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Jens Löschmann, Peter Mark

• Several aged reinforced concrete (RC) structures need to be strengthened. A typical method is to subsequently add rebar into slots filled with bonding mortar. However, this kind of strengthening only acts for live loads, not for dead loads, if no prestressing or prior lifting is applied. To overcome this deficiency, a novel method is presented. It activates the postinstalled reinforcement for all types of loading by temporarily inducing temperature from the outside. Doing so, statically indeterminate structures are locally relieved from stresses by constraint moments from systematically induced vertical temperature gradients during strengthening. To set the size of the gradients, the nonlinear material behavior, especially the significant reductions in constraint forces due to softening, is taken into account. If tempering is stopped after strengthening, stresses from dead loads redistribute over the newly formed total cross section. The method is theoretically derived, discussed, and verified in the lab on a two-span RC girder. It turns out appropriate to enhance the bending resistance of beams or slabs.