Instrumentations, Pile Group Load Testing, and Data Analysis Part II: Design & Analysis of Lateral Load Test. Murad Abu-Farsakh, Ph.D., P.E.

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1 Instrumentations, Pile Group Load Testing, and Data Analysis Part II: Design & Analysis of Lateral Load Test Murad Abu-Farsakh, Ph.D., P.E. Louisiana Transportation Research Center Louisiana State University

2 Acknowledgement Financial Support: FHWA under IBRD program, LTRC and LA DOTD Coworkers: Binay Pathak Xinbao Yu

3 Part II: Design & Analysis of Lateral Load Test Outline Objectives of the lateral load test Overview of M19 Eastbound pier Design of the Lateral Load Test Results and Analysis of Lateral Load Test Comparison with FB-MultiPier Analysis Conclusions

4 Objectives of Lateral Load Test Evaluate the lateral behavior of battered pile group, Validate the FB-MultiPier analysis for predicting the performance of battered pile group foundation systems under lateral loading, Develop (or back-calculate) p-y curves and p- multipliers for use in the analysis and design of battered pile group foundations for bridges build in similar soil conditions.

5 Location of I-1 Twin Span Bridge 5.4 mile long 3 ft east of current bridge Source: Volkert Construction, LA DOTD

6 Overview of I-1 Twin Span Bridge Old Bridge New Bridge M Marine Traffic Source: Volkert Construction, LA DOTD

7 Overview of I-1 Twin Span Bridge M19 Pier

8 Overview of M19 Pier (Eastbound) Footing size: 44 ft x 42.5 ft x 7 ft Total: 24 battered pile (batter angle of 1:6) Size: 36 square PPC piles. 11 ft long Embedded pile length: ~87 ft Water depth: 11 ft

9 Soil Profiles: Soil Boring & CPT Soil Description m.c, L.L. and P.L Cu (kpa) Cone Tip Resistance qc (tsf) Probability of soil type (%) Silty clay, stiff Clay, stiff Silty clay, soft Clay, medium Sand, medium-dense Clayey sand, medium-dense Clayey 6 Silty clay, stiff Clay, medium Silty Depth (ft) Clay, very stiff Silty clay, stiff Sandy silt, stiff Clayey sand, very stiff Sand, very dense 1 12 m.c. P.L. L.L Clay, stiff Clay sand, medium dense Clay, very stiff Clay, stiff Silty sand, medium-dense Sand, very dense Sand, very dense Medium to stiff gray and tan silty clay to clay soil Sandy with silt and sand pockets and seams Cu qc SPT-N Rf Medium 18 dense 18 light gray sand 18 was noted between ft to 58 ft 2 Piles tip on stiff silty clay layer Standard Penetration Test (N) 14 Friction Ratio Rf (%) 14

10 Layout of Instrumented Piles at M19 Eastbound Pier 8 selected piles were instrumented with MEMS In-Place (IPI) inclinometers To measure the lateral deformation profile Load 12 selected piles were instrumented with strain gauges Load To measure the axial loads and moments. IPI, Sister Bar strain gauges

11 Installation of Piles: Sister Bar Strain Gauges For 12 selected piles 2 pairs of strain gauges were installed at 16 ft and 21 ft from the top of the pile. 16 ft 5 ft

12 Installation of Piles: MEMS In-Place Inclinometers below pile top below pile top 25'11" solid section 1-12' after pile cutoff 5' below SG1 below pile top below pile top below pile top below pile top IPI Sensor For 8 selected piles 6 MEMS IPI sensors were install at depths of 5, 15, 25, 35, 45, and 65 ft from bottom of pile cap.

13 Design of Lateral Load Test at M19 Piers Westbound Eastbound 44 Live End Jacking 68 6 Dead End Anchorage

14 Design of Lateral Load Test at M19 Pier Target maximum lateral load: 2 kips Eastbound Pier: designed as dead-end anchorage Westbound pier: designed as live end for jacking load system Load applied using high strength low relaxation two 19-strand tendons (.62 in 2 each) run through the westbound and eastbound footings, The eastbound footing and westbound footing were pulled towards each other using two 6 ton hydraulic jacks,

15 Design of Lateral Load Test at M19 Pier Data acquisition system: was temporary assembled, Automated laser survey system: used to monitor the horizontal movements of footings and bent caps of the two M19 piers, as well M17, M18 and M2 piers.

16 Setup of Lateral Load Test at M19 Piers Westbound Eastbound Barge

17 Setup of Lateral Load Test at M19

18 Setup of Lateral Load Test at M19

19 Setup of Lateral Load Test at M19 Westbound 6-ton Jack Dead End Anchorage Eastbound Live End Jacking Systems 19-strand tendon (.62 in2 each) Water 19-strand Pressure tendon Cells

20 Setup of Lateral Load Test at M19 Data loggers Monitoring

21 Setup of Lateral Load Test at M19 Pier Survey Prism Automated Laser Survey System

22 Setup for Lateral Load Test at M19 Pier Criterion to stop the loading at any time: 1) If the maximum lateral displacement of the M19 westbound bent cap reaches 3/4 in., 2) If the maximum tension strain change at the top two strain gages in pile 8 reaches 16 microstrains, corresponding to a maximum negative moment of 75 ft-kips. However, the test was unloaded earlier at a maximum applied load of 187 kips when the stroke in one 6-ton jack reached its maximum.

23 Loading-Unloading-Reloading Schedule No. Lateral Load (kips) per cable Total Lateral Load (kips) Load Duration (min) No. Lateral Load (kips) per cable Total Lateral Load (kips) Load Duration (min) Pre-load Cut strands 3

24 Results: Profiles of Lateral Deformation with Load Displacement (in) Displacement (in) Depth below pile cap (ft) st row / Pile 11 Load 57 kips 77 kips 97 kips 118 kips 158 kips 1745 kips 187 kips Depth below pile cap (ft) nd row / pile 6 Load 57 kips 77 kips 97 kips 118 kips 158 kips 1745 kips 187 kips 65 65

25 Results: Profiles of Lateral Deformation with Load Displacement (in) Displacement (inch) Depth below pile cap (ft) rd row / pile 7 Load 57 kips 77 kips 97 kips 118 kips 158 kips 1745 kips 187 kips Depth below pile cap (ft) th row / pile 8 Load 57 kips 77 kips 97 kips 118 kips 158 kips 1745 kips 187 kips 65 65

26 Results: Profiles of Lateral Deformation with Load 2 16 Lateral Load (kips) st row 2 nd row 3 rd row 4 th row Pile Position 1st row / pile 11 2 nd row / pile rd row / pile 7 4 th row / pile 8 E1 E Pile Displacement (inch)

27 Results: Load versus Strains Load vs. Strain - M19 Pile #4 2 SG4-1A Strain Gage Readings (microstrains SG4-1B SG4-2A SG4-2B Load (kips) Load vs. Strain - M19 Pile #9 Strain Gage Readings (microstrains SG9-1A SG9-1B SG9-2A SG9-2B Load (kips)

28 Lateral Behavior of Piles If we consider piles as flexible elastic beams and using the beam on elastic foundation theory: The lateral behavior of the piles can be evaluated by solving the following differential equations of deflection (or rotation) curves: 2 d y Moment :M z = EI 2 dz = EI d dz Shear : V z = EI 3 d y 3 dz = EI 2 d 2 dz Soil reaction : P z = EI 4 d y 4 dz = EI 3 d 3 dz

29 Interpretation of Lateral Load Tests of Piles Existing Methods of Data Interpretation: From Inclinometer Readings From Strain Gauges Readings High order polynomial curve fitting (Nip & Ng, 25) Brown least square error method (Brown 1994) High order polynomial curve fitting (Nip & Ng, 25) Weighted residual method (Wilson, 1998) Energy Method (Lao & Jen, 23) Cubic Spline (Dou & Byrne, 1996) Piecewise polynomial curve fitting (Matlock & Ripperger, 1956)

30 High-Order Polynomial Curve Fitting The shape of soil reaction profile (P z ) is assumed to follow a 4 th order polynomial function (Nip & Ng, 25) as follows: P z = a z b z 2 c z Integrating the above equation three times: 3 d z 4 z = ao a1 z a2 z a3 z a4 z a5 z a6 z a 7 z 7 The coefficients a o to a 7 were determined by fitting the measured rotation profiles obtained from IPI at different load increments using reduced chi-square minimization of residual error regression analysis.

31 High-Order Polynomial Curve Fitting Once the rotation profile is fitted into a function, The moment, shear force, and soil reaction profiles can then be deduced by differentiating the rotation equation and multiplying the result by EI : M z = E c I c (a 1 2a 2 z 3a 3 z 2 4a 4 z 3 5a 5 z 4 6a 6 z 5 7a 7 z 6 ) P z = E c I c (6a 3 24a 4 z 6a 5 z 2 12a 6 z 3 21a 7 z 4 ) I c : E c : I E solid(no void) 139,968 in 57, f c c, f c 8, psi, 4, I 128,475 in Hollow(with void) E c psi 4

32 High-Order Polynomial Curve Fitting Depth below pile cap (ft) Rotation (radian) st row / pile 11 Depth below pile cap (ft) Displacement (in) st row / pile 11 y dz Load 1745 kips measured displacement calculated displacement 7 7

33 High-Order Polynomial Curve Fitting Rotation (radian) Displacement (in) th row / pile th row / pile 8 Depth below pile cap (ft) Depth below pile cap (ft) y dz Load 187 kips calculated displacement Line/Scatter Plot 1

34 High-Order Polynomial Curve Fitting Depth below pile cap (ft) Moment (kips-ft) st row/ Pile 11 Load 57 kips 77 kips 97 kips 118 kips 1745 kips 187 kips M z = EI d dz Depth below pile cap (ft) Moment (kips-ft) Bending Moments 4 th row / Pile 8 Load 57 kips 77 kips 97 kips 118 kips 158 kips 1745 kips 187 kips

35 High-Order Polynomial Curve Fitting 2 2 3rd row / Pile 7 Moment at SG I location 4 th row / Pile 4 Moment at SG I location Load (kips) 8 Load (kips) 8 4 Moment Inclinomter Moment Strain gague Moment 4 Moment Inclinomter Moment Strain gague Moment Moment (kips-ft) Moment (kips-ft) Bending Moments

36 High-Order Polynomial Curve Fitting % of Latera Load Transferred to Axial Load st row 2 nd row 3 rd row 4 th row Pile 1 Pile 4 Pile 7 Pile 9 Pile 11 Pile 12 % of Latera Load Transferred to Axial Load st row 2 nd row 3 rd row 4 th row Pile 1 Pile 4 Pile 8 Pile 9 Pile 11 Pile 12 Pile Lateral Load (kips) Lateral Load (kips) Axial Load

37 High-Order Polynomial Curve Fitting Depth below pile cap (ft) soil reaction/lenght (kips/ft) Soil Reaction P z Load 57 kips 77 kips 97 kips 118 kips 158 kips 1745 kips = EI 3 d 3 dz

38 M 19 modeled with: FB-MultiPier Analysis 24 battered piles - discrete elements Pile cap (footing) - linear shell elements Shear wall - linear bending elements Two pier columns - linear bending elements Cantilever bent - linear bending elements Soil input parameters: Soil boring/lab test data, S u -UU, 5, k, (from SPT - sand) CPT data, S u -CPT (N kt =15), 5, k, Cantilever Bent Shear Wall Pier columns Pile Cap Batterd Piles

39 Soil-pile Interaction: FB-MultiPier Analysis Was modeled both vertically and horizontally with nonlinear p-y, t-z, and q-z curves, The pile group effect was initially considered through using p-multiplier assigned for different pile rows. Summary of Input Parameters of p-y Curves Used in FB-MultiPier Soil type Soil stiffness Soil location Parameters Model (reference) Sand Clay Loose dense Soft/medium stiff Stiff Above groundwater table k O Neill and Murchison Below groundwater table k Reese et al. (2) Above groundwater table s u, 5 O Neill and Gazioglu Below groundwater table s u, 5 Matlock (1) Above groundwater table s u, 5 Reese and Welch Below groundwater table s u, 5, k Reese et al.

40 Comparison with FB-MultiPier Analysis Lateral Deformation (in) Lateral Deformation (in) Depth below pile cap (ft) Lateral Load = 187 kips Pile 8 (boring) Pile 8 (CPT) Pile 8 (CPT, no group effect) Pile 8 (IPI measurement) Pile 8 (boring, no group effect) Pile 8 (polynomal derived) Depth below pile cap (ft) Lateral Load = 187 kips Pile 4 (boring) Pile 4 (CPT) Pile 4 (CPT, no group effect) Pile 4 (IPI measurement) Pile 4 (boring, no group effect) Pile 4 (polynomal derived) 7 7 Lateral Deformations

41 Comparison with FB-MultiPier Analysis Deformation (in) Soil Boring CPT (Nk=15) Pile cap (measured E1) Pile cap (measured E2) Lateral Load (kips) M19W E1 E2 M19E Lateral Deformations

42 Comparison with FB-MultiPier Analysis 2 16 Lateral Load (kips) M19W E1 M19E Cap movement E1 E2 FB-MultiPier_CPT (no group effect) FB-MultiPier_CPT FB-MultiPier_Soil boring FB-MultiPier_soil boring (no group effect) Polynomial derived E2 Pile Cap Movement (in) Lateral Deformations

43 Comparison with FB-MultiPier Analysis 25 Pile 8 (Soil Boring) 2 Pile 1 (Soil Boring) Micro-strain 15 1 Pile 8 (CPT,Nk=15) Pile 1 (CPT,Nk=15) Pile 8 (Measurement) Pile 1 (Measurement) 16 micro-strain Lateral Load (kips) Load versus Tension Strains

44 Comparison with FB-MultiPier Analysis Moment (kips-ft) Moment (kips-ft) D epth b e low pile cap (ft) Load 97 kips 1745 kips FB 97 kips FB 1745 kips SG 97 kips SG 1745 kips 4 th row/ Pile 4 D epth b e low pile cap (ft) Load 97 kips 1745 kips FB 97 kips FB 1745 kips SG 97 kips SG 1745 kips 4 th row/ Pile 12 Bending Moments

45 Comparison with FB-MultiPier Analysis -2 1st row / pile 11 (FB-1) Axial Load (kips) SG level SG 1 SG 2 FB at SG1 FB at SG Lateral Load (kips) Axial Load

46 Back-Calculated P-Y Curves Development of the rotation profile (θ z ) Derivation of the displacement profiles (y) Derivation of soil resistance profiles (P z ) Construction of p-y curves for selected depth Depth below pile cap (ft) Rotation (radian) st row / pile y Lateral displacement Profile Ground level P Soil lateral resistance Profile Soil resistance (P) P-Y Curve Lateral Displacement, y

47 Back-Calculated P-Y Curves Soil resistance force (kips/ft) Pile Position st row / pile nd row / pile rd row / pile th row / pile Displacement (in) Soil resistance force (kips/ft) Pile Position st row / pile nd row / pile rd row / pile th row / pile Displacement (in) 5 ft below GL 1 ft below GL

48 Back-Calculated P-Y Curves Soil resistance force (kips/ft) Pile Position 1 st row / pile 11 2 nd row / pile 6 3 rd row / pile 7 4th row / pile Displacement (in) Soil resistance force (kips/ft) Pile Position.5 1 st row / pile nd row / pile 6.3 3rd row / pile 7.2 4th row / pile Displacement (in) 15 ft below GL 2 ft below GL

49 Conclusions A unique lateral load test was designed and successfully conducted at M19 pier. The max applied load = 187 kips, The max. lateral deformation of M19 pile cap, from laser survey, was.67 in, which is 5% of the value predicted using the FB-MultiPier analysis, A high order polynomial curve fitting of IPI measurements was used to derive the profiles of lateral deformation, bending moment, shear and soil reaction, The FB-MultiPier analysis based on both soil boring data or CPT overpredicted the lateral cap movements. The use of S u -CPT yields a better prediction than S u -soil boring,

50 Conclusions Good agreements was obtained between the backcalculated moments deduced from the curve fitting of IPI and moments calculated from strain gauge measurements, The moments developed at the ground level were about 5-55% lower than that at the bottom of pile cap, and the depth to the zero moment increases as the load increases, The FB-MultiPier moment profiles have larger positive and negative moments, and the depth to the peak negative moment is shallower, as compared with the backcalculated moment profiles from IPI measurements.

51 Conclusions The measured axial loads on inner row piles (i.e., 2 nd and 3 rd rows) are higher than piles in the other two rows (i.e., 1 st and 4 th rows), Analysis of back-calculated p-y curves for piles at different row locations showed no evidence of group effect, i.e., the p-multiplier of 1 can be used for all piles, LIMITATIONS: The derived moments, shears and p-y curves were based on single, double and triple differentiating of inclination ( ) function can lead to accumulative of errors. M z = EI d dz, V z = EI 2 d 2 dz, P z = EI 3 d 3 dz

52 THANK YOU Questions