Effect of the Sliding of Stacked Live Loads on the Seismic Response of Structures

Dynamic interaction between sliding live loads and the structure they act on is significant in the seismic analysis and design of the structure. The problem becomes more complex when the live loads are in the form of stacks. This paper presents a numerical model to simulate the dynamic interaction between a primary structure (PS) and a set of stacked bodies lying on it. Individual bodies in the stack were termed as secondary bodies (SBs) in this study. The lowest SB in the stack interacts with the structure through friction. Similar frictional forces also exist between different levels of the stack. This numerical model was verified with a Finite Element model. A parametric study was performed on the seismic response by varying the dynamic properties of the structure and SBs. The energy dissipation is found to be significant due to sliding within the stack. A novel methodology is proposed to calculate a modified structural period (Tnew) of the structure to use in its design. It was found that the Tnew varies significantly with the structural period, mass ratios, and coefficients of friction. Finally, design equations are proposed to calculate the Tnew . Two Indian seismic hazard levels were considered for this study

Thermo-mechanical properties of 5-harness satin fabric composites

The use of woven textile reinforcements in composite structures increased significantly in the past decades due to their interesting properties over unidirectional fibres. Therefore, the prediction of the thermo-mechanical properties of woven fabric composites is essential from a design and manufacturing standpoint. A micromechanical approach based on finite element method that utilizes three-dimensional unit cell was applied to predict the effective properties of a periodic woven fabric composite material. Using the resin processing properties models such as cure kinetics, shrinkage, glass transition temperature and elastic modulus models, the development of the periodic woven fabric composite material thermo-mechanical properties, as the cure progresses was predicted. The residual strains and stresses generated in the composite unit cell during the cure were also predicted and linked with the development of the material properties. The effective properties of the cured woven fabric composite material were compared to the one of an equivalent cross-ply composite material to verify the validity of neglecting the fibre waviness while modelling woven fabric composite. \ua9 The Author(s) 2012 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.Peer reviewed: YesNRC publication: Ye

Modelling of the thermo-mechanical properties of woven composites during the cure

Woven fabrics are used more widely in composite materials as reinforcements to manufacture complex structures due to their high drapability and good impact resistance compared to unidirectional fibres. Understanding the properties of woven composites and their evolution during the cure is therefore important in terms of design and manufacturig of complex composite structures using woven fabrics.NRC publication: Ye

Embedded smart GFRP reinforcements for monitoring reinforced concrete flexural components

The main objectives of this paper are to demonstrate the feasibility of using newly developed smart GFRP reinforcements to effectively monitor reinforced concrete beams subjected to flexural and creep loads, and to develop non-linear numerical models to predict the behavior of these beams. The smart glass fiber-reinforced polymer (GFRP) rebars are fabricated using a modified pultrusion process, which allows the simultaneous embeddement of Fabry-Perot fiber-optic sensors within them. Two beams are subjected to static and repeated loads (until failure), and a third one is under long-term investigation for assessment of its creep behavior. The accuracy and reliability of the strain readings from the embedded sensors are verified by comparison with corresponding readings from surface attached electrical strain gages. Nonlinear finite element modeling of the smart concrete beams is subsequently performed. These models are shown to be effective in predicting various parameters of interest such as crack patterns, failure loads, strains and stresses. The strain values computed by these numerical models agree well with corresponding readings from the embedded fiber-optic sensors