Bridge Superstructure Tolerance to Total and Differential Foundation Movements (2018) / Chapter Skim
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NCHRP Project 12-103 1 NCHRP Project 12-103 Bridge Superstructure Tolerance to Total and Differential Foundation Movements Final Report 1 Introduction 1.1 Motivation and Research Objectives Article 10.5.2.2 in AASHTO LRFD provides guidance for tolerable movements and movement criteria for highway bridges. The commentary, Article C10.5.2.2, states the following: "….angular distortions between adjacent foundations greater than 0.008 rad.
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NCHRP Project 12-103 2 incorporation of the aforementioned AASHTO LRFD criteria for angular distortion through a series of examples for two-, four- and five-span bridges for a wide range of foundation settlements. Ballot items for incorporation of the work by Samtani and Kulicki (2016)
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NCHRP Project 12-103 3 • LD movements – This type of support movement occurs when all bearing locations at a single support undergo the same amount of vertical translation. The tolerable level of this type of support movement may be limited by Strength and Service limit states or ride-ability criteria.
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NCHRP Project 12-103 4 1.2 Project Organization To satisfy the research objectives described above, the project activities were organized into four phases as shown in Figure 1-1. The specific objectives for each phase are provided in Table 1-1.
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NCHRP Project 12-103 5 (b) Develop efficient and accurate modeling approaches capable of simulating the response of common bridge types to support movements (c)
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NCHRP Project 12-103 6 each parameter on the chosen response variable (e.g., tolerable settlement, moment, shear, etc.) , as well as the effects of interactions between various parameters on the response variable.
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NCHRP Project 12-103 7 Figure 1-2 - Flow chart of key action items for Phase II of this project. Automate and validate LRFD design for primary bridge types (T2.1.2)
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NCHRP Project 12-103 8 Table 1-2 - Parameters investigated in this project. Parameter Bounds Notes Di sc re te P ar am et er s Bridge Type Steel and PS Concrete Multi-girder These bridge types were selected as they represent the most commonly designed and built structures Bridge Continuity Simple, 2-Span Continuous, 3-Span Continuous These levels of superstructure continuity allow for no continuity, continuity at one end of each span, and continuity at both ends of a span, respectively Co nt in uo us P ar am et er s Span Length 40 ft to 160 ft Typical span lengths for multi-girder bridges.
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NCHRP Project 12-103 9 Table 1-3 - Limit states investigated in this project. Limit State Description Strength I Flexure and shear limitations under basic load combinations related to normal vehicle use of the bridge Service II Flexure limitations intended to control yielding of steel structures under basic load combinations related to normal vehicle use of the bridge Service I & III Compression/tension limitations under the load combination for analysis of longitudinal compression/tension in PS concrete superstructures Task 2.3: Identification of Influential Parameters Once convergence was achieved the results were plotted and interpreted to understand and explain the underlying mechanisms.
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NCHRP Project 12-103 10 • Closed Steel Box Girders Bridges • Open Steel Box Girder Bridges (Tub Girder Bridges) • Cast-in-Place Concrete Multi-Cell Box Girder Bridges The work done for Task 2.4 is further detailed in Section 7 of this report.
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NCHRP Project 12-103 11 • Section 6: Pre-Stressed Concrete Bridge Results (T2.2 and T2.3) presents the results of the computed tolerable support movements as well as an interpretation of the trends and influential parameters observed for PS concrete multi-girder bridges.
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