Castor Roots In A Vertic Inceptisol

The root systems of 4 large and 4 small, mature castor (Ricinus communis) cv. Acuna plants were excavated. Large and small plants had similar root:shoot ratios but roots of small plants were longer per unit weight. Soil factors in or near the surface of the C1 horizon, probably higher gravel and carbonate content, apparently restricted root penetration

Development of a composite prototype with GFRP profiles and sandwich panels used as a floor module of an emergency house

A series of experimental tests carried out on a composite prototype to be used as a floor module of an emergency house is presented in this paper. The prototype comprises a frame structure formed by GFRP pultruded profiles, and two sandwich panels constituted by GFRP skins and a polyurethane foam core that configures the floor slab. The present work is part of the project “ClickHouse – Development of a prefabricated emergency house prototype made of composites materials” and investigates the feasibility of the assemblage process of the prototype and performance to support load conditions typical of residential houses. Furthermore, sandwich panels are also independently tested, analysing their flexural response, failure mechanisms and creep behaviour. Obtained results confirm the good performance of the prototype to be used as floor module of an emergency housing, with a good mechanical behaviour and the capacity of being transported to the disaster areas in the form of various low weight segments, and rapidly installed. Additionally, finite element simulations were carried out to assess the stress distributions in the prototype components and to evaluate the global behaviour and load transfer mechanism of the connections.Quadro de Referência Estratégica Nacional (QREN)FEDER funds through the Operational Program for Competitiveness Factors – COMPETE and the Portuguese National Agency of Innovation (ADI) - project no. 3896

Experimental behaviour of non-seismical RWS connections with perforated beams under cyclic actions

The use of perforated (in particular cellular and castellated) beams has become widespread as their manufacturing processes keep minimising wasted material and has become cost-effective by reducing self-weight of steel structures, while allowing for larger clear spans. Although their behaviour to time-invariant vertical loads has been extensively investigated and validated in laboratory setups, their response to reversible actions has not been explored to the same extent. This paper presents results of cyclic load tests of beam-column reduced web section (RWS) connections, considering setups representative of what is observed in low-rise buildings in the UK; a region with sparse seismicity. Results show that RWS connections on these frames can achieve stable hysteresis loops without significant strength degradation, due to the simultaneous occurrence of yielding of the critical cross-section and development of a Vierendeel mechanism on the edges of the perforations (web openings). Also, inelastic action is mostly observed within the beam, thus being successful in protecting the beam-column connection. Performance particularly exceeds what is observed for a benchmarking RBS connection styled according to the same underlying assumptions, hinting that RWS connections could be a more suitable solution for structural retrofitting in regions where seismicity is sparse

A numerical investigation on the fire response of a steel girder bridge

The response of bridges subject to fire is an under researched topic despite the number of bridge failures caused by fire. Since available data shows that steel girder bridges are especially vulnerable to fire, this paper delves into their fire response by analyzing with a 3D numerical model the response of a typical bridge of 12.20 m span length. A parametric study is performed considering: (1) two possibilities for the axial restraint of the bridge deck, (2) four types of structural steel for the girders (carbon steel and stainless steel grades 1.4301, 1.4401, and 1.4462), (3) three different constitutive models for carbon steel, (4) four live loads, and (5) two alternative fire loads (the hydrocarbon fire defined by Eurocode 1 and a fire corresponding to a real fire event). Results show that restraint to deck expansion coming from an adjacent span or abutment should be considered in the numerical model. In addition, times to collapse are very small when the bridge girders are built with carbon steel (between 8.5 and 18 min) but they can almost double if stainless steel is used for the girders. Therefore, stainless steel is a material to consider for steel girder bridges in a high fire risk situation, especially if the bridge is located in a corrosive environment and its aesthetics deserves special attention. The methodology developed in this paper and the results obtained are useful for researchers and practitioners interested in developing and applying a performance-based approach for the design of bridges against fire. © 2012 Elsevier Ltd. All rights reserved.Funding for this research has been provided to Dr. Paya-Zaforteza by the Spanish Ministry of Education (contract number EX-2008-0669 of the Program for Postdoctoral Stays), the Spanish Ministry of Economy and Competitiveness (research project BIA 2011-27104) and the Universitat Politecnica de Valencia (Research and Development Support Program PAID-06-11). Funding has also been provided to Dr. Maria Garlock by the National Science Foundation (NSF) under award number CMMI-1068252. All opinions expressed in this paper are the authors' and do not necessarily reflect the policies and views of the sponsors.Paya-Zaforteza, I.; Garlock, ME. (2012). A numerical investigation on the fire response of a steel girder bridge. Journal of Constructional Steel Research. 75:93-103. https://doi.org/10.1016/j.jcsr.2012.03.012S931037

Characterization of Emissions from a Desktop 3D Printer

3D printers are currently widely available and very popular among the general public. However, the use of these devices may pose health risks to users, attributable to air-quality issues arising from gaseous and particulate emissions in particular. We characterized emissions from a low-end 3D printer based on material extrusion, using the most common polymers: acrylonitrile-butadiene-styrene (ABS) and polylactic acid (PLA). Measurements were carried out in an emission chamber and a conventional room. Particle emission rates were obtained by direct measurement and modeling, whereas the influence of extrusion temperature was also evaluated. ABS was the material with the highest aerosol emission rate. The nanoparticle emission ranged from 3.7.10(8) to 1.4.10(9) particles per second (# s(-1)) in chamber measurements and from 2.0.10(9) to 4.0.10(9) # s(-1)in room measurements, when the recommended extruder temperature was used. Printing with PLA emitted nanoparticles at the rate of 1.0.10(7) # s(-1) inside the chamber and negligible emissions in room experiments. Emission rates were observed to depend strongly on extruder temperature. The particles' mean size ranged from 7.8 to 10.5 nanometers (nm). We also detected a significant emission rate of particles of 1 to 3nm in size during all printing events. The amounts of volatile organic and other gaseous compounds were only traceable and are not expected to pose health risks. Our study suggests that measures preventing human exposure to high nanoparticle concentrations should be adopted when using low-end 3D printers.Peer reviewe