The Complete Stress-strain Curve of Recycled Aggregate Concrete under Uniaxial Compression Loading

The mechanical performance of recycled aggregate concrete （RAC） is investigated. An experiment on the complete stress-strain curve under uniaxial compression loading of RAC is carried out. The experimental results indicate that the peak stress, peak strain, secant modulus of the peak point and original point increase with the strength grade of RAC enhanced. On the contrary, the residual stress of RAC decreases with the strength grade enhancing, and the failure of RAC is often broken at the interface between the recycled aggregate and the mortar matrix. Finally, the constitutive model of stress-strain model of RAC has been constituted, and the results from the constitutive model of stress-strain meet the experiment results very well.

Typical curve with G1 constraints for curve completion

This paper presents a novel algorithm for planar G1 interpolation using typical curves with monotonic curvature.The G1 interpolation problem is converted into a system of nonlinear equations and sufficient conditions are provided to check whether there is a solution.The proposed algorithm was applied to a curve completion task.The main advantages of the proposed method are its simple construction,compatibility with NURBS,and monotonic curvature.

On 3-Submanifolds of S3 Which Admit Complete Spanning Curve Systems

Let M be a compact connected 3-submanifold of the 3-sphere S^3 with one boundary component F such that there exists a collection of n pairwise disjoint connected orientable surfaces S = {S_1, ···, S_n} properly embedded in M, ?S = {?S_1, ···, ?S_n}is a complete curve system on F. We call S a complete surface system for M, and ?S a complete spanning curve system for M. In the present paper, the authors show that the equivalent classes of complete spanning curve systems for M are unique, that is, any complete spanning curve system for M is equivalent to ?S. As an application of the result,it is shown that the image of the natural homomorphism from the mapping class group M(M) to M(F) is a subgroup of the handlebody subgroup Hn.

Quantitative Evaluation of Rock Brittle Property Based on Energy Evolution and Its Application in Three Gorges Reservoir Area

Brittleness is of great significance for evaluating the mechanical properties of the slope rock in reservoir area and revealing the brittle failure mechanism of the rocks.Although a series of definitions of the brittleness and evaluation methods of brittleness index have been proposed,there is still lack of a widely recognized and remarkable standards in these aspects due to the differences in diagenetic process,depositional environment and mineral composition.The previous methods to quantitively estimate the rock brittleness based on energy balance analysis are summarized,which neglect multiple influencing factors of the rock brittleness,such as the weight of pre-peak or post-peak mechanical behaviors on the prediction performance of the brittleness index.Based on the typical curves about stress and strain,the relationships between the brittle failure behaviors and the energy evolutions are comprehensively analyzed,then a new method for assessing the brittleness is proposed.Based on prepeak brittleness index to represent brittle property at pre-peak stage and post-peak brittleness index to determine brittle characteristic at post-peak stage,a new brittleness index is established by additive synthesis method in consideration of the weight of brittleness indexes before and after peak strength,and either of the two brittleness indexes can be punished or compensated by setting different parameter values.The results indicate that the proposed brittleness index can represent the brittle change laws for different rock types whenα≤0.5,β≥0.5.When evaluating the brittleness of the slope rock in Three Gorges Reservoir(TGR)area,the results show that the rock brittleness in the slope affects the stability of the slope.Therefore,the novel evaluation method can provide reliable results,and the proposed brittleness index considering the energy evolution can be applied to assess the brittle property in the reservoir bank project.

DEVELOPMENT AND APPLICATIONS OF THE ELASTO-PLASTIC CELLULAR AUTOMATON

The paper presents the advancement and applications of the elasto-plastic cellular automaton （EPCA）, a simulator for rock mechanics and rock engineering. The most significant feature of EPCA lies in its ＇down-top＇ way of dealing with nonlinear behaviors of rocks. The theory, the basic idea and associated developments, including the definition of cellular automaton, the heterogeneous material model, constitutive relations, failure criteria, the post-yield softening scheme, the thermo-hydro-mechanical coupling process, are described. The applications are presented to show the ability of EPCA to model the rock failure process, fluid flow, heat transfer, and the coupled thermo-hydro-mechanical （THM） process etc.

Strength and Deformation of Axially Loaded Fiber-Reinforced Polymer Sheet Confined Concrete Columns

Experimental results of 29 axially loaded fiber-reinforced polymer sheet (FS) confined concrete columns and two reference plain concrete columns are introduced. Twenty four column specimens were confined with carbon fiber sheet (CFS) and five column specimens were hybrid confined with both CFS and glass fiber sheet (GFS). The influence of aspect ratio, FS material, initial axial force ratio, and FS confine-ment degree on the strength and deformation of columns were studied. Based on the experimental results, the equations of complete stress-strain curve of CFS confined concrete are proposed. These equations are suitable for the nonlinear analysis of square and rectangular section columns. Suggestions of applying FS to confine concrete columns are presented.