Applied Mechanics and Materials Vols. 438-439

Abstract: In allusion to the management characteristics of the cement laboratory samples, this paper conducts introduction and comparative analysis on such four kinds of identification as inspection organization, traditional cement sample identification of corporate laboratory, paper-electronic tags and wireless monitoring devices. It shows that wireless monitoring devices are superior to the traditional sample identification and paper-electronic tags, and can achieve intelligent management of cement samples ensuring objective and fair inspection data.

Abstract: Fracture toughness J_C is sensitive to the characteristic of the material itself, as an effective indicator to appreciate the fracture resistance of the asphalt mixtures, is adopted by more and more researchers. The Semi-Circular Bending Test (SCB) can evaluate the fracture resistance of asphalt mixtures with different kinds of molding means. But currently, the fracture toughness J_C is measured by multi specimens (at least two), the experimental consumption is high, the single specimen calculation formula didnt appear. Using Digital Image Correlation Method (DICM) can compute the J-contour integral of a single specimen, compared with the results obtained from multi specimens, the repeatability is better, the accuracy is higher. Test and analytic results show that the DICM provide a new approach to study and investigate the fracture toughness J_C.

Abstract: The key of ground penetrating radars application lies in the calculation of dielectric coefficient. The pavement materials are inhomogeneous medium in fact, the particle surface can induce the scatter and diffraction of electromagnetic wave. The inhomogeneous dielectricity can change the characteristics of reflected wave. It may even cause background noise of reflected signal, which will lead to mistakes in signal interpretation. Therefore it is necessary to analyze the inhomogeneous dielectric coefficients by GPR. This paper proposes the solutions of inverse analysis for inhomogeneous dielectric coefficients of pavement materials used GPR data. Two examples are given to assess the validity of genetic algorithms in inversion of pavement materials inhomogeneous dielectricity. The results show that genetic algorithm can converge into true solutions well. The backcalculated inhomogeneous dielectric coefficients can help to evaluate pavement properties further.

Abstract: Novel and efficient structural and material designs can be realized by topology optimization that is capable of maximizing the performance of structural systems under given constraints. The bi-directional evolutionary structural optimization (BESO) method has been developed into an effective tool for topology optimization of load-bearing structures and materials. The latest advances of BESO are aimed at expanding its practical applications to a wider range of structural systems on both macro and micro scales. This paper presents recent developments of BESO for optimal design problems of a variety of structural systems ranging from buildings of large scales to materials of micro scales. Selected applications are introduced to demonstrate the capability of BESO. Examples presented in this paper are based on research and industrial projects of the Centre for Innovative Structures and Materials (http://www.rmit.edu.au/research/cism) at RMIT University.

Abstract: Different from the independent optimization of macrostructures or materials, a two-scale topology optimization algorithm is developed in this paper based on the bi-directional evolutionary structural optimization (BESO) method for concurrently designing a macrostructure and its composite microstructure. The objective is to minimize the mean compliance of the structure which is composed of a two-phase composite. The effective properties of the composite are calculated through the homogenization method and integrated into the finite element analysis of the structure. Sensitivity analysis for the structure and microstructure is conducted by the adjoint method. Based on the derived sensitivity numbers, the BESO approach is applied for iteratively updating the topologies for both the structure at the macro level and the microstructure of composite at the micro level. Numerical examples are presented to validate the effectiveness of the proposed optimization algorithm.

Abstract: The goal of this paper is to investigate the efficiency of domestic Rain Water Harvesting (RWH) tank to reduce the inflow discharge to stormwater sewer systems, which intends to be an option to increase urban resilience to climate change impacts. A dimensionless methodology developed based on a water balance model at daily temporal scale was applied to determine both the obtainable water saving due to the use of rain water for toilet flushing (i.e. reduce the use of portable water) and meanwhile reduce stormwater volumes discharging to sewer systems by the tank storage. The methodology and a RWH tank system was evaluated applying the daily rainfall data obtained in two met-stations of Blindern in Oslo and Rygge in Fredrikstad, South Norway. Results show, for all the considered scenarios in the two case studies that the use of the rainwater storage tank can provide significant reduction of water volume discharges to the storm water sewer, accordingly the resulting damages during the extreme events will be reduced.

Abstract: Advanced processing techniques for the application of Fibre Reinforced Polymer (FRP) materials to repair concrete structures include the adoption of a vacuum consolidation process coupled with heat and/or resin injection to improve the curing process, bond strength and speed of application. The vacuum can contribute to the penetration of the resin into the surface around the exposed aggregates in order to achieve higher bond in strengthened elements. Since, debonding of FRP materials from the substrate is a brittle failure, it is essential to study this phenomenon and propose significant ways to improve the behaviour of the bondline. In this article, the interfacial bond behaviour of FRP laminates attached to concrete in the presence of vacuum and heat/resin injection is studied. The results of single lap shear tests have been utilized to investigate the capability of this system in strengthening of concrete elements. In this regard, several FRP-bonded concrete prisms will be examined in a single lap shear test set-up. Further, the effects of bondline thickness on the bond performance of adhesively bonded joints are studied.

Abstract: Based on the tested data, the ANSYS finite element analysis software was adopted to establish the finite element model for the concrete beam nonlinear analysis.The finite element models were developed using 3-D solid element for concrete and shell element for the Carbon Fiber Reinforced Ploymer (CFRP) sheet. The results obtained from the ANSYS were compared with the experimental data for two strengthened beams with different thickness CFRP sheet. The comparisons were made for the curves of load-midspan deflection, yielding load and ultimate load. Models were calculated at the same condition as the experimental beams. Two reinforced beams strengthened with CFRP sheet were calculated in four-point bending. The load-deflection curves from the finite element analysis agree well with the experimental results. The average difference in ultimate load for two cases is 5.5%.

Abstract: Eleven pre-cracking reinforced concrete T-beams were strengthened with U-stirrups and longitudinal sheets of CFRP, the main parameters were the width, layer and space of U-stirrups of CFRP. The tests for shear resistance of the beams were carried out to measure the diagonal crack development and crack width, mid-span deflection, CFRP strain and ultimate resistance. Compared with the reference beam without strengthening, the diagonal cracks were effectively restrained and the shear resistances of the beams were also strengthened by the U-stirrups of CFRP. However, the shear resistance increment of the beams were not in direct proportion with the amount of CFRP sheet characterized by the width, layer and space of U-stirrups, as the strengthening effect is obviously influenced by the bond quality and the anchorage reliability of the U-stirrups. When strengthened with one layer, the shear resistance of the beam was enhanced largely by the wider sheet. When strengthened with two layers, the enhancement of shear resistance was weakened with the increasing width of sheets.

Abstract: A large impaired reinforced concrete beam with cracks was strengthened under self-weight action by the externally bonded steel frame composed with bottom steel plate and side hoop steel belts. The normal service loading behaviors of this beam were tested to verify the effectiveness of this strengthening method specified in current Chinese design code. Based on the analyses of test results, it can be concluded that: the deformation of flexural cross section of this beam fitted the assumption of plain cross section, the steel plate could effectively enhance the flexural stiffness and decrease the deflection of this beam, no new cracks appeared under the normal service loads, the cracks at bottom of this beam were more confined by the steel frame than those at web zone. Therefore, other measure should be taken to avoid the opening of web cracks.