AU2015101180A4 - Employment of Wood Blocks in Concrete-Filled Tubes - Google Patents

Abstract

Employment of Wood Blocks in Concrete-Filled Tubes Abstract: The application of wood with different shapes and volumes in concrete filled steel tubes is focused as the main idea of this innovation. This idea helps decrease the weight of the composite element relative to the fully concrete filled tubes and yet employ the compressive strength of the wood itself. The wood is covered by the concrete and the concrete is in turn covered by steel tubes so that the new composite element is believed to bring about a considerable capacity increase, especially when it is exposed to the compression. Keywords: Wood infill, Concrete; Steel tubes; C regular wood infiU Timber Concrete r Square wood infi Timber Concrete b Rectangular wood infil Timber Concrete b Rectangular fileted wood infill Timber Concrete b Fig.2. Geometric features and details of different cross-sections.

Description

EDITORIAL NOTE 2015101180 - There are 2 pages of Description which are not page numbered Employment of Wood Blocks in Concrete-Filled Tubes Tohid Ghanbari Ghazijahani* PhD in Structural Engineering (in progress) Inventor, Phone: (+61) (0)469 311 896, E-mail: tohidghanbarigjnailcom 1. Theory behind the idea and discussions: Demands for light-weight structural elements have been steadily growing. Steel is very well known for its tensile strength, while concrete is a material with a high compressive strength. By the same token, wood can greatly carry the compression. The combination of these three materials is believed to yield a very reliable composite section, as the inherent features of the three materials strengthen one another. Wood is covered by concrete in order that inward expansion of the concrete is restricted under axial loading. Furthermore, outward expansion of the wood is also limited by the concrete, which leads to a quite reliable section under loading. Besides, the steel tube - or a material such as FRP with a great strength in tension covering the whole element can restrict the concrete and wood inside. Some of the advantages of the new composite are outlined as follows: 1- Lightweight yet strong, if compared with fully concrete-filled; 2- Low price of wood especially in the countries like Australia relative to the equivalent materials such as steel or concrete. One may take the extensiveness of wooden structures in Australia - especially in low and mid-rise buildings than concrete and steel structures, as an obvious evidence for this claim. 3- Existence of steel allows possibility of connection to different elements through welding or using bolts, whereas for bare-wood or concrete buildings there is no such capability; 4- Ductility of the present composite as a significant structural parameter increases relative to the fully concrete filled tubes; 5- This combination protects the structures from collapse in fire conditions based on wood's different physical properties in comparison with pure steel constructions which are quite vulnerable to the fire collapse; 6- For the pure steel elements the internal space of the tubes remains inaccessible and accordingly useless (from the architectural point of view), whereas using this combination brings about significant increase in capacity, by additional reinforcing elements, i.e. wood and concrete, with no more space occupation. 7- From mechanical perspective, wood considerably arrests the inward failure of the concrete, while outward failure is fairly restrained by the steel. As a consequence, all materials in this combination help to optimally enhance the capacity.

2. Construction-related recommendations: Casting the concrete is assumed to be done in a similar way as the normal concrete filled tubes. There might be a concern about soaking the water of the concrete by the wood which can be readily overcome by sealing the wood blocks by the cling wraps in multiple layers. This method was tried and seen to be an effective way to resolve the mentioned issue. The other alternative is to saturate the wood with water prior to casting the concrete, although the first option (cling wraps) is particularly recommended for this project. 3. Detailed drawing of the new composite: Depending upon different available equipment various shapes of wood are proposed such as circular, square, rectangular and rectangular filleted infils (see Figs.1 and 2). The area of the wood versus concrete is a significant parameter, which can highly affect the capacity to total weight ratio. Initial examinations show that a wood core (covered by concrete) can bring about a comparable capacity relative to the concrete. It is noteworthy that the capacity to total weight ratio is deemed to vary form one particular project (or application) to another in the light of the fact that in some projects weight is a highly critical factor so that the proportion of the wood outweighs if compared with its concrete counterpart.