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1.
Influence of test methodology on the characterization of the parallel-to-grain timber embedment strength and foundation modulus of dowels
Caroline D. Aquino, Rodrigues Leonardo G., Michael Schweigler, Meta Kržan, Zheng Li, Jorge M. Branco, 2024, izvirni znanstveni članek

Povzetek: A reliable determination of the embedment strength and foundation modulus of timber elements is critical for the design and safety assessment of joints in timber structures. However, the existence of various test configurations for characterising the embedding properties of large diameter steel fasteners in timber elements poses challenges in directly comparing and utilising available test data. This paper aims to provide an insight into the influence of embedment property test methods, comparing experimental results from different test setups within the guidelines of the EN 383 and ASTM D 5764-97a standards for European softwood species, Scots pine wood (Pinus sylvestris) and Norway spruce (Picea abies). In addition to the test guidelines, the thickness of the specimen and the application of the load was evaluated within the protocols. A comprehensive statistical analysis was performed to identify statistically significant differences between the groups evaluated. The results of the analysis revealed disagreement between the standards in the evaluation of the strength of the embedding, highlighting the potential bias inserted by the experimental setup and protocol. Furthermore, it was proven that the thickness of the specimens influences both the embedding strength and the foundation modulus of the wood species tested. Finally, no distinctions were observed between tensile and compressive loading within the guidelines of the EN 383 standard.
Ključne besede: embedment strength, foundation modulus, dowel-type connections, test methods
Objavljeno v DiRROS: 15.04.2024; Ogledov: 54; Prenosov: 28
.pdf Celotno besedilo (3,96 MB)
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2.
Quality checking of polymer modified bitumens in Slovenia
Marjan Tušar, Lidija Ržek, Mojca Ravnikar Turk, 2021, objavljeni znanstveni prispevek na konferenci

Povzetek: For many years the properties of bitumen have been determined based on mechanical tests as needle penetration, Ring&Ball and Fraass fracture temperature. For elastomer (styrene-butadiene-styrene) polymer modified bitumens these tests are not sufficient to show the important differences in bitumens. Elastic recovery and cohesion provide better insight, but rheological properties cannot be adequately described with conventional test. The requirements of the polymer modified bitumens (PmB) in Europe were defined in EN14023 in 2010 [1]. Since then several new tests were introduced in the research field and their procedures improved. In the European Standards Committee (CEN) TC 336, there is on-going work to develop performance related specifications. New laboratory test methods from American standards were adapted and transformed into EN standards (bitumen laboratory aging methods and rheological tests). These test methods are not yet employed in the cur-rent PmB European standard, however, the draft prEN 14023, April 2020 [2] suggests these new tests. In the recent years at ZAG Laboratory for asphalts and bitumen-based products long-term aging of bitumen by pressure aging vessel (PAV) and rheological tests were introduced. Traditional bitumen test methods are performed together with new rheological testse.g. Dynamic Shear Rheometer (DSR) testing, to characterize complex modulus and phase angle, and Multiple Stress Creep Recovery Test (MSCRT) in order to develop a preliminary data base on PmB’s, which are frequently used in Slovenia. The paper presents the current requirements for PmB’s in Slovenia and test results on PmB 45/80-65, original, laboratory aged and extracted from produced asphalt mixtures.
Ključne besede: polymer modified bitumen, recovered bitumen, laboratory ageing, dynamic shear rheometer, multiple stress creep recovery test
Objavljeno v DiRROS: 28.02.2024; Ogledov: 113; Prenosov: 73
.pdf Celotno besedilo (703,78 KB)
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