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Metro Tunnels
Published in S. Ponnuswamy, D. Johnson Victor, Transportation Tunnels, 2017
S. Ponnuswamy, D. Johnson Victor
The gradient permissible is dependent on the tractive capacity of vehicles. A minimum drainage gradient of 0.3% is to be provided. At stations, for the purpose of stability of stopped vehicles, this should also be treated as maximum gradient albeit the desirable maximum is 0.2%. There are systems with up to 5% maximum gradient in-between stations on some heavy metros (Boston and Philadelphia). Washington has a 4% grade in its tunnel, Singapore 3% and Kolkata 3%. The gradient should be compensated for curvature (0.04% per degree of curvature). A vertical curve is always introduced when the gradients change. Parabolic vertical curves are preferred. Lengths will be (G1 – G2) x 100, where (G1 – G2) is the algebraic difference between the grades of connected lengths; this is limited to a minimum length of 80 m. The constant profile of any grade is also limited to a minimum length of 30 m (in Toronto it is 150 m). The minimum radius of vertical curve adopted in metros ranges from 1500 m to 3000 m as against 3000 to 4000 m on main line railways. At 80 kmph, which is the normal maximum speed of metros with close station spacing, this would give a vertical deceleration of 0.033 g for 1500 m to 0.017 g for 3000 m. Hence this range is satisfactory. It is also advantageous to provide a vertical grade that ascends to the station and descends out of the station thus providing a camel-back type of track surface at the station (but of uniform grade or level over the station length plus 25 m at either end). This not only helps reduce vertical transportation distance for passengers, but also aids in quick deceleration and acceleration of the vehicle, resulting in some saving of energy. Typical profile for such treatment at stations is given in sketch below.
Hydraulic Performance of Vertically Depressed And Non-Depressed Grate
Published in Urban Water Journal, 2019
Sarah Alia Md Wakif, Nuridah Sabtu
The testing was performed according to different gully system, slope conditions and inflow rates. These three alterations are important as each of them illustrates the actual condition of the pavement drainage system on the highways. The laboratory rig was tilted accordingly based on the slope required. The drainage gradient is the term used to describe the combined slope due to the road surface of cross slope, Ix and longitudinal slope, Iy. The ratio for the cross slope used in this study was 1:80 and 1:40 whilst the ratio for the longitudinal slope was 1:100 and 1:50 based on the British Standard (BS EN 12056-3:2000). Different slopes were tested in order to evaluate the hydraulic performance of the inlet system and the flow behaviours related to the particular slope.
Timber Arch Bridges with V-shaped Hangers
Published in Structural Engineering International, 2019
Roberto Crocetti, Jorge M. Branco, Jorge F. Barros
The bridge was designed for a service life of 80 years, according to current regulations of the Swedish road and railway administration. According to common Swedish praxis, all wood parts of the bridge consist of untreated glulam made out of Norway spruce. Untreated wood obviously needs to be protected from moisture in order to ensure the required durability. Therefore, a 5 mm waterproofing membrane was applied on the top of the deck to prevent moisture from penetrating into the wood from above. Then, an 80 mm asphalt layer was applied on the top of the membrane. The deck was also given a 2% cross slope to provide a drainage gradient so that water will run off the surface of the deck. A piece of bent sheet metal that runs along the entire length of the deck on both sides transports the water away from the deck. A ventilated side panel made of 21 × 120 mm2 board is used to protect the edge beams of the deck and the prestressing anchorage from rain and sun. The panel is fastened to the deck through wood block spacers. The prestressing bars and nuts are made out of galvanised steel (see Fig. 6).