الفهرس 
Contact stress distribution below rigid footing resting on sandy soil
Failure of concrete footingOnly 14 pages are availabe for public view
 |  | from | 295 |  |  |
| | | from | 295 | | |
Abstract
It is common practice to strengthen reinforced concrete (RC) footings
by reinforced concrete jackets using shear dowels and a bonding agent to
connect existing and new concrete surfaces. This can cause a significant
amount of stress redistribution beneath the strengthened footing, which
results in an efficient and economical design when taken into consideration.
There is a lack of research regarding load carrying capacity and stress-
redistribution beneath footings resting over the top of sand stratum when a
concrete jacket is applied all around the existing footing. This research
aims to assess the load carrying capacity and stress redistribution beneath
strengthened footings that are subject to concentric and eccentric loading
conditions and residing over cohesionless soil medium. In this respect, an
experimental study was conducted on eight reinforced concrete footings,
among which a full concrete jacket was applied to four footings, while two
footings were strengthened with a partial jacket that applied as a stripped
jacket around column faces only with a width equal to a width of the
column. Two footings were left without strengthening to act as control
footings, one subjected to concentric loading and the other footing
subjected to eccentric loading. The footings had a constant dimension and
flexural steel reinforcement, designed to prevent brittle failure due to
concrete crushing before steel yielding. In the strengthening strategy, the
shear dowels and bonding agent were used to connect new and existing
surfaces in three strengthened footings, and for the other three footings, the
bonding agent was used only to investigate the effect of different
connecting techniques on the stress redistribution and load carrying
capacities in strengthened footings. A nonlinear numerical finite element
(FE) model was developed using ”Abaqus 6.14” and was validated using
the experimental findings. The model was found to be capable of
stimulating the behavior of footings and showing good agreement in
predicting the failure load and simulating the actual interaction between a
concrete footing and resting soil. A parametric study was conducted to
investigate other parameter effects on the load carrying capacity and stress
redistribution beneath the strengthened footings. The parameters included
the reinforcement ratio, ratio of jacket depth to the footing depth, concrete
compressive strength, spacing between dowels, and roughness coefficient
between the existing and new surfaces. The results showed that the contact
stress beneath the center of strengthened footings was higher than the
central contact stress for non-strengthening footings by approximately
10%. Moreover, the distribution of the contact stresses seem to be saddle-
shaped before cracking, and the contact stresses redistributed and shifted
towards the center of footing after cracking during concentric loading.
Furthermore, increasing the ratio between the concrete jacket depth to the
total footing depth after strengthening leads to increased load carrying
capacity and central contact stress. However, if the ratio (d/h) was less than
or equal to 0.25, the load carrying capacity decreased compared with non-
strengthened footings. The results also showed that the distribution of the
contact stresses beneath non-strengthened and strengthened footings were
not consistent with the available theoretical solutions. The effect of using
dowels, in connecting existing and new concrete, on stress distribution
under strengthened footings and load carrying capacity are presented.