Small is Possible by George McRobie and Small is Beautiful and Possible... But Access to Land is Critical by Robert A. Williams

On April 29 1982 George McRobie visited Simon Fraser University to deliver a lecture on his favourite topic - "appropriate" technology. To give special point to that occasion and underline the relevance of the topic for British Columbia Robert Williams was invited to give a counterpoint talk. This Siamese-twin paper is the result of that juxtaposition.  George McRobie spent some fifteen years with the National Coal Board in Britain, during which he was closely associated with E.F. Schumacher, author of Small is Beautiful. In 1965 they founded the Intermediate Technology Development Group in London, U .K., of which Mr. McRobie is now chairman. A graduate in economics of the London School of Economics Mr. McRohie is the author of Small is Possible. Robert A. Williams is best known in British Columbia for his political activities, especially as Minister of Lands, Forests and Water Resources in the NDP government from 1972 to 1975. Having degrees in economics and urban planning from the University of British Columbia he has a special interest in land issues

Hydrological modelling improvements required in basins in the Hindukush-Karakoram-Himalayas region

Millions of people rely on river water originating from basins in the Hindukush-Karakoram-Himalayas (HKH), where snow- and ice-melt are significant flow components. One such basin is the Upper Indus Basin (UIB), where snow- and ice-melt can contribute more than 80% of total flow. Containing some of the world’s largest alpine glaciers, this basin may be highly susceptible to global warming and climate change, and reliable predictions of future water availability are vital for resource planning for downstream food and energy needs in a changing climate, but depend on significantly improved hydrological modelling. However, a critical assessment of available hydroclimatic data and hydrological modelling in the HKH region has identified five major failings in many published hydro-climatic studies, even those appearing in reputable international journals. The main weaknesses of these studies are: i) incorrect basin areas; ii) under-estimated precipitation; iii) incorrectly-defined glacier boundaries; iv) under-estimated snow-cover data; and v) use of biased melt factors for snow and ice during the summer months. This paper illustrates these limitations, which have either resulted in modelled flows being under-estimates of measured flows, leading to an implied severe water scarcity; or have led to the use of unrealistically high degree-day factors and over-estimates of glacier melt contributions, implying unrealistic melt rates. These effects vary amongst sub-basins. Forecasts obtained from these models cannot be used reliably in policy making or water resource development, and need revision. Detailed critical analysis and improvement of existing hydrological modelling may be equally necessary in other mountain regions across the world

Unified geometrical framework for the plastic design of reinforced concrete structures

© 2020 The Authors. Structural Concrete published by John Wiley & Sons Ltd on behalf of International Federation for Structural Concrete. Although the analysis and design of structures in static equilibrium can be intuitively carried out using simple equilibrium-based methods such as graphic statics, the application of these methods to engineering problems that take into consideration specific material properties is generally limited. Within the domain of reinforced concrete, existing geometric approaches for developing stress fields and yield lines based on the theory of plasticity are especially useful. However, these approaches usually rely on iterative constructions and are generally limited to two-dimensional cases. By taking advantage of graphic statics, this article introduces the theoretical basis for an entirely geometrical method to generate discrete stress fields and yield line patterns in two- and three-dimensional reinforced concrete structures. The proposed approach is based on the use of reciprocal stress functions and the relationship between form and force diagrams

Applications of graphic statics to analysis and design of reinforced concrete: Stress fields and yield lines

© Fédération Internationale du Béton – International Federation for Structural Concrete. Graphic statics can be effectively used for the analysis and design of structures in static equilibrium and for solving engineering problems related to specific materials, most notably, reinforced concrete. In this regard, methods for the construction of stress fields and yield lines, based on the theory of plasticity, are particularly valuable; however, their automation and generalisation to the third dimension are still open research topics. This paper introduces a unified method based on graphic statics for the generation of discrete stress fields of 2D and 3D reinforced concrete structures and the definition of admissible yield line patterns in concrete slabs. The presented approach relies on the construction of reciprocal stress functions, and the link between form and force diagrams through Minkowski sums

Mechanisms and states of self-stress of planar trusses using graphic statics, part II: Applications and extensions

This paper extends the overview (Mitchell et al. [11]) relating graphic statics and reciprocal diagrams to linear algebra-based matrix structural analysis. Focus is placed on infinitesimal mechanisms, both in-plane (linkage) and out-of-plane (polyhedral Airy stress functions). Each self-stress in the original diagram corresponds to an out-of-plane polyhedral mechanism. Decomposition into sub-polyhedra leads to a basis set of reciprocal figures which may then be linearly combined. This leads to an intuitively-appealing approach to the identification of states of self-stress for use in structural design, and to a natural “structural algebra” for use in structural optimisation. A 90° rotation of the sub-reciprocal generated by any sub-polyhedron leads to the displacement diagram of an in-plane mechanism. Any self-stress in the original thus corresponds to an in-plane mechanism of the reciprocal, summarised by the equation s = M* (where s is the number of states of self-stress in one figure, and M* is the number of in-plane mechanisms, including rigid body rotation, in the other). Since states of self-stress correspond to out-of-plane polyhedral mechanisms, this leads to a form of “conservation of mechanisms” under reciprocity. It is also shown how external forces may be treated via a triple-layer Airy stress function, consisting of a structural layer, a load layer, and a layer formed by coordinate vectors of the structural perimeter

Engineering as a tool for improving human habitat

The conventional approaches to poverty alleviation in the slums entail a cocktail of interventions in health, education, governance and physical improvements, often stretching the scarce resources far and thin. Driven by the 'poverty' mindset, physical measures such as minimal paving, public water posts and community latrines actually brand the slums apart instead of assimilating them into the urban infrastructure fabric. The concept of Slum Networking proposes comprehensive water and environmental sanitation infrastructure as the central and catalytic leverage for holistic development. At costs less than the conventional 'slum' solutions, it tries to penetrate a high quality urban infrastructure net deeply into the slums to assimilate them into the city rather than lock them in as disadvantaged islands. Further, it transcends resource barriers and 'aid' through innovative partnerships and the latent resource mobilisation potential of the so-called 'poor'. This paper examines Slum Networking as implemented in Sanjaynagar in Ahmedabad, India and compares it with a similar settlement with no interventions in Ahmedabad. It assesses the knock-on impact of physical infrastructure on health, education and poverty. Finally, it evaluates the multiplier effect of physical infrastructure and the partnerships on the subsequent investments by the community in its own shelter and habitat

The rotational stiffness of cross-laminated timber half-lap joints

Half-lap joints in cross-laminated timber are often conservatively assumed to have no rotational stiffness, preventing applications where the cross-joint stiffness could be utilised. The stiffness of a typical half-lap joint was derived from static four point bend tests, with experiments carried out through a combination of laboratory testing and finite element modelling. A simplified calculation method was developed to predict the rotational stiffness from the joint configuration and material properties. This was incorporated into a spreadsheet design tool for use by the industry partner

Perpendicular-to-grain compression behaviour of screw reinforced timber and a novel application of digital image correlation

This project investigates various factors which influence the behaviour of a timber roof structure designed by Smith & Wallwork Engineers. The first part of the project focused on material of sweet chestnut, where Digital Image Correlation (DIC) was employed to obtain values for the shear modulus. DIC was able to implement the shear field test method prescribed in BS EN 408:2010, along with two new methods developed based on additional information available through DIC. These methods were accurate, fast to implement, and potentially more robust than the shear field test method. A method to estimate the true value of the Timoshenko shear coefficient was also developed. The second section of the project involved physical testing of portions of the roof structure to investigate the behaviour of screw-reinforced and unreinforced timber loaded perpendicular to grain. Together with finite element modelling, it was noticed that a key aspect of the connection's behaviour was the axial force transfer between overlapping screws via shear in the timber, and the resulting relative displacement between the screws. A simple spring model was developed to characterise the compression stiffness of the roof which can now be used in reverse to calculate the forces due to moisture expansion or contraction

Accuracy assessment of ISI-MIP modelled flows in the Hidukush-Karakoram-Himalayan basins

Large Asian rivers heading in the Hindukush-Karakoram-Himalayan mountains, and whose streamflow includes significant snow-melt and glacier-melt components, may be highly susceptible to climate warming and pattern changes. Millions of people depend on these streamflows for agriculture and power generation. Reliable predictions of future water availability are therefore needed for planning under a changing climate, and depend on the quality of hydro-climatic modelling. ISI-MIP provides global hydrological modelling results, and need validation at regional scale. This study evaluates the accuracy of modelled flows from the hydrological models used in ISI-MIP, in various sub-basins of the Upper Indus Basin (UIB) and for the reference period 1985-1998. The modelled flows are based on six hydrological models, which are: i) H08, ii) VIC, iii) WaterGAP, iv) WBM, v) MPI-HM, vi) PCR-GLOBWB. Of these models, H08 and VIC are energy-based hydrological models, while the others are temperature-based hydrological models. WBM and MPI are not suitable for the UIB, due to significant under-estimation (by 70-90%) of measured flows by their modelled flows. The remaining four models provide consistent, but still significantly under-estimated flows (up to 60% of measured flows) in all sub-basins, except the Kharmong basin. Monthly differences between modelled and measured flows vary between sub-basins, but with noticeable over-estimation in winter-spring months and under-estimation during summer months. Accuracy of the bias-corrected precipitation data sets (based on five GCMs) used in the ISI-MIP hydrological models has been assessed, using a basin-wide water balance assessment method. This method shows that all precipitation data sets significantly under-estimate precipitation in the UIB, particularly in the Karakoram sub-basins. The selected ISI-MIP hydrological models have used precipitation data which are under-estimates, which may be a main reason for under-estimated flows. ISI-MIP hydrological modelling needs to use the best available precipitation data for the UIB, but other input data and calibration parameters also need revision. An important message from this study is that caution must be exercised in selecting precipitation data sets and hydrological models in alpine regions such as the Hindukush-Karakoram-Himalayas

The role of infrastructure in improving human settlements

This paper considers how the provision of integrated household-level infrastructure – particularly water and environmental sanitation (including water supply, sewerage, roads, storm drainage and solid waste management) – can play a leading role in improving the conditions in slum settlements. Around 700 socio-economic interviews were carried out in India and South Africa to investigate an innovative approach called slum networking, which sees the strong correlation between slum locations and drainage paths as an opportunity for improving the wider urban environment. This recognition allows resources to be mobilised locally, thereby removing the need for external aid funding. The evidence from the 700 families shows that communities perceive water and sanitation inputs to be their top priority and are willing to contribute to the costs. If slum upgrading is led with access to integrated water and environmental sanitation at household level with community contributions to the cost of infrastructure, then slum communities subsequently invest considerably greater sums in improved housing and education, with longer term contributions to poverty alleviation, improvements in health and literacy and an increase in disposable incomes