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Structural design of G+7 building using solid and ribbed slab

Prepared byMekbib EsundaleShemeles MekonenSimon KetemaTeklemaryam MamoTewodros Mekonen

Advisor Ato Abreham E.–

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To make us familiar with the basic design steps of structural systems

To have general over view of solid slab & ribbed slab floor system

To provide appropriate– shape, – dimension – detail of reinforcement

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Design methodology

Limit sate design Method Considering– Safety of the structure and its content– Safety of People– Fitness for purpose

Serviceability Limit State ConsideringDeformationDisplacementVibration and Cracking

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Content

Introduction Design of roof structures Shemeles Design of slab Design of stair Teklemariyam Earth quake analysis Mekbib Design of beams and columns Tewodros Design of foundation Simon

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Introduction

Structural design is• Process of determining the dimensions

and lay out of the load resisting components

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Design data and material properties

Concrete grade C-25 Class I Reinforcement Steel f=300 Mpa Roof truss and purlin Zigba

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Key characteristics

Physical characteristics give reinforced concrete its special properties:The coefficient of thermal expansion of concrete is similar to that of steel, eliminating large internal stresses due to differences in thermal expansion or contraction

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1. Roof analysis and design

LOADING– Dead load – Live load

• Concentrated • Distributed

– Wind load• External wind pressure• Internal wind pressure• Net wind pressure9

Roof analysis and design Cont’d……

Wind load analysisTwo methods

– Quasi static method– Dynamic analysis

According to [EBCS-1,1995 section 3.9.3]– Our building can be analyzed using Quasi

static analysis

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Roof analysis and design Cont’d……

Design of purlinLoad combination

We selected Zigba tree for the truss systemTaking maximum actions Cheek for

– Deflection and – Shear

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Roof analysis and design Cont’d…..

Stress analysis of trussTruss is a structure with straight pieces forming triangles to support a loadTruss must be safe from

– Failure of members– Failure of truss as a whole– Excessive deflection

Cheek for section capacity of tension and compression 12

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2.Slab design

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Solid slab design

1. Depth determination

d≥(0.4+0.6fyk/400)Le/a

2. Design load calculation

Based on the limit state design method

Pd= 1.3DL+1.6LL

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3. Analysis of individual panels The analysis of support and field moments Mi = α iPdLx2

4. Moment adjustmentSupport adjustment ∆M<20%

∆M≥20% Span adjustment

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5.Check depth for flexure

6.Reinforcement design for flexure

Using design chart

7.Load transfer to frames

Load transferred As shear. The shear is calculated as:

Vx = ßvx* Pd*Lx

Vy = ßvy* Pd*Ly17

Two type 1.Precast

pre-cast joist pre-cast of hollow

block(HCB)

2.Cast-in-place pre-cast of HCB

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Size requirements

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Procedure • Depth determination for deflection.• Design load calculations.• Moment envelop to maximize support

and span• Check depth for maximum moment.• Design the Rib’s using moment

envelop.

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Design method Stair is designed like one-way

solid slabs Checked for shear and moment

Design steps Depth determination for deflection Determination of design load Moment calculation Check depth for maximum moment Reinforcement provision Load transfer to beam21

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3.3.Earthquake Analysis

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3.Design procedure for simple Earthquake Analysis

Check the building regularity criteria

1.Criteria for regularity in plan.

2. Criteria for regularity in elevation.

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Design procedure for simple Earthquake Analysis

Calculation of Lateral loads by Earthquake and determination of base shear

Fb = Sd (T1) W

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Design procedure for simple Earthquake Analysis

Determination of Center of Mass

Center of mass (Xm, Ym): it is a point on a floor level where the whole floor mass and its inertial effects can be replaced using a lumped equivalent mass.

– Xm = (∑wiXi)/(∑wi)

– Ym = (∑wiYi)/(∑wi)

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Design procedure for simple Earthquake Analysis

uncertainty in the location of masses special variation of the seismic variation of the seismic motion.

center of mass at each floor i displaced from its normal location in each directions by additional accidental eccentricities

eu= 0.05Li

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4.Design of Beam and column

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Design of Beam

Beams are flexural members which are used to transfer the loads from slab to columns

Design steps design for flexure Provision of longitudinal reinforcement using design chart design for shear

Provision of lateral reinforcement

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Column design

Design procedure

Classify the frame as sway or non-sway

Substitute the beams and columns by one substitute frame

substitute frameActual frame31

Design procedure cont.

Calculate the stiffness coefficients of the substitute fame

The effective length of the substitute frame is computed for each story Checking for slenderness ratio

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Design procedure cont.

Check consideration for second order effect Design eccentricity calculation

Design Column under biaxial bending using interaction chart

Read

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5.Foundation

Foundations transfer the load coming from the superstructure to the soil or bedrock.

Modern foundation types are shallow and deep foundations.

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Foundation Design Cont’d…

We have used EBCS 2 & 7, 1995 as our standard code for design.

Punching shear and wide beam shear are used to control the depth and to check safety against diagonal tension.

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Foundation Design Cont’d…….Punching &wide beam shear

Punching design considers the comparison of Column reaction Vp with punching shear resistance given by Vrd=0.25fctdK1K2Ud.

Wide beam shear design compares the acting shear Va with shear resistance given by Vw=0.25fctdK1K2bwd.

Punching reinforcement37

Foundation Design Cont’d…..

Reinforcement Flexural reinforcement is provided using the

critical design moment Where the Moment is subject to both X and Y

direction eccentricities.

AutoCAD Drawing

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