DESIGN OF CABLE STAYED PEDESTRIAN BRIDGE

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DESIGN OF CABLE STAYED PEDESTRIAN BRIDGE T.Nelson ponnu durai 1 Dr. P.Asha and R.Vinoth kumar 3 1 Final Year P.G Structural, St. Peter s University HOD CIVIL Department St.

1 DESIGN OF CABLE STAYED PEDESTRIAN BRIDGE T.Nelson ponnu durai 1 Dr. P.Asha and R.Vinoth kumar 3 1 Final Year P.G Structural, St. Peter s University HOD CIVIL Department St. Peter s University 3 Assistant Professor,Civil, St. Peter s University, Abstract: This paper intends to describe the conceptual design of a CABLE STAYED PEDESTRIAN CROSS OVER BRIDGE, near Koyembedu bus terminus. The development of detailed design and critical issues associated with bridge deck, cables and tower are briefly discussed. The bridge is constructed for easy movement of people crossing the expressway and to avoid fatal accidents. Live load acting on the bridge is transferred to the bridge deck, which in turn both the dead load of the superstructure (self-weight of the bridge deck) and live load of the bridge is balanced by tension cables which is anchored to the tower. The tower of the bridge carries the total working load. Additional columns are provided at the end supports. The design is aimed to meet the requirements. 1. Introduction A cable-stayed bridge has one or more towers from which cables support the bridge deck. A cable-stayed bridge is not a suspension bridge type. Hence No end anchorage is necessary. The cable stayed pedestrian bridge is taken into idea for developing the transportation, and its infrastructure to meet the needs and demand of the growing population whilst retaining its distinctive and valued market town character. This project has been proposed especially for pedestrian safety considerations, where the cable stayed cross over structure will serves as a best for both pedestrians and the fastest moving traffic. The structure provides a strategic and easy access to the bus terminus and in conjunction with the six lanes state highway would enable the traffic to flow at high speed so that the flow should not be disturbed in turn saving the destination, fuel and prevents hazards at a time. The CMBT provides the potential to attract a range of new businesses including government departments/relocations by virtue of its domestic transport links, and the quality of its riverfront of aesthetic environment. The bridge caters to the requirement of motorists, pedestrians and cyclists. This bridge is henceforth referred as the cable stayed pedestrian cross over bridge in this design project. 1.1 Objectives 1. To design a cable stayed pedestrian cross over bridge (Harp design) for an expressway, to avoid fatal accidents.. Components of a cable stayed pedestrian bridge to be designed: 3. Tower (or) Pylon 4. Bridge deck 5. Cable 6. Support Columns 1. Scope of Work The scope of the project included the Preliminary Design of Pedestrian Footbridge. Specific requirements of geometric and structural design were obtained from the general data collected in the form of a design and analysis basis note. The construction of the proposed bridge is at an early stage of development in other developed countries and not yet in India and needs to be taken through simple procedures, The development of the scheme shall be undertaken by any kind of Bridge and iron companies, NHAI, IRC or any other private firms which so ever is economic to both the public and private sectors The project shall be the subject of a competitive tendering process, which shall involve national road building contractors. 1.3 Our Vision: To avoid fatal accidents To efficiently convey the traffic To ultimately decrease the destination time To avoid traffic congestion To feed a continuous flow of traffic.. Study Area Fig..1 study area ISSN: Page 55

2 .1 Reasons for Selecting the Location: It became tedious for the pedestrians to cross the road in peak hours. Also, the vehicles are stopped for pedestrian crossing which disturbs the traffic flow. To avoid fatal accidents.. Plan and Elevation: Reinforced Concrete Slab. The slap is precasted in 10 parts in a dimension of 3m x 3.5m. dl x = 3m (shorter span) L y = 3.5m (longer span) L y /L x <, therefore the slab is -way slab. Calculation of depth of slab: Design for -way slab According to clause 4.1 of IS 456:000, L x = (35 x 0.8) Here, the material are taken as M 0 concrete and Fe 415 (high strength steel bars) 3000 / D = 8 D = 110 mm Providing an effective cover depth of 5mm d eff = = 85 mm d = 85 mm 4. Load calculation: 4..1 Design for wind pressure: According to clause 5.4 of IS 875 part 3, The design wind pressure, p x = 0.6v x v x is the velocity of wind at the locality which is 45 m/s, Equating the value to the above equation, design wind pressure, 3. Methodology: Case study of the road Journals Plan Design of structural components Analysis of structural components Construction techniques 3.1structural Components to Be Designed Foundation Design Pier ( Column) Design Deck Slab Design ( Girder) Tower ( Pylon ) Design Cable Design ( HARP Arrangement ) Girder Girder Connection Plate Cable Connection Staircase Design Installation of Hand rail 4. Designs of Components: 4.1 Design of bridge deck: The total span of the bridge is 30m. Since it is difficult to construct cast in-situ bridge deck over a heavy traffic road. The deck is designed to be p x = 0.6 x 45 = 1.5 KN/m Self weight of slab = 0.11 x 5 =.75 KN/m Live load of slab = 5 KN/m Total load = 9 KN/m Ultimate load, w u = 1.5 x 9 = 13.5 KN/m. Moment calculation: According to D of Annex D in IS 456: 000, M x = α x w u l x M y = αy w u l x Where the values of α x and αy are computed from table 7 of IS 456: 000 L y /L x = By double interpolation method, α x = α y = Moment in shorter span, M x = α x w u l x = x 13.5 x 3 = KN- m Moment in longer span, My = αy w u l x = x 13.5 x 3 = KN m Check for ultimate depth: M max = f ck b d x 10 6 = x 0 x 1000 x d d = < p rovided = 85 mm. Area of reinforcement calculation: For shorter span, M x = KN m M x = 0.87 f y A st d [1 A st f y / b d f ck ] x 10 6 = (0.87 x 415 x 85) A st [1 A st x 415 / 1000 x 85 x 0] A st = mm. Provide 10mm diameter bars at spacing of 00 mm is shorter span. For longer span, ISSN: Page 56

3 M y = KN m x 10 6 = (0.87 x 415 x 85) A st [1- A st x 415 / 1000 x 85 x 0] A st = KN m Providing 10 mm diameter bars at spacing of 50 mm in longer span. Check for shear: V u = w u l x / = 13.5 x 10 3 x 3000 / V u = 0.5 KN Stress in slab, τv =V u /bd (According to IS 456:000, clause 40.1) = 0.5/100x85 τ v = 0.38 N/mm According to table 19 of IS 456:000 P t = 0.46 τ c = N/mm Permissible stress => τ c. k s 0.468(0.5+ l x /l y ) = 0.37(0.5+3/3.5) N/mm τ c < τ c. k s Therefore the slab is safe in shear. Check for deflection: (L/d) max = (l/d) basic x k t x k f x k c According to cl.3. of IS 456:000, Modification factor = 0.58x415x70/ (4x78.53) From table 19, P t = 0.46 k t = 1.9 (L/d) max= 0x1.9x1x1 = 38 (L/d) actual=3000 / 85 = 35 < 38 So the slab is safe in deflection. Check for crack control: 1. Reinforcement provided is more than minimum percentage of 0.1% (0.1/100)x1000x110=> 13mm. Spacing of main reinforcement not less than 3d ( 3x95=>55mm) 3. Diameter of reinforcement < (D/8) (110/8)= So, the slab is safe in crack control. Reinforcement in cage strips: A st = (0.1/100) x1000x110=> 13mm Provide 8mm dia spacing 80mm c/c L x /8=> 3/8 => 375mm 4.3 Design of cross girder: Load acting on cross girder => 8KN/mm 9x3=7KN/m Factored load, W u = 1.5x7=40.5KN M u = W u l /8=> 60.9 KN.m V u = W u l/=> KN Cross girder is provided below the slabs at the interval of 3m where one end of the both of the slabs meet. Plastic modulus, Z p = M u.γ m0 /f y = 60.9x10 6 x1.1/50=> Z p = cm 3 From Annex H of IS 800:007, Choosing a suitable section of ISWB 00 A= 36.71cm ; D = 00mm;b f =140mm; t f = 7.3mm; t w = 5.4mm Z p = cm 3 ; r 1 = 9.5mm Section classification: b = b f / = 140/= 70mm b/t f = 70 / 9 = 7.78 < 9.4t Therefore Plastic section. d = D-t f -r 1 = 00-x9-x9.5 d = 164mm. d/t w = 164 / 5.4 = 30.37< 84t Therefore plastic section.. Design shears strength for section: According to cl of IS 800:007 V u = V d = V n /γm 0 V n = A v.f y / 1.73 = 00x6.1x50 / 1.73 = KN. V d = / 1.1 = KN. V u < 0.6 V d.(96.03 KN) According to cl of IS 800:007 M d = β b.z p.f y / γm 0 1x x 50 / 1.1 = 66.8 KN.m> KN.m Therefore the selected section is safe. 4.4 Design of main Girder: Load acting on main girder = slab weight = 9x3.5 = 31.5 KN/m Self weight of the cross girder = 0.88 KN / m Total Load = KN/m Ultimate load = 1.5 x = KN/ m Load to be carried by one main girder = / = KN Moment due to load = Wl / 8 = 3.841x15 / 8 M u = KN.m Plastic modulus, Z p = M u.γm 0 / f y = 670 x 10 6 x 1.1 / 50 Z p = cm 3 Assume a section of ISMB 600 Weight per m = 1.6 kg/m ; A = cm ; D = 600 mm ; b f = 10 mm t f = 0.8mm ; t w = 1mm ; Z p = cm 3 ; r 1 = 0mm Section classification: b = b f / = 10 / = 105mm b / t f = 105 / 0.8 = 5.04 < 9.4 t Therefore, the section is plastic. d = D t f r 1 = 550 x0.8 x0 = mm d / t w = / 1 = 43. < 84t Therefore, the section is plastic. Design shears strength of section: V u = W u l / = 3.841x15 / = KN V d = V n / γm 0 V n = A v.f y / 1.73 = 600x1x50 / 1.73 = KN V d = / 1.1 = > V u V u < 0.6V d, ( KN) According to cl of IS 800:007 M d = β b.z p.f y / γm 0 1x3060.4x10 3 x50 / 1.1 M d = KN.m> M u Therefore, the design is safe. ISSN: Page 57

4 4.5 Design of Tower: Load due to slab: 9x3.5x30 = 945 KN Load due to cross girder: 0.88x3.5x11 = KN Load due to main girder: 1.6x30x = KN Total load : KN. Factored load = 1.5x = KN So, selecting a compound section For compound section, λ = 30 to 60 Let us assume λ = 60, f cd = 1 N/mm A req = x10 3 / 1 = mm Area of one section = / = 6330 mm Provide a section of ISMB 5.4 A = 6670 mm ; b f = 140 ; I xx = x10 4 mm 4 ; I yy = 537.7x10 4 mm 4 r xx = I xx / A = x10 4 / 6670 = r yy = I yy / A = 537.7x10 4 / 6670 = 8.39 l eff = 0.8 l = > 0.8x100 = 9600 mm λ zz = k.l / r zz = 9600 / = by reffering table 10 of IS 800:007 b / b f = 350 / 140 =.5 t f < 40 mm For Z-Z axis buckling class A, f cd = N/mm Design load = 6670x = KN I xx = I yy I xx = [I zz + Ah ] = x x (6670 x 0 ) = x ( x10 4 ) = 70.6x10 4 mm 4 I yy = [I yy + (Ah )] = [537.7x (d/ + t w /) ] = [537.7x (d / ) ] 70.6x10 4 = [537.7x (d / d)] 13096x10 3 = 6670( (d / 4) d ) d = mm Horizontal spacing = ( ) = ~ 300 mm Vertical spacing, tan 45 0 = h /300 h = 300 mm Distance between lacings = = 600 Length of lacings = 45 mm Minimum thickness of lacings = l / 40 = ~ 1 mm For minimum width = 3xd = 60 mm Size of lacing plate = 45 x 60 x 1 mm Strength of column due to lacing 1.05xk.L / r = 70.51; f cd = N/mm Design load = x6670 = 108 KN Check for vertical spacing k.l / C.O.G < 50 = 0.8x600 / 5.4 < < 50, Hence the design is safe. Check for lacings k.l / r < 145 r min = ( (1/)x60x1 3 / 60x1) 1/ r min = 3.46 k.l / r = 0.8x45 / 3.46 = 98.6< 145 Check for load carrying capacity, Transverse shear to be resisted = (.5 / 100) 77.5x10 3 = N k.l / r = 98.6, Class C f cd = N/mm P d = A c.f cd = > x 6670 = KN No. of bolts = strength of plate / strength of bolt = > provide 1 bolt of 0 mm dia of 4.6 grades Splice plate: At 4m from top and bottom, 50% of load is transferred to splice Load on splice plate = 77.5 / = KN Load on single splice plate = / = KN Area of splice plate = x 10 3 / 50 = mm Width of the splice plate = = mm Thickness = / = > should not be less than 6 mm. Therefore, t = 6mm. Shear capacity of bolt: Assume 0 mm dia, shear value = 45.7 KN. No. of bolt = / = 6 bolts. Length of Splice plate = 5x50 + x40 = 330 mm Design of Slab base: The compound section of xismb 350 columns is resting on concrete pedestal of M0 grade using slab base plates. Bearing strength of concrete pedestal = 0.45 f ck = 0.45 x 0 = 9 Mpa Factored load resting on compouind column = 1545 KN Area of base plate, A req = 1545 x 10 3 / 9 = mm Properties of ISMB 350 D = 350 mm ; b f = 140 mm ; t f = 14. mm ; t w = 8.1 mm Provide an equal projection of 100 mm on all four edges of column. Size of base plate provided = x40 ( ) = > mm > mm Thickness of base plate: Actual pressure at base, w = 1545x10 3 / 430x650 = 5.5 N/mm t s = (.5w(a 0.3 b ) γm 0 / f y ) 1/ t s = 8. mm Provide a base plate of 1 mm thickness. Connection: Let us use 4 bolts of 0 mm dia, and 400 mm long to anchor the plate of size 430 x 650 x 1 mm Welds, Properly machined column is to be connected to the base plate using fillet weld. The length available for welding, 4(140) + 4( ) + x = mm Strength of weld per mm = 410 x 1.73 / 1.5 = Let, t be the size of weld and l eff be the effective length of weld Eff. Area of weld = 0.7 t.l eff Eq. strength of weld to axial load 0.7t.l erff = 1545 x 10 3 t = 5.6 mm ~ 6 mm. ISSN: Page 58

5 4.6 Design of staircase: Since, the total structure is designed to be of steel elements, the stair case is also designed to be of steel frame with concrete slab. Load acting on the staircase will be equal to that of the load acting on the bridge deck. Therefore, the design elements are the same for both. The girder and the column of the staircase is designed as ISMB600, which is sufficient. Width of the staircase =.5 m Rise = 00 mm Thread = 300 mm 4.7 Design of connections: The connections to various elements are made by bolted connections. Cross girder to Main girder connection: Let us assume 0mm dia of 4.6 grade bolts, Design shear strength of the bolt, V dsb = Vnsb γmb Vnsb = fub nn Anb + ns Asb 3 = KN Bearing strength of bolt, V npb = Vnpb γmb =.5 k b d t f u / 1.5 = KN Number of bolts required to connect cross girder with main girder, load acting on cross girder = bolt value = = bolts Provide bolts in one direstion, therefore to connect the cross girder with the main girder 4 number of bolts with 0mm dia of 4.6 grade is used. Main girder to tower connection: Number of bolts required to connect main girder with tower, load acting on main girder = bolt value = = 8 bolts Therefore to connect the main girder with the tower, 8 number bolts with 0mm dia of 4.6 grades is used. 4.8 Design of foundation: The size of the tower is 430 x 350 mm, the width of the road divider is 1m. Therefore a square footing of dimension 1m x 1m is designed with a minimum depth of foundation as, The soil is of dry and compacted sand till the depth of 7m. The unit weight and angle of repose of the soil is found by the following table. Angle of Table 4.1 Unit weight and angle of repose of the soil Type of soil Unit weight kg/m 3 repose (degree) Sand (dry) Sand (damp) Sand (wet) Sand (dry and compact) Clay (dry) Clay (damp) Clay (wet) The minimum depth of the foundation is found from Rankline formula as, q D min = γ 1 sinφ 1+sinφ Unit weight of soil, γ = 18 Kn/m 3 ; Angle of repose, φ = 40 0 And the total load acting on the foundation is 1545 KN Therefore, minimum depth of foundation = sin40 1+sin40 =85.83 x 0.17 =4.5m A square footing of size 1m x 1m x 4.5m with M 0 grade concrete is used as foundation. 4.9 Design of Cables: The cables are supposed to transfer the tensile load from the bridge to the tower or column as compressive force. 1 number of cables are used with 6 cables in each half span. The cable is attached to the tower at a interval of 50 mm and therefore the cable design is semi harp type. Each cable carries a tensile force of KN TABLE 4. Comparison of Nominal Ultimate and Allowable Tensile Strength for Various Types of Cables, KN Type Bars, A7 type II Locked coil strand Structural strand A586 * Structural rope A603 * Parallel wire Parallel wire, Nominal Tensile Strength ( f pu ) Allowable tensile strength f pu = f pu = f pu = f pu = f pu = f pu = 108 ISSN: Page 59

A41 Parallel strand, A416 70 0.45 f pu = 11.5 Source: CABLE-SUSPENDED BRIDGES Walter Podonly.Jr.P.E Therefore selecting two strands of structural A586* can provide a tensile strength of 146.

6 A41 Parallel strand, A f pu = 11.5 Source: CABLE-SUSPENDED BRIDGES Walter Podonly.Jr.P.E Therefore selecting two strands of structural A586* can provide a tensile strength of KN, which is safe enough to meet the requirements. 4.9 Installation of hand rails: According to safety considerations, the height of railings is specified as 1.3 m and the spacing between ballusters were specified to be 100mm c/c. The railings are installed by rivetted or bolted connections according to site conditions. Materials used for railings are mild steel. 5 Analysis Of Structure Using Modern Methods (Staad Pro) Fig 5.1 3D MODEL CROSS GIRDER MAIN GIRDER ISWB 00 ISMB 600 D=00mm; A=36.71cm D=600mm;A=15 6.1cm TOWER ISMB 350 A=6670cm. STAIRCAS E CONNECT ION FOUNDAT ION CABLES HAND RAILS CONCLUSIONS STEEL FRAME WITH CONCRETE SLAB 4.6 GRADE BOLTED CONNECTION SQUARE FOOTING M0 GRADE CONCRETE A586 CABLE STRANDS MSASTDAFDFAD CFSFJHM A586* CABLE RIVTED BOLTED RAILING OR STEEL WIDTH =.5m; RISE = 00mm TREAD = 300mm 0mm BOLTS DIA 1m x 1m x 4.5m 1 50mm INERVALS. HEIGHT OF RAILINGS = BALUSTER 100mm C/C The cable stayed pedestrian bridge is a reliable and economic structure selected and designed under site conditions for providing the pedestrians an easy and safe access to the other side of the road especially in highways and expressways, thus preventing fatal accidents and thereby delivering the motorists a continuous and efficient flow of traffic thus saving the destination time. The main highlight of the bridge is its aesthetic appearance evolving a scenic view of the place. References: [1]. Dr.S.Ramamrutham, Design of Steel structures chapter 6&7 pp: 171 []. Dr.D.Dayarathnam, Design of Steel structures chapter 5 pp: 145 [3]. B.C.Punmia, Soil mechanics & Foundation Engineering, Chapter 5 pp:707 Fig 5.ANALYSIS RESULTS [4].IS456:000 Plain And Reinforced Concrete- Code Of Practice, Bureau of Indian Standards,pp RESULTS COMPON ENTS BRIDGE DECK MATERIALS USED RCC SLAB PRECAST DIMENSIONS 3.5mx3m TWO WAY SLAB [5]. IS800:007 General Construction in Steel Code of Practice, Section 6,7, Annex F Connections. pp:3-50 [6]. IS 875 (part-3) 1987 Code of practice for design loads for buildings and structures., chapter 5.3, pp:1. ISSN: Page 60

DESIGN AND DETAILING OF COUNTERFORT RETAINING WALL

DESIGN AND DETAILING OF COUNTERFORT RETAINING WALL When the height of the retaining wall exceeds about 6 m, the thickness of the stem and heel slab works out to be sufficiently large and the design becomes