Effect of Tie Beam Dimensions on The Behaviors of Isolated Footings Under Eccentric Loading
Australian Journal of Basic and Applied Sciences
INTRODUCTION The differential settlement of isolated footings should be minimum. In order to minimize the differential settlement between isolated footings, it is recommended to connect them by tie beams. Georgiadis and Butterfield (1987) investigated the response of footings on sand, under eccentric loads. Apparatus was developed that simultaneously apply loads to footings at any eccentricity. A method was developed for predicting vertical and horizontal displacements and rotations of loaded
... otings on sand. The interaction diagrams between the vertical loads, horizontal loads, and moments that cause failure of the footing were presented. Mahiyar (2000) presented the analysis of angle shape footing under vertical load by using finite element program. The analysis has been done by considering the parameters as depth of footing and eccentricity width ratio. The behavior of an Angle Shaped Footing under Eccentric Loading was studied. Elsaadany (2004) examined the role of tie beam (strap beam) of eccentric footings resting directly on soil by using numerical parametric finite element technique. The Winkler model was used to model the soil behavior. The effect of allowable bearing capacity of soil and the tie beam stiffness on contact pressure, settlement and bending moment of tie beam-eccentric footing was presented. Al-Omari and Al-Ebadi (2008) investigated the effect of tie beams on settlement, moments and shear developed in the foundation. A case study is selected; it is the case of grid foundation composed of nine footings. Three-dimensional nonlinear finite element analyses have been conducted. The soil has been assumed to follow the Drucker-Prager rate independent plasticity criterion. The parametric study conducted involved the effects of tie beams proportion, tie beams soil contact and an induced soil weakness beneath parts of the total foundation area. The detailed results indicated that the tie beams reduce the total and differential settlements of footings but this restriction is often on the expense of increasing the shear and moment particularly in the central footing. Dayamond and Mahiyar (2009) investigated the behavior of angle shaped footing under inclined loads by performing experimental model tests and finite element analyses. A series of loading tests were conducted on a square angle shaped footing on sand with different angle and length of footing projection the footing was loaded at different angles from the vertical: 0°, 5°, 10°, 15°, 20°, 25° and 30°. The comparison between the experimental results and the Finite Element analysis results were presented. It was observed that eccentrically inclined loaded footing can be designed for no or very small negligible tilt by using angle shaped footing with different angle and length of footing projection Thus Model of angle shaped footing can make reasonable predictions of the inclined loading responded. Kumawat et al. (2015) proposed the Tee shaped footing for improving the bearing capacity of shallow footings against the action of eccentric loads. The vertical insertion of the rigid Tee shaped footing, into the bearing soil, provides considerable resistance, against both of sliding and overturning, enough to regain the reduction in bearing capacity and increase in settlement. A series of experimental results by loading footing eccentrically along and perpendicular axes in horizontal plane for reporting ultimate loads and settlement of Tee shaped footing were considered out. Pusadkar et al. (2016) evaluated the effects of eccentricity eccentric-inclined load on performance of square footing resting over sand. The laboratory load tests were conducted on the model footing with eccentric load. The eccentricity ratio (e/B) and inclination angle (α) varied from 0 to 0.2 and 00 to 300 respectively. The results showed that the bearing capacity decreases with increase in the load eccentricity and load inclination. Elbatal and Abo-Alanwar (2017) investigated the straining actions of two square footings connected with tie beams resting on replaced soil. The effect of the interaction between natural soil deposit, soil replacement density and length and foundations were presented. Vertical displacements of soil and foundations, bending moments and shear force along the tie beam length were investigated. It was noticed that variation of replaced soil density changes final straining actions of footings and tie beams. In addition, variation of replaced soil must be considered in foundation deign to avoid error in design. However, in case of the natural soil deposit is dense, increasing the density of the replaced soil increases the maximum moment. Also, in case of the natural soil deposit is loose, increasing the density of the replaced soil has no significant effect on maximum moment. Abstract Background: Foundations may be subjected to eccentric loads. If the load is eccentric the stress distribution underneath the footing will be non-uniform causing differential settlement between the two edges. Objective: In the present study, the finite element program software PLAXIS 3D 2014 has been used to study the effect of tie beam dimensions connecting isolated footings under eccentric loading on settlement and horizontal displacement as well as bending moment and shear force. The investigated program consists of eccentric footings connected with tie beams with different thicknesses and widths. The details and variation of the selected parameters were presented. Results: It was concluded that, the settlement and horizontal displacement values in both directions as well the contact pressure values decrease with increasing the thickness and widths of tie beam. However, the values of bending moment and shear forces along axis decreases with increasing the dimensions of tie beam. In addition, the distribution of stresses under footing along axis's decreases with increasing both of tie beam thickness and width. Conclusion: However, the differential settlements of footings decrease with increasing tie beam dimensions.