Papers by Author: Xiang Guo Wu

Abstract: The analysis of material variables and curing procedure design are the key techniques of UHPCC. Material variables include cement-water ratio, silica fume content, sand’s content and size, filling powder’s content and type. Based on the objective of compressive strength, UHPCC with compressive strength 180MPa was developed based on the influence analysis of material variables on its performances and the substitution of silica fume by lime stone powder. By the analysis of the influences of early curing method, initial time, duration time and high temperature curing, curing procedure design was proposed, i.e. early water curing at first after 24 hours of casting and then high temperature steam curing. Based the simplified constitutive relation of UHPCC, the ultimate flexural of UHPCC hybrid girder was analyzed. This paper can be a basis of UHPCC-NC hybrid structure analysis.

Abstract: Direct uniaxial tension test of ultra high performance cementitious composites I shape specimens have been investigated in this paper. A nonlinear analytical model based on continuum damage mechanics is developed to characterize tensile stress-strain constitutive response of UHPCC. Basic governing equations of damage evolution and material constitutive relation are established considering random damage which conforms to a modified Weibull type distribution proposed in this paper. Calculation suggests that Weibull distribution can describe damage evolution of UHPCC and predict the constitutive relation and damage evolution equation.

Abstract: An R-curve formula for ultra high performance cementitious composites is derived in this paper. The fracture mechanics based on R-curve is used to predict the load-deflection relation of ultra high performance cementitious composites. The reductions of stress intensity factor and CTOD by steel fiber reinforcement are assumed as conforming linear distribution along crack propagation. The effective numbers of steel fiber on unit area based uniform distribution is used here. Results of the theoretical predictions show a good agreement with test results of three point bending beam of UHPCC. The modified R-curve formula for UHPCC can be a reference for future study of fracture performances of UHPCC.

Abstract: This paper concerns the theoretical research of shear failure load of steel fiber reinforced ultra high performance cement composites (SFR-UHPCC) beam. Based on test investigation, an analytical model of prestressed SFR-UHPCC beam is constituted. Two formulae of ultimate failure load, i.e. the upper bound and the lower bound of shear loading capacity, all have been obtained according to the limit analysis of concrete plasticity. In the process of upper bound analysis, uniform distribution of steel fiber has been assumed, and virtual work induced by steel fiber has been divided into two parts, i.e. pulling-out virtual work and debonding virtual work. Five coefficients are introduced considering some defects. Twelve SFR-UHPCC beams with three kinds of shear span ratio i.e. 2.7, 5.6 and 8.5 are tested and compared with the results from the proposed equations.