Elastic And Elasto-Plastic Design Theory And Analysis Method For Typical Disturbed Regions In Concrete Bridges

The major engineering structures are desired to perform with high safety and high durability,which requires to advance the analysis theory of concrete bridges,especially detailed the reinforcement of the regions where anchored by the concentrated forces or the,that is,the disturbed regions(D-regions).In the current practice of bridge engineering,a number of cracking distresses have been occurred in the D-regions due to the lack of sufficient design guidance.To overcome these challenges,the refinement design and analysis approach is necessary for the disturbed regions.The main objective of this study is to develop rational design approaches and analysis methods for some typical D-regions in concrete bridges,especially from the perspective of describing the load transfer mechanism within the structures through experimental tests,elasticity and proposed elastic-to-plastic strut-and-tie model(EPSTM).Details of this study are summarized as follows:(1)As for the regions influenced by the curved tendons in the top slab of the concrete box girder bridges,an analytical solution for bursting stresses caused by curved tendons is derived on the basis of the Airy function,and countermeasures are proposed to mitigate this unfavorable effect.(2)As for the post-tensioned anchorage zones,the sum function method is employed to derive the bursting stresses in the concentric anchorage zones and multi anchorage zones,which can be used to anti-cracking design for anchorage zones.(3)According to the existing compression dispersion model(CDM),an updated CDM is proposed by adding another two boundary conditions for isostatic lines of compression(ILC),and an unified equation is derived to predict the bursting forces in the anchorage zones with different load conditions.Meanwhile,a photelastic tests is conducted to visually reproduction the load path in rectangular anchorage zones.(4)According to the weakness of concrete in tension,a modified optimal criterion is proposed to develop STM using topology optimization methods.And then the principle of minimum strain energy of ties and maximum stiffness of the struts are proposed to determine the optimal layout ties in the STM.(5)Experimental testing on three typical regions(including concentric anchorage zones,multi anchorage zones and deep beams)are carried out to investigate the load transfer mechanism throughout the loading process.(6)The principle of stationary complementary energy is introduced into the traditional STM to generate the adaptive EPSTM at each load step automatically.And then the EPSTM are individually established for concentric anchorage zones,multi anchorage zones and deep beams,which can provide a consistent analysis of the behavior of D-regions.(7)By incorporating the bond stress-slip relation of the tension chord subjected to lateral pressure into the EPSTM,a simplified method is proposed to evaluate the maximum crack width in the typical D-regions.