University of London Imperial College of Science 6 Technology
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University Of London Imperial College Of Science 6 Technology Behaviour Of Grouted Dowelled Connections Between Precast Concrete Columns. A thesis submitted for the degree of Doctor of Philosophy of the University of London and for the Diploma of Imperial College. by ATALLAH SHAFIC KUTTAB Concrete Section Department of Civil Engineering 1986 2 ABSTRACT The work described deals with the behaviour of grouted dowelled connection between precast columns in compression and compression combined with flexure. The literature review of precast concrete connections revealed that their efficiency relates directly to their dimensional accuracy, i.e. tolerance, which in turn can only be obtained using correct manufacturing process. A purpose built rig, providing axial and lateral loads, was used for this study. Prototypes of the specimens were made to test the adequacy of the grouting. Detailing of the connection was based on a concrete confinement model developed in this thesis. The column failed away from the connection when subjected to pure axial load, confirming the adequacy of the detailing. In all other tests, the joint was subjected to more severe loading than the remainder of the column and failure occurred at the joint. Shear seemed to have negligible effect on this behaviour . When subjected to flexural stresses, precast specimens behaved similar to monolithic ones up to peak load. Beyond this point, the joint behaved as a hinge leading to a local angular discontinuity within the length of the jointed column. A feature of the work was the use of instrumentation to study this localised behaviour and to isolate the behaviour of the joint from the column as a whole. The sensitivity of the joint performance to errors in construction was examined by varying the joint thickness. This had a number of effects, in addition to reducing confinement, which led to significant reduction in strength with increase in joint thickness . 3 Table of Contents Page Acknowledgement 9 Chapter 1- Introduction. 10 1.1- General. 10 1.2- Objective of the research. 14 1.3- Organization ofthis work. 15 Chapter 2- Review of literature dealing with column-to-column joints. 2.1- Introduction. 16 2.2- Types of column-to-column joint. 18 2.3- Previous research. 4-5 2.3.1- General. 4-5 2.3*2- Tests by Somerville. 4-8 2.3.2.1- Behaviour of mortar joints in compression. 52 2.3.2.2- Influence of percentage reinforcement on mortar joints. 54 2.3*3- Ad hoc tests at Polytechnic of Central London 58 2.4- - Critique of present practices 62 2.4- • 1 — General. 62 2.4.2- Tolerances in the precast industry. 63 2.4*2.1- Historical background. 63 2 .4*2.2- Theoretical analysis of tolerances. 69 2.5- Summary, evaluation and conclusion. 77 4 Chapter 3- A confinement model for detailing concrete structures. 80 3.1- Introduction. 80 3-2- Concrete confinement. 82 3.2.1- Passive confinement. 82 3.2.2- Active confinement. 86 3.3- Passive confinement by rectilinear ties. 89 3•3•1- Introduction. 89 3.3*2- Comparative study of the confinement models. 89 3*3.3- Sheikh & Uzumeri experimental programme. 98 3.3*3.1- Experimental observations. 98 3.3*3.2- Analytical model. 99 3.3*4- Experimental programme by Park et.al. 103 3.3.4*1- Experimental observations. 103 3.3-4*2- Analytical model. 110 3.4- Analytical model of concrete confined by rectilinear steel ties. 112 3.4*1 - Critique of existing models. 112 3.4*2- Proposed analytical model. 113 3*4*3- Two models of confinement. 118 3.4.3.1- The K-N model. 118 3.4*3.2- The A-S model. 118 3.4*4- Application to specimens tested by Sheikh & Uzumeri. 122 3*5- Practical application of the confinement model. 133 3.6- Summary. 136 5 Chapter 4- Description of experiment. 137 4.1- Introduction. 137 4*2- Test rig. 139 4.2.1- Alternatives for the test rig. 139 4.2.2- Description of the test rig. 142 4.2.2.1- Axial load rig. 142 4.2.2.1.1- End blocks. 142 4.2.2.1.2- Accessories. 147 4.2.2.2- Lateral load rig. 148 4.2.3- Eccentricity of the test rig. 156 4»3- Test specimens. 160 4.3.1- Formwork 160 4»3.2- Reinforcement. 160 4-3.3- Concrete mix and casting of specimens. 166 4.3*4- Grouting. 173 4.3.4*1- Introduction. 173 4.3*4*2- Pump. 173 4.3.4*3- Trial mixes of grout. 176 4*3.4*4- Grouting technique. 178 4*3.5- Stacking of grouted specimens. 180 4.4- Instrumentation. 183 4*4*1- Measurements required. 183 4.4*2- Instruments. 183 4«4*3- Calibration. 189 4«5- Test procedure. 190 Acknowledgement. 191 6 Chapter 5- Results of the main test series. 192 5«1- Introduction. 192 5.2- General observations. 196 5.3~ Measurement of angular change across the thickness of the joint. 205 5.3.1- General. 205 5.3.2- Exact Method. 213 5.3-3- Approximate Method. 218 5.3.4- Comparison between both methods. 221 5.4- Other measurements made during testing. 224 5.4*1- Lateral deflections. 224 5.4*2- Deformation of embedded strain gauges. 225 5.5- Effect of shear. 234 5.6- Summary. 235 Chapter 6- Analytical view of behaviour. 236 6.1- Introduction. 236 6.2- Behaviour to peak load. 237 6.2.1- Introduction. 237 6.2.2- Column Theory. 237 6.2.2.1- Assumptions. 237 6.2.2.2- Mathematical formulation. 238 6.2.3- Application to specimens in main test series. 243 6.2.4- Comparison with experimental results. 251 6.2.5- Conclusion. 262 7 6.3- Post peak load behaviour. 271 6.3*1- Introduction. 271 6.3*2- Failure mechanism. 271 6.3*3- Literature review. 272 6.3*4- Analysis of angular change across the joint thickness. 275 6.3*5- Discussion of results and conclusion. 279 6.4- Analysis of the shoe joint. 280 6.4*1- Introduction. 280 6.4*2- Analysis of the various sections. 280 6.4*3- Comparison with experimental results. 284 6.4*4- Discussion of the shoe and grouted joints results. 291 6.5- Summary and conclusions. 295 Chapter 7- Results of tests on the influence of joint thickness. 296 7.1- Introduction. 296 7.2- Tests undertaken. 298 7.3- Presentation and discussion of experimental results. 298 7*4- Summary & conclusions. 315 Chapter 8- Discussion and Conclusions. 319 8.1- Summary and general discussion. 319 8.2- Conclusions. 321 8 List of references. 324 Appendix 1- Chapter 4» 338 (a) Calculation of the amount of ties in the joint region. 338 (b) Calibration of the 200 ton jack. 339 (c) Calibration of the 50 ton jack. 340 Appendix 2- Chapter 5. 341 (a) Estimation of rotation of the precast columns near the joint. 341 (b) Tables of results of the main test series. 345 Appendix 3- Chapter 6. 381 (a) Listing of computer programme for the Column Theory. 381 (b) Input file for the computer programme. 384 9 ACKNOWLEDGEMENT. I wish to acknowledge the considerable help and encouragement given to me by Prof. J.W.Dougill who supervised this work. I also want to thank Dr. J.Bobrowski (Jan Bobrowski & Partners), Dr. M.Kotsovos (Imperial College), and Dr. B. Cranston and Dr. G. Somerville (Cement & Concrete Association) for their valuable comments and advice. My thanks are due too to the staff of the Concrete Laboratory at Imperial College, especially Mr. R. Loveday and Mr. W. Bobinski, without whose help this work would have been impossible, and to Mr. A. Chipling of the photographic section for making all the plates. Also, I am very grateful to the Civil Engineering Department (Concrete Section) for supporting this work. My gratitude must be extended to the British Council and Birzeit University (Israeli- Occupied West Bank) who supported me financially for the duration of this work. Also, I wish to thank all my colleagues at Birzeit University who provided facilities for the writing up of this thesis. Finally, my thanks to many other colleagues and friends who have contributed much, both directly and indirectly, to this thesis. 10 Chapter 1- Introduction. 1.1- General. The technique of precasting parts of a concrete structure in a factory away from the site is one which has evolved slowly. Perhaps this technique, in its crudest form, is represented in masonry structures where bricks are fabricated in a factory and joined on the site. Since World War II - especially during the last three decades- precast concrete has gained considerable publicity, although not always with the right emphasis. Far too many engineers started thinking of precast concrete frames without giving adequate consideration to problems associated with the joints. In the 194-0's the idea of precasting the entire frame originated because it was realised that prefabrication was a most useful tool in the tool-box of the engineer. Unfortunately, with the type of joints used- cleated, bracketed and bolted joints with connections based on the use of steelwork- it was found more difficult to use concrete than to use steelwork. The degree of tolerance that was needed for constructing units in precast concrete was extremely small and indeed was far more limited than in steelwork. Many engineers had had experience in forcing a structural steel unit into position and in wedging it over so that it could be bolted into place; if, however, this is attempted with precast concrete units, edges splinter off and the result is unsightly or sometimes even dangerous.