Richard Walls | University of Stellenbosch (original) (raw)

Papers by Richard Walls

Fire

Informal settlements (ISs) are a high-risk environment in which fires are often seen. In 2019 alo... more Informal settlements (ISs) are a high-risk environment in which fires are often seen. In 2019 alone, 5544 IS fires were reported in South Africa. One of the main problems, when investigating an IS fire, is determining the fire cause. In the last 15 years, approximately 40% of the fire causes were classified as ‘undetermined’ in South Africa. Furthermore, the cases where the fire causes have been determined, do not provide the necessary information to comprehend why the fire started. This paper seeks to gain better insight with respect to fire causes by analysing the fire risk perception of IS inhabitants. To this end, a survey that was conducted in 2017, consisting of data from 2178 IS households, that were affected by a large-scale fire, was analysed. The survey consisted of questions relating to the fire risk perception with regards to the settlement in general, to the inhabitants’ own household, and about measures that could reduce fire risk. The analysis suggests that (a) the su...

Fire

Large conflagrations of informal settlements occur regularly, leaving thousands of people homeles... more Large conflagrations of informal settlements occur regularly, leaving thousands of people homeless daily and taking tens of thousands of lives annually. Over the past few years, a large amount of data has been collected from a number of full-scale informal settlement fire experiments. This paper uses that data with a semi-probabilistic fire model previously proposed by the authors, to illustrate the potential applications of the fire spread method proposed. The current model is benchmarked against a 20-dwelling full-scale informal settlement fire experiment, and the effects of the (a) ignition criteria, (b) wind direction, and (c) wind speeds on the predicted fire spread rates are investigated through the use of a parametric study. Colour maps of the fire spread rates and patterns are then used to visually interpret the effects of different types of fire scenarios and fire breaks. Finally, the fire spread capability within B-RISK is used to derive a linear equation for the potential...

This project will focus on investigating the behaviour of fire in informal settlements, to unders... more This project will focus on investigating the behaviour of fire in informal settlements, to understand the problem and develop better solutions. This will involve full-scale testing of individual shacks, multiple shacks and large-scale tests of up to 60-70 shacks, which will be burnt down in single experiments. The applicant will also be involved in overseeing a series of surveys done in informal settlements to understand the fire loads and fire risks in such areas. The research team will be developing models to understand and predict fire spread through such settlements.
The postdoctoral candidate will have the opportunity to work on individual research as well as to work within a team (doctoral, masters and Hons level students), and in addition, to gain experience in supervision of MEng and Honours students where possible. Two additional postdoctoral team members will be based at the University of Edinburgh and will work in close collaboration with the local team. The applicant will be required to travel to Edinburgh to engage with the team there for short periods.

Host: This will be a collaborative project between the University of Stellenbosch, University of Edinburgh and Western Cape Disaster Management, Fire & Rescue Services. The postdoctoral position is based within the Fire Engineering Research Unit at the department of Civil Engineering at Stellenbosch University.

Requirements:
• PhD with a background in engineering sciences, from fields such as civil, mechanical or chemical engineering. (Strong applicants with no PhD will be considered if sufficient experience in the field of fire engineering can be demonstrated, but should contact rwalls(AT)sun.ac.za to discuss).
• Understanding of fire / heat transfer / thermodynamics / temperature behaviour preferable.
• Understanding of informal settlements and associated problems beneficial.
• Research and publication record. We hope to publish much from this research.
• Good management skills as significant local management of big test setups will be required.
• Driving license to be able to visit test sites preferable.
• Willingness to learn new skills in an exciting new research field.
• Ability to speak other local languages such as Afrikaans or Xhosa beneficial, although not compulsory.

Commencement of duties: As soon as possible
Bursary: £1,500 per month (+-R25,000. Amount is fixed in pounds). Please note that postdoctoral fellows are not appointed as employees and their fellowships are awarded tax free. They are therefore not eligible for employee benefits.
Closing date: 24 May 2017 at 12h00.
Enquiries: Send a letter of application, accompanied by a comprehensive curriculum vitae, including list of publications and the names and contact details of at least two referees, to Dr Richard Walls at rwalls(AT)sun.ac.za.

Paper on the design and construction of a new glass factory in South Africa

In 2014 an innovative approach was followed with the final year structural engineering design pro... more In 2014 an innovative approach was followed with the final year structural engineering design project at Stellenbosch University, in which students had the tough task of designing a glass processing facility. The lessons learnt (both by the students and lecturers), challenges, successes and thoughts for the future are discussed in this article as we contemplate how to produce structural engineering graduates who are well equipped for the design office. Items such as site visits, oral presentations to practising engineers, YouTube videos, marshmallow & spaghetti models, and a lot of hard work helped create an interesting project (and hopefully better engineers for our society).

Believe it or not, when you set fire to a composite steel and concrete floor it just doesn’t want... more Believe it or not, when you set fire to a composite steel and concrete floor it just doesn’t want to fall over. It heats up to hundreds of degrees Celsius, beams buckle, floors sag, concrete can crack and the people still in the building at such temperatures are long dead – but floors don’t collapse because they become giant hanging catenaries. Using results from full-scale tests this behaviour can now be modelled and designed for, potentially leading to significant savings in the cost of passive fire protection on steelwork – with as much as 40-50% of floor beams not needing protection (see Figure 1). Passive protection such as intumescent paints, vermiculite boards and spray-on products can be very expensive. Thus, rational structural fire design methods, as presented here, can lead to significant savings. This article presents a brief introduction to a design method, the Slab Panel Method, which allows engineers to design composite floors for fire.

How is it that a building just prior to demolition, which now slightly resembles Swiss cheese, ca... more How is it that a building just prior to demolition, which now slightly resembles Swiss cheese, can still carry a lot of load and doesn’t fall down? Why is it that structural engineers cannot explain the demolition engineer’s “experience” that the Swiss-cheese-looking building is still safe enough for his team to be there?
This article briefly outlines research currently being undertaken at Stellenbosch University (SU), near Cape Town in South Africa, regarding how strong buildings are once they have been weakened by demolition teams. If buildings are weakened too much they may collapse prematurely, killing workers, and if they are not weakened enough they may not come down when you need them to. Hence, the research team aims to help the demolition industry by providing simple ways of determining whether weakened buildings are still safe. The work has been initiated by Jet Demolition, a company doing specialist demolition work in South Africa and abroad.

In South Africa engineers are starting to use the Eurocode guidelines for steelwork design, and i... more In South Africa engineers are starting to use the Eurocode guidelines for steelwork design, and it is important to understand the implications and differences in results that are obtained when applying the different codes. This paper presents a comparison between the Eurocode 1993-1-1:2005 and SANS 10162-1:2005 hot-rolled steelwork design codes. Numerical comparisons of predicted member design strengths for the important modes of failure
and the complexity of calculations are presented, along with considerations regarding the
parameters used in design. The following are explicitly shown for both codes: (a) differences in the classification of commonly used H, I, PFC and equal L sections, (b) differences in tension resistance calculations, (c) comparisons of all axial buckling curves, (d) calculations for a selection of members in flexural buckling which have different classifications, and (e) a summary of the shear resistances of commonly used H and I sections. It is shown that, on average, Eurocode 3 predicts higher member design strengths than the SANS 10162 code for most failure modes, primarily because of material partial safety factors closer to unity, less conservative buckling curves and the consideration of plastic resistance of sections. These EC3 design capacities can be higher by up to 11% for tension, 35% in compression, 31% in bending and 51% in shear, although there are cases where strengths of up to 33% lower were calculated, such as for an IPEAA-200 in shear. Results are influenced by design geometric tolerances, which are based on section classifications. The Eurocode’s equations and design methodologies are more complex and computationally demanding. Since South Africa has started moving in the direction of adapting or adopting Eurocodes with the SANS 10160 Loading Code (from EN 1) and SANS 10100 Structural Concrete Code (from EN 2), it should be considered whether or not the steelwork code should be adopted or adapted in a similar fashion in the future.

Courses notes on the design of structures in fire, with an emphasis on steel structures. Aspects ... more Courses notes on the design of structures in fire, with an emphasis on steel structures. Aspects such as fire curves, loading, design criteria, advanced design, resistance requirements, material response and other topics are addressed.

A spreadsheet for detailing rebar for reinforced concrete. Further instructions and a demonstrati... more A spreadsheet for detailing rebar for reinforced concrete. Further instructions and a demonstration can be found at:
https://www.youtube.com/watch?v=bXwoIuVxB7w

This dissertation presents a new method for the automated optimisation of structures. The method ... more This dissertation presents a new method for the automated optimisation of structures. The method has been developed to: (1) select sections to satisfy strength and deflection requirements using minimum material, and (2) efficiently group members.

This paper presents an iterative, automated method for optimizing structures with multiple deflec... more This paper presents an iterative, automated method for optimizing structures with multiple deflection criteria and load cases. The method is based on the principle of virtual work. Discrete sections are selected for structures with fixed geometries. An optimal structure is one which meets all strength and deflection criteria using minimal material. Four case studies are considered in this paper. A simple portal frame is presented to show how the method works. A 60-storey frame is optimized to demonstrate the effectiveness of the method for large structures. A warehouse designed by professional engineers is presented to show how the method can be used for structures subjected to complex loading conditions and deflection criteria. The automated method's solution is 4.5% lighter than the engineers'. Finally, a stepped cantilever is optimized and compared to results in the literature. Material savings of up to 14.4% are realized.

This paper investigates the distribution of mass and stiffness in multi-storey, ungrouped, unbrac... more This paper investigates the distribution of mass and stiffness in multi-storey, ungrouped, unbraced, optimized frames. Ungrouped structures are impractical to design and construct. However, optimized, ungrouped structures suggest how structural systems can be improved, and the loads can be carried more efficiently. The Virtual Work Optimization (VWO) method is used to minimize the weight of the structures considered. A 60-storey structure found in the literature is optimized to compare the distribution of mass and stiffness in grouped and ungrouped configurations. A parametric study of frames subjected to lateral loads, ranging in height from 5 to 30 stories, is carried out. Structures are designed to satisfy both strength and deflection criteria. Three different section databases are used for each case study to investigate whether the nature of discrete sections influences results. When ungrouped frames subject to lateral loads are optimized the total stiffness and mass per floor decrease approximately linearly with decreasing height, followed in some cases by a constant region of mass and stiffness, and a decrease in the foundation region. Distinct patterns emerge where members are stiffened on diagonal paths across the width of the structure. The distribution of mass in the frames suggests truss or megabrace behaviour.

An automated method for grouping discrete structural members is presented in this paper. The numb... more An automated method for grouping discrete structural members is presented in this paper. The number of groups is specified by the user, and members are grouped according to their mass per unit length. The method first optimizes a structure assuming that every member can have a different section. This is done using the Virtual Work Optimization (VWO) method, but any method can be used. The initial solution is the lightest possible, but the number of sections required make it impractical and uneconomical to construct. Next, an exhaustive search of all possible grouping permutations is carried out. The mass of the structure is predicted for each permutation.

The Virtual Work Optimization (VWO) method used in this paper is an automated and iterative metho... more The Virtual Work Optimization (VWO) method used in this paper is an automated and iterative method to minimize a given structure's mass. The method selects members' sections from a discrete database in such a way as to meet all strength and stiffness criteria. In the optimization process multiple load cases and deflection points are considered simultaneously. Within each iteration the efficiency of each section change is computed, and the section that produces the lowest mass increase per deflection decrease is chosen. The process continues until all the deflection criteria, as stipulated by the user or by the building code, are met. The power of the method is demonstrated by optimizing two warehouses using a truss and a cellular beam roof system. Savings in mass of up to 19.9% are computed when the roof system is a truss. However, fabrication and erection costs can offset material savings when cellular beams are used. Plots of members' mass per unit length, and deflection contribution, give valuable insight into the structures behaviour, and how the members can be grouped together to simplify the construction process.

Fire

Paper on the design and construction of a new glass factory in South Africa

This fellowship is a postdoctoral position working on the IRIS-Fire project investigating the beh... more This fellowship is a postdoctoral position working on the IRIS-Fire project investigating the behaviour of fire in informal settlements, to understand the problem and develop better solutions. Around 1 billion people internationally live in informal settlements (also known as slums, favelas, shantytowns, etc.). By developing a sound understanding of the problem many people living in poverty can be helped, whilst developing novel research.

The work of the fellowship will involve full-scale testing of individual shacks, multiple shacks and large-scale tests of up to 30-70 shacks, which will be burnt down in single experiments. The research team will be developing computer models to understand and predict fire spread through such settlements. Extensive full-scale testing, data analysis, research publication and computer modelling will form part of the work conducted by the successful candidate.

The postdoctoral candidate will have the opportunity to work on individual research as well as to work within a team (doctoral, masters and Hons level students), and in addition, to gain experience in supervision of MEng and Honours students where possible. Two additional postdoctoral team members are based at the University of Edinburgh and work in close collaboration with the local team. Applicant will be required to travel to Edinburgh to engage with the team there for short periods.

IRIS-Fire (Improving the Resilience of Informal Settlements to Fire) is an international and interdisciplinary research project. This international collaboration project, between the University of Edinburgh, UK and Stellenbosch University, South Africa, aims to develop fundamental understanding of the social, political, and technical issues regarding fire safety and fire spread within informal settlements situated in the Western Cape of South Africa and beyond. See the project website at: https://www.iris-fire.com/