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(nèi)容摘要：這篇論文為木橋設(shè)計(jì)規(guī)范的確定發(fā)展提供了校準(zhǔn)方法和基本數(shù)據(jù)。結(jié)構(gòu)類型被認(rèn)為包括鋸成的木梁、膠合梁及各種類型的木梁板。負(fù)載和阻力參數(shù)被視為隨機(jī)變量，因而，結(jié)構(gòu)特性是根據(jù)可靠性指標(biāo)來(lái)測(cè)定的。橋的恒載和交通活載，都是基于先前的研究結(jié)果。材料的阻值是取自可用的測(cè)試得來(lái)的數(shù)據(jù)，這些數(shù)據(jù)中包含了考慮有彈性反應(yīng)作用的數(shù)據(jù)。阻力的組成和結(jié)構(gòu)系統(tǒng)是基于可利用的實(shí)驗(yàn)數(shù)據(jù)和有限元分析的結(jié)果。阻力的統(tǒng)計(jì)參數(shù)是由梁板、梁體及個(gè)別的組件計(jì)算而得。對(duì)木橋進(jìn)行可靠性分析設(shè)計(jì)應(yīng)依照AASHTO標(biāo)準(zhǔn)設(shè)計(jì)規(guī)范并且要注意到可靠性指標(biāo)中的一個(gè)重要變化，負(fù)載限度和阻力系數(shù)應(yīng)該和可靠性程度及目標(biāo)水準(zhǔn)相一致。
DOL：10.1061/(ASCE)1084-0702(2005)10:6(636)
土木工程師數(shù)據(jù)庫(kù)的關(guān)鍵詞：橋梁、木制的、校準(zhǔn)、負(fù)載和阻力系數(shù)、設(shè)計(jì)、橋板。


論文簡(jiǎn)介
1993年，美國(guó)國(guó)家公路與運(yùn)輸協(xié)會(huì)采納了一部新的公路橋的負(fù)載和阻力因素的設(shè)計(jì)法規(guī)。這部新法規(guī)為鋼結(jié)構(gòu)與混凝土結(jié)構(gòu)提供了一個(gè)合理的設(shè)計(jì)依據(jù)。盡管木橋的設(shè)計(jì)在設(shè)計(jì)法規(guī)中也還包含在內(nèi)，但是對(duì)這些結(jié)構(gòu)此校準(zhǔn)法還沒(méi)有予以實(shí)行（諾瓦克1995，1999）。因此，對(duì)于木結(jié)構(gòu)的可靠性水平的一致性問(wèn)題還有一些疑慮。
先前的一些研究指明木橋結(jié)構(gòu)部件的可靠度與鋼結(jié)構(gòu)或者混凝土結(jié)構(gòu)有明顯的不同之處（諾瓦克 1991）。這個(gè)程度的變化對(duì)木材性質(zhì)的影響則取決于尺寸大小,負(fù)載持續(xù)時(shí)間、水分含量等參數(shù)。假若是木橋，考慮到其結(jié)構(gòu)體系或次要系統(tǒng)以及個(gè)別元件/部件是非常重要的一步。