Abstract

This paper addresses an old and recurring theme in development economics: the slow adoption of new technologies by farmers in many developing countries. The paper explores a somewhat novel link to explain this puzzle -- the link between market access and the incentives to adopt a new technology when there are non-convexities. The paper develops a theoretical model to guide the empirical analysis, which uses spatially disaggregated agricultural production data from Spatial Production Allocation Model and Living Standards Measurement Study survey data for Nigeria. The model is used to estimate the impact of transport costs on crop production, the adoption of modern technologies, and the differential impact on returns of modern versus traditional farmers. To overcome the limitation of data availability on travel costs for much of Africa, road survey data are combined with geographic information road network data to generate the most thorough and accurate road network available. With these data and the Highway Development Management Model, minimum travel costs from each location to the market are computed. Consistent with the theory, analysis finds that transportation costs are critical in determining technology choices, with a greater responsiveness among farmers who adopt modern technologies, and at times a perverse (negative) response to lower transport costs among those who employ more traditional techniques. In sum, the paper presents compelling evidence that the constraints to the adoption of modern technologies and access to markets are interconnected, and so should be targeted jointly. Document type: Book

Abstract

This work deals with a comparative study of regulations, codes and standards for hydrogen fuelling station dedicated for light duty land vehicles in the following countries: United States (California), United Kingdom, Italy, Germany, Canada, Sweden, Norway, Denmark and Spain. The following technical components of a hydrogen fuelling station are included in the scope of the study: the hydrogen storage systems (cryogenic or compressed gases) and buffer storage, the compressor stations, the high pressure buffer storage, the cooling systems for hydrogen, the dispensing equipments and the dispensing area. The hydride storage, the pipelines, on site production and the hydrogen vehicle have been excluded. The analysis, performed in September 2014 in a report from INERIS DRA-14-141532-06227C BENCHMARK STATIONS-SERVICE HYDROGENE, is based on documents collected by bibliographic review and information obtained through a questionnaire sent to authorities and IA HySafe [1] members in the above mentioned countries. This paper gives a synthesis of the regulations and on permitting process in the different studied countries (including the new European Directive on the deployment of alternative fuels infrastructure in Europe [2]), it develops the required safety barriers in the different parts of a fuelling station and specially for the dispensing area, gives an overview of the different approaches for safety distances and processes to obtain licences to operate.

Abstract

The introduction of reinforced concrete as a structural material in American practice circa 1900 created unique challenges in design and analysis. Engineers and builders had to simultaneously determine proper constituent materials for the concrete, the relation between materials proportions and strength, and formulas for sharing load between steel and concrete. Early on there were only local building codes, which often treated concrete as masonry. This was followed, starting in 1909, by the reports of the “Joint Committee” which served as a de facto national code for concrete; the American Concrete Institute code was first independently published in 1941 and has been updated regularly since. All of the early codes, specifically including the Joint Committee report and the ACI code, used allowable-stress design with a linear-elastic model of flexure. Load-and-resistance factor design using an ultimate-strength model was first introduced in the US as an alternate method in the 1956 ACI code, was elevated to equal status with the 1963 code, and was made the standard in the 1971 code with the linear-elastic allowable-stress model as an alternate. Since the ultimate-strength model is generally accepted to more accurately represent flexure in reinforced concrete, the allowable-stress alternate was little used after the transition. Many details have changed minimally since the 1910s, including provisions for T beams that take advantage of the slab for additional compression flange area. The calculation of shear capacity in both concrete and web reinforcing changed minimally except for the transition from allowable-stress to load-and-resistance-factor design. Re-analysis of extant concrete structures designed before the 1956 code generally shows a pattern of significant excess capacity in flexure and limited excess capacity in shear. For members that are generally not controlled by one-way (beam) shear (two-way slabs and one- way slabs) the increase in flexure capacity governs; for members where one-way shear is a controlling factor, the small increase, no change, or decrease in shear capacity governs. Much of the current literature on evaluating the capacity of extant concrete structures focusses on strength degradation from material changes such as rusting rebar and from overall material changes such as carbonation. The presence of excess capacity should also be considered, and it is possible based on review of the governing codes and design methods to determine general patterns as to how much excess capacity may be expected.

Abstract

Prefabricated concrete piles have been used for the foundation of bigger buildings for about a century. Often a change in function, an addition (also vertically) or another type of alteration is required, resulting in different loads on the foundation. There are several complicating factors that return regularly in these assessments. The first one is a lack of data. Often drawings are missing or incomplete, e.g. showing only pile head dimensions or maximum calculated load but not the pile length, pile tip shape or material properties. Inspection is hard and only possible for the part directly under the pile head. And a third complication is that in The Netherlands there have only been official codes for piles since 1992. Various calculation and design methods from WWII until 1985 are discussed to see if there is any consistency that might lead to an indication of the load bearing capacity of piles in The Netherlands from that era. It is concluded that design rules for the load bearing capacity of concrete pile foundations in The Netherlands have been inconsistent over time. If the original detailed geotechnical calculations and/or structural drawings cannot be found in archives then the given ultimate loads cannot only not be exceeded; even if the load on a pile is currently less than stated on the technical specifications designers are advised not to increase the load.