SOIL STRUCTURE INTERACTION STUDY ON PLANE BUILDING FRAME SUPPORTED ON PILE GROUP EMBEDDED IN COHESIVE SOIL

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 1, January 2017, pp , Article ID: IJCIET_08_01_099 Available online at &IType=1 ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed SOIL STRUCTURE INTERACTION STUDY ON PLANE BUILDING FRAME SUPPORTED ON PILE GROUP EMBEDDED IN COHESIVE SOIL PG CH.Hanumantha Rao Professor, Department of Civil Engineering, K L University, A. P, India ABSTRACT Background/Objectives: The main objective of this work is to determine the soil interaction of a plane building frame underpinned by pile groups which are embedded in cohesive soil (clayey soil).methods: The impact of Soil-Structure Interaction on response of a 4 storey framed Building underpinned by Pile group is reported in this paper. The four storey frame consists of three bays and columns of the frame supported by a pile group. The Pile group is presumed to be embedded in the Cohesive soil mass (clayey soil). The soil mass is represented by equivalent springs. The displacement of the building frame caused due to the deflection of the foundation with and without Soil Structure Interaction is analyzed using ANSYS. Findings: Soil non-linearity in lateral direction is indicated by the P-Y curve developed using Matlock equations. The soil properties which are used for clay (cohesive soil) are from the Triaxial Consolidated Undrained Compression Test on soil. Shear Force and Bending Moments at the base of the columns are determined for the frame which is analyzed with and without consideration of soil structure interaction. Key words: Building Frame, Cohesive Soil, Soil-Pile- Structure Interaction, Non Linearity, P-Y Curve Cite this Article: Lakshmi Pujitha V and CH.Hanumantha Rao, Soil Structure Interaction Study on Plane Building Frame Supported on Pile Group Embedded In Cohesive Soil. International Journal of Civil Engineering and Technology, 8(1), 2017, pp /issues.asp?jtype=ijciet&vtype=8&itype= =1 1. INTRODUCTION Lakshmi Pujitha V Student, Department of Civil Engineering, K L University, A. P, India The flexural rigidity of the super structure results in the soil settlement. In a Conventional Structural Design, the impact that is caused due to the settlement of the ground surface on the Framed structure supported by fixed base is ignored. The Structural Stiffness may have impact on the column loads and Moments distribution which willl be imparted to Foundation of Structure. Past reviews are however specified that interaction impact between soil & the Structure could be remarkable. Soil interaction 841

2 Lakshmi Pujitha V and CH.Hanumantha Rao analysis are previously described in various research such as Morri, Lee & Harrison [1971], Lee & Brown [1973], also in Deshmukh and Karmarkar [1991], Noorzaei [1994] Rao [1995], Dasgupta [1998], and Mandel[1999]. Generally those obtained loads due to foundation from the Analysis of the Structure without allowing the settlement of foundation leads to uneconomical structure, so it is avoided and the effect of interaction of Soil is considered in calculating the settlement of the building frame. This implies that we have to predict how the Structure respond to the deformation & what are the results of that bending to the functionality of building. In that respect, various analysis works are reported about the framed structures supported on the Pile groups. The main aim of the paper is to do the Analysis numerically using Finite element analysis ( Non Linear FEA) of the plane building Frame of four storey and three bays underpinned by the Pile groups placed in the cohesive soil (clay) under some Static load ( Centrally Concentrated Load). Here the requirement to the consideration of the Soil Structure Interaction in the Building Frame analysis is highlighted through comparing the Behavior of Building Frame acquired from Analysis of frame with and without consideration of SSI. 2. OBJECTIVE 1. Deriving p-y curves for cohesive soil by using Matlock equations. 2. Obtained graphs are used for modeling in ANSYS 3. METHODOLOGY 3.1. PROCEDURE FOR DEVELOPING P-Y CURVE 1. Computing Ultimate Soil Resistance, p u using p u = [ 3+( γ ' /c u )*z+(j/d)*z]c u D (1) 2. Computing deflection at the one-half of the Ultimate Resistance of Soil, y 50 using y 50 = 2.5*Ɛ 50 *D (2) 3. Developing the P-Y curve by using following expression p/p u = 0.5* (y/y 50 ) (3) where y 50 -deflection at the one-half of the ultimate resistance of soil. p u -ultimate resistance of soil p- Force/load y -Displacement c u -un drained Shear strength D- Diameter of pile J = 0.5 for clay (soft) = 0.25 for clay(medium) γ ' -Effective unit weight of the soil z -Soil depth Ɛ 50 - Strain at one half ultimate soil resistance The soil properties which are used for clay (cohesive soil)are from the Triaxial Consolidated Undrained Compression Test on soil. The diameter of the pile is assumed as 0.4m, the depth at which the clayey soil is 6m, undrianed shear strength is 116kN/m 2, J is a constant value 0.5 for soft clay, the dry density of the soil is 1.62 KN/m 3, strain at one half Ultimate Soil Resistance is obtained through the graph which is plotted between strain and deviator stress obtained from the Triaxial test. The curve thus obtained is shown in figure

3 Soil Structure Interaction Study on Plane Building Frame Supported on Pile Group Embedded In Cohesive Soil Figure 1 P-Y Curve 3.2. ANALYTICAL PROGRAM 3.2.1Analysis Program using a software ANSYS 12.1 The Analysis of a Modeled Building frame (4*3) is done using a software ANSYS 12.1 for following cases: The Frame underpinned with the fixed bases for calculating the SF & BM for a column, which was the general practice used called as Conventional Method. A Non Linear Analyses to calculate the Lateral and Vertical Displacements, shear forces, & bending moments in the frames. Figure 2 Modeled plane frame including pile Finite element modeling and analysis The non linear Analyses was done for three bay, four storeyed model Plane building frame supported on pile groups in a clayey soil (figure 2). Columns (C1,C2,C3,C4), beams, and the piles have been modeled by using 3D Elastic 2-Node Beam elements. Cap of a pile is modeled using 4-Noded Elastic shell 843

4 Lakshmi Pujitha V and CH.Hanumantha Rao elements. That cohesive Soil which is throughout an individual pile have modeled with Non linear Load Transfer curves(p-y curves) using COMBIN 39 element. The non linear analysis constitutive tutive Soil Models given by the equation 1,equation 2 and equation 3 are hired for the present problem. The p-y curve given by equation 1 were from the Matlock(1970) equation After analyzing the plane frame using ANSYS 12.1 the result is shown in figure 2 4. RESULTS AND DISCUSSIONS Figure 3 Y Component of Displacement The four storey three bay frame which is assumed to be supported by pile group and embedded in cohesive soil is analyzed using ANSYS in both the conventional and nonlinear FEA methods. The results for Shear Force, Bending Moments at base of all the columns are shown in figures 4,5 respectively. Figure 4 Variation Of Shear Force for the Columns From the figure 4 it is observed ed that the variation of Shear Force values from conventional method to Non linear FEA for the exterior columns of the frame are more when compared with the interior columns. Therefore, from obtained results, it is to know that the Soil Interaction consideration reduced Shear Force greatly when the comparison done with Frame Analysis having Fixed bases

5 Soil Structure Interaction Study on Plane Building Frame Supported on Pile Group Embedded In Cohesive Soil Bending Moments in the Frame under Center concentrated load have indicated in the figure 5. Figure 5 Variation Of Bending Moments for the Columns From those graphs, it can be perceived that the moments caused due to bending obtained by Conventional Method are always higher. Major difference in bending moment obtained by Conventional Method analysis and Non linear FEA to the plane Frame was nearly 31%. Here, it is to be noted regarding the bending moment for the 1st column of a plane frame obtained by various analysis methods although their difference in percentage is not high, they are important because values for Bending Moment are the multiples of the thousands. Therefore this represents that there is a need to the consideration for Interaction of soil for calculating design values in Building frame. 5. CONCLUSIONS 1. It is perceived that the Shear force(sf) and Bending moment(bm) values from the conventional method for the first column are 18.2% and 7.83% respectively are more than those from the non linear FEA. 2. It is perceived that the Shear Force(SF) and Bending Moment(BM) values when frame was analyzed without SSI for the second column are 24.2% and 22.7% respectively are more than those that is analyzed with SSI. 3. The above results shows that the Shear force (SF) and Bending moment (BM) values from the Conventional Method for the third column are 22.07% and 31.0% respectively are more than those from the non linear FEA. 4. It is seen that the Shear force(sf) and Bending moment(bm) values from the Conventional Method for the fourth column are 29.8% and 19.6% respectively are more than those from the non linear FEA. REFERENCES [1] Ravikumar C Reddy And Gunneswara T D Rao " Study Of Soil Interaction In A Model Buildingframe With Plinth Beam Supported By Pile Group" International Journal Of Advanced Structural Engineering 2012 [2] Sushma Pulikanti, Pradeep Kumar Ramancharla "Ssi Analysis Of Framed Structures Supportedon Pile Foundations: A Review" " Frontier In Geotechnical Engineering (Fge) Volume 2 Issue 2, June 2013 [3] S.A.Rasal, Chore H.S "Interaction Of Frame With Pile Foundation" Iosr Journal Of Mechanical And Civil Engineering (Iosr-Jmce) Issn: , Pp:

6 Lakshmi Pujitha V and CH.Hanumantha Rao [4] Dr. C. Ravi Kumar Reddy, Dr. M. Anjaneya Prasad "Modeling Of Displacements In Building Frame On Pilegroups" International Journal Of Earth Sciences And Engineering 2015 [5] C. Ravi Kumar Reddy, And T. D. Gunneswara Rao, Effect Of Rigidity Of Plinth Beam On Soil Interaction Of Modeled Building Frame Supported On Pile Groups, Civil Engineering Dimension, Volume No. 16, Issue No.1, Pp.8-17, [6] D.M. Wood, A. Crew, And C. Taylor, Shaking Table Testing Of Geotechnical Models, Int. J. Phys. Modell. Geotech., Volume No.1, Pp.1-13, [7] H.S. Chore, And R.K. Ingle, Soil- Structure Interaction Analysis Of Building Frames- An Overview, J. Struct. Eng. Serc, Volume No.34, Issue No. 5, Pp , [8] Deshmukh Am, Karmarkar Sr (1991) "Interaction Of Plane Frames With Soil" In Proceedings Of Indian Geotechnical Conference, 1st Edn., Surat, India,Pp [9] Ingle Rk, Chore Hs (2007) "Soil-Structure Interaction Analysis Of Building Frames -An Overview." J Struct Eng, Serc 34(5): [10] Kulhawy Fh, Mayne Pw (1990) "Manual On Estimating Soil Properties For Foundation Design", 5-1st Edn. Epri Rep El-6800, Electric Power Research Institute, Palo Alto, Pp 5 25 [11] Desai, C. S. Kuppusamy, T. And Allameddine, A. R. ʺPile Cap Pile Group SoilInteraction.ʺ Journal Of Structural Division, Asce, 107 (5), , [12] Focht, J. A., And Koch, K. J. ʺRational Analysis Of The Lateral Performance Of Offshore Pile Groups.ʺ Fifth Annual Offshore Technology Conference, Houston, Texas, , [13] Garassino, A. ʺSome Developments On Laterally Loaded Piles With Particular Reference To P Y Sub Gradereaction Method.ʺ Proceedings of The 4th International Conference On Piling And Deep Foundations, A.A. [14] Balkema, Rotterdam, The Netherlands, , 1994.Hetenyi, M. ʺBeams On Elastic Foundation.ʺ The Universityof Michigan Press, Ann Arbor, Michigan, [15] Horvath, J. S. ʺSimpified Elastic Continuum Applied To The Laterally Loaded Pile Problem Part 1: Theory.ʺ Laterally Loaded Deep Foundations: Analysis And Performance, American Society For Testing And Materials, ,