ANALYSIS OF COMPOSITE BUILDINGS UNDER FIRE CONDITIONS

In this paper, the performances of a generic three dimensional 45m x 45m composite floor subjected to ISO834 Fire and Natural Fire are investigated. The influences of reinforcing steel mesh and vertical support conditions on the tensile membrane action of floor slabs are investigated in details. Two robust 2-node connection element models developed by the authors are used to model the behaviour of end-plate and partial end-plate connections of composite structures under fire conditions. The impact of connections on the 3D behaviour of composite floor is considered. Based on the results obtained, some design recommendations are proposed to enhance the fire safety design of composite buildings

A simplified model for modelling flexible end-plate connection in fire

In this paper a simplified robust 2-noded connection element has been developed for modelling the flexible end-plate connections at elevated temperatures. In this model, the two stage behaviours of flexible end-plate connection are considered. The model has the advantages of both the simple and component-based models. It is computationally efficient and has very good numerical stability under static solver conditions. A total of 14 tests are used to validate the model, demonstrating that this new connection model has the capability to accurately predict the behaviour of the flexible end-plate connections at elevated temperatures. The model can be used to simulate the flexible end-plate connections in real performance-based fire resistance design of steel-framed composite buildings

Dimensonial Instability of Cement-Bonded Particleboard: Behavior of Cement Paste And Its Contribution To The Composite

This paper examines the behavior of cement paste under constant and changing relative humidity (RH) conditions to evaluate the contribution of cement paste to the dimensional instability of cement-bonded particleboard (CBPB). It was found that the trend of changes in cement paste was very similar to, but the degree of changes was different from, that of CBPB at various exposures. The comparison of the results of cement paste with those of CBPB indicated that the inclusion of wood chips accelerated the carbonation reaction, and that carbonation of the cement paste exerted additional stresses on the wood chips in CBPB; this resulted in a slightly higher increase in mass but an appreciably greater decrease in the dimension of CBPB under constant 20°C/65% RH. The cement paste had considerably lower changes in mass and dimension with a single change in RH between 35 and 90% RH (except for the increase in mass on adsorption at 90% RH) compared to CBPB. The inflection in the relationship between mass and dimensional changes of cement paste was more distinct than that of CBPB with the change of mass per unit length change after the "inflection point" being about eight times higher than that of CBPB on desorption. Under cyclic RH, the response to the level of RH and the history of sorption was different between cement paste and CBPB, with the difference in dimensional change between adsorption and desorption being more significant, while the adsorption at 90% RH for the cement paste was considerably higher. Fitting of models previously developed to the data permitted the prediction of accumulated change of the cement paste with a good degree of fit and established the suitability of using these formulae for modelling CBPB as a composite to be described in a further paper in this series

Revealing the interface structure and bonding mechanism of coupling agent treated WPC

© 2018 by the authors. This paper presents the interfacial optimisation of wood plastic composites (WPC) based on recycled wood flour and polyethylene by employing maleated and silane coupling agents. The effect of the incorporation of the coupling agents on the variation of chemical structure of the composites were investigated by Attenuated total reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) and Solid state 13 C Nuclear Magnetic Resonance spectroscopy (NMR) analyses. The results revealed the chemical reactions that occurred between the coupling agents and raw materials, which thus contributed to the enhancement of compatibility and interfacial adhesion between the constituents of WPC. NMR results also indicated that there existed the transformation of crystalline cellulose to an amorphous state during the coupling agent treatments, reflecting the inferior resonance of crystalline carbohydrates. Fluorescence Microscope (FM) and Scanning Electron Microscope (SEM) analyses showed the improvements of wood particle dispersion and wettability, compatibility of the constituents, and resin penetration, and impregnation of the composites after the coupling agent treatments. The optimised interface of the composites was attributed to interdiffusion, electrostatic adhesion, chemical reactions, and mechanical interlocking bonding mechanisms

Factors influencing self-healing mechanisms of cementitious materials: A review

The increasing awareness of climate change and global warming has pushed industries to be more conscious of their environmental impact, especially in the construction industry with the main contributor being concrete. Concrete is a material that is in very high demand in the construction industry for structural applications. However, it’s a material with a major concern with the challenges of microcracking. New technology has seen the development of self-healing material, using novel techniques to bring cementitious materials back to its original state. This paper reviews and evaluates the novel techniques adopted by the researchers in the field to achieve a self-healing material, with the main focus being on the factors influencing the mechanisms of autogenous healing and bacteria-based healing. Various parameters including bacteria type, pH, temperature, nutrient, urea, and Ca2+ concentration, bacteria concentration and application, pre-cracking, healing condition, cement type, and crack width are all important for healing efficiency, although the use of water to facilitate both autogenous and ureolytic bacteria healing mechanism is paramount for the triggering of healing processes. This study thoroughly presents various factors and their correlation to the healing mechanisms of autogenous healing and ureolytic bacteria healing. Further studies are identified to better understand the exact mechanism taking place and which healing process contributed to how much of the healing, and this review could serve as an informative platform for these pursues

Critical review on the thermal conductivity modelling of silica aerogel composites

As a new generation of thermal insulation materials, the effective thermal conductivity of aerogel and its composites is extremely low. The nanoporous structure of aerogels demobilises the movement of gas molecules, and the nano-skeleton system restricts solid heat transfer because of the size effect. Numerous research and modelling works have been carried out to understand and predict heat transfers. This review thoroughly discusses the existing theories and models of silica aerogel composites in gas, solid and radiative heat transfers. It investigates the correlation of the pore size distribution and solid skeleton network of the composites with the thermal conductivity. The review then assesses the advances of the development and questions remaining for further development, including 1) some unexplainable performance of existing models and 2) improvements required for gas and solid thermal conductivity models. Bridging the identified research gaps shall lead researchers to understand existing models better, develop a more accurate model based on more realistic microstructure simulation and further innovate the models for other emerging composites

Development of facture free clay-based aerogel: Formulation and architectural mechanisms

Clay aerogel could potentially be ideal insulation materials for many industrial sectors because of its natural resource, green and low cost production. However, there is a dilemma between thermal conductivity and integrity, which are also highly related to density and microstructure. These could be manipulated through formulation compositions and processing parameters. This paper employs cellulose nanowhisker (CNW) as the reinforcement to develop novel 3-component systems of aerogel by exploring optimum formulation and architectural microstructure systems. The results shows that fracture free clay aerogel can be developed with solid content less than 4wt%, enabling optimum thermal insulation performance of 0.034 W/mK; optimum micro-network and hence much more enhanced bonding systems can be built with strategical interactions within and between clay platelets, PVA and CNW; and an architecture of ‘CNW-clay (mechanically)+CNW-PVA (chemically)+CNW-clay’ 3-component clay aerogels could be established, achieving excellent mechanical property (e.g. compressive strength and shape recovery)

Ammonia-Nitrogen Recovery from Synthetic Solution using Agricultural Waste Fibers

In this study, modification of Empty Fruit Bunch (EFB) fibers as a means to recover ammonianitrogen from a synthetic solution was investigated. Methods: The EFB fiber was modified using sodium hydroxide.Adsorption-desorption studies of ammonia nitrogen into the modified EFB fiber were investigated Findings: Theincrease in adsorption capacity was found to be proportional with the increase of pH up to 7, temperature and ammoniaconcentration. The maximum adsorption capacity is 0.53-10.89 mg/g. The attachment of ammonia nitrogen involves ionexchange-chemisorption. The maximum desorption capacity of 0.0999 mg/g. Applications: This study can be used as abaseline for designing a low cost adsorbent system for ammonia nitrogen recovery drainage and industrial wastewater aswell as EFBs-palm oil mill effluent composting