The Crack Pattern Of R.C Beams Under Loading
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1. A reinforced concrete beam was tested under static two-point concentrated loading to study the effect of different web reinforcement arrangements on ultimate shear strength. 2. It was observed that diagonal cracks developed first in deeper beams while flexural cracks developed first in shallower beams with sufficient reinforcement. 3. The crack pattern and failure mode were similar across all test beams despite variations in web reinforcement, with diagonal cracks forming first in deeper beams.
The Crack Pattern Of R.C Beams Under Loading
- 1. GAZIANTEP UNIVERSITY GRADUATE SCHOOL NATURAL AND APPLIED SCEINCE DEPARTMENT OF CIVIL ENGINEERING M.SC IN CONSTRUCTION ENGINEERING CE545 : DEFORMATION AND FRACTURE THEORIES STUDY No: 5 The Crack Pattern Of R.C Beams Under Loading Submitted by AHMED ASSIM ABDULLAH STD No: 201444960
- 2. The loading conditions can be categorized with respect to the ratio of load duration (to) to characteristic response time (T) as proposed in Table At high rates of loading the response of structures is affected by propagation of stress waves and motion-generated inertia forces. The dynamic response of a structure to impact loading can be analysed in terms of a local (primary) response in the direct vicinity of the applied load and of an overall (secondary) response of a structural member or the entire structure .
- 3. The behaviour of a system consisting of the structure and an impacting body depends on their masses and rigidities, sizes and shapes of contact surfaces, initial velocities, stiffness of structural members and supporting conditions , among other factors .
- 4. The local response of concrete structures involves crushing, punching shear, spalling and scabbing of concrete. In the case of hard missile impact significant penetration and even perforation of concrete members may occur. These phenomena are governed by stress wave propagation and behaviour of sound and cracked concrete under multiaxial, high rate loading conditions. Due to the complex nature of the local response of concrete structures reliable and economical analysis, so that empirical formulae often have to be used in design procedures. Several formulae and results of hard missile impact tests are reviewed by Hughes , The following formulae for the penetration depth x^ and for the barrier thicknesses h and h preventing scabbing and perforation respectively :
- 5. Concrete Under Tension : The beam was tested under two- points concentrated load by ? kips capacity universal testing machine (hydraulic type). The load was applied on the top surface. long steel plate and the reactions were supported. long steel plates placed at the bottom of the beams. One of the reaction plate rested on a steel block and itself placed on the anvil of the testing machine. The other reaction plate was placed over a steel block supported by 5/8-in. diameter steel rollers. I-joists with rollers and rubber pads were employed as load transfer devices for two series of beams. The support lines were clearly marked on both sides of the beams. The loading blocks were also marked on both sides at their centers. A deflectometer graduated in 0.001 in . division was used to measure the mid span deflections of test beams at each load increment. The beam was then loaded and deflection readings were taken at regular interval of load increment. Test beams were white washed to facilitate visual observation of the propagation of cracks on the surface of beam . Cracks were deeply marked with a soft pencil upon their formation on the beam surface and the load intenSity at which it was formed was noted besides the crack. One of the cylinders cast along with each of the test beam was tested under axial compression to determine the ultimate compressive strength of concrete and the other was tested under diametrical compression to find the split cylinder tensile strength.
- 6. A reinforced concrete beam have been tested under static two point concentrated loading system. The special interest of the investigation is to study the effect of different web reinforcement arrangement on the ultimate shear strength of brick aggregate concrete beams under two series and as a whole the overall behavior of deep beams under two point concentrated loading. The specific observation of interest during the test has been recorded and is being presented in this chapter. The critical load at tension cracking , the load at flexure cracking , the ultimate load and deflections under different load intensities are noted in a systematic manner during the test. For an easy grasp of the overall performance of the beams, the test results are presented here in a tabular form. a general description of the contents of the different tables containing various test data seems necessary and is furnished below. the typical beam properties of all the beams have been provided. This includes the actual overall depth , beam width, span to effective depth ratio, web steel ratio (both for vertical and horizontal web steel), cylinder crushing strength and split cylinder strength. The different steel ratios are computed on the basis of actual area of steel provided and mean of the measured width and effective depth after casting. Some of the basic properties of brick aggregate concrete like, compressive strength , split cylinder strength and the relation between them is given by Brazilian ratio and the unit weight of harden concrete is computed by dividing the weight of standard cylinder by its volume. Mode of Failure and Crack Pattern The crack pattern and the mode of failure of all the test beams were almost similar despite the variations in web reinforcement arrangement. From the test it was observed that diagonal cracks develop first in relatively deeper beams and flexural cracks develop first in shallower beams provided the beams have sufficient reinforcement. The crack pattern of beam A2 is shown below:
- 7. Failure at Macro-Scale Although the stress-displacement curves give an indication of the failure mechanisms, to fully understand the rate dependency of the dynamic failure behaviour of concrete it is necessary to study the crack patterns in detail. Therefore, after the dynamic experiments are finished, the specimens are impregnated with a fluorescent epoxy. After impregnation, the specimens were sawn in half to be able to study the macro-crack patterns. From Figures can be concluded that the macro-crack patterns of the static and the SHB tests are not that different, although the static cracks seem to be a little more whimsical. In both cases, almost no fractured aggregates were detected and most of the aggregate particles were pulled out of the cement paste. The particles that were fractured had a low density and probably had a lower strength than the cement paste. The few fractured particles were observed both in the static tests and the SHB tests. ved both in the static tests and the SHB tests. The macro-crack patterns of the MSHB tests differ per test. Sometimes the width of the zone with macro-cracks seems to be very small and other times the width is larger and the cracks are more whimsical (Figs. Above ) The characteristics of the macro-crack correspond with the shape of the stressdisplacement curves; when the peaks of the curves are wider, which indicates multiple fractures, the width of the
- 8. zone with macro-cracks seems to increase. A comparison between the macro- crack patterns of the static and SHB tests and the crack patterns of the MSHB tests is difficult, since the characteristics of the macro-crack in the MSHB tests are not always the same. One major difference can be observed; the amount of fractured aggregate particles. In the MSHB tests more aggregates are fractured, than in the other two loading conditions. However, the cracks not always run through the aggregate particles but also move around them, searching for the weakest part of the cement paste close to the particles; the interfacial transition zone (ITZ).