The preyield cracked stage is from the cracking load to the yield load. Grading of Fine Aggregate. SikaWrap C Table 5. The CFRP strips were applied in one layer to the lower face tension face of the circular RC slabs as supplementary tension reinforcement around the openings in two orthogonal directions, parallel to the directions of internal grid reinforcement.
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Mixing Water Ordinary clean tap water was used circulra casting and curing all the slabs. Experimental Program During this research, the study of the behavior of slabs was based upon eight circular RC slab specimens. Introduction In existing reinforced concrete structures it is very often required to create openings in the slabs to accommodate new stair wells, elevators shafts, utility ducts, and also required for plumbing fire protection pipes, heat and ventilation ducts and air conditioning.
Load-Deflection Response Figures 15 through 18 compare the normalized load- central deflection response of all eight tested specimens. Eight circular RC slabs were constructed and tested under repeated cirvular. Due to lightweight, high strength, good fatigue, and corrosion properties, fiber reinforced polymer FRP have been intensively used in the repair and strengthening of concrete structures . The cylindrical concrete specimens were placed in a container filled with tap water for 28 days.
The jack was operated using the valve of hydraulic oil and load cell was connected to a data logger TDS for recording the applied repeated loads. Introducing openings in slabs can severely weaken the slabs due to the cut out of both concrete and reinforcing steel . The presence of CFRP strips delays the crack initiation and arrested their propagation.
All the slabs were geometrically similar, having dimensions of mm in diameter and 75mm in thickness. Sikadur Table 6.
Mixture details are given in table 7. Description of Applied Repeated Loads Concrete behavior subjected to repeated loads is differ than the one subjected to static loads.
The epoxy resin Sikadur as shown in ddsign 3 used in this paper was also provided by Sika corporation. Conclusions 1- The presence of CFRP strips on the tension face of circular slabs delays the cracks initiation and arrested their propagation.
Testing Procedure Before the day of testing, the lines of supports and points at which the deflection was measured were marked. Fine Aggregate River sand was used as fine aggregate. It was washed and cleaned by water several times and left to dry in the air.
Equipment and Curing Procedure. The steel work setup for the testing machine includes two main parts: Description of Applied Repeated Loads 7. The clear concrete cover of 15mm was maintained by using plastic spacers. Description of Testing Rig 6. Properties of Sikadur .
Strengthening of Circular RC Slabs with Central Openings Using CFRP Stripsunder Repeated Loading
The chemical and physical analyses of the used cement are given in tables 1 and 2respectively. In general, unstrengthened control slab specimens, a large desgin in deflection were noticed in a comparison with strengthened slab specimens. The inclined shear cracks usually started from the flexural cracks. SikaWrap C Table 5.
Steel Reinforcement Deformed steel bars of size 6mm in diameter were used as reinforcement to test slab specimens. The preyield cracked stage is from the cracking load to the yield load.
Two different strengthening schemes were used in this paper. Bonding Material The building and construction industries presented some of the largest types of adhesive materials, many applications are non-structural in the sense that the bonded assemblies are not used to transmit or sustain significant stresses e. The uncracked stage is characterized by an approximately linear relationship between the load and the central deflection and both the concrete and steel behave essentially elastic the cracked stage can be divided into two substages: Because of its drawbacks dedign low corrosion resistance and of handling problems involving excessive size and weight, there is need for the engineering community to look for alternatives.
The loading support for the different shapes of openings is shown in figures 7 through 9.