Table of Contents
TABLE OF CONTENTS
1.0 — INTRODUCTION
1.1 — General
1.2 — Scope and Limitation
2.0 — CAUSES AND CATEGORIZATION OF CRACKING
2.1 — Shortening in post-tensioned construction
2.2 — Restraint-to-shortening illustration
2.3 — Cracking categorization
2.3.1 — Slab cracks
2.3.2 — Column cracking
2.3.3 — Wall cracking
2.4 — Temperature differentials
3.0 — CRACK MITIGATION PHILOSOPHY AND STRATEGIES
3.1 — Mitigation philosophy
3.2 — Considerations for release connections
3.2.1 — Time lapse, and temporary and permanent release
3.2.2 — Slab length
3.2.3 — Impact of construction quality
3.2.4 — Examples of successful implementations of crack mitigation measures
3.2.5 — Incomplete or poor implementation of crack mitigation measures
3.2.6 — Common field shortcomings in implementation of crack mitigation measures
3.3 — Layout of restraining members
3.4 — Concrete properties
3.4.1 — Concrete mixture drying shrinkage factors
3.4.2 — Concrete mixture – recommended best practices
3.4.3 — Shrinkage-reducing admixtures, shrinkage-compensating cement
3.5 — Structural separation
4.0 — CRACK MITIGATION DETAILING
4.1 — Pour strips, joints, and favorable pour sequencing
4.1.1 — Pour strips
4.1.2 — Construction joints
4.1.3 — Pour sequencing
4.1.4 — Sand pockets at column base
4.2 — Temporary and permanent wall/slab release
4.2.1 — Release concept
4.2.2 — Release performance
4.2.3 — Foundation wall/slab release details
4.2.4 — Bearing wall/slab release details
4.2.5 — Non-Bearing wall/slab details
4.3 — Other temporary and permanent release connections
4.3.1 — Slab/column
4.3.2 — Slab joints
4.3.3 — Wall joints
4.4 — Embedded release devices
4.5 — Additional non-prestressed reinforcement
4.6 — Addition/improved layout of tendons
5.0 — STRUCTURAL EVALUATION AND REPAIR OF CRACKS
5.1 — Contribution of post-tensioning in slabs
5.1.1 — Uplift
5.1.2 — Precompression
5.1.3 — Strength
5.2 — Summary of structural evaluation and recommendations
5.3 — Crack repair
5.3.1 — Objectives of crack repair
5.3.2 — Which cracks to repair
5.3.3 — When and how to repair
6.0 — COMPUTATION OF SHORTENING MOVEMENT
6.1 — Theoretical background
6.2 — ACI 209 method
6.2.1 — Shrinkage strain
6.2.2 — Creep strain
6.3 — PCI design aid method
6.3.1 — Shrinkage strain
6.3.2 — Creep strain
6.3.3 — Temperature strain
6.4 — Simplified method
6.4.1 — Shrinkage strain
6.4.2 — Creep coefficient
6.4.3 — Temperature strain
6.4.4 — Elastic shortening strain
6.4.5 — Total shortening
6.5 — Shortening calculation examples
6.5.1 — Example no. 1
6.5.2 — Example no. 2
6.5.2.1 — ACI 209 method
6.5.2.2 — PCI design aid method
6.5.2.3 — Simplified method
6.5.3 — Example no. 3
6.5.3.1 — ACI 209 method
6.5.3.2 — PCI design aid method
6.5.3.3 — Simplified Method
6.5.3.4 — Summary of results
6.5.4 — Example no. 4
6.5.4.1 — Case 1: (t – tc) = 30 days
6.5.4.1.1 — ACI 209 method
6.5.4.1.2 — PCI design aid method
6.5.4.2 — Case 2: (t – tc) = 365 days
6.5.4.2.1 — ACI 209 method
6.5.4.2.2 — PCI design aid method
6.5.4.3 — Case 3: (t – tc) = final
6.5.4.3.1 — ACI 209 method
6.5.4.3.2 — PCI design aid method
6.5.4.3.3 — Summary of results
7.0 — SHORTENING CONSIDERATION IN FINITE ELEMENT ANALYSIS
7.1 — Introduction
7.2 — Example models
7.3 — Finite element analysis
7.3.1 — Assumptions
7.3.2 — Tensile stress diagrams
7.3.3 — Model 1 and model 2 comparison
7.3.4 — Model 2 restraint mitigation comparison
7.3.5 — Comparison recap
7.4 — Strength checks due to restraint to shortening
7.5 — Summary
8.0 – SUMMARY
9.0 — REFERENCES
9.1 — Cited references
9.2 — Photo, figure, and table credits