An investigation of prestressed concrete containing steel fibres as secondary reinforcement to improve performance in shear, flexure and bond is reported. Emphasis is placed on the use of steel fibres in prestresssed extruded hollow core slabs, since these common precast elements have intrinsic difficulty in incorporating traditional secondary reinforcement due to their unique shape and manufacturing method. Two separate studies were carried out. The first study involved laboratory investigations into the bond between fibre reinforced concrete (FRC) and the prestressing strand, and the shear behaviour of laboratory-cast prestressed fibre reinforced concrete (PFRC) beams. The second part involved the factory production of fibre reinforced hollow core slabs in co-operation with a local manufacturer. The fibre reinforced hollow core slabs were subjected to conventional full-width shear tests, concentrated load shear tests, and to transverse flexure. For all laboratory cast elements, cubes, cylinders and prisms were cast to investigate compressive, tensile and flexural properties, respectively. Two types of steel fibre were investigated: hooked-end steel fibres at fibre volume fractions (Vf) of 0.5%, 1.0% and 1.5%; and amorphous metal fibres at Vf‘s of 0.28% and 0.56%. The trial production of fibre reinforced hollow core slabs necessitated the investigation of the effect of steel fibres on the extrusion manufacturing process. It was shown that fibre reinforced hollow core slabs could be adequately compacted with only slight increases in mixing water. Fibres were found to distribute randomly throughout the cross-section. However, the rotation of the augers affected the orientation of fibres, with fibres tending to align vertically in the web. It was shown that the addition of steel fibres to prestressed concrete has a negative effect on the bond between matrix and tendon, leading to longer transfer lengths. The effect of the increase in transfer length was to reduce cracking shear strengths by 4%. Shear tests showed that the incorporation of steel fibres could increase shear strength by as much as 45% for Vf = 1.5%. This increase in shear strength, known as the fibre contribution, was shown to be due to fibres bridging across the crack and an increased compressive resistance due to fibres arresting the propagation of cracks into the compressive zone. A semi-empirical equation for shear strength of PFRC elements is developed. It is given in two forms, one compatible with the present equations for prestressed concrete given in BS 8110 and Eurocode 2, and a second form compatible with that advocated for fibres in reinforced concrete. The equation makes use of equivalent flexural strength which is recognised as the most useful material property for design of FRC. The equation was found to give good correlation with the shear strength of single web beams cast both in the laboratory and under factory conditions. However, a overall strength reduction factor is required for full-width hollow core slabs to account for uneven load distribution and inconsistent web widths. This is consistent with tests on plain hollow core slabs found in the literature.

The designer of lattice trusses has been traditionally encouraged to avoid extra joint bending moments by ensuring 'noding' of member centre lines. This can however cause problems in the design of RHS trusses with small (economical) branch members by causing large gaps at joints with undesirable flexibility for slender chord walls. 100% overlap joints overcome this problem while still maintaining economic single cut branch ends. The research programme set out first to highlight the difference in behaviour of trusses with large gap noding and completely overlapping joints. Two similar trusses - one gap, the other lap - with matched sections were tested to failure. It was concluded that the gap joint truss (branch/chord width ratio = 0.4) was much less efficient than the corresponding 100% overlap truss despite the large eccentricities. The collapse load of the latter was some 35% greater, while the stiffness properties were better, and remained linear for a substantial proportion of the loading. On the other hand the gap joint truss soon became non-linear, with large overall deflections. Local connecting chord wall deflections were quite small in the lap joints while appreciable deflections occurred at gap joints under service loads. Elastic frame analyses were carried out for all the six test trusses (one gap and five lap). For the overlap trusses, axial forces and bending moments could be predicted fairly accurately but a non-linear analysis was required for the gap jointed truss even at fairly modest loads. The effects of ß ratio, chord slenderness and branch angle were all examined within the parameter range tested. The advantages of truss continuity moments as well as plastic redistribution of moments have been observed to reduce the occurrence of the local chord buckling mode of failure (L7), compared with previous isolated joint tests. Results obtained from tests on isolated joints can give good agreement with those obtained from truss tests, both with respect to strength and failure mode. However, as the isolated joint testing cannot always reproduce the support conditions in a truss, the failure modes (and hence strengths) can differ. The current CIDECT design strength equations and recommendations for gap and overlap joints are largely based on the results of isolated joint testing. The suitability of the CIDECT strength equations and recommendations for designing RHS lattice trusses has been reviewed. Consequently, for the 100% overlap joint trusses a simple design method has been presented in conjunction with practical design recommendations. The problems associated with the analysis and design of the gap joint truss are described in detail.

The design of reinforced concrete deep beams is not yet covered by the current British Code CP110: 1972. Some provisions are given in the CEB-FIP Recommendations (1970) and the AC1318-71 Building Code, and the new (1977) CIRIA design guide contains more comprehensive guidance including a number of recommendations for the design of deep beams with web openings. This thesis is concerned with the general behaviour in shear of single-span reinforced concrete deep beams and in particular the effects of web openings on their ultimate strength and serviceability. The test specimens comprised seventy-five lightweight and sixteen normal weight reinforced concrete deep beams with span/depth ratios ranging from one to two. The effects of a varied range of web openings on deflections, crack widths, cracking loads, failure modes, and ultimate shear strengths were studied, and the influence of web reinforcement was investigated. The exact analysis of reinforced concrete deep beams with web openings presents formidable problems. However, the ultimate shear strengths of such beams can be predicted with reasonable accuracy using a simple structural idealization, which was derived from the results of the test programme. A simple design method is explained and design hints are given. The procedures currently used by practising engineers for the design of deep beams are outlined and discussed, and a more detailed review of the new CIRIA guide is presented. Design examples are given to illustrate the use of the various methods. In all the current procedures, the design assumptions regarding the anchorage requirements of the longitudinal tension reinforcement are necessarily conservative. Appendix 1 describes the details of nine tests carried out to provide information on the effects of various amounts of end anchorage on the strength and crack, control of deep beams. In Appendix 2 details are given of three tests carried out to investigate the behaviour of deep beams under repeated loading conditions.

The main objective of this thesis was to develop numerical modelling procedures for composite connections and to use results generated in conjunction with data from other sources as the basis for the preparation of design procedures. The finite element method has been used for the numerical simulation of composite endplate connections. The developed model was verified by comparing both local measures of response and overall behaviour with test results. The validated model was then used in conjunction with theoretical analysis to study the behaviour of composite endplate connections for variable shear to moment ratios. This permitted the identification of those cases for which changes in the shear to moment ratio affects the connection's moment capacity. The model was also used in conjunction with theoretical analysis to study the effect of varying levels of axial column loading on the connection moment capacity. Results of both studies indicated a need for modifications to the equations of EC3 (for bare steel connections but which are also applicable to composite connections) that consider the interaction with column loading. These are: the equations for column web compression resistance, column web shear resistance and the bolt force. Using the FEM results, available test results and EC3 and EC4 equations for the determination of basic component forces, design procedures for composite flush endplate, finplate and angle cleated connections are proposed. Predictions from the design method have been compared with a total of 53 test and finite element results for the flush endplate connections (32 laboratory tests from 7 different sources plus a further 21 numerical results) so as to provide validation over the full range of parameters. These comparisons gave an overall prediction to test ratio of 0.99 with a standard deviation of 0.14, thereby demonstrating that the proposed method can accurately predict the resistance of composite flush endplate connections under a variety of different connection arrangements and loading conditions. Similarly, the prediction from the design method was compared with 6 finplate test results which gave an average prediction to test ratio of 1.06 with a standard deviation of 0.18. Comparisons for the angle cleated connection using 16 test results from 4 different sources gave an average prediction to test ratio of 0.98 with a standard deviation of 0.13. Theoretical studies have been performed to develop equations to predict the initial stiffness for composite endplate connections and these have been verified against test results. Suggestions to predict the available rotation capacity of flush endplate connections have also been made. This two methods has been combined with the moment capacity model to develop a prediction method for the overall behaviour of the flush endplate connections. The finite element method has also been used to develop a numerical simulation of non-sway composite frames. Comparisons of results show good agreement with the observed test behaviour. It has been found that it is possible to model the non-sway frames in a way that can predict the frame moment distribution, connection moment - rotation response and the beam load displacement history with sufficient accuracy. This provides an economic tool to study different aspects of the behaviour of composite non-sway frames. A numerical model has been developed for un-braced steel frames by simplifying the composite frame model. This model was verified using numerical results selected from the work of other researchers. Using the model for steel frames, studies were conducted for sway behaviour which provide guidance on behaviour suitable as a basis for developing design procedures.

The twin aims of this research were to improve the presentation of codified design information and to investigate the methods used to calibrate the partial safety factors applied to resistance functions (ΎR-factors) so as to improve both the economy and the reliability of the predictions. A restructured version of EC3 (known as F-EC3) was developed by rearranging the design clauses on the basis of design tasks. This system enables the code to become more user-friendly. Hypertext versions of both EC3 and F-EC3 have been created on PC-based Microsoft Windows compatible software. The implications of hypertext on structural codes are investigated. The procedure used for calibrating the ΥR-factors contained within EC3 - (the Annex Z method) was reviewed and an alternative technique involving less assumption is proposed. A comprehensive set of measurements recording the material strength and the geometric properties of steel were obtained and collated. The large data set (over 7000 tests) was sufficient to evaluate the type of probability distribution characterising the variability of the basic material and geometric properties of structural steel. The resulting data were combined with experimental test results to determine the reliability of plate girder design and restrained beam design. The theoretical shear buckling resistance of plate girders (predicted by the simple post-critical and tension field, methods) was compared with experimental test results to determine reliability. The analysis demonstrated that plate girder design falls well short of the target reliability and an adjustment to the design methods is required in order to ensure safe design. A series of 4-point bending tests on laterally restrained beams were conducted to establish the accuracy of the Mpl.Rd resistance function. This study quantifies the degree of conservatism inherent in the Mpl.Rd design method and provides convincing evidence of the need to reduce the ΥR-factor applied to this resistance function. A modification is proposed to the design formulae which improves accuracy and permits the full moment capacity of restrained beams to be utilised.

One of the most vital duties for engineers is to preserve life and nature by utilising safe designs that take into account environmental standards and monitoring the performance of structures against design criteria. Furthermore, monitoring can be used to determine any required maintenance of an important structure following a catastrophic event. Numerous different techniques and instruments can be employed for such a purpose with different requirements producing different results. For instance, some techniques need to embed sensors inside the building, such as Geotechnical Sensors. Others can offer high quality, but with a low point density and require fixed stations and targets, like Total Stations (TS). In such cases, the location of deformation tends to be known, such as in dams, bridges, and high-rise buildings. However, this is not always the case where it might be hard to expect deformation location as in the case of historic ruins where each part of the structure could be subject to deformation. The challenge in such case is to detect the deformation without any previous knowledge. Remote Sensing (RS) techniques, such as Digital Photogrammetry, Synthetic Aperture Radar (SAR), Interferometric Synthetic Aperture Radar (InSAR), and Terrestrial Laser Scanner (TLS) can be solutions for such an issue. Interestingly, many researchers are focusing on using TLS for monitoring owing to the great spatial resolution system can offer. However, there are three challenges in using TLS in monitoring: the first one is a huge amount of data and the difficulty of handling it; the second one is the difficulty of comparing between two epochs because observations of TLS are not repeatable; and the third issue is the noise which is attached to the data. The first problem is solved by segmentation and point structure while the second and the third ones still need more investigation, although some interesting researches have been done in this area. The aim of this research is to develop a new approach to detect and localise unpredictable deformation. It is based on TLS measurements and Generalised Procrustes Analysis (GPA) techniques to determine deformation vectors, while boxing structure and F-test are used to detect and localise deformation. In summary, after applying this approach, the whole concerned building is represented as parts, for each of which the displacement vector and the deformation probability are estimated. Ultimately, it is possible to monitor any part through different epochs. In addition, through this technique, it is possible to determine deformations - not just between two epochs, but for sequences of them. This can give more reliable results. Four validation experiments have been conducted. The first test was designed to assess the performance of the developed software and to fix some variables. Therefore, it was based on simulated data with controlled white noise, distributed according to the normal distribution, and simulated deformations. The results of this test revealed the success of the proposed algorithm to detect and to localise deformations. In addition, it showed the success when no deformations exist. Furthermore, optimistically, it could observe deformations with magnitude less than the noise level; however, the probability was only 40%. Correspondingly, real scan data with simulated deformations was used in the second test. The purpose of this test is to examine the performance of the proposed method in case of real errors budget. However, the short range of the test (about 10m), a featureless scanned area (wall only), and scanning from one position for all epochs (no need for registration) can reduce errors to a minimum. Results of this test showed the success of the proposed method to detect and localise deformations. Potentially, it can give indications for areas with deformations less than the noise level. Furthermore, results of the proposed method can be considered better than that of CloudCompare software. The third test was conducted to examine the performance of the proposed technique regarding different materials and textures. For this purpose, the Nottingham Geospatial Building (NGB) was selected with more extensive ranges (between 20-25 m). Similar to the second test, all measurements were taken from the same scanner position. To some extent, the proposed technique succeeded to detect and to localise deformations. However, the researcher does not recommend it for monitoring modern and complicated buildings, instead it has been developed for monitoring historic ruins. Finally, the proposed method was applied on the Bellmanpark Limekiln, Clitheroe, Lancashire monitoring project. This is a live project for Historic England and addresses a historic building that currently has some structural issues. The outcome of the proposed method revealed deformations in the faces South East (SE) and North East (NE). From examining these faces, three deformed areas were found: two in the face SE and one in the face NE, which might cause some cracks appeared in these faces. Alternatively, the CloudCompare software has been employed to detect deformation. Although results coincide with the proposed method for detected deformations, it cannot locate these deformations very well because it diffused over a wide area. In addition, it cannot determine actual directions of the deformations unlike the proposed method.

Soil-Structure Interaction (SSI) procedures for performance-based seismic design of building structures have been in existence in design guidelines and provisions for decades. However, several issues still remain regarding the application of these procedures to inelastic multi-storey buildings. Three main issues are identified and investigated in this research. Firstly, the gap between code-specified design response spectra and base shear demands of inelastic flexible-base multi-storey buildings is bridged by introducing a strength reduction factor RF and a Multi-Degree-Of-Freedom (MDOF) modification factor RM. The strength reduction factor RF, derived based on the combined (and similar) effects of SSI and structural yielding, allows base shear demands of a flexible-base yielding Single-Degree-Of-Freedom (SDOF) structure to be calculated directly from code design response spectra. The MDOF modification factor RM links base shear demand of a MDOF structure to that of its SDOF counterpart. Secondly, the effect of frequency content of ground motions on elastic and inelastic flexible-base buildings located on very soft soil profiles is examined. Results showed that normalising the equivalent period of a SSI system Tssi by the corresponding predominant periods resulted in more rational spectra for seismic design purposes. In the elastic response spectra, Tssi is normalised by the spectrum predominant period TP corresponding to the peak ordinate of a 5% damped elastic acceleration spectrum, while for nonlinear structures Tssi should be normalised by the predominant period of the ground motion, Tg, at which the relative velocity spectrum reaches its maximum value. It is shown that an actual SSI system can be replaced by an equivalent fixed-base SDOF (EFSDOF) oscillator having a natural period of Tssi, a viscous damping ratio xissi and a global ductility ratio of mussi. The EFSDOF oscillator performed well for linear systems while, in general, overestimated ductility reduction factor Rmu of SSI systems with high initial damping ratio, which consequently led to an underestimation of inelastic displacement ratio Cmu. The two issues stated above were addressed by results of a large number of response history analyses performed using a simplified SSI model where the foundation response was assumed to be linearly elastic and frequency-dependent. The soil-foundation model, developed on the basis of the cone theory, has been verified to be a reliable tool for simulating dynamic soil-foundation interaction. Finally, in order to take into account foundation nonlinearity in preliminary seismic design of building structures, a simplified nonlinear sway-rocking model was developed. The proposed model is intended to capture the nonlinear load-displacement response of shallow foundations during strong earthquake events where foundation bearing capacity is fully mobilised. Emphasis is given to heavily-loaded structures resting on a saturated clay half-space. The variation of soil stiffness and strength with depth, referred to as soil non-homogeneity, is considered in the model. Although independent springs are utilised for each of the swaying and rocking motions, coupling between these motions is taken into account by expressing the load-displacement relations as functions of the factor of safety against vertical bearing capacity failure (FSV) and the moment-to-shear ratio (M/H). The simplified model is calibrated and validated against results from a series of static push-over and dynamic analyses performed using a more rigorous finite-difference numerical model. Despite some limitations of the current implementation, the concept of this model gives engineers more degrees of freedom in defining their own model components, providing a good balance between simplicity, flexibility and accuracy.

In the last three decades, advances in modern manufacturing processes, such as additive manufacturing (AM) on one hand and computational power on the other hand, has resulted in a surge of interest in topology optimization as a means of designing high performance components with high degrees of geometrical complexity. Topology optimization seeks to find the best design for a structure by optimally distributing material in a design space. Therefore not only the shape and size of the structure, but also the connectivity of the structure changes during the topology optimization process. As a result, the solution of a topology optimization problem might be represented with a high degree of geometrical complexity as it is not dependent on the initial geometry. The finite element method (FEM) is a powerful numerical analysis technique that was developed to solve complex solid mechanics problems. Many topology optimization approaches use FEM to calculate the response of the structure during the optimization process and some of them, called “element based-methods”, are integrated with FEM to use the properties of finite elements as design variables in the optimization. The solutions of such approaches are usually represented by a uniform finite element mesh that bears no relation to the final geometry and hence they don’t provide an accurate representation of the design boundary. The solution from topology optimization must therefore go through further post processing stages to obtain a manufacturable design. The post processing stages which can include smoothing and shape optimization are costly and time-consuming and may result in the structure becoming less optimal. With traditional manufacturing processes this is acceptable as the manufacturing constraints prevent the optimized design from being manufactured so some re-analysis is necessary. With additive manufacturing, however, this restriction is removed, which means a topology optimization resulting in a manufacturable design is highly desirable. Evolutionary structural optimization (ESO) is an element based topology optimization approach which operates by systematically removing inefficient material from the structure until the optimization objective achieves convergence. Due to the intuitive nature of ESO, this method is simple to be programed and can be easily integrated with FEM or other numerical analysis techniques; thus it is suitable for complex geometries represented with FEM. During the last two decades ESO and its extensions, such as bi-directional ESO (BESO), have been successfully used for many topology optimization problems such as stiffness design, design of compliant mechanisms, heat conduction problems and frequency problems. However, being an element based method, the drawback of poor boundary representation remains. The extended finite element method (X-FEM) is an extension of the classical FEM that was developed to represent discontinuities, such as cracks and material-void interfaces, inside finite elements. X-FEM can be employed in topology optimization problems to handle the material-void discontinuity introduced by the evolving boundary during the optimization process which potentially enables a sub-element boundary representation. This requires an implicit boundary representation, such as level-set method with the benefits of better computational accuracy through the optimization, more optimized solution and smoother boundaries for direct to manufacture. In this work a new method of evolutionary structural optimization is proposed in which X-FEM is employed for the more smooth and accurate representation of the design boundary. Linear finite elements are used to discretize the design space. These include 4-node quadrilateral elements in 2D modelling and 8-node hexahedral elements in 3D modelling. To implement the X-FEM, an implicit boundary representation using isoline and isosurface approaches is used. The proposed method which is called “Iso-XFEM” is implemented for various topology optimization problems, including the stiffness design of 2D and 3D structures, stiffness design with additional displacement constraint and topology optimization of geometrically nonlinear problems. The solutions of the Iso-XFEM method are compared with those obtained using BESO, as a representative FE based method. The results confirm a significant improvement in boundary representation of the solutions when compared against BESO, and also demonstrate the feasibility of the application of the proposed method to complex real-life structures and to different objectives. All the programs used to generate topology optimised solutions using the proposed method and its modifications are developed by the author. These include topology optimization codes, linear and non-linear FEA, and 2D and 3D X-FEM integration schemes.