Chapter 6 - two-way Floor Design example - Post-Tensioned Concrete Frame under Construction

Oct 24, 2026

Upload by OKfine

Example Chapter 6 explains the design of a two-way post-tensioned floor slab for a multistory building with irregular support arrangement. The slab uses column drops for punching shear and drop panels for additional capacity against high negative moments. It compares unbonded and bonded (grouted) post-tensioning systems and applies American codes (ACI 318 and IBC) as well as the European Code (EC2). The workflow covers geometry, material properties, loads, design parameters, post-tensioning selection, code checks for serviceability and strength, and detailing for construction.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages32

Reading Time1 h 21 min

AccessFree to download

Foreword

DESIGN STEPS

1. GEOMETRY AND STRUCTURAL SYSTEM

2. MATERIAL PROPERTIES

3. LOADS

4. DESIGN PARAMETERS

5. ACTIONS DUE TO DEAD AND LIVE LOADS

6. POST-TENSIONING

7. CODE CHECK FOR SERVICEABILITY

8. CODE CHECK FOR STRENGTH

9. CODE CHECK FOR INITIAL CONDITION

10. DETAILING

Chapter 6 two-way Floor Design example Post-Tensioned Concrete Frame under Construction (California, P634) Foreword The following example represents a floor of a multistory building with an irregular arrangement of supports. The slab is provided with both column drops for punching shear, and drop panels for additional strength in resisting the high negative moments over selected supports. Further, the optimum post-tensioning leads to different number of strands along the length of the design strip selected, as well as change in tendon profile from span to span. The objective in selecting an irregular and complex structure is to expose you to the different design scenarios that are common in real life structures, but are not covered in traditional text books. Design conditions that are not directly covered in the following example, but are important to know of, are introduced and discussed as comments or added examples. Steps that are common knowledge, such as the calculation of moments and shears, once the geometry of a structure, its material properties and loading are known, are not covered in detail. You are referred to your in-house frame programs for their computation. The design example covers side by side both the unbonded and bonded (grouted) post-tensioning systems, thus providing a direct comparison between the design process of the two options. In addition, in parallel, the design uses both the current American building codes (ACI 3181 and IBC2 ) and the European Code (EC2)3. There are three methods commonly used for the design of a post-tensioned floor system – Simple Frame 1 ACI 318-11 2 IBC International Building Code 2012 3 EC2 EN 1992-1-1:2004(E) Design of Post Tensioned Buildings [www.PT-structures.com](www.PT-structures.com) 6-2 Design of Post Tensioned Buildings Methods (SFM)4, Equivalent Frame Method (EFM); and Finite Element Method (FEM). Among the three, the EFM has been the primary method of design used by leading consulting firms for many years. However, due to its complexity, it does not lend itself to daily hand calculation of real structures in the environment of a consulting firm. Computer programs based on the EFM, such as ADAPT-PT are generally used. Recently, many consultants sacrifice the efficiency of designs based on EFM with respect to its capability to yield optimum designs, and opt for designs based on Finite Element Method (FEM), such as those based on Floor-Pro5. FEM-based designs can model the entire floor system and provide seamless integration of the design process from architectural drawings to fabrication documents. (a) 3D Solid View of the Floor System (P471) (b) See through View of the Floor System (P472) 0-3 3D Views of the Floor System 4 The Simple Frame Method (SFM) in UK and the literature based on UK practice is referred to as “Equivalent Frame Method.” It is based strictly on the cross-sectional geometry of the slab frame being designed. The term Equivalent Frame Method in the US literature is based on an approximation that is intended to simulate the two-way action of a floor slab. [5](5 www.adaptsoft.com)[ www.adaptsoft.com](5 www.adaptsoft.com) Hand calculations, such as the one presented herein, use the SFM. Two text fonts are used in the following. The numerical work that forms part of the actual calculations uses the font shown below: This font is used for the numerical work that is part of the design. The following text font is used, where comments are made to add clarification to the calculations: This font is used to add clarification to the calculations. DESIGN STEPS 1. GEOMETRY AND STRUCTURAL SYSTEM 1.1 Geometry of the Floor System 1.2 Support Lines and Tributaries 1.3 Idealized Design Strips 2. MATERIAL PROPERTIES 2.1 Concrete 2.2 Nonprestressed Reinforcement 2.3 Prestressing 3. LOADS 3.1 Selfweight 3.2 Superimposed Dead Load 3.3 Live Load 4. DESIGN PARAMETERS 4.1 Applicable Code 4.2 C

FAQs

What floor behavior does this example aim to capture?

It models a two-way post-tensioned slab on columns and walls with irregular support geometry, including column drops and drop panels to address punching shear and negative moment resistance.

How are post-tensioning systems compared in the example?

The chapter presents design side by side for unbonded and bonded (grouted) post-tensioning systems to directly compare the design process for both options.

Which codes are used for the design and checks?

The design uses current American building codes (ACI 318 and IBC) along with the European Code (EC2) for code checks and governing design conditions.

Oct 24, 2026

Upload by OKfine