دانلود رایگان مقاله انگلیسی بررسی عددی در پاسخ های لرزه ای سازه های بتنی با توجه به تاثیر میزان فشار - الزویر 2018

abstract

The strain rate effect can inevitably impact the seismic responses of reinforced concrete (RC) structures because the dynamic properties of RC materials under earthquakes change significantly with the timevarying loading rates. This paper carries out systematic experimental tests and numerical simulations to investigate the effects of strain rates on the seismic responses of RC structures. The dynamic properties of micro-concrete and iron wire used in the shaking table specimen are firstly tested under seismic loading rates and the corresponding dynamic increase factors (DIFs) are estimated based on the test data. The shaking table test of a 1/5 scaled RC structure is performed to realistically reproduce the dynamic responses of RC structures with strain rate effect. Moreover, a three-dimensional rate-dependent fiber beam-column element is developed in the ABAQUS platform to establish the finite element (FE) model of the shaking table specimen, in which the estimated DIFs for the key parameters of micro-concrete and iron wire are employed to consider the strain rate effect. Besides, the rate-independent structural FE model is also developed using the traditional beam-column element with the static RC material constitutive models. The numerical results demonstrate that the seismic responses of RC structures are overestimated when the strain rate effect is neglected. As validated by the experimental data of the shaking table test, the FE model developed using the proposed rate-dependent fiber beam-column element can yield better structural seismic response predictions in comparison with the rate-independent model.

6. Conclusions

In the present study, the influence of strain rate effect on the seismic responses of RC structures is comprehensively investigated through experimental tests and numerical simulations. The key findings are summarized as follows:

(1) The compressive strength and Young’s modulus of the micro-concrete, as well as the yield strength and tensile ultimate strength of iron wire are all enhanced with the increasing loading rate. The DIFs for these key material parameters are estimated based on the experimental data of the dynamic loading tests.

(2) The strain rates of column and beam members in the shaking table specimen magnify with the input ground motion intensity. The peak strain rates of the columns are much higher than those of the beams. The effect of strain rate should not be neglected in the seismic response predictions of RC structures, especially under the excitations of strong earthquakes.

(3) It is validated by the shaking table test that the proposed rate-dependent fiber beam-column element model can more reasonably and accurately simulate the seismic responses of RC structures as compared with the traditional beamcolumn elements with static RC material constitutive models. The proposed numerical simulation method can yield precise seismic performance predictions of RC structures and provide beneficial recommendation and supplement for the seismic design codes of RC buildings.

(4) More investigations are needed to examine the effect of strain rate on the seismic responses of other types of RC structures, especially high-rise buildings. Moreover, the seismic vulnerability analyses of RC structures should be carried out in the future studies, in which the influence of ratedependent properties of RC materials can be evaluated under a large number of input earthquake ground motions.