The influence of structural spatial constraints on the flexural performance of reinforced concrete beams
To investigate the influence of structural spatial constraints on the yielding mechanism of frame structures,reinforced concrete(RC)beam models with different boundary conditions were established using a multiscale numerical method.A quantitative analysis was conducted on the influence of end constraints and the addition of cast-in-place floor slabs on the stiffness and flexural capacity of RC frame beams,i.e.,the peak bending moment that the specimen can withstand.The influence mechanisms of end constraints and cast-in-place floor slabs on the bending mechanism of RC beams were revealed.Furthermore,comparative analyses were conducted with the calculated flexural capacity of various national standards.The results indicate that structural spatial constraints affect the failure modes of RC frame beams.The stiffness and flexural capacity of fixed-end beams are significantly higher than those of simply supported beams,with the flexural capacity and stiffness of fixed-end beams reaching up to 3.06 and 4.10 times those of simply supported beams,respective-ly.The addition of cast-in-place floor slabs significantly enhances the flexural capacity and stiffness of the beams.National standards can accurately calculate the flexural capacity of simply supported beams.However,for fixed-end beams and floor beams,the calculated flexural capacity is extremely conservative.For example,the simulated values of fexural capacity for the fixed-end beam with a shear span ratio of 5.0 are 6.25,6.76 and 6.06 times the calculated values according to Chinese,American,and Canadian standards,respectively.
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