Axial testing and numerical modeling of square shaft helical piles under compressive and tensile loading

2008 ◽  
Vol 45 (8) ◽  
pp. 1142-1155 ◽  
Author(s):  
Ben Livneh ◽  
M. Hesham El Naggar
Keyword(s):  
Numerical Modeling ◽  
Shear Failure ◽  
Load Transfer ◽  
Failure Surface ◽  
Correlation Factor ◽  
Axial Loads ◽  
Element Analysis ◽  
Pile Capacity ◽  
Helical Piles ◽  
Load Tests

Helical piles are increasingly used to support and rehabilitate structures subjected to both tensile and compressive axial loads. This paper presents a detailed investigation into the axial performance of helical piles. The study encompasses 19 full-scale load tests in different soils and numerical modeling using finite element analysis. The ultimate load criteria and load transfer mechanisms for helical piles were examined. In addition, the relationship between the installation effort (torque) and pile capacity was explored to determine its suitability for predicting pile capacity. The piles tested were made of three circular pitched bearing plates welded at a spacing of three helical diameters to a solid-square, slender steel shaft. It is proposed to determine the ultimate pile capacity as the load corresponding to pile head movement equal to 8% of the largest helix diameter plus the pile elastic deflection. A torque correlation factor, KT = 33 m–1 for compression and KT = 24 m–1 for uplift, was established to relate the ultimate pile capacity to the installation torque. It was found that load transfer to the soil is predominantly through a cylindrical shear failure surface that follows the tapered profile of the interhelices soils and the bearing capacity of the lead helix in the direction of loading.

Helical Pile Capacity-to-Torque Correlation: A More Reliable Capacity-to-Torque Factor Based on Full Scale Load Tests

2020 ◽  
Vol 14 (2) ◽  
Author(s):  
Moncef Souissi
Keyword(s):  
Axial Load ◽  
Static Load ◽  
Full Scale ◽  
Load Direction ◽  
Pile Capacity ◽  
Helical Piles ◽  
Load Tests ◽  
High Torque ◽  
Low Torque ◽  
The One

The capacity-to-torque ratio, Kt, has been used in the design of helical piles and anchors for over half a century. Numerous research efforts have been conducted to accurately predict this capaci-ty-to-torque ratio. However, almost of all these Kt factors are based on shaft geometry alone. The ca-pacity-to-torque ratio described herein was found to depend on the shaft diameter, shaft geometry, helix configuration, axial load direction, and installation torque. In this study, 799 full scale static load tests in compression and tension were conducted on helical piles of varying shaft diameters, shaft geometry, and helix configurations in different soil types (sand, clay, and weathered bedrock). The collected data were used to study the effect of these variables on the capacity-to-torque ratio and resulted in developing a more reliable capacity-to-torque ratio, Km, that considers the effect of the variables mentioned above. The study shows that the published Kt values in AC358 (ICC-ES Acceptance Criteria for Helical Piles Systems and Devices) underestimate the pile capacity at low torque and overestimate it at high torque. In addition, and based on probability analysis, the predicted capacity using the modified Km results in a higher degree of accuracy than the one based on the published Kt values in AC358.

scholarly journals Large-diameter helical pile capacity – torque correlations

2017 ◽  
Vol 54 (7) ◽  
pp. 968-986 ◽  
Author(s):  
Jared Harnish ◽  
M. Hesham El Naggar
Keyword(s):  
Large Diameter ◽  
Failure Criteria ◽  
Load Test ◽  
Ultimate Capacity ◽  
Pile Capacity ◽  
Shearing Resistance ◽  
Helical Piles ◽  
Torque Capacity ◽  
Load Tests ◽  
Pile Load Tests

Large-diameter helical piles are utilized increasingly to support heavy structures. Both the magnitude of the required installation torque and the pile capacity can be directly attributed to the soil shearing resistance developed over the embedded area of the pile including the shaft and helical plates. Hence, the pile capacity can be correlated to installation torque. Such correlations are widely used in the helical pile industry as a means for quality control and quality assurance. In the current study, a total of 10 test piles were installed while monitoring the installation torque continuously with depth. The recorded installation torque profiles were demonstrated to be accurate and repeatable. Field pile load tests were conducted and their results were analyzed to determine the interpreted ultimate capacity of the test piles. The results demonstrate that the ultimate capacity of large-diameter helical piles can be interpreted from pile load test data employing the failure criteria proposed by Elkasabgy and El Naggar in 2015 and Fuller and Hoy in 1970. The measured installation torque and corresponding ultimate capacity values were employed to define torque–capacity correlation (Kt) based on embedded pile area. It was demonstrated that the proposed Kt is suitable for large-diameter helical piles.

scholarly journals Numerical Analysis of Triplet Shear Test on Brickwork Masonry

2013 ◽  
Vol 831 ◽  
pp. 437-441 ◽  
Author(s):  
Jun Zhe Wang ◽  
Andrew Heath ◽  
Pete Walker
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
Shear Failure ◽  
Complex Loading ◽  
Failure Surface ◽  
Element Model ◽  
Element Analysis ◽  
Shear Strength Test ◽  
Linear Elastic ◽  
Compressive Stresses

Shear failure is often found for masonry structure when subjected to complex loading. This paper presents the numerical analysis of shear strength test on triplet masonry specimens under different normal compressive stresses. Two different models were produced using a commercially available finite element analysis package ANSYS. The first model is a continuum model with the brick unit modeled as linear elastic material, while the mortar joints are modeled using a Drucker-Prager (DP) material or a concrete material. In the second model, the mortar joints as well as the brick/mortar interfaces were represented by a series of contact elements, and the Mohr-Coulomb failure surface was employed by these contact elements. Comparisons with the experimental results show that both models give satisfactory predictions for the maximum failure load, while the finite element model with interfaces has a better performance in terms of the load displacement response.

The design and performance of heavily loaded piles in a high-risk earthquake zone

1983 ◽  
Vol 20 (2) ◽  
pp. 262-275
Author(s):  
George H. Watson ◽  
Richard S. Williams ◽  
Chun Chiu Yam
Keyword(s):  
Industrial Development ◽  
Load Transfer ◽  
Active Regions ◽  
Load Test ◽  
Lateral Loads ◽  
Axial Loads ◽  
Load Tests ◽  
The Government ◽  
And Performance ◽  
Earthquake Zone

Amoco International Oil Company and the government of Trinidad and Tobago have formed a consortium (FERTRIN) to construct and operate two ammonia plants. The site is located on the west coast of Trinidad some 32 km south of Port of Spain and is part of a major industrial development being planned by the government.Trinidad is located in one of the most seismically active regions of the Caribbean. Local building codes are still in the process of development, but local practice requires design specifications similar to the highest risk earthquake zones in California. As a result, piling under critical and heavy structures is often governed by the lateral rather than the vertical load requirements.This paper describes the choice, design, and performance of the piles tested for the FERTRIN ammonia plants. The design methods are evaluated and predictions of both lateral and vertical pile performance are compared with the load test results. Keywords: piles, lateral loads, axial loads, load tests, foundations, load transfer.

Effect of loading history on the compression and uplift capacity of driven model piles in sand

1992 ◽  
Vol 29 (2) ◽  
pp. 334-341 ◽  
Author(s):  
R. C. Joshi ◽  
Gopal Achari ◽  
Shenbaga R. Kaniraj
Keyword(s):  
Key Words ◽  
Load Transfer ◽  
Uplift Capacity ◽  
Loading History ◽  
Pile Capacity ◽  
Rate Of Penetration ◽  
Constant Rate ◽  
Tip Resistance ◽  
Tension And Compression ◽  
Load Tests

Model piles were tested in dry uniform sand to study the effect of loading history on the behaviour of piles in compression and tension. A sand bed was prepared by the raining technique, and a smooth cylindrical instrumented pile was driven into the sand. Load tests on piles were conducted at a constant rate of penetration of 0.5 mm/min. The effects of length to diameter (L/D) ratio and sand density were also investigated. The load transfer along the pile surface was studied for an L/D ratio of 33. The pile tip resistance was measured for model piles with L/D ratios of 20–33 and was generally found to be constant. A significant decrease in the pile capacity both in tension and compression was noted for piles having a loading history. When a pile was loaded in compression after being loaded in tension, the tip load could be mobilized only after a certain movement of the pile. The mobilization of the shaft load, however, started immediately. Key words : load tests, model piles, dry sand, loading history, tip capacity, shaft capacity, compression, tension, load transfer.

Thermo-structural analysis of cryogenic tanks with common bulkhead configuration

2021 ◽  
pp. 095441002110247
Author(s):  
S Sumith ◽  
R Ramesh Kumar
Keyword(s):  
Structural Analysis ◽  
Temperature Gradient ◽  
Thermal Gradient ◽  
Load Transfer ◽  
Thermal Analyses ◽  
Positive Margin ◽  
Heat Transfer Analysis ◽  
Liquid Oxygen ◽  
Launch Vehicles ◽  
Element Analysis

In launch vehicles, cryogenic propulsion stages store liquid oxygen (LOX) at 76 K and liquid hydrogen (LH2) at 20 K, generally in two separate insulated tanks connected through tubular truss components. Consequently, load transfer from the LH2 tank to the LOX tank is very much localized, resulting in a nonoptimal design. This article presents an alternative single tankage design using a common bulkhead (CBH) to enhance the payload capability, which enables maintaining LH2 temperature within a specified temperature when exposed to a temperature gradient. A sandwich insulator using aramid honeycomb embedded with polyimide foam keeps the LH2 temperature within 20 ± 1 K is proposed, based on transient heat transfer analysis for 1000 s. The foam-filled honeycomb core is treated as equivalent foam in the analysis as the thermal conductivity of the core and the foam is quite close. The efficacy of the insulator is established by an experiment to measure the back wall temperature when liquid nitrogen is loaded on the top skin of the panel, and the insulator maintains a temperature gradient of 123 K for 1000 s. A good agreement is obtained between the transient finite element analysis results with experimental data. An externally insulated LOX tank configuration with an optimum length of the skirt–cylinder where the temperature reaches 80 K is arrived at based on slosh, buckling, and thermal analyses. No thermal gradient is found across the thickness of the skirt, while the thermal gradient is observed along the length of the skirt as anticipated. An integrated thermo-structural analysis of the cryo-system is carried out considering temperature-dependent material properties. A positive margin for the skirt is obtained. A payload gain of 366 kg is estimated based on the present study for the new design option with a CBH and skirt as compared to the traditional tubular truss arrangements.

scholarly journals Strength and Failure Mechanism of Composite-Steel Adhesive Bond Single Lap Joints

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Kai Wei ◽  
Yiwei Chen ◽  
Maojun Li ◽  
Xujing Yang
Keyword(s):  
Failure Mechanism ◽  
Shear Failure ◽  
Failure Load ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Adhesive Failure ◽  
Interface Failure ◽  
Element Analysis ◽  
Single Lap Joints ◽  
Structural Adhesive

Carbon fiber-reinforced plastics- (CFRP-) steel single lap joints with regard to tensile loading with two levels of adhesives and four levels of overlap lengths were experimentally analyzed and numerically simulated. Both joint strength and failure mechanism were found to be highly dependent on adhesive type and overlap length. Joints with 7779 structural adhesive were more ductile and produced about 2-3 kN higher failure load than MA830 structural adhesive. Failure load with the two adhesives increased about 147 N and 176 N, respectively, with increasing 1 mm of the overlap length. Cohesion failure was observed in both types of adhesive joints. As the overlap length increased, interface failure appeared solely on the edge of the overlap in 7779 adhesive joints. Finite element analysis (FEA) results revealed that peel and shear stress distributions were nonuniform, which were less severe as overlap length increased. Severe stress concentration was observed on the overlap edge, and shear failure of the adhesive was the main reason for the adhesive failure.

scholarly journals Full Contoured Tooth-Implant Supported 3-Pointic All-Ceramic Denture During Occlusal Load Transfer in Lateral Region

2016 ◽  
Vol 61 (2) ◽  
pp. 843-846 ◽  
Author(s):  
J. Żmudzki ◽  
P. Malara ◽  
G. Chladek
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Bone Tissue ◽  
Load Transfer ◽  
Element Analysis ◽  
Lateral Region ◽  
The Finite Element Analysis ◽  
All Ceramic ◽  
Dental Professional ◽  
Wide Zone

Abstract Implant and a tooth supported dentures are avoided by dentists because of uneven distribution of occlusal loads between a stiffer implant and a more pliable tooth. The hypothesis was that a 3-point all-ceramic bridge supported on a natural second premolar tooth and a two-pieces typical implant bears safely mastication loads. The finite element analysis showed that the implant splinted by all-ceramic zirconium bridge with the second premolar was safe under lateral mastication load, but there was found an overload at wide zone of bone tissue around the implant under the load of 800 N. The patients can safely masticate, but comminution of hard food should be avoided and they should be instructed that after such an indiscretion they need to contact a dental professional, because, in spite of integrity of the prosthesis, the bone tissue around the implant may fail and there is a hazard of intrusion of the tooth.

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