Load transfer of fibre-reinforced polymer (FRP) composite tapered piles in dense sand

2004 ◽  
Vol 41 (1) ◽  
pp. 70-88 ◽  
Author(s):  
Mohammed Sakr ◽  
M Hesham El Naggar ◽  
Moncef Nehdi
Keyword(s):  
Analytical Solution ◽  
Load Transfer ◽  
Compressive Loading ◽  
Centrifuge Modeling ◽  
Rational Approach ◽  
Dense Sand ◽  
Reinforced Polymer ◽  
Cylindrical Piles ◽  
Confining Pressures ◽  
Fibre Reinforced Polymer

This paper describes an experimental study conducted using a large, laboratory-scale testing facility to test pile segments at different stress levels. The objectives of the study were twofold: to examine the load-transfer mechanism of tapered piles in compression, and to evaluate the effect of pile material on pile performance characteristics. The results of axial compressive loading tests on 26 pile load tests were presented using fibre-reinforced polymer (FRP) concrete composite tapered piles and steel piles. Two installation techniques were used, including conventional head driving and toe driving using a new technique. Piles were tested at different confining pressures to represent a pile segment at depths of 4.0 and 8.0 m. The load distribution along the pile shafts was measured and the results were compared with those from an analytical solution in terms of the taper coefficient Kt. The comparison showed reasonable agreement between Kt values established from the experiments and those obtained from the analytical solution. The measured toe resistance of tapered and cylindrical piles was compared with those from the analytical solution. A simple rational approach was proposed for the design of tapered piles.Key words: tapered piles, FRP, pile capacity, axial performance, centrifuge modeling, shaft resistance, toe resistance.

Evaluation of axial performance of tapered piles from centrifuge tests

2000 ◽  
Vol 37 (6) ◽  
pp. 1295-1308 ◽  
Author(s):  
M Hesham El Naggar ◽  
Mohammed Sakr
Keyword(s):  
Analytical Solution ◽  
Reasonable Agreement ◽  
Compressive Loading ◽  
Axial Loading ◽  
Centrifuge Modeling ◽  
Cohesionless Soil ◽  
Scale Model ◽  
Rational Approach ◽  
Centrifuge Tests ◽  
Cylindrical Piles

The performance of tapered piles under axial compressive loading was investigated using centrifuge model tests. Model tapered and cylindrical piles were installed in cohesionless soil and subjected to axial loading. The objectives of this study were to understand the performance characteristics of tapered piles and develop a rational approach for their design. The results of axial compressive loading tests on 12 one-tenth scale model piles with different taper angles in a centrifuge setup are presented and discussed. Six piles were instrumented and six piles were not. The load distribution along the shaft of instrumented piles was measured and the results were compared with an analytical solution in terms of the taper coefficient Kt. The comparison showed a reasonable agreement between Kt values established from the experiments and those obtained from the analytical solution. A simple rational approach was proposed for the design of tapered piles. The proposed approach was used to calculate the bearing capacity of the tested piles, and reasonable agreement with the measured values was obtained. The results of this study suggest that the pile taper should be limited to the top 20-25 pile diameters of the pile length for optimum efficiency.Key words: tapered piles, pile capacity, axial performance, centrifuge modeling, shaft resistance.

Uplift behaviour of tapered piles established from model tests

2000 ◽  
Vol 37 (1) ◽  
pp. 56-74 ◽  
Author(s):  
M Hesham El Naggar ◽  
Jin Qi Wei
Keyword(s):  
Load Transfer ◽  
Compressive Loading ◽  
Compressive Load ◽  
Tensile Load ◽  
Confining Pressure ◽  
Cohesionless Soil ◽  
Uplift Capacity ◽  
Experimental Modelling ◽  
Confining Pressures ◽  
Load Tests

Tapered piles have a substantial advantage with regard to their load-carrying capacity in the downward frictional mode. The uplift performance of tapered piles, however, has not been fully understood. This paper describes the results of an experimental investigation into the characteristics of the uplift performance of tapered piles. Three instrumented steel piles with different degrees of taper were installed in cohesionless soil and subjected to compressive and tensile load tests. The soil was contained in a steel soil chamber and pressurized using an air bladder to facilitate modelling the confining pressures pertinent to larger embedment depths. The results of this study indicated that the pile axial uplift capacity increased with an increase in the confining pressure for all piles examined in this study. The ratios of uplift to compressive load for tapered piles were less than those for straight piles of the same length and average embedded diameter. The uplift capacity of tapered piles was found to be comparable to that of straight-sided wall piles at higher confining pressure values, suggesting that the performance of actual tapered piles (with greater length) would be comparable to that of straight-sided wall piles. Also, the results indicated that residual stresses developed during the compressive loading phase and their effect were more significant on the initial uplift capacity of piles, and this effect was more pronounced for tapered piles in medium-dense sand.Key words: tapered piles, uplift, axial response, load transfer, experimental modelling.

Analytical Solution for Cohesive Layer Model and Model Verification

2005 ◽  
Vol 13 (8) ◽  
pp. 741-752 ◽  
Author(s):  
Samit Roy ◽  
Yong Wang
Keyword(s):  
Analytical Solution ◽  
Analytical Solutions ◽  
Damage Zone ◽  
Model Verification ◽  
Beam Specimen ◽  
Analytical Prediction ◽  
Zone Length ◽  
Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Cohesive Damage

The objective of this work was to find an analytical solution to the stresses in the cohesive damage zone and the damage zone length at the interface between a fibre reinforced polymer (FRP) plate and concrete substrate. Analytical solutions have been derived to predict the stress in the cohesive layer when considering the deformation in the stiff substrate. A two-dimensional cohesive layer constitutive model with a prescribed traction-separation (stress-strain) law was constructed using a modified Williams' approach, and analytical solutions derived for the elastic zone as well as the damage zone. Detailed benchmark comparisons of analytical results with finite element predictions for a double cantilever beam specimen were performed for model verification, and issues related to cohesive layer thickness were investigated. It was observed that the assumption of a rigid substrate in analytical modelling can lead to inaccurate analytical prediction of the cohesive damage zone length.

Large model test of prestressed carbon fibre reinforced polymer ground anchors

2005 ◽  
Vol 32 (6) ◽  
pp. 1064-1074 ◽  
Author(s):  
Burong Zhang ◽  
Brahim Benmokrane
Keyword(s):  
Rock Mass ◽  
Carbon Fibre ◽  
Model Test ◽  
Load Transfer ◽  
Strain Gauges ◽  
Tensile Behaviour ◽  
Distribution Profile ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

This paper presents a full-scale prestressed ground anchor model test with carbon fibre reinforced polymer (CFRP) 9-bar tendons. The main objectives of this laboratory study were to evaluate the serviceability of the developed bond-type anchorage for post-tensioning applications with CFRP multibar tendons and to study load transfer mechanism of CFRP multibar tendons to surrounding rock mass. A cement-based mortar-filled steel tube was used to simulate a rock mass environment. Extensive instrumentation including resistance strain gauges, fibre optic sensors, embedded strain gauges, and linear variable displacement transducers (LVDTs) were used to monitor the behaviour of the anchor. The test results show that the tested CFRP 9-bar anchor presents an acceptable tensile behaviour under a load of 0.6fpu in accordance with existing codes. The CFRP multibar anchor presents a similar strain distribution profile as that for conventional steel anchors, except giving a shorter load transfer length. It is expected that CFRP 9-bar anchors require a minimum anchor bonded length of 2000 mm with plain cement grouts.Key words: anchor, anchorage, FRP, tendon, slip.

FRP Strengthening of Discontinuous Members

2015 ◽  
Vol 1129 ◽  
pp. 69-76
Author(s):  
Kiang Hwee Tan
Keyword(s):  
Rational Approach ◽  
Test Results ◽  
Structural Members ◽  
Strut And Tie ◽  
Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Large Opening ◽  
Frp Strengthening ◽  
Glass Frp ◽  
Strength And Ductility

Deep beams, corbels, stepped beams, beams with openings and the like are structural members comprising discontinuous regions for which conventional flexural theory does not apply. To strengthen such members using fibre-reinforced polymer (FRP) systems, a rational approach based on strut-and-tie models (STMs) is desirable. This involves the strengthening of struts, ties and nodal zones where required. This study was carried out to illustrate the use of strut-and-tie models in FRP strengthening of reinforced concrete T-beams with a large opening created through the web. Five 3-meter long simply-supported beams were fabricated to simulate existing beams with webs punctured by openings of lengths varying from 180 to 720 mm and located at about 0.5 to 1.5 m from the near support. The depth of the opening was kept constant at 180 mm. Based on strut-and-tie modelling, the beams were strengthened using glass FRP sheets to carry the same ultimate load as a solid beam which had the same dimensions and internal steel reinforcement but without opening, that is, 200 kN. The beams were each subjected to a single load at one-third span from the other support. Test results indicated that all beams with strengthened opening performed as well as the solid beam without opening in terms of cracking and deflection characteristics, in addition to ultimate strength and ductility.

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