Advanced Materials Research Vols. 163-167

Abstract: . It is possible to quantify the damage to reinforced concrete members under cyclic loading through a nondimensional parameter known as a “damage index”. The damage index can be either a global damage index for the total structure, or a local damage index for the element level. In this paper, a new damage model termed “equivalent ductility damage model” has been suggested for evaluation of the damage index, which is consistent with accepted definitions of ductility. Substructure method was applied to verify the suggested new damage model. A total of 3 identical half-scale reinforced concrete columns were tested under variable amplitude cyclic loading up to the ultimate failure of the specimens. The imposed displacement histories were obtained from analytical simulations of the model column subjected to a series of earthquakes. Test observations indicate that the proposed model predicts 100 percent damage at the ultimate failure state of the element. The proposed damage index model can be extended to other structural elements, such as shear walls, beams, beam-column junctions, etc.

Abstract: Considering the relationship of displacement and turn angle in anchorages and deviators between the externally prestressed steel and concrete beam under the action of load in simply supported externally prestrressed beam, equations on solving the incremental force in externally prestressed steel are established. The presented novel approach and the train of thought can be easily extended to analyze time-dependent effect for externally prestressed beams. The example shows that the theoretical values based on the presented formulae are agreeable with the results obtained by other methods.

Abstract: The transient temperature field and creep of concrete surrounding a spiral case are analyzed with a three-dimensional method, based on ABAQUS. The mechanism of hydration heat and cooling pipes on temperature is studied. The distribution of temperature with construction is given. The effect of temperature on gap between steel liner and concrete is researched. It is concluded that the influence of the measure parameters and temperature is indispensable.

Abstract: To study bilateral shear strength of rectangular frame column (RFC) with different stirrup area on two principal axis, 12 rectangular frame columns including 5 columns without stirrup and 7 columns with stirrup were tested. The analytical results indicated that the relationship of shear strength between two principal axes of RFC without stirrup could be approximately described as ellipse, and stirrup stress on two principal axes is independent. The oblique shear strength is less than the resultant force calculated by unilateral shear strength formula offered by Code for Design of Reinforced Concrete Structure. The reason for this is shear strength contributed by concrete is considered iteratively on two axes. Based on truss model and the above conclusion, a reduced coefficient is introduced to calculate the bilateral shear strength offered by concrete and the axial force, and then a formula is proposed to calculate bilateral shear strength of RFC with different stirrup area on two principal axes. Comparison between the calculation and experimental results shows the formula is feasible and safe.

Abstract: According to the construction site of Zibo athlete apartment and the relevant standards, the structure constitution of the composite floor system, construction method and the problems that should be paid attention during construction were introduced in detail. Reinforced concrete composite floor system of superimposing box and net beam consisted of small prefabricated components- two reinforced concrete plates locating at top and bottom of the box and the cast-in-site concrete beam. This composite floor system was a whole structure of beam and plate combination, with a continuous box section. The superimposing box undertook the loads action together with the rib beam. The floor system has many advantages such as the industrial prefabricated components, stable construction quality, reduction of labor intensity in construction site and the environmental pollution, and the integral structure.

Abstract: Reinforced concrete frame-shear wall structure is a double resistance to lateral force system, in which the frames and shear walls work cooperatively and the distributive rule of the earthquake force varies with different earthquake actions. To ensure the frames bear the increasing earthquake shear force and play a role of second defense line due to the internal force re-distribution after the stiffness degradation of shear walls, the elastic design earthquake shear force of the frames should be adjusted. However the adjustment measures applied in Chinese code are proposed according to the design experiences of engineers and lack of the theoretical and computational analytical basis. Moreover, there is a dispute about ignoring the rule of the shear force redistribution along storey or not, it is necessary to further evaluate the rationality of the measures in the code. In this paper, based on a 3-D precise nonlinear frame-shear wall structure analysis model, the re-distributive rule of the internal force under strong earthquake was studied and the adjustment measures of earthquake force in the frames were checked. Finally, some design suggestions were proposed.

Abstract: Shrinkage and creep are the inherent properties of concrete bridge. According to Latin Hypercube Sampling method (LHS) and concrete bridge shrinkage and creep uncertainty parameters, this paper promotes stochastic finite element method based on LHS for concrete bridge shrinkage and creep uncertainty analysis in ANSYS random analysis model. Based on this stochastic finite element method, internal force and long-term deformation of a continuous rigid frame bridge with density gradient concrete is analyzed. Result show, internal force and deformation of continuous rigid frame bridge after completing are reasonable and satisfy Code requirement, and are various in previous 3 years at service stage and trend to steadily after 3 years. Research result provides theoretical basis for shrinkage and creep uncertainty further analysis in concrete bridge.

Abstract: Multi-ribbed frame grid (hereinafter referred to as MRFG) is the important part of Multi-ribbed composite wall and consisted of outer frame and ribbed grid. The reinforcement in column of outer frame is the main influence factor on the performance of MRFG. In this study, a MRFG specimen under laterally cyclic and axial loading in literature is numerically simulated with 5 kinds of different reinforcement ratio in column of outer frame, by a general finite element software and user-defined material model. The influence of different reinforcement ratio in column of outer frame on the mechanical behavior of MRFG has been discussed.

Abstract: On the basis of diffusion mechanism of crack and stress-strain of concrete, the mathematical differential formula and the pure theoretical model of stress-strain complete process of concrete are established. It is shown that stress-strain relationship of concrete is affected by Hooke’s law and diffusion mechanism of crack, and the law of which can be expressed by an exponential formula.

Abstract: Various analytical approaches to performance-based seismic design are in development. Based on the current Chinese seismic codes，elastic capacity calculation under frequent earthquake and ductile details of seismic design shall be performed for whether seismic design of new buildings or seismic evaluation of existing buildings to satisfy the seismic fortification criterion “no damage under frequent earthquake, repairable under fortification earthquake, no collapse under severe earthquake”. However, for some special buildings which dissatisfy with the requirements of current building codes, elastic capacity calculation under frequent earthquake is obviously not enough. In this paper, the advanced performance-based seismic theory is introduced to solve the problems of seismic evaluation and strengthening for existing reinforced concrete structures, in which story drift ratio and deformation of components are used as performance targets. By combining the features of Chinese seismic codes, a set of performance-based seismic design method is established for reinforced concrete structures. Different calculation methods relevant to different seismic fortification criterions are adopted in the proposed method, which solve the problems of seismic evaluation for reinforced concrete structures.