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  • LRFD
    Steel Design using Advanced Analysis

    This book presents a simple, concise, and direct method of designing steel frames, using a practical, advanced technique that produces member sizes very close to those given by the LRFD method. The main advantage of Advanced Analysis is that the laborious and sometimes confused member capacity checks needed to satisfy the AISC-LRFD specifications are avoided. Advanced Analysis captures the limit state strength and stability of a structural system and its component members directly. While elastic analysis is still the standard in engineering practice, a new generation of Codes is expected to adopt Advanced techniques and thus significantly reduce cost and time. In recent years, the rapid development of computer hardware and software, coupled with growing knowledge of structural behavior has made it possible to introduce Advanced Analysis to the design office.

    This book is written for both academics in Universities and engineers in the industry. The reader need have no specific knowledge of this subject, but should be familiar with methods of elastic analysis and conventional LRFD design. Advanced Analysis has been presented here in a practical and simple manner for both analysis and design with emphasis placed upon implementing advanced analysis in engineering practice. This book describes not only this general method in as a simple manner as possible, but also provides introduction on how this new method can be used in frame design. The scope of the book is indicated by its contents.

    Chapter 1 presents the development of various methods of advanced analysis and a review of the AISC-LRFD method. The concept and formulation of Advanced Analysis are discussed in Chapter 2. Chapter 3 addresses verification studies for a wide range of frames. The step-by-step procedure required to perform this analysis is described in Chapter 4. Chapter 5 introduces an ucational version of this advanced technique coded in FORTRAN. A floppy disk is included on the back cover to exercise this new tool. In Chapter 6, design examples using advanced analysis are presented in detail, and also compared to the LRFD method. The design examples cover frames including braced, unbraced, and semi-rigid frames. The input data for each design example are provided so engineers can easily reproduce their own input. The authors thank Purdue University Teaching Assistant Elizabeth M. Webster and Graduate Student I-hong Chen for their help in proofreading this manuscript and their valuable comments. The authors also extend special thanks to Mrs. Molly Stetler for her outstanding job in typing the manuscript.

    December 1996
    Wai-Fah Chen
    Seung-Eock Kim
    ◎ Contents

     1.1  Introduction
     1.2  Design Formats
           1.2.1  Allowable stress design
           1.2.2  Plastic design
           1.2.3  Load and resistance factor design
           1.2.4  Advanced analysis/design
     1.3  AISC-LRFD Design Method
           1.3.1  Overview of LRFD Frame Design
           1.3.2  Column curves
           1.3.3  Beam-column interaction equations
           1.3.4  Effective length factor
           1.3.5  Moment amplification factors
           1.3.6  Illustrative example 1: Two-bay unbraced frame
           1.3.7  Illustrative example 2: Leaning column frame
           1.3.8  Semi-Rigid Frames
     1.4  Methods of Advanced Analyses
           1.4.1  Plastic-zone method
           1.4.2  Quasi plastic hinge method
           1.4.3  Elastic-plastic hinge method
           1.4.4  Notional load plastic hinge method
           1.4.5  Refined plastic hinge method
     1.5  Why Advanced Analysis
     1.6  Summary


     2.1  Introduction
     2.2  Key Factors Influencing Steel Frame Behavior
           2.2.1  Gradual yielding associated with flexure
           2.2.2  Gradual yielding associated with residual stresses
           2.2.3  Second-order effects
           2.2.4  Geometric imperfections
           2.2.5  Connection nonlinearity
     2.3  Desirable Attributes for Practical Advanced Analysis
     2.4  Second-Order Refined Plastic Hinge Analysis
           2.4.1  Stability functions accounting for second-order effect
           2.4.2  Incremental force-displacement relationship
           2.4.3  Cross-section plastic strength
           2.4.4  Modification of element stiffness for the presence of plastic hinges
           2.4.5  Tangent modulus model associated with residual stresses
           2.4.6  Two-surface stiffness degradation model associated with flexure
     2.5  Analysis of Semi-Rigid Frames
           2.5.1  Types of semi-rigid connection
           2.5.2  Practical modeling of connections
           2.5.3  Formulation of initial stiffness and ultimate moment capacity
           2.5.4  Empirical equation for shape parameter
           2.5.5  Practical estimation of three parameters using computer program
           2.5.6  Incremental force-displacement relationship accounting for semi-rigid
     2.6  Geometric Imperfection Methods
           2.6.1  Explicit imperfection modeling method
           2.6.2  Equivalent notional load method
           2.6.3  Further reduced tangent modulus method
     2.7  Numerical Implementation
     2.8  Summary


     3.1  Introduction
     3.2  Axially Loaded Columns
     3.3  Isolated Beam-Columns
     3.4  Mathematically Identical Columns
     3.5  Rigidly Jointed Truss
     3.6  Braced Frames
     3.7  Sway Frames
           3.7.1  Kanchanalai's frame in strong-axis bending
           3.7.2  Kanchanalai's frame in weak-axis bending
           3.7.3  Vogel's frame
     3.8  Special Frames
           3.8.1  Braced column with K-factor greater than 1.0
           3.8.2  Unbraced frame with K-factor less than 1.0
     3.9  Semi-Rigid Frames
           3.9.1  Displacement characteristics
           3.9.2  Comparison with analytical results
           3.9.3  Comparison with experimental results
     3.10  Summary


     4.1  Introduction
     4.2  Design Format
     4.3  Loads
           4.3.1  Dead load
           4.3.2  Live loads
           4.3.3  Highway live loads
           4.3.4  Impact
           4.3.5  Wind load
           4.3.6  Earthquake load
           4.3.7  Snow load
           4.3.8  Rain load
     4.4  Load Combinations
     4.5  Resistance Factors
     4.6  Establishment of Structural System
           4.6.1  Low-rise structures
           4.6.2  Multistory structures
           4.6.3  Forms of bracing
           4.6.4  Other design consideration
     4.7  Section Application
     4.8  Preliminary Member Sizing
           4.8.1  Approximate analysis
           4.8.2  Approximate member sizing
     4.9  Modeling of Structural Members
           4.9.1  Number of elements for a beam subjected to distributed transverse loads
           4.9.2  Number of elements for a column without geometric imperfections
           4.9.3  Number of elements for a column with geometric imperfections
     4.10  Modeling of Geometric Imperfection
           4.10.1  Explicit imperfection modeling
           4.10.2  Equivalent notional loads modeling
           4.10.3  Further reduced tangent modulus modeling
     4.11  Load Application
           4.11.1  Proportional loading
           4.11.2  Incremental loading
     4.12  Analysis
     4.13  Load-Carrying Capacity
     4.14  Serviceability Limits
     4.15  Ductility Requirements
           4.15.1  Compactness
           4.15.2  Lateral torsional buckling
     4.16  Adjustment of Member Sizes
     4.17  Summary


     5.1  Introduction
     5.2  Program Overview
           5.2.1  Nonlinear analysis routines
           5.2.2  Organization of computer program
           5.2.3  Hardware requirements
           5.2.4  Execution of program
     5.3 Users  Manual
           5.3.1  General rules
           5.3.2  Input instructions
     5.4 Example
           5.4.1  Frame configuration and load condition
           5.4.2  Input data preparation
           5.4.3  Program execution
           5.4.4  Output interpretation
     5.5  Modification of In-House Program
           5.5.1  Stability function
           5.5.2  Cross-section plastic strength
           5.5.3  CRC tangent modulus
           5.5.4  Parabolic function
           5.5.5  Geometric imperfection
           5.5.6  Semi-rigid connection
     5.6  Summary


     6.1  Introduction
     6.2  Simple Structures
           6.2.1  Three-span continuous beam
           6.2.2  Two-story column
     6.3  Truss Structures
           6.3.1  Roof truss
           6.3.2  Pratt truss
     6.4  Braced Frames
           6.4.1  Simple braced frame
           6.4.2  Braced eight-story frame
     6.5  Unbraced Frames
           6.5.1  One-story two-bay frame
           6.5.2  Leaning column frame
           6.5.3  Two-story frame
           6.5.4  Eight-story frame
           6.5.5  Five-bay four-story frame
     6.6  Semi-Rigid Frames
           6.6.1  Two-story one-bay semi-rigid frame
           6.6.2  Two-story four-bay semi-rigid frame
     6.7  Summary

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    연구실명 : 교량 및 강구조 연구실  
    주소 : 서울 광진구 군자동 98 세종대학교 건설환경공학과  
    TEL : 02-3408-3291   FAX : 02-3408-4332  
    Copyrightⓒ by Bridge and Steel Structure Lab All rights reserved.   
    연구실명 : 교량 및 강구조 연구실  
    주소 : 서울 광진구 군자동 98 세종대학교 건설환경공학과  
    TEL : 02-3408-3291   FAX : 02-3408-4332  
    Copyrightⓒ by Bridge and Steel Structure Lab All rights reserved.