الفهرس 
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Abstract
ABSTRACT
Among many types of reinforced concrete buildings, reinforced concrete flat slab structure is very popular; it consists of flat plate and columns, with no beams between the columns to support the slab. The research addresses the behaviour and design of this type of structures. Emphasis is on the punching shear behaviour of slab-column connections by using shear studs in seismic zones.
Flat slab-column structural systems are popular due to reduction of building story height, easy setting up of formwork, convenience for utilities layout, and good slabs appearance. However, this type of structure can easily be subject to brittle punching shear failure. When the flat slab-column connections are subjected to heavy vertical loading, cracks will occur inside the slab in the vicinity of the column. These cracks then propagate through the slab thickness at an angle of 20 to 45 degree to the bottom of the slab. This can lead to punching shear failure of the slab along the cracks. When subjected to seismic lateral load, shear stresses in the slab increase due to an unbalanced moment (from horizontal loading), and the slab-column Connection is more likely to fail by punching shear.
Objectives of the Research
1- Evaluation of the behaviour and resistance of the punching shear capacity of flat concrete slabs subjected to vertical load in addition to reversed cyclic moments.
2-To propose a set of recommendations when designing in the light of practical and theoretical results based on international codes such as ACI318-14, EC2-2004, CSA A23.3-04 and ECP203-2018.
3- Preparation of proposed equations for the calculation of the punching shear resistance of RC flat slabs with and without shear reinforcement (shear studs) can be used in the Egyptian Code ECP203.
Experimental Program and Theoretical Program
A set of eight full-scale reinforced concrete slab-column connection specimens were tested under vertical service and cyclic loads. The first specimen was tested under vertical (gravity) load only up to punching shear failure while the other specimens were tested under constant vertical load and reversed cyclic load. The vertical load for each specimen was kept at a constant value throughout the testing. The cyclic lateral drift with increasing intensity was applied to the columns. The specimens were level of gravity punching load, number shear studs and layout of shear studs around of column. Strain in flexural rebars in the slabs, crack widths, lateral loads, and displacements were obtained.
The peak lateral load (moment) and its corresponding drift ratio, connection stiffness, crack width, and ductility were compared among different specimens. The testing results show that shear studs can increase lateral peak load resisting capacity, lateral drift capacity at peak load, and ductility of the slab-column connection. Shear studs also change the failure mode of the slab-column connections and increase the energy dissipation capacity. The experimental results are analyzed and compared to international codes such as American Codes ACI318-14, Euro Code EC2-2004, Canadian Code CSA A23.3-04 and Egyptian Code ECP203-2017. Finally developing the design guidelines available test from the experimental results as well as punching design recommendations for slab-column connections in seismic zones in Egypt. The proposed design guidelines and equations are based on the following design codes ACI318-14 and ECP203-2017.
Conclusions
The conclusions based on the experimental results are presented first, followed by the theoretical investigations on design of slabs with and without shear studs, the following detailed conclusions are drawn:
1- The experimental results in the test of slab-column connections subjected to vertical load plus cyclic loading showed a clear difference in the shape and distribution of cracks around the RC Column section compared to slab-column connections subjected to vertical load only.
2- The experimental results showed that the punching shear resistance of the slab-column connections are reduced if subjected to lateral cyclic loading in addition to the vertical load.
3- Tests subjected to cyclic moments indicate that the anticipated drift ratio can be achieved without shear reinforcement indicating conservative provisions of ACI 318-14 in this regard.
4- Increasing the gravity shear ratio reduces the displacement ductility considerably as this factor is related to the connection drift capacity.
5- The code provisions of ACI318-14, EC2-2004, CSA A23.3-04 and ECP203-2017 predicted accurately the failure loads for reference control specimen subjected to gravity shear only, while overestimated the failure loads for all other specimens under reversed cyclic moments.
6- Shear studs are effective in increasing peak lateral load capacity of slab-column connections. For all tested specimens with shear studs, for four rows of studs an increase of 26%~293% was observed.
7- The specimens with shear studs can undergo more lateral drift cycles at large deformation, showing a significant increase in energy dissipation capacity.
8- Shear studs can change failure mode of the flat slab column connections. Slabs designed properly with shear studs will exhibit desirable flexural while slabs without shear studs can be subjected to abrupt punching shear failure.
9- The tests results confirmed the trend of the ACI equation relating the drift capacity with the level of gravity shear for connections subjected to cyclic moments in addition to gravity shear. The ACI equation shows better agreement with the test results if the shear stresses are calculated according to EC 2.
10- The ductility capacity of specimens with studs were much higher than of specimens without shear studs, which shows that the studs contribute to improve ductility behaviour and prevents sudden brittle failure after the ultimate load.