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Study on Nondeterminacy of Large or Small Eccentricity in Eccentric
Compression Members
XIAO Guanghong, TANG Minghao, XIE Xin
2018, 37(11):
21-25.
DOI: 10.3969/j.issn.1674-0696.2018.11.04
In the formulas of Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts(short for
Code)for calculation of eccentric compression members, the stress of reinforcing steel is discontinuous, which, to a certain extent,
has an influence on the depth of compression zone, judgment of large or small eccentricity and bearing capacity of members. Firstly,
in order to study the uniqueness of the quadratic equation and the distribution of the depth of compression zone, theoretical analysis
of formulas for eccentric compression members of large or small eccentricity was made. Then, for the purpose of proving the influence
on bearing capacity of the eccentric compression member, concrete illustrations containing 3 groups of material, namely C30-HRB335,
C50-HRB335 and C30-HRB400, were used for contrastive study. Results show that there is only one solution in(0，+∞)for the quadratic
equation; under the circumstance of firstly assuming that it is an member of large eccentricity, there is a blank interval in the
distribution of depth of compress zone; under the circumstance of firstly assuming that it is a member of small eccentricity, there
are both a blank interval and a wrong judged interval, and the phenomenon of nondeterminacy wont happen when judging the
eccentricity. The bearing capacity of the same eccentric compress member has error at the critical eccentricity under both hypotheses.
The error of firstly assuming large eccentricity is smaller than that of firstly assuming small eccentricity. There is a positive
correlation between the error and the strength of materials. Research on distribution of depth of compression zone and bearing
capacity has referential value for further revision of the formulas in the Code.
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