Practical Design of Reinforced Concrete Buildings

Syed Mehdi Ashraf

• Publisher: CRC Press
• Year: 2017
• eBook ISBN: 9781351649797
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

This book will provide comprehensive, practical knowledge for the design of reinforced concrete buildings. The approach will be unique as it will focus primarily on the design of various structures and structural elements as done in design offices with an emphasis on compliance with the relevant codes. It will give an overview of the integrated design of buildings and explain the design of various elements such as slabs, beams, columns, walls, and footings. It will be written in easy-to-use format and refer to all the latest relevant American codes of practice (IBC and ASCE) at every stage. The book will compel users to think critically to enhance their intuitive design capabilities.

Section II

Design

6
Slabs

6.1Introduction

Introduction to the concepts of slabs, their behavior, and bending theory and shear force theory is provided in Chapter 1. Sectional strength of the slabs is discussed in Chapter 4. This chapter deals with the code specifications and the design methodology for one-way and two-way slabs. Several design examples are provided that demonstrate the code specifications for design and sectional strength of the slabs. In the examples, the serviceability requirements of the code are also checked.

6.2One-Way Slabs With Beams

Slabs are classified as one-way slabs when their aspect ratio is 2 or greater. The length of the slab is at least twice the width.

6.2.1Simply Supported Slab

Simply supported one-way slabs would bend (sag) in the shorter direction due to its geometry. Hence, the main reinforcement to resist the bending moment would be placed in the shorter direction. Since the slab is simply supported, it has only one span and is required to have two beams along the long edges to support the slab (Figure 6.1). Unless the two short edges of the slab are loaded (e.g., with a masonry wall above the slab along its short edges), beams are not required along the short edges. If the columns are short columns, do not require bracing and are not resisting any lateral loads, then also beams are not required along short edges.

FIGURE 6.1 One-way slab (simply supported slab).

6.2.2Continuous Slab

Continuous one-way slabs have two or more spans (Figure 6.2). If the slabs have uniform spans and loads, then the spans would be subject to sagging moment (assigned positive sign throughout this book) at the span and hogging moment (assigned negative sign throughout this book) at the support. However, depending upon the spans and loading, hogging moment could occur at the span too.

FIGURE 6.2 One-way continuous slab.

6.2.3Materials

The properties of concrete and steel, detailing of the embedments, and connections to other members are discussed in Sections 5.9, 5.10, 5.12, and 5.13 of this book, respectively.

6.2.4Minimum Thickness of Slab

Though the thickness of the slab is selected at the beginning of the design, deflections are calculated after the flexural and shear reinforcement of the slab are designed. The concept of deflection is discussed in this chapter along with the selection of the thickness of the slab. The code specifies the minimum thickness of slab in table 7.3.1.1, unless the slab is supporting concentrated loads. The values provided are for steel grade f_y = 60,000 psi. If any other grade of steel is used, the values need to be multiplied by (0.4 + f_y/100,000). For lightweight concrete (weight w_c), the value needs to be multiplied by the greater of (1) 1.65–0.005w_c and (2) 1.09.

...

Simply supported	L/20
One end continuous	L/24
Two ends continuous	L/28

Table of contents

• Cover
• Halftitle Page
• Title Page
• Copyright Page
• Contents
• Preface
• Author
• SECTION I Concepts and Codes
• SECTION II Design
• SECTION III Miscellaneous Chapters
• Appendix A: Main Design Concepts
• Appendix B: Materials
• Appendix C: Design Loads
• Appendix D: ACI Strength Requirements
• Appendix E: Slabs
• Appendix F: Beams
• Appendix G: Columns
• Appendix H: Walls
• Appendix I: Footings
• Index