Carlos Sousa

Numerical Evaluation of the Long-Term Behavior of Precast Continuous Bridge Decks

Continuous bridge decks constructed with precast girders undergo significant stress changes caused by the concrete delayed deformations because of creep and shrinkage. These effects must be taken into account in the design of new structures. The validation of the analysis procedures should ideally be carried out through the comparison between the calculations and the results observed in real structures. However, experimental results of the construction and long-term behavior of these structures are scarce. The construction of a major bridge in Portugal has provided the opportunity to monitor one such structure. This paper presents the monitoring campaign and the analysis strategy that was developed to assess the long-term variation of strains and stresses in precast continuous bridges. The numerical analysis was validated by comparison with the results observed in the real bridge. The consequences of carrying out simplified analyses based on limited information about the concrete properties and the construction sequence are also evaluated.

Naphthopyran-Based Silica Nanoparticles as New High-Performance Photoresponsive Materials

Hybrid nanomaterials based on the covalent grafting of silylated naphthopyrans (NPTs) onto silica nanoparticles (SiO2 NPs) were successfully prepared and studied as new photochromic materials. They were prepared by a two-step protocol consisting of (i) NPTs (derivatives from 2H-naphtho[1,2-b]pyran (2H-NPT) and 3H-naphtho[2,1-b]pyran (3H-NPT)) silylation by a microwave-assisted reaction between hydroxyl-substituted NPTs and 3-(triethoxysilyl)propyl isocyanate, followed by (ii) covalent post-grafting onto SiO2 NPs. In order to study the role of the silylation step, the analogous non-silylated nanomaterials were also prepared by direct adsorption of NPTs. The characterization techniques confirmed the successful NPTs silylation and subsequent grafting to SiO2 NPs. All SiO2-based nanomaterials revealed photoswitching behavior, following a biexponential decay. The SiO2 NPs functionalized with silylated 3H-NPTs (SiO2@S3 and SiO2@S4) presented the most promising photochromic properties, showing fast coloration/decoloration kinetics (coloring in 1 min under UV irradiation and fading in only 2 min) and high values of total color difference (ΔE*ab = 30-50). Also, the 2H-NPTs-based SiO2 NPs (SiO2@S1 and SiO2@S2) presented fast coloration and good color contrasts (ΔE*ab = 54), but slower fading kinetic rates, taking more than 2 h to return to their initial color. In contrast, the SiO2 NPs functionalized with non-silylated NPTs (SiO2@1 and SiO2@3) showed weaker color contrasts (ΔE*ab = 6-10) and slower fading kinetics, proving that the NPT silylation step was crucial to enhance the photochromic behavior of SiO2 NPs based on NPTs. Furthermore, the silylated-based nanomaterials showed good photostability upon prolonged UV light exposure, keeping their photochromic performance unchanged for at least 12 successive UV/dark cycles, anticipating interesting technological applications in several areas.

Assessing and monitoring urban resilience using COPD in Porto

BACKGROUND COPD morbidity is a good example of how the urban form may interfere with a diseases severity. Then, it may play an important role as a stimulus to increase the acceptability of several policy actions that aim to upgrade urban resilience. Despite the multiple dimensions of wellbeing, health is surely a key variable attracting everyones attention, which is thus more likely to be able to persuade people that actions that may at first seem undesirable are fundamental in improving urban sustainability and well-being. METHODS After creating a short list of socio-economic and environmental factors relating to the onset and aggravation of COPD, daily admissions distributions were compared using both a non-weighted and a weighted multi-criteria hierarchical analysis procedure. RESULTS Portos COPD Social and Environmental Inequalities Index (SEII), calculated with a hierarchical analysis procedure, accurately illustrates a great relationship between COPD admissions and adverse urban form variables. CONCLUSION COPD may be an important communication tool to stimulate the acceptability of some otherwise unpopular planning measures to improve urban resilience (sustainability and well-being).

Screen-Printed Photochromic Textiles through New Inks Based on SiO2@naphthopyran Nanoparticles

Photochromic silica nanoparticles (SiO2@NPT), fabricated through the covalent immobilization of silylated naphthopyrans (NPTs) based on 2H-naphtho[1,2-b]pyran (S1, S2) and 3H-naphtho[2,1-b]pyran (S3, S4) or through the direct adsorption of the parent naphthopyrans (1, 3) onto silica nanoparticles (SiO2 NPs), were successfully incorporated onto cotton fabrics by a screen-printing process. Two aqueous acrylic- (AC-) and polyurethane- (PU-) based inks were used as dispersing media. All textiles exhibited reversible photochromism under UV and solar irradiation, developing fast responses and intense coloration. The fabrics coated with SiO2@S1 and SiO2@S2 showed rapid color changes and high contrasts (ΔE*ab = 39-52), despite presenting slower bleaching kinetics (2-3 h to fade to the original color), whereas the textiles coated with SiO2@S3 and SiO2@S4 exhibited excellent engagement between coloration and decoloration rates (coloration and fading times of 1 and 2 min, respectively; ΔE*ab = 27-53). The PU-based fabrics showed excellent results during the washing fastness tests, whereas the AC-based textiles evidenced good results only when a protective transfer film was applied over the printed design.

Long-term monitoring and assessment of a precast continuous viaduct

Precast girders have recently been widely employed in the construction of bridges and viaducts. The new bridge over the Tagus River in Portugal, the Lezíria Bridge, comprehends a 9160 m long south approach viaduct, which was built with precast girders made continuous in situ. Given the relevance of this construction, a long-term monitoring system was implemented and measurements were taken since the start of the construction. The observed parameters were concrete strains and temperatures, deck rotations, joint displacements, accelerations and also environment temperature and relative humidity. The work presents the precast structure, the monitoring system and the appraisal of a statistical procedure for the long-term assessment of the structural behaviour. This procedure is based on prediction models, which establish the normal correlation patterns between environmental and material parameters (such as concrete temperature and shrinkage strains), and the observed structural response in terms of strains, rotations and movements of expansion joints. The calculation of the normal correlation pattern comprehends the minimisation of a square error. By applying the prediction model to the structural response measured in the south approach viaduct of the Lezíria Bridge, it was found that this methodology is a feasible tool for real-time damage detection of bridges.

The Accuracy of the Heat Index to Explain the Excess of Mortality and Morbidity During Heat Waves - a Case Study in a Mediterranean Climate

Abstract The aim of this contribution was to evaluate the accuracy of a well known human comfort index, the heat index, to anticipate the effects of the July 2006 heat wave in mortality (all causes) and morbidity (all causes, respiratory and circulatory disease). Our assessment was done to all citizens, to people of the 75+ cohort and to each gender, in Porto. For further statistical analysis, we calculated an expected number of admissions by averaging the admissions recorded during the comparison period. The 95% confidence interval was calculated, using a standard method based on the t-distribution, for differences between independent means with different population variances, using the Leveane test to evaluate the variance’s homogeneity. During the 2006 heat wave, a 52% mortality excess was registered relatively to the expected mortality (p < 0.001), for all cohorts of the population. The admissions excess for all ages included the admissions due to respiratory diseases (p < 0.029), pneumonia (p < 0.001) and chronic obstructive pulmonary disease (p < 0.001). For the 75+ cohort, the admissions due to respiratory diseases (p < 0.017), pneumonia (p < 0.001) and heart failure (p < 0.610) were also statistically high. The obtained results confirm that the heat index is a truthful method to anticipate the negative impacts of heat waves in human health even in climate contexts adapted to hot summers like at Porto - a Mediterranean tempered climate. The impacts of July 2006’s heat wave in the increase of mortality (all causes) and in respiratory morbidity (all population and 75+cohort) was evident.

Push-Off Tests in the Study of Cyclic Behavior of Interfaces between Concretes Cast at Different Times

AbstractThe knowledge about the cyclic behavior and effects of fatigue on interfaces between concrete cast at different times, subjected to shear stress, is still very limited. This aspect is particularly relevant in structures subjected to important cyclic loads, such as railway bridges. In this context, first, a brief state of the art on the monotonic and cyclic behavior of interfaces between concretes cast at different times is presented. Then, the test campaign, which was aimed at obtaining experimental support for modeling the behavior of such interfaces, subjected to a high number of load cycles, is described, and the corresponding results are discussed and analyzed in terms of slip and crack opening, stress variations in the monotonic tests, failure mode, and number of resisting load cycles. It was further observed that the number of resisting load cycles increases as the maximum load level decreases. On the basis of this evidence, an experimental S-N curve was set for this type of interface.

Novel L-prolyl-L-leucylglycinamide (PLG) tripeptidomimetics based on a 2-azanorbornane scaffold as positive allosteric modulators of the D2R

An efficient and straightforward orthogonal methodology was successfully developed to achieve constrained l-prolyl-l-leucylglycinamide (PLG) analogues starting from two proline mimetics based on a 2-azanorbornane scaffold. A preliminary dopamine D2 receptor radiolabeled binding assay with [3H]-N-propylnorapomorphine shows that enantiopurity of PLG peptidomimetics based on 2-azanorbornane is a requirement to achieve statistically significant positive modulators of the D2 receptor. This is the first documented active peptidomimetic of PLG whose bioactivity is not correlated with the C-terminal carboxamide pharmacophore and which cannot adopt the hypothesized type II β-turn conformation.

New L-Serine Derivative Ligands as Cocatalysts for Diels-Alder Reaction

New L-serine derivative ligands were prepared and tested as cocatalyst in the Diels-Alder reactions between cyclopentadiene (CPD) and methyl acrylate, in the presence of several Lewis acids. The catalytic potential of the in situ formed complexes was evaluated based on the reaction yield. Bidentate serine ligands showed good ability to coordinate medium strength Lewis acids, thus boosting their catalytic activity. The synthesis of the L-serine ligands proved to be highly efficient and straightforward.

Enantiopure synthesis of 7-(1-pyrindanyl)propargyl ethers as rasagiline analogues via chemical or enzymatic resolution of 1-pyrindan-7-ol

In this work, the enantiopure synthesis of 7-(1-pyrindanyl)propargyl ethers – rasagiline analogues – via chemical and/or enzymatic resolution of the racemic precursor 1-pyrindan-7-ol is described. (R)-Methoxyphenylacetic acid – (R)-MPAA – and (S)-methoxyphenylacetic acid – (S)-MPAA were used as chemical resolution agents, whereas Candida antarctica lipase B (CALB) was employed as kinetic resolution catalyst. The enzymatic resolution was successfully achieved by two different approaches: (1) transesterification of racemic 1-pyrindan-7-ol, which was found to selectively acylate the (R)-enantiomer with high efficiency; (2) hydrolysis of the racemic 7-(1-pyrindanyl)acetate, which was also highly selective to the (R)-enantiomer. The enzymatic hydrolysis was performed in a non-aqueous solvent using a lipase with significant absorbed water content. The configuration of the two enantiomers of 1-pyrindan-7-ol (and consequently of the 7-(1-pyrindanyl)propargyl ethers) were unequivocally determined by X-ray crystallography and/or specific optical rotation.