The settlement performance of stone column foundations

Vibrated stone columns are frequently used as a method of reinforcing soft ground as they provide increased bearing capacity and reduce foundation settlements. Their performance in relation to bearing capacity is well documented, but there is also a need for enhanced understanding of their settlement characteristics, particularly in relation to small-group configurations. This paper presents results obtained from physical model tests on triaxial specimens 300 mm in diameter and 400 mm high. Parameters investigated include column length to diameter ratio, area replacement ratio and single/group configuration. The findings of the work are as follows. The design is flexible: settlement can equally be controlled using short columns at relatively high area replacement ratios, or longer columns at smaller area replacement ratios. An optimum area replacement ratio of 30-40% exists for the control of settlement. The settlement performance of a small column group is highly influenced by inter-column and footing interaction effects.

The pressure distribution along the stone column in soft clay when subjected to consolidation and foundation loading

The mechanism whereby the foundation loading is transmitted through stone the column (included in soft clay) has received less attention from researchers. This paper reports on some interesting findings obtained from a laboratory-based model study in respect of this issue. The stone column, included in the soft clay bed was subjected to foundation loading under drained conditions. The results show, probably for the first time, how the foundation loadings are transmitted through the column and indeed the existence of “negative skin friction” (a widely accepted phenomena in solid piles) in granular columns in soft clays.

Effect of column base strength on steel portal frames in fire

This paper presents the findings of a project part sponsored by an ICE Research and Development grant on portal frames in fire. The research reported here has also lead to a sucessful research grant from the IStructE. The paper describes a non-linear elasto plastic dynamic finite element model that captures the collapse of a portal frame in fire. It demonstrates that current guidance on the column base stiffness and strength, to prevent collapse, may in some cases be unconservative.

Modelling and fixed bed column adsorption of Cr(VI) onto orthophosphoric acid-activated lignin

The advantage of using an available and abundant residual biomass, such as lignin, as a raw material for activated carbons is that it provides additional economical interest to the technical studies. In the current investigation, a more complete understanding of adsorption of Cr(VI) from aqueous systems onto H PO -acid activated lignin has been achieved via microcolumns, which were operated under various process conditions. The practice of using microcolumn is appropriate for defining the adsorption parameters and for screening a large number of potential adsorbents. The effects of solution pH (2-8), initial metal ion concentration (0.483-1.981 mmol·L ), flow rate (1.0-3.1 cm ·min ), ionic strength (0.01-0.30 mmol·L ) and adsorbent mass (0.11-0.465 g) on Cr(VI) adsorption were studied by assessing the microcolumn breakthrough curve. The microcolumn data were fitted by the Thomas model, the modified Dose model and the BDST model. As expected, the adsorption capacity increased with initial Cr(VI) concentration. High linear flow rates, pH values and ionic strength led to early breakthrough of Cr(VI). The model constants obtained in this study can be used for the design of pilot scale adsorption process. © 2012 Chemical Industry and Engineering Society of China (CIESC) and Chemical Industry Press (CIP).

Flexural behaviour of external R/C steel fibre reinforced beam-column joints

A softened strut-and-tie macro model able to reproduce the flexural behaviour of
external beam-column joint is presented. The model is specific for concrete with hooked steel fibres (FRC) and it is designed to calculate the flexural response, as load-deflection curve, of a beam-column sub-assemblages. The model considers the presence of a constant vertical load acting on the column and of a monotonically increasing lateral force applied at the tip of the beam.

Potential applications of shape memory alloys in seismic retrofitting of exterior RC beam-column joints

Shape memory alloys (SMAs) have the ability to undergo large deformations with minimum residual strain and also the extraordinary ability to undergo reversible hysteretic shape change known as the shape memory effect. The shape memory effect of these alloys can be utilised to develop a convenient way of actively confine concrete sections to improve their shear strength, flexural ductility and ultimate strain. Most of the previous work on active confinement of concrete using SMA has been carried out on circular sections. In this study retrofitting strategies for active confinement of non-circular sections have been proposed. The proposed schemes presented in this paper are conceived with an aim to seismically retrofit beam-column joints in non-seismically designed reinforced concrete buildings. SMAs are complex materials and their material behaviour depends on number of parameters. Depending upon the alloying elements, SMAs exhibit different behaviour in different conditions and are highly sensitive to variation in temperature, phase in which it is used, loading pattern, strain rate and pre-strain conditions. Therefore, a detailed discussion on the behaviour of SMAs under different thermo-mechanical conditions is presented first.

Shape Memory Alloy Features for Seismic Retrofitting of External RC Beam-Column Joint

Shape memory alloys (SMAs) have the ability to undergo large deformations with minimum residual strain and also the extraordinary ability to undergo reversible hysteretic shape change known as the shape memory effect. The shape memory effect of these alloys can be utilised to develop a convenient way of actively confining concrete sections to improve their shear strength, flexural ductility and ultimate strain capacity. Most of the previous work on active confinement of concrete using SMA has been carried out on circular sections. In this study retrofitting strategies for active confinement of non-circular sections have been proposed. The proposed schemes presented in this paper are conceived with an aim to seismically retrofit a beam-column joint in non-seismically designed reinforced concrete buildings.

The complex material behaviour of SMAs depends on number of parameters. Depending upon the alloying elements, SMAs exhibit different behaviour in different conditions and are highly sensitive to variation in temperature, phase in which it is used, loading pattern, strain rate and pre-strain conditions. Therefore, a detailed discussion on the behaviour of SMAs under different thermo-mechanical conditions is presented first in this paper.

The influence of water column variability and seafloor topography on multibeam bathymetric mapping

Senior thesis written for Oceanography 445