Yan Zhuge

FRP-Retrofitted URM Walls under In-Plane Shear: Review and Assessment of Available Models

In the last two decades, several seismic retrofitting techniques for masonry structures have been developed and practiced and fiber-reinforced polymer (FRP) material has been increasingly used owing to its high strength/stiffness to mass ratio and easy application. Although much research has been carried out on FRP strengthening of unreinforced masonry (URM) structures, most of it has been experimental studies to investigate the effectiveness of retrofitting techniques rather than the development of a rational design model. In addition, more research has been conducted on FRP-retrofitted URM walls under out-of-plane loads where flexural behavior dominates, the research on the shear strength of FRP-retrofitted URM walls has been limited. This paper presents a review of research in this area. Existing retrofitting techniques are overviewed, followed by a detailed discussion of experimental results of failure modes as they are directly related to the design model. The available design models are then assesse...

Numerical simulation of the mechanical behaviour of porous concrete

– Porous concrete is a mixture of open‐graded coarse aggregate, water and cement. It is also occasionally referred to as no‐fines concrete or pervious concrete. Due to its high infiltration capacity, it is viewed as an environmentally sustainable paving material for use in urban drainage systems since it can lead to reduced flooding and to the possibilities of stormwater harvesting and reuse. However, the high porosity is due in the main part to the lack of fine aggregate particles used in the manufacture of porous concrete. The purpose of this paper is to present a numerical method to understand more fully the structural properties of porous concrete. This method will provide a useful tool for engineers to design with confidence higher strength porous concrete systems., – In the method, porous concrete is modelled using a discrete element method (DEM). The mechanical behaviour of a porous concrete sample subjected to compressive and tensile forces is estimated using two‐dimensional Particle Flow Code (PFC2D)., – Three numerical examples are given to verify the model. A comprehensive set of micro‐parameters particularly suitable for porous concrete is proposed. The accuracy and effectiveness of simulation are confirmed by comparison with experimental results and empirical equations., – The experimental investigations for porous concrete described in this paper have been designed and conducted by the authors. In addition, the type of two dimensional PFC analysis presented has rarely been used to model porous concrete strength characteristics and from the results presented in this paper, this analysis technique has good potential for predicting its mechanical properties.

Cost Optimum Design of Structural Fibre Composite Sandwich Panel for Flooring Applications

A new type of FRP composite panel suitable for civil engineering constructions has been invented by the Australian manufacturers. This new type of FRP structural sandwich Panel is made of fibre glass skins and modified phenolic core material with a density relatively higher than the normal sandwich panel. This panel is used for civil engineering applications of flooring system and glue laminate FRP beams. The extensive experimental work has been carried out by the Centre of Excellence in Engineered Fibre Composites (CEEFC) at the University of Southern Queensland to find the strength parameters of this new sandwich panel. This research aims to develop an optimum design of the new FRP sandwich floor panel by using Finite Element (FE) and Genetic Algorithm (GA) method. The numerical FE shows a relatively accurate simulation for the behaviour of the FRP panel. The materials cost was regarded as an objective function with the EUROCOMP design constraints. The optimization shows that the skins orientations 0/90o would produce the best design for one-way spaning floor panel.

The prediction of damage to masonry houses caused by foundation movements

Cracking failure in masonry houses founded on expansive soils has been widely reported throughout Australia and other countries. The cost associated with such damage is significant. The current codes of practice only provide broad guidance on the design principles of masonry under ground movement, due to a lack of research in the area. In this paper a numerical model has been developed to study the behaviour of masonry walls under footing movements as a result of expansive soils. The model is based on Distinct Element Method (DEM) which has been applied successfully by the authors to model the masonry walls under simulated (static) in-plane earthquake forces. The model is capable of predicting the crack initiation, propagation and failure modes of masonry walls under various footing movements (doming or dishing curvatures). The numerical solutions obtained from the distinct element analysis are validated by comparing the results with those obtained from the existing experiments.

Review of the Performance of High-Strength Rubberized Concrete and Its Potential Structural Applications

Partially replacing concrete aggregates with recycled materials could help to combat the decreasing availability of some natural resources (like natural sand) and at the same time help to utilize growing quantities of waste material like used tires. This idea has been put into practice to develop a more sustainable concrete material called rubberized concrete or crumbed rubber concrete (CRC). CRC has improved structural ductility and impact resistance but can have lower strength than traditional concrete. Most research to date has focused on low strength CRC and its non-structural applications. However, recent research has shown that high-strength CRC (HSCRC) can be achieved through rubber pre-treatment, using various additives, optimal rubber content, or good grading of combined rubber sizes. This paper reviews the research undertaken to date in HSCRC (defined as compressive strength over 30 MPa), focusing primarily on the material properties but also considering the potential structural applications of HSCRC. Finally, the future research necessary to prove the viability of HSCRC for structural reinforced concrete applications is discussed.

Investigation of some fundamental properties of permeable concrete

This paper presents the outcomes from a laboratory based research study undertaken to evaluate the fundamental properties of permeable concrete, including compressive strength, global and local strain, elastic modulus (stiffness), porosity and permeability. Six permeable concrete mixtures were made with constant water - cement ratio of 0.34, using different aggregate sizes and sand percentages. The compressive strength range was 15-35 MPa, while the permeability varied between 1.5 to 5.5mm/s and the porosity varied between 25 to 35 %. Two testing methods were used to measure the strain and modulus of elasticity (MOE) of the permeable concrete namely, platen-to-platen method and strain gauge method. Considerable difference was found between the MOEs obtained by the two methods. The MOE determined using the platen-to-platen method consistently were lower in value, which has been attributed to the softness of the capping components, the interface between the specimens and the platen and overall machine compliance. The pore characteristics and their distribution were seen to have an influence on the material responses such as material stiffness and strain. A comparison drawn between the axial strain obtained by the strain gauge measurement and that deduced from the platen-to-platen measurement was undertaken to evaluate the strain homogeneity along with possible detection of the localization phenomena.

Flexural strength of sandwich panel with lignocellulosic composites intermediate layer: a statistic approach

In this study, three different types of lignocellulosic composite materials have been incorporated in sandwich panel structure as an intermediate layer. The experiment was statistically designed based on single factor analysis scheme. The results of experiments have been analyzed using analysis of variance (Anova) followed by Tukeys, Fishers and Dunnets tests to obtain the information of how significant those materials contribute to the flexural strength of sandwich panel structure. The total number of samples tested was 48 beams. The results show that the introduction of lignocellulosic composites materials, that are hardboard, medium density fibre (MDF) and plywood, has significantly improved the flexural strength of sandwich panel. The range of improvement contributed by the presence of lignocellulosic composites intermediate layer was around 100–150% for samples with balsa core and 130–150% for samples with polystyrene core. The result of this study shows the potential of lignocellulosic composite material to be developed further for producing more sustainable sandwich panel.

The Implementation of Statistical Inference to Study the Bending Strength of Sustainable Hybrid Sandwich Panel Composite

The study reported here involves the evaluation of the ultimate bending stress (bending strength) of hybrid sandwich panels using a simple comparative statistical analysis. Four sets of beam were tested with each set consisting of modified beams (MB) and unmodified beam (UB) samples. A total of 42 beam samples were tested using 3 point bending followed by statistical inference analysis using a t-test. The results show that the introduction of an intermediate layer has a significant effect on increasing the bending strength of the new hybrid sandwich panel composite.

Buckling Analysis of Laminated Composite Plate on Tensionless Elastic Foundations Under Uniaxial Compression

This paper addresses the compressive local buckling behavior of an infinitely long laminated composite plate resting on a tensionless elastic foundation (Winkler foundation). The analytical solution to the contact buckling coefficient of a laminated composite plate is derived using a one-dimensional analytical method. Numerical examples are considered to investigate the influence of the ply angle and foundation stiffness on the contact buckling coefficients of laminated composite plates under uniaxial compression. The lateral boundary conditions including clamped and simply-supported edges are treated. Finally, finite element (FE) analysis is conducted to provide an independent check on the analytical solutions.

Laboratory Evaluation of the Stress-Strain relationship of Permeable Concrete

The authors conducted research aimed at developing a new type of permeable concrete material with enhanced structural strength. This paper presents and discusses the results of their investigation on the unaxial compressive stress-strain relationship of porous concrete made with two different mix designs with constant water to cement ratio. The concrete mixes were designed with a target compressive strength between 15-25 MPa and target porosity between 10-15% to study the effect of pore sizes on the stress-strain curve. The average pore space was increased by increasing the relative amount of large aggregate. The reduction in the relative amount of fine aggregate increased the average pore space and resulted in a reduction in mix stiffness and a marginal increase in ultimate strength.