• 作者： 蔡益超
• 作者服務機構： 國立臺灣大學土木系
• 中文摘要： 本文首先根據Julian氏於1957年所整理的171個38至1"鋼筋降伏強度，3974個ASTM A-7結構鋼降伏強度試驗資料及American Concrete Institute於1964年所做92個工地取樣混凝土極限抗壓強度試驗資料求出鋼筋，結構鋼，混凝土的強度或然率分佈函數。其次根據結構可靠度理論研究荷重等於設計荷重時（如呆重）鋼筋，混凝土與結構鋼之可靠度與其安全係數的關係。吾人發現鋼筋的安全係數取 1.30以上，混凝土的安全係數取1.45以上，結構鋼的安全係數取1.40以上所設計出的結構物己非常安全。 當荷重可大於設計荷重而為常態分佈時（如風力，地震力等），筆者就不同的標準離差與荷重超過設計荷重的或然率利用電子計算機做數值積分，求出鋼筋，混凝土可靠度與安全係數之關係。以荷重超過設計荷重的或然率為10%，標準離差較小的情況為例，鋼筋的安全係數在1.60，混凝土的安全係數在1.70以上則所設計出的鋼筋混凝土結構物已非常安全。 大體說來，工程界常用鋼筋安全係數為1.7混凝土安全係數為2.2似乎可依荷重特性斟以降低。
• 英文摘要： Strength probability distribution function of reinforcing bar and structural steelare calculated at first basing upon test data of yield strengh of 171 reinforcing barranging from 3'8" to 1 "and yield strengh of 3974 ASTM A-7 structural steel publi-‵shed by Julian in 1957. Compressive strength probability distribution function ofconcrete is also calculated according to field test data of 92 samples submitted byAmerican Concrete Institute in 1964. Relation between reliability and safety factorof reinforcing bar, structural steel, and concrete are then studied according to theoryof reliability under the condition that loading is equal to design load．Result revealsthat it is very prudent to use 1.30, 1.45, 1.40 as safety factor for reinforcing bar,concrete and structural steel respectively to design a stracture. Loading with normal distribution which is allowed to exceed the design load isstudied next. Relationship between reliability and safety factor of reinforcing bar andconcrete is studied with various standard of deviation and possible probability ofapplied load which may exceed the design load. Take certain set of parameter forinstance, when standard of deviation is small and probability of applied load whichexceed design load is 10%' we can find it is very safe to design reinforced concretestructures using 1.60 and 1.70 as safety factor of reinforcing bar and concreterespectively. Engineers usually take 1.7 as safety factor for reinforcing bar and 2.2 for con-crete. It seems that these figures can be lowered a little without danger to meetthe requirement of economy.
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