This thesis is the result of the experimental study carried out at the Department of Civil Engineering at the Indian Institute of Technology, Guwahati, India. Richard Scott of Durham University, U.K., who has been physically present during the testing of the first sample.
EXPERIMENTAL STUDY ON BEAM-COLUMN JOINTS WITH BEAM WEAK IN SHEAR
EXPERIMENTAL STUDY ON BEAM-COLUMN JOINTS WITH COLUMN WEAK IN SHEAR
SUMARY AND CONCLUSIONS 187
Some of the researchers conducted tests on beam-column connection without changing the size of tested specimens. It is therefore necessary to undertake study on the size effect of structural behavior of beam-column connections, especially under cyclic loading.
LIST OF TABLES
LIST OF SYMBOLS AND ABBREVIATIONS
ASTM American Standard for Testing Materials BWFLC Weak bending beam with large control BWFMC Weak bending beam medium control BWFSC Weak bending beam small control BWFLR Weak bending beam TH large assembled. BWFSR small beam in flexure, retrofitted, BWSLC beam in shear large control BWSMC beam in weak control medium shear BWSSC beam in weak shear small control BWSLR beam in weak large shear, retrofitted BWSMR Medium shear beam retrofitted retrofitted BWSSR Small shear beam CWS small Column weak shear large control CWSMC Column weak shear control CWSSC Column weak shear small control CWSLR Column weak shear CWSMR large assembled advanced column weak shear medium assembled CWSSR weak shear column small carbon fiber reinforced CFRP reinforced.
INTRODUCTION AND LITERATURE REVIEW
INTRODUCTION
Thus, the use of test results from standard specimens in practice should be applied judiciously, with due regard to the existence of size effects. It is well known that the mathematical modeling of such behavior must be based on the principles of fracture mechanics.
BEAM-COLUMN JOINT
The total effective shear strength of the connection in the horizontal direction is given by. Many of the codes define the nominal shear capacity of the connection based on the strength of the strut.
RETROFITTING
Drilling of holes in the structural members can lead to micro-cracks and weakness in the element. Nowadays, the applications of FRP are becoming popular in the civil engineering construction for their various advantages.
FIBRE REINFORCED POLYMER (FRP) COMPOSITE
The FRP composites are anisotropic materials, meaning their properties are different in all directions. FRP composites have been used for many years in other areas, such as the aerospace industry, and their superior properties are well established.
HISTORICAL DEVELOPMENT OF SIZE EFFECT
However, this attitude changed in the 1980s and size effect gained its popularity in the study of concrete structures, composite structures, etc.
BAZANT’S SIZE EFFECT LAW
Baz˘ant's size effect law has the advantage that it can be transformed into a linear regression plot as. Fracture mechanics size effect: This is the most important source of size effect in concrete construction.
LITERATURE REVIEW
Antonopoulos and Triantafillou [2003] tested eighteen exterior 2/3-scale beam-column joints for evaluating the contribution of FRP to the shear capacity of the joint. Mahini and Ronagh [2010] tested seven 1:2.2 scaled beam-column joint specimens modified by web bond method under monotonic loading. The beams are wrapped with CFRP on both sides as well as around the back of the column for providing FRP anchorage. In the test setup adopted, the columns were supported on each side with specially designed supports that ensured free rotation without translation.
SCOPE AND OBJECTIVE OF THE PRESENT STUDY
Linear regression analysis using Baz˘ant's size effect law was performed for bi-logarithmic plotting. Furthermore, the literature review indicates that there was scant research on the size effect of retrofitted RC structures. Thus, it was considered necessary to carry out size effect studies of RC beam-column joint with and without retrofitting.
Furthermore, it was observed from literature survey that a large number of studies on size effect in pure composite materials were carried out in the form of tension tests, compression tests and bending tests. However, very limited research work was done on size effect of retrofit RC structures using composites. Similarly, among the limited number of beam-column joint numerical studies carried out so far, no literature covering the size effect of RC beam-column joints with and without retrofitting could be traced.
Conducting an experimental study on the size effect of different types of defective AB joint of external beam and column with and without retrofitting subjected to cyclic loading. Interpret experimental findings to investigate the existence of size effect in terms of various parameters such as stress, stiffness, ductility, energy dissipation, etc.
ORGANIZATION OF THE THESIS
To develop the experimental setup necessary for testing samples of different sizes. To carry out numerical study of RC beam-column joint with and without retrofitting for evaluation of yield displacement, ultimate load capacity etc. To study the change in various properties of specimens due to retrofitting and to investigate the possibility of correlating these changes with the size of the tested specimens.
6, experimental investigation of beam-column joints with beam weak in shear RC specimens and corresponding retrofitted specimens has been covered with various observations during testing and interpretation of results, etc. Likewise, chapter 7 includes experimental investigation, observation and interpretation of results for RC beam-column joints with column weak in displacement as well as retrofitted beam-column joints.
CONCLUDING REMARKS
INTRODUCTION
MIX DESIGN
The variation in size of coarse aggregates resulted in slight variation in the mixing ratio of the design mix for a specified target strength of concrete. So three numbers of mix designs were done for target strength of 30 N/mm2 and another three mix designs were done for target strength of 25 N/mm2. The details of material properties used in the mix designs are described in the following subsections.
The cement was tested for its standard consistency, initial setting time, specific gravity and compressive strength as per relevant Bureau of Indian Standards (IS) codes. The compressive strength values found from the compression test and the standard value as per IS are shown in Table 2.2. Thus, it is evident that the cement used met the compressive strength criteria of cement 53.
Three numbers of concrete mixes were designed for three different nominal sizes of coarse aggregates corresponding to each target strength. In this study, a total of six numbers of concrete mixtures, with two intended strengths, were taken into account.
TESTS ON STEEL REBAR
TESTS ON COMPOSITES
CONCLUDING REMARKS
INTRODUCTION
SELECTION OF THE FULL SCALE SPECIMEN
DESCRIPTION OF THE SPECIMEN
For example, BWFLC stands for beam weak in flexure large control specimen, similarly BWSMR stands for beam weak in shear medium retrofitted and CWSSC stands for column weak in shear small control specimens. The detail of all the bam weak in bending: control samples is shown in Fig. In the remaining part of the column, lateral ties of 6 mm diameter mild steel bars were used with a spacing of 150 mm c/c.
The same table also gives details of specimens that are weak in shear, which will be described in the next section. Specimens in this category are completely similar in all respects to beam specimens that have weak flexure: control specimens, except for the shear reinforcement in the girders. In BWSLC, two-armed mild steel bars of 6 mm diameter and 600 mm c/c spacing were provided as shear reinforcement.
Specimens in this category were cast with a relatively poorer grade of concrete than that used in the previous examples to make the column weak in shear. In CWSLC, 6 mm dia double-armed mild steel bars with 900 mm c/c spacing were provided as lateral ties.
BWFLC; B-BWFMC; C-BWFSC
BWSLC; B-BWSMC; C-BWSSC
CWSLC; B-CWSMC; C-CWSSC
- CASTING OF THE SPECIMEN
- RETROFITTING OF THE SPECIMEN
- INSTRUMENTATION AND LOADING ARRANGENENT
- CONCLUDING REMARKS
- INTRODUCTION
- NONLINEAR ANALYSIS
- ELEMENT TYPES
- SOLID65
- LINK8
- SOLID45
- MATERIAL MODELLING
- NONLINEAR SOLUTION TECHNIQUE
- FINITE ELEMENT ANALYSIS
- RESULTS AND DISCUSSIONS
- CONCLUDING REMARKS
- INTRODUCTION
- DISPLACEMENT HISTORY OF SPECIMENS
- TESTING OF LARGE SPECIMENS
- TESTING OF MEDIUM SPECIMENS
- TESTING OF SMALL SPECIMENS
- INTERPRETATION OF RESULTS TO EXPLORE THE EXISTANCE OF SIZE EFFECT
- CONCLUDING REMARKS
- INTRODUCTION
- TESTING OF LARGE SPECIMENS
- TESTING OF MEDIUM SPECIMENS
- TESTING OF SMALL SPECIMENS
- INTERPRETATION OF RESULTS TO EXPLORE THE EXISTANCE OF SIZE EFFECT
A layer of FRP was used for retrofitting specimens of all types. A close-up view of the damaged area at the failure mode of the specimen is shown in Fig. Furthermore, the beam began to rotate around the beam-column joint due to the development of a plastic hinge near the joint area.
The first flexural crack was observed in the beam near the joint junction at a displacement amplitude of ±3.33 mm. The beam was observed to rotate at the beam-column joint due to the development of a plastic hinge near the joint area. In addition, the percentage increase in ultimate bearing capacity due to retrofitting was related to the size of the specimens.
The displacement ductility of the control as well as the assembled specimen is shown in Fig. The fracture in the GFRP sheet at the joint propagates from one end to the other end of the joint with the same displacement amplitude. A close-up of the joint region at the end of the test is shown in Fig.
The onset of fracture in the GFRP slab on the column side of the beam is shown in Fig.
- CONCLUDING REMARKS
- INTRODUCTION
- TESTING OF LARGE SPECIMENS
Finally, bi-logarithmic plots for control and retrofitted samples were plotted as shown in Fig. The slope of the bi-logarithmic plot for retrofitted samples is found very close to -1/2. The percentage increase in ultimate bearing capacity of retrofitted specimens over control specimens for various sizes was calculated and presented in Fig.
Similarly, Figure 6.32 and Fig. show the percentage increase in initial stiffness and energy dissipation due to retrofitting. It should be noted that the displacement ductility increases as the specimen size decreases for both the control and retrofitted specimens. Relative deflection and stresses were calculated and stress changes with relative deflection were plotted for the control and retrofitted specimens (Fig. 6.37 and Fig. 6.38).
It was observed that the bi-logarithmic plot for both control and retrofit samples followed the size effect law proposed by Baz˘ant. However, the size effect was more pronounced for retrofitted samples than control sample in the bi-logarithmic plot.
