3d Stress Design

3D STRESS DESIGN

Project can be categorized into two tenures – technical planning and implementation. Technical planning is subdivided into four – visualization, analysis, design and drafting. Hitherto, technical implementation too is divided into four – quality control, execution (construction and assembly), marketing and customer services. Diabolic planning is required to restrain on field afflictions. Analysis Load Combinations

1. D 1.0

6. D 1.0 L 0.75 DY 0.75

2. D 1.0 L 1.0

7. D 1.0 DY 0.75

3. D 1.0 L 1.0 DY 1.0

8. D 0.6 DY 1.0

4. D 1.0 DY 1.0

9. D 0.6 DY 0.7

5. D 1.0 L 0.75

10. D 0.6 DY 0.525

D – Dead, L – Live (Static), DY – Dynamic Member forces (as in Staad output): Beam

L/C

Section

Axial Force

Shear-Y

Shear-Z

Torsion

Moment-Y

Moment-Z

Fx

Fy

Fz

Mx

My

Mz

Design Procedure for Metal Section properties: D – Overall Depth, B – Overall Breadth, L – Overall Length, t – Web Thickness, T – Flange Thickness, Ax – Cross sectional area, Zx; Zy; Zz – Section modules in x, y and z-axis. Zx = √ (Zz2 + Zy2 + Zz * Zy * Sin B/4 * Cos B/4) Check for longitudinal shear Dvd

=

Fy [(D – t) * t]

(6.4.2, IS 800)

≤

Dva

Check for axial tension

Hat,cal Hat

=

(Fx / Ax) Hat

(4.1, IS 800)

≤

1.0

Check for axial compression

Hac,cal Hac

=

(Fx / Ax) Hac

(5.1, IS 800)

≤

1.0

Check for lateral shear Lateral shear stress, Hls = ν (Dva + Hac) Hls,cal

=

Fz [2 * B * T]

≤

Hls

1

04-Oct-09

Check for bending in tension

(6.2, IS 800)

Hbtz,cal / Hbt = (Mz / Zz) / Hbt

≤

1.0

Hbty,cal / Hbt = (My / Zy) / Hbt

≤

1.0

Check for bending in compression

(6.2, IS 800)

Hbcz,cal / Hbc = (Mz / Zz) / Hbc

≤

1.0

Hbcy,cal / Hbc = (My / Zy) / Hbc

≤

1.0

≤

1.0

Check for torsion Torsion stress, Htor = ν (Hbt + Hbc) Htor,cal / Htor = (Mx / Zx) / Htor

Combined axial and bending in compression & torsion

Hac,cal Hac

+

Hbcz,cal Hbc

Hbcy,cal

+

+

Hbc

(7.1.1, IS 800)

Htor,cal Htor

≤

Combined axial and bending in tension

Hat,cal Hat

+

Hbtz,cal Hbt

+

1.0 (7.1.2, IS 800)

Hbty,cal

≤

Hbt

1.0

Check for Dynamics (general structures) Maximum allowable deflection, Kmax = L / 250 Obtained deflection, K ≤ Kmax Obtained frequency, ƒ = 0.2√ (g/K) ≥ Natural frequency (ƒn = 0.2g) Design Procedure for RCC Section properties: D – Overall Depth, B – Overall Breadth, L – Overall Length, c – clear cover, d – Effective depth, b – Effective breadth, Zx; Zy; Zz – Section modules in x, y and zaxis. Zx = √ (Zz2 + Zy2 + Zz * Zy * Sin B/4 * Cos B/4) Material properties: fck – Characteristic strength of concrete (after 28 days), fy – Characteristics strength of steel, m – Modular ratio, Hcac; Hcbc ≤ 0.33fck, Hcat; Hcbt ≤ 0.17√fck ≤ 1 N/mm2 (Conservatively considered as null to avoid cracks. Moreover minimum reinforcement to be provided, spacing between any should not exceed 150 mm c/c and should not be less than 75 mm c/c) Check for torsion: Htor,cal ≤ Htor Otherwise, Astor = (Htor,cal - Htor)bd / 0.67fy Check for total shear: V = Fy + Fz, Dv = V / bd ≤ Dc Otherwise, Asts = V / [m (Dv - Dc)] + Astor Check for axial tension: Hcat = 0 Otherwise, Asat = Fx / 0.6fy Check for axial compression: Hcac,cal ≤ Hcac Otherwise, Asac = (Hcac,cal - Hcac)bd / 0.6fy Check for bending in tension: Hcbt = 0

2

04-Oct-09

Otherwise, Asbtz = (Mz / d) / 0.67fy; Asbty = (My / b) / 0.67fy Check for bending in compression: Hcbcz,cal; Hcbcy,cal ≤ Hcbc Otherwise, Asbcz = (Hcbcz,cal - Hcbc)bd / 0.67fy; Asbcy = (Hcbcy,cal - Hcbc)bd / 0.67fy Combined axial and bending in compression Ast,top = Asac / 4 + Asbcz, Ast,side = Asac / 2 + Asbcy For columns, Ast,all = Asac + Asbcz + Asbcy Combined axial and bending in tension Ast,bottom = Asat / 4 + Asbtz, Ast,side = Asat / 2 + Asbty For columns, Ast,all = Asat + Asbtz + Asbty Check for Dynamic (general structures) Maximum allowable deflection, Kmax = L / 250 Obtained deflection, K ≤ Kmax Obtained frequency, ƒ = 0.2√ (g/K) ≥ Natural frequency (ƒn = 0.2g) Self Compacted Concrete recommended: RCC

Approximate Mix Proportion

Cement

CA

FA

Water

Grade

cft

Cement

CA

FA

kg

cft

cft

l

M15

1

1

2

4

7.48

0.35

0.70

3.74

M20

1

1

1.5

3

9.34

0.33

0.66

4.67

M25

1

1

1

2

9.34

0.22

0.44

4.67

M30

1

1

0.5

1

9.97

0.12

0.23

4.98

M35

1

1

0.5

1

10.59

0.12

0.25

5.30

M40

1

1

0.5

1

11.21

0.13

0.26

5.61

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.

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04-Oct-09