3d Manual Analysis

3D MANUAL ANALYSIS

It’s easy to calculate analysis parameters in one dimension, but not tedious to determine in remaining two directions. Academic and research scholars adopt forward biases but professionals are compelled to go by reverse biases due to economic constrains. The former go by their experience, senior commonness and right long way but the latter employ the codes’, unique, distinct and innovative talent and right shortcut. The approaches furnished below can be utilized to approximately cross check, the software analysis. M

Beam Bending Theory,

I

From the fundamentals,

My

≤

σ

y M

=

=

Z

F A

σz ≥ σy

By design orientation, Thus,

)

=

Mz Z y Zz

;

Fz

≥

Fy A z Ay

For non-axially loaded members, 2 ν σy Ax ≤ (Fx = σx Ax) ≤ ν (σz + σy) Ax Torsion, Mx = Fx Zx / Ax, we know Zx = √ (Zz2 + Zy2 + Zz * Zy * Sin 8/4 * Cos 8/4) Thus the maximum manual analysis forces are Fx

Fy

Fz

Mx

My

2 ν σy Ax

Fy

Mz

Fy A z

F x Zx

Mz Z y

Ay

Ax

Zz

Fy

Fz

Mx

My

Mz

Fx Ay

Fy A z

F x Zx

Fy Zy

Fz Zz

2 ν Ax

Ay

Ax

Ay

Az

Mz

For pure axially loaded members Fx Fx

Hitherto from the above the deflections can also be evolved which are solely depended on the support conditions. (Please do try for simple supported!)

Ten Commandments in ‘AnD’ 1. Software packages’ to be used for conservative 3D-Analysis. 2. The structure to be reliable as the wind forces distributed realistically in all directions.

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02-Dec-09

3. Though the fundamental natural frequency (Mode I) to be greater than 0.2g, the general structure is considered as dynamically sensitive as per IS code since the aspect ratios (height/width) is more than 5... 4. The structure is stable only if more than three vibration modes achieved. 5. The structure will be balanced, if leg forces in compression are in similitude to tension. Moreover, there should not be uplift in the mat footing. 6. The structure will not burst if symmetric and concentric sections have been provided as main frame members. 7. Pragmatic sway of the structure to be achieved, which is obviously less than the allowable. 8. Optimum 3D-Design to be accomplished. 9. Due to economic constrains, the structure may not withstand to wind speed greater than 210 kmph.

10. Discrepancy intimidated to rectify. Go by the essence rather than the appearance.

About the author Mahaveer Janapala is a Structural Engineer and Interface Manager in an EPC Company. Licensed to www.ghmc.gov.in. He is a postgraduate in Structural Engineering and a graduate in Civil Engineering from Osmania University (www.osmania.ac.in). He has a post

graduation

in

Biblical

Counseling

from

‘CARE’

Counseling

Institute

(http://carecounseling.mahalife.com/) affiliated to ‘TOPIC’ (www.topic.us). He was born (1977), brought up, educated, working and residing in Hyderabad, India. While pursuing technical post graduation he wasn’t able to evolve 3D Manual Analysis.

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02-Dec-09