Khaled Megahed

50 Questions 138 Answers 0 Followers

Questions related from Khaled Megahed

In Abaqus python API, is these formulation give the same results?

If 'P' is the part name The first form: P.ReferencePoint(point=(0, 0, 0)) R= P.referencePoints[l] P.DatumPointByOffset(point=R, vector=(10,0,0)) P.DatumPointByOffset(point=R,...

11 November 2019 4,518 1 View

How to define a rigid link between two points in Abaqus?

I can use rigid body element or MPC constraint (type beam). What the difference between them? Is there any alternative way to define this rigid link? Thanks for reading

10 October 2019 5,691 3 View

Which is faster in writing code; using the built in trigonometric functions or using power series expansions?

Sometimes, for small angle the trigonometric, expression like sin(theta)/theta become produce ill-conditioned.

05 May 2019 5,202 2 View

What is the Balance laws in term of 2nd Piola-Kirchhoff stress tensor?

The balance laws could be defined in term of Cauchy stress and 1st Piola-Kirchhoff stress tensor as follow https://en.wikipedia.org/wiki/Continuum_mechanics But could I define it in term of...

04 April 2019 6,425 7 View

What is the difference between variation in displacement and virtual displacement?

Also when referring to variation in the work (virtual work), we use virtual rotation not rotation variation? Thanks.

04 April 2019 5,394 11 View

How to perform bifurcation analysis on structures?

I would be grateful for any references or sites. Thanks

04 April 2019 8,832 1 View

What is the types of solution of a dynamic problem?

Thanks

04 April 2019 4,239 1 View

How to extract the potential energy of conservative moment?

Some researchers consider rotation variables as work-conjugate with moments, others think that the displacement derivatives is, and others use semi tangential rotation as work-conjugate to...

04 April 2019 5,464 4 View

Do I need to attend a conference if my paper has been accepted for the conference?

Thanks.

04 April 2019 5,207 1 View

At implementing damage model, How could I get the effective stress-strain curve or damage parameter from true stress strain curve?

Most experimental results include true strain curve. How could I experimentally or theoretically reach effective stress strain curve or damage parameter for damage model? Thanks

03 March 2019 7,702 12 View

At implementing damage model, effective stress-strain curve used should not include softening part. Is it right?

Using damage model includes the relation between the effective and true stress. The true stress-strain curve is the stress-strain curve measured directly from experimental tests which could...

03 March 2019 3,490 12 View

Anyone has a link to download KM-Editor program?

Thanks.

03 March 2019 6,931 1 View

How to model anistropic damage in concrete material?

Any papers, books,codes, or sites as a start? Thank you.

03 March 2019 7,809 3 View

What is the accuracy of wind tunnel to model real structures?

Could wind tunnel provide accurate results to wind load distribution over the building? What if the building is very flexible like cable stayed bridges or tall building. Could it be simulated...

03 March 2019 6,346 13 View

What is the allowable lateral acceleration of tall building due to wind load?

People feel uncomfortable in the upper stairs of the tall building when the building move laterally due to wind load or to be accurate the lateral acceleration of the building. Is their any...

03 March 2019 5,170 10 View

Could I model a reinforced concrete member as a wire element in ABAQUS?

In shell element I could define rebars layers to define reinforcement, but could I implement rebars in wire element? Thanks

03 March 2019 2,451 7 View

How to implement plastic hinge with capacity interaction between axial load and bending moment in ABAQUS?

In 3D frame analysis, using elastic element with plastic hinge at nodes accelerate the solution time instead of using distributed plasticity. But most plastic hinges include interaction between...

03 March 2019 852 4 View

Which software application is best for plotting this graph?

I encountered similar graphs like the one shown in the attached figure in many papers and researches. Does anyone use a certain software to draw this type of graphs?

02 February 2019 6,314 12 View

Which model is recommended in concrete fracture, fixed or rotating smeared crack?

In modeling concrete fracture, I could use fixed or rotating smeared crack model. But when could I use each of them.

02 February 2019 4,208 9 View

Which stress notation in the following photos does Abaqus use in writing Umat?

STRESS(4) mean sigma(1,2) or sigma(2,3)? Thanks.

02 February 2019 934 1 View

In Return Mapping algorithm, should each increment for getting plastic multiplier value be positive or the overall value of it?

When using Return Mapping algorithm, I implement Newton–Raphson iteration to reach the value of plastic multiplier. I know that the total value of plastic multiplier should not be negative. But,...

02 February 2019 8,479 5 View

Do anyone have a simplified explanation, reference, or source code in using a return-map algorithm in plasticity?

I encountered a return-map technique in many papers but I do not understand how it works.

02 February 2019 6,127 3 View

Why does arc-length method diverge when the stiffness approach zero?

I tried to code this method and it diverges when the stiffness approach zero. As, calculating load vector coefficient ∆λ requires having inverse of the stiffness as shown in the attached photo...

02 February 2019 5,306 4 View

Does anyone read about using multi-directional cracks in 3D modeling of concrete?

I encountered using multi-directional cracks model in 2D elements, but could it be used for 3D concrete elements?

02 February 2019 273 15 View

What is the shape of loading and unloading curve of concrete in tension?

Also how could I identify the pre-transition and post-transition parts of strain increment?

02 February 2019 5,121 6 View

Why does Etabs software calculate magnified moment (ACI -318) due second order effects in a different way?

These attached figures are captured from Concrete Frame Design Manual using ACI-318 attached with Etabs Design examples. It calculates the amplified moment due to second order effects using this...

02 February 2019 4,106 5 View

Radial Return Mapping Algorithm

In radial RMA, the deviatoric parts of trail stress and iteration stress have the same direction, so the calculated shear stress after convergence is just a scale down to the trail shear stress...

01 January 1970 6,010 1 View

Difference between first and second Piola-Kirchhoff stress vector

what is the difference between them? Which one could I use in beam element - shell -solid element? I read that beam uses first and shell uses second one, why? and what is the conjecture strain...

01 January 1970 9,224 12 View

Torsional rotation of multi story building under dead load.

Could the layout of the shear walls in multi story building induce torsional rotation due to dead load only? I faced this problem when analyzing a building in Etabs. Thanks

01 January 1970 4,359 10 View

The effect of torsional rotation on multi story building under seismic loading

Building exhibit torsional rotation under seismic loading due distance between the center of mass and center of rigidity. According to building codes, does this distance or torsional rotation have...

01 January 1970 6,450 8 View

Open source code finite element software which could deal with finite-strain deformation

I would like to know a finite element software which provides open source codes for large deformation analysis for beam and shell elements.

01 January 1970 5,602 18 View

Beam element formulation with large displacement

Anyone has source code for beam element formulation with large deformation and large displacement. I tried to model it but the problem is in taking into account finite rotation. Most books written...

01 January 1970 2,595 3 View

Tensor to matrix notation

How could I write the following formula in matrix notation? Any references, sites, or codes? Thanks

01 January 1970 6,633 3 View

Aerodynamic damping (negative - positive)

In textbook I read this sentence "In the case of positive aerodynamic damping the forces generated by motion through the airstream tend to oppose the motion. Negative damping tends to reinforce...

01 January 1970 4,944 4 View

Vortex shedding frequency

why lateral-force ﬂuctuations frequency is half longitudinal-force ﬂuctuations in turbulence flow or wind simulation?

01 January 1970 9,649 8 View

CWE-Simulation-Tool for wind simulation

How could I use this tool to reach to wind pressure distribution over simulated building and How could I deal generally with the results? Thank you

01 January 1970 699 5 View

Shape function of large 3D rotations in FEA

when using interpolation functions to get the interpolated values of displacement and rotation in Gauss point, we could define two separate equations; one for the displacement and one for the...

01 January 1970 8,404 3 View

The reasons for membrane locking in shell finite element?

I read about the membrane and shear locking appearing in shell element. Most references explain the reasons for shear locking but do not provide sufficient explanations for membrane locking. I...

01 January 1970 10,068 2 View

Mixed finite element method in structural analysis?

I am a beginner in understanding mixed FEM in structural analysis and I would be grateful for any advice, or reference that could help about this topic. Thanks for reading.

01 January 1970 9,366 2 View

Non-conservative loads

What is the types of non conservative loads? distributed loads, concentrated loads, concentrated moments. what is the effect of non conservative load in solving finite element problems? Should...

01 January 1970 5,804 5 View

Semi-tangential rotation and moment

How the total potential energy is a unique function with respect to semi-tangential rotation? Also how the tangent stiffness matrix of space elements based on semi-tangential moment is symmetric?

01 January 1970 6,209 2 View

Constitutive equation for stress-strain relation

what is the difference between the C value in both equations in the attached photo?

01 January 1970 3,303 8 View

Nonlinear analysis using Lagrangian formulation

which is the best for modelling different continuum and structural elements; updated Lagrangian formulation or total Lagrangian formulation. Thanks

01 January 1970 9,003 8 View

What is the tensor type for these physical quantities?

What is the tensor type for Green Lagrange strain tensor and 2nd 2nd piola kirchhoff tensor? Stress and strain are called 2nd order tensor because they follow the transformation rule: sigma`= R *...

01 January 1970 7,806 5 View

Symmetry of stiffness matrix of structure under conservative forces

If a system subjected to conservative forces and moments, at any circumstances the stiffness matrix could be unsymmetric

01 January 1970 5,939 5 View

The most efficient shell model?

what is the shell model with best performance for modeling shell element; using MITCn model or DKT or exact shell model proposed by JC Simo or ANDES elements? also the shape of it; quadratic or...

01 January 1970 3,556 2 View

Open source mesh generator?

I am looking for open source code for generating mesh for shell and solid elements. Any suggestions? Thanks.

01 January 1970 1,090 5 View

Tensor notation to matrix notation

How could I convert this Tensor notation in the attached photo into Matrix notation? Any references, website or codes. Thanks

01 January 1970 9,877 2 View

Drilling dof (degree of freedom) in finite shell element

There are several shell models that take into account drilling dof in shell formulation, and others not. What is the effect of using this dof in the accuracy and convergence rate of finite...

01 January 1970 474 3 View

Finite element locking in finite shell element

When solving shear or membrane locking in shell element, most researchers assume shear and membrane fields or stress field for the element using mixed formulations. What is the methodology to...

01 January 1970 2,489 2 View