Lateral Load Tests Research Articles

Numerical derivation of CPT-based p–y curves for piles in sand

The formulations for the lateral load–displacement (p–y) springs conventionally used for the analysis of laterally loaded piles have been based largely on the back-analysis of the performance of small-scale instrumented piles subjected to lateral load. Although such formulations have been employed with much success in industry, their applicability to large-diameter piles, such as those used to support offshore wind turbines, is uncertain and has necessitated further research in this area. Moreover, with the growth in popularity of in-situ cone penetration tests (CPTs), there are demands for a theoretically supported direct method that can enable the derivation of p–y curves from the CPT end resistance (qc). In this paper, a numerical derivation of CPT-based p–y curves applicable to both small- and large-diameter laterally loaded single piles in sand is presented. Three-dimensional finite-element analyses are performed using a non-linear elasto-plastic soil model to predict the response of single piles in sand subjected to lateral loads. The corresponding CPT qc profile is derived using the same soil constitutive model by way of the cavity expansion analogue. An extensive series of computations of the lateral pile response and CPT qc values is then employed to formulate a direct method of constructing p–y curves from CPT qc values. The proposed method is shown to be generally consistent with existing empirical correlations and to provide good predictions in relation to the measurements obtained during lateral load tests on instrumented piles in an independent case study.

Lateral Dynamic Response and Effect of Weakzone on the Stiffness of Full Scale Single Piles

The determination of dynamic characteristics of soil-pile system by full-scale lateral dynamic pile load testing is an important aspect in the design of pile foundations subjected to dynamic/seismic loads. Field test results are very useful for validating existing linear/non-linear models, which are used to predict the dynamic stiffness and damping of the soil-pile system. This paper presents the results of field lateral dynamic load tests conducted at two different petrochemical complex sites in India and the measured dynamic constants of the soil-pile system. A 3D finite element analysis is performed using ABAQUS to predict the non-linear response of soil-pile system under dynamic lateral loads. The lateral stiffness estimated from the FE analysis shows good agreement with stiffness measured in the field tests. Dynamic analyses of single piles using improved Novak’s method were performed to study the effect of weak zone around the pile shaft on the lateral stiffness of the piles.

Nonlinear cyclic behavior of laterally loaded pile in cohesive soil

Pile foundations may be subjected to lateral dynamic loads due to different hazards, such as impact of ships on bridge piers or jetties during berthing, wave and wind actions on offshore structures, and seismic wave motion on different buildings. The beam on nonlinear Winkler foundation (BNWF) approach is widely employed for predicting the response of piles under lateral loading because of its simplicity and practical accuracy. p–y curves are employed to represent the nonlinear soil reactions within the framework of the BNWF approach. However, they are empirically obtained from limited full-scale field tests and are not unique, accounting only for the pile width and not its mechanical properties. On the other hand, the strain wedge (SW) method allows the assessment of three-dimensional (3-D) soil–pile interaction of laterally loaded piles by incorporating soil continuity and pile properties as well as soil properties. In this study, the nonlinear p–y curves generated by the SW model are implemented as the backbone curve of developed BNWF model to effectively account for different response features of the pile–soil system. These features include the soil and pile nonlinear behavior, cyclic degradation of soil stiffness and strength, formation of soil–pile gap, and radiation damping. Two case studies of cyclic lateral load tests for single piles are investigated to examine the effects of soil degradation and gap formation on the response of laterally loaded piles embedded in cohesive soil. The developed model is shown to be capable of representing different soil–pile interaction features observed in experiments. The predictions of the developed BNWF model are in good agreement with experimental results. Finally, a comprehensive parametric study is performed to compare the predictions of the SWM-based model of the pile response under cyclic loading with that obtained from the conventional p–y curve–based model for different pile cross-section configurations, mechanical properties (strength and stiffness), and soil strength–stiffness.

Effect of lateral static load on immediately restored implants: histologic and radiographic evaluation in dogs

The aim of this study was to evaluate the effect of lateral static load in immediately restored implants in the canine mandible. In 7 mongrel dogs, all premolars and the first molars were extracted bilaterally in the mandible. Two months after the extractions, 6 implants with sandblasted acid-etched surfaces were placed in each animal, 3 on each side. Randomly, two implants per side were immediately restored with an orthodontic expansion device that promoted lateral excessive static load (test group) or load (control) while the third implant of each side, remained submerged (unloaded group). These loaded devices were cleaned daily with chlorhexidine 0.12%, during the 4 months of study, when the animals were sacrificed and biopsies removed for histometric study. Intra-oral periapicals were made using positioners at the beginning and at the end of the study. Five implants from test group were lost in 3 dogs. Radiographically, there was a marginal bone loss of 3.68 ± 0.74 mm for the test group, 1.63 ± 0.2 mm for the control group and 0.45 ± 0.5 mm for the unloaded group. Histometrically, the percentage of bone-to-implant contact (BIC%) was 35.52 ± 7.32%, for the test group, 63.16 ± 5.16% for the control group and 42.33 ± 2.14% for the unloaded group. In conclusion, the excessive lateral static load negatively affected the behavior of peri-implant bone around immediate restored implants.

Seismic and Power Generation Performance of U-Shaped Steel Connected PV-Shear Wall under Lateral Cyclic Loading

BIPV is now widely used in office and residential buildings, but its seismic performance still remained vague especially when the photovoltaic (PV) modules are installed on high-rise building facades. A new form of reinforced concrete shear wall integrated with photovoltaic module is proposed in this paper, aiming to apply PV module to the facades of high-rise buildings. In this new form, the PV module is integrated with the reinforced concrete wall by U-shaped steel connectors through embedded steel plates. The lateral cyclic loading test is executed to investigate the seismic behavior and the electric and thermal performance with different drift angles. The seismic behavior, including failure pattern, lateral force-top displacement relationship, and deformation capacity, was investigated. The power generation and temperature variation on the back of the PV module and both sides of the shear wall were also tested. Two main results are demonstrated through the experiment: (1) the U-shaped steel connectors provide enough deformation capacity for the compatibility of the PV module to the shear wall during the whole cyclic test; (2) the electricity generation capacity is effective and stable during this seismic simulation test.

Numerical Analysis of Piles Under Cyclic Lateral Load

The paper presents the results to study the response of piles in homogeneous and layered soils subjected to quasi-static and cyclic lateral loading using numerical analysis. The analyses are carried out using three-dimensional finite element software, ABAQUS v6.10. Hypoelastic constitutive model is used to simulate the small strain nonlinear behavior of soil observed during the application of cyclic lateral load on piles. The bending moment and deflection responses computed from ABAQUS analyses are compared with the results obtained from the reported case histories of field pile lateral load tests and centrifuge tests. The favorable comparisons established that the three-dimensional numerical analysis can be effective to model complex soil–pile systems. Numerical analysis was also able to simulate a cement injected layer as a reinforcement body to the soft foundation soil, which can affect the pile response. The study was further extended to understand, the effect of flow of surrounding soil around the laterally-loaded piles on the response of piles.

Exploring influence of sectional flexural yielding on experimental pile response analysis and applicability of distributed plastic hinge model in inelastic numerical simulation for laterally loaded piles

This study used model pile load testing and numerical analysis to investigate the experimental analysis results of pile and soil responses for lateral load testing due to the flexural yielding of a pile, and to examine the applicability of the distributed plastic hinge model to the numerical simulation of inelastic pile response. A lateral load test on an aluminum model pile in sand was conducted as an analysis case. The pile was loaded to a large lateral pile-head displacement, a displacement under which some of the pile sections yielded and thus the pile had inelastic flexural deformation. The test results showed that before the pile yielded, the depth of maximum moment increased with increasing load due to soil nonlinearity; after the pile yielded, the depth of maximum moment varied less and the plastic region expanded upward and downward around this depth with increasing pile displacement. In deducing the responses of the pile and soil for the pile-soil system, the actual nonlinear flexural rigidity of the pile section built based on the bending test was essential to retrieve rational ones. In addition, the distributed plastic hinge model was shown to be effective to model the inelastic pile responses and capture the development of plastic zones in the pile.

하중기반 유한요소모델에 의한 FRP 보강 철근콘크리트 기둥의 비선형 해석

The aim of the current study is to develop a nonlinear isoparametric layered frame finite element (FE) analysis of FRP strengthened reinforced concrete (RC) beam or column members by a force-based FE formulation. In sections, concrete is modeled in the triaxial stress-strain relationship state and the FRP sheet is modeled as layered composite materials in two-dimension. The element stiffness matrix derived by the force-based FE has the force-interpolation functions without assuming the displacement shape functions. A lateral load test of RC column strengthened by GFRP sheets was analyzed by the developed force-based FE model. From comparative studies of the experimental and analysis results, it was shown to compare with the stiffness FE method that the force-based FE analysis could give more accurate predictions in the overall lateral load-deflection response as well as in nonlinear deformations and damages in the column plastic hinge region.

Retracted: Frozen Soil Strength Criteria for Lateral Pile Analysis

This paper presents a design approach to analyze the effects of lateral loads on piles embedded in a layered frozen soil profile. This design approach makes use of a commercially available computer program that uses p-y curves to model lateral pile loading and soil interaction. Shear strength and strain criteria for both fine- and coarse-grained frozen soil are presented for use in constructing p-y curves. These strength criteria are parameterized based on frozen soil temperature and load duration. Inuvik lateral pile load test results and deflections calculated using the strength criteria are compared. Deflections and moments are also calculated using the strength criteria for two Prudhoe Bay, Alaska, lateral pile load cases.

Seismic Resistance of Socket Connection between Footing and Precast Column

A new concept has been developed for connecting spread footings and precast columns in bridges. The socket connection is constructed by precasting the column, erecting it, and casting the reinforced concrete footing around it. This system saves construction time on site because, in little more than the time needed to construct the footing, both the column and footing can be constructed. Site erection is facilitated by the fact that the field tolerances are essentially unlimited. The longitudinal column bars are straight and are terminated with mechanical anchors. This arrangement improves constructability, because no bars cross the interface between the column and footing, and it provides better transfer of forces in the connection region than is possible with conventional bent-out longitudinal bars. The surface of the column is roughened to improve adhesion to the surrounding cast-in-place concrete. Axial-load tests demonstrated that the connection can resist column axial loads far above those expected in practice. Cyclic, lateral-load tests demonstrated that the seismic performance of the connection is at least as good as, if not better than, that of a comparable cast-in-place system. The recent deployment of the new system in a highway overpass provided both field experience and initial estimates of the potential time savings.

빔요소와 Rigid 링크를 이용한 수평하중에 대한 말뚝 거동 3차원 유한요소해석

The BNWF (Beam on Nonlinear Winkler Foundation) model is one of the simplest idealizations for a pile embedded in soil as it ignores the continuity of the soil. This method is difficult to model the behavior of pile group foundation subjected to lateral loading. The limitation can be overcome with the utilization of the finite element method (FEM) or finite different method (FDM) to represent a pile element embedded in a soil medium. Both the ground and piles are modeled with soild elements. The solid elements, which do not have rotational degree of freedom, is not appropriate for modeling piles. It can be overcome by substantially increasing the number of elements, which can be prohibitive for 3D modeling. This paper used the beam element and rigid link incorporated in the OpenSees to model the pile. The accuracy of the model is validated through comparison with lateral load test and BNWF analysis. It is shown that the method can capture the measured behavior accurately. It is therefore recommended to be used in group pile analyses.

Rocking response assessment of in-plane laterally-loaded masonry walls with openings

Finite element (FE) simulations of lateral loading tests on a full-scale masonry wall with an opening were processed to investigate the observed rocking response before and after strengthening. The lateral drift of the piers and spandrel panel was decomposed in a part associated with both bending and shear deformations and another part associated with rocking rotations of end sections. FE analysis results show that: (1) the ratio between rocking rotations of the spandrel panel and those of the piers can be predicted through a simple geometrical relationship; (2) overturning moment can induce significant axial force variations in piers, changing their lateral behaviour. A sensitivity analysis demonstrated that rocking response was not significantly affected by variations in fracture energies of masonry units and mortar, opposed to the case of individual solid masonry walls. Finally, a simplified analysis of individual piers and macro-element matrix analysis of the as-built sub-assemblage was performed. Several options in terms of pier effective heights, spandrel effective length, size/stiffness of spandrel–pier overlapping zones, and reduction of elastic properties have been tested against experimental and numerical results. It is shown that: (1) lateral drifts in uncracked elastic conditions can be predicted via equivalent frame models with rigid end offsets and different effective heights of piers, depending on their location and performance level considered; (2) reduction factors of elastic properties lower than those allowed by some national and international codes may be required to capture large rocking-induced lateral drifts.

Cyclic Lateral Load Test on T-Shaped Reinforced Concrete Columns

Based on the experiment of eight reinforced concrete T-shaped columns under low cyclic load, the factors which affect bearing capacity and seismic behavior, such as limb length, axial load ratio, stirrup ratio and the arrangement of longitudinal bars, etc., are analyzed. Tests results show that the bearing capacity of the columns increases, but the ductility is decreased with an increase of axial load ratio. The bearing capacity of T-shaped column increases when the web gets longer, while its deformability and ductility decrease. Besides, increase of stirrup ratio and longitudinal bars in the end of the web also have effect on the ductility of the columns.

Influence of masonry infill on the seismic performance of concentrically braced frames

This paper presents an experimental and analytical study to investigate the effect of masonry infill on the seismic performance of special Concentrically Braced Frames (CBFs). Cyclic lateral load tests are conducted on three half-scale specimens including two special CBFs with and without masonry infill and a moment resisting steel frame with masonry infill for comparison purposes. Companion analyses are performed to study the influence of masonry infill on the potential rupture of gusset plates and top-seat angle connections by using detailed FE models validated with experimental results. It is shown that the presence of masonry infill could increase the lateral stiffness and load carrying capacity of the special CBF by 33% and 41%, respectively. However, the interaction between masonry infill and the frame significantly increased the strain demands and failure potential of the connections. The results of the experimental tests and analytical simulations indicate that ignoring the influence of masonry infill in the seismic design process of CBFs results in a premature fracture of the connection weld lines and a significant reduction in the deformation capacity and ductility of the frame. This can adversely influence the seismic performance of the structure under strong earthquakes. The results of this study compare well with the damage observations after the 2003 earthquake in Bam, Iran.

Seismic behavior of a type of welded precast concrete beam-column connection

This paper describes testing of a typical practice in Mexico for connecting precast concrete members for moment-resisting frames using welded reinforcement. Cyclic lateral load testing of typical beam-column assemblies were conducted. The connections were also analyzed using a nonlinear analytical model. The results indicate that the welded reinforcement con- nection detail may result in brittle failure under cyclic loading. The authors recommend that emulative con- nections be used instead.

Evaluation of Lateral Interpretation Criteria for Drilled Shaft Capacity in Gravels

Representative interpretation criteria are examined in detail to evaluate the lateral response of drilled shaft foundations in gravels. A database of field lateral load tests is used for the analysis. The representative criteria are subdivided into absolute displacement, displacement as a function of shaft diameter, rotation limit, mathematical model, and graphical construction method. Comparison of these criteria shows that the initial elastic region ends at approximately 3–5 mm, 0.50 %B, and 0.08° rotation, which represent the serviceability limit state. The final region begins at about 25 mm, 2.5 %B, and 0.33° rotation, which represent the ultimate limit state. The graphical construction methods, QL and QS&W, are located within the transition region of the curve. Among these criteria, the displacement limits, QL, and QS&W methods demonstrate more reliable results. The typical load–displacement curves for lateral capacity in gravels are developed for engineering practical use. Further, recommendations for the use of these interpretation criteria are also given.

Seismic finite element simulation of concrete piles in harbour landing stages

Seven reduced-scale prestressed concrete (PC) pile specimens for landing stages simulating four levels of corrosion were tested to investigate their structural cyclic lateral load-carrying behaviour. Three corroded specimens were repaired using fiber-reinforced polymer (FRP) jacketing before testing. In this paper, the force-based fibre element (FFE) and the OpenSees software are used to analyse the seven PC pile specimens, achieving good corroboration with tests. Because the corrosion in such piles is horizontally asymmetric, the validated FFE models are used to execute 78 pushover analyses along various lateral directions to determine the multi-directional lateral strengths of the six corroded specimens. Based on the FFE analyses and experimental observations, this study makes design recommendations for FRP jacketing for use in repairing corroded landing stage PC piles. The FFE modelling is also extended to simulate the entire pile–soil system of an in situ pile lateral load test, validating its feasibility and accuracy for an entire full-size pile–soil system.

H형강 프레임으로 보강한 철근 콘크리트 골조의 내진성능 평가

This study proposed proposes a retrofitting method using an H-beam frame to improve the seismic performance of non-seismic designed reinforced concrete frames. To evaluate the seismic performance with the H-beam frames, a cyclic lateral load test was performed and the experimental result was compared with the bared frame, and a masonry infilled RC frame. The results was were analyzed regarding aspects of the load-displacement hysteresis behavior, effective stiffness, displacement ductility, and cumulative energy dissipation. AlsoIn addition, it was possible to prove both an increase of in the maximum load capacity, effective stiffness, and energy dissipation capacity using the H-beam frame.

Nonlinear Load-Deflection Behavior of Reinforced Concrete Drilled Piles in Stiff Clay

AbstractThe results of three full-scale lateral load tests of cast-in-drilled-hole RC piles are evaluated to provide insights into the soil-pile interaction behavior as represented by p-y curves (p = soil reaction/length; y = lateral pile deflection) spanning from elastic conditions to mobilization of the soil capacity. The test sequence enables evaluation of the diameter effects on the p-y behavior as a result of testing two otherwise similar specimens, but with different diameters (0.6 and 1.8 m), and evaluation of the head-fixity effects as a result of testing similar specimens (with a 0.6 m diameter) under flagpole and fixed-head conditions. A constrained exhaustive search procedure that facilitates data interpretation even in the presence of severe shaft nonlinearity is introduced, which was needed because the testing was performed to full structural failure conditions. The p-y curves obtained with the present test data differ from the predictions of a standard (American Petroleum Institute) model, i...

횡방향 가력실험 및 충격실험을 통한 강판콘크리트(SC) 전단벽의 감쇠비 평가

Steel plate concrete (SC) composite structure is now being recognized as a promising technology applicable to nuclear power plants as it is faster and suitable for modular construction. It is required to identify its dynamic characteristics prior to perform the seismic design of the SC structure. Particularly, the damping ratio of the structure is one of the critical design factors to control the dynamic response of structure. This paper compares the criteria for the damping ratios of each type of structures which are prescribed in the regulatory guide for the nuclear power plant. In order to identify the damping ratio of SC shear wall, this study made SC wall specimens and conducted experiments by cyclic lateral load tests and vibration tests with impact hammer. During the lateral loading test, SC wall specimens exhibited large ductile capacities with increasing amplitude of loading due to the confinement effects by the steel plate and the damping ratios increased until failure. The experimental results show that the damping ratios increased from about 6% to about 20% by increasing the load from the safe shutdown earthquake level to the ultimate strength level.