Prestressed High-strength Concrete Research Articles

A study of the possibility of using TFT-LCD waste glass as an admixture for steam-cured PHC piles

In the high-tech industry in Korea, the use of thin-film transistor liquid-crystal display (TFT-LCD) glass products has increased significantly in recent years and large amounts of TFT-LCD waste glass are produced during the manufacturing process. This research studied the effect of TFT-LCD waste glass proportions on binder in mortar when added with an appropriate amount of activator. Experiments were conducted to determine the optimal replacement content to ensure that the quality of prestressed high-strength concrete (PHC) products is maintained. The results indicate that the use of TFT-LCD waste glass powder as an admixture for PHC piles was efficient in reducing alkali–silica reaction expansion and increasing workability. The compressive strength of mortars with TFT-LCD waste glass was also improved compared with that of normal mortar, due to the increased amount of calcium silicate hydrates created by pozzolanic reaction between the waste glass and activator. In field tests, the compressive strength of a PHC pile with TFT-LCD waste glass powder was about 3 MPa higher than that of a normal PHC pile. Guidelines are suggested for the recycling of TFT-LCD waste glass in steam-cured concrete products such as PHC piles.

A Case Study of Retaining Wall Using Pre-Stressed High-Strength Concrete (PHC) Pile for Deep Excavation Work

With increasing land prices and a lack of space in urban areas in the Republic of Korea, urban construction sites require deeper and larger excavations. For this reason, the selection of an adequate retaining wall system is becoming more important than any other aspect of excavation work. Cast-in Place pile (CIP) method, one of construction methods for retaining walls, is generally selected in excavation work for urban projects. CIP has some disadvantages such as additional waterproof work and environmental. The Pre-stressed High-strength Concrete (PHC) pile method is a solution that attempts to resolve these disadvantages of the CIP method. This study aims to compare the CIP and the PHC method in terms of cost and time. It was found that applying the PHC pile method could reduce cost and time compared to CIP by case study.

Thermal performance analysis of a ground-coupled heat pump integrated with building foundation in summer

Geothermal energy has been provided to improve the energy performance of buildings with great support from the government in Korea. However, despite the many advantages of using a ground-coupled heat pump (GCHP) with geothermal energy, the high construction cost of the ground-coupled heat exchanger (GCHE) is the primary obstacle to prevent the supply and spread of GCHPs.In this study, in order to overcome the problems of the conventional GCHP, a GCHP integrated with a PHC (prestressed high-strength concrete) pile, which is used in the foundation of buildings, was introduced and its thermal performance was analyzed through experiments conducted in summer. To increase the thermal performance, a coil-type pipe was used. The PHC-pile-integrated GCHP was installed at a depth of 15m. However, because it was installed in the beneath of the building, it was not largely affected by the outdoor temperature. The measured effective thermal conductivity was 3.69W/m°C, which is similar to that of a conventional vertical GCHP. Also, the COP was determined to be 3.9–4.3, which is slightly lower than the conventional vertical GCHP. However, considering the fact that the expensive drilling cost could be mitigated by 83.7%, the thermal performances were satisfactory.

Experimental Research on the Influence of the Pile Type and Stirrup on the Seismic Performance of PHC Piles

The influence of the pile type and the stirrup on the seismic performance was evaluated based on the results of reversed cyclic loading tests on the four prestressed high strength concrete (PHC) piles. It is indicated that the AB-type pile has the better seismic performance than the A-type pile from the results. The bearing capacity does not increase obviously with decreasing of the stirrup spacing and increasing of the stirrup diameter. The degradation of stiffness does not decrease significantly with decreasing of the stirrup spacing and increasing of the stirrup diameter. The energy dissipation capacity is improved with increasing of the stirrup diameter and decreasing of the stirrup spacing.

Effect of driving long pre-stressed high-strength concrete pipe piles in alluvium and its mechanical behavior

To investigate the driving effect of long pre-stressed high-strength concrete (PHC) pipe piles on surrounding cohesive soil layers and mixed soil layers, standard penetration tests and static cone penetration tests were performed. Pore water pressure, lateral displacement in the surrounding soils and shaft forces along the piles were also measured. The process of driving piles was recorded and the mechanical behavior of the piles was researched using fibre optic sensors as well. The results indicated that significant excess pore pressure and lateral deformation were developed as the result of the pile driving and their magnitudes decreased with distance from the pile. Pile driving improved the mechanical properties of the surrounding soils and enhanced the liquefaction resistance of both the silt and silty sand layers. The ratio of soil plug length to pile length ranged from 22 to 43 % and the PHC pile with a thinner wall resulted in a greater plug. The distribution of the shaft force was nonlinear along the pile length and became more obvious with the increase of the applied load. Shaft resistance varied with the magnitude of applied load and the soil properties.

Discussion of “Distribution of residual load and true shaft resistance for a driven instrumented test pile”1Appears in the Canadian Geotechnical Journal,48(4): 583–598 [doi: 10.1139/t10-084

The authors have presented a well-documented case study of the load test interpretation of prestressed high-strength concrete (PHC) piles, which are very popular in the Far East and are often favoured over steel piles on the basis of cost. Despite their popularity, well-analyzed load test case histories are rare and hence the authors’ paper is a valuable contribution to the technical knowledge base. Although the authors’ have considered the geotechnical aspects in detail, the discussers believe that this case study also would benefit from a fuller analysis of the structural conditions of the piles. This is because the authors have identified that the key design aspects for this site are actually the maximum load in the pile and the pile structural strength, but not the pile capacity. Based on the load test results, the authors concluded that the long-term maximum load in the pile will approach the pile structural strength and hence grouting the central void should be considered. The discussers have carried out an assessment of the pile strength using a different approach and compared the results with the current design guidelines. It was found that even with the central void grouted, the PHC piles are still not sufficiently robust and a different pile size or type may need to be considered. The discussers’ assessment and, where appropriate, comparisons with the authors’ results are described as follows.

Electrochemical corrosion behavior of arc sprayed Zn and Zn15Al coatings in simulated salina soil and neutral meadow soil solutions

Arc sprayed Zn and Zn15Al coatings were chosen to protect the metal ends of prestressed high-strength concrete (PHC) pipe piles against corrosion of salina soil in northern china and neutral meadow soil in northeast China. The corrosion behavior of the coated Q235 steel samples in two simulated soil solutions were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The experimental results show that the corrosion of the matrix Q235 steel in both simulated solutions is remarkably inhibited by Zn and Zn15Al coatings. The corrosion products on Zn and Zn15Al are thick, compact, firm and protective. The corrosion current density icorr of both Zn and Zn15Al-coated samples is decreased evidently with corrosion time, and the charge transfer resistance Rct is increased greatly. The corrosion resistance indexes of Zn and Zn15Al in simulated neutral meadow soil solution are more outstanding than those in salina soil. The corrosion resistance of Zn15Al in salina soil is slightly superior to that of Zn. When the sprayed coatings are sealed with epoxy resin, the corrosion resistance of the coatings is further enhanced markedly.

Vibration Effects Attributable to Driving of PHC Pipe Piles

AbstractTo ensure the safety of adjacent 16.7-m-high concrete frame structures (cooling towers) and buried pipelines in service during installation of 83 prestressed high-strength concrete (PHC) pipe piles, the behavior of the ground, the buried pipelines, and cooling towers was monitored by a comprehensive instrumentation program. The field measurements included the following: (1) time histories of the particle velocities and corresponding Fourier spectra in three mutually perpendicular directions at various pile penetration depths and (2) vertical and horizontal movements of the buried pipelines caused by pile installation. Based on the analysis of the field data, the following major findings were obtained: (1) unlike the driving of prestressed concrete piles or cast in situ piles, the vibration velocity in the vertical direction was not greater than that in the plane during PHC pipe pile driving; (2) the amplitudes of the peak particle velocities were relatively independent of the pile penetration dept...

Uplift behavior and load transfer mechanism of prestressed high-strength concrete piles

Prestressed high-strength-concrete (PHC) tube-shaped pile is one of the recently used foundations for soft soil. The research on uplift resistance of PHC pile is helpful to the design of pile foundations. A field-scale test program was conducted to study the uplift behavior and load transfer mechanism of PHC piles in soft soil. The pullout load tests were divided into two groups with different diameters, and there were three piles in each group. A detailed discussion of the axial load transfer and pile skin resistance distribution was also included. It is found from the tests that the uplift capacity increases with increasing the diameter of pile. When the diameter of piles increases from 500 to 600 mm, the uplift load is increased by 51.2%. According to the load-displacement (Q-S) curves, all the piles do not reach the ultimate state at the maximum load. The experimental results show that the piles still have uplift bearing capacity.

Corrosion behaviors of arc spraying single and double layer coatings in simulated Dagang soil solution

Three kinds of single layer coatings of Zn, Zn15Al, 316L stainless steel and two kinds of double layer coatings with inner layer of Zn or Zn15Al and outer layer of 316L stainless steel by arc spraying were developed to protect the metal ends of prestressed high-strength concrete (PHC) pipe piles against soil corrosion. The corrosion behaviors of the coated Q235 steel samples in the simulated Dagang soil solution were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and natural immersion tests. The results show that the corrosion of the matrix Q235 steel is effectively inhibited by Zn, Zn15Al, Zn+316L and Zn15Al+316L coatings. The corrosion rate value of Zn15Al coated samples is negative. The corrosion products on Zn and Zn15Al coated samples are compact and firm. The corrosion resistance indexes of both Zn and Zn15Al coated samples are improved significantly with corrosion time, and the latter are more outstanding than the former. But the corrosion resistance of 316L coated samples is decreased quickly with the increase in immersion time. When the coatings are sealed with epoxy resin, the corrosion resistance of the coatings will be enhanced significantly.

高強度PC杭とパイルキャップとの接合部の強度と変形性状 : 高強度PC杭の耐力および変形性能向上に関する研究(4)

高強度PC杭とパイルキャップとの接合部の強度と変形性状 : 高強度PC杭の耐力および変形性能向上に関する研究(4)

高強度PC杭とパイルキャップとの接合に関する研究 : 高強度PC杭の耐力及び変形性能向上に関する研究(3)

高強度PC杭とパイルキャップとの接合に関する研究 : 高強度PC杭の耐力及び変形性能向上に関する研究(3)

高強度PC杭の中空部にコンクリートを中詰めした効果に関する研究 : 高強度PC杭の耐力および変形性能向上に関する研究(2)

高強度PC杭の中空部にコンクリートを中詰めした効果に関する研究 : 高強度PC杭の耐力および変形性能向上に関する研究(2)

Japan's foundation design guide

Although described as a Guide, the 1984 design manual for foundation design forms part of the enforcement system of the Earthquake Resistance code in Japan. The Guide applies knowledge gained from recent unexpected experiences, notably the damage to prestressed high‐strength concrete (PHC) piles in the Off‐Miyagi earthquake without any effects from change in ground conditions, such as liquefaction. This review is by the Head of the Geotechnical Engineering Division of the Japanese Building Research Institute, who chaired the Working Party on the Guide.