a rheonomic energy function. The final formulation has the advantage of being simple and easy to teach, when compared to classical Counterparts. The behavior of a bench-mark problem (spin-up maneuver) is solved to prove the formulation regarding high circumferential speed applications. Other examples are dedicated to inflatable and very thin structures, in order to test the formulation for further analysis of three dimensional balloons.

Power Secant Method applied to natural frequency extraction of Timoshenko beam structures

This work deals with an improved plane frame formulation whose exact dynamic stiffness matrix (DSM) presents, uniquely, null determinant for the natural frequencies. In comparison with the classical DSM, the formulation herein presented has some major advantages: local mode shapes are preserved in the formulation so that, for any positive frequency, the DSM will never be ill-conditioned; in the absence of poles, it is possible to employ the secant method in order to have a more computationally efficient eigenvalue extraction procedure. Applying the procedure to the more general case of Timoshenko beams, we introduce a new technique, named ""power deflation"", that makes the secant method suitable for the transcendental nonlinear eigenvalue problems based on the improved DSM. In order to avoid overflow occurrences that can hinder the secant method iterations, limiting frequencies are formulated, with scaling also applied to the eigenvalue problem. Comparisons with results available in the literature demonstrate the strength of the proposed method. Computational efficiency is compared with solutions obtained both by FEM and by the Wittrick-Williams algorithm.