Navegando por Assunto "Engenharia de estruturas"

Agora exibindo 1 - 8 de 8

Acesso aberto (Open Access)
Adequação estrutural dos pilares de um edifício residencial em concreto armado na cidade de Rio Branco
(Universidade Federal do Pará, 2013-11-06) SANTOS, Mateus Silva dos; OLIVEIRA, Dênio Ramam Carvalho de; http://lattes.cnpq.br/1324105476558186
The recovery and strengthening of reinforced concrete structures are increasingly common in Brazil, mainly due to the aging of structures built in the 60s and 70s of the twentieth century, which are close to reaching their lifetime. Added to this, factors such as the use of concrete with low strength, execution failures, improper use and lack of maintenance. Due to these factors that society should endeavor to enhance and / or restore these buildings, thus avoiding demolition of the same and even avoid fatal acidentes. This paper presents a case study that aims to recover a building that is abandoned for nearly two decades in the city of Rio Branco, Acre State. Currently, there are various techniques for strengthening reinforced concrete structure. Such as reinforcement through reinforced concrete jacketing, supplemented or enhanced with added armor, enhanced with application of metal sheets and profiles, reinforcing pillars reinforced with carbon fiber (PRCF), among other. In this work, the method adopted for recovery was enhanced by reinforced concrete jacketing. And for a better understanding of the methodology adopted work also presents details of the enhanced configuration adopted, constructive detail and executive procedures of the method adopted. In addition, the wrappers showing the active and resistant efforts before and after the booster.
Acesso aberto (Open Access)
Análise experimental de lajes nervuradas de concreto armado com viga faixa de altura variável
(Universidade Federal do Pará, 2014-11-21) SACRAMENTO, Paulo Victor Prazeres; OLIVEIRA, Dênio Ramam Carvalho de; http://lattes.cnpq.br/1324105476558186
The ribbed slabs have been widely used in the buildings it has several advantages in its execution and performance. In order to get a good design of this type of slab is necessary ensure that the stresses are properly supported, mainly those considered critical, which can lead the structure to the collapse suddenly, as is the case of punching in connection wide beam-column or of the shear in the region of the ribbed. In order to evaluate the punching strength of the slab-column connection and the shear strength of the ribs were manufactured four reinforced concrete ribbed slabs, two slabs one-way and two slabs two-way. The flexural reinforcement rate was constant in all slabs. All slabs were square of side 2200 mm and thickness equal to 150 mm. The main variable in this study was the change in height of the wide beam. This variation has to evaluate the performance of the ribs, even when the limit of spacing between them is ensured. Also, check if the punching is a possibility of rupture in this case. The estimates in this step design were based on three different standards. These were ACI 318 (2008), Eurocode 2 (2004) and NBR 6118 (ABNT, 2014). Studies with ribbed slabs have shown that the estimates of design standards are conservative. In addition, this predictions may lead to inadequate results for resistance slabs. The experimental results of this series of tests were compared to the standard recommendations in order to assess the accuracy of these three standards, which refer to the ribbed slabs. Were also built computational models in order to verify that the behavior of slabs as the stress distribution both in connection wide beam-column range as the beam connection wide beam-ribbed. The results showed that the slabs connection wide beam-ribs must be treated in a careful manner due to the difference in stiffness between the solid area and the ribs.
Acesso aberto (Open Access)
Análise experimental dos limites superiores de resistência à punção de lajes lisas de concreto armado com armaduras de cisalhamento
(Universidade Federal do Pará, 2018-10-30) FREITAS, Marcus Vinícius Pereira de; FERREIRA, Maurício de Pina; http://lattes.cnpq.br/4242041552985485; https://orcid.org/0000-0001-8905-9479
In the flat slab system, the slab-column connection is a critical point due to the risk of punching shear failure. Several structural collapses are reported due to this mode of failure and constructive errors are the main causes of such accidents, leading researchers to study new shear reinforcement to minimize them. The use of shear reinforcement is the most efficient way to increase punching shear ductility and strength, but its correct arrangement generates conflict with the flexural reinforcement. Thus, Ferreira et al. (2016) propose a prefabricated truss reinforcement positioned internally to the flexural reinforcement, which generated the patent number BR 10 2015 006518 3 A2. Therefore, the work carried out in this research contributes to the investigation of cases of bidirectional shear for the present reinforcement. In this research, 5 experimental tests of reinforced concrete flat slabs submitted to symmetrical loading, containing both Stud Rails and the pre-fabricated truss reinforcement proposed by Ferreira et al. (2016) as shear reinforcement, were carried out. The study evaluated the performance of the reinforcement in relation to punching shear strength and analyzed the upper limits of strength, since a flexural reinforcement ratio of 2% and shear reinforcement ratios around 1% were used. The slabs were octagonal with a 2500 mm distance between parallel faces, side of 1036 mm and thickness of 210 mm, cast with concrete around 30 MPa and supported on columns with 400-mm-side. The following variables were analyzed: shear reinforcement type, slope and spacing of the shear reinforcement layers, as well as the design parameters of ACI 318 (2014), EC2 (2014), ABNT NBR 6118 (2014) and ETA 12/0454 (2012) codes. The experimental results show that the increase of load, in relation to the slab without shear reinforcement, reached up to 92%, with the use of pre-fabricated truss reinforcement, and 101% with the use of Studs, showing that the upper limit of ultimate load as a function of the concrete strength (Vu/Vc) can be limited to 2 and that the reinforcement studied in this research has a high commercial potential, since its cost per increment of load was lower than the one of the slab reinforced with Studs Rails, except for the design criteria suggested by ETA 12/0454, reducing the total cost by 15.6%.
Acesso aberto (Open Access)
Desempenho estrutural de blocos, primas, mini-paredes e paredes de alvenaria estrutural confeccionadas com blocos cerâmicos produzidos a partir da mistura de lama vermelha com argila
(Universidade Federal do Pará, 2014-03-27) COSTA, Diogo Henrique Pereira e; MACEDO, Alcebíades Negrão; http://lattes.cnpq.br/8313864897400179
New techniques for the improvement of residues have become increasingly important in constructions, especially when it comes to the use of residue from other industries and the reduction of natural raw materials. The objective of this study was to evaluate the use of a residue from the production of metallurgical alumina known as red mud (RM), the structural performance of blocks, prisms, mini-walls and walls made of ceramic blocks with reticulated and circular cross sections, produced from the mixture of clay and RM. Experimental tests were performed corresponding to the characterization of the materials used and testing of compressive strength of units, blocks, prisms, mini-walls and walls. All materials and units met the standard requirements for their correct use in experimental tests. The results of compression tests have shown that elements of the blocks made by mixing clay and RM parameters met the standards and showed satisfactory and superior results to the components made of composite ceramic blocks with 100% clay, usually employed in constructions.
Acesso aberto (Open Access)
Influência da protensão na resistência ao cisalhamento de vigas de concreto protendido
(Universidade Federal do Pará, 2014-11-21) SOUZA JUNIOR, Orivaldo de Azevedo; OLIVEIRA, Dênio Ramam Carvalho de; http://lattes.cnpq.br/1324105476558186
With the increase of the construction industry, the prestressed concrete has advanced beyond of the stages of evolution, being consolidated as a structural material, evolving and bringing reliable technical and technologies for many different structures, ranging from conventional buildings, with applications in bridges and stadiums, and on to more complex structures such as offshore platforms. The study of shear in reinforced concrete beams and prestressed concrete beams always had many controversies because of the many variables that involve the study of shear. In the case of prestressed beams, which are adopted profiles with different inclinations together with shear reinforcement, there is need for improved theoretical methods and practical, this research may contribute materially to the understanding of these variables. Thus, to determine the influence of the inclination of prestressing strands in the shear strength of prestressed concrete beams, oriented the focus this research to study of six prestressed concrete beams with alternating tracing cable straight and parabolic and transverse reinforcement, in order to observe the structural behavior of these beams, mainly observations about the influence of the stress generated by varying the inclination of the cables and varying the rate of transverse mode rupture, the load capacity, the surfaces of rupture and other factors in order to understand the shear in prestressed concrete beams.
Acesso aberto (Open Access)
Machine learning algorithms for damage detection in structures under changing normal conditions
(Universidade Federal do Pará, 2017-01-31) SILVA, Moisés Felipe Mello da; SALES JÚNIOR, Claudomiro de Souza de; http://lattes.cnpq.br/4742268936279649; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
Engineering structures have played an important role into societies across the years. A suitable management of such structures requires automated structural health monitoring (SHM) approaches to derive the actual condition of the system. Unfortunately, normal variations in structure dynamics, caused by operational and environmental conditions, can mask the existence of damage. In SHM, data normalization is referred as the process of filtering normal effects to provide a proper evaluation of structural health condition. In this context, the approaches based on principal component analysis and clustering have been successfully employed to model the normal condition, even when severe effects of varying factors impose difficulties to the damage detection. However, these traditional approaches imposes serious limitations to deployment in real-world monitoring campaigns, mainly due to the constraints related to data distribution and model parameters, as well as data normalization problems. This work aims to apply deep neural networks and propose a novel agglomerative cluster-based approach for data normalization and damage detection in an effort to overcome the limitations imposed by traditional methods. Regarding deep networks, the employment of new training algorithms provide models with high generalization capabilities, able to learn, at same time, linear and nonlinear influences. On the other hand, the novel cluster-based approach does not require any input parameter, as well as none data distribution assumptions are made, allowing its enforcement on a wide range of applications. The superiority of the proposed approaches over state-of-the-art ones is attested on standard data sets from monitoring systems installed on two bridges: the Z-24 Bridge and the Tamar Bridge. Both techniques revealed to have better data normalization and classification performance than the alternative ones in terms of false-positive and false-negative indications of damage, suggesting their applicability for real-world structural health monitoring scenarios.
Acesso aberto (Open Access)
Patologias em fachadas: análises de casos na Universidade Federal do Pará
(Universidade Federal do Pará, 2014-03-28) CARVALHO, Isabella Chaves; PICANÇO, Marcelo de Souza; http://lattes.cnpq.br/4535052395600357; MACEDO, Alcebíades Negrão; http://lattes.cnpq.br/8313864897400179
The system of external cladding of the building acts as a protective layer and contributes to the proper aspect. The facade is subject to the action of agents of degradation as one of the most exposed areas of the building, with the presence of pathology becoming responsible for high repair costs. Research suggests as a general goal, assess conditions affecting building facades of higher education in the Federal University of Pará, guided by a theoretical basis (literature review) responsible for the first information on the subject. To such as research methodology, we sought to first do a physical survey of facades of 30 buildings in UFPA, identifying cadastral records in the main degradation mechanisms. Then, after quantify / qualify the anomalies present in the sample and point out the most critical building with key injuries and their causes, listed up to this, basic intervention measures in order to solve efficiently the problem caused by proposing a document that acts as technical support for inspection of facades generally. We also used the test to characterize samples in order to prove the origins of those damages which at first could not identify the cause. The results showed that the analyzed buildings have pathological damage of different nature and degree of complexity, ranging from the most complex requiring specific tests to discover their origin, even the most simple, with scheduled maintenance can be eliminated. We conclude that much of the damage happen by human negligence, but that even with an emphasis on quality of execution in facades, there is no way rule out failures or ignore the time of use and the actions of external factors lead to degradation Nature of the building. We conclude that much of the damage happen by human negligence, but that even with an emphasis on quality of execution in facades, there is no way to reject the hypothesis failures or ignore the time of use and the actions of external factors lead to natural degradation of the building. Therefore, to prevent the early onset of pathologies in facades, bringing its useful life and reducing extra costs, it is suggested, implementation procedures based on technical standards enforcement of them, following project criteria and presenting periodic inspections so that preventive measures are taken in apt time.
Acesso aberto (Open Access)
Pesagem em movimento e caracterização do tráfego ferroviário com uso da técnica B-WIM
(Universidade Federal do Pará, 2014-02-26) CARVALHO NETO, José Alves de; VELOSO, Luís Augusto Conte Mendes; http://lattes.cnpq.br/9476653308517248
This Master’s Thesis presents the development of algorithms for application of Bridge- Weigh In Motion (B-WIM) for weighing moving trains and method for the characterization of rail traffic, allowing up to obtain information about the speed of passage of trains , number and axle spacing. The B-WIM systems from a simple instrumentation for determining the axle loads of moving vehicles, eliminating the dynamic effect. The algorithms for determining the values related the geometry of the train and axle loads were implemented, which was validated from a theoretical example, where we simulated the passage of a train of known characteristics over the bridge and axle loads were determined 100% accuracy. In addition, a numerical example was done in finite element method, of a reinforced concrete viaduct for application of the method, where was determine axle loads for different speeds of train passage. In order to reduce the processing time of the analysis in the numerical example, an algorithm for generating the numerical model nodal loads was implemented that have reduced processing time by 96% compared to the analysis of multi-step, which automatically simulates the passage of the train over the structure. Finally, the method was tested on a real case from monitoring tests realized on a reinforced concrete viaduct in the Carajás Railroad. Although it was not possible to determine the axle load locomotive, it was possible to measure accurately the gross weight of the locomotive when using the constitutive model of Collins and Mitchell (1991) for concrete.