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Seismic performance of prestressed concrete stand structure supporting retractable steel roof
Yiyi CHEN, Dazhao ZHANG, Weichen XUE, Wensheng LU
Front Arch Civil Eng Chin. 2009, 3 (2): 117-124.
https://doi.org/10.1007/s11709-009-0024-3
The seismic behavior of a structural system composed of pre-stressed concrete stand supporting a retractable steel roof was studied, which is typically based on the prototype of engineering project of Shanghai Qizhong Tennis Center. By elasto-plastic finite element analysis and shaking table test, the following were investigated: the effects of roof configurations in opening and closing, the effect of pre-stress on the structural seismic response, and the failure mechanism of the spatial stand frame systems featured with circularly arranged columns and inverse-cone type stands. It was found that the roof status has great effect on the natural period, vibration modes, and seismic response of the whole structure, the stand response to horizontal seismic excitation is stronger in roof opening configuration than in closing state, and the response mode is dominantly translational rather than rotational, though the stand is characterized by its fundamentally torsional vibration mode. The study indicated that the pre-stressed inverse-cone stands can keep the system from global side-sway collapse under gravity loads, even in the case that most columns loose moment capacity.
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Behavior of steel fiber–reinforced high-strength concrete at medium strain rate
Chujie JIAO, Wei SUN, Shi HUAN, Guoping JIANG
Front Arch Civil Eng Chin. 2009, 3 (2): 131-136.
https://doi.org/10.1007/s11709-009-0027-0
Impact compression experiments for the steel fiber–reinforced high-strength concrete (SFRHSC) at medium strain rate were conducted using the split Hopkinson press bar (SHPB) testing method. The volume fractions of steel fibers of SFRHSC were between 0 and 3%. The experimental results showed that, when the strain rate increased from threshold value to 90 s-1, the maximum stress of SFRHSC increased about 30%, the elastic modulus of SFRHSC increased about 50%, and the increase in the peak strain of SFRHSC was 2-3 times of that in the matrix specimen. The strength and toughness of the matrix were improved remarkably because of the superposition effect of the aggregate high-strength matrix and steel fiber high-strength matrix. As a result, under impact loading, cracks developed in the SFRHSC specimen, but the overall shape of the specimen remained virtually unchanged. However, under similar impact loading, the matrix specimens were almost broken into small pieces.
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Time-domain and frequency-domain approaches to identification of bridge flutter derivatives
Zhengqing CHEN
Front Arch Civil Eng Chin. 2009, 3 (2): 173-179.
https://doi.org/10.1007/s11709-009-0034-1
Flutter derivatives are essential for flutter analysis of long-span bridges, and they are generally identified from the vibration testing data of a sectional model suspended in a wind tunnel. Making use of the forced vibration testing data of three sectional models, namely, a thin-plate model, a nearly streamlined model, and a bluff-body model, a comparative study was made to identify the flutter derivatives of each model by using a time-domain method and a frequency-domain method. It was shown that all the flutter derivatives of the thin-plate model identified with the frequency-domain method and time-domain method, respectively, agree very well. Moreover, some of the flutter derivatives of each of the other two models identified with the two methods deviate to some extent. More precisely, the frequency-domain method usually results in smooth curves of the flutter derivatives. The formulation of time-domain method makes the identification results of flutter derivatives relatively sensitive to the signal phase lag between vibration state vector and aerodynamic forces and also prone to be disturbed by noise and nonlinearity.
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Effect of natural resource on improving indoor thermal environment in Chongqing
Yong DING, Baizhan LI, Qing LUO, Hong LIU, Meng LIU
Front Arch Civil Eng Chin. 2009, 3 (2): 211-218.
https://doi.org/10.1007/s11709-009-0018-1
This paper analyzes the potential of natural resources to improve the indoor thermal environment in Chongqing through the statistical analysis of natural resources including solar energy, wind, water, and earth, etc. The building form, systems, and principle of usage of natural resources are briefly analyzed through the building site decision, building form design, and computer simulation, which will be the real reference for the design of building energy efficiency.
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Experimental study on pile-end post-grouting piles for super-large bridge pile foundations
Weiming GONG, Guoliang DAI, Haowen ZHANG
Front Arch Civil Eng Chin. 2009, 3 (2): 228-233.
https://doi.org/10.1007/s11709-009-0019-0
The application of pile-end post-grouting piles for super-large bridge pile foundations in some important projects was introduced in this paper. There are totally 21 test piles. The maximum pile diameter varies from 2.5 m to 3 m, and the maximum length is 125 m; the bearing capacity of the post-grouting piles is over ten thousands tons. Based on the test results, the bearing capacity, displacement, and bearing characteristic before and after grouting were analyzed. The results show that the bearing capacity of the piles are increased in different degrees after grouting although the technical parameters, including the patterns of grouting pipes, pressure, dosages of cement, duration of grouting lasting time, are different. However, the obtained values are very discrete. In addition, the calculation formula for the post-grouting piles under specified grouting condition was deduced based on the statistics analysis results of 57 test piles. The research results have been applied in the design of bridge foundation.
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