| Steel reinforced concrete(SRC for short)beams and steel reinforced ultra-high performance concrete(SRUHPC for short)beams had been used in a number of applications in practical engineering.At present,there were many study results on their flexural strength calculation methods,but the calculation results of different methods varied widely and there were obvious controversies.Therefore,using experimental research,theoretical analysis and other methods,based on the collection of existing research data,it was proposed to carry out further research on the flexural performance of rectangular section SRC beams and SRUHPC beams.The experimentally validated finite element models were used for parameter expansion analysis in conjunction with the actual engineering situation.The applicability of the proposed calculation method was investigated to provide a theoretical basis for its popularisation and application in practical engineering.The main work and findings of this study were as follows:(1)The methods from the established codes and paper were used to calculate the flexural strength of the 51 SRC specimens collected.It was found that there were some deviations between the calculated values of the existing method and the test values.Based on the reasons for the errors of the existing methods and theoretical analysis,the flexural strength calculation method of SRC beams was proposed,and the flexural strength of 51 specimens and 253 finite element analysis models were calculated.The results showed that the mean values of the calculated values of the proposed method were 0.953 and 0.970,respectively,and the variances were 0.015 and 0.007,respectively.It could be seen that the calculation accuracy of the proposed calculation method was better than the collected codes and paper calculation methods,and had higher calculation accuracy.(2)Flexural tests were carried out on five SRUHPC beams and one reinforced ultra-high performance concrete(UHPC for short)beam,and the results showed that: the specimens all exhibited balanced failure;the reinforced UHPC beam specimen exhibited UHPC crushed in the compressive zone after yielding of the tensile longitudinal bars;the SRUHPC beam specimens exhibited part of the steel beam and longitudinal bars successively yielded,followed by the UHPC being crushed in the compressive zone;the steel beam,reinforcement and UHPC in the SRUHPC beam specimens could work well together until the specimens were damaged,and the longitudinal strain in each part along the section height was basically in accordance with the plane section assumption.(3)The flexural strength and deflection of the SRUHPC specimens were calculated using the method from the established papers.It was found that there were some deviations between the calculated values of the established method and the test values.Combining the test results with the theoretical analysis,the method of calculating the flexural strength and immediate stiffness of SRUHPC beams was proposed,and the flexural strength of 21 specimens,111 finite element models and the deflection of 13 specimens were calculated,the results showed that: the mean value of the ratio of the calculated value to the test value and the finite element calculated value for the proposed flexural strength calculation method was 0.972 and 1.035,respectively,with a variance of 0.009 and 0.002,respectively;the mean value of the ratio of the calculated value to the test value for the proposed immediate stiffness calculation method was 1.041,with a variance of 0.017.The calculation accuracy of the proposed method was better than that of the existing paper,and had a high calculation accuracy.(4)The effects of various parameters on the flexural performance of SRUHPC beams had been analysed.The addition of steel beam to the reinforced UHPC beam could significantly improve the flexural strength,stiffness and crack resistance of the beam.Under the same load,the strain and strain development rate of the tensile longitudinal bars,UHPC and steel beam of the built-in H-beam specimen were smaller than those of the built-in I-beam and T-beam specimens,showed that the placement of the top and bottom flanges helped to further improve the flexural performance of the beam.The placement of the studs on the side of the steel beam could reduce the slippage between the UHPC and the steel beam,thus indirectly improving the crack resistance of the specimen. |
