Aggregate interlock is the dominant load transfer mechanism in non-dowelled Jointed Plain Concrete Pavements, as the innovative short concrete slabs. Although the Load Transfer Efficiency of this pavement innovation is based on that mechanism, the structural design methods do not relate the Load Transfer Efficiency by aggregate interlock with its direct cause, which is the Crack Width under the joints. The objective of the present article is to characterise in the laboratory the Load Transfer Efficiency−Crack Width relation for innovative short slabs Jointed Plain Concrete Pavements. Additionally, as an alternative to large-scale laboratory tests to study the Load Transfer Efficiency, a practical test on a reduced scale is proposed. The results confirmed that short slabs Jointed Plain Concrete Pavements with high-quality aggregates are able to provide adequate Load Transfer Efficiency (above 70%) without dowels bars. Based on the laboratory results, complemented with previous field data, a Load Transfer Efficiency−Crack Width curve is proposed and made available for structural design methods of short slabs Jointed Plain Concrete Pavements. Finally, the laboratory test on a reduced scale is useful to develop specific Load Transfer Efficiency−Crack Width relations using standard equipment available in traditional concrete laboratories.
Concrete is a material with high compressive strength, but predisposed to shrinkage cracking, rapid cracks propagation, and brittle failures. The incorporation of fibre is an acceptable solution to reduce these limitations. However, high cost and energy consumption related to man-made fibres have placed natural fibres as an attractive sustainable alternative, especially considering that different natural fibres are industrial waste (as the Eucalyptus globulus bark fibre). Still, natural fibres can produce an important reduction of concrete strength. Hence, the objective of this study is to evaluate the effects of Eucalyptus globulus bark fibre in traditional concrete mechanical properties as compressive and flexural strength. For this, an experimental program was developed in such a way that reduces the results uncertainties and increases the power of decision regarding the percentage and fibre conditions of the samples. The results indicate that, unlike other natural fibres, the traditional mechanical properties have a slight reduction and acceptable workability. This fact is more evident in the samples with 0.50% fibre with respect to the weight of cement. Therefore, reinforcing mortars and concrete with Eucalyptus globulus bark fibres emerges as an eco-friendly building alternative to reuse this industrial waste.
New automation technologies affect workers in a heterogeneous manner according to their demographic characteristics, skills, and the tasks they perform. In this paper we study the effects of automation on labor market outcomes in a developing country, Chile. We focus our analysis on the heterogeneous impacts of automation across cohorts. Does automation affect young workers differently than older workers? Do young workers tend to perform routine tasks? Are young workers in routine occupations more exposed to negative effects of technology? Our empirical strategy is based on exploiting differences in the routinization of tasks across districts and occupations and a change in the trend of automation technology adoption in Chile. We find that young workers are more easily displaced by automation than older workers of similar characteristics. At the same time, cohorts of young workers are more skilled and more mobile than older workers, which implies that they have good prospects of working in complement with automation technology in the near future. The young and unskilled are the most vulnerable group of workers.
We study the effect of a trade induced competitive shock given by rising import competition from China on Chilean manufacturing plants. For identification, we exploit the fact that, during 1995-2006, China import penetration (CIP) increased sharply in Chile, but this increment was quite different across manufacturing industries. We use Chinese export growth in high-income industry-country pairs as instrument for CIP. Our results suggest that plants in more exposed industries exhibit relative declines in revenue, employment and physical capital, and face a higher probability of exiting the panel than comparable plants in less exposed industries. All these effects are concentrated among establishments with low initial levels of productivity.
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