Reinforced Concrete Piles Research Articles

Nonlinear soil and pile behaviour on kinematic bending response of flexible piles

In recent years kinematic interaction of piled foundations under seismic loading has been extensively researched from both an experimental and a numerical viewpoint. With regard to numerical aspects, most literature studies implement simplified constitutive models to describe soil and pile behaviour despite current availability of sophisticated constitutive models for both materials. The use of advanced constitutive models is limited in practice due to the difficulty in calibrating several constitutive parameters and the high computation demand which is generally required, particularly if a 3D continuum approach is selected for the analysis. To overcome some of the difficulties above and achieve a better understanding on kinematic response of piles under strong earthquakes, the capability of an advanced but still user-friendly kinematic hardening constitutive soil model has been investigated. The model derives from the classical Von Mises failure criterion with the addition of isotropic and kinematic hardening components to better represent soil response under cyclic loading.Dynamic 3D finite element (f.e.) analyses were performed in the time domain through a simple scheme of a single pile embedded in a soil deposit made of two cohesive layers. The parametric study elucidates the role of soil nonlinearity (stiffness degradation, hysteresis, soil plasticization) on pile kinematic bending response in respect of the adopted input signal, mobilized transient and permanent shear strain developed in the soil layers. For some accelerometric inputs the diffuse plasticization of the soil around the pile leads to compute high kinematic bending moments especially in soil deposits with the upper layer made of low-plasticity index soft clay. Finally, pile nonlinearity has also been considered by implementing bending moment-pile curvature relationships typical of reinforced-concrete piles.

Numerical Analysis of Reinforced Concrete Piles under Blast Loads

Pile foundations are commonly used as foundation systems for high-rise buildings and bridges. This paper uses a fully coupled three dimensional numerical modelling procedure to study the performance of pile foundations subjected to ground shocks induced by surface explosions. The comprehensive numerical model includes the pile, surrounding soil, air and the explosive. Appropriate material models are incorporated and dynamic non-linear analysis is carried out using finite element techniques. The soil in which the pile is buried could influence the blast performance of the pile. A parametric study is hence carried out to evaluate the effects of soil properties of density, friction angle, cohesion and Poisson’s ratio on the blast performance of the pile. It is found that density and cohesion of soil have significant effects on the deflection of the pile under blast loading. Poisson’s ratio has some effect, but effect of the soil friction angle is not very significant. The findings of this study will serve as a benchmark reference for future analysis and design of pile foundations to blast loading.

Evaluation of Maintained Load Test (MLT) and Pile Driving Analyzer (PDA) in Measuring Bearing Capacity of Driven Reinforced Concrete Piles

Results of several full scale RC (reinforced concrete) pile load tests were studied and analyzed to create a comparison between the MLT (maintained load test) and PDA (pile driving analyzer) methods. The ultimate pile capacities derived from analysis of PDA were consistently higher than results from the MLT. A coefficient of 0.9 or a 10% reduction is suggested to be applied to values derived from PDA. It is also observed that the longer the time interval, the greater the shaft friction contribution is towards the pile capacity.

Use of the Impact-Echo Method for Analyzing the Integrity of Driven Reinforced Concrete Piles

The limitations of using the sonic echo method for evaluating the integrity of driven concrete piles with near-surface flaws are examined. Criteria for detecting pile flaws in a compact region are obtained. It is shown that it is possible to use the multiplicative impact-echo method for determining the length of a pile with a near-zone flaw.

Verification of the Vertical Bearing Capacity of a Reinforced Concrete Pile

This paper deals with the modeling of the load test of vertical resistance of reinforced concrete piles. The pile is a part of a group of piles with reinforced concrete heads. The head is pressed with steel arches of a bridge on highway Jablonov - Studenec. Pile model is created in ANSYS with several models of foundation having properties found out from geotechnical survey. Finally some crucial results obtained from computer models are presented and compared with these obtained from experiment.

Corrosion Activity on CFRP-Strengthened RC Piles of High-Pile Wharf in a Simulated Marine Environment

We report test results from an experimental study to investigate the effectiveness of carbon fiber-reinforced polymer (CFRP) against reinforcing steel bar corrosion. Twelve reinforced-concrete pile specimens of 180 mm square by 1,600 mm long were cast. Three pile specimens were corroded to 5% steel mass loss and then strengthened with CFRP sheets; four specimens were strengthened by using CFRP sheets, whereas the remaining five specimens were not strengthened. The specimens were placed in a simulated marine environment, and corrosion was induced by an impressed current technique. At different theoretical corrosion degrees, nondestructive tests were performed to investigate the corrosion activity of the pile specimens, and destructive tests were performed to determine reinforcing steel bar mass loss. Based on the findings, the effectiveness of the CFRP-strengthened RC piles under aggressive marine environmental conditions was established.

Model verification and assessment of shear-flexure interaction in pile foundations

Fiber models have been developed and applied to various structural elements such as shear walls, beams and columns. Only scarcely have fiber models been applied to circular foundation systems such as cast in drilled holes shafts (CIDH). In pile foundations with constraint head boundary conditions, shear deformations can easily contribute to the lateral pile response. However, soil structure interaction formulations such as the p-y method, commonly used for lateral pile design, do not include structural shear deformations in its traditional derivation method. A fiber model that couples shear and axial-bending behavior, originally developed for wall elements was modified and validated on circular cross sections (columns) before being applied to a 0.61 m diameter reinforced concrete (RC) pile with fixed head boundary conditions. The analytical response was compared to measured test results of a fixed head test pile to investigate the possible impact of pile shear deformations on the displacement, shear, and moment profiles of the pile. Results showed that shear displacements and forces are not negligible and suggest that nonlinear shear deformations for RC piles should be considered for fixed-head or similar conditions. Appropriate sensor layout is recommended to capture shear deformation when deriving p-y curves from field measurements.

Optimal Force-Based Beam-Column Element Size for Reinforced-Concrete Piles in Bridges

AbstractThe nonobjective disadvantages of the force-based frame element, such as the nonobjective curvature prediction, have been discussed by many researchers. The trial-and-error method is commonly used to determine element size, but it could cost tremendous computational efforts. This paper proposes and analytically studies the optimal element size for reinforced-concrete piles for bridges when using force-based beam elements. In this study, the relationship between the optimum element size and integration point number is investigated, and the equivalent plastic hinge length is used and correlated to the optimal element size, on the basis of which the moment-curvature and force-displacement responses are objective and the soil effects on the pile response could be simulated sufficiently as required. The results of a case study show that both the local and global responses can be very well predicted, and the nonobjective disadvantage of the force-based element could be eliminated using the proposed opti...

Response of a RC pile group in liquefiable soil: A shake-table investigation

Soil liquefaction induced by earthquakes frequently cause costly damage to pile foundations. However, various aspects of the dynamic behavior and failure mechanisms of piles in liquefiable soils still remain unclear. This paper presents a shake-table experiment conducted to investigate the dynamic behavior of a reinforced-concrete (RC) elevated cap pile foundation during (and prior to) soil liquefaction. Particular attention was paid to the failure mechanism of the piles during a strong shaking event. The experimental results indicate that decreasing the frequency and increasing the amplitude of earthquake excitation increased the pile bending moment as well as the speed of the excess pore pressure buildup in the free-field. The critical pile failure mode in the conducted testing configuration was found to be of the bending type, which was also confirmed by a representative nonlinear numerical model of the RC pile. The experimental results of this study can be used to calibrate numerical models and provide insights on seismic pile analysis and design.

Concrete integral abutment bridges with reinforced concrete piles

AbstractThe use of reinforced concrete (RC) piles in integral abutment bridges (IABs) has not been widespread due to concerns over pile flexibility and the potential for concrete cracking. This is the reason why the use of steel piles is the preferred solution in the United States. However, in various countries where IABs are still seldom used, RC piles are more readily available and economical. Hence, an understanding of the behaviour of IABs with RC piles can lead to a wider implementation of integral solutions. This paper presents the results of a parametric study conducted to evaluate how both the design variables and the accuracy of the modelling approach influence the potential use of integral solutions with RC piles in prestressed concrete bridges up to 200 m long. Finite element modelling was used and four levels of approximation (LoA) were established for the analyses, ranging from simple linear‐elastic to more complex non‐linear models. The results show that existing concerns over concrete cracking control can be overcome if adequate options in design are used together with the adequate LoAs in structural analysis. Integral solutions with RC piles for bridges up to 200 m long can generally be adopted, although in comparisons with non‐integral designs a significant additional amount of prestressing steel is to be expected. The results also include a set of charts with practical estimates to help designers in their first approach to the preliminary design of an IAB.

Experimental investigation on GFRP strengthened RC piles under lateral loads

Piles could be damaged under major lateral loading environment for a long period. The sources of lateral loads are lateral earth pressure, wind loads, seismic loads, impact loads from ships (berthing and mooring) eccentric loads on columns, river current and mud movement loads in alluvial settings (foundations subject to scour), ocean wave forces, slope movements and cable forces on transmission towers. Hence, it is important to improve the lateral load capacity of pile foundation. In recent years, Fibre Reinforced Polymer (FRP) jacketing has become popular to retrofit existing deficient piles. The lightweight, high strength and corrosion resistance of FRPs made them particularly suitable for repair. This paper presents the experimental study on Glass Fibre Reinforced Polymer (GFRP) strengthened Reinforced Concrete (RC) piles subjected to lateral loads. The effects of GFRP strengthening on RC piles were studied.

Seismic Performance of Prestressed Reinforced Concrete Piles Reinforced with Nonprestressed Reinforcements

The main purpose of this paper is to study the seismic performance of prestressed reinforced concrete pile (PRC pile) reinforced with nonprestressed reinforcements. Two prestressed high strength concrete piles (PHC piles) and two PRC piles were tested. The variables studied in this research are the prestressed reinforcements ratio and nonprestressed reinforcements ratio. The piles subjected to low-cycle loading were presented in this paper, including the hysteretic performance, stiffness degradation curves, coefficient of equivalent viscous damping and skeleton-frame curves. It is shown that the failure modes of all specimens are bending damage from the test and PRC piles have good energy-absorbing hysteretic behavior.

Nonlinear behavior of reinforced concrete (RC) and steel fiber added RC (WS-SFRC) model piles in medium dense sand

Behavior of laterally loaded reinforced concrete (RC) model piles in medium dense sand was investigated in this study. Influence of steel fibers on nonlinear RC pile response was especially studied. Five types of model piles were tested under lateral loading and lateral+axial loading. RC-with bending reinforcement pile tests involved testing of model piles with and without shear reinforcement. Tests were performed also on concrete and steel fiber reinforced concrete piles in order to observe the influence of steel fibers by isolating them from bending and shear reinforcement. The steel fiber ratio by volume was decided as 1% based on previous experience. Prior to the model pile tests, bending tests were made on flexural elements to obtain the moment–curvature relationship. The study also enabled observation of loading rate effects and influence of axial load and steel fiber on reinforced pile response. Test results show that the RC-with steel fiber pile behavior is superior to the conventional RC pile under axial loading and different rate of loadings. It is concluded that steel fibers can be utilized to replace shear reinforcement to produce concrete piles with only bending reinforcement.

The Application for Reinforced Concrete Piles of Marine Sedimentary Soft Soil Foundation Treatment

Marine sedimentary soft soil is larger water content, higher compressibility, and lower strength and buried deep. The sluice project in the marine soft soil foundation construction is beneficial to the people's livelihood needs to conduct foundation treatment. Through the scheme comparison, the sluice wing wall is located in the Yellow River estuary uses reinforced concrete pile to treat foundation. The pile diameter is 0.5m, the pile length is 19m, and the pile end is located in the sand to meet the requirements of various conditions.

Analyses of Influencing Factors and Numerical Model of the Reinforced Concrete Piles

Analyses of Influencing Factors and Numerical Model of the Reinforced Concrete Piles

Experimental Analyses of Dynamic Damage of the Reinforced Concrete Pile

The earthquake often leads to the damage of stabilizing concrete pile. In order to analyze the damage mechanism of the reinforced concrete stabilizing pile, this article uses the developed concrete model piles, studies the seismic deformation of a slope reinforced with stabilizing piles and the dynamic broken damage phenomenon of pile by using the dynamic centrifuge model test without groundwater. The results show that the earthquake action leads to the obvious increase of dynamic excess bending moments, eventually results in the pile’s breaking damage.

Static and dynamic response analysis of reinforced concrete piles

In order to clarify restoring force and deformation characteristics of reinforced concrete (RC) pile – soil system, static and dynamic loading tests were conducted for RC piles in dry sandy soil. It was clarified that, within the range of the tests, the restoring force at pile head can be determined from the maximum damaged depth of the pile which depends on the relative stiffness between the pile and its surrounding soil. Additionally, it was observed in the dynamic loading tests that the loading velocity has a small effect on the restoring force of the pile. The derived results from these tests can be used to establish an accurate evaluation method for seismic performance of RC structures. Key words: Dynamic and static analysis, reinforced concrete piles, dry sand, restoring force.

Shear behaviour of reinforced concrete pile caps under full-width loading

There has been discrepancy in the design procedures for reinforced concrete (RC) pile caps in the UK design codes BS 8110 and BS 5400 that arose from the independent development of semi-empirical bending theory-based shear design formulae based on limited experimental data. Stimulated by the advent of the Eurocodes, a series of reduced-scale RC pile caps were tested under full-width wall loading to investigate their real shear capacity. The British Standards have been confirmed to be conservative, with the degree of conservatism found to be a function of shear enhancement factor and the width of cap over which shear enhancement is applied. The strut-and-tie model from BS 8110 gave better agreement with the experimental results, although the limit on the width of the tension tie of three pile diameters meant it became conservative at wide transverse pile spacings. A revision to the strut-and-tie model is proposed, in which longitudinal reinforcement across 90% of the cap width is considered to participate in the yielding tie.

Evaluation of Protective Jackets Used on Reinforced Concrete Piles: Case Study of Hampton Roads Bridge and Tunnel

Corrosion of reinforced concrete piles located in a marine environment is of great concern, as it can reduce the load capacity of the piles and shorten their effective life. The Hampton Roads bridge and tunnel, located where the James River discharges into the Chesapeake Bay, was constructed with precast prestressed concrete piles, which have been exposed to a marine environment for 53 years. In the early 1980s, the Virginia Department of Transportation installed protective jackets on the piles to address the effects of chloride contamination and corrosion damage of the piles. The jackets were constructed by placing reinforcing mesh and a fiberglass stay-in-place form around an existing pile, and grouting the annular space with a mortar fill. The objective of these jackets was to prevent or mitigate corrosion activity by blocking water, oxygen, and chlorides from reaching the pile reinforcement. A study was undertaken to evaluate the effectiveness of the protective jackets through the use of visual evalua...

The Application for Reinforced Concrete Piles of Chamber on Soft Foundation Treatment

The Application for Reinforced Concrete Piles of Chamber on Soft Foundation Treatment