Search results for "Civil Engineering"
showing 10 items of 1216 documents
Būvmateriali: mūrnieka amata kursa (pēc Latvijas amatniecības kameras meistaru pārbaudes programas) lekciju konspekts
1939
Effect of two novel bio-based rejuvenators on the performance of 50% RAP mixes - a statistical study on the complex modulus of asphalt binders and as…
2019
An experimental study was conducted to evaluate the effectiveness of two bio-additives as rejuvenators on the properties of asphalt mixtures containing 50% RAP and their binder constituents containing 37% RAP binder. Before mixing, the rejuvenators were blended with fresh bitumen and the extracted and recovered RAP bitumen, and changes in the rheological properties of the binders were assessed using performance grading (PG) criteria. The results showed that both rejuvenators could improve the low-temperature performance of the aged RAP binder and restore its low-temperature properties. Master curves for the unaged, RTFO-aged, and PAV aged blends were constructed using both the Christensen-A…
Data Compression Approach for Long-Term Monitoring of Pavement Structures
2019
Pavement structures are designed to withstand continuous damage during their design life. Damage starts as soon as the pavement is open to traffic and increases with time. If maintenance activities are not considered in the initial design or considered but not applied during the service life, damage will grow to a point where rehabilitation may be the only and most expensive option left. In order to monitor the evolution of damage and its severity in pavement structures, a novel data compression approach based on cumulative measurements from a piezoelectric sensor is presented in this paper. Specifically, the piezoelectric sensor uses a thin film of polyvinylidene fluoride to sense the ener…
Full-scale validation of bio-recycled asphalt mixtures for road pavements
2019
Abstract Recycling of asphalt has become a well-established practice in many countries, however the road pavement industry remains a bulk consumer of extracted raw materials. Novel solutions that find root in circular economy concepts and life-cycle approaches are needed in order to enable optimisation of infrastructure resource efficiency, starting from the design stage and spanning the whole value chain in the construction sector. Itis within this framework that the present study presents a full-scale validation of asphalt mixtures specifically designed to ensure durability of flexible road pavements and at the same time enabling the reuse of reclaimed asphalt pavement (RAP) through the i…
Comparison among different rainfall energy harvesting structures
2018
In this paper, an experimental comparison between different rainfall harvesting devices through the study of the electrical rectifying circuit is proposed. In more detail, three harvesting structures are considered: the cantilever, the bridge and the floating circle. Different waveforms were acquired and discussed. The processed data were compared in order to suggest the best choice for the rectifying circuit, from the simplest one to that most frequently endorsed in the technical literature.
Construction sequence analysis of long-span cable-stayed bridges
2018
Abstract In cantilever construction of long-span cable-stayed bridges the stressing sequence of stays is fundamental for establishing the final configuration of the bridge. The structural behaviour of these bridges is usually evaluated through a forward staged construction analysis, in which the values of the prestressing forces to be applied to stays are the main unknowns. A unified procedure for determining the initial cable forces and for analyzing the entire sequence is presented here, considering the geometric nonlinearity of stays through the Dischinger equivalent elastic modulus. The target is the simultaneous determination of the initial cable forces with the simulation of the const…
Experimental investigation on the compressive behavior of short-term preloaded carbon fiber reinforced polymer-confined concrete columns
2017
Strengthening of concrete columns with fiber reinforced polymer sheets provides a good improvement to the existing structural members in terms of load and strain capacity due to the properties of the composite jacket. A proper knowledge of the load–strain response of the composite members is necessary to design retrofitting intervention of existing structures; however, so far the available design methods do not allow to take into account the effect of the possible presence of service loads on the compressive behavior of the reinforced columns. An experimental investigation on the compressive behavior of preloaded circular concrete columns reinforced with carbon fiber reinforced polymer was …
On Approximation of Entropy Solutions for One System of Nonlinear Hyperbolic Conservation Laws with Impulse Source Terms
2010
We study one class of nonlinear fluid dynamic models with impulse source terms. The model consists of a system of two hyperbolic conservation laws: a nonlinear conservation law for the goods density and a linear evolution equation for the processing rate. We consider the case when influx-rates in the second equation take the form of impulse functions. Using the vanishing viscosity method and the so-called principle of fictitious controls, we show that entropy solutions to the original Cauchy problem can be approximated by optimal solutions of special optimization problems.
Changes in Cement Paste and Mortar Fluidity after mixing induced by PCP: A parametric study
2006
International audience; The interaction mechanism between polycarboxylate-type superplasticizer (PCP) and cement hydration is not fully understood and incompatibilities between concrete and additive are sometimes observed. In some cases, the fluidity tends to increase (“overfluidification”) few minutes after mixing. This is a problem because the overfluidification leds to bleeding of the concrete which could be critical on job site. Our study consisted first in highlighting the phenomenon of “over-fluidification” by slump flow tests on mortar. Next, the time evolution of the rheological behaviour of cement pastes in the presence of PCP was analysed thanks to a rheometry protocol in order to…
SHORT-TERM PROCESSES OF RADIONUCLIDE IMMOBILIZATION IN CEMENT - A CHEMICAL APPROACH
1992
Abstract The ions released in solution by the constituents of cement (principally silicate, aluminate, OH and Ca ions) can combine with the anions and cations from nuclear wastes present in the mixing water to give very insoluble compounds that can fix these ions in the concrete matrix. In order to understand some of the particular physico-chemical processes involved in cement hydration in the presence of analogue elements, tricalcium silicate (C 3 S) was used instead of cement, which is too complex a mixture. It was found that the salt of a chemical analogue, a lanthanide salt, showed some accelerating effects when present in dilute amounts but resulted in large accelerating effects on QS …