BORANG PENGESAHAN STATUS TESIS REPAIR AND STRENGTHENING METHODS FOR BRIDGE SUPPORTS SESI PENGAJIAN : 2006/2007

Transcription

1 PSZ 19:16(Pind.l /97) UNIVERSITI TEKNOLOGI MALAYSIA BORANG PENGESAHAN STATUS TESIS JUDUL : REPAIR AND STRENGTHENING METHODS FOR BRIDGE SUPPORTS SESI PENGAJIAN : 2006/2007 Saya HANIZAH BINTI ARGADAN (HURUF BESAR) mengaku membenarkan tesis (PSMISatjana/Dekter Falsafah)* ini disimpan di Perpustakaan Universiti Teknologi Malaysia dengan syarat-syarat kegunaannya seperti berikut : 1. Tesis adalah hak milik Universiti Teknologi Malaysia. 2. Perpustakaan Universiti Teknologi Malaysia dibenarkan membuat salinan untuk tujuan pengajian sahaja. 3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara institusi pengajian tinggi 4. **Sila tandakan (,/ ) D D SULIT TERHAD o TIDAK TERHAD tjl~ (TAND ATANGAN PENULIS) (Mengandungi maklumat yang berdatjah keselamatan atau kepentingan Malaysia seperti yang termaktub di dalam AKT A RAHSIA RASMI 1972) (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasilbadan dimana penyelidikan dijalankan) Alamat Tetap: NO.51OBLOK A GUGUSAN MELATI JALAN CAMAR 4/5 SEKSYEN 4 KOTADAMANSARA PETALING JAYA. SELANGOR Tarikh: 0"5 ~ ~4. PROF. DR. AZLAN BIN ABD. RAHMAN Nama Penyelia Tarikh : CATATAN: * Potong yang tidak berkenaan. ** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasalorganisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT atau TERHAD.. Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Sarjana secara penyelidikan, atau disertasi bagi pengajian secara kerja kursus dan penyelidikan, atau Laporan Projek Satjana Muda (PSM).

2 "I hereby declare that I have read this thesis and in my opinion this thesis is sufficient in terms of scope and quality for the award of the degree of Master of Engineering (Civil-Structure)" Signature Name of Supervisor Date

3 11 I declare that this thesis entitled "Repair and Strengthening Methods for Bridge Supports" is the result of my own research except as cited in the references. The thesis has not been accepted for any degree and is not concurrently submitted in candidature of any other degree. Signature Name Date HANIZAH BINTI ARGADAN O~ \'(\e{ ~1"

4 iv ACKNOWLEDGEMENT I wish to express my gratitude to those who contributes in the preparation and completion of this project dissertation especially to: Government of Malaysia for providing the financial support during the course of this work; My supervisor, Prof. Dr. Azlan b. Abdul Rahman for all the useful comments and suggestions for the completion of this project Ir. Abdul Hadi Jusoh, Pn. Sherliza Zaini Sooria and Mr. Lee Choon Shiang, form Jabatan Kerja Raya for providing the information and access to the project site; My superior, Ir. Mohd Noor Azudin b. Mansor from Jabatan Kerja Raya for his understanding during the whole duration of my study and for his invaluable assistance in the preparation of this dissertation; Noraidah Yahya, for her kind co-operation and full encouragement in entire period of my study and for her ideas in the preparation of this dissertation; Last but not least, to my beloved family for their pray, support and patience.

5 To my beloved parents iii

6 v ABSTRACT This project dissertation paper is a study on the repair and strengthening method for the support of a flyover affected by structural cracks. The study focuses on the techniques used to structurally repair or strengthen the concrete bridge piers of the selected case study involving the combination of external pre-stressing and composite method. Factor and requirement for repair and strengthening of the bridge supports have been reviewed whereby the technical aspects with respect to structural strength are studied. A hypothetical detail of bridge support has been created and investigated to study the effect on the flexural capacity of concrete section when pretensioning force imposed the CFRP strip prior to the adhesion of the plate onto the concrete bridge support. A general flow of repair and strengthening of concrete bridge support has been developed based on the analysis of the case study and results of the section analysis of the hypothetical detail. It is found that the choice of repair and strengthening method of bridge supports required a comprehensive structural investigation, careful design and construction. Data of the existing structure and its material properties, as well as the innovative approach of the construction technique are important factors for a successful implementation of the repair / strengthening method. In this particular case study, the repair and strengthening scheme which utilized a combination of external pre-stressing and composite system has been successfully applied to the bridge supports. Continuous monitoring and maintenance are required to ensure that the repair is effective in providing the solution to the structural problem.

7 vi ABSTRAK Disertasi ini adalah untuk mengkaji teknik pembaikan dan penguatan sokong jambatan yang mengalami keretakan. Kajian ini dijalankan dengan memilih kajian kes dan memfokuskan terhadap teknik pembaikan dan penguatan sokong jambatan secara struktur. Faktor-faktor dan keperluan untuk membaiki dan menguatkan sokong jambatan telah dikaji dengan memberikan tumpuan kepada aspek kekuatan struktur. Satu butiran hipotesis sokong telah dibentuk untuk mengkaji kesan daya pra-tegangan terhadap kekuatan lenturan muktamad keratan konkrit apabila daya prategangan dikenakan kepada kepingan CFRP sebelum kepingan tersebut dilekatkan ke permukaan sokong konkrit. Satu carta aliran umum berkenaan tatacara pembaikan dan penguatan sokong jambatan konkrit telah dirangka berdasarkan kajian kes dan hasil analisis keratan butiran hipotesis tadi. Adalah didapati bahawa pemilihan cara pembaikan dan penguatan memerlukan penyiasatan struktur yang komprehensif serta rekabentuk dan pembinaan yang teliti. Data untuk struktur sediada dan sifat bahan di samping pendekatan inovatif dalam teknik pembinaan adalah faktor-faktor penting untuk perlaksanaan kaedah pembaikan dan penguatan yang berjaya. Dalam kajian kes ini, skim pembaikan dan penguatan yang mengunakan gabungan pra-tegasan luaran dan sistem komposit telah didapati berjaya diaplikasikan untuk sokong jambatan. Pemantauan dan penyelenggaraan yang berterusan terhadap kaedah pembaikan tersebut adalah diperlukan untuk memastikan bahawa ianya berkesan dalam penyelesaian sesuatu masalah struktur.

8 vii TABLE OF CONTENT CHAPTER TITLE PAGE DECLARATION DEDICATION ACKNOWLEDGEMENT ABSTRACT ABSTRAK TABLE OF CONTENT LIST OF TABLES LIST OF FIGURES LIST OF SYMBOLS LIST OF APPENDICES ii iii iv v vi vii x xi xiv xvii 1 INTRODUCTION Significance of Study Objective of Study 3 2 LITERATURE REVIEW Bridge Support Structural Concrete repair Concrete Cracks Crack Repair Method and Material Structural Strengthening Steel-base Strengthening Material FRP-base Strengthening Material 15

9 viii 2.4 External pre-stressing Strengthening Flexural Section Analysis CFRP Strip Flexural Strengthening Level of Post Tensioning Pre-stressed or Post-Tensioned 27 CFRP Strips Force Transfer from Strip to 28 Dead and Live Anchors Force Transfer from Dead or 30 Live Anchor to Concrete 3 METHODOLOGY Hypothetical Bridge Support Detail Detail of Existing Section Detail of Strengthen Section Ultimate Section Capacity Existing Section Strengthen Section Case Study Selection General Flow of Bridge Support 45 Repair and Strengthening 4 ANALYSIS AND DISCUSSION Pier Head Existing Section Capacity Flexural Capacity in Longitudinal Direction Transverse Capacity of Existing Section Strengthen Section Capacity Flexural Capacity in Longitudinal Direction Transverse Capacity of Strengthen Section 50

10 ix 5 CASE STUDY: Repair and Strengthening of Middle Ring Road 52 (MRR2) Package Introduction Description of the Structure Background of the Problem Description of Repair and Strengthening Work Detail of Repair and Strengthening Stages of Repair and Strengthening Conclusion 63 6 General Guideline for Repair and Strengthening Concrete 64 Bridge Support 6.1 Introduction Existing Bridge Support Assessment Conceptual Stage Detail Analysis and Design Construction Stage Service Stage Flow Chart of Repair and Strengthening Guideline Process 68 7 CONCLUSIONS AND RECOMMENDATIONS Conclusions Recommendations 71 REFERENCES Appendix A-B:

11 x LIST OF TABLES TABLE NO TITLE PAGE 2.1 Mechanical / physical properties of adhesive - Sikadur Mechanical / physical properties of epoxy resin Sikadur 31LP Pre-stressing bar properties, (Dwidag System International) Properties for carbon fibres (Sika CarboDur Plate) Values of partial factors for FRP material Reinforcement area for existing pier Crossbeam Material properties for existing section Technical properties of CFRP strip for strengthening Technical properties of Dywidag Post Tensioning system using bar 36

12 xi LIST OF FIGURES FIGURE NO TITLE PAGE 2.1 Stress-strain curves, (Collins and Mitchell 1991) Properties of different fibre and KsSteel. After ACI Comitee 440 and Dejke (2000) Stress-Strain diagram for Sika CarboDur Stress Strain Diagram for external pre-stressing Failure mechanism of beams strengthened with bonded CFRP strips with respect to the level of post-tensioning Shear stress distribution inside the final anchorage induced by rear-loading of prestressing force V (τv), front-loading of additional forces Z (τ Z) and its superposition (τv+ Z) Transfer of pre-stressing force from anchor to concrete Existing bridge support reinforcement and plan view Strengthen bridge support and plan view Stress-strain diagram for the existing section 38

13 xii 3.4 Stress-strain diagram for the strengthen section over beam depth Schematic presentation for Length vs. Moment of Resistance Location map of Middle Ring Road 2 Package Location map of Middle Ring Road 2 Package 11 (Close View) Sketch of Location map for Middle Ring Road 2 Package Stages of repair and strengthening Predicted stress condition at service Predicted stress condition at the application of external pre-stressing force form the steel tie frame (Prior to the closure of cracks) Predicted stress condition at the application of external pre-stressing force form the steel tie frame (After the closure of cracks) Predicted stress condition at the application of external pre-stressing force form the steel tie frame and the CFRP Plate Predicted stress condition after the released of external pre-stressing force in the steel tie frame Predicted stress condition at service after strengthening process (With assumption class 3 pre-stressing concrete member is obtained) 63

14 xiii 6.1 Schematic representation of repair and strengthening process for bridge support with strength failure 69

15 xiv LIST OF SYMBOLS a - Shear span or distance from beam support to the nearest loading point A c - Gross section area of concrete section A c - Area of crack concrete section A ps - Area of external tendon A s, A si - Area of internal steel reinforcement b c, b - Width of beam c, x, - Neutral axis d frp - Depth of FRP f c - Cylinder compressive strength of concrete f cu - Concrete ultimate strength (Concrete grade) f pe - Effective tendon pre-stress f ps, - Stress in external tendon f si, σ si - Stress in internal steel f y - Ultimate strength for steel (Steel yield stress) F c - Compression strut F t - Tension tie F s - Pre-stress force tie d - Effective depth of un-strengthened section (with respect to steel) d pso,d u - Effective tendon depth at ultimate E frp - Modulus of elasticity for FRP e - Eccentricity of steel tie frame e - Eccentricity of CFRP strip E st - Modulus of elasticity for steel h - Overall beam height k 1 - The mean stress factor

16 xv k 2 - Concrete compressive force centroid factor k s - Second order effect L - Beam span L u - Horizontal distance between end of the pre-stress tensioning strands M s - Service moment during construction M s - Additional service moment after the release of steel tie frame M u - Ultimate Flexural strength of strengthen beam M un - Ultimate flexural strength of un-strengthen beam P i - Initial pre-stressing force in CFRP P st - Portion of pre-stressing force from the steel tie frame P rup - CFRP rupture strength P st - Total effective pre-stressing force from the steel tie frame x cr - The critical depth of neutral axis of strengthened section x 1, x 2 - The depth of neutral axis of the section which takes into consideration the curve shape of pier crossbeam T - The applied horizontal load along with V - Vertical force Z b - Section modulus for bottom fibre of un-crack concrete section Z t - Section modulus for bottom fibre of un-crack concrete section Z b - Section modulus for bottom fibre of crack concrete section Z t - Section modulus for top fibre of crack concrete section Z cb - Section modulus for bottom fibre of composite section Z ct - Section modulus for bottom fibre of composite concrete section z - Lever arm of concrete section β - Estimated loses in pre-stressing of CFRP β - Compression stress block depth factor to ACI Building Code (ACI Committee 1999) ε co - The compressive strain of unconfined concrete, at the peak stress of concrete ε cf - Strain in concrete ε cu - Ultimate strain of concrete ε frp - Strain in FRP ε frp-rup - Strain in FRP at rupture for composite section ε frp-ini - Initial strain in FRP

17 xvi ε frp-max - Maximum strain in FRP ε si - The strain in the steel γ c - Partial safety factor material (concrete) safety factor γ mwe - Partial safety factor for the modulus of the fibres in tension and compression γ mwy - Partial safety factor for the compressive strength of the fibres γ mwε Partial safety factor for the strain capacity of the fibres in tension and compression and the strain at failure in the fibres in compression. ρ frp - The ratio of CFRP ρ frp-cr - The critical ratio of CFRP σ c - Stress in concrete before strengthening σ' c - Stress in concrete after strengthening σ frp - Stress in FRP ρ si - The ratio of internal steel Ω u - Bond reduction coefficient at the ultimate limit state

18 xvii LIST OF APPENDICES APPENDIX TITLE PAGE A Pictures on Repair and Strengthening Works of Middle Ring Road, (MRR2) Package B Result for Hypothetical Bridge Support Analysis

19 CHAPTER 1 INTRODUCTION Bridge generally needs structural modification when there is insufficiency strength caused by design inadequacies, incorrect detailing, improper construction or loss of stiffness due to material deterioration. Sometimes combination of these factors exists. The most common methods of structural modification are in the form of repairing, stiffening or strengthening the existing structure. Strengthening and stiffening are also necessary due to increase in live load and design code revision. Failure in serviceability limit state attracts concern from the public. The safety of public facilities and infrastructure always become an issue when there is apparent concrete crack, excessive deflection and unacceptable vibration. Occurrence of this symptom is also the warning to the ultimate safety of a structure. As for bridge, these symptoms need particular repair or strengthening method to reinstate the bridge to it original service level. Bridge support; the pier, pier cap and abutment, are considerably important to be maintained, repaired and strengthened where necessary. Damage of bridge support that is not repaired or strengthened properly would affect the bridge integrity as a whole.

20 2 When reconstruction or demolition is not an option, innovation in method of structural repair or strengthening should be the solution. However, repair and strengthening method need to consider a suitable theoretical background for a successful scheme. Cause of failure, existing condition of structure, the material compatibility and constructability are all equally important in short listing the possible solutions for repair or strengthening a structure. For concrete bridge structure whether by attaching the repair material directly onto the concrete surface to form composite, crack grouting or reinstating the structure via external prestressing, must undergo proper evaluation and selection. Recent development in advanced civil engineering material provides variety of options for repair technique to suit the required condition of a deficient structure. Furthermore, the cost factor must be taken into consideration and in most cases this is the major determining factor. 1.1 Significance of Study The study provides more evidence on the applicability of the existing theoretical background for repair and strengthening of bridge superstructure. Compiling the state-of-the-art technology in repair, stiffening and strengthening of bridge support provides a possibility for improvement of the existing engineering judgements or assumption made in designing the bridge repair and strengthening. If the technical aspects in state-of-the-art-technique such as safety factor, material mechanical properties, and static mechanic involves as well as the suitable assumptions made in bridge support modification work is continuously collected, a general guidelines for structural repair, stiffening and strengthening of bridge support is possible. Furthermore, through a case study, the necessary measure or good engineering practices adopted during the process of modification of bridge support can be documented. This is important to identify what are the do s and don ts during

21 3 the repair and strengthening work for an acceptable level of performance and durability of the repair material and the modified bridge support as a whole. 2.1 Objective of Study The objective of this case study is to review the factors and requirements for strengthening of concrete bridge support. The study will also investigate the technical aspects of strengthening techniques for concrete bridge support through a selected case study.