A novel method for determining effective length factors for solid round steel leg members of guyed lattice towers with cross-bracing

2003 ◽  
Vol 30 (4) ◽  
pp. 780-786
Author(s):  
Yongcong Ding ◽  
Faouzi Ghrib ◽  
Sudip Bhattacharjee ◽  
Murty K.S Madugula
Keyword(s):  
Closed Form Solution ◽  
Form Solution ◽  
Effective Length ◽  
Rotational Stiffness ◽  
Element Analysis ◽  
Effective Length Factor ◽  
Novel Method ◽  
Lattice Tower ◽  
Lattice Towers ◽  
Communication Towers

A novel method is presented for determining the effective length factors (K factors) for solid round steel leg (vertical) members in all-welded guyed communication towers with cross-bracing. Deflections due to an arbitrary load were used to determine the restraining moments and rotational stiffness of the legs. Using the closed-form solution for buckling of a column with rotational restraint at both ends, K factors were computed. From the study it is found that the K factors varied from 0.61 to 1.00, depending on the relative sizes of the leg and bracing members. An expression for estimating the effective length factors for solid round steel leg members of all-welded guyed lattice towers with cross-bracing is developed.Key words: cross-bracing, effective length factor (K factor), finite element analysis, guyed lattice tower, solid round steel leg member, welded tower.

Buckling Analysis of Sway Steel Frames with Semi-Rigid Connections

2011 ◽  
Vol 250-253 ◽  
pp. 3876-3879
Author(s):  
Wan Zhen Wang ◽  
Ji Xiang Xu ◽  
Fei Yi Chen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Steel Frames ◽  
Buckling Analysis ◽  
Nonlinear Finite Element ◽  
Effective Length ◽  
Finite Element Models ◽  
Rotational Stiffness ◽  
Element Analysis ◽  
Effective Length Factor

The modified factor formulas, which are applicable to sway steel frames, are derived by considering joint relative rotational stiffness and adopting the modified stiffness factor. The finite element models of steel frames with semi-rigid and rigid connections are established using ANSYS program. Nonlinear finite element analysis of steel frames with two web and top-seat angles steel semi-rigid connections is conducted. Through bulking analysis of sway steel frames with semi-rigid connections, the effective length factor of sway steel frames is derived, which considers nonlinear rotation of two web and top-seat angles steel semi-rigid connections.

scholarly journals Determination of Constraint-Modified J-R Curves for Carbon Steel Storage Tanks

2002 ◽  
Author(s):  
P.-S. Lam ◽  
Y. J. Chao ◽  
X.-K. Zhu ◽  
Y. Kim ◽  
R. L. Sindelar
Keyword(s):  
Carbon Steel ◽  
Test Data ◽  
Storage Tank ◽  
Closed Form Solution ◽  
Crack Tip ◽  
Form Solution ◽  
Fracture Parameter ◽  
Element Analysis ◽  
Crack Tip Constraint ◽  
Senb Specimen

Mechanical testing of A285 carbon steel, a storage tank material, was performed to develop fracture properties based on the constraint theory of fracture mechanics. A series of single edge-notched bend (SENB) specimen designs with various levels of crack tip constraint were used. The variation of crack tip constraint was achieved by changing the ratio of the initial crack length to the specimen depth. The test data show that the J-R curves are specimen-design-dependent, which is known as the constraint effect. A two-parameter fracture methodology is adopted to construct a constraint-modified J-R curve, which is a function of the constraint parameter, A2, while J remains the loading parameter. This additional fracture parameter is derived from a closed form solution and can be extracted from the finite element analysis for a specific crack configuration. Using this set of SENB test data, a mathematical expression representing a family of the J-R curves for A285 carbon steel can be developed. It is shown that the predicted J-R curves match well with the SENB data over an extensive amount of crack growth. In addition, this expression is used to predict the J-R curve of a compact tension specimen (CT), and reasonable agreement to the actual test data is achieved. To demonstrate its application in a flaw stability evaluation, a generic A285 storage tank with a postulated axial flaw is used. For a flaw length of 10% of the tank height, the predicted J-R curve is found to be similar to that for a SENB specimen with a short notch, which is in a state of low constraint. This implies that the use of a J-R curve from the ASTM (American Society for Testing and Materials) standard designs, which typically are high constraint specimens, may be overly conservative for analysis of fracture resistance of large structures.

Analytical and Numerical Studies of a Thick Anisotropic Multilayered Fiber-Reinforced Composite Pressure Vessel

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Isaiah Ramos ◽  
Young Ho Park ◽  
Jordan Ulibarri-Sanchez
Keyword(s):  
Finite Element ◽  
Pressure Vessel ◽  
Structural Damage ◽  
Three Dimensional ◽  
Closed Form Solution ◽  
Form Solution ◽  
Fiber Reinforced ◽  
Element Analysis ◽  
Analytical Results ◽  
Composite Pressure Vessel

In this paper, we developed an exact analytical 3D elasticity solution to investigate mechanical behavior of a thick multilayered anisotropic fiber-reinforced pressure vessel subjected to multiple mechanical loadings. This closed-form solution was implemented in a computer program, and analytical results were compared to finite element analysis (FEA) calculations. In order to predict through-thickness stresses accurately, three-dimensional finite element meshes were used in the FEA since shell meshes can only be used to predict in-plane strength. Three-dimensional FEA results are in excellent agreement with the analytical results. Finally, using the proposed analytical approach, we evaluated structural damage and failure conditions of the composite pressure vessel using the Tsai–Wu failure criteria and predicted a maximum burst pressure.

Validation of Nitinol SMA Characteristics Using Finite Element Analysis and Closed Form Solutions

2013 ◽  
Vol 856 ◽  
pp. 147-152
Author(s):  
S.H. Adarsh ◽  
U.S. Mallikarjun
Keyword(s):  
Experimental Data ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Closed Form ◽  
Closed Form Solution ◽  
Form Solution ◽  
Fe Analysis ◽  
Element Analysis ◽  
Complex Behaviour ◽  
Closed Form Solutions

Shape Memory Alloys (SMA) are promising materials for actuation in space applications, because of the relatively large deformations and forces that they offer. However, their complex behaviour and interaction of several physical domains (electrical, thermal and mechanical), the study of SMA behaviour is a challenging field. Present work aims at correlating the Finite Element (FE) analysis of SMA with closed form solutions and experimental data. Though sufficient literature is available on closed form solution of SMA, not much detail is available on the Finite element Analysis. In the present work an attempt is made for characterization of SMA through solving the governing equations by established closed form solution, and finally correlating FE results with these data. Extensive experiments were conducted on 0.3mm diameter NiTinol SMA wire at various temperatures and stress conditions and these results were compared with FE analysis conducted using MSC.Marc. A comparison of results from finite element analysis with the experimental data exhibits fairly good agreement.

scholarly journals Displacement Formulations for Deformation and Vibration of Elastic Circular Torus

2021 ◽  
Author(s):  
bohua sun
Keyword(s):  
Free Vibration ◽  
Gaussian Curvature ◽  
Turning Point ◽  
Closed Form Solution ◽  
Complex Form ◽  
Form Solution ◽  
Element Analysis ◽  
Displacement Boundary ◽  
Engineering Mechanics ◽  
Maple Code

The formulation used by most of the studies on an elastic torus are either Reissner mixed formulation or Novozhilov's complex-form one, however, for vibration and some displacement boundary related problem of a torus, those formulations face a great challenge. It is highly demanded to have a displacement-type formulation for the torus. In this paper, I will carry on my previous work [ B.H. Sun, Closed-form solution of axisymmetric slender elastic toroidal shells. J. of Engineering Mechanics, 136 (2010) 1281-1288.], and with the help of my own maple code, I am able to simulate some typical problems and free vibration of the torus. The numerical results are verified by both finite element analysis and H. Reissner's formulation. My investigations show that both deformation and stress response of an elastic torus are sensitive to the radius ratio, and suggest that the analysis of a torus should be done by using the bending theory of a shell, and also reveal that the inner torus is stronger than outer torus due to the property of their Gaussian curvature. Regarding the free vibration of a torus, our analysis indicates that both initial in u and w direction must be included otherwise will cause big errors in eigenfrequency. One of the most intestine discovery is that the crowns of a torus are the turning point of the Gaussian curvature at the crown where the mechanics' response of inner and outer torus is almost separated.

scholarly journals Obtaining the Correspondence Between Bayesian and Neural Networks

1998 ◽  
Vol 12 (07) ◽  
pp. 901-920 ◽  
Author(s):  
A. Stassopoulou ◽  
M. Petrou
Keyword(s):  
Neural Network ◽  
Bayesian Network ◽  
Full Range ◽  
Closed Form Solution ◽  
Real Data ◽  
Form Solution ◽  
Least Square ◽  
Novel Method ◽  
Probability Matrices ◽  
Desertification Assessment

We present in this paper a novel method for eliciting the conditional probability matrices needed for a Bayesian network with the help of a neural network. We demonstrate how we can obtain a correspondence between the two networks by deriving a closed-form solution so that the outputs of the two networks are similar in the least square error sense, not only when determining the discriminant function, but for the full range of their outputs. For this purpose we take into consideration the probability density functions of the independent variables of the problem when we compute the least square error approximation. Our methodoloy is demonstrated with the help of some real data concerning the problem of risk of desertification assessment for some burned forests in Attica, Greece where the parameters of the Bayesian network constructed for this task are successfully estimated given a neural network trained with a set of data.

Strengthening of wide-flange columns under load

1990 ◽  
Vol 17 (5) ◽  
pp. 835-843 ◽  
Author(s):  
H. Marzouk ◽  
S. Mohan
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Critical Load ◽  
Closed Form Solution ◽  
Welding Process ◽  
Form Solution ◽  
Element Analysis ◽  
Welding Stress ◽  
Existing Structures ◽  
Welding Sequence

The present work deals with formulation of theoretical and analytical methods leading to the development of column strength curves. The formulations were developed for both elastic and inelastic behaviour. Two types of reinforcement have been developed for strengthening the W-shape columns under load. Since the column strength curves are based in part on the magnitude and distribution of residual stresses, it is extremely important to consider the new pattern of residual stresses due to welding process. Also, the welding sequence will affect the magnitude and distribution of residual stresses. Theoretical formulations leading to a closed-form solution for the prediction of critical load were developed for two types of strengthening using the superposition of original residual, new welding, and initial loading stresses. A nonlinear finite element analysis based on the large deformation theory of stability was used to predict the strengthened column critical load. It takes into consideration the effect of cooling residual stresses and new welding residual stresses. The formulations were incorporated with gradual penetration of yielding, the spreading of inelastic zones along the member length, the presence of residual stresses, and strain hardening of the material. Experiments were carried out to determine the actual capacity of strengthened columns. Seven specimens were tested using two and four strengthening plates. The welding stresses were measured through a series of experiments, and it was found that the parabolic distribution is a very close approximation to the actual new welding stress distribution. Key words: reinforcement of steel columns, welding stresses, welding sequence, strengthening of existing structures, buckling, steel plating, finite element.

Using Isochronous Method to Calculate Creep Damage in Pressure Vessel Components: Part 2

2017 ◽  
Author(s):  
Chithranjan Nadarajah ◽  
Benjamin F. Hantz ◽  
Sujay Krishnamurthy
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Pressure Vessel ◽  
Closed Form Solution ◽  
Creep Damage ◽  
Form Solution ◽  
Creep Model ◽  
Stress Strain ◽  
Element Analysis ◽  
Good Agreement

This paper is Part 2 of two papers illustrating how isochronous stress strain curves can be used to calculate creep stresses and damage for pressure vessel components. Part 1 [1], illustrated the use of isochronous stress strain curves to obtain creep stresses and damages on two simple example problems which were solved using closed form solution. In Part 2, the isochronous method is implemented in finite element analysis to determine creep stresses and damages on pressure vessel components. Various different pressure vessel components are studied using this method and the results obtained using this method is compared time explicit Omega creep model. The results obtained from the isochronous method is found to be in good agreement with the time explicit Omega creep model.

Experimental basis for the effective length factors of steel solid round cross-braced diagonals in CSA Standard S37-01

2002 ◽  
Vol 29 (3) ◽  
pp. 430-435
Author(s):  
Yongcong Ding ◽  
Kalid S Jaboo ◽  
Yean Sun ◽  
Murty K.S Madugula
Keyword(s):  
Effective Length ◽  
Test Results ◽  
Experimental Basis ◽  
Failure Loads ◽  
Lattice Tower ◽  
Communication Towers ◽  
Round Cross ◽  
Compressive Resistance

The effective length factors for steel solid round diagonals in all-welded communication towers are investigated in this paper to provide experimental basis for the relevant clauses in CSA Standard S37-01. The results of a total of 31 all-welded lattice tower specimens with three types of cross-braced diagonals are presented. The failure loads for these members were determined from the maximum axial strains measured during the tests. The effective length factors were then back-calculated from the experimental failure loads using the compressive resistance formulas. The test results showed that even the significantly lower effective length factors specified in CSA S37-01, compared to CSA S37-94, are still conservative.Key words: all-welded towers, communication towers, cross-bracing, effective length factors, solid round steel diagonals.

Equivalent Elastic Constants of Truss Core Sandwich Plates

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Hong-Xia Wang ◽  
Samuel W. Chung
Keyword(s):  
Elastic Constants ◽  
A Priori ◽  
Three Dimensional ◽  
Closed Form Solution ◽  
Elastic Stiffness ◽  
Form Solution ◽  
Laminated Plates ◽  
Element Analysis ◽  
Truss Core ◽  
Anisotropic Elastic

A plate structure of a triangular truss core sandwiched by two panels is treated as an equivalent homogeneous laminated plate by obtaining equivalent anisotropic elastic constants. The equivalent elastic constants are obtained by considering generalized Hook’s law of a three dimensional elastic body with no a priori assumption and the equilibrium of a segment deformed by bending moments. To verify the accuracy of the equivalent elastic constants, a linear static analysis of sandwiched aluminum plates subjected to lateral pressure is carried out. The results of the finite element analysis applied to the equivalent laminated plates are compared with those of a NASTRAN analysis of the original structural layouts. The results are also compared with a closed-form solution, which simplifies the sandwiched plate as a homogeneous orthotropic thick plate continuum (Lok and Cheng, 2000, “Elastic Stiffness Properties and Behavior of Truss-Core Sandwich Panel,” J. Struct. Eng., 126(5), pp. 552–559). As the maximum deflections of three analyses agreed closely, one has assurance that the method of the homogeneous plate with equivalent elastic constants is valid and useful.

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