scholarly journals The impact of the health condition of oaks from the Krotoszyn Plateau on the mechanical properties of timber structures

2015 ◽  
Vol 57 (4) ◽  
pp. 224-232
Author(s):  
Jarosław Siwiński ◽  
Katarzyna Kubiak ◽  
Miłosz Tkaczyk ◽  
Anna Mazur ◽  
Ryszard Rekucki

Abstract The study was conducted to perform a comparative analysis of the mechanical properties of wood samples derived from oaks in the Krotoszyn Plateau, which depend on the health state of the trees. Strength parameters of oak wood were calculated for selected diseased and healthy trees (according to the Roloff classification). The study was conducted by a modified method described in the standard Polish Norm PN EN 408+ A1: 2012. For testing, prior selection of wood samples showed that more wood samples of diseased trees compared with those of healthy oaks did not fulfil the Polish standard requirements. According to the method used, the average results of strength tests of timber structures from healthy oaks exhibited higher strength parameters than those of the diseased trees.

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 519
Author(s):  
Vitalii Bezgin ◽  
Agata Dudek ◽  
Adam Gnatowski

This paper proposes and presents the chemical modification of linear hydroxyethers (LHE) with different molecular weights (380, 640, and 1830 g/mol) with the addition of three types of rubbers (polysulfide rubber (PSR), polychloroprene rubber (PCR), and styrene-butadiene rubber (SBR)). The main purpose of choosing this type of modification and the materials used was the possibility to use it in industrial settings. The modification process was conducted for a very wide range of modifier additions (rubber) per 100 g LHE. The materials obtained in the study were subjected to strength tests in order to determine the effect of the modification on functional properties. Mechanical properties of the modified materials were improved after the application of the modifier (rubber) to polyhydroxyether (up to certain modifier content). The most favorable changes in the tested materials were registered in the modification of LHE-1830 with PSR. In the case of LHE-380 and LHE-640 modified in cyclohexanol (CH) and chloroform (CF) solutions, an increase in the values of the tested properties was also obtained, but to a lesser extent than for LHE-1830. The largest changes were registered for LHE-1830 with PSR in CH solution: from 12.1 to 15.3 MPa for compressive strength tests, from 0.8 to 1.5 MPa for tensile testing, from 0.8 to 14.7 MPa for shear strength, and from 1% to 6.5% for the maximum elongation. The analysis of the available literature showed that the modification proposed by the authors has not yet been presented in any previous scientific paper.


2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Kun Zhang ◽  
Bairu Lu ◽  
Yihong Wang ◽  
Zhijun Lei ◽  
Zhanshen Yang

According to the latest UN statistics, more than 2 billion people in the world still live in various forms of earthen buildings, including some in China. The variety of earth-based constructional materials is significant among different regions, with each region influencing the selection of local earth construction materials. In this study, earth materials from four regions of China were collected and sorted, with 10 samples from each source, and cube compressive strength tests were performed to analyze the composition and mechanical properties of the four materials, including northeast black earth, southeast red earth, northwest loess, and Xinjiang yellow sand earth. The results showed that significant differences existed in the composition of earth-based constructional materials from different regions, which have influence on the materials’ compressive strength. The order from large to small of compressive strengths was loess, black earth, yellow sandy earth, and red earth. Material load-displacement curves were influenced significantly by the plasticity index, but the overall failure processes of the various samples were basically the same.


Author(s):  
Larry Pax Chegbeleh ◽  
Lawrence Opanin Nkansah ◽  
Frank Siaw Ackah ◽  
Richard Adams Mejida

The importance of concrete as one of the major materials in the building and construction industry cannot be over emphasized due to the myriad benefits and versatility to humankind. However, its performance characteristics on the stability of engineered structures have mostly been overlooked. In this paper, petrographic characteristics and physico-mechanical properties of ten (n=10) rock samples and some quantity of coarse aggregate representing one set of samples, each obtained from two quarry sites around Amasaman and Shai Hills in the Greater Accra Region of Ghana, have been investigated. This study aimed to determine the impact of aggregate size, content and type on the compressive strength of concrete. The study was conducted through petrographic and physico-mechanical properties analyses on the samples obtained. Petrographic studies were performed on the ten (n=10) rock samples from each quarry site, while the physico-mechanical property tests were conducted directly on the coarse aggregate. However, compressive strength tests were performed on cast concretes produced from aggregates with varying sizes and type obtained from the two quarry sites. Results of the petrographic analysis reveal two rock types: Quartzo-feldspathic gneiss and Granodiorites from Amasaman quarry and also two rock types: Gneiss and Meta-granite from Shai Hills quarry. Results of the physico-mechical properties tests are consistent with requirement of approved construction standards. Compressive strength tests show increasing compressive strength of concretes with increasing aggregate nominal sizes of classes A, B and C but show reduced compressive strength for aggregate nominal sizes of class D. It can therefore, be inferred that, aggregate size and content have profound impact on compressive strength of concrete. Also, aggregate type has influence on compressive strength of concrete, as observed in higher compressive strength of concretes produced from the quartzo-feldspathic gneiss and granodiorites than concretes produced from the gneiss and meta-granites.


2020 ◽  
Vol 128 ◽  
pp. 81-88 ◽  
Author(s):  
Paweł Kowalik ◽  
Mariusz Fabijański

The purpose of this study is to present the requirements, methodology, and results of research on the impact of biodegradable oil on plastic components used in the construction of a railway turnout. Briefly discussed are what railroad turnouts are, how they work, and what problems occur with substances used for their lubrication. They have an impact on the mechanical properties and durability of products made of polymeric materials. These types of materials absorb various kinds of chemicals, to a greater or lesser degree, and this affects their properties. For the tests, we used a universal lubrication oil with biodegradable properties, which is its most significant advantage. However, it may not cause deterioration of the turnout operation and change the properties of materials used for its construction. These types of oils require more frequent applications on cooperating components. We used the two most popular polymer materials. The first is high-density polyethylene (HDPE), used to make all kinds of rail spacers, dowels for fixing rails, sleeves, etc. The second, polyurethane (PUR) is most commonly used for rail pads of various shapes. The methodology and results of testing the impact of a lubricant (biodegradable oil) on the change of mechanical properties such as strength and hardness are presented. The tests were carried out at various temperatures; the time of exposure to oil was seven days; the results were referred to samples conditioned under standard conditions. The tests carried out on the impact of the biodegradable lubricant on polymeric materials (HDPE and PUR) showed little effect on the change of strength parameters of these materials. Celem niniejszego opracowania jest przedstawienie wymagań, metodyki oraz wyników badań oddziałania biodegradowalnego oleju na elementy z tworzyw sztucznych stosownych w budo-wie rozjazdu kolejowego. Krótko omówiono czym są rozjazdy kolejowe i jak działają oraz jakie występują problemy z substancjami używanymi do ich smarowania, które nie pozostają bez wpływu na właściwości mechaniczne i trwałość wyrobów z materiałów polimerowych. Materiały tego typu wchłaniają różnego rodzaju substancje chemiczne w większym lub mniejszym stopniu, a to ma wpływ na ich właściwości. Do badań został wykorzystany uniwersalny olej do smarowania o biodegradowalnych właściwościach, co jest jego największą zaletą. Jednak nie może on powodować pogorszenia pracy rozjazdu oraz zmieniać właściwości materiałów użytych do jego budowy. Tego typu oleje wymagają częstszego aplikowania na elementy współpracujące ze sobą. W pracy wykorzystano dwa najbardziej popularne materiały polimerowe. Pierw-szy to polietylen o dużej gęstości (HDPE), z którego wykonuje się wszelkiego rodzaju przekładki podszynowe, dyble do mocowania szyn, tuleje, itp. Drugi to poliuretan (PUR) stosowany najczęściej na przekładki podszynowe o różnym kształcie. Zaprezentowano metodykę i wyniki ba-dań oddziaływania środka smarnego (biodegradowalnego oleju) na zmianę właściwości mechanicznych takich jak wytrzymałość oraz twardość. Badania zostały przeprowadzone w różnych temperaturach, a czas ekspozycji na olej wynosił 7 dób, wyniki odniesiono do próbek klimatyzowanych w standardowych warunkach. Przeprowadzone badania oddziaływania biodegradowalnego środka smarnego na tworzywa polimerowe (HDPE i PUR), wykazały niewielki wpływ na zmianę parametrów wytrzymałościowych tych materiałów.


2018 ◽  
Vol 10 ◽  
pp. 02028
Author(s):  
Urszula Sadowskaʼ ◽  
Andrzej Żabiński ◽  
Krzysztof Mudryk

The objective of the conducted study was to evaluate the impact of the pressure agglomeration process of peppermint herb on the mechanical properties of the obtained product. The separated fractions of peppermint with 0.5-2.5 and 2.5-5 mm particles were compacted using a hydraulic press Fritz Heckert EU 20, with pressure 50, 100, 150 and 200 MPa. A closed matrix with the compression chamber diameter of 15.6 mm was used. Every time, a 2-g herb sample (corresponding to the weight of tea used for the production of tea bags) was poured into the matrix. Thus, compacted herb in the form of a straight cylinder was obtained. When producing the agglomerate compaction work was determined. Strength tests of the obtained agglomerate were conducted using the MTS Insight 2 testing machine. The density of the produced agglomerate, its compaction level and strength in the Brazilian test was calculated. The obtained results indicate that the values of the tested parameters increase with the increase of pressure in the tested range, yet differences occur between the tested herb fractions. Typically, the agglomerate produced from 0.5-2.5 mm fraction is characterized by a greater density, and the higher level of agglomerate compaction is obtained using 2.5-5 mm herb fraction. The highest strength determined using Brazilian test was determined for agglomerate produced from 0.5-5 mm peppermint herb fraction at 200 MPa pressure and 0.5-2.5 mm fraction using 150 and 200 MPa pressure.


2020 ◽  
Vol 41 (1) ◽  
pp. 89-99
Author(s):  
Aureliano Paolo Finch ◽  
John Brazier ◽  
Clara Mukuria

Background Generic preference-based measures (GPBMs) such as the EQ-5D are valid across many conditions, but in some cases, “bolting on” additional dimensions may improve validity. The selection of “bolt-ons” has been based on the psychometric impact of individual dimensions, but preferences provide another important way to select them. This study aims to test the potential of using pairwise choices to inform the selection of bolt-ons for the EQ-5D-5L. Methods General population preferences were collected using an online survey of 1040 UK residents. Three EQ-5D-5L health state pairs were selected based on pairs that had a 50:50 split in respondent preferences from a previous pairwise survey. Participants were presented with pairwise choices of EQ-5D-5L health states without and with bolt-ons of hearing, sleep, cognition, energy, and relationships, each added individually. Logistic models were used to assess the impact of bolt-ons, as well as bolt-ons at different severity levels, on the log odds of responders choosing between health states. Results Preferences varied according to the bolt-ons and their severity level (only levels 1, 3, and 5 were used). Additions of bolt-ons at level 1 generally resulted in nonstatistically significant differences while additions of bolt-ons at level 3 and level 5 produced a negative and statistically significant impact on preferences for the health state with the bolt-on. At level 5, hearing had the largest impact, followed by cognition, relationships, energy, and sleep. At level 3, cognition produced the largest impact, followed by hearing and sleep with similar impacts, energy, and relationships. This ordering offers information for bolt-on selection, with hearing and cognition appearing as the most important. The weight placed on the different health problems is not constant across severity levels between bolt-ons. Conclusions Pairwise choices provide a cost-effective approach of generating information on preferences to support bolt-on selection.


2018 ◽  
Vol 8 (1) ◽  
pp. 27-36
Author(s):  
M. Esmailpour ◽  
K. Rahmani ◽  
S. Piroti

Abstract The use of various additives (admixtures) in concrete and cement products has been considered by various researchers in recent years. Microsilica (Silica fume) can also be considered as one of the most widely used additives (admixtures) in this section. In this study, 120 concrete specimens were constructed using a mix design based on ACI in the laboratory with an overview of records and advantages of using microsilica in concrete. The microsilica used in concrete specimens has been considered 2%, 5.5% and 7.5% by weight of cement. Finally impact permeability, tension and uniaxial compressive strength tests were done on concrete specimens and their mechanical properties were evaluated. The results show that microsilica improves the mechanical properties of concrete. The results also show that the use of microsilica in ordinary concrete has a very positive effect in controlling the surface cracks and increasing some strength parameters such as tensile and compressive strength of concrete.


2021 ◽  
Vol 17 (6) ◽  
pp. 58-63
Author(s):  
T.S. Kuzmenko ◽  
S.I. Vorotyntsev

The work is devoted to the study of the influence of individualized protective ventilation support on pulmonary mecha-nics. The study included 47 patients who underwent open abdominal surgery under general anesthesia. All patients had a moderate to high risk of developing postoperative pulmonary complications by the ARISCAT scale. Intraoperatively, the impact of individualized protective ventilation on respiratory mechanics, namely Ppeak, Pplat, Pdrive, dynamic pulmonary compliance was assessed. Individualized protective respiratory support was ventilation with a tidal volume of 7 ml/kg of ideal body weight, with the selection of the optimal level of positive pressure at the end of exhalation (PEEP), focusing on dynamic pulmonary compliance and performing recruiting maneuver, and then in the case of a decrease in dynamic pulmonary compliance by more than 20 %, followed by re-selection of PEEP. The studied parameters were recorded before and after the recruiting maneuver, as well as on the 30th, 60th, 90th, 120th, 150th, 180th minutes after the recruiting maneuver, depending on the duration of the operation. The use of alveolar straightening techniques led to an improvement in pulmonary mechanics, namely, an increase in dynamic pulmonary compliance by 16 % and a decrease in Pdrive by 17 %. The intraoperative level of PEEP averaged 4 [4; 5] cm of water. No cases of hypoxemia or recurrence of recruiting maneuver were reported. The obtained results indicate that chosen technique of recruiting maneuver is effective and safe, and its use allows reducing the negative impact of mechanical ventilation. The study did not find a statistically significant correlation between the level of PEEP and the value of dynamic pulmonary compliance. Such data prove the need for individual selection of ventilation parameters according to the characteristics of the mechanical properties of each patient.


Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 804 ◽  
Author(s):  
Anna Rudawska

The aim of this study was to analyse the impact of the adhesive samples seasoning conditions (temperature and time) on selected mechanical properties of four epoxy adhesive compounds (two unmodified and two modified ones). The samples were made of Epidian 53 epoxy resin mixed with the two different amine curing agents in appropriate stoichiometric proportions. A filler in the form of calcium carbonate (CaCO3) powder was used as a modifier. The adhesive compound samples were cured for seven days. Six seasoning variants were used. Four of them were related with the seasoning time at ambient temperature of 24 ± 2 °C for: one month, two months, five months and eight months, respectively. Two other variants were related with seasoning at negative temperature (−10 ± 2 °C) for one month. The last variant (F) also included seasoning at ambient temperature (24 ± 2 °C) for five months right after seasoning in negative temperature. Cured and cylinder-shaped adhesive compound samples were subjected to compressive strength tests (according to the ISO 604 standard). The strength tests were performed using a Zwick/Roell Z150 testing machine. Based on the tests, it was observed that both temperature and time of seasoning influenced the adhesive’s mechanical properties. In the perspective of eight months, these changes were relatively minor for the samples seasoned at ambient temperature. The adhesive samples prepared for the tests were especially sensitive to negative temperature.


2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Zhuoran Liu ◽  
Jinyang Huo ◽  
Zhenjun Wang

In order to investigate the influences of emulsifier types on properties of cement bitumen emulsion mortars (CBEM), anionic and cationic emulsifiers were used to prepare CBEM in this work. Influences of anionic and cationic bitumen emulsions on workability, mechanical properties, and viscoelastic property of CBEM were studied. The workability of CBEM was evaluated by fluidity and extensibility tests. The mechanical properties were assessed by compressive strength and flexural strength tests. XRD was used to analyze the phase before and after bitumen emulsion was added. The viscoelastic property was studied by a dynamic mechanical analyzer (DMA). The results show that CBEM prepared by cationic bitumen emulsion (CBE) has better workability. The mechanical properties of CBEM are negatively affected by bitumen emulsion. The impact on the compressive strength of CBEM prepared by CBE is higher. Bitumen emulsion can significantly improve the viscoelastic property of CBEM. With the increase of bitumen emulsion dosage, the loss factor of CBEM increases. The viscoelastic property at low frequency is better than that at high frequency. In contrast to CBEM prepared by CBE, CBEM prepared with anionic bitumen emulsion (ABE) possesses better viscoelastic property.


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