Reinforced Concrete Buildings: Behavior and Design
5/5
()
About this ebook
Read more from Ahmad A. Hamid
Introduction to Design of Building Structures Rating: 4 out of 5 stars4/5Design and Retrofit of Building Envelope Rating: 5 out of 5 stars5/5
Related to Reinforced Concrete Buildings
Related ebooks
Reinforced Concrete Design Rating: 0 out of 5 stars0 ratingsStructural Concrete: Materials; Mix Design; Plain, Reinforced and Prestressed Concrete; Design Tables Rating: 4 out of 5 stars4/5Structural Concrete: The Commonwealth and International Library: Structures and Solid Body Mechanics Division Rating: 0 out of 5 stars0 ratingsPrinciples of Reinforced Concrete Rating: 5 out of 5 stars5/5Earthquake-Resistant Structures: Design, Build, and Retrofit Rating: 4 out of 5 stars4/5Rehabilitation of Concrete Structures with Fiber-Reinforced Polymer Rating: 0 out of 5 stars0 ratingsAnalysis and Design of Prestressed Concrete Rating: 3 out of 5 stars3/5Concrete Structures: Repair, Rehabilitation and Strengthening Rating: 0 out of 5 stars0 ratingsMinimum Reinforcement in Concrete Members Rating: 3 out of 5 stars3/5Design of Steel-Concrete Composite Structures Using High-Strength Materials Rating: 0 out of 5 stars0 ratingsPlastic Analysis and Design of Steel Structures Rating: 4 out of 5 stars4/5Structural Design: A Practical Guide for Architects Rating: 5 out of 5 stars5/5Structures Failures Reasons and Mitigation Rating: 0 out of 5 stars0 ratingsReinforced Concrete Grade Beams, Piles & Caissons: A Practical Guide for Hillside Construction Rating: 0 out of 5 stars0 ratingsDesign and Analysis of Tall and Complex Structures Rating: 5 out of 5 stars5/5Civil Engineer's Reference Book Rating: 4 out of 5 stars4/5Corrosion and its Consequences for Reinforced Concrete Structures Rating: 0 out of 5 stars0 ratingsMethod of Protecting Steel Reinforcement Rating: 0 out of 5 stars0 ratingsStability of Structures: Principles and Applications Rating: 4 out of 5 stars4/5Foundation Design: Theory and Practice Rating: 5 out of 5 stars5/5Structural Design of Buildings Rating: 0 out of 5 stars0 ratingsBridge Engineering: Classifications, Design Loading, and Analysis Methods Rating: 4 out of 5 stars4/5Design of Steel Structures: Materials, Connections, and Components Rating: 0 out of 5 stars0 ratingsStructural Steel Design to Eurocode 3 and AISC Specifications Rating: 0 out of 5 stars0 ratingsElements of Loadbearing Brickwork: International Series of Monographs in Civil Engineering Rating: 5 out of 5 stars5/5Concrete and Masonry Movements Rating: 5 out of 5 stars5/5A State-of-the-Art Guide for Post-Installed Reinforcement Rating: 0 out of 5 stars0 ratingsCorrosion of Steel in Concrete Rating: 0 out of 5 stars0 ratings
Architecture For You
Feng Shui Modern Rating: 5 out of 5 stars5/5Lies Across America: What Our Historic Sites Get Wrong Rating: 5 out of 5 stars5/5How to Fix Absolutely Anything: A Homeowner's Guide Rating: 4 out of 5 stars4/5The New Bohemians Handbook: Come Home to Good Vibes Rating: 4 out of 5 stars4/5Cozy Minimalist Home: More Style, Less Stuff Rating: 3 out of 5 stars3/5Become An Exceptional Designer: Effective Colour Selection For You And Your Client Rating: 3 out of 5 stars3/5Architectural Digest at 100: A Century of Style Rating: 5 out of 5 stars5/5Walkable City: How Downtown Can Save America, One Step at a Time Rating: 4 out of 5 stars4/5How Paris Became Paris: The Invention of the Modern City Rating: 4 out of 5 stars4/5Building Natural Ponds: Create a Clean, Algae-free Pond without Pumps, Filters, or Chemicals Rating: 4 out of 5 stars4/5Architecture 101: From Frank Gehry to Ziggurats, an Essential Guide to Building Styles and Materials Rating: 4 out of 5 stars4/5Brunelleschi's Dome: How a Renaissance Genius Reinvented Architecture Rating: 4 out of 5 stars4/5Flatland Rating: 4 out of 5 stars4/5How to Build Shipping Container Homes With Plans Rating: 3 out of 5 stars3/5Martha Stewart's Organizing: The Manual for Bringing Order to Your Life, Home & Routines Rating: 4 out of 5 stars4/5The Nesting Place: It Doesn't Have to Be Perfect to Be Beautiful Rating: 4 out of 5 stars4/5Live Beautiful Rating: 4 out of 5 stars4/5Welcome Home: A Cozy Minimalist Guide to Decorating and Hosting All Year Round Rating: 0 out of 5 stars0 ratingsAtomic Ranch: Design Ideas for Stylish Ranch Homes Rating: 4 out of 5 stars4/5Disney's Land: Walt Disney and the Invention of the Amusement Park That Changed the World Rating: 4 out of 5 stars4/5The Year-Round Solar Greenhouse: How to Design and Build a Net-Zero Energy Greenhouse Rating: 5 out of 5 stars5/5Get Your House Right: Architectural Elements to Use & Avoid Rating: 4 out of 5 stars4/5Solar Power Demystified: The Beginners Guide To Solar Power, Energy Independence And Lower Bills Rating: 5 out of 5 stars5/5The Little Book of Living Small Rating: 5 out of 5 stars5/5Making Midcentury Modern Rating: 4 out of 5 stars4/5Down to Earth: Laid-back Interiors for Modern Living Rating: 4 out of 5 stars4/5A Pattern Book of New Orleans Architecture Rating: 0 out of 5 stars0 ratingsMeet Me by the Fountain: An Inside History of the Mall Rating: 3 out of 5 stars3/5
Related categories
Reviews for Reinforced Concrete Buildings
1 rating0 reviews
Book preview
Reinforced Concrete Buildings - Ahmad A. Hamid
Wall
1
INTRODUCTION
1.1 Advantages and Characteristics of Reinforced Concrete
Reinforced concrete is a composite material made of concrete and steel bars, see Figure 1.1. It merges the advantages of concrete (form, stiffness and durability) with those of steel bars (high tensile strength and ductiltiy) into a single material with excellent physical and mechanical properties. Longitudinal steel in form of reinforcing bars is placed on the tension side of the member to carry flexural tensile stress from bending (in case of beams) or from combined axial laod and bending (in case of columns). Transverse steel in form of stirrups (in beams) or ties (in columns) serves to carry diagonal tension from shear forces.
Figure 1.1 Reinforced concrete as a composite material.
1.2 Composite Action
For composite action to work, adequate load transfer between the steel bars and the surrounding concrete has to be ensured via adequate development length of the steel bars. As such, the steel bar will develop its full tension capacity (yield strength times the bar cross sectional area) before it pullls out of the concrete. That is why reinforcing bars are deformed (Figure 1.2-a) to have adequate load transfer ability. Development length of straight bars ranges from 40-60 times the bar diameter. Using a 90 dgrees or 180 degrees hook (Figure 1.2-b) at the end of the bar can reduce the development length by roughly 50%
Figure 1.2 Deformed reinforcing steel bars.
1.3 Types of Reinforced Concrete Buildings
The most common types of low-rise and mid-rise (up to 20 stories) reinforced concrete buildings are:
1- Frame buildings (Figure 1.3)
2- Wall buildings (Figure 1.4)
3- Hybrid frame-wall buildings (Figure 1.5)
Figure 1.3 RC Frame building.
Figure 1.4 RC wall building
Figure 1.5 Hybrid frame-wall building
1.4 Floor Slabs
The choice of the type of floor slabs for buildings depends on many factors such as the material used for the load resisting system (steel, concrete, masonry, timber), vertical load intensity, span and panel aspect ratio. The thickness of the floor slab is a critical parameter that affect the weight and cost of the structure. This is particularly true for highrise buildings. For example, reducing the slab thickness from say 6.5 in. to 6.0 in. for 5000 sq. ft building with 30 stories will save 0.5 x 5000 x 30 = 75,000 cu ft of concrete. This reduction in weight will reduce the column loads and foundation loads. It will also reduce inertia forces from earthquakes.
Concrete is an excellent material for floor construction because of its high stiffness, fireproofing and good sound insulation properties. The selection of the floor system and the slab thickness is a key design parameter. The selection of the floor slab system depends on:
1- Clear span between columns or shear walls
2- Aspect ratio of the panel
3- Stiffness of boundary beams, if any
4- Load intensity
5- Function of the building
Figure 1.6 shows different types of floor slabs depending on span.
Figure 1.6 Floor slabs.
1.5 Structural Safety and Reliability
There are three main reasons why safety factors should be incorporated in structural design:
1- Variability in resistance
. Variability of material strength (Figure 1.7-a)
. Variability of dimensions and locations of members
. Simplifying assumptions in design
2- Variability in loading, see Figure 1.7-b
3- Consequences of failure
. Potential loss of life
. Cost of replacement
. Cost of lost time and revenue
Figure 1.7 Examples of variability in strength and loads.
Figure 1.8 Safety margins.
Safety factors are based on a probabilistic approach. Safe and unsafe combinations of loading are shown in Figure 1.8. The term Y=R-S in Figure 1.8 is called safety margin. In this figure the shaded area represents the probability of failure. Because of economical reasons there will be always a very small probability of failure (typically 5%).
Reliability is the ability of a system or component to perform its required functions under stated conditions for a specified period of time. Reliability presents ways in which products fail, the effects of failure and aspects of design, manufacture, maintenance and use which affect the likelihood of failure.
Figure 1.8 shows the pressures that lead to the overall perception of risk. Reliability engineering has developed in response to the need to control these risks.
Figure 1.8 Perceived risk.
1.6 Structural Analysis
The main objective of the analysis is to predict the response of buildings to loading. This can be measured by the resulting internal forces (axial force, shear force and bending moment) and deformations (deflections and rotations). Reinforced concrete frame structures are typically statically indeterminate. The following methods are used:
1- Approximate methods such as the portal frame method and the cantilever method
2- Classical methods for hand calculations such as the Moment Distribution Method
3- Stiffness method for computer applications. Many powerful commercial software codes are available such as STAAD and SAP.
4- ACI 318 shear and moment coefficients for continuous beams and one-way slabs.
1.6.1 Effect of Continuity
For horizontal spanning from point A to B the location of the supports and consequently span/continuty effect has a dramatic influence on the demand/internal forces and deflections. As shown in Fig. 1.9, for a simly supported beam AB the maximum moment at mid-span is wL²/8. If the support move to the inside, negative at the supports and positive moment at mid span develpe with values less than wL²/8. As the supports move close to the middle negative moment equal to wL²/8 develop. For a = 0.2L, equal negative and positive moments (0.02 wL²) develop leading to an optimum design.
Figure 1.9 Effect of continuity on beam moments.
1.6.2 Effect of Boundary Conditions
As shown in Fig. 1.10, the shape and maximum moments are affected by the boundary conditions at the supports. For a simply supported beam maximum moment of wL²/8 occurs at mid-span with maximum rotation θ= wL³/24 at the supports. For a fixed-fixed beam negative moment of wL²/12 develops at the supports with less positive moment of wL²/24 (compared to the simply supported case) at mid-span. In this case rotation is zero at the supports and maximum deflection is less comapred to the simply supported case. Por partil constraints at the supports the negative moment at the supports will be less than wL²/24 whereas the postive moment at mid-span will be greater than wL²/24.
Figure 1.10 Effect of boundary conditions on beam moments.
1.6.3 Shear and Moment Cofficients for Continuious Beams and One-Way Slabs
Figure 1.11 shows ACI 318 shear and moment coefficients for continuous beams where moment is Cm wL² and shear is Cv wL/2. It is assumed that live loads are not greater than three times the dead loads and therefore pattern loading is ignored (for LL/DL ratio less than or equal to 3.0) and the total full dead and live loads are considered.
1.6.4 Pattern Loading
For heavy live loads that are more than three times the dead loads the effect of pattern loading should be accounted for. Ignoring the effect of pattern loading in this case would result in an underestimation of maximum moments and shear forces at the member ends. This effect will be more significant in case of long catilevers and dissimilar spans. Some computer codes/software consider the effect of pattern loading in the analysis of frames under vertical loads.
Figure 1.11 Shear and moment coefficients for continuous beams.
1.7 Structural Design
1.7.1 Objectives of Structural Design
The main objectives/goals of structural design are:
1- Adequate performance under service loads. This is referred to as Serviceabilty limit state
and it concerns with deflection limits, vibration control and crack control.
2- Adequate factor of safety against failure/collapse in case of overloading.
3- Economy (initial and long-term).
1.7.2 Design Loads
Gravity Loads (dead and live loads) for beams and columns can be calculated using the concept of tributary area, see Figure 1.12. Note that the loads on beams are localized whereas the axial loads on columns are accumulative