The simulations of SCC mixes are also used as an aid at the mix design stage of such concretes. Self-compacting high and ultra-high performance concrete (SCHPC/SCUHPC) mixes with and without steel fibres (SCHPFRC/SCUHPFRC) are proportioned to cover a wide range of plastic viscosity. All these mixes meet the flow and passing ability criteria, thus ensuring that they will flow properly into the moulds.

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The challenge for the civil engineering community in the near future will be to realize the building of structures in harmony with the concept of sustainable development, through the use of high performance materials which have low environmental impact and can be produced at reasonable cost. Geopolymers are novel binder materials that could provide a route towards this objective. Although research on geopolymer has advanced, most of the previous research conducted on geopolymers has dealt with pastes and concentrated on the material's chemistry and microstructure. There is little information available concerning the engineering and durability properties of geopolymer concrete and none considering the use of natural pozzolans for production of geopolymer concrete. This investigation has studied the potential of using five natural pozzolans from Iran as geopolymer precursors. Most of the raw materials contain zeolites and clay minerals and have a high loss on ignition. Therefore, trials were made where samples were calcined at 700, 800 and 900°C. The solubility of both the raw and calcined materials in an alkaline solution was used as an indicator for pozzolanic activity. Improvements in pozzolanic properties due to heat treatment and elevated curing temperatures (20, 40, 60, and 80°C) were studied by using alkali solubility, XRD and compressive strength tests. It has been found that geopolymer binders can be synthesized by activating natural pozzolans and condensing them with sodium silicate in a highly alkaline environment. A new model is presented which allows the prediction of the alkali activated pozzolan strength from information on their crystallinity, chemical compositions and alkali solubility. Two types of Iranian natural pozzolans, namely Taftan which can be activated without calcination and Shahindej which was calcined were selected for further activation to study the effect of the alkaline medium on the strength of the alkali-activated natural pozzolan. The effect of the type, form, and concentration (molarities =2.5, 5.0, 7.5, 10.0 M) of the alkaline hydroxide, the modulus of sodium silicate (Si02INa20 ratio =2.1, 2.4, 3.1) and different curing conditions on the geopolymerisation of the above two natural pozzolans were studied. The optimum range and contributions for each factor is suggested based on their effect on compressive strength. An optimum paste formulation has been developed for concrete mixing together with the procedure of addition of the raw materials to the reaction mixture and suitable curing methods for producing the geopolymer concrete derived from them. The properties of this geopolymer concrete in both the fresh and hardened states have been investigated in terms of setting time, workability, air content, compressive strength, splitting tensile strength, static modulus of elasticity, ultrasonic pulse velocity, and drying shrinkage. Studies related to durability such as gas permeability, chloride ion penetration, and sulphate resistance have been undertaken and compared to these for typical OPC concretes. Some problems were encountered in applying the standard concrete durability tests. In this study attempts have been made to determine the relationships between the different properties of geopolymer concrete with its compressive strength and compared to results for ope concrete, to help to explain the differences between alkali-activated natural pozzolan concrete and ope concrete. In the countries which have large resources of natural pozzolan, geopolymer concrete based on alkali activation of these resources can help decrease the energy consumption and environmental impacts involved in using traditional cement pastes.

A column design method has been developed for use in braced frames with discontinuous columns using flexible cap and base plates and floor beams that are either simply supported or continuous. The method is intended to be used with shallow floor construction with concrete or steel/concrete composite slabs in which the floor slab occupies the depth of the floor beams and is fully grouted to the beams so that the slab restrains the full depth of the beams and was developed to simplify the design of discontinuous columns in frames using Corus ASB type floor construction without resorting to methods using nominal moments. Floor beams are therefore designed to carry the floor loads without interaction with the columns. Columns are designed to resist the floor beam reactions with column end-rotations equal to the slope of the floor beams at the top or bottom of the column, whichever is the greater. The method incorporates the elasto-plastic behaviour of columns subject to axial compression and large end-rotations. The design procedure uses rectangular stress blocks of classic plastic cross-sectional resistance and includes the end-rotations of the columns and the effects of imperfections. Therefore the approach is similar to classic second-order rigidplastic analysis but with the important additions of actual end-rotations and an initial imperfection. The method has been verified by physical tests on full-scale columns and finite element analysis using non-linear geometry and material properties. The design method 1. is derived from simple geometry and simple statics 2. accounts for initial imperfections by deriving a design value from the strut resistance of whatever design code is specified 3. is limited to sections that cannot be affected by torsional, lateral torsional or torsional flexural buckling 4. is not applicable to sections with thin walls 5. has been verified for use with hot-finished square hollow sections by testing fullscale columns The design method is defined in detail and illustrated by a worked example so that it can be used in normal design practice. Connection design and bracing requirements are discussed to enable the column design to be used to design complete frames.

Following recent events such as the World Trade Center building collapse and the Cardington large scale structural fire research program, the fire behavior of connections has now become an important research subject. This thesis presents the results of experimental, numerical and theoretical studies into the behavior of simple welded fin-plate to concretefilled tubular (CFT) columns loaded by tensile or shear force. Such connections represent a simple single-sided joint solution to steel CFTs which are considered an attractive and robust structural element. Experiments have been performed at both ambient and elevated temperatures against the results of which numerical finite element models have been validated. The ranges of parameters encompassed by the tests include column cross-section shape; column and finplate thickness; concrete in-fill; elevated temperatures and connection lever arm. The observed failure modes include fracture of the fin-plate and tearing out of the tube around the welds. By considering the results of previously published research, the current design method for similar connections under purely tensile load, in CIDECT Guide 9, based on a deformation limit of 3% of the tube width is shown to be inadequate when evaluating the ultimate strength of such connections. By comparing the results from the current test program which failed in the fin-plate with Eurocode guidance for failure of a fin-plate alone under shear and bending load it is shown that the column face influences the overall connection strength regardless of failure mode. Concrete in-fill is observed to significantly increase the strength of connections over empty specimens, and circular column specimens were observed to exhibit greater strength than similarly proportioned square columns. When validating the numerical model against elevated temperature tests it was found that the strength reduction factors suggested by Eurocode for steel at elevated temperature are appropriate. The numerical models developed have been used to perform extensive parametric studies from which simple hand calculation methods have been developed for evaluating the strength of the column component of square CFTs under either tensile or shear load imparted through a fin-plate connection. The simple hand calculation procedures are based upon defining a rigid plate deformation pattern for the connection and then applying the internal work principle. For connections under shear load a method is presented for combining the column failure load with the fin-plate failure derived from existing Eurocode guidance. Both simple hand calculation methods are compared favorably with available test results. A limited number of tests and numerical validation have also been performed for reverse channel to CFT connections loaded in shear at both ambient and elevated temperatures.

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Concrete as a material for construction has certain inherent weaknesses such as its low tensile strength and its tendency to shrink on drying and creep under stress. In recent years, attempts have been made to increase the tensile strength and ductility of cement-based matrices. In this context, the use of steel fibre reinforcement shows considerable potential. In the present investigation, short lengths of steel fibres have been used to study the mechanics of steel fibre reinforcement in cement matrices and its influence on the fracture behaviour and deformation characteristics of concrete. The influence of steel fibre reinforcement on the fracture behaviour and load-deformation properties of concrete under short-term uniaxial compression has been studied in Chapter 3. Pour types of steel fibres were used - straight, hooked, melt extract and crimped. The effect of steel fibre reinforcement on the free shrinkage and compression creep properties of cement matrices has been studied in Chapters 4 and 5. Three types of steel fibres, namely, hooked, melt extract and crimped fibres were used. Four different mix proportions ranging from cement paste to concrete were used. In the second part of Chapters 4 and 5, suitable theories to predict the free shrinkage and compression creep of steel fibre reinforced cement matrices have been derived. The influence of steel fibre reinforcement on the performance of conventionally reinforced concrete short compression members and the short-term load-deformation properties of the concrete phase of these members has been studied in Chapter 6. Melt extract steel fibres were used. Three different stirrup spacings were used - 125, 187 and 375 mm. The effect of steel fibre reinforcement on the long term deformation characteristics of conventionally reinforced concrete short compression members has been studied in Chapter 7. In the first part of this Chapter, the shrinkage and creep properties of conventionally reinforced concrete compression members, as affected by steel fibre reinforcement, are investigated. In the second part of Chapter 7, the influence of steel fibre reinforcement on the long term deformation characteristics of conventionally reinforced concrete members under combined bending and axial compression has been studied. Melt extract steel fibres were used and stirrup spacing was kept constant at 125 mm. Steel fibre-cement matrix interfacial bond characteristics under flexure have been studied in Chapter 8. The influence of parameters such as fibre embedment length, fibre diameter, spacing between fibres and fibre content of the matrix on the fibre-matrix interfacial bond strength has been studied. Limitations of the present study, conclusions and suggestions for future research are given in Chapter 9.