Higher Studies

Diploma, Master of Science in Structural EngineeringFeb. 2017 – May 2017

Assc. Prof. Dr. Nasser. El-Shafey

Course teaching topic by - Dr. Nasser. El-Shafey:

1. Types of applied vertical and lateral Loads on reinforced concrete

buildings.

2. Introductions to Earthquake ( Theories of how earthquake formed

,classifications of earthquake, earth tectonic plates, faults and ground

movements, methods of measuring earthquake, earthquake waves,

history of some severe earthquakes occurs in the history)

3. Structural systems used to resist earthquakes (moment resisting

frames, shear wall, cores,…)

4. Structural damages due to earthquake.

5. Simplified model response spectrum method ( lateral force

distributions on building, center of mass & center of rigidity,

symmetrical & unsymmetrical shear walls or cores, symmetrical &

unsymmetrical rigid frames, torsion effect, drift of structures due to

seismic)

6. Distribution of wind loads on R.C. buildings.

7. Coupled shear walls (behavior, distribution of lateral loads, stresses

on each wall )

8. Distributions of lateral loads on building resisting by both shear

wall & rigid frames.

At the end of this coursethe attendees should be able to:

1. Chose suitable structural systems to resist earthquakes (moment resisting

frames, shear wall, tube in tube,…)

2. Define different structural damages due to earthquake .

3. Distribute lateral forces (seismic) using response spectrum method for

buildings resisted by either symmetrical or unsymmetrical shear walls,

rigid frames, or both and coupled shear walls including torsion effect, drift

of structures )

4. Calculate wind loads and its distributions on buildings.

5- Check (sliding, overturning and drift) for the concrete buildings.

6- Complete calculations for Design and detailing of different structural

resisting concrete elements (shear walls, rigid frames and coupled shear

walls to resist lateral loads).

Method of Assessment Percentage of total

Written examination (closed Book exam) 70%

Assignments (15%) , quizzes(15%) 30%

Knowledge and Understanding

Design straining actions for different structural elements.

Behavior of concrete structural elements.

Types of damages and cracking in different structural

concrete elements.

Design of different concrete sections, columns and walls

under different straining actions.

List of References: 1. Lecture notes .

2. “Earthquake damage to structures ”, By : Mark Yashinsky ( Structural

Engineering handbook).

3. “Seismic design of building to Euro code 8 ” By Ahmed El-Ghazouli

Local books of Concrete structures.

4. “Some concepts in Earthquake Behavior of Buildings” C.V.R Murty,

Rupen Goswaml

5. The Egyptian code of practice for design and construction of

concrete structure.

6. The Egyptian code of practice for load calculation.

Loads on buildings

All structural elements must be designed for all loads anticipated to act during

the life span of such elements. These loads should not cause the structural

elements to fail or deflect excessively under working conditions.

Main vertical load

Dead loads (D.L)

•Weight of all permanent construction.

• Constant magnitude and fixed location.

Examples: Weight of (Walls, Floors, Roofs, Ceilings, Stairways, Partitions,

Fixed Service Equipment )

Live Loads (L.L) according to building uses (2 : 5 KN/m2).

Wall Loads according to own weight of wall intensity (15 : 18 KN/m3).

These types of loads consider as a main loads for any types of buildings

Secondary LoadWind loads.

The wind load is a lateral load produced by wind pressure. It is a type of dynamic load

that is considered static to simplify analysis. The magnitude of this force depends on the

shape of the building, its height, the velocity of the wind in which the building exists.

Seismic loads (Earthquakes loads).

The earthquake load is a lateral load caused by ground motions resulting from

earthquakes. The magnitude of such a load depends on the mass of the structure and the

acceleration caused by the earthquake.

Earth pressure.water pressure loads.Impact loads.

These loads consider secondary load for the ordinary low rise buildings, but for high rise buildings or special buildings, these loads consider main loads

Lateral Load

Wind Loads Earthquakes loads

Wind or

earthquakes

Vertical deflection (sag)

Dead, Live, etc.

Lateral deflection (sway)

Performance-Based Design:

Control displacements within acceptable

limits during service loading, factored

loaded, and varying intensities of

environmental loading

Loads and load combinationsFor members subject to live loads:U = 1.4 D + 1.6 L Where,D = Dead Loads L= Live Loads

- For members subject to either wind load, W or seismic load, S the ultimate load shall be taken equal to the greater value obtained from the following two equations:

U = 0.8 (1.4 D + 1.6 L + 1.6 W)

U = 1.12 D + a L + S Where,S = Ultimate seismic loads.

a = A factor that accounts for the effects of the sustained live loads on the structure during seismic activities.

a = 1/4; for residential buildings

a = 1/2; for public buildings including, schools, hospitals, garages, theatre halls, commercial and office buildings

a = 1 ; for structures subject to loads acting for a long duration of time which include but are not limited to, silos, bins, water tanks, libraries, storage buildings

Internal Forces

• The internal strength of the entire structure must be = or > the total forces applied on the building

• The ability to withstand all forces depends on the structural component’s dimensions and the solidity and elasticity of the material.

• Internal forces :

• Compressive and Tensile ForcesAccording to Newton’s Third Law, forces

act in pairs. In structural terms, tensile force pulls a structural element apart while compressive force compresses it.

• TorqueIf opposing forces are applied at different

points, a structural element may become twisted. Internal forces in a structural element

Egyptian Code of practice

The Egyptian Code of practice require that in addition to the vertical

loads, buildings designed to resist lateral loads (wind or earthquake

loads).

Lateral loads may or may not affect the design of structures according

to buildings heights.

In working stress design method, if seismic or wind loads are

considered, then the allowable stresses may be increased by 15%.

Wind loads and seismic loads should not be combined.(only, the

higher of the two load case is to be considered)

What is a High-Rise Building ??

A building whose height creates different conditions in the design,construction, use than those that exist in common buildings of a certainregion and period.”

• “A Structure because of its height, is affected by lateral forces due to windor earthquake actions to an extent that they play an important role in thestructural design.”

■ Why Tall Building (Advantage)??

• Business activities need to be as close to each other.

• It forms prestige symbols, distinctive land marks, hotels and commercial city centers.• High cost of land and limited space.

■ Disadvantage of Tall Building ??

• Putting intense pressure on the available land space .

• Increase the risk, safety hazards and constitute an easy target in case of war or terrorism.

STAGES OF HIGH RISE building DESIGN

Concept Design

MEP

Preliminary Structural Design Based on

Vertical Loads Plus an allowance for Lateral

Loads Based mainly on EXPERIENCE

Structural

■ Design Process

Final Design

Working Design

Accurate Modeling and Analysis Based on

Final Layout and All Possible Loads and

Development of Final LAYOUT DRAWINGS

Final Design Calculations and the

Development of Working Drawings by

Cooperation with CONTRACTORS

Architectural

Lateral Load Resisting Elements

• Vertical Elements:

• Moment-Resisting Frames.

• Walls – Bearing walls / Shear Walls.

• “Dual” System (Frame + Wall).

• Tube System.

• Tube in Tube system

• Bundled-Tube System.

• Floor / Diaphragm.

• Foundation – various types

Moment-resisting frames are structures having the traditional beam-

column framing, carrying gravity loads that are imposed on the floor

system.

The floors also function as horizontal diaphragm elements that

transfer lateral forces to the girders and columns. In addition, the

girders resist high moments and shears at the ends of their lengths,

which are, in turn, transferred to the column system. As a result,

columns and beams can become quite large.

Moment-Resisting Frames

■ Moments resisting frames

Consist of beams and

columns in which bending of

these members provides the

resistance to lateral forces.

Basic Behavior

Frame Lateral Load SystemsFlat plate-column frame:

Beam-column frame:

Elevation

Shear Wall Lateral Load Systems

Shear wall

Elevation

Edge column

Interior gravity frames

Shear deformations

generally govern

The elevator shafts, stairwells necessary for access in a high rise and must be protected by fire walls, as demanded by fire safety regulation.

Shear wall with its highly resistance to shear stress, are highly suitable for assuming the shear forces that arise through lateral loads.

Dual Lateral Load Systems

Type 3 – Cumulative Drift

Flexural deflection profile

Type 2 Core Only

Shear deflection profile

Type 1 Frame Only

Combined deflection profile

Type 3

+ =

The total deflection of the interacting shear wall and rigid frame systems is obtained by superimposing the individual models of deformation

Core Structure System

Tube-in-tube system

The framed-tube structure has its

columns closely spaced around

the perimeter of the building,

rather than scattered throughout

the footprint, while stiff spandrel

beams connect these columns at every floor level

Framed-tube system

• The lateral resistant of the framed-tube structures is provided by very stiff moment-resistant frames that form a “tube” around the perimeter of the building.

• The basic inefficiency of the frame system for reinforced concrete buildings of more than 15 stories resulted in member proportions of prohibitive size and structural material cost premium, and thus such system were economically not viable.

• The frames consist of (2-4m) between centers, joined by deep spandrel girders.

• Gravity loading is shared between the tube and interior column or walls.

Dewitt chestnut

Braced-tube systemBundled-tube system

The concept allows for wider column spacing in the tubular walls than would be possible with only the exterior frame tube form.The spacing which make it possible to place interior frame lines without seriously compromising interior space planning.

Burj Khalifa, Dubai.

Sears Tower, Chicago.

BUNDLED TUBE SYSTEM

High Rise Example

1.Sears Tower

Nine Bundled Tubes,

each 25 m wide with no columns

between core and perimeter.

Location: Chicago

No of Stories: 108

Construction Year: 1974

Height: 442 m

Outrigger-braced system

■Tallest twenty high rise in the world

CHALLENGES IN THE DESIGN OF HIGH RISE BUILDINGS

10/28/2009

■ High Rise Example (Burj Dubai)

This is the tallest Man Made Building in the world with a predicted height of 818m.

■ High Rise Example (World Trade Center)

534 meter to tower

top 610 meter to pyramid

top 670 meter to comm. tower

Structural Systems for Tall Buildings

Burj khalifaMakkah Clock Royal Tower

Taipei 101

Petronas Towers International Commerce Center

Kingkey Finance

Tower

Wills Tower Nanjing

Greenland

Financial

Center

■Construction Challenge Modern Shuttering

■Design Challenge

Ductile Detailing

Using Advanced Control Techniques