Shear due to wt. Both deck and girder concrete shall be of 28 days crushing cylinder strength f‟c = 25 … The method outlined by M. Pigeaud deals with the effect of concentrated load on slabs spanning in two directions or on slab spanning in one direction where the width-span ratio exceeds 3. = 11,22,000 Nm. ii) Shear due to self wt. analysis of the slab. Dead load shear due to weight of cross beam on outer girder = 1/4 of total shear = ¼ x ½ x 2090 = 260 Kg. A plate girder is a steel beam that is widely used in bridge construction. 6.10 at e.g. i) At mid span, design moment = D.L.M. In designing the girders, the dead load of deck slab, cross-beams, wearing course, wheel guard, railing, etc., may be equally distributed over the girders. The superstructure consists of several parts: The substructure is made of multiple parts as well: Two different girder bridges. 8.16a. A design example followed by a load rating analysis illustrates the engineering computations performed by PGSuper. 8.4 will produce worst effect and will therefore, govern the design. limit state method of design was used for design of pier shaft. 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. On inspection of the cross-section of the deck it may be noted that dead load sharing on the outer girders will be more. where W is the total load. Since it is a two-way slab, the live load moments will be determined by using Pigeaud’s method with Poisson’s ratio of concrete to be 0.15 as advocated in the. Maximum transverse moment per metre length of the-deck at centre is given by: My = b [µ0r1 – µ30r3 + µ50r5]        (8.3), Where rn = (= 1,3,5) = (4w/nπ) sin (nπu/2a) sin (nπc/2a). Now the transverse deck is subjected to moments due to the following dead loads: a) Udl due to wt. i) At mid span, design moment = 31 + 670 = 701 Kgm. 6.10 at e.g. shear = 1.45 x 35,000/3 = 16,916 Kg. Less load on 2.5 m length i.e. shear due to cross-beam on central girder = ½ x ½ x 2090 = 520 Kg. Design a slab and girder bridge with 7.5 m. clear roadway having a span of 12.0 m. between centre line of bearings. With 10 per cent impact, L.L. Loading – Single lane of Class 70-R or two lanes of Class A: Let the cross-section of the deck be assumed as shown in Fig. Shear + L.L. ...Total dead load shear = 2186 + 595 + 2775 = 5556 Kg. [2][3][4][5] However, some authors define beam bridges slightly differently from girder bridges.[6]. This example illustrates the design of a two span cast-in-place post-tensioned concrete box girder bridge. Provide 6 dia. The outer girder has an overhang of 1.765 m. from the centre line of girder and centre to centre distance of girders is 2.45 m. Therefore, the outer girder is also a T-beam. 22.5.3 Precast single span bridge girder (bridge design model) Two traffic bridge design models having one 45 m single span were analysed (see Almansour and Lounis, 2008).They consist of precast/prestressed girders and a cast-in-place … Bridge Concrete Girder Prestressed Concrete Girder Design for Bridge Structure Based on AASHTO 17th Edition & ACI 318-11 ; Bridge Concrete Column Bridge Column Design Based on AASHTO 17th … The deck may consist of 3 girders spaced at 2, 45 m. centres. at the centre of the span. on the inner side. minimum side-face reinforcement on both the faces shall be equal to 0.1 percent of the web area. 2010. Learn about the CSiBridge 3D bridge analysis, design and rating program for the design and optimization of steel girder bridges with composite decks. For simply supported spans, this limit is generally found to be nearly 10 metres and for continuous or balanced cantilever type structures, this limit is 20 to 25 metres. These analyses were … The Ministry of Shipping and Transport (Roads Wing), Govt. (vide dead load calculation for the design of girder) = 925 Kg. Continuous Span Standards. 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. shear + L.L. D.L. 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. Dividing the equivalent width into 4 equal parts, load per part = 6944/4 = 1736 Kg. of each part may be summed up and the transverse moment may be obtained from equation 8.3 assuming u = c = a. As technology advanced the methods were improved and were based on the utilization and manipulation of rock, stone, mortar and other materials that would serve to be stronger and longer. The mechanical device is known as “shear connectors” 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 “composite girders”. Hence, shear to be resisted by bent up bars and stirrups is ½ x 4,56,700 = 2,28,350 N. each. The bridges constructed by Romans were at the time basic but very dependable and strong while serving a very important purpose in social life. Beam bridges are generally considered the simplest form of bridge. The reaction on the outer girder will give the shear on the cross beam. Reinforcement for central girder, As = 11,22,000 x103/ 196×1060 = 5400 mm2, Provide 12 Nos. In the example, Class 70-R tracked vehicle will govern the design. The box is typically rectangular or trapezoidal in cross-section. of each load are: The live load moment on the cross-beam of the same deck has been determined for Class AA (tracked) loading. 8.2a. Design Shear = D.L. Therefore, reaction of each support and as such the total L.L. 6.10 will remain the same. Since θ and α values of both the decks are the same, the influence line for transverse moment coefficients as shown in Fig. 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. The bridge decks have three number T-beams of varying depths depending upon spans. 28 Φ bent up bars in double system as in outer girder = 3,47,800 N. However, not more than 50 percent of the design shear shall be carried by the bent up bars. Span and support moment in the transverse direction per metre = 2872 x 0.8 x 1.25 = 2872 K.gm. You need to start with specifying input parameters to design a specific bridge structure. Deck design follows the NMDOT standard deck slab detail in Chapter 4 of the NMDOT Bridge Procedures and Design Guide, hereinafter referred to as Design Guide. PCI has developed Preliminary Design Charts in accordance with the AASHTO. Design a slab and girder bridge with 7.5 m. clear roadway having a span of 12.0 m. between centre line of bearings. Hence the section is to be modified. D.L. It lets you design different kinds of bridge projects including Box Girder, Spectra, Curved, Prestressed Girder, I-Beams, U-Beams, and many more. 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. 8.11. Shear and Shear Reinforcement near support: Shear taken by outer girder = 3/8 x 9720 x 6.0 = 21,870 Kg. = 6900 Nm. In the example, simple thumb of rules are used to start the AASHTO-LRFD design for prestressed precast girders. A box girder is formed when two web plates are joined by a common flange at both the top and the bottom. Let us widen the web section near the support to same as the bottom bulb as shown in Fig. Hence, the section will be safe with shear reinforcement. 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. Both must work together to create a strong, long-lasting bridge. As the Industrial Revolution came and went, new materials with improved physical properties were utilized; and wrought iron was replaced with steel due to steel's greater strength and larger application potential. Fig shows a laterally buckled view of a portion of the span. The Third Edition of the design specifications, to be published in 2004, will contain a complete set of new The values of the coefficients m1 and m2 are obtained from the curves when the values of U/B , V/L and K (= B/L Shorter Span/ Longer Span)are known. A girder bridge is a bridge that uses girders as the means of supporting its deck. Figure 38.3-3 . Therefore, the effective width of flange for T-beam in terms of Clause 305.12.2 of IRC: 21-1987 is valid for the outer girder. of each part = ¼ (2090) = 520 Kg. The deck slab has to distribute wheel loads to the main girders and also to transfer some load from more highly loaded girders to adjacent ones. Shear at a distance of 2.5 m. (i.e. They serve to help reduce the time required for preliminary bridge superstructure layout, girder plate sizing, and more. for the latter. The spacing of main girders thus affects the design of the slab as well as the number of girders … ... Design L.L.M. Shallow girder depth’s may be used where vertical clearance below the bridge is critical. Bridges,” Chapter 4. 2.45 m. iii) Breadth of web plus 12 times slab thickness = 0.3 + 12 x 0.215 = 2.88 m. Hence 2.45 m. shall be the effective flange width. B-15 in place of B-14 (Appendix B) for the determination of the values: Moment on the cross-beam with 10 percent impact = 1.1 x 17.22 = 18.94 tm. Shear resistance of 2 Nos. as calculated before. The closed cell which is formed has a much greater torsional stiffness and strength than an open section and this is the main reason why box girder configuration is usually adopted in long span bridges. Therefore, the most economical arrangement of bridge deck varies from place to place depending on the cost of materials, shuttering, staging etc., in that locality. Longer spans, more traffic, or wider spacing of the beams will all directly result in a deeper beam. //]]>. It has been observed that three beams deck is generally found economical than two, four or five beams deck having a carriageway for two lanes. Reinforcement per metre depth = 0.1/100 x 300 x 1000 = 300 mm2. bridges to curved steel I-girder bridges (Doust 2011). Copyright 10. Total D.L. Reaction on outer girder = 56.67/3 x 1.45 (distribution co-efficient) = 27.39 tonnes = 27,390 Kgs. Due to local concentration of load, this moment may be increased by 10 percent. //
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