Program Development And Research On Calculation Method Of Bending Capacity For Preflexed Composite Beam

It has beam more than 70 years since the concept of preflexed beam was first put forward by Belgian scholar A.Lipski in 1949.Although the relevant theoretical and engineering research on preflexed composite beam in China is about 40 years later than that in foreign countries,its development in China has grown rapidly.In October 2018,the national standard “Technical standard for preflexed composite beam bridges” issued by the Ministry of housing and urban rural development of China came into operation.However,calculating the Untimate Limit States and stress by the method in Technical standard is still cumbersome,and many trial calcutiongs are often needed in the design.Therefore,it is necessary to restudy the calcution method of the bending capacity for preflexed composite beam and develop the design and checking special program for preflexed composite beam bridges which could promote this type of bridges further.In this paper,the following researches have been done:(1)Based on the plastic theory,the plastic calculation method of bending capacity for preflexed composite beam is deduced,and three simplified calculation methods are put forward.The theorical capacity of 7 experimental flexural failure beams is calculated by the three simplified calculation methods,the simplified calculation method 1 is finally determined,which is assumed that discard the bearing capacity of elastic-core in the elastoplastic calculation method,as the most suitable simplified calculation method of preflexed composite beam.(2)The flexural capacity of 7 experimental flexural failure beams is calculated by the elastoplastic method,the deduced plastic method and the simplified calculation method.Nonlinear finite element analysis models were established by general finite element analysis software Abaqus and all results were compared with test results for verifying the safety and accuracy of the new calculation method.The results show the proposed simplified calculation method of bending capacity is simpler than the elastoplastic method and the plastic method which can be used in the calculation of cross-section bending capacity for highway bridges.Based on the above research,an example of preflex simply supported beam bridge is given which use the proposed method to calculate the ultimate bending capacity for practical project.(3)Based on the Technical standard and combined with the calculation requirements and function realization of the preflexed composite beam design and checking system(PBS system),the ideas and formula derivation of the contents including section geometric characteristics calculation,internal force calculation of any section,specific application of elastic design method and so on are sorted out and summarized and the applicable conditions are given based the summary.(4)On basis of the design and checking calcution requirements of preflexed composite beam bridge,PBS system is developed by Visual C++ in Qt Creator which can be used for the design and checking of highway preflexed composite beam structure and is suitable for the calculation of simply supported equal section and variable section beam.PBS system also can distinguish engineering beam and experimental beam.And Two examples are used to verify the correctness of PBS system operation calculation.The results show that the calculation of internal force,the calculation of section,the calculation of bearing capacity limit state and other modules of PBS system run well,the functions can be realized,and the correctness of system calculation can be ensured.The interface is beautiful,intuitive and user-friendly.(5)On basis of the existing standard design of preflexed composite beam,general drawing of highway bridge and the Japanese standard design set of preflexed composite beam bridge,the standard beam of preflexed composite beam bridge is designed in detail and checked by PBS system.Finally,15 standard spans are determined,each span corresponds to two bridge widths,and each bridge width corresponds to three beam heights,which include 6sets of standard sizes and 90 standard beam sizes total,the standard beam is imported into the PBS system for reference.