تصميم المنشآت الخرسانية المسلحة

DESIGN OF REINFORCED

CONCRETE STRUCTURES

محمد إبراهيم الرجوب. د

Design Methods

Building Codes

Loads

Components of Concrete

Properties of Concrete

INTRODUCTION

INTRODUCTION

Materials

Concrete = FA + CA + cement +Water +Add.

= Agg. + Paste

Reinforced Concrete = Concrete + Steel

Why Steel is used??

Material Properties

Properties of Concrete

Ex. RC BEAMS

RC Beams

Water / Cement Ratio

w/c = 0.2 – 0.3 ???

w/c = 0.35 – 0.45 ???

Concrete Compressive strength

Typical Stress-strain curve of concrete

Curves of HSC vs NSC

Steel

Typical Stress-strain curve of steel

Prestressing

Steel:

stress-

strain

curve

Ec (SI Units)

Ec: (NWC and LWC)

Example USC Units

Tensile strength

Ft = (0.05 – 0.1) f’c

Types: 1. Modulus of rupture. 2. Split tensile strength

3. Double Punching . 4. Direct Tensile strength.

Modulus of Rupture (SI units)

SI units USCU

Tensile strength

Ft = (0.05 – 0.1) f’c

Types: 1. Modulus of rupture. 2. Split tensile strength

3. Double Punching . 4. Direct Tensile strength.

SI Units USCU

Modulus of

Rupture

Fr =

Split Tensile

Strength

Concrete Shrinkage

Effect of curing on Concrete Shrinkage

Concrete Creep

LOADS

DEAD LOADS

Dead loads are weights of material, equipment, or

components that are relatively constant throughout

the structure's life.

Permanent loads includes dead loads and forces set

up by irreversible changes in a structure's constraints

such as loads due to settlement.

Live loads: Sometimes referred to as probabilistic loads

include all the forces that are variable within the object's

normal operation cycle not including construction or

environmental loads.

Live loads (roof) produced (1) during maintenance by

workers, equipment and materials; and (2) during the life

of the structure by movable objects such as planters and

by people.

Live loads

Include:

People

Books

Equipment

LRFD or LFD General Form

ACI Partial Safety Factors

AISC LRFD Partial Safety Factors

Codes

Several Codes have recently been

revised to incorporate Probabilistic

design Such as

- ACI 318 -08 Building Code

- AISC LRFD Steel Manual

- BS 8110 -02

Loads (See ASCE Load ..)

Typical Dead Loads for common

building materials

ASCE Loading

Typical Live loads

ACI & AISC Load Factors

Load factors and Combinations

Example: Load Combinations (USCU)

Example 2:

Solution

LECTURE _2_

STRUCTURAL SYSTEM OVERVIEW

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One-Way Joist Floor System

2D lateral frames

Floor joists, type

Rib (joist) slab : (One-way bending)

2D gravity or lateral

frames

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One-Way Joist Floor System

Lateral space frame

Floor joists, type

Rib (joist) slab with beams: (One-way bending)

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One-Way Joist Floor System

• 2’ or 3’ cc. – Joists

• 4’ or 6’ cc. – Skip joists

• 5’ or 6’ cc – Wide-module joists

Top of Slab

1:12 Slope, type

8-24” for 30” Modules

16-24” for 53” Modules

14-24” for 66” Modules .

Width varies

4”, 6” or larger

(100-150 mm)

Typical Joist

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One-Way Joist Floor System

Advantages:

Longer spans with heavy loads

Reduced dead load due to voids

Electrical, mechanical etc. can be placed between voids

Good vibration resistance

Typical Applications:

Medium-to-long spans with heavy loading

For 30” modules, 35’ – 40’ spans

For 53” & 66” modules, 35’ – 50’ spans

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Two-Way Joist Floor System

2D lateral frames

Waffle pans, type

Waffle slab : (Two-way bending)

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Two-Way Joist Floor System

Advantages:

Longer spans with heavy loads

Reduced dead load due to voids

Electrical, mechanical etc. can be placed in voids

Good vibration resistance

Attractive Ceiling

Typical Applications:

Long spans with heavy loading

For 3’, 4’, and 5’ modules, 40’ – 50’ spans and beyond

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B. Lateral Load Systems

Frame Overview

Flat plate (& slab)-column (w/ and w/o drop panels and/or capitals) frame systems

Beam-column frame systems

Shear wall systems (building frame and bearing wall)

Dual systems (frames and shear walls)

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Frame: Coplanar system of beam (or slab) and

column elements dominated by flexural deformation

Planar (2D) Space (3D)

CVEN 444 Structural Concrete Design

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Basic Behavior

Gravity Load Lateral Loading

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Frame Advantages

Optimum use of floor space, ie. optimal for office buildings,

retail, parking structures where open space is required.

Relatively simple and experienced construction process

Generally economical for low-to mid-rise construction (less than

about 20 stories)

In Houston, most frames are made of reinforced concrete.

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Frame Disadvantages

Generally, frames are flexible structures and lateral

deflections generally control the design process for buildings

with greater than about 4 stories. Note that concrete frames

are about 8 times stiffer than steel frames of the same

strength.

Span lengths are limited when using normal reinforced

concrete (generally less than about 40 ft, but up to about 50

ft). Span lengths can be increased by using pre-stressed

concrete.

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Frame Lateral Load Systems

Flat plate-column frame:

Plan Elevation

Effective slab

width

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Frame Lateral Load Systems

Beam-column frame:

Elevation

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Frame Lateral Load Systems

For relatively square plans, diaphragms are generally considered rigid

Space frame with

square plan

Deformed shape has constant lateral

displacement - No diaphragm flexibility,

ie. lateral load distributes to frame

proportional to frame stiffness

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Shear Wall Lateral Load Systems

Shear wall

Elevation

Edge column

Interior gravity

frames

Shear deformations generally

govern

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Shear Wall Lateral Load Systems

Gravity frames

Shear walls

Coupling beams

Elevator shaft configuration

Hole

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Dual Lateral Load Systems

Lateral frames – 25%

of lateral load,

minimum

Shear walls

Wall-Frame Dual System:

Hole

Analysis Versus design

Analysis Versus design

AISC Loads