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Interference Effects On The Collapse Loads For Footings And Anchors Using An Upper Bound Finite Element Limit Analysis

Electronic Theses of Indian Institute of Science

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Title Interference Effects On The Collapse Loads For Footings And Anchors Using An Upper Bound Finite Element Limit Analysis
 
Creator Kouzer, K M
 
Subject Structural Analysis (Civil Engineering)
Finite Element Analysis
Anchorage (Structural Engineering)
Loads (Civil Engineering)
Footings (Structural Engineering)
Sandy Soils
Foundations - Bearing Capacity
Foundations (Civil Engineering))
Upper Bound Limit Analysis
Horizantal Anchors
Bearing Capacity Factor Ny
Multiple Strip Footings
Collapse Loads
Structural Engineering
 
Description The present thesis is an attempt to investigate the interference effects on the magnitudes of the ultimate failure loads for a group of closely spaced strip footings and strip plate anchors. On account of an increase in the number of different civil engineering structures, footings and anchors are often need to be placed very close to each other. In such a situation, the ultimate bearing capacity/pullout capacity of an interfering footing/anchor becomes significantly different from that of a single isolated footing/anchor. The effect of interference on the magnitude of failure load is usually expressed in terms of an efficiency factor (%y); where £,y is defined as the ratio of the magnitude of the failure load for a strip footing/anchor of a given width in the presence of other footings/anchors to that of the magnitude of the failure load for an isolated single strip footing/anchor having exactly the same width. No rigorous analysis seems to have been carried out so far in literature to investigate the interference effect for a group of footings and anchors. In the present study, it is intended to use rigorous numerical upper bound limit analysis in combination with finite elements and linear programming in order to determine the collapse loads for the problems of both isolated and a group of footings and anchors. Three noded triangular elements are used throughout the thesis for carrying out the analysis for different problems. The velocity discontinuities are employed along the interfaces of all the elements. The plastic strains within the elements are incorporated by using an associated flow rule. The Mohr Coulomb yield surface is linearised by means of an exterior regular polygon circumscribing the actual failure surface so that the finite element formulation leads to a linear programming problem. In solving the different problems taken in this thesis, computer programs were developed using 'MATLAB' with the usage of 'LINPROG' - a library subprogram for doing the necessary optimization.
The bearing capacity factor Ny for an isolated single rigid strip footing placed on a cohesionless ground surface has been computed and its variation with respect to the footing-soil roughness angle (8) has been examined in detail. It is clearly noted that an increase in 8 leads to a continuous increase in Ny. The solution is also obtained for a perfectly rough footing without considering any velocity discontinuity surface along the footing-soil interface. With 5 = Scr/B. '
In the case of a group of multiple strip footings, the value of £y is found to increase continuously with a decrease in S/B. The effect of the variation of spacing on §y is found to be very extensive for small values of S/B; the magnitude of ^y approaches infinity at S/B = 0. For all the values of S/B ground heave is invariably observed on both the sides of the footings. The magnitudes of ^Y for given values of S/B and 2c/tan
 
Contributor Kumar, Jyant
 
Date 2011-02-17T06:57:37Z
2011-02-17T06:57:37Z
2011-02-17
2008-04
 
Type Thesis
 
Identifier http://hdl.handle.net/2005/1070
 
Language en_US
 
Relation G22347