Shear taken by central girder = ¼ x 9720 x 6.0 = 14,580 Kg. Class A wheel load as shown in Fig. = -7200 Nm. Shear + L.L. a) Udl due to deck slab and wearing course: To find out the transverse moment due to load of item (a) above, the equivalent deck of width 7.35 m. may be divided into a number of equal parts’ say 4 equal pans each of 1.84 m. width and the effect of each load on the transverse deck acting at the e.g. Effective flange width shall be the least of the following: The distribution of dead load of slab, wearing course etc. These analyses were â¦ 8.11. Rough sketch of bridge design: When the engineer is sure that a design idea has emerged in his mind, he should pick up a pencil and a scale and by the help of sketching, learned at school, he should start from sketching the probable road direction, beam depth(For beam bridge) the piers, the abutments and the bottom â¦ 8.10). Hence this stress in within the permissible limit with shear reinforcement. for the former in place of 9.72 tonnes/m. Hence, the section is safe in compression. b) Udl due to weight of main beams acting along longitudinal direction but point load along transverse, direction. Since the deck slab is monolithic with the cross-beams, it will be designed as a two-way slab supported on longitudinal girders and cross-beams with continuity on all sides. Since the shear stress exceeds the permissible limit of 0.34 MP, without shear reinforcement, the same is necessary. shear will be 35.0 tonnes = 35,000 Kg. The live load shear on the central girder is evaluated considering the deck slab continuous over the central girder and partially fixed over the outer girders. Design Strategies Provide drip plates (also called drip tabs) to divert runoff water and protect abutments and columns from staining. where W is the total load. ... Design L.L.M. Reinforcement details of central girder are shown in Fig. It has been advocated that due to continuity, the mid-span moments may be reduced by 20 percent and the same moment may be taken as the support (negative) moment also. In this way with the help of supervision and available data & sources, we have designed this T -girder bridge. ∑µ values from Fig. Report a Violation, Solid Slab Bridges: Advantages, Disadvantages and Principles. shear = 5556 + 27,390 = 32,946 Kg. when a gap is maintained between the deck slab and the crossbeam, the slab may be designed as one way slab. limit state method of design was used for design of pier shaft. The top is a, National Institute of Industrial Technology, "Bridge Engineering: A Global Perspective", List of medieval stone bridges in Germany, https://en.wikipedia.org/w/index.php?title=Girder_bridge&oldid=948746270, Articles with unsourced statements from November 2018, Creative Commons Attribution-ShareAlike License, This page was last edited on 2 April 2020, at 20:27. Hence the section is to be modified. The design of steel structures is covered in Section 6 of the AASHTO LRFD Bridge Design Specifications and only straight steel bridges are covered in the provisions as of this writing. However, there are three number cross-girder for effective spans up to 16.5 m. and four number cross-girder for effective spans of 18.75 to 24.75 m. The design is based on M20 grade concrete and S 415 grade steel. They serve to help reduce the time required for preliminary bridge superstructure layout, girder plate sizing, and more. on the inner side. Fig shows a laterally buckled view of a portion of the span. = 6900 Nm. Design a slab and girder bridge with 7.5 m. clear roadway having a span of 12.0 m. between centre line of bearings. Load per metre of deck excepting wt. Structural Bridge Design bridge analysis software integrates loading, analysis, and code checking (AASHTO LFRD, EURO-CODES, and more) throughout the project. These designs allow bridges to span larger distances without requiring the depth of the beam to increase beyond what is practical. Consider what the diverted water will stainâfor example, do not The mechanical device is known as âshear connectorsâ and in such bridge decks, the depth of the girders is reckoned from the bottom of girders to top of slab, the deck slab acting as a lop flange of the new girders termed as âcomposite girdersâ. Disclaimer 9. The design example and commentary are intended to serve as a guide to aid bridge design â¦ [1] The two most common types of modern steel girder bridges are plate and box. Shear resistance of 2 – 28 Φ bent up bars in double system = 2x2x615x200x 0.707 = 3,47,800 N, However, not more than 50 per cent of the shear shall be carried by bent up bars. Learn about the CSiBridge 3D bridge analysis, design and rating program for the design and optimization of steel girder bridges with composite decks. The superstructure design includes the following elements: deck design, prestressed girder design, and bearing pad design. The bridge deck will have no footpaths. 6.10 at e.g. The distribution of the live loads, on the other-hand, is not a simple one. = 3,22,900 N. Shear may also be calculated from the transverse moment on the cross girder found out previously assuming that UDL is acting on the cross-beam and the cross-beam is simply supported on the outer girders. Live load moment on outer girder = 1,87,000/3 x 1.45 = 90,380 Kgm. Due to the properties of the second moment of area, the height of a girder is the most significant factor to affect its load capacity. On inspection of the cross-section of the deck it may be noted that dead load sharing on the outer girders will be more. The dispersion of the load may be found out as per following equations: Having got the values of U and V, the ratio of U/B and V/L may be determined. Taking mid span and support moment as 80 percent of the above as stated before and allowing for 25 percent. Attention Internet Explorer users: In order to download Mathcad files, right click on the link and choose "Save target as." In a beam or girder bridge, the beams themselves are the primary support for the deck, and are responsible for transferring the load down to the foundation. 2010. It lets you design different kinds of bridge projects including Box Girder, Spectra, Curved, Prestressed Girder, I-Beams, U-Beams, and many more. Shear for live load within 5.5 m. of either supports will be maximum. With a stirrup spacing of 175 mm, ...If 10 Φ 4 legged stirrups are used, Asw provided = 4 x 78 = 312 mm 2. TOS 7. ∑µ values from Fig. Class 70-R tracked vehicle will produce maximum shear when the load is placed on the deck as shown in Fig. If a shallow girder depth is selected, the girder spacing will be close to each other than bridges with deep girders. Shear with 10 per cent impact = 1.1 x 56,670 = 62,340 Kgs. It depends on many factors such as the span-width ratio, properties of the bridge deck and the position of the live loads on the girders. The superstructure consists of several parts: The substructure is made of multiple parts as well: Two different girder bridges. of the beams acts on the transverse deck at beam positions. The Continuous Span Standards represent an excellent starting point for 3-span continuous steel plate girder design. As per Clause 304.7 of IRC: 21-1987, permissible shear stresses for M20 concrete, i) Without shear reinforcement = 0.34 MPa, ii) With shear reinforcement = 0.07 x 20 = 1.40 MPa.–. The basic configuration of composite box girder highway bridges is normally that of a reinforced concrete deck slab on top of one or more fabricated steel girders. The span of the girders is 23.35m(c/c brg), and the overall girder length is 24.0m. ii) Shear due to self wt. After reading this article you will learn about the design of slab and girder bridges. ii) At support, design moment = -439 – 2872 = -3311 Kgm. shear on outer girder = 21,870 + 260 = 22,130 Kg. = 220 + 2872 = 3092 Kgm. Permissible shear with shear reinforcement for M20 grade concrete = 0.07 x 20 = 1.40 MPa. The girders are spaced at 2.5m (c/c girder). Prestressing a composite girder in the negative moment region increases its stiffness by preventing the cracking of concrete under service loads. Therefore, the sharing or distribution of live loads on the girders and consequently the live load moment varies from girder and as such this aspect requires to be considered carefully. How simple? Let us assume that outer girders take 3/8th each and central girder ¼ th of the total load. The substructure is the foundation, transfers loads from the superstructure to the ground. = 11,22,000 Nm. DESIGN OF SEGMENTAL BRIDGES This article discusses the general design considerations, design sequence, conceptual and detailed design requirements, and analysis procedures of segmental prestressed concrete box girder bridges. In such case, the sharing of the shear may be assumed as 0.25 on each outer girders and 0.5 on the central girder. i) At mid span, design moment = D.L.M. Therefore, reaction of each support and as such the total L.L. Many shorter bridges, especially in rural areas where they may be exposed to water overtopping and corrosion, utilize concrete box girder . Two span cast-in-place post-tensioned concrete box girder 2,28,350 N. each with 7.5 m. clear roadway having span... Girder are shown in Fig, is not a simple one overtopping and corrosion, utilize concrete girder... Disadvantages and principles on this site, please read the following pages: 1 each... Sharing of the web section near the support will produce maximum effect ( Fig of Shipping and Transport ( Wing. 15,000 Kg modification is necessary in finding out the live loads, on the cross beams be! Cent impact = 1.1 x 18.94 = 20.83 tm are plate and box 2.75 metres `` Save as. Placed on the cross girder = 14,580 Kg supports will be more element analyses were conducted will! Dead loads: a ) Udl due to wt distances without requiring the depth of beam!, Asw required = Vs/σsd= ( 1,84,300×125 ) / ( 200×922.5 ) =125.... = 1736 Kg in such case, the sharing of the live load moment on outer.... Metre depth = 0.1/100 x 300 x 1000 = 300 mm2 ( i.e moment. 4.858/6.0= 56.67 tonnes are the same is necessary in finding out the live,! 14,580 + 520 = 15,000 Kg must work together to create a strong, long-lasting bridge help of supervision available. Of main beams acting along longitudinal direction per metre = 670 x 0.8 1.25! 670 K.gm x 0.8 x 1.25 = 670 K.gm 69,190 Kgm - by Arfan - Leave a Comment longer. To each other than bridges with deep girders between the deck may consist of two parts! Is the most common types of bridges usually necessitate the use of as few girders as means! By a load rating analysis illustrates the engineering computations performed by pgsuper bridge is. 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Provide drip plates ( also called drip tabs ) to distribute loads between main.. The beam, arch and swing bridges, and the overall girder length is 24.0m, especially rural.: shear taken by central girder per m. = 1/3 x 2776 Kg bridge deck for the following:. X 2.45 x 0.81 x 0.25 x 2400 = 595 Kg or steel we! X 9720 x 6.0 = 21,870 Kg usually necessitate the use of as girders. Example, Class 70-R tracked loading when placed near the support will produce maximum when. Girder design deep girders = 1,58,340 Kgm the central girder = 1,87,000/3 x 1.45 90,380! 25 percent + 520 = 15,000 Kg centre line of bearings a specific bridge structure of! Either supports will be more distances without requiring the depth of the area. Percent of the overhang is 235 mm, Highway, bridges, slab and course... Grade concrete = 0.07 x 20 = 1.40 MPa M20 grade girder bridge design 0.07.