Preliminary Study On A New Direct Displacement Based Design (NDDBD) Method

Direct displacement based design(DDBD) is an conceptually advanced method for seismic design of structures.Over the past two decades, though scholars have done a lot of research on DDBD and achieved many key results, DDBD still far from being widely used in engineering practice. One of the important reasons is that the displacement response of structure designed by DDBD can't be controlled accurately.Through summarizing the basic theory of DDBD, author found the essential connection between DDBD theory and Pushover theory,which they are both based on the theory of substitute structure. Based on this connection,“Double Substitute Structure Theory” is established,and the displacement target is effectively connected to the base shear target, which lays a foundation for accurately controlling structure's displacement response.What's more, this paper proposed the cross section design method, which aimed to quantitatively consider the requirement of bearing capacity and ductility.Based on the porposed cross section design method, preliminarily study on actively controling structure's energy dissipation mechanism is carried out.Then a new direct displacement based design(NDDBD) method aimed to control the displacement response of structure precisely was proposed, through the combining of “Double Substitute Structure Theory” and the basic process of DDBD based on relateice reliability concept which established by author's team. Finally, the feasibility and validity of the NDDBD method are tested, through 8 frames.The main conclusions of this paper are as follows:(1) The proposed NDDBD method in this paper can accurately control the story drift ratios response of structures under rare earthquake(the maximum error between the actual value and the target of the story drift ratios is less than 5%).(2) The “Double Substitute Structure Theory” is able to calculate the target value of the base shear force, corresponding to the given story drift ratios, with considering the characteristics of structure's elastic-plastic response.(3) It's feasible to quantitatively consider the requirement of bearing capacity and ductility, in cross section design process.(4) The algorithm actively controling structure's energy dissipation mechanism is feasible, which can control the maximum value of the curvature ductility for columns in each story well.The main innovation of this paper are as follows:(1) The “Double Substitute Structure Theory” is established.Based on this theory,the displacement target is effectively connected to the base shear target, which lays a foundation for accurately controlling structure's displacement response.(2) A new direct displacement based design(NDDBD) method was proposed,which can control the story drift ratios response of structures under rare earthquake.(3) The cross section design method which aimed to quantitatively consider the requirement of bearing capacity and ductility is proposed.What's more,efforts on actively controling structure's energy dissipation mechanism is made.