Study On The Effect Of Initial Stress On Bearing Capacity Of Strengthened Structure Members Subjected To Axial Compression

The strengthened structure is the structure subjected to twice-loading. Because ofcomplexity of lag stress, it differs from new normal structures. Each strengtheningmethod has its calculating specialty. This thesis focuses research on mechanicalbehavior of the strengthened masonry wall with reinforced concrete layer and thestrengthened concrete column with reinforced concrete, and analyses the influence ofvarious strengthening factors on utilization factor of material strength, by means ofFEM numerical simulation and the derivation of theoretical formulas. Then this thesisverifies the bearing capacity formulas of relevant codes and proposes some advice foramendments. Meanwhile, this thesis also provides some suggestions aboutstrengthening design. The details of results and conclusions are as follows.（1）The latest research progress of structure member strengthening withreinforced concrete layer or reinforced concrete is introduced and some shortcomingsin current research results are also pointed out.（2）Based on strain control theory, this thesis discusses yield failure ofsecondary loaded structure members. The conclusion is that whether the originalmaterial or new material fail first is only related to the initial stress level.（3）According to stress-strain relations, this thesis deduces axial compressionformulas of bearing capacity and strength utilization factors, about both thestrengthened masonry wall with reinforced concrete layer and the strengthenedconcrete column with reinforced concrete. These formulas prove that bearing capacityand strength utilization factors of secondary loaded structure members are merelyrelated to the initial stress level.（4）Conclusions of numerical simulation by FEM software ANSYS confirmcorrectness of derivation formulas. Furthermore, finite element analysis results showthat strength utilization factors of original masonry and new concrete have norelationship with almost all strengthening factors. But strength utilization factor ofnew steel bar is not only related to the initial stress level, but also its own strength.（5）By comparing analysis of derivation formulas, numerical simulation andrelevant codes, this thesis proposes some amending advices about calculation of bearing capacity and strength utilization factors for the strengthened masonry wallwith reinforced concrete layer and the strengthened concrete column with reinforcedconcrete. At last, this thesis provides some reasonable suggestions about strengtheningdesign and construction.