Papers by Author: Hong Chang Qu

Abstract: The urban renewal is not a simple reconstruction by demolition for the urban material substances, but its a kind of the artificial behavior to promote solution of various problems which can affect and hinder the urban development and obtain sustainable development. The renewal project planning of the industrial cities is a continuous, dynamic, long-term development process, in this process, emphasizing the application of the optimization of the forward-looking, dynamic and comprehensive renewal planning system has an important guiding significance on the sustainable development of the cities.

Abstract: The rapid development and expansion speed in the renewal of the China’s industrial cities are not suited to the current situations of large energy consumption of the existing buildings, these current situations causes the urban environment and resources to be destroyed and the sustainable development of cities to be severely hampered. To solve these problems, a variety of resources for urban renewal in the energy conservation reconstruction of the existing building should be deeply developed, such as analysis and research of reconstruction background, local natural environment and natural resources, utilization of waste and recyclable resources etc., at the same time, perfection of the existing building energy saving assessment system is also the key to promote the settlement of the problems. This paper demonstrates the energy conservation reconstruction and comprehensive utilization of the existing buildings in the industrial urban renewal in various aspects in order to promote the sustainable development objectives of the industrial urban renewal.

Abstract: A meshless natural neighbour Petrov–Galerkin method (NNPG) is presented for solving the elasticity problems in this paper. In a certain domain, a discrete model consists of a set of distinct nodes, and a polygonal description of the boundary. The natural neighbour interpolation has Kronecker delta function property, and the construction of local sub-domain is simple both for internal nodes and boundary nodes. The whole interpolation is constructed with respect to the natural neighbour nodes and Voronoi tessellation of the given point. A local weak form over the local Delaunay triangular sub-domain is used to obtain the discretized system of equilibrium equations. The numerical results show the presented method is easy to implement and very accurate, especially for solving the problems of crack propagation or large deformations.

Abstract: In this paper, different types of debonding failure modes are described. Study of concrete cracking behavior and interfacial debonding fracture in fiber reinforced polymer (FRP)-strengthened concrete beams are carried out. A finite element analysis is performed to investigate the different types of debonding propagation along FRP–concrete interface and crack distribution in concrete. The proposed FE, denoted as FRP–FB (force-based) beam, is used to predict the load-carrying capacity and the applied load-midspan deflection response of RC beams subjected to four-point bending loading. Numerical simulations and experimental measurements are compared based on numerous tests available in the literatures and published by different authors. The numerically simulated responses agree remarkably well with the corresponding experimental results. It demonstrates that the proposed two-dimensional frame finite element (FE) is able to accurately estimate the load-carrying capacity of reinforced concrete (RC) beams flexurally strengthened with externally bonded fibre reinforced polymer (FRP) strips and plates.

Abstract: The bonding of fiber reinforced polymer (FRP) plates or sheets to the concrete structures has been found to be an effective technique to improve the capacity. As a result, a large number of studies have addressed debonding failures in FRP-strengthened RC structures, with many of them being focussed on understanding the behaviour of simple FRP-to-concrete bonded joints in which an FRP plate/sheet is bonded to a concrete prism and is subject to a tensile force. With the help of features of FRP–concrete interface and experimental data in the literatures, a non-linear mode II interface law is presented. The proposed interface law includes non-linear contributions of adhesive and concrete cover at high shear stresses. The numerical results presented in this study show that FRP strains, shear stresses, slips and values of delamination force in the bonded region are in good agreement with experimental results. The agreement verifies the validity of the proposed interface law.

Abstract: The bonding of fiber reinforced polymer (FRP) strips and plates to the concrete structures has been found to be an effective technique for flexural strengthening. The FRP is then under both pulling and peeling forces, resulting in a combination of shear sliding and opening displacement along the FRP/concrete interface. A novel experimental set-up is studied that a peeling load is applied on the FRP sheet by a circular rod placed into the central notch of the beam. Based on the linear-elastic fracture mechanics approach, a theoretical analysis is conducted on specimens representing the peeling behavior. From the numerical analysis, the load–displacement curves, load–stiffness of FRP sheet curves, and load–fracture energy curves affected by different variables are discussed. The peel load is related to the FRP sheet stiffness and to the interfacial fracture energy. Therefore, only two material parameters, the interfacial fracture energy of FRP–concrete interface and stiffness of FRP sheets, are necessary to represent the interfacial fracture behavior. The theoretical load–deflection curves of specimens agree well with the corresponding experimental results in the literatures.

Abstract: A linear elastic fracture mechanics (LEFM) approach to the debonding analysis of concrete beams strengthened with externally bonded fiber-reinforced-polymer (FRP) strips are studied. The analytical models based on the LEFM approach are presented and discussed. The fracture analysis has adopted the energy-release-rate approach and the J-integral formulation. In addition, an algorithm for the construction of the equilibrium path that describes the debonding process in the FRP strengthened beam has been developed. The approach and its applicability to the debonding analysis of the FRP strengthened beam has been examined through three cases that include a single shear test, an edge peeling test, and a beam specimen strengthened with FRP. In cases where qualitative information regarding the initiation and progress of the debonding process is available, the LEFM model can be used for a reasonable quantitative appraisal of the debonding mechanism.

Abstract: Concrete is a three-phase material consisting of cement paste matrix, discrete inclusions of sand (aggregate), and an interfacial transition zone (ITZ) between the matrix and the inclusions. In order to calculate the elastic properties of the ITZ of cement mortar, We model the material as a composite formed by a matrix with embedded spherical particles; each surrounded by a concentric spherical shell. With help of the generalized self-consistent method (GSCM), equations of bulk modulus and shear modulus of ITZ are deduced, and Elastic properties of ITZ are computed by using experimentally known elastic properties of the composite. It is found that the shear modulus of ITZ is about 50% of that of the cement paste matrix.

Abstract: In this paper, the extended finite element method (XFEM) is used for a discrete crack simulation of concrete using an adaptive crack growth algorithm. An interface model is proposed which includes normal and tangential displacements and allows the transfer of shear stresses through the interface. Different criteria for predicting the direction of the extension of a cohesive crack are conducted in the framework of the XFEM. On the basis of two examples, a comparison between the maximum circumferential stress criterion, the maximum energy release rate and the minimum potential energy criterion with experimental data has been carried out. The considered numerical simulations have confirmed the flexibility and effectiveness of the XFEM for the modelling of crack growth under general mode I and mixed-mode loading conditions.

Abstract: The crack tip region in an elastic composite can be separated into three different regions. based on a simple rate-independent phenomenological constitutive model, the path independence of the J-integral and the concept of cracktip shielding, the maximum radii R of the damage saturation zone is obtained. Damage isotropy in the largest saturated damage zone is expressed by utilizing the Monte-Carlo technique to create the uniform distributions of microcrack location and orientation. With the assumption of dilute microcrack concentration, interaction among microcracks are neglected, and the stress intensity factor produced by interaction between main-crack and each microcrack can be superposed. Two sources of loading are analyzed, one is for the main-crack microcrack interaction under an applied remote load, and the other is for the main-crack microcrack interaction accompanied by the relief of residual stresses on the microcrack surfaces. The results show that two sources of loading can shield the main-crack tip, and microcracks behind the main-crack tip can make the most shielding whereas microcracks ahead of the main-crack tip play no role in shielding.