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Long‐term investigations on reduction of constraint forces caused by imposed deformation by creep
Author(s) -
Berger Johannes,
Feix Juergen
Publication year - 2020
Publication title -
structural concrete
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 34
eISSN - 1751-7648
pISSN - 1464-4177
DOI - 10.1002/suco.202000233
Subject(s) - creep , stiffness , structural engineering , deformation (meteorology) , statically indeterminate , viscoelasticity , constraint (computer aided design) , materials science , cracking , reduction (mathematics) , mechanics , term (time) , composite material , mathematics , engineering , physics , geometry , quantum mechanics
External constraint is an action that arises when a structure cannot deform freely. This deformation may be caused by imposed deformation. These deformations lead to support reactions and internal forces only in statically indeterminate systems and are proportional to the absolute values of the structural stiffness. The structural stiffness is significantly reduced by creep of concrete. The classical models for calculating the creep impact on constraint forces assume linear‐elastic or linear‐viscoelastic behavior. The influence of the reinforcement on the creep deformation is neglected as well as the effect of cracking. For this reason, experiments were carried out to obtain results on the creep‐induced degradation of constrained forces caused by imposed deformations. Long‐term experiments were performed on a two‐span beam on which the constraint force was applied by lifting the middle support. Dimensions of the test bodies were l/w/h = 7.3 m/0.4 m/0.2 m. Measurements were carried out on two test bodies, one conventional reinforced test body and one post‐tensioned test body. Thus, the stiffness of a cracked and non‐cracked test body was given. As a result, the influence of the reinforcement as well as effect of crack formation can be taken into account. The experiment lasted over a period of 500 days. The aim is to compare the results of the theoretical models taking into account different stiffness and different creep behavior with the measured test results.