Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview and Volume 2: Guidelines (2017) / Chapter Skim
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Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms Volume 1: Research Overview NCHRP RESEARCH REPORT 864 NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM
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TRANSPORTATION RESEARCH BOARD 2017 EXECUTIVE COMMITTEE* OFFICERS Chair: Malcolm Dougherty, Director, California Department of Transportation, Sacramento ViCe Chair: Katherine F
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2017 N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP RESEARCH REPORT 864 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms Volume 1: Research Overview M Saiid Saiidi Mostafa Tazarv Sebastian Varela Infrastructure InnovatIon, LLc Reno, NV Stuart Bennion M
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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed research is the most effective way to solve many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others.
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The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, nongovernmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research.
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C O O P E R A T I V E R E S E A R C H P R O G R A M S AUTHOR ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 12-101 by Infrastructure Innovation, LLC in collaboration with BergerABAM and Modjeski and Masters, Inc. The principal investigator (PI)
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This report describes the evaluation of new materials and techniques for design and construction of novel bridge columns meant to improve seismic performance. These techniques include shape memory alloy (SMA)
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FRP wrapping) and analytical techniques (e.g., current design practice, direct displacement based design, and substitute structure design method)
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1 Summary 3 Chapter 1 Introduction 3 1.1 Problem Statement 3 1.2 Research Objectives 4 1.3 Document Organization 5 Chapter 2 Guidelines for Evaluation of Novel Columns 6 Chapter 3 Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 7 3.1 Proposed Seismic Design and Construction of SMA-Reinforced ECC Columns 7 3.1.1 Introduction 7 3.1.2 Application of SMA-Reinforced ECC Columns 7 3.1.3 Materials 7 3.1.3.1 SMA 8 3.1.3.2 ECC 10 3.1.4 Analysis of SMA-Reinforced ECC Columns 10 3.1.4.1 Selection of Analysis Procedure to Determine Seismic Demand 10 3.1.4.2 Effective Section Properties 11 3.1.4.3 Damping Ratio for Dynamic Analysis 11 3.1.4.4 Displacement Modification for Damping 12 3.1.4.5 Displacement Modification for Short-Period Bridges 13 3.1.4.6 Displacement Ductility versus Drift Ratio 14 3.1.4.7 Column Drift Demand Requirement 15 3.1.4.8 Column Force Demand 15 3.1.4.8.1 Moment Demand 15 3.1.4.8.2 Shear Demand 15 3.1.4.8.3 Column Adjoining Member Force Demand 16 3.1.4.9 Residual Drift 16 3.1.5 Design of SMA-Reinforced ECC Columns 16 3.1.5.1 Analytical Plastic Hinge Length 17 3.1.5.2 Column Drift Capacity 17 3.1.5.2.1 Minimum Drift Capacity 17 3.1.5.3 Shear Capacity 19 3.1.5.4 Axial Capacity 19 3.1.5.5 Minimum Lateral Strength 19 3.1.5.6 Other Loading and Strength Design 19 3.1.5.7 Serviceability Design 20 3.1.5.7.1 Shrinkage and Creep 20 3.1.5.7.2 Axial Deformations C O N T E N T S
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20 3.1.6 Details for SMA-Reinforced ECC Columns 20 3.1.6.1 Partially or Fully Cast ECC Columns 20 3.1.6.2 Reinforcement Details 20 3.1.6.2.1 Longitudinal SMA Reinforcement 21 3.1.6.2.2 SMA Bar Size 21 3.1.6.3 Splicing of SMA Reinforcement 22 3.1.6.4 Maximum Axial Load 22 3.1.6.5 Maximum Aspect Ratio 23 3.1.7 Construction of SMA-Reinforced ECC Columns 23 3.1.7.1 Quality Control Tests 23 3.1.7.2 Construction Procedures 23 3.1.7.3 Construction Tolerance 23 3.1.8 References 25 3.2 Proposed Design and Construction of SMA-Reinforced FRP-Confined Concrete Columns 25 3.2.1 Introduction 25 3.2.2 Application of SMA-Reinforced FRP-Confined Concrete Columns 26 3.2.3 Materials 26 3.2.3.1 SMA 27 3.2.3.2 FRP-Confined Concrete 29 3.2.4 Analysis of SMA-Reinforced FRP-Confined Concrete Columns 29 3.2.4.1 Selection of Analysis Procedure to Determine Seismic Demand 29 3.2.4.2 Effective Section Properties 29 3.2.4.3 Damping Ratio for Dynamic Analysis 31 3.2.4.4 Displacement Modification for Damping 31 3.2.4.5 Displacement Modification for Short-Period Bridges 31 3.2.4.6 Displacement Ductility versus Drift Ratio 33 3.2.4.7 Column Drift Demand Requirement 33 3.2.4.8 Column Force Demand 33 3.2.4.8.1 Moment Demand 33 3.2.4.8.2 Shear Demand 34 3.2.4.8.3 Column Adjoining Member Force Demand 34 3.2.4.9 Residual Drift 35 3.2.5 Design of SMA-Reinforced FRP-Confined Concrete Columns 35 3.2.5.1 Analytical Plastic Hinge Length 35 3.2.5.2 Column Drift Capacity 35 3.2.5.2.1 Minimum Drift Capacity 36 3.2.5.3 Shear Capacity 37 3.2.5.4 Axial Capacity 37 3.2.5.5 Minimum Lateral Strength 37 3.2.5.6 Other Loading and Strength Design 38 3.2.5.7 Serviceability Design 38 3.2.5.7.1 Shrinkage and Creep 38 3.2.5.7.2 Axial Deformations 38 3.2.6 Details for SMA-Reinforced FRP-Confined Concrete Columns 38 3.2.6.1 FRP Jacket 39 3.2.6.2 Reinforcement Details 39 3.2.6.2.1 Longitudinal SMA Reinforcement 39 3.2.6.2.2 SMA Bar Size
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39 3.2.6.3 Splicing of SMA Reinforcement 40 3.2.6.4 Maximum Axial Load 41 3.2.6.5 Maximum Aspect Ratio 41 3.2.7 Construction of SMA-Reinforced FRP-Confined Columns 41 3.2.7.1 Quality Control Tests 41 3.2.7.2 Construction Procedures 41 3.2.7.3 Construction Tolerance 41 3.2.8 References 43 3.3 Proposed Design and Construction of FRP-Confined Hybrid Rocking Columns 43 3.3.1 Introduction 43 3.3.2 Application of FRP-Confined Hybrid Rocking Columns 44 3.3.3 Materials 44 3.3.3.1 Steel Tendons 44 3.3.3.2 FRP-Confined Concrete 46 3.3.4 Analysis of FRP-Confined Hybrid Rocking Columns 46 3.3.4.1 Selection of Analysis Procedure to Determine Seismic Demand 46 3.3.4.2 Effective Section Properties 46 3.3.4.3 Damping Ratio for Dynamic Analysis 47 3.3.4.4 Displacement Modification for Damping 47 3.3.4.5 Displacement Modification for Short-Period Bridges 47 3.3.4.6 Displacement Ductility Versus Drift Ratio 48 3.3.4.7 Column Drift Demand Requirement 49 3.3.4.8 Column Force Demand 49 3.3.4.8.1 Moment Demand 50 3.3.4.8.2 Shear Demand 50 3.3.4.8.3 Column Adjoining Member Force Demand 50 3.3.4.9 Residual Drift 51 3.3.5 Design of FRP-Confined Hybrid Rocking Columns 51 3.3.5.1 Analytical Plastic Hinge Length 52 3.3.5.2 Column Drift Capacity 52 3.3.5.2.1 Minimum Drift Capacity 52 3.3.5.3 Shear Capacity 54 3.3.5.4 Axial Capacity 54 3.3.5.5 Minimum Lateral Strength 54 3.3.5.6 Other Loading and Strength Design 54 3.3.5.7 Serviceability Design 54 3.3.5.7.1 Shrinkage and Creep 54 3.3.5.7.2 Axial Deformations 55 3.3.6 Details for FRP-Confined Hybrid Rocking Columns 55 3.3.6.1 FRP Jacket 55 3.3.6.2 Reinforcement Details 55 3.3.6.2.1 Longitudinal Reinforcing Steel Bars 56 3.3.6.2.2 Longitudinal Steel Tendons 56 3.3.6.2.3 Longitudinal Steel Tendon Initial Stresses 57 3.3.6.3 Maximum Axial Load 57 3.3.6.4 Maximum Aspect Ratio 58 3.3.7 Construction of FRP-Confined Hybrid Rocking Columns 58 3.3.7.1 Quality Control Tests 58 3.3.7.2 Construction Procedures
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58 3.3.7.3 Construction Tolerance 58 3.3.7.4 Ducts 59 3.3.8 References 60 Chapter 4 Summary and Conclusions 60 4.1 Summary 61 4.2 Conclusions 61 4.2.1 Proposed AASHTO Guidelines for Evaluation of Novel Columns 61 4.2.2 Seismic Design and Construction of Novel Columns 62 4.2.3 Key Conclusions from Appendix Documents 62 4.2.3.1 Literature Review 62 4.2.3.2 State DOT Survey 62 4.2.3.3 Literature Synthesis and Knowledge Gaps 62 4.2.3.4 Novel Column and Construction Concepts 62 4.2.3.5 Demonstration of Evaluation Guidelines 63 4.2.3.6 Design Examples of Select Novel Columns 63 4.2.3.7 Qualitative Benefits and Economic Impact 63 4.2.3.8 Drift Ratio Displacement Ductility Relationship 63 4.2.3.9 Modeling and Validation for Novel Columns 64 Appendices A–I Note: Photographs, figures, and tables in this report may have been converted from color to grayscale for printing. The electronic version of the report (posted on the web at www.trb.org)
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1 S U M M A R Y Standard reinforced concrete bridge columns are generally designed to dissipate earthquake energy through yielding of longitudinal reinforcing steel and spalling of concrete that collectively cause large plastic deformations in columns. Even though bridge collapse is expected to be prevented using current design specifications, excessive plastic hinge damage and large post-earthquake permanent lateral deformations may cause decommissioning of bridges for repair or replacement.
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2 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview (10) ease of construction, (11)
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3 1.1 Problem Statement Standard reinforced concrete bridge columns are generally designed to dissipate earthquake energy through yielding of longitudinal reinforcing steel and spalling of concrete that collectively cause large plastic deformations in columns. Even though bridge collapse is expected to be prevented using current design specifications, excessive plastic hinge damage and large postearthquake permanent lateral deformations may cause decommissioning of bridges for repair or replacement.
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4 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview conducted under Phase III of the project that consisted of three tasks: (9) develop guidelines with detailed examples for each concept, (10)
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5 A conventional reinforced concrete (RC) bridge column is generally designed to dissipate earthquake energy through yielding of longitudinal reinforcing steel combined with cracking and spalling of concrete that leads to large plastic deformations in columns.
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6The project panel selected three novel columns for further studies: (1) SMA-reinforced ECC columns; (2)
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 7 3.1 Proposed Seismic Design and Construction of SMA-Reinforced ECC Columns 3.1.1 Introduction The main objectives of this study were to develop (1) proposed AASHTO guidelines for the evaluation of new techniques for the design and construction of bridge columns with energy dissipation mechanisms meant to minimize bridge damage and replacement after a seismic event and (2)
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8 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview (–10°C) and the "average low temperature" (a metrological measure)
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 9 ( )
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10 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview (a) Circular Sections (b)
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 11 3.1.4.3 Damping Ratio for Dynamic Analysis For elastic and nonlinear dynamic analyses of SMA-reinforced ECC columns, the damping ratio should be taken as 3.2%, rather than the 5% used for RC. The lower damping ratio recommended for SMA-reinforced ECC accounts for the lower hysteretic damping in columns with flag-shaped behavior that could result in higher displacement demands.
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12 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview An extensive nonlinear parametric study of more than 90 SMA-reinforced ECC columns was conducted in this study. Details of the study are shown in Appendix I
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 13 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 D ri ft R at io (% ) Displacement Ductility Aspect Ratio= 4 Aspect Ratio= 6 Aspect Ratio= 8 Practical Range Proposed relationships are the upper bound Figure 3.1.4.6-1.
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14 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview interpolation is allowed for intermediate aspect ratios. Alternatively, the following equation can be used for intermediate aspect ratios: ( )
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 15 multiplied by the deformability factor, W, which should be taken as 1.2 for SMA-reinforced ECC columns. Linear interpolation can be used for intermediate aspect ratios.
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16 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview moment, see Sections 3.1.4.8.1 and 3.1.4.8.2, and the associated forces (e.g., shear and overturning axial forces) in an essentially elastic manner.
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 17 3.1.5.2 Column Drift Capacity Column drift capacity (Δc) is defined as a displacement at fracture of the column longitudinal bar or compressive failure of the column core concrete.
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18 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview where Vc1 is based on AASHTO SGS (2011) and Vc2 is according to the JSCE Concrete Library 127 (2008)
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 19 The contribution of fibers to shear strength is as follows: ( )
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20 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview be short- and long-term deformations. Serviceability for conventional RC and ECC is addressed through the minimum shrinkage and temperature reinforcement requirement.
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 21 where Ag is the gross area of member cross-section (in.
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22 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview 3.1.6.4 Maximum Axial Load The axial load acting on an SMA-reinforced ECC column, including gravity and seismic demands (Pu) where a pushover analysis is not performed, should satisfy: ≤ ′0.15 (3.1.6.4-1)
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 23 3.1.7 Construction of SMA-Reinforced ECC Columns 3.1.7.1 Quality Control Tests ASTM F2516-07 (2007) should be utilized for tensile testing of NiTi SE SMA to compute the mechanical properties according to the procedure presented in Tazarv and Saiidi (2014b)
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24 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview PCI MNL-116-99.
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 25 FRP Jacket Reinforcing SMA Bars Concrete Co up le r Footing G ap Figure 3.2.1-1. SMA-reinforced FRP-confined plastic hinge detail at column base.
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26 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview SMA-reinforced FRP-confined concrete bridge columns are suggested for sites in which the 1-sec period acceleration coefficient, SD1, is greater than 0.3, which is equivalent to the seismic design category (SDC) C or D according to AASHTO SGS (2011)
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 27 stress-strain material model based on the expected tensile properties is permitted for the design of SMA-reinforced columns. Currently, only plain undeformed SMA bars are available ranging from No.
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28 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview where f * fu is the guaranteed FRP design tensile strength reported by the manufacturer and CE is the environmental reduction factor according to Table 3.2.3.2-1.
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 29 The confinement provided by an FRP jacket alone may not be sufficient to achieve large displacement capacities. Thus, supplementary transverse steel reinforcement may be needed in addition to the FRP jacket.
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30 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview (a) Circular Sections 0.05 0.1 0.15 0.2 0 0.05 0.1 0.15 0.2 0.25 0.3 Circular SMA-Reinforced FRP-Confined Concrete Sections El as tic St iff ne ss R at io (I e ff / I g )
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 31 ratios. The average ratio of flag-shaped hysteretic damping to that of RC columns was 63%.
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32 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 D ri ft R at io (% ) Displacement Ductility Aspect Ratio= 4 Aspect Ratio= 6 Aspect Ratio= 8 Practical Range Proposed relaonships are the upper bound Figure 3.2.4.6-1.
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 33 direction. For multi-column bents, the aspect ratio is the ratio of a portion of the column length (length of column from point of maximum moment to the point of contraflexure)
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34 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview shall not be less than the shear associated with 1.44 times the idealized plastic moment when the calculated failure moment exceeds 1.2Mp (Mu ≥ 1.2Mp)
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 35 minimum and maximum longitudinal reinforcement ratios, maximum aspect ratio)
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36 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview correspond to the minimum displacement ductility capacity for conventional columns. Columns shall be designed to provide at least this level of drift ratio.
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 37 For members that are reinforced with circular hoops, spirals, or interlocking hoops or spirals, the nominal shear reinforcement strength, Vs, is: = pi ′ 2 (3.2.5.3-8) V nA f D s s sp yh where n is the number of individual interlocking spirals or hoops within the spacing s.
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38 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview factors (AASHTO LRFD, Table 3.10.7.1-1) may be used to reasonably size the columns and their adjoining members, only for preliminary design under the load combination of "Extreme Event I." Nevertheless, SMA-reinforced FRP-confined columns should be analyzed and designed according to the present guideline for seismic loads.
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 39 3.2.6.2 Reinforcement Details 3.2.6.2.1 Longitudinal SMA Reinforcement. The area of longitudinal reinforcing SMA bars (ASMA)
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40 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview In this case, the coupler properties in Eq. 3.2.6.3-1 should be based on the coupler that is near the column end.
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 41 analysis including the P – Δ effect is performed to compute the maximum drift capacity of the column. 3.2.6.5 Maximum Aspect Ratio The aspect ratio of SMA-reinforced FRP-confined concrete bents should not exceed 8.
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42 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview Haber, Z B., Saiidi, M
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 43 3.3 Proposed Design and Construction of FRP-Confined Hybrid Rocking Columns 3.3.1 Introduction The main objectives of this study were to develop (1) proposed AASHTO guidelines for the evaluation of new techniques for the design and construction of bridge columns with energy dissipation mechanisms meant to minimize bridge damage and replacement after a seismic event and (2)
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44 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview in the vicinity of the rocking interface. The concrete damage can be minimized when it is jacketed by FRP sheets.
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 45 The maximum compressive strength of a FRP-confined concrete section ( f ′cc)
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46 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview where Ec is the modulus of elasticity of concrete, which for normal weight concrete is ( )
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 47 stated (Section 3.3.6.2)
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48 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview Table 3.3.4.6-1. Detailed results of the parametric study are presented in Appendix H
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 49 multiplied by the deformability factor, W, which should be taken as 1.0 for hybrid rocking columns, including the FRP-confined hybrid rocking columns. Linear interpolation may be used for intermediate aspect ratios.
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50 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview The moment-curvature analysis of a hybrid rocking column section is the same as that for a conventional column with an additional axial load representing the post-tensioning force after all losses. 3.3.4.8.2 Shear Demand.
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 51 (a) Proposed Equation for As/Ag > 0.01 (b)
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52 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview The AASHTO analytical plastic hinge length for RC columns is suggested for the design of hybrid rocking columns because the plastic hinge length is controlled by longitudinal reinforcing steel that is common to both RC and hybrid rocking columns. 3.3.5.2 Column Drift Capacity Column displacement capacity (Δc)
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 53 Where the strength reduction factor, Øs, is 0.9, Vn is the nominal shear capacity of member, Vs is the reinforcing steel contribution to shear capacity, Vc is the concrete contribution to shear capacity, and Vf is the FRP contribution to the shear. Vc and Vs are computed according to AASHTO SGS and are repeated here for circular columns: = 0.8 (3.3.5.3-3)
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54 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview The sum of shear strengths provided by the steel and FRP shall be limited to + ≤ ′0.25 (3.3.5.3-12) V V f As f c e where Ae is the effective area of the cross-section for shear resistance (0.8Ag)
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 55 The estimation of deformations in FRP-confined hybrid rocking columns at a limit state of serviceability is based on two assumptions: (1) strain is proportional to the distance from the neutral axis of the cross-section and (2)
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56 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview Furthermore, the ratio of the flag-shaped column damping to the RC column damping is approximately constant for ductilities greater than 2 (Fig.
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 57 where fpy is the yield strength of steel tendons. The calculation of steel tendon stress losses shall be according to the AASHTO LRFD Bridge Design Specifications (2014, Article 5.9.5)
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58 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview 3.3.7 Construction of FRP-Confined Hybrid Rocking Columns 3.3.7.1 Quality Control Tests FRP testing method for the computation of mechanical properties, fire and life safety, service temperature, and many other parameters should be according to Appendix H of the ACI 440.2R-08 (2008)
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Guidelines for Seismic Design and Construction of Bridge Columns with Improved Energy Dissipating Mechanisms 59 3.3.8 References AASHTO.
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60 4.1 Summary Standard RC bridge columns are generally designed to dissipate earthquake energy through yielding of longitudinal reinforcing steel and spalling of concrete that collectively cause large plastic deformations in columns. Even though bridge collapse is expected to be prevented using current design specifications, excessive plastic hinge damage and large post-earthquake permanent lateral deformations may cause the decommissioning of bridges for repair or replacement.
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Summary and Conclusions 61 converted to a five-star rating method to help bridge owners and designers compare different alternatives and make the final selection. The current AASHTO Guide Specifications for LRFD Seismic Bridge Design uses displacement ductility as a measure of column deformability.
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62 Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms, Volume 1: Research Overview the cementitious material in the plastic hinge could be achieved by the use of damage tolerant materials or through external FRP jackets. The study showed that many of the provisions of the AASHTO SGS are applicable to analysis and design of novel columns, but the design has to also incorporate recent research results that address the characteristics of the particular advanced materials used in the columns.
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Summary and Conclusions 63 star rating discussed under the guidelines was applied to both seismic performance and other considerations and were combined into a single star rating. It was concluded that non-seismic considerations could offset a higher star rating given to seismic performance for some of the columns, leading to a relatively low overall number of stars for these columns.
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64 Appendices A through I are not printed herein but are available for download from the TRB website (trb.org) by searching for "NCHRP Research Report 864." The appendices include the following: Appendix A: Literature Review Appendix B: Survey of State Departments of Transportation Appendix C: Synthesis of Literature Appendix D: Novel Column and Construction Concepts Appendix E: Demonstration of Evaluation Guidelines Appendix F: Detailed Design Examples for Three Novel Columns Appendix G: Benefits and Economic Impact of Novel Columns Appendix H: Relationship Between Drift Ratio and Displacement Ductility Appendix I: Modeling Methods and Validation for Novel Columns A p p e n d i c e s A – i
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Abbreviations and acronyms used without definitions in TRB publications: A4A Airlines for America AAAE American Association of Airport Executives AASHO American Association of State Highway Officials AASHTO American Association of State Highway and Transportation Officials ACI–NA Airports Council International–North America ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act APTA American Public Transportation Association ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATA American Trucking Associations CTAA Community Transportation Association of America CTBSSP Commercial Truck and Bus Safety Synthesis Program DHS Department of Homeland Security DOE Department of Energy EPA Environmental Protection Agency FAA Federal Aviation Administration FAST Fixing America's Surface Transportation Act (2015) FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration FRA Federal Railroad Administration FTA Federal Transit Administration HMCRP Hazardous Materials Cooperative Research Program IEEE Institute of Electrical and Electronics Engineers ISTEA Intermodal Surface Transportation Efficiency Act of 1991 ITE Institute of Transportation Engineers MAP-21 Moving Ahead for Progress in the 21st Century Act (2012)
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