INTERNATIONAL JOURNAL OF CIVIL AND STRUCTURAL ENGINEERING Volume 1, No 3, 2010

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1 Analysis and Design of Underpass RCC Bridge Mohankar.R.H 1, Ronghe.G.N 2 1 Lecturer, Civil Engineering Dept., G.H Raisoni College of Engineering, Nagpur, India. 2 Professor, Applied Mechanics Dept., Visvesvaraya National Institute of Technology, Nagpur, India roshanohankar@gail.co ABSTRACT The Underpass RCC Bridge is very rarely adopted in bridge construction but recently the Underpass RCC Bridge is being used for traffic oveent. In this paper, the analysis of the underpass RCC bridge is carried out. The analysis of this underpass RCC bridge is done by considering fixed end condition. Finite Eleent Method (FEM) analysis is perfored and results are presented. Coparison of different forces between 2D and 3D odels for fixed end condition is provided. In this study we show a 2D odel can be effectively used for analysis purpose for all the loading condition entioned in IRC: 6, Standard Specifications and Code of Practice Road Bridges The Indian Roads Congress and Directorate of bridges & structures (2004), Code of practice for the design of substructures and foundations of bridges Indian Railway Standard. Keywords: RCC Underpass bridge, FEM analysis. 1. Introduction The Underpass RCC Bridge is very rarely adopted in bridge construction but recently the Underpass RCC Bridge is being used for traffic oveent. This underpass RCC bridge is pushed inside the ebankent by eans of hydraulic jack syste Since the availability of land in the city is less, such type of bridge utilizes less space for its construction. Hence constructing Underpass Bridge is a better option where there is a constraint of space or land. Detailed analysis and design of underpass RCC bridge has not been carried out till date. Ronghe G. N. and Gatfane Y. M ( ) have worked on the analysis and design of 2D underpass RCC bridge odel. In this paper 2D along with 3D analysis of underpass RCC bridge is carried out considering six different loading conditions and eight different loading cobinations which are considering fro IRC: , Standard Specifications And Code Of Practice Road Bridges The Indian Roads Congress and Directorate of bridges & structures (2004), Code of practice for the design of substructures and foundations of bridges Indian Railway Standard. The end condition is considered to be fixed for both 2D and 3D underpass RCC bridge odel. 1.1 Modeling of syste For the study of Underpass RCC bridge, earth pressure acting on side walls of underpass RCC bridge because structure ebedded as well as vertical loading due to iposed load 558

2 and live load fro Bridge rules, Rules specifying the loads for designing the superstructure and sub structure of bridges and for assessing the strength of existing bridges (Indian Railway Standard code) on the top of underpass RCC bridge is considered. As there is a top loading, there is reaction at botto also. This underpass RCC bridge is provided for city traffic also. For that purpose live load fro IRC: inside the underpass RCC bridge is considered. Vertical Earth Pressure due to backfill Earth Pressure due to backfill Reaction at botto Figure 1: 2D Model of RCC Underpass Bridge 2D underpass RCC bridge odel shown in Figure 1 is analyzed considering without soil structure interaction. Figure 2: 3D Model of RCC Underpass Bridge 3D underpass RCC bridge odel shown in figure 2 is analyzed considering without soil structure interaction. 559

3 2. Forulation 2.1 Loads on the top of slab Total load for bending oent and shear force is considered fro IRS code rules specifying the loads for designing the super structure and sub structure of bridges and for assessing the strength of existing bridges. For span of 8 total load for bending oent 981kN and total load for shear force is 1154kN is considered. Dead load of earth fill over the box = Area x depth x density 1.1 Total vertical pressure on top slab = Iposed load + Dead load + Live load Loads on sidewalls The coefficient of active earth pressure of the soil is given by the equation 2 cos ( φ α ) Ka = 2 2 sin ( ) ( φ + δ ) sin ( φ i ) cos α cos α + δ 1 + cos ( ) cos ( ) α δ α i 1.3 where, γ = Density of soil, ф = Angle of internal friction,δ = angle of friction between wall and earth fill Where value of δ is not deterined by actual tests, the following values ay be assued. (i) δ = 1/3 ø for concrete structures. (ii) δ = 2/3 ø for asonry structures. i = Angle which the earth surface akes with the horizontal behind the earth retaining structure ( i =0 0 for ebedded structure). Since this concrete structure is ebedded in soil, the value of δ is considered as 1/3 ø (for concrete structures) considered for calculation of coefficient of active earth pressure of the soil. 2.3 Earth pressure acting on the sidewalls: 2.3. a) Earth pressure due to backfill Earth pressure center of top slab = Ka γ H 1.4 Earth pressure center of botto slab = Ka γ H b) Earth pressure due to dead load surcharge Earth pressure acting on sidewalls: At Top = Iposed load of track + Earth pressure on the top of slab + Live load 1.6 AT Botto = Horizontal effect of surcharge + Earth pressure center of botto slab

4 2.4 Reaction at the botto of box Self weight of box = Weight of top slab + Weight of botto slab + Weight of side walls 1.8 Total reaction at botto=self weight of box +Weight of iposed load +Weight of live load 1.9 The boundary condition considered is fixed. 3. Analysis of 2D underpass RCC bridge odel A 2D underpass RCC bridge (Figure 1) is odeled considering 1 length for the following details shown below. Box diensions: 1x7.5x4.1 (LxWxH) (Center to center). In addition to the diensions entioned in Figure 3, following paraeters are considered for the 2D analysis. Keeping all the paraeters sae, the analysis is carried out using two ethods viz. conventional slope deflection ethod (anual calculations) and other by using SAP2000 (prograing software). The anually calculated values for the bending oent at corner A is 205kN and corner C is 302kN for dead load case. For the sae corners A & C, the SAP results are found to be 203kN and 298kN respectively A B C D (a) (b) Figure 3: (a) Center to center Diensions of RCC Underpass Bridge (b) Diensions of RCC Underpass Bridge Diensions of underpass RCC bridge Clear horizontal opening 7 Clear vertical opening 3.5 thickness 0.6 Wall thickness 0.5 Outer to outer horizontal width 8 Outer to outer vertical height 4.7 Length underpass RCC bridge 1 Angle of internal friction (ф) 25 o Density of soil (γ) 19 kn/ 3 Grade of concrete M40 561

5 Grade of steel Fe415 The ax BM and SF obtained for 2D underpass RCC bridge odel considering without soil stiffness are shown in Table 1. Shear force and bending oent diagra after analysis is shown in Figure 4 (a) & (b) (a) (b) Figure 4: (a) SF diagra for 2D Analysis (b) BMD For 2D Analysis 3.1 Validation of results The bending oent results obtained by slope deflection ethod and SAP2000 progra for 2 diensional odel of underpass RCC bridge are approxiately sae. The slight variation of results ay be due to the variation of oent of inertia values. Based on this validity of results further analysis of sae 2D odel for various cobinations of loading cases was carried out. Also it was observed that was the sae corners of the 3D odel the bending oent results obtained were sae and hence 3D analysis was carried out using SAP2000. Table 1: Max BM and Max SF of 2D Meber Top Botto Side Walls Results Max BM & Max SF of 2D odel without soil stiffness (kn ) Max SF BM Mid Span BM Corner Max SF BM Mid Span BM Corner Max SF BM Mid Span BM Corner

6 3.2 Analysis of 3D underpass RCC bridge odel A 3D underpass RCC bridge is odeled considering total length 13 with details shown above and there is no change in details except length. Box diensions: 13x7.5x4.1 (LxWxH) (Center to center).the ax BM and SF obtained for 3D underpass RCC bridge odel considering without soil stiffness are shown in Table 2. Table 2: Max BM and Max SF of 3D Meber Top Botto Side Walls Results Max BM & Max SF of 3D odel without soil stiffness(kn ) Max SF BM Mid Span BM Corner Max SF BM Mid Span BM Corner Max SF BM Mid Span BM Corner Coparison of Result of 2d & 3d Underpass Rcc Bridge Model The coparison of the axiu bending oent and shear force values obtained for 2D and 3D underpass RCC bridge odels which are considered without soil stiffness are copared. The coparison between these two results (Table 3) shows that the values of bending oent and shear force for 2D and 3D odel for all loading cases considered for the analysis purpose fro IRC: , Standard Specifications and Code of Practice Road Bridges The Indian Roads Congress and cobinations, are approxiately sae. Table 3: Coparison of Max BM and Max SF of 2D odel and 3D odel of the box Coparison of Max BM of 2D & 3D odel without soil stiffness Meber Results Max BM of 2D Max BM of 3D % odel without soil odel without soil Difference stiffness (kn ) stiffness (kn ) Max SF Top BM Mid Span BM Corner

7 Botto Side Walls Max SF BM Mid Span BM Corner Max SF BM Mid Span BM Corner Conclusions Fro the analysis it can be observed that bending oent and shear force obtained for 2D and 3D odel are approxiately sae. A 2D odel can be effectively used for analysis purpose for all the loading condition entioned in IRC: 6 and Directorate of bridges & structures (2004), Code of practice for the design of substructures and foundations of bridges Indian Railway Standard. Further research is needed to verify the use of 2D odel for different paraeters such as dynaic analysis, soil structure interaction etc. 6. REFERENCES 1. Ronghe G.N. And Gatfane Y.M. "Analysis And Design Of A Bridge By A Push Back Syste. A Dissertation of M.tech In structural Engineering Directorate of bridges & structures (2004), Code of practice for the design of substructures and foundations of bridges Indian Railway Standard. 3. IRC: , Standard Specifications And Code Of Practice Road Bridges The Indian Road Congress. 4. IS 456:2000, Plain and Reinforced concrete code for practice Bureau of Indian Standards. 5. IRC: , Standard Specifications And Code Of Practice Road Bridges The Indian Road Congress. 6. IRC: , Design criteria for pre stressed concrete road bridges (Post Tension concrete) The Indian Roads Congress. 564