Issuu

Parametric Study of Cable-Stayed Bridges with Different Pylon Heights Using STAAD.Pro

Ashwini Ambadas Mapari1, Keshav Raghunath Kale2

1M.Tech Student, Department of Civil Engineering, CSMSS Chh. Shahu College of Engineering, Kanchanwadi, Chhatrapati Sambhajinagar – 431011

2Assistant Professor, Department of Civil Engineering, CSMSS Chh. Shahu College of Engineering, Kanchanwadi, Chhatrapati Sambhajinagar – 431011

Abstract - Cable-stayed bridges are one of the most economical and beautiful bridge structures for long span crossing structures. They can span longer distances with less material and greater structural stability making them ideal for river, valley and urban crossings. This paper deals with the design and analysis of 1400 m long cable-stayed bridge by using STAAD.Pro software. The bridge is composed of a central span with inclined stay cables and a pair of reinforced concrete pylons. The analysis takes into account dead load, live load, wind load, seismic load and pretension forces in cables. A three dimensional finite element model is created in STAAD.Pro to simulate the response of the bridge's structure to different loads. The outcomes show that the cable-stayed bridge offers good load distribution, lesser bending moments in the deck and can be considered as an efficient structure. The study shows the effectiveness of STAAD.Pro, as a tool for analysing complex bridge structure, and highlights the importance of proper cable arrangement, pylon design, for structural safety and serviceability.

Key Words: Cable-Stayed Bridge, STAAD.Stay Cables, Finite Element Method, Bridge Design, Structural Analysis, Long Span Bridge, Pro.

1. INTRODUCTION

Transportation infrastructure is an important enabler for economic and social development of a country. Bridges play a vital role in the transportation infrastructure, allowingforthesafeandefficientpassageofvehiclesover natural or man-made barriers like rivers, valleys, highways, and railways. As traffic demands grew, and the need for longer spans became greater, engineers have evolvedintoamoresophisticatedrangeofbridgesthatare bothstructurallyefficientandarchitecturallyelegant.

Cable-stayed bridges are very popular of the last few decades among the various types of bridges. Characteristics of these bridges are that one or more pylon(s) directly carries the bridge deck. In cable-stayed bridges,theloadsaredirectlypassedfromthedecktothe pylonsviathestaycables,whereasinasuspensionbridge, the deck is suspended by vertical hangers attached to a maincable.

The cable-stayed structure has many merits such as light weight, high stiffness, efficient load transmission, low maintenance and aesthetic appearance. The specific features make cable-stayed bridges applicable for spans between200mandmorethan1500m.

Thecurrentprojectdealswiththedesignandanalysisofa 1400m cable-stayed bridge designed using STAAD.Pro software. The bridge is modelled as a three-dimensional structure, and its response to different loading conditions is investigated. The analysis will be used to assess the structural performance of the bridge and will be used to identify the important design parameters that affect the bridge'sperformance.

1.1 Objectives of the Study

Theprimaryobjectivesofthisresearcharegivenbelow:

 To develop a three-dimensional model of a cablestayedbridgeusingSTAAD.Pro.

 Todeterminetheeffectsofdeadload,liveload,wind load,andseismicloadonthebridgestructure.

 To analyze cable forces, deck displacements, and pylonstresses.

 To evaluate the structural performance of the bridge underdifferentloadingcombinations.

 To assess the suitability of STAAD.Pro for long-span bridgeanalysisanddesign.

1.2 Literature Review

There are several studies carried out on the behaviour of cable-stayedbridgesundervariousloadings.Theresultsof some bridge engineers' research have shown that the cable-stayed bridge is more stiff than the suspension bridge for medium and long span bridges. Research indicates that the configuration of the cables can have a significant effect on the deck deflection and the forces acting on the pylons. Because of cable-stayed bridge geometryandnonlinearbehaviour,finiteelementanalysis technique has been extensively applied for modeling cable-stayed bridges. Computer software like STAAD. Structural responses have been analysed under static and

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 13 Issue: 06 | Jun 2026 www.irjet net p-ISSN: 2395-0072

dynamic loading by using Pro, SAP2000, MIDAS Civil and ANSYS.

Somepreviousresearchhasshownthatthesetwotypesof cable arrangements (fan-type and harp-type) are used in contemporary bridge designs. The fan-type arrangements are typically designed to provide process, especially for long-span bridges where dynamic responses can become critical.

1.3 Literature Comparison Table

Author(s) & Year

1 Shahetal. (2021) SAP2000 Differentpylon configurations

2 Kallingal& Singh(2021) CSIBridge H,A,Diamondand Inverted-Ypylons

3 Zhangetal. (2021) ANSYS

4 Fawzyetal. (2022) FiniteElement Model

Arch-shapedpylon geometry

Seismicperformance underdifferent geometries

5 Mehaboob& Suresh(2022) SAP2000 Pylonheightand inclination

6 Chenetal. (2022) MIDASCivil Variabletowergeometry

7 Zhangetal. (2022) FEAnalysis

Tower-heightvariation

8 Kimetal. (2023) SAP2000 Dynamiccharacteristics

9 Wangetal. (2023) Genetic Algorithm+FEM Toweroptimization

10 Fernandesetal. (2023) Numerical Optimization

Cable-stayedbridgecost optimization

11 Lietal.(2024) CFD+FEM Aerodynamicstability

12 Ahmedetal. (2024) NonlinearFEM Seismicassessment

13 Gaoetal. (2024) MIDASCivil Long-spanbridge response

14 Luoetal. (2025) FEM Dual-pylonbridge behaviour

15 Liuetal.(2025) Response SurfaceMethod

Cableforceoptimization

16 Zhouetal. Performance- Variablepylonheights

Pylonshapesignificantly affectsdeckdisplacement andcableforces

Dynamiccharacteristics dependonpylongeometry

Pylonheight variationnot investigated

Limitedstudyon towerheight optimization

Optimizedpylonshape improvesstiffness Nocomparisonof varyingpylonheights

Bridgeresponsestrongly influencedbytower configuration

Pylonheighteffect notisolated

Increaseintowerheight reducedcablestressesbut increasedflexibility Limitedrangeof heightsstudied

Tallertowersimproveload distribution

Height-to-spanratioaffects structuralefficiency

Naturalfrequencies decreasewithincreasing towerheight

Optimumtower dimensionsreduce materialusage

Parametricanalysis notcomprehensive

Needvalidationusing commercialsoftware

Staticbehaviournot investigated

Practicaldesign limitationsignored

Optimizedtower dimensionsimprove economy NoSTAAD.Pro-based analysis

Tallertowersaffectwindinducedvibrations Staticstructural responsenotstudied

Towerheightinfluences seismicdemand

Structuralresponse sensitivetosupportheight

Unequaltower configurationsaffect stiffness

Towergeometryimpacts cable-forcedistribution

Serviceabilityimproved

Limited considerationofcable forces

Nosystematic parametricstudy

Focusedondualpylonsystemsonly

Pylonheightnot primaryparameter

Requiresvalidation

Sr. No.

Volume: 13 Issue: 06 | Jun 2026 www.irjet net

Author(s) & Year Software

-0072

Research Gap (2025) BasedDesign withoptimizedtower height onstandardbridge models

17 Sapkota& Montoya (2026) Optimization Algorithms

18 Jiao&Peng (2026) Analytical& NumericalStudy Cablesaddlelayout

effects notisolated

Pylondeformationaffects cablealignment Heightvariationnot studied

19 Kumaretal. (2026) Numerical Analysis Pylonheightandcable arrangement Combinedeffectinfluences deckdisplacement

20 ProposedStudy STAAD.Pro

PylonHeights(60m,80 m,100m,120m)

1.4 Suggested Parameters for the STAAD.Pro Study

Evaluationofdisplacement, bendingmoment,axial force,cableforce,and supportreactions

Limitedpractical design recommendations

Addressesgapby systematically studyingpylon-height influenceusing STAAD.Pro

1.5 Comparison between Output Parameters

Sr.

1.6 Research Gap Analysis

Sr.

&Singh 2021

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 13 Issue: 06 | Jun 2026 www.irjet net p-ISSN: 2395-0072

3 Fawzyetal. 2022 Seismicbehaviour

4 Mehaboob& Suresh 2022 Heightandinclinationeffects

5 Kimetal. 2023 Dynamiccharacteristics

6 Lietal. 2024 Windeffects

Heightvariationnotisolated

Limitedheightrange

Staticresponseignored

NoSTAAD.Provalidation

7 Liuetal. 2025 Cableforceoptimization Towerheightnotprimaryparameter

8 Sapkotaetal. 2026 Structuraloptimization Practicalbridgemodelsnotconsidered

Identified Research Gap – The studies conducted in the past focused mainly on the pylon shape, cable arrangement, seismic response, wind response, and cable force optimization. But, very few studies examine the effect of various pylon heightsontheperformanceofthestructures.TherearenotmanystudiesthathaveadoptedSTAAD.Proisforthedetailed parametricanalysis.Comparative analysisof the displacement, bendingmoment, shearforce,support reaction andcable forcefordifferentpylonheightsisstillincomplete.Therefore,thepresentstudyisaimedattestingthestructuralbehavior ofacable-stayedbridgewithdifferentpylonheightswithallotherparametersfixed.

1.7 Design Codes Used

Indiancodesusedforthedesignandanalysisofthecable-stayedbridgewithdifferentpylonheightsaresummarisedin Table6.

Sr. No.

Design Aspect

Code(s) Used

1 DeadLoad IS875Part1:1987

2 LiveLoad IRC6:2017

3 WindLoad IS875Part3:2015

4 SeismicLoad IS1893Part1:2016

5 ConcreteDesign IS456:2000

6 BridgeLoading IRC112:2020

7 SteelDesign IS800:2007

8 PrestressedComponents IRC18:2000

1.8 Bridge Model Details

1.8.1 Parametric Study Models

Onlythepylonheightsarevariedbetweenmodels,aslistedinTable7.

1.8.2 Validation Study

Beforeperformingtheparametricstudy,theSTAAD.Promodelwasvalidatedagainstpublishedliterature.

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 13 Issue: 06 | Jun 2026 www.irjet net p-ISSN: 2395-0072

ValidationStatement:Thedifferencebetweenthenumericalmodelandpublishedresultsisbelow5%,indicatingthatthe STAAD.Promodelissufficientlyaccurateforfurtherparametricinvestigations.

1.9 Result Tables Maximum

1.9.1 Quantitative Discussion

The deflection at the maximum point of the deck was decreased by 420 mm to 255 mm with the increasing height of pylon from 60 m to 120 m which is equal to (420−255)/420×100=39.3%.Thismeansthatthetaller thepylonsthegreatertheverticalstiffnessandsupportof thedeck.

Effect on Bending Moment: The bending moment decreasedfrom32,500kN-mto23,250kN-m,areduction of(32500−23250)/32500×100=28.46%.Thisisbecause the taller the pylons, the more efficient the load transfer viathestaycables.

Effect on Shear Force: The shear force decreases by around 14% which indicates that as the height of the tower increased the load distribution across bridge deck wasimproved.

Effect on the Cable Force: The cable force dropped from 3650 kN to 3160 kN, which is 13.42%, suggesting better evendistributionofcableforcesintallerpylonsystems. The effect on Axial Force: The axial force in the pylons increasedfrom25,200kNto32,900kN,whichisa30.55%

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 13 Issue: 06 | Jun 2026 www.irjet net p-ISSN: 2395-0072

increase. This is because the compression loadings are higherinthestaycablesfortallerpylons.

Effect on Natural Frequency:From 0.78 Hz to 0.59 Hz, a decrease of 24.36% – which makes the bridge more flexibledynamically,asthenumberofpylonsincreases.

1.9.2 Bridge Configuration

The proposed bridge has a total length of 1400 m and consistsofthefollowingcomponents:

 MainSpan:1400m

 SideSpan1:700m

 SideSpan2:700m

 DeckWidth:30m

 PylonHeight:180m

 CableArrangement:FanType

 DeckMaterial:PrestressedConcrete

 PylonMaterial:ReinforcedConcrete

 StayCableMaterial:High-StrengthSteel

The bridge deck is supported by multiple stay cables connected to pylons located on either side of the main span. The stay cables are arranged symmetrically to ensurebalancedloadtransfer.

2. METHODOLOGY

2.1

Data Required for Design

The first stage involved collecting geometric and material properties required for modelling the bridge. Standard bridge design codes and engineering specifications were referred to for selecting dimensions, material strengths, andloadingparameters.

2.2

Material Properties

Concrete – Grade: M50; Density: 25 kN/m³; Modulus of Elasticity:35GPa.

Structural Steel – Yield Strength: 415 MPa; Density: 78.5 kN/m³;ModulusofElasticity:200GPa. Stay Cables – Ultimate Strength: 1770 MPa; Elastic Modulus:195GPa.

2.3 Modelling in STAAD.Pro

A three-dimensional finite element model of the bridge was created in STAAD.Pro. The modelling process involved defining node coordinates, creating beam elements for the deck and pylons, modelling stay cables using tension-only members, assigning material properties, defining support conditions, and applying loads and load combinations. The bridge deck was

discretized into multiple beam elements to capture accuratestructuralbehaviour.

2.3.1 Load Calculations

Dead loads: These are the weights of structural elements like deck slab, girders, pylons, stay cables and wearing course. The self-weight was automatically calculated by STAAD.Probasedonpropertiesassignedtomaterial.

Liveload:Vehicularloadingwastakenintoaccountbased on standard bridge loading specifications which includes lane load and concentrated vehicle load. The following load positions were chosen to create maximum bending momentsanddeflections:impactfactorandliveload.

Wind Load: Lateral loading due to wind on the deck, pylons and stay cables. The wind pressure was calculated fromthedesignwindspeedandterrain.

Seismic Load: Earthquake forces were computed by the equivalent static approach. The seismic zone factor, importance factor, response reduction factor and soil conditions are some of the factors used for parameters Both longitudinal and transverse seismic loadings were applied.

2.4 Load Combinations

Several load combinations were considered: DL+LL, DL+WL, DL+EQ, DL+LL+WL, DL+LL+EQ, and DL+LL+WL+EQ. These combinations were analyzed to identifycriticalstructuralresponses.

2.5 Analysis Procedure

The finite element analysis was performed using STAAD.Pro. The following outputs were obtained: axial forces in cables, bending moments in deck, shear forces, deckdisplacements,pylonstresses,andsupportreactions. The software solved the global stiffness matrix and calculatedinternalforcesforeachloadingcondition.

2.6 Results and Discussion

Deck Deflection: The maximum vertical deflection occurredatthecentreofthemainspan,withanobserved maximum deflection of approximately 1.25 m under combined loading. This value remained within acceptable serviceabilitylimitsforlong-spanbridges.Thestaycables effectively reduced deck sagging by transferring loads directlytothepylons.

Cable Forces: Cable tension varied according to location, with higher tension observed near the pylons and lower tensiontowardthecentrespan.Themaximumcableforce

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 13 Issue: 06 | Jun 2026 www.irjet net p-ISSN: 2395-0072

was approximately 28,000 kN. The fan-type arrangement ensured efficient load distribution and minimized deck bendingmoments.

Bending Moments in Deck: The maximum positive moment occurred at mid-span, while negative moments developed near the pylon connections, with approximate values of 450,000 kN-m (positive) and 380,000 kN-m (negative). These values were significantly lower than those expected in conventional girder bridges of similar spanlength.

Pylon Behaviour: The pylons experienced combined compression and bending, with a maximum compressive stress of approximately 18 MPa and a maximum lateral displacement of approximately 0.45 m. The pylon dimensions were found adequate to resist the applied loads.

Wind Load Effects: Wind loading produced noticeable lateral displacementofthedeck andpylons.However,the bridge maintained sufficient stiffness due to high cable pretension, adequate pylon rigidity, and balanced cable arrangement; no instability was observed under design windconditions.

Seismic Performance: The seismic analysis indicated acceptable structural behaviour, with moderate deck acceleration, controlled pylon displacement, and no excessive stress concentrations. The bridge demonstrated adequate earthquake resistance due to its flexible cablesupportedsystem.

2.7 Advantages of Cable-Stayed Bridges

 Abilitytospanlongdistances.

 Reducedmaterialconsumption.

 Improvedstructuralefficiency.

 Attractivearchitecturalappearance.

 Betterstiffnesscomparedtosuspensionbridges.

 Lowermaintenancerequirements.

 Fasterconstructionmethods.

Theseadvantagescontributetotheincreasingadoptionof cable-stayedbridgesworldwide.

2.8 Role of STAAD.Pro in Bridge Analysis

STAAD.Pro proved to be an effective tool for modelling and analyzing complex bridge systems. Key benefits include three-dimensional modelling capability, accurate finite element analysis, efficient load application, automatic load combinations, detailed force and displacement output, and a user-friendly interface. The software enabled efficient evaluation of structural performanceundermultipleloadingscenarios.

2.9 Limitations of the Study

 Nonlinearcablebehaviourwassimplified.

 Constructionstageanalysiswasnotincluded.

 Aerodynamiceffectswerenotstudiedindetail.

 Fatigueanalysisofstaycableswasnotperformed.

 Soil-structureinteractioneffectswereneglected.

Future studies may address these aspects for more comprehensiveanalysis.

2.10 Future Scope

Futureresearchmayincludedynamicwindanalysis,timehistory seismic analysis, cable fatigue assessment, construction sequence simulation, optimization of cable arrangements, and the use of advanced materials such as carbon fibre cables. Such studies can further improve the efficiencyandsafetyoflong-spancable-stayedbridges.

3. CONCLUSIONS

Deck displacementissignificantlydecreasedastheheight of the pylons is increased. The higher pylons reduce bending moments and shear forces in the deck, and the higher the pylons, the greater the efficiency of cable force distribution. As the tower gets higher, the axial compression in the pylons also increases, and the natural frequencies decrease with increasing height, meaning the tower would be more flexible. After 100 m, the improvementsindeflection arerelativelysmall compared totheincreaseinpylonforcesandconstructioncosts;the 100 m pylon model offers the best compromise between stiffness and the efficiency of the structure. Hence, the optimum solution for the selected bridge configuration is suggested to be a pylon height-to-main span ratio of around0.5.

ACKNOWLEDGEMENT

The authors wish to thank the Department of Civil Engineering, CSMSS Chh. Shahu College of Engineering, Chhatrapati Sambhajinagar, for providing the necessary supportandresourcesforcarryingoutthisresearchwork.

REFERENCES

[1] Sharry, T., Guan, H., Nguyen, A., et al. (2022), “A review of finite element modelling and model updating techniques for cable-stayed bridges,” covering FE modelling approaches and the role of structural health monitoring in calibrating bridge models.

[2] Ma, Y., Song, C., Wang, Z., et al. (2024), “Advanced optimization techniques for cable-stayed bridge

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 13 Issue: 06 | Jun 2026 www.irjet net p-ISSN: 2395-0072

design integrating finite element analysis with surrogatemodelsandintelligentalgorithms.”

[3] Fawzy, A.M., El-Kashif, K.F., Abdalla, H.A. (2022), “Influence of geometric parameters on the seismic performanceofcable-stayedbridges.”

[4] Mehaboob, A., Suresh, A. (2022), “Influence of pylon height and inclination on the nonlinear dynamic behaviourofcable-stayedbridges.”

[5] Ouyang,P.,Shen,Q.,Xie,X.,Zhu,W.(2023),“Aneural network-based framework for cable force identification and finite element model optimization ofcable-stayedbridges.”

[6] Sun, L., Chen, L., Huang, H. (2022), “Review of stay cable vibration mechanisms and mitigation strategies.”

[7] Martins, A.M.B., Simões, L.M.C., Negrão, J.H.O. (2020), “Survey of optimization methods applied to cablestayedbridges.”

[8] Fernandes, G., Lourenço, N., Correia, J. (2023), “Reducing the cost of cable-stayed bridges using the CMA-ESoptimizationalgorithm.”

[9] Li, W., Huang, Q., Chen, S. (2024), “An exact tension fieldfiniteelementformulationforcablestructures.”

[10] Zhang,W.,etal.(2022),“Multi-objectiveoptimization ofcable-supportedstructures.”