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AS5100.2: 2017 changes to traffic-barrier loadings – a Victorian perspective
Published in Nigel Powers, Dan M. Frangopol, Riadh Al-Mahaidi, Colin Caprani, Maintenance, Safety, Risk, Management and Life-Cycle Performance of Bridges, 2018
An integer number of barrier units is provided in each bridge span. Each barrier unit is nominally 3000 mm long (or 6000 mm). The spacing of posts in both cases is also nominally 3000 mm. It is interesting to note this approach yields barrier lengths 3000 mm (+/-5%) in the span-range 30 m to 200 m, with the variation increasing to (+/-10%) in the range 20 m to 30 m. The lengths of barriers in opposing spans may be different, however this difference should not be noticeable to the observer (compared to the disparate barriers in Figure 4), or consequential to the design.
Introduction: Wood properties, species, and grades
Published in Abi Aghayere, Jason Vigil, Structural Wood Design ASD/LRFD, 2017
These are vertical members that resist axial compression loads and may occasionally resist additional bending loads due to lateral wind loads or the eccentricity of the gravity loads on the column. Columns or posts are usually made from post and timber (P&T) sawn lumber or glulam. Sometimes, columns or posts are built up using sawn-dimension lumber. Wood posts may also be used as the chords of shear walls, where they are subjected to axial tension or compression forces from the over-turning effect of the lateral and seismic loads on the building.
Planning and Preliminary Design of Modern Steel Railway Bridges
Published in John F. Unsworth, Design and Construction of Modern Steel Railway Bridges, 2017
Pedestrian walkways on railroad bridges are typically for the use of only railroad employees and not the general public. The walkway must be outside regulatory or other prescribed railway clearances.* Most railroad companies have policies, generally based on government regulations, regarding walkway and guardrail† requirements for bridges. Width of walkways is often prescribed by the railroad company,‡ but should not be less than 600 mm (2 ft). Walkway surfaces should be a nonslip galvanized steel grating (checker plate) no less than 6 mm (1/4 in.) thick. High toe boards of dimension 100 mm (4 in.) to 150 mm (6 in.) are often installed on walkway surfaces, particularly on ballasted deck bridges over roadways.* Structural members (e.g., knees braces at floorbeams of through plate girder spans) should not be considered as obstructions on walkways designed for the use of railroad employees. Guardrail height is generally prescribed as a minimum of 1067 mm (3.5 ft), with clear distances between railings not exceeding 530 mm (21 in.), by North American regulatory authorities. Nevertheless, depending on the bridge location, greater guardrail heights might be required at some crossings. Posts are usually spaced considering the superstructure framing system, and are typically spaced at intervals of between about 2.5 m (8 ft) and 4 m (13 ft). Handrails and posts consisting of galvanized tubular, pipe, or angle sections not less than 6 mm (1/4 in.) thick are often used for railway bridge guardrails, where adequate strength and safety, without the need to consider a esthetics, are required. AREMA (2015) provides recommendations for the design of pedestrian walkways and guardrails (see Chapter 4). The designer should also consult with the railroad company and applicable regulations concerning specific safety appliances that may be required.
Luminescence dating of Quaternary alluvial successions, Sellicks Creek, South Mount Lofty Ranges, southern Australia
Published in Australian Journal of Earth Sciences, 2020
R. P. Bourman, D. Banerjee, C. V. Murray-Wallace, S. Buckman, D. K. Panda, A. P. Belperio, C. L. Jayawardena
Following European settlement of South Australia in 1836, human-induced erosion related to land clearance resulted in the accumulation of PESA sediments over parts of the Sellicks landscape as sediment was transported from nearby higher country, blanketing the lowlands before the gullies fully developed. Commonly PESA sediments contain European artefacts such as bottles, metal objects and fence posts. Accelerated erosion on upland slopes led to sedimentation lower in the landscape, steepening slopes, smothering channel vegetation and initiating channel incision. The accelerated erosion produced steep trench-like channels stranding PESA sediments at the tops of the banks. In places, new generations of PESA deposits occur within the newly eroded channels, especially upstream of constricted road crossings and other artificial knickpoints. The relationships between the various alluvial successions in Sellicks Creek are illustrated in Figures 4 and 5a, b.
Investigating the Newcomen pumping engine house at Brislington near Bristol
Published in The International Journal for the History of Engineering & Technology, 2018
The life expectancy of an early boiler may have been short and replacement with a pre-constructed one, rather than riveting one in situ, would have been quicker meaning the engine was out of action for less time. The opening is large enough to allow for a boiler to be inserted or removed without demolishing a large part of the engine house. Such a large opening on the outside of the building would have been undesirable. The current lean-to structure covering the arch has similar thickness walls to the engine house. Braikenridge drawings show a lean-to structure in the same location although at least part of the structure is in timber framing with posts supporting the roof. It therefore appears that although likely to be on the same footprint as the original lean to structure at least some of the current building, possibly all of it, is of later construction. The purpose of this building can be determined from comparison with the engravings of the Chelsea engines59 (see Figures 17 and 27). Both engine houses have a similar attached structure, albeit two storey with a dual pitched roof; Watt labels this as ‘Place for Coals’. To determine whether any of the current walls are part of an original structure would need further investigation and is not currently possible.
On-site full-scale tests of a timber queen-post truss
Published in International Journal of Architectural Heritage, 2018
Jorge M. Branco, Humberto Varum, Filipe T. Matos
The geometry of this particular truss is out of the ordinary: its configuration is typical of a king-post truss, but the queen-posts were added by connecting the joint strut/rafter to the tie-beam. This is not the traditional queen-post truss geometry, in which the king-post is substituted by a straining beam connecting horizontally (in the superior part) the two queen-posts, those located below the higher purlin, and the struts connecting the bottom part of the queen-posts to the lower purlins. Clearly, it is an example of a timber truss with an incorrect configuration for the span of the roof. The correct queen-post truss geometry should have been used or two extra posts (princess-posts) should have been placed below the lower purlin. Point loads out of the joints, causing bending moments in the rafters, are the most common error detected in the preliminary survey performed in previous steps of the research program (Branco et al. 2006).