Ricardo Monteiro

Evaluation of Nonlinear Static Procedures in the Assessment of Building Frames

In recent years a number of nonlinear static procedures (NSPs) have been developed and proposed. Such pushover-based seismic assessment procedures are relatively straightforward to employ and are generally chosen over nonlinear dynamic analysis, especially within the realm of design office application. Parametric comparisons between the different NSPs available, however, are still somewhat sparse. In this work, five commonly employed NSPs (the N2 method, capacity spectrum method, modal pushover analysis, adaptive modal combination procedure, and the adaptive capacity spectrum method) are applied in the assessment of 16 frames subjected to a large number of input motions with a view to assess the accuracy level of such approaches through comparison with nonlinear dynamic analysis results. The evaluation shows that all the NSPs are able to accurately predict displacements and to produce reasonable estimates for other response parameters, with limited dispersion. Even though no single NSP tested led to consistently superior results, modal pushover analysis and the adaptive capacity spectrum method seemed to perform slightly better.

Assessment of Continuous Span Bridges through Nonlinear Static Procedures

Nonlinear static procedures constitute an important tool in design office application of performance-based earthquake engineering concepts, and for this reason, they have been extensively developed and promoted in the last decade or so. However, these efforts focused predominantly on the assessment of buildings, rather than bridges, and hence there is currently a need to verify the validity in the application of such pushover-based methods for the assessment of bridges or viaducts. In this work, therefore, by considering a wide set of bridge configurations subjected to equally varying seismic input intensity levels, four commonly employed nonlinear static procedures (CSM, N2, MPA, ACSM) are scrutinized and compared, with a view to establish their adequacy for the seismic assessment of existing continuous span bridges. Results seem to indicate that all methods are able to predict displacement response with good accuracy, while force estimation, on the other hand, is reasonably attained only by those approaches where higher modes effects are explicitly accounted for.

Assessment of indoor airborne contamination in a wastewater treatment plant

The main objective of this work was to quantify and characterize the major indoor air contaminants present in different stages of a municipal WWTP, including microorganisms (bacteria and fungi), carbon dioxide, carbon monoxide, hydrogen sulfide ammonia, formaldehyde, and volatile organic compounds (VOCs). In general, the total bacteria concentration was found to vary from 60 to >52,560xa0colony-forming units (CFU)/m3, and the total fungi concentration ranged from 369 to 14,068xa0CFU/m3. Generally, Gram-positive bacteria were observed in higher number than Gram-negative bacteria. CO2 concentration ranged from 251 to 9,710xa0ppm, and CO concentration was either not detected or presented a level of 1xa0ppm. H2S concentration ranged from 0.1 to 6.0xa0ppm. NH3 concentration was <2xa0ppm in most samples. Formaldehyde was <0.01xa0ppm at all sampling sites. The total VOC concentration ranged from 36 to 1,724xa0μg/m3. Among the VOCs, toluene presented the highest concentration. Results point to indoor/outdoor ratios higher than one. In general, the highest levels of airborne contaminants were detected at the primary treatment (SEDIPAC 3D), secondary sedimentation, and sludge dehydration. At most sampling sites, the concentrations of airborne contaminants were below the occupational exposure limits (OELs) for all the campaigns. However, a few contaminants were above OELs in some sampling sites.

Using the Conditional Spectrum Method for Improved Fragility Assessment of Concrete Gravity Dams in Eastern Canada

The accurate estimation of fragility functions requires the proper selection of ground motion records at different intensity levels. However, most of the available fragility assessments of concrete dams use the same records at all intensity levels and often selects them with an inadequate target spectrum. In order to improve the fragility assessment of such structures, this paper proposes the use of records selected with the Conditional Spectrum (CS) method within a multiple stripes analysis. The approach is applied to a dam in Eastern Canada, and a comparison with the methodology used by other studies is done. It is shown that the approach proposed herein allows for the reduction of the seismic response and fragility of the dam. Moreover, the uncertainty related to material properties becomes less significant when using the CS method, and the fragility curves could be reasonably estimated by considering the ground motions as the only source of uncertainty.

Synthesis and characterization of N-modified titania nanotubes for photocatalytic applications

The modification of titanate nanotubes (TiNT) with nitrogen (NTiNT) was accomplished through impregnation method. TiNT were synthesized via hydrothermal treatment of titania powders in NaOH solution at 130xa0°C for 48xa0h. The obtained samples were characterized by UV–Vis absorption spectroscopy, Brunauer–Emmett–Teller (BET) surface area, XRD, TEM, XPS, and TG analysis. Structure, morphology, composition, and visible light absorption property of nitrogen-modified TiO2 nanotubes are found to depend on the nitrogen content and not on the calcination temperature for the range used in this work. The photocatalytic activity of these nanotubes was investigated for the degradation of methylethylketone (MEK) and hydrogen sulfide (H2S) under ultraviolet and solar light radiation. MEK is very resistant to photocatalytic degradation with the prepared materials;, however, the results show that modification of the TiNT with nitrogen in a proportion of 1 to 1 (TiNT to urea weight ratio) and calcination at 400xa0°C lead to materials with high photocatalytic activity under ultraviolet radiation and moderate photocatalytic activity under solar radiation for degradation of H2S.

Critical Assessment of Intensity Measures for Seismic Response of Italian RC Bridge Portfolios

ABSTRACT The seismic assessment of a road network depends largely on the characterization of the fragility of its bridge components. The accuracy of bridge seismic demand estimates and the use of proper intensity measures (IM) will significantly influence such task. The available literature has mainly focused on buildings or a limited number of bridge configurations and IMs, which may not be representative for bridge portfolio assessment studies. In this paper, the correlation quality between a larger pool of traditional and innovative IMs and the nonlinear dynamic response of typical Italian RC bridges is investigated to identify the best-performing IMs.

USING DIFFERENT UNCERTAINTY MODELS FOR SEISMIC ASSESSMENT OF RC BRIDGES

The seismic assessment of structures depends on a large number of aleatory and epistemic uncertainties, which are majorly associated to the estimation of the structural demand and capacity, both usually featuring considerable dispersion levels, particularly when reinforced concrete structures are being assessed. When focusing on bridges, additional complexity may be introduced by the irregular behaviour in the transverse direction. Several procedures may be used for the assessment of the seismic safety of bridges, deterministic or probabilistic, and all rely on an accurate prediction of the demand, obtained via linear or nonlinear static or dynamic analysis. This work employs both static and dynamic analysis methods for demand estimation within a relatively straightforward framework to compute the failure probability of existing bridges. Different variables typically considered in a seismic assessment procedure (geometry, material properties, earthquake records, intensity level) are statistically characterized, catering for a global simulation process, where each iteration step is associated to an independent structural nonlinear static or dynamic analysis. Failure probability is then obtained through different uncertainty models, corresponding to the convolution of capacity and demand distributions or the probabilistic analysis of a safety indicator, defined as the difference between capacity and demand at each random simulation realisation. A case study of seven bridge configurations, with different (ir)regularity levels, is considered together with a relatively large set of real earthquake records. The simulation process is carried out using Latin Hypercube sampling, expected to considerably reduce the number of realizations with no reliability loss. Conclusions have allowed the identification of vulnerable configurations and shown the differences in considering different uncertainty models.

Derivation of fragility functions for seismic assessment of RC bridge portfolios using different intensity measures

ABSTRACT Macro-scale seismic assessment of road networks requires the characterization of the vulnerability of the population of existing bridges, typically provided by fragility curves as they correlate the probability of exceeding specific limit states at different levels of intensity measures (IM). The available literature mainly provides functions of peak ground or spectral accelerations, developed using single structures. However, when dealing with a population of reinforced concrete (RC) bridges, recent research has identified different IMs as more promising. This paper carries out a statistically sound comparison of improved analytical fragility curves by means of nonlinear static analysis of 3D RC bridge models.

An improved model for seismic risk assessment in Portugal

Purpose Portugal experienced very destructive earthquakes in the past, such as the well-known Lisbon Earthquake in 1755. With such in mind, accurate estimates of human and economic losses can play a significant role in providing various societal key players with objective information for response strategies. The present paper aims to present the contribution of the most recent study in Portugal (PRISE) concerning comprehensive seismic risk assessment, which can be used as good practice and reproduced in different contexts. Design/methodology/approach PRISE (Earthquake loss assessment of the Portuguese building stock) covered three main lines of research, corresponding to the three components typically considered in any seismic risk assessment study: i) the characterization of the seismic hazard; ii) the identification of the exposure to earthquakes and loss potential; and iii) the vulnerability of the exposed assets. Each of those components was fully characterized through the collection of census and l...

A facile method to prepare translucent anatase thin films in monolithic structures for gas stream purification

AbstractIn the present work, a facile method to prepare translucent anatase thin films on cellulose acetate monolithic (CAM) structures was developed. A simple sol–gel method was applied to synthesize photoactive TiO2 anatase nanoparticles using tetra-n-butyl titanium as precursor. The immobilization of the photocatalyst on CAM structures was performed by a simple dip-coating method. The translucent anatase thin films allow the UV light penetration through the CAM internal walls. The photocatalytic activity was tested on the degradation of n-decane (model volatile organic compound—VOC) in gas phase, using a tubular lab-scale (irradiated by simulated solar light) and pilot-scale (irradiated by natural solar light or UVA light) reactors packed with TiO2-CAM structures, both equipped with compound parabolic collectors (CPCs). The efficiency of the photocatalytic oxidation (PCO) process in the degradation of n-decane molecules was studied at different operating conditions at lab-scale, such as catalytic bed size (40–160xa0cm), TiO2 film thickness (0.435–0.869xa0μm), feed flow rate (75–300xa0cm3xa0min−1), n-decane feed concentration (44–194xa0ppm), humidity (3 and 40%), oxygen concentration (0 and 21%), and incident UV irradiance (18.9, 29.1, and 38.4xa0WUVxa0m−2). The decontamination of a bioaerosol stream was also evaluated by the PCO process, using Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Gram-positive) as model bacteria. A pilot-scale unit was operated day and night, using natural sunlight and artificial UV light, to show its performance in the mineralization of n-decane air streams under real outdoor conditions.n Graphical abstractNormally graphics abstract are not presented with captions/legend. The diagram is a collection of images that resume the work