Marta Kałuża

In modern construction, natural materials with a low carbon footprint and full recyclability are becoming increasingly important. A typical group here is products made from solid wood, including glued wood, plywood, and wood-based composites. With their many advantages, however, they all burden the environment with the costs of production processes, as well as the need to use harmful chemicals (adhesives and impregnants). Solid wood is devoid of these disadvantages; however, it is often treated as a rather archaic material. One of the arguments here is its low durability compared to, e.g., glued wood. The article discusses the durability of solid wood using the example of a group of wooden churches preserved in Poland, in Upper Silesia. Some of these buildings are over five hundred years old, making them a reliable source of information about the durability of the material from which they were built. A total of 85 churches, at least 200 years old, were analyzed, evaluating the technical state of the main load-bearing elements of their structures. In view of the number of facilities and the inability to conduct tests in most of them, the assessment was limited to a visual inspection of the technical condition, carried out by an experienced building expert. The assessment estimated the area of corrosion damage, probed its depth, and measured the depth of cracks. The relationship between their technical condition and the environmental conditions in which they were used was described and discussed. In this way, both the threats to the durability of solid wood and the ways to keep it in good condition for hundreds of years were identified, refuting the thesis that solid wood is a material with low durability. Its use in structural elements therefore supports efficient resource management and contributes to sustainable construction, especially in small and medium-sized buildings.

The application of surface strengthening is an effective method to increase the shear capacity of masonry walls. The effectiveness of such systems is analyzed during ad hoc tests, which guarantees no effect of aging. However, under real conditions, the aging process plays an important role, as it affects the durability and effectiveness of the strengthening. This article presents preliminary results of aging tests performed on glass fiber meshes undertaken as part of the TC-290 IMC work of the RILEM organization. The aging process consisted of soaking the meshes in a 0.16% CaOH solution at either 23C or 40C, for periods of 1000, 2000 and 3000 hours. Tensile tests on the meshes were performed for 7 series, one of which was a reference, and the others included aged meshes. Analysis of the test results showed that the effect of the solution temperature was significant, as in the case of an increased temperature (40C), and therefore a more intensive aging process, significant reductions in strength and deformability were recorded, exceeding 30% of the value measured in the reference series. For a solution temperature of 23C, the reductions were just over 10%. An interesting observation was that with the passage of time, the intensity of the changes taking place decreased, and the reductions in the values of the analyzed parameters obtained after 3000 hours of soaking stabilized

The article presents a research and computational analysis of the effect of external strengthening on the shear capacity of walls made of autoclaved aerated concrete (AAC) blocks. Non-structural materials, i.e. glass mesh and plaster mortar, which are used in thermal modernization works, were used as strengthening. The first part discusses and shows the results of testing of individual materials and strengthening set in the form of single-lap and coupon type specimens, as well as standard model tests of 1.2 × 1.2 m walls. Two arrangements of meshes on the surface of the models (horizontally and vertically) were tested, showing that for the materials used, both configurations yield similar increases in shear capacity of 89% and 80%, respectively. On the basis of the parameters determined in the material tests, that is, the effective strains and the modulus of elasticity of the strengthening, the contribution of the strengthening to the load capacity of the strengthened walls was calculated, directly on the basis of literature guidelines, as well as taking into account the proposed modification. Comparison of the results derived from the calculations and model tests indicated very good agreement

Gazobeton i pianobeton to materiały należącedo rodziny betonów lekkich, które powstają poprzez modyfikacjęstruktury. Przy różnych technologiach tej modyfikacji efektemjest uzyskanie betonu o silnie porowatej strukturze. Stąd uogólnionanazwa obydwu materiałów – betony komórkowe. W artykuleomówiono podstawowe cechy betonów komórkowych, takiejak gęstość objętościowa, wytrzymałość na ściskanie i współczynnikprzewodzenia ciepła, istotne z punktu widzenia ich funkcji– izolacyjnej i konstrukcyjnej, a także powiązania tych cech. Gazobeton,dostępny przede wszystkim jako autoklawizowany betonkomórkowy, jest obecny na rynku w formie gotowych, znormalizowanychelementów. To powoduje, że jego parametry są ściśleokreślone w zależności od kategorii elementu, odnoszącej się do niskiej,średniej bądź wysokiej gęstości (od D300 do D800 kg/m3).Pianobeton nie jest produkowany i dostępny jako gotowy wyróbbudowalny o zadanych parametrach, a zatem jego właściwościmożna dość dowolnie kształtować. W zastosowaniachpraktycznych gęstość objętościowa pianobetonu wynosi od 400do 1600 kg/m3. Gazobetony charakteryzuje niska wytrzymałośćna ściskanie, wynosząca od 2 do 5 MPa, podczas gdy wytrzymałośćpianobetonów może dojść do 30 MPa – przy czym dla konkretnychgęstości wytrzymałość gazobetonu jest wyższa. Właściwościtermoizolacyjne obydwu tych materiałów są podobne,przy identycznej ich gęstości. Współczynnik przewodzenia ciepławynosi od 0,08 do 0,25 W/(mK), odpowiednio przy gęstościachod 300 do 800 kg/m3, natomiast przy najcięższych (konstrukcyjnych)pianobetonach wzrasta do około 0,7 W/(mK).Generalnie, niezależnie od sposobu wytworzenie i indywidualnychcech technicznych, obydwa te materiały znakomicie wpisująsię w ideę budownictwa energooszczędnego.

The article presents the influence of a superficial strengthening system on the behaviour of AAC-block walls with thin bed joints and unfilled head joints. The strengthening system consisted of a high-strength fibreglass mesh applied to both wall surfaces with a mineral mortar reinforced with fibreglass. A series of strengthened and unstrengthened specimens was tested under diagonal compression according to ASTM E519-15 to determine their shear strength and stress-strain characteristics. The use of optical strain measurement made it possible to identify the failure mode for both types of the tested walls. The strengthening system changed the wall failure development, which was initiated by unfilled head joints in both cases. The application of the strengthening system on both wall surfaces improved the strength properties of the wall significantly. The load-bearing capacity of the specimens increased by nearly 90% and cracking of the walls occurred at loads about 50% higher compared to specimens with no superficial strengthening. The strengthened specimens exhibited a ductile behaviour after reaching the maximum bearing capacity. A simplified method for computing the cracking load and maximum load was also proposed, the results of which are consistent with the tests results.

This paper presents the results of an experimental study of the shear behavior of masonry walls made of aero autoclaved concrete (AAC) blocks strengthened by externally bonded fiber-reinforced polymer (FRP) composites. Fifteen small wall specimens were constructed and tested in a diagonal compression scheme. Two types of composite materials—carbon- and glass-reinforced polymers—were arranged in two configurations of vertical strips, adopted to the location of the unfilled head joints. The effect of the strengthening location and strengthening materials on changes in the strength and deformability parameters are discussed and the failure process of unstrengthened walls is also presented. The placement of the composite on unfilled head joints proved to be a better solution. Carbon-fiber-reinforced polymer (CFRP) strips provided a threefold increase in stiffness, a 48% increase in load-bearing capacity and a high level of ductility in the post-cracking phase. Glass-fiber-reinforced polymer (GFRP) strips offered a 56% increase in load-bearing capacity but did not change the stiffness of the masonry and provided relatively little ductility. Placing the composite between unfilled joints was only reasonable for CFRP composites, providing a 35% increase in load-bearing capacity but with negligible ductility of the masonry.

The use of adhesive to joint structural elements, despite many advantages of this technology, is not a method commonly used in engineering practice, especially in construction. This is mainly due to the poor recognition of the behavior, both in terms of testing and analysis, of joints made on a scale similar to the actual elements of building structures. Therefore, this paper presents the results of model tests and then numerical analyses of adhesively bonded joints made of high-strength steel elements in a full-scale (double-lap joint). In order to properly model the adhesive connection, material tests of the methacrylate adhesive were performed in the field of tensile, shear (in two versions: single lap joint test and thick adherent shear test) and bond properties. Comparison of the results of the model and numerical tests showed very good agreement in terms of the measurable values, which makes it possible to consider the results obtained in the adhesive layer as reliable (not directly measurable in model tests). In particular, the distribution of stresses inside the adhesive layer, the range of plastic zones and areas of loss of adhesion are presented and discussed. The results indicate the possibility of a reliable representation of the behavior of adhesively bonded joints of high-strength steel, thus providing a tool for the analysis of semirigid adhesive in large-size joints.