الفهرس 
OVERVIEW
EXPERIMENTAL WORKOnly 14 pages are availabe for public view
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Abstract
This research was initiated with the objective of investigating the behavior of light weight concrete “LWC” by partial aggregate replacement with polystyrene foam under uniaxial eccentric compression. This is attributed to the fact that the reduced mass concrete reduces the imposed lateral load during earthquakes. Primarily, literature review was carried out in the field of LWC in order to determine the research gaps or weak points to commence this research. Accordingly, an experimental work was carried out. It encompassed three investigation phases (mix selection phase, stress block parameter phase and behavior under eccentric compression phase). All through the mix selection phase, five lightweight concrete mixes were investigated in terms of compressive, and tensile strengths. During the stress block investigation phase, LWC was examined in terms of stress block parameters. Throughout the eccentric load investigation phase, the behavior of LWC columns was examined under eccentric load.
In the first phase the properties of the different mixes were determined in order to use suitable mix, in this study we used mix which have cylindrical compressive strength 30 MPa, cubic compressive strength 38MPa, tensile strength 3.35MPa, and density 18.1KN/m3.
The second phase was aimed to determine the stress-strain distribution of LWC and evaluate equivalent compressive stress block parameters of the rectangular stress block, Two square half-scale columns specimens with dimension 200 x 200 mm and 1600 mm height was tested. It had two steel beams, each of them was connected at the top and bottom ends of the specimen to transfer the moment from the applied load to specimen. This phase results indicated that the stress block parameter k1, k2, k3 is equal 0.49, 0.37, 1.12 respectively when cylinder lightweight concrete compressive strength 30 MPa. from these values we found the stress block parameters α1 and β1 equal 0.78 and 0.73 respectively.
For the third phase, six half scale LWC square specimens with different eccentric ratios (e/t) and different transverse reinforcement were tested under eccentric loads using the same dimensions as in the second phase. The results signposted that increasing eccentricity ratio change the behavior of columns failure from compression to tension failure, and it leads to reduced failure load of column due to generation of additional moment (resulting to increase lightweight concrete compression side strain value, reduce strain in the longitudinal reinforcement, and reduce the transverse reinforcement strain at failure load). On the other hand, the results designated that increasing transverse reinforcement ratio (VS/VC) (by 0.4%, to 0.6%) in LWC columns provided better confinement but the same location of failure and lead to an increase in failure load, ductility so as deformation, and it resulting to increase lightweight concrete compression side strain value, increase strain in the longitudinal reinforcement, and increase the transverse reinforcement strain at failure load.
Also a non-linear finite element model was performed using software package (ANSYS 15), to verify with the experimental program results, and thirty-six square reinforced lightweight concrete columns modelled under concentric and eccentric loads, in order to determine the impact of both slenderness and longitudinal reinforcement ratios on the behavior under uniaxial eccentric compression. This results indicated that increasing longitudinal reinforcement ratio (i.e. by 0.8% to 1.1%, and 2%) has no effect on the failure pattern at the same eccentricity but it lead to an increase in failure load, so lightweight concrete compression side strain value increased, strain in the longitudinal reinforcement in inner and outer sides increased, and the transverse reinforcement strain at failure load increased. On the other hand the model results designated that increasing the slenderness ratio (λ) (i.e. from 6 to 15) increased the buckling, which reduced the failure load due to generation additional moment from buckling (deformation reduced at maximum load so as strains, and it leads to reduce LWC compression side strain, reduced strain in longitudinal reinforcement and reduced the transverse reinforcement strain).
The parametric study analysis resulted in predicated design equations for lightweight concrete short or long columns subjected to axial and eccentric loading with taking into consideration the effect of transverse reinforcement.
In the same context, recommendations for future research so as engineering practice were suggested. Innovative about this research is carrying out experimental work; verifying the results numerically and providing design equations, that most probably, might be incorporated during LWC design.