الفهرس 
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Abstract
7.1SUMMARY
In this thesis, behavior of reinforced concrete ledge beams under vertical loads acting at the ledge part at midspan was experimentally and analytically investigated. Sixteen test specimens with different concrete dimensions, different vertical load eccentricities and different amount of transverse reinforcement were experimentally examined. The analytical investigation aimed to model the tested specimens using a finite element program ANSYS version 14 computer program and then comparing the results with those of the experimental tests. Furthermore, another analytical study was accomplished using strut and tie model to propose another design approach for ledge beams.
7.2 CONCLUSIONS
Based on the results obtained from the experimental and analytical investigation, the following main conclusions can be furnished:
1- The effective width of hanger steel reinforcement of vertical load acting on the ledge part is about (4-5) times the ledge height each side from the acting load. This result is compatible with The PCI Design Handbook (2010). The effective width of hanger steel reinforcement according to the PCA notes on ACI (318-14) is small
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compared to the experimental results and gives unreasonable results.
2- The design equation of the hanger steel reinforcement of vertical load acting on the ledge part according to the PCI Design Handbook (2010), which takes a modification factor depending on the eccentricity of vertical load and the concrete dimensions of cross section, is compatible with the experimental and analytical results compared to the design equation according to the PCA notes on ACI (318-14).
3- The concept of adding the area of hanger steel reinforcement to the reinforcement resisting shear and torsion stresses according to the PCA notes on ACI (318-14) gives large amount of transverse RFT which is actually over conservative design. According to the PCI Design Handbook (2010), the greater amount of the two terms (hanger or shear & torsion RFT.) has to be taken and this approach gives a good agreement with the experimental and analytical results.
4- The punching shear strength of the ledge beam according to the PCI Design Handbook (2010) is realistic to a great extend. This result is clearly appeared when comparing the test results with the predicted PCI punching shear strength.
5- The increase of the eccentricity of the acting vertical load on the ledge part decreases the punching failure load of the ledge beam. This effect is not included into the PCI design equation for calculating the punching shear strength of ledge beams.
6- The increase of the ledge thickness increases the punching failure load of the ledge beam. This result is very reasonable and compatible with the PCI & PCA design equations.
7- The increase of the web width has no significant effect on the punching shear strength of the ledge beam.
8- Three dimensional strut and tie model for ledge beams could be constructed and used to design this type of structures. The strut
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and tie model gives reasonable results which agrees with the experimental results.
9- Reasonable concrete dimensions of ledge thickness to avoid punching shear failure could be estimated using the derived equations derived from the strut and tie models of the tested specimens.
10- The dimensions of the loaded area on the ledge part should be calculated carefully to avoid punching shear failure or compression bearing failure.
11- The average stress in the hanging stirrups must not exceed the yield stress of steel reinforcement to avoid separation of the ledge part from the web.
12- The concept of constructing the 3-D model could be used in any reinforced concrete structures subjected to combined effects of bending moments, shearing forces and torsional moments.
7.3 Suggestions for Future Studies
The current research work has contributed to understand the behavior of reinforced concrete ledge beams under vertical loads acting on the ledge part. However, several topics have been unveiled for investigation and some propositions require further validation. Several suggestions for future studies are given hereafter,
1- Further tests on ledge beams with different distribution of shear reinforcement should be performed.
2- Study the effect of using high-strength concrete on the punching shear resistance of ledge beams.
3- Study the effect of boundary conditions of ledge beams on the behavior of load transfer and hanging action.
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4- Study the behavior of the deep ledge beams and its effect on the hanging action.
5- Investigate the effect of ledge thickness on the load transfer to the web for cases beyond this work (hl/hw < 0.3).
6- Study the effect of using prestressed concrete ledge beams on the behavior of punching shear and hanging action