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- Al-Emrani, Mohammad, 1967, et al.
(författare)
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Experimentelle untersuchung des ermudungsverhaltens genieteter trager
- 2002
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Ingår i: Stahlbau. ; 71:2, s. 145-150
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Tidskriftsartikel (refereegranskat)abstract
- The results from ten fatigue tests performed on six full-scale riveted stringers are presented and discussed. The stringers were taken from a 100 year old bridge, and the tests were performed at two different stress ranges: 60 and [similar to] 100 MPa. The tested stringers showed an excellent fatigue performance and their fatigue lives were in correspondence with or above the fatigue design curve given by the codes. Furthermore, the efficiency of using stop-holes to retard fatigue crack propagation in riveted girders was examined. The method was found to be an effective measure when aimed at temporarily arrest the crack propagation in riveted girders.
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| 3. |
- Al-Emrani, Mohammad, 1967, et al.
(författare)
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Fatigue performance of stringer-to-floor-beam connections in riveted railway bridges
- 2004
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Ingår i: Second International Conference on Bridge naintainace, Afety and Management.
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Konferensbidrag (refereegranskat)abstract
- Stringer-to-floor-beam connections in riveted railway bridges have in many casesshown to be critical details with respect to fatigue. These connections, while generally designedwith respect to shear forces alone, are often subjected to repeated out-of-plane distortion as a re-sult of their rotational stiffness.Static and fatigue tests involving three full-scale bridge parts have been conducted in order to study the behavior and the fatigue performance of riveted double-angle connections. The bridge parts were taken from an old riveted railway bridge built in 1896 and demolished in 1993. Each test specimen consisted of three floor beams and four stringers connected to each other with riv-eted double angles. Fig. 1 shows the set-up of the test specimens and loading arrangement, to-gether with a detail of the double-angle connections. Finite element analysis of the tested specimens was also performed in order to more closely study the load-deformation characteris-tics of these connections.
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| 4. |
- Al-Emrani, Mohammad, 1967, et al.
(författare)
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FE analysis of stringer-to-floor-beam connections in riveted railway bridges
- 2003
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Ingår i: Journal of Constructional Steel Research. ; 59:7, s. 803-818
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Tidskriftsartikel (refereegranskat)abstract
- The results from ten fatigue tests performed on six full-scale riveted stringers are presented and discussed. The stringers were taken from a 100 year old bridge, and the tests were performed at two different stress ranges: 60 and [similar to] 100 MPa. The tested stringers showed an excellent fatigue performance and their fatigue lives were in correspondence with or above the fatigue design curve given by the codes. Furthermore, the efficiency of using stop-holes to retard fatigue crack propagation in riveted girders was examined. The method was found to be an effective measure when aimed at temporarily arrest the crack propagation in riveted girders.
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| 5. |
- Al-Emrani, Mohammad, 1967, et al.
(författare)
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Overlooked Secondary Effects in Open-Deck Truss Bridges
- 2004
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Ingår i: Structural Engineering International. ; 14:4
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Tidskriftsartikel (refereegranskat)abstract
- Deformation-induced fatigue cracking has been a common source of fatiguedamage in steel bridges. These damage cases are often the result of secondaryrestraint forces generated by an unintended or overlooked interaction betweendifferent members in the bridge.A number of these interaction mechanisms areexamined in this paper using finite element analysis of a case-study bridge. Fieldmeasurements performed on the bridge were used to validate the analysis. Theresults of the analysis indicate that the effects of secondary forces, which developin different members of the floor system of riveted truss bridges, are generallynot negligible. In particular, the connections between different orthogonal membersof the floor system, such as stringer-to-floor-beam and floor-beam-to-chordconnections, might be critical with respect to fatigue due to these effects.
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| 6. |
- Bengtsson, Charlotte, et al.
(författare)
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Bending creep of high-temperature dried spruce timber
- 2003
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 57:1, s. 95-100
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, bending creep test results from high-temperature (HT) dried Norway Spruce timber are presented. The results are compared with creep tests of conventional low-temperature (LT) dried timber. The HT drying was performed at 115°C and the LT drying was performed at 70°C. The creep tests were performed in a varying climate with 20°C and 30–90% relative humidity. A total number of 24 specimens, 45 × 70 × 1100 mm, were loaded in bending during approximately 240 days. Both the HT-dried and the LT-dried material were cut from the same four trees to have as equal raw material as possible for the two drying methods. The results show smaller bending creep deformations of HT-dried timber (approximately 30%) as compared to the LT-dried timber. The variation in magnitude of creep for HT-dried timber was equal to or smaller than for LT-dried timber. Additionally, the variation in deformation between the moisture cycles was smaller for HT-dried timber. These observations indicate a less pronounced mechano-sorptive effect for HT-dried timber. The free shrinkage in the grain direction was significantly smaller for the HT-dried material than for the LT-dried material.
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| 9. |
- Eklund, Leif, et al.
(författare)
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Spiral grain from an environmental, genetic and economical point of view
- 2000
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Ingår i: The Tree.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Characteristic of wood is that its behavior is strongly orthotropic due to the internal structure of the material and dependent on moisture and temperature. In addition, the material is characterized by a strong variation of the properties in the radial direction. Another important property that affects the behavior of wood is spiral grain, causing the direction of the fibers to deviate from the longitudinal direction of the tree. It is hardly possible to assess spiral grain in the woods, no rejection of severe spiraled trees are done before the log arrives into the sawmill. If a method for on site rejection is available, and the severest spiraled trees, 2-10%, could be avoided in the shipment to the sawmill substantial money could be saved in the forest industry. The causes of spiral grain have been thoroughly discussed through the years and the debate about the environmental and genetic impact on the phenomenon is still not settled. We present evidence for a direct effect of wind on the degree of spiral grain. We also present evidence for a putative thinning effect on spiral grain that is probably connected to wind. Additionally we also present evidence for a strong genetic impact on the formation of spiral grain in conifer trees. In another study mechanical properties such as shape stability has been investigated for the same trees. In some of the logs it may therefore be possible to quantify the relation between spiral grain and distortion in sawn timber.
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