ISSN: 2277-9655 Scientific Journal Impact Factor: 3.449 .
[Gupta, 4(4): April, 2015]ISSN: 2277-9655Scientific Journal Impact Factor: 3.449(ISRA), Impact Factor: 2.114IJESRTINTERNATIONAL JOURNAL OF ENGINEERING SCIENCES & RESEARCHTECHNOLOGYSTRUCTURAL DESIGN FOR ECCENTRIC LOADING OF FOOTINGNidhi Gupta**Assistant Professor, Department of Civil Engineering, RKDF BhopalABSTRACTEccentric loading, in which vertical or inclined wall surrounds one or more sides of the soil mass beneath thefooting, is one of the recognized bearing capacity improvement techniques. The footing when provided with footingprojection on one side such that it is an integral part of the footing it is called angle shape footing. Construction offooting projection at the base of the footing, confining the underlying soil, generates a soil resistance on projectionside that helps the footing to resist sliding. In such a footing the soil particles near the footing projection areprevented from moving laterally thus footing projection to tilt in direction opposite the one in which the footing hastendency to tilt thus tilt of the footing can be reduced to zero by providing a downward inclined footing projection ofrequired depth toward the loading side. The idea of angle as well as suitable length of projection has been used hereby giving the footing an angle shape of variable projection angle. Various load inclination angles, load eccentricities,various angles as well as lengths of footing projection were investigated. Load displacement values for all caseswere compared, and favourable design conditions were suggested. Laboratory work and numerical analysis wereperformed to study the behaviour of eccentric loading subjected to eccentric inclined load.KEYWORDS: Eccentric loading, Bearing Capacity of SoilIt is known from the observation of theINTRODUCTIONbehavior of foundation subjected to a load thatbearing capacity failure usually occurs as the shearfailure of the soil supporting the footing. Theminimum gross pressure intensity at the base offoundation at which the soil fails in shear is calledthe ultimate bearing capacity, qu. The ultimatebearing capacity diviedeby the desired factor of safebearing capacity. For the design capacity offoundation it is not only safety against shear failurewhich is considered but also likely settlement. Apressure intensity which is considered safe both withrespect to shear failure and called the allowablebearing pressure, qu or the design unit load. Thus theallowable bearing pressure is excessive settlementdetrimental to the structure.In every building the load is transferred to soil byfoundation. It is necessary to design &Check itproperly for probable failures. The foundation mayfail due to excessive settlement, shear, tilting etc. Afoundation is the lower part of a structure thattransmit the load to the soil orrock. It includes thesoil or rock. Thus, the word foundation refers to thesoil under structure as well as any intervening loadcarrying member. In the design of any foundationsystem the aim is to provide adequate foundation tosupport load margin of safety against bearingcapacity failure i.e. against a soil shear failure and tokeep the settlements within tolerable limits. Thus,there arises a necessity of consideration of twodifferent criteria, viz, the stability criterion and thesettlement criterion in the design of foundationsystem.Factors that affected on foundation design are:(i) Safe Bearing Capacity(ii) Swelling Shrinkage Behavior(iii) Minimum depth of foundation - Lever Arm(iv) Settlement CriteriaThe bearing capacity is affected by the manyparameters like(a) water table(b) eccentricity(c) hape of foundation(d) roughness of foundation base mpressibility of soil(e) loading(f) adjacent footing near the foundationFoundation is classified as shallow and deepfoundation depending on the depth of the loadtransfer member below the superstructure. Thus adeep foundation as the one in which the depth to thebottom of the footing is less than or equal to the leastdimension of footing. In modem usage, the termshallow foundation is used to describe of anarrangement where structural load are carried by thesoil directly under the structure, such as footing andraft and deep foundation is used to carry the load tofirm soil or rock at some depth.http: // www.ijesrt.com International Journal of Engineering Sciences & Research Technology[631]
[Gupta, 4(4): April, 2015]ISSN: 2277-9655Scientific Journal Impact Factor: 3.449(ISRA), Impact Factor: 2.114The bearing capacity may be determined by any ofthe following methods:(i) Calculation by using shear parameter based uponequations proposed by many researches.(ii) By conducting the field test like plate load test,penetration test etc.(iii) By using the guidelines given in the Nationalbuilding code which is based upon the classificationof soil.The evaluation of safe bearing capacity byusing theory does not indicate the true safe bearingcapacity as the field conditions may varying and theequations may not stimulate feild conditions.bearing capacity equation. All soils are covered inthis method by two cases which are designated asgeneral shear and local shear failures. General shearis the case wherein the loading test curve for the soilunder consideration comes to a perfectly verticalultimate at relatively small settlement. Local shear isthe case wherein settlement are relatively large andthere is not a definite vertical ultimate to the curve.The following assumption was made in the analysis. The footing is continuous. The weight of soil above the base level of footing isreplace by equivalent surcharge q yD, The shear resistance of the soil above the base levelof footing is neglected. The base of footing of rough. The principal of superposition is valid.Terzaghi presented the following bearing capacityexpression for general shear failure:qu cNc qNq ViBNq yDB Least lateral dimension of footingN, Nq, NT Dimensionless bearing capacity factors.Limitations: The shear strength of soil above the base level offooting is neglected. Hence for deep footing, errorsbecome large. This theory gives conservative value for footingwhose depths are greater than 0. Subdivision of the bearing capacity problems in twotypes of shear is an arbitary one, since two cases cannot cover the wide range of conditions.BEARING CAPACITY THEORIESThere are two approaches for the analysis of stabilityfoundations. The first these is convectional approachwhich generates from work of coulomb (1977). Thisis based on the assumption of a certain shape for therupture surface. The other approach which standsfrom the works of Rankine (1857) and Kotter (1903)is based on the assumption of simultaneous failure atevery point in certain zone of the soil mass. This isreferred here as plasticity approach.Theories based on conventional approachFellenius Method: - Fellenius (1929) presented amethod for determination of ultimate bearingcapacity of footing on highly cohesive soils. Heassumed failure surface to be of circular cylindricalshape. The expression for the ultimate bearingcapacity of long surface footing on highly cohesivesoils is given byQu 5.5cQu ultimate soil bearing pressureC cohesion of the soilStudy the effect of shear parameters on load carryingcapacity of angle shaped fitting and concluded thatload carrying capacity increases with increases inangle of internal friction and tilt was zero at allvalues.Wilsons (194 1) extended this method tofooting founded below ground surface and theultimate bearing capacity for footing below thesurface of highly cohesive soils is obtained asqu (1 0.38D/B)D Depth of foundationB Width of foundationThe circular are method has the advantage of beingsimople and it gives reasonable result for surfacefooting and footing at shallow depth in highlycohesive soils ( 0)Terzaghi's Bearing Capacity TheoryAssumption:Based on Pranti 'S theory (1920) for plastic failure ofmetal under rigid punches Terzaghi derived a generalhttp: // www.ijesrt.comMeyerhof's Bearing Capacity TheoryAssumption:The bearing capacity of shallow and deep foundationhas been derived by Meyerhof (195 1) taking in toaccount the shear strength of the soil above the baselevel of the footing. For the shallow foundation, heassumed a failure mechanism similar to Terzaghi'sbut extending up to ground surface.The following assumption is made in the analysis: The footing is continuous. The failure surface is composed of straight line andlogarithmic spiral. The principle of superposition is valid.The ultimate bearing capacity qu is expressed interms of (YO, the normal stress along the equivalentfree surface, asq cN oNpq '/2yBNpyWhere, NpclNpq, and Np bearing capacity factors.Limitations:Bearing capacity computed from Meyerhof's theoryare found to be higher then observed bearingcapacities in sands at greater depths.2.4 Skempton's (1951) bearing capacity for clays International Journal of Engineering Sciences & Research Technology[632]
[Gupta, 4(4): April, 2015]ISSN: 2277-9655Scientific Journal Impact Factor: 3.449(ISRA), Impact Factor: 2.114Skempton (1951) recommended the following shapeand depth factors, and values of Nc for surfacefooting on clays. Surface footing (D 0)Nc z5 for strip footingNc 6 for square or circular footing At Depth Ddc (1 0.2 x D/B)forD/B 2.5dc-- 1.5for D/B 2.5 At any depth, for rectangular footing,B X LSc (1 0.2 x B/L) The ultimate bearing capacity is given byqu c Nc dc ScBrinch Hansen's Bearing Capacity TheoryA theory, somewhat similar to theTerzaghi's has been proposed by Hansen (1961). Theultimate bearing capacity according to this theory isgiven byqu c Nc de Sci q Nq Sqdqiq '/27 B N.yS.yd.yi.yWhere,S shape of factord depth of factori inclination of load factorN (Nq 1) coWNq tna2 (45 0/2) e"N.y 1. 80( Nq - 1) tan (approx.)FOUNDATIONSEARTHQUAKESUBJECTEDspecial investigations, both laboratory andtheoretical.Normally the failure of structures duringearthquakes is the result of structural inadequacies,foundation failure, or a combination of both. Thefailure of a building may predominantly due tostructural inadequacies such as poor ductility andimproper beam - column joint. On the other hand, thefailure may due to any structural adequacies but dueto foundation failure. In such failures the soilsupporting the foundation plays an important role.The behavior of foundations during earthquakes isoften dictated by the response of its supporting soildue to ground motion or shaking. So it is necessary toquantify seismic hazards while designing a structureto withstand earthquakes. In general, there are twomajor seismic hazards associated with the design ofstructures and foundations, such as: (i) groundshaking and (ii) ground deformation Seismic hazardscan be established either deterministically orprobabilistically. Sometimes a detailed seismichazard study has to be established using bothdeterministic and probabilistic methods incorporatingthe recently gained knowledge on the definition ofseismic sources, seismic models, attenuation ofstrong ground motion parameters and soil conditions.Design of foundations still remains a challenging taskfor the earthquake geotechnical engineer. Leavingaside the seismic retrofit of existing foundations,which is an even more difficult issue, the design ofnew foundations raises issues which are far frombeing totally resolved. One of the main reasons stemsfrom the complexity of the problem which requiresskills in soil mechanics, foundation engineering, andsoil-structure interaction along with, at least, someknowledge of structural dynamics.TOMany Indian earthquakes in historical times clearlydemonstrated the important role that Geotechnicalconditions play under strong earthquake shaking.Every year world is facing so many earthquakes invarious parts of the world and due to earth quakenumerous R.C. framed building collapsed duringrecent earthquakes emphasized the need for the riskassessment. According to seismic design philosophyfoundation must not fail even during the devastatingearthquakes because the failure of foundation leads tothe collapse of whole structure. If it happens then inthat case loss of the human being and other thingswill be huge. Hence it is important to designfoundations which can sustain the earthquake withoutfailure.ECCENTRIC LOADINGWhen a footing is to resist a moment, the problem ofeccentricity of the load has to be considered.Merehof's (1953) presented chart for thedetermination of ultimate bearing) capacity of aneccentrically loaded footing by introducing theconcept of useful width. This is based on theassumption that the edge of foundation further fromthe point of load application no longer contributes tothe bearing capacity.Behavior of Eccentric LoadingWhen footing is subjected to an axial point load andits centroid matches with the centroid of footing areathen pressure distribution below the footing isuniform. However when the footing subjected to anaxial load with moment or eccentric point load thedistribution below the footing is not uniform anddepending upon eccentricity it may be trapezoidal orOnce earthquake risk and site effects have beenevaluated the foundation designer needs to proceedwith the proportioning of the foundation. To datethere is little in the way of code recommendations tocover this, especially along the emerging trends ofperformance based design. Eurocode is an exceptionand contains an extensive section on the design offoundations to resist earthquake loading. This hasbeen developed using the results of a number ofhttp: // www.ijesrt.com International Journal of Engineering Sciences & Research Technology[633]
[Gupta, 4(4): April, 2015]ISSN: 2277-9655Scientific Journal Impact Factor: 3.449(ISRA), Impact Factor: 2.114triangular. In order to have uniform pressure underthe footing area and centroid of column load shouldcoincide.structures using IS codes and put it for use by theIndian academicians, researchers and practicingengineers. Currently the technology to handle largescale numerical simulations with IS codes andpractices is not available for Indian users. The codepublished by Bureau of Indian standards, whichspecify minimum design requirements for earthquake- resistance design of foundation. These requirementstake into consideration the characteristics andprobability of occurrence of earthquake, thecharacteristics of the structure and the foundation,and the amount of damage that is consideredtolerable. Modern codes provide for reduction forseismic forces through provision of special ductilityrequirements. Detail for achieving the safety,economy in reinforced concrete structures underearthquake forces is given in IS 13920.However due to higher eccentricity it become verydifficult to match the centroid of the column andfooting area, because it may demand a very highfooting size, which is uneconomical.In angle shaped footing subjected to eccentric load,when the eccentric width ratio (e/B) and depth offooting projected (D/B) are in accordance with thirddegree polynomial equation, the footing subjected touniform settlement and uniform pressure.CONCLUSIONThere is need to develop indigenous software in thearea of seismic analysis and design of foundations ofREFERENCES1.2.3.4.5.6.7.8.Abrahamson, N., A. (2000), "State of thepractice of seismic hazard evaluation", 12thworld conference on EQ engineering,Auckland (N.Z.).Czap, Z. (1994), "Finite element analysis ofcutting resistance in foundation design",Periodical Polytechnica: Civil Engineering,38(1), pp 21-28.Danziger, F., A., B., Danziger, B., R. andPacheco, M., P. (2006), "The simultaneoususe of piles and prestressed anchors infoundation design", www.sciencedirect.comDash, R., Suresh and Bhattacharya, S.(2007), "Seismic hazard assessment forfoundation design", Design of s", NICEE, lIT, KanpurE1-Zafraay, A., Fadhil, S. and Al-Hosani, K.(1995), "A new fundamental solution forboundary element analysis for boundaryelement analysis of thin plate on Winklerfoundation", International Journal forNumerical Methods in Engineering, 38(6),pp 887-903.Geoffrey, R., Martin and Ignatius, Po, Lam(2000), "Earthquake Resistant Design ofFoundations:RetrofitofExistingFoundations", 12th world conference on EQengineering, Auckland (N.Z.).VIS 13920:1993, "Ductile detailing ofreinforced concrete structures subjected toseismic forces—code of practice", Bureau ofIndian Standards, New Delhi.IS 1893 (part 1): (2002), "Criteria forearthquake design of structures—Part 1:http: // www.ijesrt.com9.10.11.12.13.14.15.16.17.general provisions and buildings (FifthRevision)", Bureau of Indian Standards,New Delhi.IS 456:2000, "Indian standard codes ofpractice for plain and reinforced concrete",Bureau of Indian Standards, New Delhi.IS 4326:2002, "Code of practice forearthquakeresistancedesignandconstruction of buildings", Bureau of IndianStandards, New Delhi.Jam, A., K. (2002), "Reinforced concretelimit state design (Sixth Edition)", NemChand & Bros, Roorkee.Javier, Avilésa and Luis, E., Pérez-Rochab(2004), "Design concepts for g structures, 27, 443-454.Lipschutz, S. and Poe, A. (1982),"Programming with FORTRAN", Schaum'soutline Series McGraw-Hill Book Company,Singapore.Pecker, A. (2006), "Enhanced seismicdesign of shallow foundations: Example ofthe RionAntrion bridge", 4h Athenianlecture on geotechnical engineering.Pecker, A. and Michael, J., Pender (2000),"Earthquake resistant design of foundations:New construction", 12th world conferenceon EQ engineering, Auckland (N.Z.)Pfflai, S., U. and Menon, D. (2003),"Reinforced concrete design (SecondEdition)", Tata McGraw-Hill PublishingCompany Limited, New Delhi.Ricardo, D. and Susumu, I. (2000), "RecentDevelopment in the Understanding of International Journal of Engineering Sciences & Research Technology[634]
[Gupta, 4(4): April, 2015]ISSN: 2277-9655Scientific Journal Impact Factor: 3.449(ISRA), Impact Factor: 2.114Earthquake Site Response and AssociatedSeismic Code Implementations", 12th worldconference on EQ engineering, Auckland(N.Z.)18. Romo, F, Miguel, Manuel, J., Mendoza andSilivia, R., Garcia (2000), "Geotechnicalfactors in seismic design of foundations state of the art", 12tl world conference onEQ engineering, Auckland (N.Z.)19. Silval, F., Pedro (2003), "Seismic evaluationoffull-momentconnectionCISShttp: // ediret.com20. SF -16, "Explanatory handbook on IndianStandard code of practice for plain andreinforced concrete (IS 456:1978)", Bureauof Indian Standards, New Delhi.21. Teguh, M., Duffield, C. F., Mendis, P.A.and Hutchinson, G. L. (2006), "Seismicperformance of pile to pile cap connections:An investigation of design issues",Electronic Journal of Structural Engineering,6,8-18. International Journal of Engineering Sciences & Research Technology[635]
STRUCTURAL DESIGN FOR ECCENTRIC LOADING OF FOOTING Nidhi Gupta* *Assistant Professor, Department of Civil Engineering, RKDF Bhopal ABSTRACT Eccentric loading, in which vertical or inclined wall surrounds one or more sides of the soil mass beneath the footing, is one of th
ISSN: 2277-9655 [Gulati * et al., 7(4): April, 2018] Impact Factor: 5.164 IC Value: 3.00 CODEN: IJESS7 http: // www.ijesrt.com International Journal of Engineering Sciences & Research Technology [359] the data from feeding through the network. To avoid this, the sub-images have to be resized and then by finding
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“The Calcutta Chromosome” KKIMRC International Journal of Research in Education and Communication Technology (KKIMRC IJRECT) Print: ISSN- 2277-1212 Online ISSN:2277-1077 ENG M.Raja Ambedkar Restoration of Human Spirit in "The Hungry Tide” of Amitav Ghosh The
ISSN: 2277-9655 [Patil Jaya et al., 5(12): December, 2016] Impact Factor: 4.116 IC Value: 3.00 CODEN: IJESS7 http: // www.ijesrt.com International Journal of Engineering Sciences & Research Technology [493] Fig 4 General arrangement drawing for a typical Dual system In present work analysis of multi-storied building frame subjected to wind load is consider.
ISSN: 2277-9655 [Bahalkar* et al., 6(7): July, 2017] Impact Factor: 4.116 IC Value: 3.00 CODEN: IJESS7 http: // www.ijesrt.com International Journal of Engineering Sciences & Research Technology [448] Figure 4: Meshing of coil spring (SAE 9254) The CAD model of coil spring is fixed at its bottom end and load is applied vertically downwards as shown in
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