Basic Structural Design Concepts

7/27/2019 Basic Structural Design Concepts

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BASIC STRUCTURAL

DESIGN CONCEPTS

MASONRY & R.C.C

STRUCTURES

Engr. Naveed RashidDirector

Planning & Design Directorate

Punjab Buildings Department

Lahore


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Basic Concept A structure is an assembly of members,

each of which is subjected to:

bending or

direct forces (either tensile or compressive) or,

a combination of bending and direct force.


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Design

Design includes accessing and providing

resistance against:

the moments,

the forces, and

other effects on the member.

(temperature etc)


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Efficient Design

An efficiently designed structure is one in which themembers are arranged in such a way that the

weight, loads and forces are transmitted to the

foundations by the cheapest means consistent with

the intended use of the structure. Experience and good judgment are as important for

safe and economical structures as calculations.

Complex mathematics should not be allowed to

confuse the sense of good engineering.

Same degree of accuracy should be maintained

throughout the calculations.


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Design Codes

Structural Design is controlled by codes,

even within such bounds, the designer must

exercise judgment in his interpretation of the

requirements. Building code requirements for structural

concrete (ACI318-11).

Uniform Building Code (UBC)

International Building Code (IBC)

Building Code of Pakistan.


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Economical Structure

In beams and slabs much of concrete is in

tension and therefore neglected in the

calculations, it is economical to use lean

concrete than a rich one. In columns, where all the concrete is in

compression, the use of rich concrete is more

economical. The use of steel in compression is always

uneconomical.


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Drawings

All drawings for one contact, the same conventionsare adopted and uniformity of appearance and sizeshould be aimed at, thereby making the drawingseasier to read.

The scales adopted should be commensurate withthe amount of detail to be shown.

In reinforced concrete details the outline of concreteis to be indicated by a thin line and to show thereinforcement by bold lines.

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Safety Factors

Ratio of the greatest load that a structure can

carry to the actual loading for which it has

been designed.

CP114:

FOS for concrete = 3

FOS for steel = 2

ACI Code: FOS is applied on loads.


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Characteristic Loads

Dead Loads (DL)

Imposed/Live Loads (LL)

Wind Forces

Seismic Forces


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Types Of Structures

Load Bearing Masonry Structure

R.C.C Frame Structure

Steel Structures

Precast Structures

Water Retaining Structures

Ground Storage Tanks Elevated Water Tanks

Storage Structures, silos


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1. Masonry Structures

Foundation Design

Pillars / Walls Design

Slab Design

Beams Design


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Masonry/Spread Foundation

LOAD CALCULATION

SELF WEIGHTOF WALL(9,13)

SLAB

SELF WEIGHT (5, 6, 7)

FLOOR FINISH (BB 3 + PCC 2)

CEILING FINISH (1/2)

LIVE LOAD (30 psf TO SAY 100psf) ref. ubc

WIDTH = TOTAL LOAD/BEARING CAPACITY


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Walls / Pillars Design

SAFE LOAD CARRYING CAPACITY 1:3 c/s 125 Psi

1:4 c/s 100 Psi

1:6 c/s 70 Psi

Check the pillar for stress Stress =load / unit area

Check the walls for slenderness


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Slab Design

One Way Slab Minimum thickness

Simply supported =l/20

One end cont. =L/24

Both end cont. =L/28

Cantilever =L/10 (Table 8.1 winter Nilson) Moment= WL^2/8, WL^2/10, WL^2/12

Two Way Slab Three variables

Load (DL, & LL) :for LL ref ubc/ibc/any design hand book SPANS (SHORT & LONG)

END CONDTION (CONT., DISCONTINUOUS)(coefficents for +ve & -ve moments Table 8.3 winter Nilson)


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Beams Design

Rectangular beam, T beam & L beam

Loading

Bending moment

Shear force

Design of concrete section (12x18)

Flexure reinforcement (6#6 bars)

Shear reinforcement (#3rings @6c/c) Beams Containing compression reinforcement


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2. R.C.C Frame Structure

MODELING OF STRUCTURE

FOUNDATION DESIGN

COLUMN DESIGN

SLAB DESIGN

BEAM DESIGN


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Modeling Of Frame Structure

SAP

ETABS

STAAD

PCA SOFTWARES INPUT

GEOMETRY

ASSUMED SECTIONS ANTICIATED LOADING

DL, LL, SEISMIC, WIND


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Foundations

Type of Foundations

1. Spread footing isolated

2. Strap footing Isolated footing combined with beam

3. Combined /strip footing

4. Mat or Raft footing5. Pile foundations


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Foundation Design

Geotechnical design Proportioning the footing w.r.t geo-tech.report Area of footing = D+L / bearing capacity

(concentric Loading)

A = (D+L+W) / 1.33 X BC EQ-14.2 WINTE NILSON

QMAX,MIN = P/A + M/Z EQ-14.3

Structural design1. Adequate section

Two Way Or Punching Shear

One Way Or Beam Shear2. Reinforcement

Reinforcement is provided against moment


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Column Design

1. Axially Loaded columns Stress = P/A

2. Compression Plus Uni-axial bending Stress = P/A + MX/ZX

3. Compression Plus Bi-axial bending Stress = P/A + MX/ZX + MY/ZY

Basic Structural Design Concepts

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