RCAAP Repository

Abstract In this paper the simplified method to evaluate final efforts using γ z coefficient is studied considering the variation of the second order effects with the height of the buildings. With this purpose, several reinforced concrete buildings of medium height are analyzed in first and second order using ANSYS software. Initially, it was checked that the (z coefficient should be used as magnifier of first order moments to evaluate final second order moments. Therefore, the study is developed considering the relation (final second order moments/ first order moments), calculated for each story of the structures. This moments relation is called magnifier of first order moments, "γ", and, in the ideal situation, it must coincide with the γ z value. However, it is observed that the reason γ /γ z varies with the height of the buildings. Furthermore, using an statistical analysis, it was checked that γ /γ z relation is generally lower than 1.05 and varies significantly in accordance with the considered building and with the presence or not of symmetry in the structure.

Abstract The application of Nondestructive Testing methods (NDT) may be an interesting strategy to monitor the condition state of reinforced concrete structures, especially when there are problems related to mixing, conveying or placing the concrete. Among the NDT methods, the Ultrasonic Pulse Velocity (UPV) has been one of the most used in various fields of civil engineering, due to the ease of operation, low cost, test velocity and low level of damage to the surface analyzed. This work aims to study the influence of certain technological variables in the results obtained through UPV tests. With this aim two large blocks were cast at the laboratory, with dimensions close to real concrete elements. One of the elements was reinforcement with steel meshes on both sides while the other was cast without reinforcement. Inside these elements objects were introduced to reproduce internal concrete flaws. To facilitate the analysis the results were represented by means of a surface mapping image technique and were also subjected to statistical analysis. Through the study it was demonstrated that the correct choice of test parameters is crucial to obtain a right interpretation of UPV results from real structures.

Abstract In this work, a two-dimensional finite element (FE) model for physical and geometric nonlinear analysis of reinforced concrete beams and plane frames, developed by the authors, is presented. The FE model is based on the Euler-Bernoulli Beam Theory, in which shear deformations are neglected. The bar elements have three nodes with a total of seven degrees of freedom. Three Gauss-points are utilized for the element integration, with the element section discretized into layers at each Gauss point (Fiber Model). It is assumed that concrete and reinforcing bars are perfectly bonded, and each section layer is assumed to be under a uniaxial stress-state. Nonlinear constitutive laws are utilized for both concrete and reinforcing steel layers, and a refined tension-stiffening model, developed by the authors, is included. The Total Lagrangean Formulation is adopted for geometric nonlinear consideration and several methods can be utilized to achieve equilibrium convergence of the nonlinear equations. The developed model is implemented into a computer program named ANEST/CA, which is validated by comparison with some tests on RC beams and plane frames, showing an excellent correlation between numerical and experimental results.

Abstract In this work, a comparative study of different simplified methods and nonlinear finite element (FE) models used for calculating short-term deflections (vertical displacements of the longitudinal axis) in continuous reinforced concrete (RC) beams, under service loads, is performed. The simplified methods employed are the one proposed by Branson and the bilinear method recommended by the European Code CEB - Design Manual on Cracking and Deformations. Two finite element models are utilized: the first one with frame elements in which material nonlinearities are considered along the element and its cross section divided into layers, by using of constitutive relationships for steel and concrete, while the second one utilizes beam elements, with physical nonlinearity considered by means of moment-curvature diagrams, obtained from Branson equation. Several examples of continuous RC beams under service loads are analysed and the results obtained by the different models are compared taking as reference the nonlinear frame element model. A few conclusions and recommendations regarding the use of the different methods are drawn at the end of the work.

Abstract Obtaining internal load capacity, in reinforced concrete sections, at ambient temperature, under biaxial bending, is one of the most common tasks done by structural engineers, but not so common when the member is in fire situation. The intention of this paper is to show that is possible to correlate the ultimate limit state (ULS), in fire situation, with ULS at ambient temperature, for square cross sections under fire from all faces. To reach the purpose and give support to the numerical analysis of this article, a computer program, in Delphi language, called COL FIRE, is being developed by the authors.

Abstract This work developed experimental tests and numerical models able to represent the mechanical behavior of prisms made of ordinary and high strength concrete blocks. Experimental tests of prisms were performed and a detailed micro-modeling strategy was adopted for numerical analysis. In this modeling technique, each material (block and mortar) was represented by its own mechanical properties. The validation of numerical models was based on experimental results. It was found that the obtained numerical values of compressive strength and modulus of elasticity differ by 5% from the experimentally observed values. Moreover, mechanisms responsible for the rupture of the prisms were evaluated and compared to the behaviors observed in the tests and those described in the literature. Through experimental results it is possible to conclude that the numerical models have been able to represent both the mechanical properties and the mechanisms responsible for failure.

Abstract The design of a precast structural system requires joints between the structural elements, and concrete corbels are commonly used in the connection between beams and columns. Concrete corbels create an obstacle in the optimization of precast production, mainly of columns that have two or more concrete corbels in different faces. In these cases, the concrete corbels need to be manufactures in a different stage from the column, which requires attention to the interface between column and corbel, and some solution to ensure the continuity of the main tie reinforcement. For this paper, tests were conducted along with analytical and computational modeling of five concrete corbels models: one monolithic model and four where the corbels are manufactured in a different stage from the column. Results show the failure mode, the interface gap opening and the accuracy of the analytical and computational predictions. It was observed that the concrete corbels with bent main tie reinforcement displayed the largest gap-opening at the interface and that the computational modeling represented the strength of the monolithic concrete corbel better than the design code models.

ABSTRACT This work analyses the methodology "A" (item A.4) employed by the Brazilian Standard ABNT 8522 (ABNT, 2008) for determining the stress-strain behavior of cylindrical specimens of concrete, presenting considerations about possible enhancements aiming it use for concretes with recycled aggregates with automatic test equipment. The methodology specified by the Brazilian Standard presents methodological issues that brings distortions in obtaining the stress-strain curve, as the use of a very limited number of sampling points and by inducing micro cracks and fluency in the elastic behavior of the material due to the use of steady stress levels in the test. The use of a base stress of 0.5 MPa is too low for modern high load test machines designed do high strength concrete test. The work presents a discussion over these subjects, and a proposal of a modified test procedure to avoid such situations.

ABSTRACT This study was conducted with the aim of evaluating the influence of different methods for end surface preparation of compressive strength test specimens. Four different methods were compared: a mechanical wear method through grinding using a diamond wheel established by NBR 5738; a mechanical wear method using a diamond saw which is established by NM 77; an unbonded system using neoprene pads in metal retainer rings established by C1231 and a bonded capping method with sulfur mortar established by NBR 5738 and by NM 77. To develop this research, 4 concrete mixes were determined with different strength levels, 2 of group 1 and 2 of group 2 strength levels established by NBR 8953. Group 1 consists of classes C20 to C50, 5 in 5MPa, also known as normal strength concrete. Group 2 is comprised of class C55, C60 to C100, 10 in 10 MPa, also known as high strength concrete. Compression tests were carried out at 7 and 28 days for the 4 surface preparation methods. The results of this study indicate that the method established by NBR 5738 is the most effective among the 4 strengths considered, once it presents lower dispersion of values obtained from the tests, measured by the coefficient of variation and, in almost all cases, it demonstrates the highest mean of rupture test. The method described by NBR 5738 achieved the expected strength level in all tests.

ABSTRACT This work includes an analytical and experimental study of the structural behavior of shear connectors in composite columns, composed of concrete-filled circular hollow section. For this study was adopted a structural bolt like a shear connector in order to verify the validity of the analytical expressions in ABNT NBR 16239: 2014 [1]. Was carried out a series of push-out tests, fixing the outer diameter of the hollow section and varying the thickness, the bolt diameter, the strength of concrete and the hole dimension. Analysis of the results shows that is possible to use this type of shear connector. The Brazilian prescriptions results are conservative and may be adjusted to provide strength capacity value closest to the experiment.

ABSTRACT This work presents a study on the project actions required for the design and analysis of port structures, with regard to the impacts of mooring and berthing of vessels. This study sought to conduct a literature review, with emphasis on technical standards and codes, encompassing both national and international publications, including the Brazilian Standard NBR 9782/1987, the British Standard BS 6349, and the German Standard EAU 2004, in addition to the recommendations of the Permanent International Association of Navigation Congresses (PIANC 2002), and those of Jayme Mason (1982) in “Port Works”. The design procedures proposed by these different references regarding the computation of forces induced by mooring and berthing of vessels were evaluated in this work. Additionally, a case study of a port’s substructure was carried out, and a comparative analysis of the results, obtained with each recommendation of the aforementioned publications, was performed. The results showed a remarkable dispersion, revealing that the standards used strongly influence the design loads of port structures.

ABSTRACT The carbonation process is one of the factors that cause a reduction in the hydrogenionic potential (pH) in cementitious composites, which can lead to a depassivation of the reinforcement structures, thus furnishing conditions for a corrosion process to begin. In this paper, the research sought to monitor the progress of the carbonation front according to European standard EN 14630, concurrently with the measurement of pH variation on the cementitious composite surface. Cylindrical mortar specimens with size of (2 x 4) cm were placed in a carbonation chamber with controlled conditions, keeping up the humidity at 65%, temperature at 28 °C and the CO2 concentration of 5%. The void structure of the matrix was evaluated by X-ray microtomography technique (μ-CT). The pH reading enabled the monitoring of the carbonation front progress in function of loss of alkalinity, even before the procedure laid down in standard EN 14630. The images obtained through µ-CT did not enable the visualization of the densification of the material found in the outermost layer of the specimen.

ABSTRACT The threats of bomb attacks by criminal organizations and accidental events involving chemical explosives are a danger to the people and buildings. Due the severity of these issues and the need of data required for a safety design, more research is required about explosions and shock waves. This paper presents an assessment of blast wave overpressures using a computational fluid dynamics software. Analyses of phenomena as reflection of shock waves and channeling effects were done and a comparison between numerical results and analytical predictions has been executed, based on the simulation on several models. The results suggest that the common analytical predictions aren’t accurate enough for an overpressure analysis in small stand-off distances and that poorly designed buildings may increase the shock wave overpressures due multiple blast wave reflections, increasing the destructive potential of the explosions.

ABSTRACT In many situations, the Brazilian Legislation does not require verifying roof structures in a fire, since their failure will not endanger the stability of the structure. In fire, the steel roof of an industrial building deforms by heating in geometry similar to a catenary, resulting in horizontal forces in the upper extremities of the columns. Thus, even roofs that do not constitute a frame with the columns may lead them to collapse, and should therefore be protected against fire. Due to the small dimensions of the structural elements of the roof, fire coating is uneconomical. There is thus a problem in the design practice. A procedure based on the British literature in which horizontal load is considered in the columns is presented in this paper. Columns and foundations must support that load. That load should be determined and the columns should be checked for fire situation. The aim of this paper is to detail this procedure, adapt it to Brazilian standards and apply it to a case study.

ABSTRACT A simplified methodology is proposed for the dynamic analysis of curved road bridges under the effect of a 3C class heavy vehicle. The dynamic models of both vehicle and bridge are considered to be uncoupled, being bound by the interaction forces. These forces come from the vehicle dynamic analysis, initially under rigid deck, subjected to a support excitation caused by the pavement geometric irregularities. Such forces are statically condensed in the vehicle centre of mass and applied to a simplified structural model (‘unifilar’) of a curved bridge with box girder section, considering the bridge super elevation. The influence of the rigid deck hypothesis on the dynamic response is assessed by an iterative procedure, in which the deck displacements are added to the pavement irregularities, to obtain an “equivalent irregularity” function. The new interaction forces are re-applied to the bridge model to determine new displacements, repeating the procedure until the results converge.

DEET (N,N-diethyl-3-methylbenzamide) is nowadays the most effective mosquito repellent available, however, its use can present some topical and systemic side effects. Some botanical compositions, as Andiroba (Carapa guianensis), have been proved repellent properties at low cost and toxicity. An experimental study was driven involving four volunteers submitting their forearms covered with Andiroba oil at 100%, DEET 50%, refined soy oil, Andiroba oil 15% and in the absence of products, directly to healthy females of Aedes sp. The times of first and third bites were checked. The results showed that the median of the first bite without any product was 17.5s and the third bite, 40.0s. In the soy oil, the bites happened in 60.0s and 101.5s, in the presence of Andiroba oil 100%, in 56.0s and 142.5s and in Andiroba oil 15%, in 63.0s and 97.5s. The volunteers using DEET 50% had not received bites after 3600s in most of the experiments (p < 0.001 Wilcoxon). Pure Andiroba oil compared to the soy oil, forearm without product and Andiroba oil 15%, showed discreet superiority (p < 0.001 Wilcoxon). Our conclusion is that this study demonstrated that the pure Andiroba oil presents discreet repellent effect against bite of Aedes sp., being significantly inferior to DEET 50%.

Comparative morphometric and morphological studies of eggs under scanning electron microscope (SEM) were undertaken in the three strains of two karyotypic forms of Anopheles aconitus, i.e., Form B (Chiang Mai and Phet Buri strains) and Form C (Chiang Mai and Mae Hong Son strains). Morphometric examination revealed the intraspecific variation with respect to the float width [36.77 ± 2.30 µm (Form C: Chiang Mai strain) = 38.49 ± 2.78 µm (Form B: Chiang Mai strain) = 39.06 ± 2.37 µm (Form B: Phet Buri strain) >; 32.40 ± 3.52 µm (Form C: Mae Hong Son strain)] and number of posterior tubercles on deck [2.40 ± 0.52 (Form B: Phet Buri strain) = 2.70 ± 0.82 (Form B: Chiang Mai strain) < 3.10 ± 0.32 (Form C: Chiang Mai strain) = 3.20 ± 0.42 (Form C: Mae Hong Son strain)], whereas the surface topography of eggs among the three strains of two karyotypic forms were morphologically similar.

The ultrastructural superficial changes in third instar house fly (Musca domestica) and blow fly (Chrysomya megacephala) induced by eucalyptol oil were observed using scanning electron microscopy. Dipped in 0.902 g/ml eucalyptol for 30 sec, the larvae integument of both species showed significant aberrant appearance of the body surface, particularly swelling integument, bleb formation, partial breach and deformation of spines.

The colony of urban stray cats living in the Rio de Janeiro zoological garden was studied in order to develop a population and health control program. As many cats as possible were captured during two months (47 animals) and were classified according to gender, age, weight and coat markings. They were submitted to a general health evaluation, examined for the presence of ectoparasites and sent to a surgical neutering program. All animals had a blood sample drawn for CBC, platelet count, heartworm and retroviruses detection. Capillary blood smears were made for hemoparasites detection. Coat marking and colors were tabby (59.7%), followed by solid black (17%); torbie (10.6%); bicolor (10.6%) and harlequin (2.1%). The only ectoparasites found were fleas, which infested 28% of the animals. The hemoparasites found were Haemobartonella felis (38%) and piroplasmas that could not be differentiated between Cytauxzoon spp. and Babesia spp. (47%). No cat was found infected by Dirofilaria immitis or FeLV (Feline Leukemia Virus), although FIV (Feline Immunodeficiency Virus) antibodies could be detected (21%). There was no correlation between hemoparasites and FIV infections. The estimated total cat population (mark-recapture method) was 59; 68% female and 32% male, suggesting that a neutering program is in fact needed.

We have searched for Mycobacterium leprae DNA for 36kDa protein in urine using a M. leprae specific PCR technique. A limited number of 16 patients (of which 11 belonged to lepromatous leprosy and five to tuberculoid leprosy) and eight healthy individuals were included for the present study. The number of urine samples positive by PCR were 36.4% (4/11) in lepromatous patients and 40% (2/5) in tuberculoid patients. None of the samples from healthy individuals was positive. To our knowledge, the results indicate, for the first time, the presence of M. leprae DNA in urine from leprosy patients. Another important finding obtained out of the study is that amongst treated patients 66.6% (4/6) were positive whereas amongst untreated only 20% (2/10) were positive. From the present indicative data it appears that treatment improves the PCR results with urine as a sample. Thus, the approach could prove to be useful for monitoring the treatment response of individual patients and needs to be further evaluated with a large number of patients.