Afsluttede PhD Projekter

Influence of Smectite Content on the Deformation Behaviour of Clays

Michael Rosenlund Lodahl

Understanding the high plasticity Palaeogene clay has been a challenge for the geotechnical community in Denmark for decades. The settlement and heave potential of this type of clay exceeds what is commonly expected for Danish clay deposits. Typically, the Palaeogene clays have high strengths but a rather large settlement and heave potential, which means that they do not follow what is normal for most clays where strength and stiffness follow one another. Many relationships exist linking the plasticity index (a state parameter easy to assess) to the engineering properties for clays based on rules of thumb. However, they rarely fit with the behaviour of the Palaeogene clays.

The latest research has indicated that the clay mineral smectite may govern the behaviour of a clay, which means that the settlement and heave potential may be dependent on this content. This project investigates this theory by execution of multiple tests of clays containing smectite.

 

 

ABOUT THE PROJECT


Project title: 
Influence of Smectite Content on the Deformation Behaviour of Clays

PhD student: Michael Rosenlund Lodahl

Contact: mirl@eng.au.dk

Project period: Aug 2014 – July 2017

Main supervisor: Prof. (Docent) Kenny Kataoka Sørensen

Co-supervisors: Helle Trankjær, COWI A/S and Niels Mortensen, nmGeo

Research section: Civil and Architectural Engineering

 

 


Vibration-Based Structural Health Monitoring

Jannick Balleby Hansen

The main focus of this project is on vibration-based damage detection on civil as well as mechanical structures.

This subject can, in a global context, be classified as a “Structural Health Monitoring” (SHM) discipline. The SHM term covers a broad range of different methods and techniques with the coincident goal or purpose of detecting damage, position and magnitude in a structure.

For researchers as well as commercial companies, SHM is an area of great interest due to the fact that SHM has the potential to replace traditional damage detecting techniques which, in most cases, are mere visual inspections supplemented by material samples extracted from the structure. 

It is commonly known that damage, e.g. holes or cracks, in a structure will have an impact on the global dynamic properties, in other words the modal parameters. These parameters can be extracted by means of “Operational Modal Analysis”, sophisticated sensors and data acquisition equipment, even on large civil structures. Hence, damage in a structure can be detected if modal property shifts are observed. The aim of this project is to develop a method which is able to detect and pin-point damage on an arbitrary structure.

ABOUT THE PROJECT


Project title:
Vibration-Based Structural Health Monitoring

PhD student: Jannick Balleby Hansen

Contact: jbha@ase.au.dk

Project period: Nov 2011 to Dec 2016

Main supervisor: Prof. Rune Brincker

Research section: Civil and Architectural Engineering


Fullblown ODS

Anders Skafte

When measuring the dynamic properties of a civil structure, the information is always limited to the amount of sensors placed on the structure. This often results in sparse modal models and rough estimations.

The main focus of this project is to develop a model that provides information about the dynamics of a structure in points where no sensors have been placed.

This is done by making a transformation between a set of experimentally obtained mode shapes and a set of mode shapes from a Finite Element Model (FE). The overall principle is that a set of mode shapes can be described as a linear combination of another set of mode shapes as long as the changes between the two models are small. This is known as the Local Correspondence Principle.

The set of experimentally found mode shapes can be found by making an Operational Modal Analysis on the measured response and has the advantage of providing “true” information in a limited number of points.

On the other hand, the FE model provides a set of “fictive” mode shapes in a large number of points. As long as the FE model doesn’t differ too much from the real structure, the estimated mode shapes can be found successfully, making a linear transformation of the FE mode shapes.

The method will provide new ways of analysing structures. Displacements can be transformed to stains and stresses, which will be a helpful tool when analysing fatigue where the stress history is an important factor. Furthermore, the method will be suitable for monitoring of structures.

ABOUT THE PROJECT


Project title:
Fullblown ODS

PhD student: Anders Skafte

Contact: ask@ase.au.dk

Project period: Oct 2011 to Sept 2016

Main supervisor: Prof. Rune Brincker

Research section: Civil and Architectural Engineering

Complex Ventilation and Micro-Environmental Control in Livestock Housing

Hao Li

The aim of this project is to improve animal welfare and reduce environmental impact. A new concept for monitoring the thermal and airflow conditions in animal zones will be introduced. Furthermore, we will set up a dynamic predictive model to create a precision environment control strategy at individual animal or defined zone level.

Micro-complex ventilation involves integrating precision local ventilations in animal zones and near manure fouled floors or manure surfaces within the building ventilation. In order to gain knowledge about air motion and distribution in animal occupied zones and about system effects on emission reduction, an integrated micro ventilation concept in livestock housing will be investigated.

Data will be gathered by using both Computational Fluid Dynamics (CFD) simulations and full scale experiments. After the establishment of the system, optimisations are also needed. Then, to validate the optimal system, varied techniques including local cross ventilation, heat exchange and passive earth-air heat/cooling will be investigated. The proposed system combines the advantages of natural, mechanical and displacement ventilation, making it a technology with great efficiency and potential. 

ABOUT THE PROJECT


Project title:
Complex Ventilation and Micro-Environmental Control in Livestock Housing

PhD student: Hao Li

Contact: hao.li@eng.au.dk

Project period: Oct 2013 to Sept 2016

Main supervisor: Senior Researcher Guoqiang Zhang

Research section: Civil and Architectural Engineering


Smart Grid Flexibility Potential in Model-Based Building Control

Michael Dahl Knudsen

Much can be achieved by making the energy consumption of buildings more flexible so that the use of energy takes place at times when it is most convenient for the overall energy system.

This project examines the flexibility potential in relation to controlling the energy system of a building. This is done by using a model of a building that includes weather forecasts, energy prices and occupant behaviour.

The approach is essential to finding the combination of future actuator set-points that result in the best outcome with respect to indoor climate and economy.

ABOUT THE PROJECT


Project title:
Smart Grid Flexibility Potential in Model-Based Building Control

PhD student: Michael Dahl Knudsen

Contact: mdk@eng.au.dk

Project period: Aug 2013 to July 2016

Main supervisor: Assistant Prof. Steffen Petersen

Research section: Civil and Architectural Engineering


Incorporating Structural Health Monitoring in the Design of Slip Formed Concrete Wind Turbine Towers

Mads Knude Hovgaard

For decades, the prevailing material for very tall chimneys for power plants has been concrete. Combined, Rambøll and MT Højgaard have been involved in all phases of the construction of the very highest in Denmark.

Most modern wind turbine towers are tubular steel towers, and until now the high labour costs have tipped the scale in favour of steel towers. But as technology advances rapidly towards larger turbines, it is only natural to assume that concrete will be the new first choice for multi MW designs as it did for chimneys. For this scale of structures, the mechanical properties of concrete can be superior to those of steel if the experiences and know-how from concrete chimney construction are applied throughout the project.

Structural health monitoring (SHM) is the perpetual process of monitoring the structures' integrity. By equipping SHM to a civil structure, the owner is provided with decision support. So far, for the structures that have been equipped with SHM, the value in terms of total life-cycle benefits has rarely been estimated.

By associating a risk optimised decision policy, the SHM effort can be optimised and the initial target safety of the structure may be recalibrated upfront. In some cases, this translates into reductions on the Partial Safety Factors, leading to reductions on initial cost.

This project implements the risk based SHM system design, which is a research heavy topic, on the development of cast concrete wind turbine towers for multi MW turbines.

ABOUT THE PROJECT


Project title:
Incorporating Structural Health Monitoring in the Design of Slip Formed Concrete Wind Turbine Towers

PhD student: Mads Knude Hovgaard

Project period: Feb 2012 to Jan 2015

Main supervisor: Prof. Rune Brincker

Co-supervisor: Jens Christian Kirk, Rambøll

Research section: Civil and Architectural Engineering


Precision Zone Ventilation Design and Control in Pig Housing

Chao Zong

The ventilation system of animal houses is important in livestock production due to its significant influence on local thermal conditions, indoor air quality and emission to the neighbouring atmosphere.

Precision zone ventilation consisting of direct air supply into the Animal Occupied Zone (AOZ) and precision exhaust ventilation from the source zone can provide more efficient climate control and improved air quality. The objective of this project is to develop the knowledge of precision zone ventilation in pig production buildings, aiming at achieving more effective ventilation and improving indoor air quality as well as reducing the required capacity of air cleaning devises.

Experimental investigations are carried out both in a pig production facility and in a 2-D chamber in the laboratory. The two-dimensional Laser Doppler Anemometry (LDA) is used for measuring velocity speed and characterising flow type in the boundary layer. N2O is applied as tracer gas. The artificial pigs developed at APL are used to simulate the heat production of pigs at different locations. Computational Fluid Dynamics (CFD) is used for computer modelling.

ABOUT THE PROJECT


Project title:
Precision Zone Ventilation Design and Control in Pig Housing

PhD student: Chao Zong

Project period: Oct 2011 to Sept 2014

Main supervisor: Senior Researcher Guoqiang Zhang

Research section: Civil and Architectural Engineering


Continuous Members in Reinforced Concrete

Jakob Fisker

The vast majority of concrete slabs are only supplied with longitudinal reinforcement while expensive shear-reinforcement is only placed in case of shear forces of extraordinary magnitude. Thus, in most situations, the capacity of the slabs with respect to shear-forces is provided by a combination of the concrete itself along with the longitudinal reinforcement. Unfortunately, the fundamentals of this vital mechanism that allow for such structures to be designed are still not fully understood, and most models used for design are empirical and lack a physical and rational basis.

In addition, such slabs are often designed as statically indeterminate structures. In order to achieve a certain level of robustness, the final structure must possess a certain level of ability to withstand larger deformations without failing.

It is well known that the ability of reinforced concrete to deform is due to development of cracks. Hence, in this respect, the progressive development of cracks is beneficial. However, when considering members without shear-reinforcement, the same cracks also introduce certain “weakened” regions which effectively reduce the capacity with respect to shear.

The aim of the project is, among others, to increase the understanding of this rather delicate relation between the inevitable development of cracks and the shear-capacity of slabs.

ABOUT THE PROJECT


Project title:
Continuous Members in Reinforced Concrete

PhD student: Jakob Fisker

Project period: Aug 2012 to July 2014

Main supervisor: Prof. (Docent) Lars German Hagsten

Research section: Civil and Architectural Engineering