PARASITIC MOMENT EFFECT FOR THE THREE SPANS CONTINUOUS PRESTRESSED CONCRETE BRIDGE SITI SARAH SALIM

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1 PARASITIC MOMENT EFFECT FOR THE THREE SPANS CONTINUOUS PRESTRESSED CONCRETE BRIDGE SITI SARAH SALIM A project report submitted in partial fulfillment of the requirements for the award of the degree of Master of Engineering (Civil-Structure) Faculty of Civil Engineering Universiti Teknologi Malaysia JANUARY 2014

2 To my beloved parents and family iii

3 iv ACKNOWLEDGEMENT I wish to express my sincere appreciation to my project supervisor, Assoc. Prof. Dr. Arizu b. Sulaiman, for his encouragement, guidance, advices and critics. Without his continued support and interest, this project would not have been the same as presented here. I also would like to give my special thanks to my Director, Mr Zainal, my supervisor, Mr S. Baskaran and fellow officemate at SMEC (M) Sdn. Bhd. for providing assistance and support. They have contributed towards my understanding, thoughts and useful information for finishing this project. My fellow friends also are recognized for their support and thanks for their direct and indirect involvement. My sincere appreciation also extends to others who have provided assistance at various occasions. Lastly but not least, I am grateful to my dearest family for their constant encouragement apart from providing their love and moral support. Words cannot express my gratitude. Thank you for everything.

4 v ABSTRACT In the analysis of a continuous prestressed concrete bridge, Dead Load (selfweight of bridge), Superimposed Dead Load (Surfacing and Parapet) and Live Load (HA, HB or combined) are considered as major loadings for bridge structure. However, there are other factors that should be considered in the analysis such as Parasitic Moment. The effect from parasitic moment can contribute a significant value in designing a continuous prestressed concrete bridge. This study focuses on the effect of parasitic moment for a three spans continuous prestressed concrete bridge. An analysis of a continuous bridge using Staad Pro software is carried out to determine the parasitic moments of the bridge. The parasitic moments obtained from Staad Pro are slightly higher compared to the parasitic moments from Adapt software with a difference less than 10 percent. The parasitic moment is sagging throughout the whole bridge and the maximum moment is at the second span. A positive value of the parasitic moment will increase the value of the sagging moment at the mid span but will reduce the hogging moment at the support. For the case when parasitic moment effect is considered, the stress at bottom of beam is lower than the stress at top of beam. Whereas, the situation is reverse for the case when parasitic moment effect is not considered. If the same dead load, superimposed dead load and live load proportions are to be considered, the resultant stress at bottom of the beam will exceed the tensile stress limit when the parasitic moment proportion is more than 55% of the total moment. Hence, the parasitic moment effect should be considered in the design of a continuous prestressed concrete bridge especially when it comes to the value of moment at the mid span of the bridge.

5 vi ABSTRAK Dalam analisis jambatan konkrit prategasan selanjar, beban mati (berat sendiri jambatan), beban mati kenaan (permukaan dan dinding jambatan) dan beban hidup (HA, HB atau gabungan) dianggap beban utama bagi struktur jambatan. Walau bagaimanapun, terdapat factor-faktor lain yang perlu dipertimbangkan dalam analisis seperti momen parasitik. Kesan daripada momen parasitik boleh menyumbang nilai yang signifikan dalam mereka bentuk sesebuah jambatan konkrit prategasan selanjar. Kajian ini menumpukan kepada kesan momen parasitik terhadap jambatan konkrit prategasan selanjar yang mempunyai tiga rentang. Analisis jambatan selanjar menggunakan perisian Staad Pro digunakan untuk menentukan momen parasitik jambatan tersebut. Momen parasitik yang diperolehi daripada Staad Pro adalah lebih tinggi berbanding momen parasitik daripada analisis perisian Adapt, dengan perbezaan kurang daripada 10 peratus. Momen parasitik adalah melendut pada keseluruhan jambatan dan momen maksimum adalah pada rentang kedua. Momen parasitik positif akan meningkatkan momen melendut di tengah rentang dan mengurangkan momen meleding di penyokong. Apabila kesan momen parasitik diambil kira, tekanan di bahagian bawah rasuk adalah lebih rendah daripada tekanan di bahagian atas rasuk. Manakala, keadaan adalah sebaliknya bagi kes apabila momen parasitik tidak dipertimbangkan. Jika bahagian beban mati, beban mati kenaan dan beban hidup yang sama dipertimbangkan, tekanan di bahagian bawah rasuk akan melebihi had tegasan tegangan apabila momen parasitik melebihi 55 peratus daripada jumlah momen. Oleh itu, kesan momen parasitik perlu dipertimbangkan dalam rekabentuk jambatan konkrit pretegasan selanjar terutama jika melibatkan nilai momen di pertengahan rentang jambatan.

6 vii TABLE OF CONTENTS CHAPTER TITLE PAGE DECLARATION ii DEDICATION iii ACKNOWLEDGEMENTS iv ABSTRACT v ABSTRAK vi TABLE OF CONTENTS vii LIST OF TABLES x LIST OF FIGURES xi LIST OF SYMBOLS LIST OF APPENDICES xvi xvii 1 INTRODUCTION 1.1 General 1.2 Problem Statement 1.3 Aim and Objectives 1.4 Scope of Work 1.5 Significant of Study LITERATURE REVIEW 2.1 General 2.2 Design Loading Dead Load Highway loading according to BD 37/

7 viii Highway loading according to JKR specifications LTAL loading SV loading Other loading 2.3 Stage of Construction 2.4 Continuity of Prestressed Bridge 2.5 Parasitic Moment Primary and secondary prestress effects The nature of prestress parasitic moments Computation method for secondary prestress moments Prestress application in Staad Pro METHODOLOGY 3.1 Dead Load and Applied Loading Analysis 3.2 Designing Prestressed Concrete Beam 3.3 Deriving the Parasitic Moment Creating new file Geometry section General section Perform analysis 3.4 Compare Results from Staad Pro and Adapt Software 3.5 Effect of Parasitic Moment ANALYSIS AND RESULTS 4.1 Introduction 4.2 Analysis of Bridge Due to Applied Loading 4.3 Parasitic Moment 4.4 Effect of Parasitic Moment 4.5 Significant of Parasitic Moment

8 ix 5 CONCLUSIONS AND RECOMMENDATIONS 5.1 Overview 5.2 Conclusions 5.3 Future Recommendations REFERENCES 79 APPENDICES 81

9 x LIST OF TABLES TABLE NO TITLE PAGE 2.1 Type HA uniformly distributed load HA lane factors Type LTAL uniformly distributed load Bending moment and shear force for different applied loadings Parasitic Moment at different positions Total moment for analysis of the bridge The stress check at 0.5L of second span with parasitic effect The stress check at 0.5L of second span without parasitic effect The stress check at 0.5L of the second span with parasitic moment value of 6760 knm 73

10 xi LIST OF FIGURES FIGURE NO TITLE PAGE 2.1 Dimensions of HB vehicle Plan of SV Controlled SV movement geometry Uncontrolled SV movement geometry Stage 1 for three-span continuous prestressed concrete bridge construction Stage 2 for three-span continuous prestressed concrete bridge construction Stage 3 for three-span continuous prestressed concrete bridge construction Stage 4 for three-span continuous prestressed concrete bridge construction Stage 5 for three-span continuous prestressed concrete bridge construction 18

11 xii 2.10 Stage 6 for three-span continuous prestressed concrete bridge construction Multi-strand tendon coupler Prestress bar coupler Prestressed in continuous decks Prestress stresses on section (a) The principal of parasitic moment (b) The principal of parasitic moment continued Grillage model of a three-span continuous prestressed concrete bridge Estimate number of tendons for a bridge The home page of Staad Pro. Software "New" model dialog box "Where do you want to go?" dialog box Members of three span continuous prestressed concrete bridge Line-beam model for three span continuous prestressed concrete bridge The section properties representation in Staad Pro 41

12 xiii 3.9 Section properties of T10 beam Section properties of T10 beam (end block) Section properties of T10 internal beam Section properties of T10 edge beam Section properties of edge diaphram Section properties of stitching and crosshead The pinned support is assign to the model Prestress load dialog box The prestress load assignation Post stress load dialog box The post stress load assignation Load combination dialog box The parasitic moment diagram Parasitic moment value from Adapt software Resultant stress on prestress section Bending moment due to self weight Shear force due to self weight 57

13 xiv 4.3 Bending moment due to parapet load Shear force due to parapet load Bending moment due to internal surfacing Shear force due to internal surfacing Bending moment due to external surfacing Shear force due to external surfacing Bending moment due to live load (HA and HB30) Shear force due to live load (HA and HB30) Parasitic moment from Staad Pro analysis Result of parasitic moment from Adapt software Resultant moment for the three spans continuous bridge Percentage of moment at 0.4L of the first span Percentage of moment at 0.5L of the second span The resultant stress at 0.5L of second span with parasitic effect The resultant stress at 0.5L of second span without parasitic effect 72

14 xv 4.18 The resultant stress at 0.5L of the second span with the parasitic moment value of 6760 knm 73

15 xvi LIST OF SYMBOLS 2-D - Two-dimensional space A, A s - Area of section d - Diameter e, e c - Eccentricity E, E s - Modulus of elasticity f cu - Concrete strength I - Moment of inertia l - Span length M - Bending moment NA - Neutral axis P, P ult - Force w - Load per meter y b - Distance of cable from bottom section Z b, Z t - Section modulus θ - End rotation

16 xvii LIST OF APPENDICES APPENDIX TITLE PAGE A General arrangement of the bridge 82 B Drawing of Cable Layout 83

17 CHAPTER 1 INTRODUCTION 1.1 General Normal practice in bridge design is to combine the longitudinal and transverse designs, different load conditions and long term effects in order to suit the design requirements. However, these criteria are practically analyzed separately. The analysis that commonly used to derive the forces and moments for bridge design is two- or three dimensional finite-element modeling or grillage models. This type of analysis can be applicable for any types of bridge materials as steel, prestressed concrete and many more. Prestressed concrete is frequently chosen as the material for bridge constructions. This is because the development of prestressed concrete bridges has given the bridge engineers increased flexibility in his selection of bridge form and in the construction techniques available. Prestressing in bridgeworks is normally applied as an external force to the concrete by the use of wires, strands or bars, and can greatly increase the

18 2 strength of concrete alone. This can result in longer or slender spans, which improves aesthetics while providing economy in the construction (Hewson, 2003). For prestressed concrete bridge, the prestress effect must be applied within the model as other loads. The principle of prestress design is to make sure that the resulting stress came from primary and secondary effects are within the allowable limit. The stress is generated due to self-weight and loadings from the prestress effect. The secondary moment such as parasitic moment is one of the prestress effects. If the resulting stresses are exceeding the allowable limit, adjustments have to be made to the prestress arrangement. So, it is important to analysis the prestress effects before determining the final bridge design. The stresses inside the prestress structure also undergo short and long term losses such as creep and shrinkage. Since the continuous prestressed concrete bridge generally constructed stage-by-stage, each stage must be analyzed separately to obtain the moments, shears and prestress effects for that stage. The total moment and force distribution at each stage is the combination of the results from the stage and from all the earlier stages. However, the results from previous stages must be modified to consider the long term losses. At the final stage, the analysis results for the completed structure are calculated after all long term losses occurred and these values are used to verify the final design.

19 3 1.2 Problem Statement In analysis of a continuous prestressed concrete bridge, Dead Load (self-weight of bridge), Superimposed Dead Load (Surfacing and Parapet) and Live Load (HA, HB or combined) are considered as major loadings for bridge structure. However, there are other factors that should also be considered in the analysis such as Parasitic Moment. The effect from parasitic moment may contribute a significant value in designing a prestressed concrete bridge. If this effect is neglected, improper design of bridges may be obtained. Furthermore, if the total stresses resulted from the applied loads and this additional effect exceeded the capacity of the bridge, the bridge may fail. 1.3 Aim and Objectives The aim of this study is to study the parasitic moment effect for three-span continuous prestressed concrete bridges. The objectives for this study are: i. To analyze the three-span continuous prestressed concrete bridge due the parasitic moment effect with Staad Pro. ii. To compare the analysis results from Staad Pro. with existing results from Adapt. iii. To determine the effect of parasitic moment for the three-span continuous prestressed bridge. iv. To propose a suitable position for considering the parasitic moment effect that will have some significant in the design of three-span continuous prestressed concrete bridge. v. To determine the limit of parasitic moment's value which will be significant in the design of three-span continuous prestressed concrete bridge.

20 4 1.4 Scope of Work This study only focuses on the Putai Bridge which is a three-span continuous prestressed concrete bridge. The dimensions, section properties and tendons location of the bridge will be shown on Appendix section. The bridge will be modelled in Staad Pro. for different stages. The stages consider will follow the sequences of construction. This model will be analyzed for self weight, superimposed dead load and highway loadings at different stages. Parasitic moment effect will be analyzed using line-beam analysis. The eccentricities and forces of tendons inside the complete prestressed concrete bridge are applied directly to the model. The analysis results from Staad Pro. are compared to the existing results from Adapt to determine the accuracy of the model. The resultant stresses of the prestressed concrete beam is checked against the stress limit using spreadsheet. 1.5 Significant of Study i. The study will shows the method to analyze the parasitic moment effects by using general structural analysis such as Staad Pro. ii. The study will show the effect of parasitic moment for the continuous prestressed concrete bridge. iii. The study will be the basis on whether parasitic moment values will be of some significant in designing continuous prestressed concrete bridge.

21 79 REFERENCES Aalami, B.O. (1998), Hyperstatic (Secondary) Actions in Prestressing and Their Computation, Technical Notes for Professional Engaged in Post-Tensioning Design, December 1998 Benaim, R. (2007), Prestressing for Continuous Beam. The Design of Prestressed Concrete Bridges 6: Bondy, K.B. (2003), Moment Redistribution: Principles and Practice Using ACI , PTI Journal, January 2003 British Design (2001), Loads for Highways Bridge, BD37/01, London: British Standards Institution British Standard Institution (1988), Steel, concrete and composite bridges. General statement. BS , London: British Standards Institution British Standard Institution (2006), Steel, concrete and composite bridges. Specification for loads. BS , London: British Standards Institution British Standard Institution (1990), Steel, concrete and composite bridges. Code of practice for design of concrete bridges. BS , London: British Standards Institution British Standard Institution (2007) Structural Use of Concrete, BS 8110, London: British Standards Institution Burgoyne, C. (2005) Analysis of Continuous Prestressed Concrete Beams Duan L., Chen, K. and Tan, A. (2000), Prestressed Concrete Bridges, Bridge Engineering Handbook. Boca Raton: CRC Press, 2000 Guo, N., Li, H. and Guo, Y. (2011), Research on Secondary Moment of Prestressed Slab- Column Structure, Advanced Materials Research Vols (2011) pp

22 80 Hewson, N.R. (2003), Analysis of Prestressed Concrete Bridges. Prestressed Concrete Bridges: Design and Construction 8: Law, S.S. and Lu, Z.R. (2005), Time domain responses of a prestressed beam and prestress identification, Journal of Sound and Vibration, 288 (2005) Lua, Z.R. and Law, S.S. (2005) Identification of prestress force from measured structural responses, Mechanical Systems and Signal Processing, 20 (2006) pp Marshall, R.B., Cormie, D. and Lavery, M. (2012), Chapter 10: Loading, ICE Manual of Structural Design: Buildings 2012 Institution of Civil Engineers Oh, B.H. and Jeon, S.J. (2002) Limitations and realistic application of equivalent load methods in pre-stressed concrete structures, Magazine of Concrete Research, 2002, 54, No. 3, June, Scollard, C.R. and Bartlett, F.M. (2005), Secondary Prestressing Moments in Rehabilitated Posttensioned Bridges, Journal of Bridge Engineering, : Su, X.K., Nan, G. (2012) Analysis Method of Secondary Moment in Prestressed Plane Structures Applied Mechanics and Materials, Vols (2012) pp Tiruchirapalli, V. and Hindi, R. (2009), Secondary Moments of Continuous Prestressed Concrte Beams Using Closed Form Equation, Structures 2009: Don't Mess with Structural Engineers 2009 ASCE Xiong, X. and Xu, S.X. (2005) Computation of Secondary Moments in Prestressed Concrete Structures, ASCE

PARASITIC MOMENT EFFECT FOR THE THREE SPANS CONTINUOUS PRESTRESSED CONCRETE BRIDGE SITI SARAH SALIM

PARASITIC MOMENT EFFECT FOR THE THREE SPANS CONTINUOUS PRESTRESSED CONCRETE BRIDGE SITI SARAH SALIM A project report submitted in partial fulfillment of the requirements for the award of the degree of