Evaluation of Several Design Methods for Calculating Axial Compression Capacity of Large Diameter Open-Ended Piles

The axial compressive behaviour of an innovative type of square concrete filled steel tube (CFST) column to reinforced concrete (RC) beam joint was experimentally investigated in this paper. The innovative joint was designed such that (i) the steel tubes of the CFST columns were completely interrupted in the joint region, (ii) the longitudinal reinforcements from the RC beams could easily pass through the joint area and (iii) a reinforcement cage, including a series of reinforcement meshes and radial stirrups, was arranged in the joint area to strengthen the mechanical performance of the joint. A two-stage experimental study was conducted to investigate the behaviour of the innovative joint under axial compression loads, where the first stage of the tests included three full-scale innovative joint specimens subjected to axial compression to assess the feasibility of the joint detailing and propose measures to further improve its axial compressive behaviour, and the second stage of the tests involved 14 innovative joint specimens with the improved detailing to study the effect of the geometric size of the joint, concrete strength and volume ratio of the steel meshes on the bearing strengths of the joints. It was generally found from the experiments that (i) the innovative joint is capable of achieving the design criterion of the ‘strong joint-weak member’ with appropriate designs, and (ii) by decreasing the height factor and increasing the volume ratio of the steel meshes, the axial compressive strengths of the joints significantly increased, while the increase of the length factor is advantageous but limited to the resistances of the joint specimens. Because of the lack of existing design methods for the innovative joints, new design expressions were proposed to calculate the axial compression resistances of the innovative joints subjected to bearing loads, with the local compression effect, the confinement effect provided by the multi-layers of steel meshes and the height effect of concrete considered. It was found that the proposed design methods were capable of providing accurate and safe resistance predictions for the innovative joints.

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Hydrodynamic Forces on Subsea Pipelines due to Orbital Wave Effects

Volume 4A: Pipeline and Riser Technology ◽

10.1115/omae2013-10647 ◽

2013 ◽

Author(s):

Annelise Karreman ◽

Jeremy Leggoe ◽

Terry Griffiths ◽

Lisa King ◽

Nino Fogliani

Keyword(s):

Vertical Velocity ◽

Large Diameter ◽

Significant Proportion ◽

Economic Benefits ◽

Hydrodynamic Forces ◽

Design Methods ◽

Fundamental Aspect ◽

Experimental Investigations ◽

Rectilinear Motion ◽

Particle Paths

Ensuring pipeline stability is a fundamental aspect of subsea pipeline design and can contribute a significant proportion of project costs in regions with large diameter trunklines, shallow water and severe geotechnical and metocean conditions [1]. Reducing the conservatism and simplifications of existing pipeline stabilisation design methods therefore offers economic benefits to hydrocarbon producers necessary to ensure the ongoing viability of projects in these regions. To realise this potential and reduce the conservatism of the existing design methods, a more accurate understanding of the hydrodynamic loads exerted by waves and currents is required. This paper investigates one of the inherent assumptions incorporated into the existing design methods through the arrangement of previous experimental investigations to determine whether rectilinear motion provides a reasonable approximation to simulate the near seabed orbital particle paths in wind-generated waves. This assumption is based on the flattening of particle paths to ellipsoids with depth and ignores the small vertical velocity components near the seabed. Based on the hydrodynamic forces calculated numerically using a validated Computational Fluid Dynamics (CFD) model for rectilinear and orbital wave modelling it is concluded that pipeline stabilisation requirements calculated in accordance with the DNV-RP-F109 absolute lateral static stability design method and rectilinear wave motion assumption are conservative. It is also concluded that the hydrodynamic force asymmetry in favour of the reverse half wave cycle caused by the vertical velocity components in orbital wave conditions requires further consideration to determine the implication for dynamic lateral stability design methods.

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Bearing Capacity of Concrete-Filled Steel Tube Column Sections under Long-Term Loading

International Journal of Innovative Technology and Exploring Engineering - Special Issue ◽

10.35940/ijitee.j9750.0881019 ◽

2019 ◽

Vol 8 (10) ◽

pp. 3530-3536

Keyword(s):

Bearing Capacity ◽

Axial Compression ◽

Steel Tube ◽

Design Methods ◽

Contribution Ratio ◽

Concrete Filled Steel Tube ◽

Numerical Example ◽

European Code

This article presents the design methods for concrete filled circular columns subjected to long-term axial compression and bending. . There are two approaches: stress-based and strain-based for formulations. Both approaches are specified in Russian Code, SP 266.1325800.2016, and in European Code, EN 1994-1-1:2004. A numerical example shows the procedures to calculate the strength of a given column according to two different Codes, the influence of parameters such as steel contribution ratio, relative slenderness to the results in two methods are consider.

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