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 INVESTIGATION OF RATIONAL DEPTH OF CASTELLATED STEEL I‐BEAMS/SIJŲ SU PERFORUOTĄJA SIENELE RACIONALAUS AUKŠČIO TYRIMAS

2008 ◽  
Vol 14 (3) ◽  
pp. 163-168 ◽  
Author(s):  
Benediktas Dervinis ◽  
Audronis Kazimieras Kvedaras
Keyword(s):  
Finite Element Method ◽  
Cross Section ◽  
Linear Analysis ◽  
Cross Sectional Area ◽  
Steel Beams ◽  
Sectional Area ◽  
The Finite Element Method ◽  
Cross Sectional ◽  
Distributed Load ◽  
The Web

There are many methods to calculate castellated steel beams; however, neither of these methods determines the rational cross‐section selection. Selecting the rational cross‐section induces a significant reduction in the quantity of steel. A new algorithm for selecting the rational dimensions of the castellated beams is presented in this paper. In future works it may be adopted and used for design. 12 m long beams, web thickness 6–12 mm and web depth 500–1000 mm are analysed in this paper. Opening size used varies from half of the web depth to the total web depth minus 100 mm. The chosen cross‐sectional area of two flanges is equal to the cross‐sectional area of the web. The thickness of the flanges is twice as big as the thickness of the web. The finite element method was used for geometrical and physical non‐linear analysis of the castellated beams under a uniformly distributed load. The upper flanges of the beams are restrained out of the plane. The results are presented in relevant charts. Santrauka Yra ne viena sijų su perforuotąja sienele skaičiavimo teorija, tačiau nė viena iš jų nenurodo, kaip parinkti racionalius tokių sijų skerspjūvio matmenis. Jeigu sijos su perforuotąja sienele skerspjūvio matmenys būtų parinkti racionalūs, galima būtų sutaupyti nemažai plieno tokioms sijoms gaminti. Buvo analizuotos sijos, kurių ilgis 12 m ir sienelės storis 6−12 mm, o aukštis 500−1 000 mm. Perforacijos skersmuo buvo parinktas nuo pusės sienelės aukščio iki sienelės aukščio atėmus 100 mm. Dviejų lentynų plotas buvo parinktas lygus sienelės plotui, o lentynų storis lygus dviem sienelės storiams. Analizuotos sijos buvo dviatramės, apkrautos tolygiai išskirstytąja apkrova, jų viršutinės lentynos buvo suvaržytos iš plokštumos. Sijos skaičiuotos baigtinių elementų metodu geometriškai ir fiziškai netiesiškai. Išanalizavus šias sijas, skaičiavimo rezultatai buvo pateikti grafikų pavidalu.

scholarly journals Changes In Cross-Sectional Area Of Gateroads In Longwalls With Roof Caving, Ventilated With “U” And “Y” Systems

2015 ◽  
Vol 60 (2) ◽  
pp. 549-564 ◽  
Author(s):  
Stanisław Prusek
Keyword(s):  
Ventilation System ◽  
Coal Pillar ◽  
Cross Sectional Area ◽  
Longwall Face ◽  
Sectional Area ◽  
The Finite Element Method ◽  
Coal Basin ◽  
Cross Sectional ◽  
Roof Caving ◽  
Upper Silesian Coal Basin

Abstract Content: In the paper results of measurements of underground gateroad deformations are presented. The measurements were conducted in seven collieries in the Upper Silesian Coal Basin. Altogether 28 gateroads were analysed:12 longwalls with „Y“ and 4 longwalls with „U“ ventilation system. Based on results of measurements, changes in cross-sectional area of gateroads were calculated and then referred to their original dimensions (when they were developed). Values of cross-sectional area of gateroads in front of and behind the longwall face are presented. Differences in deformation of gateroads in longwalls with the “U” ventilation system, surrounded by unmined coal, and/or goaf on one side were determined. Changes in cross-sectional area of reused gateroads, and newly driven ones (with a coal pillar separating the goaf from the working), were estimated. For gateroads of the longwalls with “Y” ventilation system their deformations at a distance of 200 metres behind the longwall face was determined. For selected gateroads their convergence was calculated with numerical modeling and a method developed at GIG. Calculations were made with Phase2 software based on the finite element method (FEM). Accuracy of forecasted gateroad deformations were assessed through comparing them with the results of underground measurements.

Possibility of Application of the Simulation Based Reliability Assessment Method in Modeling of Structures

2013 ◽  
Vol 486 ◽  
pp. 129-134
Author(s):  
Petr Kesl ◽  
František Plánička
Keyword(s):  
Reliability Assessment ◽  
Random Variable ◽  
Assessment Method ◽  
Composite Model ◽  
Steel Beam ◽  
Sectional Area ◽  
Steel Component ◽  
Cross Sectional ◽  
Simply Supported ◽  
Simulation Based

The article deals with possibility of application of the simulation based reliability assessment SBRA Method in modeling of structures in the field of judgement of their serviceability. A steel simply supported beam of hollow circular cross sectional area was taken into account. Using rules of modeling it was modeled by the beam of the same shape, when its material was the composite material. Deflection of it was determined experimentally and using modeling rules the corresponding deflection of the steel beam was determined. Deflections of steel component and its composite model were determined using SBRA Method, realized when following random variable quantities as dimensions of bodies and corresponding geometric quantities, Young ́s modulus of elasticity E and loading force were taken into account.

Strengthening of I-Section Steel Beams by Prestressing Strands

2020 ◽  
Vol 857 ◽  
pp. 169-176
Author(s):  
Kamal Sh. Mahmoud ◽  
Mohammed M. Rasheed ◽  
Saad Kh. Mohaisen
Keyword(s):  
Applied Load ◽  
Reference Beam ◽  
Experimental Tests ◽  
The Other ◽  
Steel Beams ◽  
Steel Beam ◽  
Maximum Deflection ◽  
Sectional Area ◽  
Simply Supported ◽  
Prestressing Strand

Six I-section steel beams had been fabricated and tested to understand the influence of prestressing strand on the load deflection behavior of steel beam. All tested beams are simply supported having the same gross sectional area with clear span (2850) mm, five beams strengthened by two low relaxation seven wire strands, while sixth beam is the reference one. The strengthening beams were subjected jacking stress equal to (1120MPa) and subdivided according to prestressing strand positions (eccentricity). From the experimental tests, it can be noted that, the load deflection curves for strengthened beams are stiffer as compared with reference beam and the percentage of ductility for strengthened beams were decreased when the eccentricity positions change form (0 to 96)mm respectively, on the other hand, the percentage of increasing in maximum applied load for strengthened beams were increased with increasing of strands eccentricity and the maximum applied load reaches to 61.74% as compared with reference, also, the percentage increasing in maximum deflection at middle span for strengthened beams decreases with increasing of strands eccentricity and the minimum percentage of decreasing at middle span of strengthened specimens reaches to 36.31% as compared with the reference beam.

Pelvic Canal Narrowing Caused by Triple Pelvic Osteotomy in the Dog

1994 ◽  
Vol 07 (03) ◽  
pp. 110-113 ◽  
Author(s):  
D. L. Holmberg ◽  
M. B. Hurtig ◽  
H. R. Sukhiani
Keyword(s):  
Postoperative Complications ◽  
Pelvic Osteotomy ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Canal Width ◽  
Operative Complications ◽  
Post Operative Complications

SummaryDuring a triple pelvic osteotomy, rotation of the free acetabular segment causes the pubic remnant on the acetabulum to rotate into the pelvic canal. The resulting narrowing may cause complications by impingement on the organs within the pelvic canal. Triple pelvic osteotomies were performed on ten cadaver pelves with pubic remnants equal to 0, 25, and 50% of the hemi-pubic length and angles of acetabular rotation of 20, 30, and 40 degrees. All combinations of pubic remnant lengths and angles of acetabular rotation caused a significant reduction in pelvic canal-width and cross-sectional area, when compared to the inact pelvis. Zero, 25, and 50% pubic remnants result in 15, 35, and 50% reductions in pelvic canal width respectively. Overrotation of the acetabulum should be avoided and the pubic remnant on the acetabular segment should be minimized to reduce postoperative complications due to pelvic canal narrowing.When performing triple pelvic osteotomies, the length of the pubic remnant on the acetabular segment and the angle of acetabular rotation both significantly narrow the pelvic canal. To reduce post-operative complications, due to narrowing of the pelvic canal, overrotation of the acetabulum should be avoided and the length of the pubic remnant should be minimized.

DETERMINATION OF THE FUNCTION OF THE ROD’S CROSS-SECTIONAL AREA USING VIBRATION EIGENFREQUENCIES

2020 ◽  
Vol 0 (4) ◽  
pp. 19-24
Author(s):  
I.M. UTYASHEV ◽  
◽  
A.A. AITBAEVA ◽  
A.A. YULMUKHAMETOV ◽  
◽  
...  
Keyword(s):  
Cross Sectional Area ◽  
Variable Cross ◽  
Sectional Area ◽  
Longitudinal Vibrations ◽  
Cross Sectional ◽  
Method Error ◽  
Various Boundary Conditions ◽  
Elastic Fixation ◽  
Crosssectional Area

The paper presents solutions to the direct and inverse problems on longitudinal vibrations of a rod with a variable cross-sectional area. The law of variation of the cross-sectional area is modeled as an exponential function of a polynomial of degree n . The method for reconstructing this function is based on representing the fundamental system of solutions of the direct problem in the form of a Maclaurin series in the variables x and λ. Examples of solutions for various section functions and various boundary conditions are given. It is shown that to recover n unknown coefficients of a polynomial, n eigenvalues are required, and the solution is dual. An unambiguous solution was obtained only for the case of elastic fixation at one of the rod’s ends. The numerical estimation of the method error was made using input data noise. It is shown that the error in finding the variable crosssectional area is less than 1% with the error in the eigenvalues of longitudinal vibrations not exceeding 0.0001.

Changes in the parameters of nasal breathing and parameters of the upper respiratory tract during orthognathic operations in patients with II and III skeletal class of jaw anomalies

2020 ◽  
pp. 22-27
Author(s):  
S.Sh. Gammadaeva ◽  
M.I. Misirkhanova ◽  
A.Yu. Drobyshev
Keyword(s):  
Respiratory Tract ◽  
Nasal Cavity ◽  
Nasal Septum ◽  
Cross Sectional Area ◽  
Upper Respiratory Tract ◽  
Sectional Area ◽  
Nasal Breathing ◽  
Cross Sectional ◽  
Skeletal Class ◽  
Upper Respiratory

The study analyzed the functional parameters of nasal breathing, linear parameters of the nasal aperture, nasal cavity and nasopharynx, volumetric parameters of the upper airways in patients with II and III skeletal class of jaw anomalies before and after orthognathic surgery. The respiratory function of the nose was assessed using a rhinomanometric complex. According to rhinoresistometry data, nasal resistance and hydraulic diameter were assessed. According to the data of acoustic rhinometry, the minimum cross-sectional area along the internal valve, the minimum cross-sectional area on the head of the inferior turbinate and nasal septum and related parameters were estimated. According to the CBCT data, the state of the nasal septum, the inferior turbinates, the nasal aperture, the state of the nasal cavity, and the linear values of the upper respiratory tract (nasopharynx) were analyzed. The patients were divided into 4 groups according to the classification of the patency of the nasal passages by

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