Prestressed High-strength Concrete Piles Research Articles

Enhancing Quality Management of PHC Piles through Improved Driving Formulas: A Comprehensive Review and Analysis

In construction projects, conducting dynamic load tests on all piles proves impractical. Selective testing estimates bearing capacity, while the remaining piles rely on penetration depth for management. This approach, however, faces reliability issues due to varying conditions among piles. Technological advancements, such as non-contact hammers and sensors, have enhanced the accuracy of penetration depth measurements during final driving. Nonetheless, relying solely on penetration depth for construction and quality management remains problematic. This study, therefore, focuses on enhancing the use of driving formulas to improve pile quality management, particularly for the widely used pre-stressed high-strength concrete (PHC) piles. To improve pile quality management, existing driving formulas underwent review and refinement. Utilizing 258 dynamic load test data from various sites, the Hiley, Gates, and Danish formulas underwent validation through statistical analysis and graphical comparison. Enhancements to the Gates formula, achieved through curve fitting with actual data and the application of segment-based coefficients, demonstrated increased accuracy in bearing capacity estimation. These improvements offer a more reliable approach to pile quality management in construction projects.

Failure analyses of open-ended pre-stressed high-strength concrete pile during driving: insights from distributed fiber optic sensing

Failure analyses of open-ended pre-stressed high-strength concrete pile during driving: insights from distributed fiber optic sensing

Experimental Study on Bonding Performance between Prestressed Concrete Pipe Piles and Core Grout

To make the bearing capacity tests safer and more affordable for prestressed high-strength concrete (PHC) piles, this paper proposes a reaction device for anchor piles filled with core grout based on the geometric and mechanical characteristics of PHC piles. The proposed reaction device has the advantages of convenient construction, strong controllability of the connection quality and low cost. In addition, the pile will not experience prestress unloading or tensile stress under the effect of the upward pulling load. To promote the application of the reaction device developed for PHC pile bearing capacity tests, experimental studies are conducted on the bonding performance between the core grout and the inner wall of the PHC pile. The influence of various factors such as the strength of the core grout, the grouting length, the curing time, and the inner diameter of the PHC pile on the bond strength between the core grout and the inner wall of the PHC pile are investigated. Results show that as the inner diameter of the PHC pile increases, the bond strength between the core grout and the inner wall of the PHC pile decreases with a maximum difference of 5%. The bond strength decreases as the grouting length increases, and gradually stabilizes, with a difference of no more than 10% between the maximum and minimum bond strength values. The higher the strength of the grout is, the greater the bond strength between the core grout and the inner wall of the PHC pile is. The bond strength between the core grout and the inner wall of the PHC pile increases with the increase of the curing time within 28 days of curing, and the bond strength at 3 days meets the requirements of the PHC pile bearing capacity test.

Field testing of seismic performance of prestressed high strength concrete piles reinforced with non-prestressed tendons considering pile–soil interaction

Prestressed high-strength concrete (PHC) piles have been widely applied as foundations. However, the application of PHC piles was challenging under earthquake hazards. With the increasing demand for PHC piles in earthquake-prone areas, PHC piles reinforced with non-prestressed tendons (PRC piles) were proposed to address the problems. A full-scale field test for one PHC pile and four PRC piles with different non-prestressed tendon ratios (NPTRs) was conducted under horizontal cyclic loading, and their seismic performances were evaluated in terms of hysteretic behaviours, horizontal bearing capacity, ductility, pile deformation, and crack patterns. The results indicated that adding non-prestressed tendons led to an improvement in the hysteresis characteristics and deformation capacity but a decrease in the horizontal bearing capacity. The displacement ductility coefficients of all specimens reached or exceeded 2.8, and there was an optimal NPTR of 0.75% that maximized the ductility of PRC piles, which was 62.5% greater than that of the PHC pile. The pile-soil interaction was considered by analyzing the crack development of the surrounding soil and piles.

Laboratory tests on the frictional capacity of core pile–cemented soil interface

Pre-bored grouted planted (PGP) piles are a new type of composite pile in which a core pre-stressed high-strength concrete (PHC) pile is surrounded by a cemented soil (CS) layer. The frictional capacity of the core PHC pile–CS interface has a significant effect on the bearing capacity of a PGP pile. In this work, a series of shear tests was carried out to determine the frictional capacity of pile–CS interfaces for both smooth square piles (SPs) and smooth pipe piles (PPs). The shear test results revealed the following. The peak skin friction (PSF) of the SP–CS and PP–CS interfaces both increased with the CS strength. The PSF of the SP–CS interface was smaller than the PSF of the PP–CS interface of identical pile (equivalent) diameter due to the occurrence of a stress concentration at the corners of the SP. The PSF of the SP–CS and PP–CS interfaces both decreased with the pile (equivalent) diameter. The occurrence of cracks in the CS caused brittle failure of both the SP–CS and PP–CS interfaces.

Research on Dynamic Pile-Driving Formula Parameters and Driving Feasibility of Extra-Long PHC Pipe Piles

Prestressed high-strength concrete (PHC) pipe pile has the advantages of high single pile bearing capacity, a wide range of applications, good driving resistance, fast construction speed, etc. It has been widely used in high-rise buildings, bridges, ports, and other industries. The application of extra-long PHC pipe piles with a length of more than 50 m is increasing. However, there are few studies on the drivability and hammering criteria of extra-long PHC piles. To analyze the drivability of extra-long piles and predict their bearing capacity, in this paper, high-strain dynamic tests were carried out on 14 test sections with the pile foundation of Temburong Bridge in Brunei as the research background. The hammer stop control criteria calculated according to the Hiley formula would lead to excessive hammering. Three types of damage occurred during construction: pile shaft breakage, weld tearing, and pile head breakage. The weight and drop height of the piling hammer selected for this project were appropriate, and the extra-long test piles can be hammered to the design depth. The values of Cp (Compression of the pile) and n (the efficiency of the blow) were fitted based on the dynamic test data, which provided a more accurate reference for the selection of subsequent piling parameters of the project. It provides a more accurate calculation method for predicting the bearing capacity of extra-long PHC piles and provides control criteria for pile stopping and a scientific basis for their design and construction.

Long-Term Settlement Prediction of Ground Reinforcement Foundation Using a Deep Cement Mixing Method in Reclaimed Land

The greenhouse foundation method requires a lower allowable bearing capacity compared to general buildings, but the high-spec and expensive prestressed high-strength concrete (PHC) pile reinforcement method is mainly applied. Therefore, the deep cement mixing (DCM) method, which is one of the ground reinforcement foundations that replaces the PHC piles and secures structural safety suitable for the greenhouse foundation, was considered. To verify the structural safety of the DCM method, a geotechnical survey and soil test were conducted, and a long-term settlement monitoring system was established. The specifications of the DCM foundation were designed to be 0.8 m in diameter, 3 m × 3 m in width and length, and 3 m in depth. Based on the settlement monitoring data, long-term settlement was predicted considering the greenhouse durability of 15 years. For long-term settlement prediction, the Log S–T, hyperbolic, Asaoka method, Schmertmann theory, and the finite element method (FEM) analysis were performed. In the case of the Log S–T, hyperbolic, and Asaoka method based on actual measurement data, the settlement amount was predicted to be 12.18~20.43 mm, and in the case of the Schmertmann empirical formula, it was predicted to be 19.66 m. The FEM analysis result was 8.89 mm. As the most conservative result, the DCM foundation method designed in this paper had an allowable bearing capacity of 310 kN/m2 and a long-term settlement of 20.43 mm. This is the result of satisfying both the allowable bearing capacity of 100 kN/m2 and the allowable settlement range of 25.4 mm as a foundation. Through this study, it was proven that long-term structural safety can be sufficiently secured when the DCM foundation is constructed on a soft ground through a design that considers the required service life and allowable bearing capacity of the structure. In addition, it was confirmed that the Hyperbolic, Asaoka, and FEM analysis method adopted in this paper can be applied to the long-term settlement behavior analysis of the DCM foundation method.

Durable life assessment of centrifugal stratified PHC piles in marine environment

This study proposes an analytical approach to assess the durable life of pre-stressed high-strength concrete (PHC) pipe piles exposed to the marine environment with consideration of centrifugal stratification and different end types. The durable life of the PHC pile is divided into two stages: the initiation stage for chloride penetration and the propagation stage for rust accumulation. To simulate the two stages, a two-layer composite cylinder diffusion model and a thick-walled ring mechanical model are developed based on the governing mechanisms. The proposed diffusion model is verified via comparisons with the numerical models with respect to chloride concentration under different stages. Then, extensive parametric studies based on the proposed method are performed to investigate the effects of end type, cover thickness, and steel bar diameter on the durable life of a PHC pipe pile. The results indicate that both increasing the cover thickness and using the closed-ended pile can significantly extend the durable life of a PHC pipe pile. Furthermore, the open-ended pile with a thinner mortar layer has a longer durable life, while the durable life of a closed-ended pile only slightly increases with a larger thickness of the mortar layer.

Analysis of Influence Factors of Negative Skin Friction on PHC Pile in High-Backfill Sites

It is recognized that NSF on a pile affects the structural and geotechnical design. The formation of NSF on a pre-stressed high-strength concrete (PHC) pile under a control building in a Vietnamese project was investigated using a verified numerical model in FLAC3D. The height of backfills, the consolidation degree of soil, working loads on the PHC pile, and the pile diameter were analyzed in sensitivity analyses to investigate the influence on NSF. It was found that higher backfills and higher consolidation degree were dominant in the formation of NSF, causing an increase of the dragload and an upward movement of the neutral plane. The working load and the pile diameter affected the dragload and the position of the neutral plane less. A limit decrease of the dragload induced by NSF was observed when the working load increased. Accelerating the soil consolidation process would be suggested to avoid great displacement due to NSF.

Application of Fiber Bragg Grating Sensing in Bidirectional Tests of Pile Foundations

Abstract The fiber Bragg grating (FBG) technique has emerged as a new strain monitoring technique in civil engineering applications. In this paper, based on the principle of the FBG technique and the bidirectional test method, FBG sensors and conventional vibrating wire strain gauges (VWSGs) were employed to monitor the strain variation law of a pile under different loads and analyze the relationship between the side resistance and pile-soil relative displacement of soil layers in bidirectional field testing of a large-diameter cast in situ pile. Four field bidirectional test cases of cast in situ piles, prestressed high-strength concrete (PHC) and steel pipe pile, and pile-base post-grouting pile are presented. The applicability and stability of the FBG sensing technique were verified by analyzing the side resistance distribution and bearing capacity. The results showed that FBG sensors can remove the influence because of residual force and the effect of temperature change and concrete expansion photosensitive material provides an improved sensitivity to the external environment compared with a VWSG. The strain and side resistance variation tendency of the cast in situ pile were consistent between the two kinds of sensors. The FBG sensing technique had high test accuracy in the four bidirectional O-cell field test cases of the cast in situ pile, PHC and steel pipe pile, and pile-base post-grouting pile. The pile-base post-grouting technique is an effective procedure that was implemented to increase the ultimate bearing capacity. The research results of this paper reveal a new strain monitoring technique for the bidirectional test method of pile foundations and represent a new test method for measuring the bearing capacity of PHC and steel pipe piles that has a remarkable application value in practical engineering.

Effect of Mineral Admixtures on the Sulfate Resistance of High-Strength Piles Mortar.

Pre-stressed high-strength concrete piles (PHCP) are widely used in the building industry in China. The main aim of our research was to investigate the utilization of quartz powder, fly ash, and blast furnace slag as mineral additives to prepare PHCP mortar. The samples were prepared using steam and autoclaving steaming. The influence of minerals on the sulfate resistance of mortar was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests. The results showed that when compared to single doped quartz powder samples, samples prepared using fly ash or blast furnace slag improved the sulfate resistance of the PHCP mortar. Furthermore, the resistance to sulfate attack of samples with dual doped quartz powder, fly ash, and blast furnace slag also improved. MIP tests showed that mineral additives can change the pore size distribution after autoclave curing. However, the number of aching holes increased after mixing with 20% quartz powder and caused a decrease in the sulfate resistance.

Experimental study on the seismic behavior of new PHC piles

In order to improve the bearing characteristics of prestressed high-strength concrete (PHC) piles, this paper proposes the use of steel strands and steel bars instead of steel reinforcement for PHC piles or PHC piles wrapped in BFRP. Eight PHC piles were tested under low-cycle loading to study their seismic performance. Through the analysis of the test phenomena, hysteresis curve, skeleton curve, strength and stiffness degradation, ductility and energy dissipation, it is found that the bearing capacity of the PHC pile coated with BFRP is much higher than that of the other types of piles. The PHC piles with steel bars and steel strands as the main reinforcement have the best seismic performance. ABAQUS was used to establish nonlinear finite element models. The results show that the experimental results are in good agreement with the finite element results. In addition, it is found that increasing the reinforcement ratio has no effect on improving the bending capacity of the PHC pile, while increasing the reinforcement ratio of the main reinforcement can improve the ultimate bending moment of the PHC pile.

Service life of prestressed high-strength concrete pile in marine environment considering effects of concrete stratification and temperature

Prestressed high-strength concrete (PHC) piles have advantages of light weight and high load carrying capacity, which have been widely applied in coastal and offshore engineering. However, PHC piles serving in the coastal or offshore regions have already undergone severe durability problem. This paper presents a comprehensive method for predicting the service life of PHC piles in the marine environment, which reasonably takes the temperature effects and the concrete stratification caused by centrifugation of PHC piles into account. The pile service life is divided into the diffusion and corrosion periods. The service life of the diffusion period is predicted by solving the diffusion equation formulated for chloride ion diffusion in a two-layer ring medium, the results of which are compared with the data obtained from the elaborate experimental tests to examine the validity. The service life of the corrosion period is determined based on the ultimate corrosion expansion pressure produced by the accumulated corrosion products of steel bar. Various possible key factors, like protective cover thickness, initial chloride ion concentration, mortar layer thickness, etc., are considered to investigate how these parameters critically affect the pile service life. The results suggest that increasing mortar layer thickness can lead to a significant decrease of the service life in both diffusion and corrosion periods; and increasing protective cover thickness and sealing pile end are two effective ways to extend the service life of PHC piles.

Influence of soil reinforcement on the uplift bearing capacity of a pre-stressed high-strength concrete pile embedded in clayey soil

This paper presents a field study on the uplift bearing capacity of a pre-stressed high-strength concrete (PHC) pile embedded in clayey soil, and on the soil around the PHC pile that was treated with cement paste. The PHC pile was inserted into a pile hole filled with cemented soil by its own weight (by gravity), and the soil compaction effect of a conventionally driven pile induced by the installation process was avoided. The test results showed that: the pile head displacement needed to fully mobilize the uplift bearing capacity of the test piles was about 0.1 D (pile diameter); the ultimate skin friction of the PHC pile–cemented soil interface was much larger than that of the cemented soil–soil interface; the PHC pile and the cemented soil around the pile behaved as an integral pile in the load transfer process; and the measured ultimate bearing capacity of the test piles was 0.91–0.94 times the American Petroleum Institute (API)’s proposed values for piles under compression and 0.79–0.80 times the values calculated with the effective stress method for piles under compression.

Flexural Performance Reinforcing Method of Damaged PHC Piles

Cracks may occur in a prestressed high-strength concrete (PHC) pile foundation because of factors, such as the aging of the domestic foundation structure, earthquake occurrence, and foundation ground expansion. The cracking of a pile foundation significantly red uces the bearing capacity of the pile such that its function as a structural foundation is lost. Recently, research on the development of reinforced methods for damaged piles has become essential in securing the stability of pile foundations. In this study, flexural strength tests were conducted on PHC piles with cracks, breakage, and cutting caused by various external forces to examine the reinforcing effects of various reinforcement conditions, such as mortar thickness, epoxy injection, and thickness of reinforcing steel, on the stability of a structure. Based on experimental results, a detailed reinforcing method for crack filling with epoxy, steel reinforcing, and mortar filling is suggested. Keywords: PHC Pile, Damaged Pile, Reinforcing Method, Flexural Strength Test

Flexural performances of prestressed high strength concrete piles reinforced with hybrid GFRP and steel bars

This study developed prestressed high-strength concrete (PHC) piles reinforced with high-strength materials (glass fiber-reinforced polymer (GFRP) bars) for flexural performance enhancement. Flexural strengths and behaviors of PHC piles reinforced with hybrid GFRP and steel bars were experimentally investigated, respectively. Large-scale specimens with total lengths of 12,000 mm and diameters of 600 mm were constructed and tested under bending, accompanied by evaluation of effects of non-prestressed reinforcement type and longitudinal reinforcement ratio. J-factors were calculated to evaluate deformability of all the specimens. PHC piles reinforced with GFRP bars were demonstrated to have much higher flexural capacity than those reinforced with steel bars. Moreover, strains at the midspans of cross sections of all the specimens basically conformed to the assumption of plane section. Failure of PHC piles reinforced with GFRP bars was attributable to gradual concrete crushing, while that of PHC piles reinforced with steel bars resulted from steel yielding. Results of this study were expected to provide theoretical basis for wide engineering applications of PHC piles reinforced with hybrid GFRP bars and steel bars in marine structures.

Analysis of Influence of Sand Parameters on Seismic Performance of PHC Piles

In order to study the effect of sand parameters on the seismic behavior of prestressed high-strength concrete (PHC) pipe piles, using the general finite element software ABAQUS6.12, by applying horizontal reciprocating load on the top of the pile, the influence of sand parameters on the seismic behavior of PHC piles under horizontal load is studied. The results show that increasing the relative density of sand increases the degree of hysteresis of PHC pipe pile hysteresis curve and reduces the cumulative hysteresis energy of PHC pipe piles; Increasing the internal friction angle of the sand increases the hysteresis loop area of the PHC pipe pile, and the cumulative hysteresis energy consumption increases; Increasing the initial modulus of sand soil resistance makes the PHC pipe pile stagnation loop shrinkage, and the cumulative hysteresis energy consumption decreases slightly. Increasing the relative density of sand, internal friction angle and initial modulus of soil resistance can increase the overall stiffness of the pile-soil system, increase the horizontal ultimate bearing capacity of PHC piles and reduce the ultimate displacement of PHC piles.

Effect of Open-Ended PHC Pile Installation during Embankment Widening on the Surrounding Soil

AbstractThis paper investigates the effect of jacking two groups of open-ended prestressed high-strength concrete (PHC) piles on an existing highway embankment based on field measurements of excess...

Quality Control Acceptance Criteria Improvements for Pre-Stressed High Strength Concrete Pile Driving Operations in Japanese Building Construction

The current practice in Japan for most driven pre-stressed high strength concrete (PHC) piling sites utilizes an ″energy formula″ approach involving the ″set-penetration test.″ In its current state, driven PHC piles in the Japanese construction industry are at increased risk of being damaged due to inferior driveability evaluation procedures leading to an increased probability of damaged piles remaining undetected after installation. This study presents two case studies in Okinawa, Japan which utilized dynamic analysis as the primary piling quality acceptance criteria and compares results to the energy formula approach which is more common to Japanese construction sites. Based on the observations of these two case studies, the applicability of dynamic testing, particularly the high-strain dynamic test, the low-strain integrity test, and wave equation analyses is analyzed. In conclusion, a case is presented that Japan′s over reliance on an energy formula approach should be augmented by additional QC procedures. A combination of wave equation analysis, dynamic testing and simple visual inspection of post-driven PHC pile conditions is recommended to better protect the integrity of driven PHC piles throughout Japan.

Experimental Investigation and Nonlinear Finite Element Analysis on Seismic Performance of PHC Piles

Cyclic tests and finite-element method (FEM) analyses were used to study the effects of varying the type of pile, stirrup ratio and reinforcement technique—concrete infilling, steel fibers or deformed steel bars—on the seismic performance of prestressed high-strength concrete (PHC) piles. The failure modes, hysteretic performance, ductility, bearing capacity, stiffness degradation and energy dissipation capacity were observed and analyzed. The results show that the PHC piles were damaged by bending, and that the bearing capacity and ductility of the PHC piles increases with the reinforcement ratio of the prestressed tendons. It was found that adding concrete infilling into the hollow section improves the bearing capacity and hysteretic performance of the PHC piles, whereas the steel fibers have little effect. It was also found that the hysteretic loops of the PHC piles reinforced with deformed steel bars are fuller, and that the energy dissipation is good. An FEM analysis was used to simulate the nonlinear behavior of the PHC piles under cyclic loading, and the predictions agree relatively well with the experimental results.