Research On Structure Property Related Problems Of Single-Plane Through Continuous Beam-Arch Combination Bridge

With the development of society,the significance of bridge structure is no longer just the practical value of traffic,the perfect combination of science and art and humanity has become a new concept of modem bridge design.The single-plane through continuous beam-arch combination bridge developed on the basis of the traditional continuous beam bridge and arch bridge,is a new and unique type of bridge structure.It has many advantages such as beautiful configuration,open view,reasonable force and strong adaptability,so it has great development prospects and space.In this paper,two single-plane through continuous beam-arch combination bridges are selected as the research background,one is the Gangou Bridge in Liaoning province with the longest main span of this type bridge at present,and the other is the Sand River Single Rib Arch Bridge in Yingkou city,which is similar to the Gangou Bridge in configuration.Focus on some structure property related problems of the singe-plane through continuous beam-arch combination bridge,the main research work are conducted as follows:(1)Based on the energy variational principle,a practical calculation for lateral stability of single-plane through continuous beam-arch combination bridge is proposed,by adding the side span effect on basis of the lateral stability analysis of simple beam-arch combination bridge.The practical formular is verified to be practical and reliable by comparing with the results of the finite element method.Based on the stability theory,considering the geometrical and material nonlinearity,the ultimate bearing capacity of Gangou Bridge is analyzed by nonlinear finite element method,and the results show that nonlinear elastoplastic analysis is necessary to accurately evaluate the stability of this kind of bridge.Then,the effects of some factors on the ultimate bearing capacity of the structure are also discussed,and the results show that:the live load distribution has a great influence;different mode and size of initial geometrical imperfections has different effects;the side span effect is not obvious;and the steel-concrete connection can improve the stability of the structure effectively when its length is reasonable.(2)Based on the assumption of filmy suspender forces,the through continuous beam-arch combination bridge is divided into beam-arch body and suspenders,and then the reaction force of the end support is calculated by the force method.The critical side-to main-span ratios are derived according to the end support can not be disengaged under the two critical cases,one case is the dead load,and the other case is the dead load and the full live load on the main span.The ranges of side-to main-span ratio under different conditions are investigated.The results show that:the reasonable side-to main-span ratio of the through continuous beam-arch combination bridge is related to the relative stiffness of the arch,the beam and the suspender,and it is smaller and more flexible than that of the continuous beam bridge,because of strengthening and adjustment of the arch to the continuous beam;by tensioning suspender and side span surcharge,the side-to main-span ratio of the through continuous beam-arch combination bridge can be further reduced,then the cost is saved and the bridge can adapt to the topography fully.(3)Assuming that the parabola is the reasonable arch axis shape,the theoretical limit span of the single-plane through continuous beam-arch combination bridge is derived,considering both the material strength and the lateral stability of the structure.And the limit spans of three cases,those have different combination of the current common materials,are discussed in detail.The study show that:the theoretical limit span of the bridge with reinforced concrete arch rib and prestressed reinforced concrete beam or with steel arch rib and prestressed reinforced concrete beam,is controlled by its material strength,and the limit span increases with the increase of the rise-span ratio;when the rise-span ratio is less than 1/7,the theoretical limit span of the bridge with steel arch rib and steel beam is controlled by its material strength,otherwise,it is determined by the structural stability;the above conclusions can offer reference in the conceptual design phase of this type bridge.(4)The single-plane through continuous beam-arch hybrid bridge,adopting steel arch rib and prestressed reinforced concrete beam,shows good economic indexes and overcrossing capacity.The steel-concrete joint connecting the arch rib and the beam is a key part of the structure,and the perfobond rib shear connector,as the main transmission component,is the core of the steel-concrete connection design.Firstly,the push-out tests that are suitable for hybrid structures are carried out to study the behaviour of perfobond rib shear connector,then the nonlinear finite element method is used to simulate the push-out tests.By comparing with the test results,the finite element method is verified to be feasible and effevtive for studing the performance of perfobond rib shear connector under serviceability limit state.On the basis of the mechanical properties of single perfobond rib shear connector,the performance parameters of perfobond rib shear connector group under serviceability limit state are determined,then the force transmission characteristics of 3D perfobond rib shear connector groups are studied by using the nonlinear finite element numerical simulation experiment,it is shown that the "connector group effect" is mainly the force non-uniformity of the multi-row connector group along the force transmission direction,subsequently,the reduction coefficient of the design bearing capacity and the equivalent number of rows are proposed,also the relationship between the equivalent number of rows and the actual number of rows is obtained.Based on the above research,the design method of perfobond rib shear connector group in hybrid structures is proposed finally,and it is verified to be reliable by the practical engineering application and the test of the connection.Lastly,the behavior of the hybrid connectors that contain perfobond rib shear connectors and stud connectors is preliminarily discussed.