scholarly journals Análise de uma Estrutura de Concreto Armado e proposição de reforço para correção de falhas estruturais: Estudo de Caso

2018 ◽  
Vol 1 (43) ◽  
pp. 140
Author(s):  
Gláucia Nolasco de Almeida Mello ◽  
Bárbara Elisa Ferreira ◽  
Marina R. B. Macedo ◽  
Carolina S. Oliveira ◽  
Marina X. S. Assis ◽  
...  
Keyword(s):  
Natural Frequencies ◽  
Steel Beams ◽  
Steel Beam ◽  
Reinforced Concrete Structures ◽  
Vibration Modes ◽  
Structural Elements ◽  
Static And Dynamic Analysis ◽  
Critical Range ◽  
Useful Life ◽  
Recurrent Process

The reinforced concrete structures degradation even before reaching useful life, is a very recurrent process in buildings, and it is necessary to execute corrective techniques to strengthen the structural elements. Therefore, it is noted that research in this field is very important to civil engineering. Consequently, the present study consisted in performing a static and dynamic analysis of a school building that presented structural flaws to identify the causes of it and propose a rehabilitation solution. Through the static analysis of the structure, performed with the CAD/TQS program, it was verified that the slabs and beams of the building were mostly executed with a thickness lower than ideal and that, in some slabs, the deflection obtained were higher than allowable. Through modal analysis, performed with Altair HyperWorks program, it was verified that the fourth, fifth and sixth vibration modes of the structure did not meet the ELS-VE, since they present natural frequencies between the critical range indicated by NBR 6118 (ABNT, 2014), thus showing the occurrence of excessive vibration. As a result, a rehabilitation solution was proposed, using steel beams, which were calculated according to the methodology of NBR 8800 (ABNT, 2008) and, verified with the aid of Altair HyperWorks program. This methodology for strengthening the concrete structure was verified with the aid of the platform Altair HyperWorks, where it was concluded that the steel beam used are able to solve the problem with the excessive deflection in the slabs without harming the displacements of the beans who support them, maintaining unaltered the natural frequencies.

Vibration-Based Crack Detection in L-Frames

2014 ◽  
Vol 658 ◽  
pp. 261-268
Author(s):  
Jean Louis Ntakpe ◽  
Gilbert Rainer Gillich ◽  
Florian Muntean ◽  
Zeno Iosif Praisach ◽  
Peter Lorenz
Keyword(s):  
Strain Energy ◽  
Crack Detection ◽  
Natural Frequencies ◽  
Vibration Modes ◽  
Structural Elements ◽  
Element Analysis ◽  
Accurate Localization ◽  
Mathematical Expressions ◽  
Measurement Results ◽  
Non Destructive

This paper presents a novel non-destructive method to locate and size damages in frame structures, performed by examining and interpreting changes in measured vibration response. The method bases on a relation, prior contrived by the authors, between the strain energy distribution in the structure for the transversal vibration modes and the modal changes (in terms of natural frequencies) due to damage. Using this relation a damage location indicator DLI was derived, which permits to locate cracks in spatial structures. In this paper an L-frame is considered for proving the applicability of this method. First the mathematical expressions for the modes shapes and their derivatives were determined and simulation result compared with that obtained by finite element analysis. Afterwards patterns characterizing damage locations were derived and compared with measurement results on the real structure; the DLI permitted accurate localization of any crack placed in the two structural elements.

scholarly journals Comparação entre a eficiência estrutural de perfis soldados de aço e perfis de aço formados a frio

2016 ◽  
Vol 12 (3) ◽  
Author(s):  
Uiatan Aguiar Nogueira ◽  
Matilde Batista Melo ◽  
Daniel De Lima Araujo
Keyword(s):  
Bending Strength ◽  
Steel Beams ◽  
Steel Beam ◽  
Structural Elements ◽  
Structural System ◽  
Welded Steel ◽  
Bending Tests ◽  
Structural Efficiency ◽  
Cold Formed Steel

RESUMO: A Análise de elementos estruturais, realizadas durante as etapas de projeto de uma estrutura, é parte fundamental para garantia de bom desempenho e estabilidade do sistema estrutural. Na execução de algumas estruturas, como as coberturas em edificações, é usual o emprego de perfis leves de aço formados a frio devido ao seu baixo peso. Esta pesquisa tem por objetivo avaliar a eficiência estrutural desses perfis quando comparados, por exemplo, aos perfis soldados compactos. Para tanto, foram realizados ensaios de flexão em quatro vigas biapoiadas submetidas a duas forças concentradas, de forma a se obter flexão pura no meio do vão das vigas. Estas foram instrumentadas para a determinação da sua rigidez e da sua resistência à flexão. A principal contribuição deste trabalho é demonstrar a eficiência estrutural de perfis formados a frio em seção caixa submetidos à flexão em comparação com perfis de seção tipo “H” soldados. ABSTRACT: The analysis of structural elements, in a structure’s design, is an essential step to ensure good performance and stability of the structural system. In any types of structures, such as roofing in buildings, it’s usual using cold-formed steel beams due to their small weight. This research seeks to evaluate the structural efficiency of cold-formed steel beams when compared, for example, to compact welded steel beams. Thus, bending tests were performed in four simply supported beams submitted to two concentrated loads, in order to obtain pure flexure at the mid-span of the beams. These beams were instrumented for the determination of their rigidity and bending strength. The results showed that the cold-formed steel beam, box-shaped, presented structural efficiency similar to the welded steel beam “H” shaped.

scholarly journals Investigation and numerical analysis of steel beams strengthened with CFRP

2021 ◽  
Vol 37 (3) ◽  
Author(s):  
M. Khanloo ◽  
H. Dashti-Naserabadi ◽  
M. Jamshidi
Keyword(s):  
Concrete Structures ◽  
Steel Structures ◽  
High Strength ◽  
Steel Beams ◽  
Steel Beam ◽  
Reinforced Concrete Structures ◽  
Ansys Software ◽  
Variable Parameters ◽  
Design Engineers ◽  
Composite Layers

One of the most common methods of strengthening concrete structures is the use of composite fibers such as FRP. These fibers have found a special place in structural retrofitting methods due to a number of specific ability including lightness and ease of performance. Reinforced concrete structures have long been considered by design engineers for the possibility of retrofitting high strength composite steel structures. In this study, twenty-two steel beam models were modeled by ANSYS software. Variable parameters studied in the modeled steel beams can be referred to the number, orientation and thickness of composite layers.

scholarly journals Effect of Prestress Force on Natural Bending Frequency of External Prestressed Steel Beams

2018 ◽  
Vol 12 (1) ◽  
pp. 62-70 ◽  
Author(s):  
Tang Bai-jian ◽  
Wang Fei ◽  
Chen Song
Keyword(s):  
Natural Frequencies ◽  
Cross Sectional Area ◽  
Steel Beams ◽  
Steel Beam ◽  
Sectional Area ◽  
View Point ◽  
The Finite Element Method ◽  
Cross Sectional ◽  
Simply Supported ◽  
Odd Order

Introduction: Natural bending frequencies of externally prestressed steel beam have certain sensitivity to prestress force, so they can be used to find the magnitude of prestress force. Methods: To answer the question if the existence of externally prestressed tendons increases or decreases the natural bending frequencies of a simply supported steel beam, the calculating formula for natural frequencies is deduced by using the energy method from the view point of prestress mechanism and further verified by the finite element method. Using this formula of universal property, the influence of prestress force, eccentricity and cross-sectional area of tendons on natural bending frequencies of prestressed steel beam is clearly revealed. Results and Conclusion: For external prestressed steel beams with straight tendons, their natural frequencies increase with the eccentricity and cross-sectional area of the prestressed tendon, and the eccentricity has a much larger effect on natural frequencies than the cross-sectional area does. The prestress force has no influence on the oven-order frequencies but decreases the odd-order frequencies. With the increasing order number, the prestress effect is much weaker than the effects caused by the eccentricity and cross-sectional area of the tendon.

scholarly journals ANALISIS PENGARUH JENIS DAN TEBAL SPRAY APPLIED MATERIALS FIREPROOFING TERHADAP KETAHANAN API BALOK BAJA

2017 ◽  
Vol 14 (1) ◽  
pp. 1
Author(s):  
NKA Agustini ◽  
Andreas Triwiyono
Keyword(s):  
Yield Stress ◽  
Numerical Approach ◽  
Nonlinear Material ◽  
Constant Thickness ◽  
Thickness Variation ◽  
Steel Beams ◽  
Steel Beam ◽  
Structural Elements ◽  
Eurocode 3 ◽  
Thick Steel

Protection against fire is important to maintain the strength of the structure. Fireproofing can be used as an anticipation to reduce the spread of the fire. Evaluation the effect of fire on structural elements is generally performed by a numerical approach. Analysis of simple beam IWF 150x75x5x7 with 3,5 span length using varied fireproofing such as CAFCO 300, Carboline Type 5 MD and Typo WR-AFD was conducted with Abaqus CAE 6.11-1. Nonlinear material properties of steel based on Eurocode 3 while thermal properties of fireproofing are constant. Thickness variation of fireproofing are 10 and 20 mm. Pressure load was carried on the top flange of steel beam. ASTM E-119 used as a thermal load by conduction on 3 sides (left, right and bottom) with duration of 2 hours.  The results showed that type and thickness variation of the fireproofing has a significant effect on the fire resistance of steel beams. The highest temperatures occur when steel coated by Typo WR-AFP and the lower temperatures occur when steel coated by CAFCO 300. Maximum deflection of steel beam occurred when steel coated by Typo WR-AFD. Steel beam with Typo WR-AFD experiencing a critical deflection with the fastest time of 4.80 minutes at 10 mm thick and 9.10 min at 20 mm thick. Steel beam with 10 mm thick of fireproofing achieve yield stress when the time 14.03, 8.86 and 5, 12 minutes for fireproofing CAFCO 300, Carboline Type 5 MD and Typo-AFD WR. Steel beam with 20 mm thick of fireproofing  experiencing yield stress only on Typo WR-AFD at 10.22 minutes.  Abstrak : Perlindungan terhadap api (kebakaran) merupakan hal penting untuk mempertahankan kekuatan struktur sehingga masih dapat menahan beban rencana. Lapisan fireproofing pabrikasi dapat digunakan sebagai antisipasi untuk mengurangi rambatan panas akibat kebakaran. Evaluasi pengaruh kebakaran pada elemen struktur umumnya dilakukan dengan pendekatan numerik. Analisis pengaruh ketebalan dan sifat termal fireproofing jenis spray applied materials bervariasi yaitu CAFCO 300, Carboline Type 5MD dan Typo WR-AFD terhadap ketahanan api balok sederhana IWF 150x75x5x7 menggunakan Abaqus CAE 6.11. Material baja bersifat non linier sesuai Eurocode 3 sedangkan sifat termal fireproofing bersifat konstan. Variasi ketebalan lapisan digunakan 10 dan 20 mm. Beban tekan (pressure loads) dikerjakan di sayap atas balok. Beban termal menggunakan standar api ASTM E-119 secara konduksi di 3 sisi (samping kiri, kanan dan bawah) dengan durasi 2 jam. Hasil penelitian menunjukkan variasi jenis dan ketebalan fireproofing memberikan pengaruh signifikan terhadap ketahanan api balok baja. Suhu baja tertinggi terjadi saat baja dilapisi fireproofing jenis TYPO WR-AFP dan terendah saat dilapisi fireproofing CAFCO 300. Baja dengan lapisan fireproofing TYPO menghasilkan lendutan paling besar dibanding baja dengan lapisan fireproofing lainnya Baja dengan lapisan fireproofing Typo WR-AFD mengalami lendutan kritis dengan waktu tercepat yakni 4,80 menit saat tebal 10 mm dan 9,10 menit tebal 20 mm Baja dengan lapisan fireproofing 10 mm mencapai tegangan leleh saat waktu 14,03 , 8,86 dan 5, 12 menit untuk fireproofing CAFCO 300, Carboline Type 5 MD dan Typo WR-AFD. Baja dengan tebal fireproofing 20 mm mengalami tegangan leleh hanya pada jenis Typo WR-AFD saat 10,22 menitKata kunci :jenis fireproofing,  tebal fireproofing, temperatur, lendutan, tegangan.

Measurement of Young’s Modulus and Shear Modulus of Some Structures Welded Using Flux Cored Wire by Vibration Tests

2014 ◽  
Vol 216 ◽  
pp. 151-156 ◽  
Author(s):  
Liviu Bereteu ◽  
Mircea Vodǎ ◽  
Gheorghe Drăgănescu
Keyword(s):  
Shear Modulus ◽  
Arc Welding ◽  
Natural Frequencies ◽  
Free Vibrations ◽  
Vibration Modes ◽  
Cored Wire ◽  
Flux Cored Arc Welding ◽  
Longitudinal Elastic Modulus ◽  
Vibration Tests ◽  
Non Destructive

The aim of this work was to determine by vibration tests the longitudinal elastic modulus and shear modulus of welded joints by flux cored arc welding. These two material properties are characteristic elastic constants of tensile stress respectively torsion stress and can be determined by several non-destructive methods. One of the latest non-destructive experimental techniques in this field is based on the analysis of the vibratory signal response from the welded sample. An algorithm based on Pronys series method is used for processing the acquired signal due to sample response of free vibrations. By the means of Finite Element Method (FEM), the natural frequencies and modes shapes of the same specimen of carbon steel were determined. These results help to interpret experimental measurements and the vibration modes identification, and Youngs modulus and shear modulus determination.

scholarly journals Vibration of Rotating and Revolving Planet Rings with Discrete and Partially Distributed Stiffnesses

2020 ◽  
Vol 11 (1) ◽  
pp. 127
Author(s):  
Fuchun Yang ◽  
Dianrui Wang
Keyword(s):  
High Speed ◽  
Differential Operators ◽  
Natural Frequencies ◽  
Rotation Speed ◽  
Distribution Area ◽  
Vibration Modes ◽  
Governing Equations ◽  
Vibration Properties ◽  
Wide Range ◽  
Forced Responses

Vibration properties of high-speed rotating and revolving planet rings with discrete and partially distributed stiffnesses were studied. The governing equations were obtained by Hamilton’s principle based on a rotating frame on the ring. The governing equations were cast in matrix differential operators and discretized, using Galerkin’s method. The eigenvalue problem was dealt with state space matrix, and the natural frequencies and vibration modes were computed in a wide range of rotation speed. The properties of natural frequencies and vibration modes with rotation speed were studied for free planet rings and planet rings with discrete and partially distributed stiffnesses. The influences of several parameters on the vibration properties of planet rings were also investigated. Finally, the forced responses of planet rings resulted from the excitation of rotating and revolving movement were studied. The results show that the revolving movement not only affects the free vibration of planet rings but results in excitation to the rings. Partially distributed stiffness changes the vibration modes heavily compared to the free planet ring. Each vibration mode comprises several nodal diameter components instead of a single component for a free planet ring. The distribution area and the number of partially distributed stiffnesses mainly affect the high-order frequencies. The forced responses caused by revolving movement are nonlinear and vary with a quasi-period of rotating speed, and the responses in the regions supported by partially distributed stiffnesses are suppressed.

scholarly journals Reliability of beams designed in accordance with Brazilian codes

2014 ◽  
Vol 7 (5) ◽  
pp. 723-746 ◽  
Author(s):  
D. M. Santos ◽  
F. R. Stucchi ◽  
A. T. Beck
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Composite Beams ◽  
Reinforced Concrete Beams ◽  
Steel Beams ◽  
Structural Elements ◽  
Pure Bending ◽  
Design Standards ◽  
Limit Values ◽  
Relative Safety

This paper presents an investigation on the safety of structural elements submitted to pure bending, produced in reinforced concrete, in steel and steel-concrete composites, and designed according to Brazilian codes NBR8681:2003, NBR6118:2007 and NBR8800:2008. The study allows a comparison of the relative safety of beams produced with these materials and designed using these codes. Comparative studies between the performances of different materials are difficult to find in the published literature. The present study shows that reliability indexes for reinforced concrete beams are satisfactory; however, results for steel beams are below limit values established in international design standards. Reliability indexes found herein for steel-concrete composite beams are intermediate to concrete and steel beams.

Dynamic Characteristics of a Long-Span Cable-Stayed Bridge

2011 ◽  
Vol 480-481 ◽  
pp. 1496-1501
Author(s):  
Liu Hui
Keyword(s):  
Finite Element ◽  
Dynamic Characteristics ◽  
Iteration Method ◽  
Natural Frequencies ◽  
Element Model ◽  
Vibration Modes ◽  
Cable Stayed Bridge ◽  
Long Span ◽  
Subspace Iteration ◽  
Floating System

In order to study the dynamic characteristics of a super-long-span cable-stayed bridge which is semi-floating system, the spatial finite element model of this cable-stayed bridge was established in ANSYS based on the finite element theory.Modal solution was conducted using subspace iteration method, and natural frequencies and vibration modes were obtained.The dynamic characteristics of this super-long-span cable-stayed bridge were then analyzed.Results showed that the super-long-span cable-stayed bridge of semi-floating system has long basic cycle, low natural frequencies, dense modes and intercoupling vibration modes.

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