FLEXURAL BEHAVIOR OF SELF COMPACTED PERFORATED CONCRETE BEAMS

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 11, November 2018, pp , Article ID: IJCIET_09_11_114 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed FLEXURAL BEHAVIOR OF SELF COMPACTED PERFORATED CONCRETE BEAMS S Sivakumar Assistant Professor, Civil Engineering Department, PSNA College of Engg, Dindigul, Tamilnadu, India T Suresh Assistant Professor, Civil Engineering Department, PSNA College of Engg, Dindigul, Tamilnadu, India C Jaya Guru Professor, Civil Engineering Department, PSNA College of Engg, Dindigul, Tamilnadu, India ABSTRACT The experimental investigation on the effects of newly developed perforated beam system on its flexural behavior is reported in this study. This perforated system facilitates passing of pipes of utility services through it and provides a good-looking appearance. A total of five rectangular beams with one solid reference beam were prepared and tested under repeated loading till collapse.. Three main factors were studied namely flexural performance, ductility and the reinforcement configuration around the perforations (circular stirrups and crossbars). It could be concluded that the perforated beams with 150 mm perforations diameter reinforced with croos-bars stirrups around the opening enabled to increase flexural capacity by 22%. In addition the other experimental specimens examined showed more or less the same ultimate capacity as well as outperformed ductility when compared to those of solid beam. Key words: RC beam, perforated beam, cross-bars, ductility, self-compacting concrete(scc) Cite this Article: S Sivakumar, T Suresh, C Jaya Guru, Flexural Behavior of Self Compacted Perforated Concrete Beams, International Journal of Civil Engineering and Technology (IJCIET) 9(11), 2018, pp INTRODUCTION Nowadays, providing openings in the reinforcced concrete beam in modern RC structures become a common practice. Openings in beam become necessary to provide service lines like water supply lines, air conditioning ducts etc to pass through in order to save the height of the room. Services and structural engineers have to work hand in hand so that proper decision is editor@iaeme.com

2 S Sivakumar, T Suresh, C Jaya Guru made in advance to avoid any undesirable damage to the concrete beams. Passage of the pipes and ducts for the air-conditioning, heating, sewage, and water supply systems, and for the telephone, electricity, and internet cables through transverse openings in floor beams enables the engineers with a more efficient building design by utilizing the dead space above the beam soffit. The utilization of this dead space reduces the heights of the bearing and nonbearing members and therefore the overall height of the building. Consequently, the loads on the foundation and on the load-carrying structural members are reduced and a more economical design is achieved. The provided opening in RC beams may take any shape, however, the circular and the rectangular configurations are the most common shapes. At the same time a beam containing opening must be checked for its strength or the region near the opening should be designed adequately to eliminate the weakness. Further more it was found that introducing large openings in RC beams without providing proper internal reinforcement could reduce the ultimate capacity significantly. The objective of the study is to examine the behavior of a new perforated beam system which is tested under repeated loading till failure. Inorder to facilitate the casting of concrete around the openings (perforations) and preventing any honeycomb, self-compacting concrete was selectively choosen. A total of five perforated beams with perforation diameters of 150 mm and 200 mm were prepared along with one solid reference beam. The configurations of the provided internal reinforcement around the perforations are in the form of circular and cross-bars. 2. EXPERIMENTAL WORK 2.1. Introduction An experimental study in order to investigate the flexural performance of newly developed perforated beam system is conducted. Identifying the locations of such perforations in the beam is an important task as well as the reinforcement around the opening should be arranged inorder to prevent from premature failure. The presence of various openings and the diagonal reinforcement around the openings are the main parameters carried out in this study. The flow or filling ability of the concrete around the perforations are achieved by using self compacted concrete Constituent Materials for SCC Ordinary Portland Cement(OPC) The cement used was an ordinary portland cement of grade 53 with a specific gravity of 3.12 which satisfies the requirements as per IS 12269:2013. The physical properties of cement are tabulated in Table 1: Table 1 Physical Properties Of Cement Si No. Property Result 1 Specific gravity Fineness of cement 8 % 3 Initial setting time 41 min 4 Final setting time 710 min editor@iaeme.com

3 Flexural Behavior of Self Compacted Perforated Concrete Beams Fine Aggregate Locally available natural sand passing through 4.75mm sieve as per IS was used as fine aggregate. Coarse Aggregate Crushed angular stone of size 10 to 16mm from a local source is used as coarse aggregate for making SCC. The physical properties of the aggregates are tabulated in Table 2: Table 2 Physical Properties Of The Aggregates SI No. Properties F.A C.A 1 Size 4.75 mm mm 2 Specific gravity Fineness modulus Bulk density kg/l kg/l 5 Water absorption 0.3% - Water Inorder to achieve a concrete of maximum strength the quality and quantity of water used is very important Mix Design for SCC As self compacting concrete possess more improved qualities and enhanced productivity and good working conditions due to less compaction, proper method for mix design need to be identified. Most common method was proposed by Nan Su. The mix design for M30 grade concrete is prepared by Nan-su method and are tabulated below. Table 3 Mix Ratio MIX RATIO CEMENT FA CA WC RATIO Test for Fresh SCC Mixes Many different test methods have been developed in attempts to characterize the properties of SCC. So far no single method or combination of methods has achieved universal approval and most of them have their adherents. Similarly no single method has been found which characterizes all the relevant workability aspects so each mix design should be tested by more than one test method for the different workability parameters. Table 5 Recommended Limits and results for Different Properties Si No. Properties Range Test Result 1 Slump flow test (mm) 750 (mm) 2 T 50cm 2-5 (secs) 5 (secs) 3 V funnel test 6-12 (secs) 9 (secs) 4 L Box test (mm) 1.0 (mm) 5 U Box test 0-30 (mm) 10 (mm) editor@iaeme.com

4 S Sivakumar, T Suresh, C Jaya Guru Figure 1 Slump Flow Test Figure 2 V Funnel Test Figure 3 L Box Test Figure 4 U Box Test 3. EXPERIMENTAL PROGRAM 3.1. Beam Specimens A total of five RC beams with 150 mm width by 400 mm rectangular section and with a span of 2000 mm were tested. The flexural reinforcement of all beams consisted of two deformed steel bars of 16 mm diameter in the tension side and two deformed steel bars of 10 mm diameter in the compression side. The stirrups of the solid beam consisted of smooth bars of 8 mm diameter spaced every 120 mm along the entire span of the beam. The flexural reinforcement, the circular openings and the diagonal openings around the openings were reflected as the test parameters. The beam CB will be the control specimen and the beams represented as PB-20-C 1, C 2 and PB-15C 1, C 2 will be the perforated beams with circular perforations of 200 mm and 150 mm diameter spaced at every 100 mm. The C 1 and C 2 represents the circular stirrups and cross-bars of 8 mm diameter. In order to form the circular perforations, PVC pipes of 150, 200mm diameter having 2 mm thickness were cut into slices of 150 mm depth and fixed accurately. Figure 5 Reinforcement Detailing Of Control Beam editor@iaeme.com

5 Flexural Behavior of Self Compacted Perforated Concrete Beams Figure 6 Reinforcement Detailing Of Perforated Beam 3.2. Test Setup The experimental program has been conducted on a loading frame of 2000 kn capacity and the loads were measured by a load cell of 100 kn which is directly connected to manually operated jacks. The beams were loaded incrementally under loading in several steps upto complete collapse. After each loading step, load values and the vertical deflections are measured by using anload cell and dial gauges and LVDT S placed at the midspan and settlement at the end supports. Figure 7 Test Setup 4. RESULTS AND DISCUSSION 4.1. Flexural Behavior of Beam The reference solid beam as well as the perforated beams were tested under loading where at each loading cycle the beam was tested. The key points such as the first cracking load for both flexure and shear, the yielding point of the main tension steel, the ultimate load, the maximum mid-span deflection and the permanent deflection after unloading were recorded as summarized. Beam First flexural crack Table 4 Characteristics Of Tested Beams First shear crack Ultimate load Mid span deflection Permanent plastic deflection after unloading (kn) (kn) (kn) (mm) (mm) CB PB-20-C PB-20-C PB-15-C PB-15-C editor@iaeme.com

6 S Sivakumar, T Suresh, C Jaya Guru Figure 8 Testing of Control Beam Figure 9 Testing of Perforated Beam 6 5 Deflection (mm) CB PB-20-C1 PB-20-C2 PB-15-C1 PB-15-C Load (kn) Figure 10 Load Vs Deflection graph 4.2. Ductility It can be noticed that the reinforcement configuration will definitely have some effect on the ductility keeping the same mass loss value. The table below shows the variation of ductility exhibited in the beams with perforations. Table 5 Ductility of Beams Beams Ductility Absolute Relative CB PB-20-C PB-20-C PB-15-C PB-15-C editor@iaeme.com

7 5. CONCLUSIONS Flexural Behavior of Self Compacted Perforated Concrete Beams For beams having circular perforations of 200, 150 mm diameter the circular and cross-bars configurations of the internal stirrups around the perforations showed insignificant effect on the ultimate capacity of the perforated beams. When orthogonal reinforcement around the perforations were provided, the ultimate capacity was increased. Considering the ultimate flexural resistance and the exhibited ductility, the beam PB-15-C2 of circular perforations of 150 mm diameterwith cross bars performed well with an increase in the ultimate capacity of 22 % when compared to those of solid beam. It showed approximately the same ultimate capacity as well as outperformed ductility for all the other perforated beams when compared to those of solid beam. The use of circular reinforcement around the openings have also contributed to the flexural rigidity and ductility of a beam with openings. The failure of a beam due to Vierendeel action reduces the ductility and energy absorption capacity of the beam and the reduction in the rigidity due to provision of openings increases as the tension reinforcement ratio of the beam increases. REFERENCES [1] Ahmed et al (2012), Reinforced concrete beams with web openings, Materials and Design, Volume 40, pg no [2] BengiAykac et al (2013), Flexural behavior of RC beams with regular square or circular web openings, Engineering Structures, Volume 56, pg no [3] Jebasingh Daniel et al (2014), flexural strength of Beams with Opening Engineering Structures, Volume 4, No.2, [4] Mohammad A et al (1983), Torsion test of R/C beams with large openings Struct. Eng., Volume109, pg no [5] Nilesh H. Saksena et al (2013), Experimental of reinforced concrete beam with web opeings Engineering Structure, Vol. II, pg no [6] Sabahattin Aykac et al (2014), Flexural Behavior and Strength of Reinforced Concrete Beams with Multiple Transverse Openings ACI Structural Journal [7] Hajime Okamura and Masahiro Ouchi, (2003) Self Compacting Concrete, Journal of Advanced Concrete Technology Vol. 1, pp [8] Pradeepa et al (2015), An Experimental Study on Properties of Fibre Reinforced Self Consolidating Concrete National Conference on Research Advanced in Communication, Computation, Electrical science and structure (NCRACCESS) ISSN pp: [9] Shiram et.al Evaluated the fresh properties of SCC using slump cone Journal of Advanced Concrete Technology. [10] IS 456. (2000) Indian Standard Plain and Reinforced Concrete Code of Practice, Bureau Indian Standards, New Delhi editor@iaeme.com