RESPONSE OF REINFORCED CONCRETE PILES INCLUDING SOIL-PILE INTERACTION EFFECTS

Transcription

1 October 12-17, 28, Beijing, China RESPONSE OF REINFORCED CONCREE PIES INCUDING SOI-PIE INERACION EFFECS S. imkatanyu 1, K. Kuntiyawichai 2, E. Spacone 3, and M. Kwon 4 1 Aitant Profeor, Dept. of Civil Engineering, Faculty of Engineering, Prince of Songkla Univerity, Songkhla, hailand 2 Aitant Profeor, Dept. of Civil Engineering, Faculty of Engineering, Ubonratchathani Univerity, Ubonratchathani, hailand 3 Profeor, PRICOS Department, Univerity of Chieti, Pecara, Italy 4 Aociate Profeor, Dept. of Civil Engineering, Gyeongang National Univerity, Gyeongnam, Korea uchart.l@pu.ac.th, kittiak.ubu@gmail.com, epacone@unich.it, and kwonm@nongae.gnu.ac.kr ABSRAC : Due to recent detructive earthquake, the lateral behavior of pile foundation have been extenively invetigated through experimental and numerical tudie. he main objective of thi work i to develop the frame model with lateral deformable upport for pile-oil ytem under cyclic lateral loading. hi propoed model i imple and computational efficient but capable of repreenting the alient feature of pile-oil ytem under cyclic lateral loading; including dragging force and gap formation along the pile-oil interface a well a hyteretic repone of urrounding oil and pile. he accuracy of the propoed model i verified through correlation tudie on full cale tet of Cat-In-Drilled-Hole (CIDH) pile partially embedded in coheionle oil. Reult from thee correlation tudie indicate that the propoed model can repreent well both on global and local hyteretic repone. KEYWORDS: Soil-Structure Interaction, Reinforced Concrete, Pile, Fiber Model, Cyclic oad, Nonlinear Frame Analyi.

2 October 12-17, 28, Beijing, China 1. INRODUCION Nowaday, both tructural and geotechnical engineer are challenged to deign and invetigate expenive and trategic tructure (e.g. high-rie building, offhore platform, multi-tory highway etc.) for extreme lateral loading (e.g. earthquake, guty wind, terrorit attack, etc.). Uually, pile foundation are ued to upport thee tructure. Conequently, the incluion of the oil-pile ytem into the numerical model i crucial for deign and analyi of thee tructure under extreme event. It i deirable that the pile foundation remain elatic under thee extreme loading. Such deire i to avoid the difficultie of uburface inpection and high cot of repairing the foundation damage. Neverthele, the bending moment induced by the deign eimic activity can be adequately large to caue flexural damage in the pile. Pot earthquake invetigation in recent earthquake have confirmed that pile foundation are prone to flexural damage from earthquake loading [1]. he flexural damage in pile foundation can reduce both tiffne and trength of the foundation; hence affecting it erviceability and exiting loading-capacity of the tructural ytem. Furthermore, it i imperative to conider the effect of oil-foundation ytem on eimic demand and tructural repone when the performance-baed methodology i ued in eimic deign of tructure. he main objective of thi paper are to preent the newly developed pile oil frame element and to ae the validity of the propoed model through correlation tudie on full cale tet on pile under lateral loading. he formulation of the pile oil frame element i baed on the principle of virtual diplacement. he o-called Winkler Foundation i employed to repreent the urrounding oil [2]. Furthermore, it i crucial to note that thi tudy emphaize only on oil-pile interaction in firm non-liquefiable oil induced by the inertia of the upertructure (inertial interaction). Kinematic interaction related to cattering of incoming eimic wave and effect of oil liquefaction are not included in thi tudy. Finally, the experimental data on full cale tet of Cat-In-Drilled-Hole (CIDH) pile partially embedded in coheionle oil i ued to ae the accuracy of the propoed model. Both global and local repone of the ytem are evaluated. It i noted that thi foundation type i frequently ued a upporting ytem of highway bridge, epecially in California. he main advantage of thi pile contruction i the cot aving aociated with the contruction of one large CIDH pile intead of multiple maller diameter driven pile, which mut be integrated through a pile-cap. 2. DISPACEMEN-BASED FIBER FRAME EEMEN WIH AERA DEFORMABE SUPPORS Figure 1 2-Node diplacement-baed fiber frame element with lateral deformable upport he 2-node diplacement-baed frame element with lateral deformable upport (e.g. oil) i hown in Fig. 1. he interaction between the frame and urrounding deformable medium are repreented by continuou lateral pring. he propoed frame element with lateral deformable upport i made of the following component: a 2-node frame, plu continuou lateral pring repreenting the urrounding deformable medium. he frame ection i dicretized into fiber. he element nodal diplacement U and the ection diplacement u(x) are alo indicated in Fig. 1. he ection deformation are grouped in the d ( ) { ( ) ( )} B x = εb x κb x where ε B( x) i the ection axial train and κ B ( x) i the ection curvature. he frame formulation i baed on the Euler-Bernoulli beam theory, neglecting the ection hear deformation. Baed on the mall deformation aumption, the ection deformation are related to the nodal diplacement through the compatibility relation

3 October 12-17, 28, Beijing, China ε B = du B dx and κ B B 2 2. he ection force conjugate of db (x) are B( x) = { NB( x) MB( x) } = dv dx D, where N B (x) and M B (x) are the frame ection axial load and bending moment, repectively. he element diplacement u(x) are expreed a function of the nodal diplacement U through the hape function N B ( x ) : u( x) = NB ( x) U (2.1) where N B ( x ) i the array containing the hape function of a two-node frame. hey are well-etablihed function that define a linear axial diplacement field and a cubic vertical diplacement field. Frame and lateral-upport compatibility are both enforced in the trong form. he ection and lateral-upport deformation are directly related to the nodal diplacement U through the following equation: d x = B x U; d x = B x U (2.2) B( ) B( ) ( ) ( ) where B ( x) = N ( x), B ( x) = N ( x) and are linear differential operator. B B B B ; B Element equilibrium i enforced in the weak form. Application of the principle of virtual diplacement, ubtitution of Eqn. 2.2 and ubequent elimination of the virtual nodal diplacementδ U, yield the following equilibrium tatement: B x D x dx + B x D x dx = P (2.3) ( ) ( ) ( ) ( ) B B where P i the nodal force vector conjugate of U; and ( x) D contain the lateral-upport force. If Eqn. 2.3 i rewritten in incremental form, the matrix form of element equilibrium become: K U = P P (2.4) where K i the element tiffne matrix, computed a: K = KB + K (2.5) where K B and K are the frame and the lateral-upport contribution to the element tiffne, repectively. K = B x k B x dx; K = B x k B x dx (2.6) ( ) ( ) ( ) ( ) B B B B k B (x) i the frame ection tiffne and k (x) i the lateral-upport tiffne. P i the array containing the element force: P= P + P (2.7) B and P = PB + P i the array containing the element initial force. P B i the frame contribution to the element force, and P i the contribution of the lateral upport: P = B x D x dx; P = B x D x dx (2.8) ( ) ( ) ( ) ( ) B B B he detail of thi model formulation can be found in imkatanyu and Spacone [3]. he general-purpoe finite element program [4] i ued to hot thi propoed element. 3. MONOONIC AND CYCIC p y CURVES of COHESIONESS SOIS In thi tudy, the oil urrounding a pile are modeled a 1-D pring continuouly placed along the pile length. Only the end-bearing pile embedded in coheionle oil i conidered in thi tudy. Baed on the model propoed by Reee et al. [5], the ultimate lateral reitance p of oil with depth can be computed from the u leer value provided by Eqn. 3.1 and 3.2. D( K K ) + z( K K ) K tanα p a p p p = γ z u 1 (3.1) + zk K + 1 tanφ inβ p coα

4 October 12-17, 28, Beijing, China ( 3 2 tanφ ) p = γzd K + K K K (3.2) u p p p z = z 5 o a p k p m b m D 3D 6 8 p u c z = z = z 4 z = z 3 z = z 2 z = z 1 Figure 2 Monotonic backbone p-y curve of and propoed by Reee et al [5]. 2 o 2 o where K = tan ( 45 + φ / 2 p ) i paive earth preure coefficient; K tan ( 45 φ / 2 a ) preure coefficient; K i at-ret earth preure coefficient; y Deeper = i active earth α = φ /2 o i angle defining the hape of failure wedge; β = 45 + φ / 2 ; γ i the effective unit weight of oil; z i depth from the ground urface; and D i the pile diameter. It i noted that Eqn. 3.1 account for the wedge- type failure near the urface while Eqn. 3.2 account for the plane-train failure at a great depth below the ground urface. he monotonic backbone p-y curve relating the oil deformation to oil preure are hown in Fig. 2 at variou depth. φ i effective internal friction angle; p u p d p d p u Figure 3 Cyclic repone of and he monotonic p-y curve of Fig. 2 erve a the envelope of the cyclic p-y curve a hown in Fig. 3. he hyteretic characteritic of the model developed by Arnold et al. [6] i modified for the propoed cyclic p-y model. hi propoed model can account for gapping and dragging apect oberved during in-itu tet on pile under cyclic lateral loading (e.g. Brown et al. [7]). he dragging force i activated only when the pile move through the gap. he value of the dragging reitance i taken a 3 % of the monotonic peak capacity a uggeted by Hutchinon et al. [8]. 4. CORREAION SUDIES ON CAS-IN-DRIED-HOE PIE FOUNDAION UNDER AERA CYCIC OADINGS he frame element with lateral deformable upport dicued above i employed to imulate both global and local repone of the pile-oil ytem under lateral loading. he fiber ection model i ued to decribe the repone of the pile ection. In thi tudy, the fiber ection i conited of 4 confined concrete fiber, 1

5 October 12-17, 28, Beijing, China unconfined concrete fiber, and 7 teel fiber. he uniaxial contitutive library developed by imkatanyu [9] i ued to model the hyteretic repone of each contituent fiber. In thi paper, one of the experimental data from a erie of full-cale CIDH pile tet by Chai and Hutchinon [1] i ued to evaluate the validity of the propoed frame model. hi pile i labeled a Chai-Hutchinon Pile #1. More reult of correlation tudie on thi tet erie are preented elewhere [11]. he geometry of thi pecimen i hown in Fig. 4. he pile wa ubjected to a contant axial compreion of 489 kn (correponding to approximately 1 % f c A g ) and a cyclic lateral tip-diplacement a hown in Fig. 5. he material propertie of concrete, reinforcing teel, and urrounding and were taken from the report by Chai and Hutchinon [1]. Axial oad ( P = 489 kn ) Cyclic Diplacement 5.48 m.81 m 13.5 D 2 D Dene Sand G.. kn γ = 18 3 m φ = 44 ranvere Reinforcement Varie Pile Section.46 m (D) 7-#7 (ongitudinal Reinforcement) f = 41 MPa Concrete: c Steel: f y = 421 MPa Concrete Bae-Slab Figure 4 Geometry and load of Chai-Hutchinon Pile #1 3 k 2 g i ip Diplacement (mm) 1-1 a b c d e f -2 h j -3 Figure 5 ip diplacement hitory of Chai-Hutchinon Pile #1 Fig. 6 (a) uperimpoe the tip load-diplacement repone from the experimental tet with the numerical reult obtained with the propoed model without dragging-gapping effect while Fig. 6 (b) compare the experimental reult with the numerical reult obtained with the propoed model with dragging-gapping effect. A expected, both model yield the ame trength. hi i due to the fact the ultimate oil preure of both model are computed baed on Eqn. 3.1 or 3.2. Negligence of dragging-gapping effect can reult in over-prediction of the hyteretic energy of the ytem. It i clear that the propoed model with dragging-gapping effect could repreent well the initial tiffne and the peak lateral load, which i eential for the overall trength of the tructural ytem. Furthermore, the propoed model with dragging-gapping effect could alo repreent well the hyteretic feature of the ytem uch a unloading-reloading branche, pot-peak trength degradation, and the hyteretic energy diipated during the loading cycle. l

6 October 12-17, 28, Beijing, China 15 1 Experimental Reult Numerical Reult without Dragging- Gapping Effect 15 1 Numerical Reult with Dragging-Gapping Effect Experimental Reult ip Force (kn) 5-5 ip Force (kn) (a) ip Diplacement (m) -1 (b) ip Diplacement (m) Figure 6 Experimental and numerical repone of Chai-Hutchinon Pile #1 Fig. 7 how the lateral diplacement profile of the pile at different loading cycle (the cycle number refer to the labeling of Fig. 5). he clear-cut change in the lope of diplacement profile are oberved. hee are aociated with the platic-hinge formation, epecially for large diplacement cycle. he lateral deflection are rather mall beyond the platic-hinge region; implying that the inelatic deformation of the pile i localized only within upper few diameter of the pile. When comparing the left (Fig. 7 (a)) and right (Fig. 7 (b)) deflection profile, one could oberve the ditinct feature of thee two deflection direction. he gap formation along the left deflection trend to be larger than that along the right deflection. hi feature wa alo oberved during the tet by Chai and Hutchinon [1]. Furthermore, it i intereting to note that thi feature wa not found when the dragging-gapping effect were not included in the numerical model cycle l j h f d b 1 cycle a c e g i k Depth (mm ) G.. z Deflection (m ) z G (a) eft Deflection -4-5 (b) Right Deflection Deflection (m ) Depth (mm ) Figure 7 ateral diplacement profile at different cycle: (a) left deflection; (b) right deflection 1 1 Depth (m ) G.. z Maximum Oberved Damage 1.25 m 3.8D 1.9 m (2.69D) Depth (m ) G.. z Maximum Oberved Damage 1.9 m (2.69D) 1.25 m 3.8D -4 a c e -5 (a) Moment g i k Moment (kn-m ) -4 a c e -5 g i k (b) Curvature Curvature (1/m ) Figure 8 Moment and curvature profile at different cycle

7 October 12-17, 28, Beijing, China Fig. 8 (a) and (b) how the moment and curvature profile of the pile at different loading cycle (the cycle number refer to the labeling of Fig. 5). A hown in Fig. 8, the depth-to-maximum moment (platic-hinge location) obtained with the propoed model i 1.25 m (3.8 D). hi value i complied well with the tet obervation of maximum damage to the pile at 1.9 m (2.69 D). Fig. 9 how the hyteretic repone of urrounding oil at variou depth. hee repone confirm that the dragging and gapping effect hould be conidered in order to appropriately cope with the problem of cyclic oil-pile interaction. p (kn/m ) (a ) z = m y (m ) p (kn/m ) (b ) z = y (m ) p (kn/m ) (c ) z = 1. m y (m ) Figure 9 Cyclic p-y repone at variou depth 5. CONCUSIONS In thi tudy, the implified model for analyi of ingle pile-oil ytem i propoed. hi model i a diplacement-baed frame fibre element with continuou lateral deformable upport. he o-called Winkler Foundation i employed to repreent the repone of the urrounding oil. he propoed model can account for dragging force and gap formation along the pile-oil interface a well a hyteretic repone of urrounding oil and pile. Experimental data from a full cale tet of the CIDH pile under cyclic lateral loading are ued to evaluate the ability of the propoed model. he correlation tudie indicate that the propoed model i capable of predicting both global and local repone of the pile-oil ytem depite the ue of rather imple one-dimenional p-y pring to repreent the urrounding oil. hi enhance the confidence on accounting for effect of oil-foundation ytem on eimic demand and tructural repone epecially when the performance-baed methodology i ued in eimic deign of tructure. 6. ACKNOWEDGEMENS hi tudy wa partially upported by the hai Minitry of Univerity Affair (MUA), by the hailand Reearch Fund (RF) under Grant MRG46819, by the National Science Foundation under Grant No. CMS-1112 by the Italian Minitry of Education, Univerity and Reearch (MIUR) under Cofin 22 and 24 Grant, and by SREAM Reearch Group. hi upport i gratefully acknowledged. Any opinion expreed in thi paper

8 October 12-17, 28, Beijing, China are thoe of the author and do not reflect the view of the ponoring agencie. he author would alo like to thank Prof. Y. H. Chai of the Univerity of California, Davi and Prof..C. Hutchinon of the Univerity of California, San Diego for providing the experimental data ued in thi paper. Special thank go to Dr. Paagorn Chaiviriyawong for hi fruitful dicuion on the theoretical apect. REFERENCES [1] Sitar, N. (1995). Geotechnical Reconnaiance of the Effect of the January 17, 1995 Hyogoken-Nambu Earthquake, Japan, UCB/EERC 95/1 Earthquake Engineering Reearch Center, Univerity of California, Berkeley, California. [2] Winkler, E. (1867). heory of Elaticity and Strength. H. Dominicu, Prague. [3] imkatanyu, S. and Spacone, E. (26). Frame element with lateral deformable upport: formulation and numerical validation. Computer and Structure. 84, no , [4] aylor, R.. (2). FEAP: Finite Element Analyi Program. Department of Civil and Environmental Engineering, Univerity of California, Berkeley, California. [5] Reee,.C., Cox, W.R., and Koop, F.D. (1974). Analyi of laterally loaded pile in and, he 6 th Offhore echnology Conference, Houton, exa. [6] Arnold, P., Bea, R.G., Idri, I.M., Reimer, R.B., Beebe, K.E. and Marhall, P.W. (1977). Study of oil-pile-tructure ytem in evere earthquake, Proceeding of the Annual Offhore echnology Conference, Houton, exa. [7] Brown, D.A., Morriion, C., and Reee,.C. (1988). ateral load behavior of pile group in and, Journal of Geotechnical Engineering. 114, no. 11, [8] Hutchinon,.C., Chai, Y.H., and Boulanger, R.W. (25). Simulation of full-cale cyclic lateral tet on pile, Journal of Geotechnical and Geoenviromental Engineering. 131, no. 9, [9] imkatanyu, S. (24). Deformation-baed uniaxial contitutive library for the inelatic analyi of RC tructure: fiber ection and beam column element, he 7 th International Conference on Concrete echnology, Kuala umpur, Malayia. [1] Chai, Y.H. and Hutchinon,.C. (1999). Flexural Strength and Ductility of Reinforced Concrete Bridge Pile. UCD-SR 99/2. Department of Civil and Environmental Engineering, Univerity of California, Davi, California. [11] imkatanyu, S., Kuntiyawichai, K., and Spacone, E. (28). Repone of reinforced concrete pile including oil-pile interaction effect, Engineering Structure (Under Review).