Abstract: The paper presents the calibration procedure and background data for the development of design code provisions for wood bridges. The structural types considered include sawn lumber stringers, glued-laminated girders, and various wood deck types. Load and resistance parameters are treated as random variables, and therefore, the structural performance is measured in terms of the reliability index. The statistical parameters of dead load and live traffic load, are based on the results of previous studies. Material resistance is taken from the available test data, which includes consideration of the post-elastic response. The resistance of components and structural systems is based on the available experimental data and finite element analysis results. Statistical parameters of resistance are computed for deck and girder subsystems as well as individual components. The reliability analysis was performed for wood bridges designed according to the AASHTO Standard Specifications and a significant variation in reliability indices was observed. The recommended load and resistance factors are provided that result in consistent levels of reliability at the target levels.
DOI: 10.1061/（ASCE）1084-0702（2005）10:6（636）
CE Database subject headings: Bridges, wooden; Calibration; Load and Resistance Factor; Design; Bridge decks.


Introduction

In 1993 AASHTO adopted a new load and resistance factor design （LRFD） code for highway bridges. The new code provides a rational basis for the design of steel and concrete structures.Although wood bridge design was also included in LRFD format,the calibration was not carried out for these structures （Nowak 1995, 1999）. Therefore, there was a concern about the consistency of the reliability level for wood structures.
Previous studies showed that the reliability index for wood bridge components can be significantly different than for steel or concrete structures （Nowak 1991）. The degree of variation for wood properties varies depending on dimensions, load duration,moisture content, and other parameters. In case of wood bridges,it is important to consider the structural system or subsystem as well as individual elements/components.
內容摘要：這篇論文為木橋設計規(guī)范的確定發(fā)展提供了校準方法和基本數(shù)據(jù)。結構類型被認為包括鋸成的木梁、膠合梁及各種類型的木梁板。負載和阻力參數(shù)被視為隨機變量，因而，結構特性是根據(jù)可靠性指標來測定的。橋的恒載和交通活載，都是基于先前的研究結果。材料的阻值是取自可用的測試得來的數(shù)據(jù)，這些數(shù)據(jù)中包含了考慮有彈性反應作用的數(shù)據(jù)。阻力的組成和結構系統(tǒng)是基于可利用的實驗數(shù)據(jù)和有限元分析的結果。阻力的統(tǒng)計參數(shù)是由梁板、梁體及個別的組件計算而得。對木橋進行可靠性分析設計應依照AASHTO標準設計規(guī)范并且要注意到可靠性指標中的一個重要變化，負載限度和阻力系數(shù)應該和可靠性程度及目標水準相一致。
DOL：10.1061/(ASCE)1084-0702(2005)10:6(636)
土木工程師數(shù)據(jù)庫的關鍵詞：橋梁、木制的、校準、負載和阻力系數(shù)、設計、橋板。


論文簡介
1993年，美國國家公路與運輸協(xié)會采納了一部新的公路橋的負載和阻力因素的設計法規(guī)。這部新法規(guī)為鋼結構與混凝土結構提供了一個合理的設計依據(jù)。盡管木橋的設計在設計法規(guī)中也還包含在內，但是對這些結構此校準法還沒有予以實行（諾瓦克1995，1999）。因此，對于木結構的可靠性水平的一致性問題還有一些疑慮。
先前的一些研究指明木橋結構部件的可靠度與鋼結構或者混凝土結構有明顯的不同之處（諾瓦克 1991）。這個程度的變化對木材性質的影響則取決于尺寸大小,負載持續(xù)時間、水分含量等參數(shù)。假若是木橋，考慮到其結構體系或次要系統(tǒng)以及個別元件/部件是非常重要的一步。