This thesis is about late medieval carpenters, their techniques and their art, and about the structure that became the fusion of their technical virtuosity and artistic creativity: the hammer-beam roof. The structural nature and origin of the hammer-beam roof is discussed, and it is argued that, although invented in the late thirteenth century, during the fourteenth century the hammer-beam roof became a developmental dead-end. In the early fifteenth century the hammer-beam roof suddenly blossomed into hundreds of structures of great technical proficiency and aesthetic acumen. The thesis assesses the role of the hammer-beam roof of Westminster Hall as the catalyst to such renewed enthusiasm. This structure is analysed and discussed in detail. Its place in the milieu of late medieval architecture is assessed, and its influence evaluated. That influence took effect mainly in East Anglia. Thus, early fifteenth-century trends in hammer-beam carpentry in the region are isolated and analysed. A typology of is created, from which arise surprising conclusions regarding the differing priorities late-medieval carpenters ascribed to structure, form and ornament. A chapter is also devoted to a critical review of literature pertaining to the topic.

When used as secondary roof purlins, cold-formed steel (CFS) sections are often attached to trapezoidal sheets through self-drilling screws to form a complete roofing system. The load application points are often eccentric to the shear centre, and thus inevitably generate a torsional moment that will induce twisting and/or warping deformations in addition to bending deflection. The connections between purlin and roof sheeting provide a restraining effect on purlin members by preventing such lateral and twisting movements, and hence have a beneficial effect on the load-carrying capacity. In this thesis the interactional behaviour of CFS purlin-sheeting system have been investigated through the following steps: (1) A F-test is carried out to measure the rotational stiffness at the connections, an engineering-orientated model is developed for quantifying the rotational stiffness regardless to purlin and sheet geometry and loading directions; (2) A set of loading tests on Z- and Σ- roof system are conducted to investigate the impact of rotational stiffness on the overall structural performance, load-carrying capacity and buckling behaviour of the system; (3) Finite element simulations of the existing tests are carried out and successfully validated; (4) Numerical parametric studies are established to study other factors that could affect the rotational stiffness.

Beam-column (BC) joints play an important role in the seismic performance of moment-resisting reinforced concrete (RC) frame structures. Without adequate joint shear reinforcement, BC joints can be the most vulnerable elements during an earthquake. Several techniques for improving the seismic performance of BC joints have been proposed, but they have been criticised for being labour-intensive and/or susceptible to premature debonding. This research explores the application of the deep embedment technique for strengthening a shear-deficient beam-column joint. Two approaches, experimental and finite element (FE) study were conducted. The experiment contained the tests of seven exterior RC BC joints under constant column axial load and a reverse cyclic load at the beam end. Variables considered during the experiments were the material type and embedded reinforcement ratio. The FE study included the modelling of the tested specimens using ABAQUS and parametric study to asses the effect of column axial load, concrete compressive strength and embedded bar size on joint shear strength. The experimental results showed the strengthened specimens had superior global and local behaviour compared to the control one. In addition, the maximum joint shear strength also changes linearly with the variation of the concrete strength, column axial load and embedded bar size.

Initially, two experimental programmes studying the structural behaviour of stainless steel beam-to-open column joints and beam-to-tubular column joints under static loads are reported in detail. The joint configurations tested include flush and extended end plate connections, top and seat cleat connections and top, seat and web cleat connections. The full moment-rotation characteristics are reported in detail. It is observed that the connections displayed excellent ductility, superior than that of equivalent carbon steel connections, and attained loads much higher than the ones predicted by design standards for carbon steel joints. Nonlinear FE models have been developed and validated against the experimental results. The FE models are shown to accurately replicate the experimentally determined, initial stiffness, ultimate resistance, overall moment-rotation response and observed failure modes. In addition, a comprehensive parametric study is conducted. The design rules for stainless steel connections, which are based on the specifications of EN 1993-1-8 for carbon steel joints, are reviewed and are found to be overly conservative in terms of strength and inaccurate in terms of stiffness thus necessitating the development of novel design guidance in line with the observed structural response. Hence, simplified mechanical models in line with the observed response are developed.

The building construction industry is growing all over the world and considered as a labour-intensive industry. It is associated with significant safety risks and losses resulting from major accidents. These critical safety risks are largely due to lack of awareness, which causes poor performance. Furthermore, in construction management projects, risk assessment tools are still widely employed by adopting two traditional parameters, severity of consequence (SC) and probability of occurrence (PO), to analyse the safety risk level. It is not clear, however, whether this analysis can evaluate the safety risk magnitude appropriately, which necessitates the introduction of another parameter, probability of consequence (PC), to improve the risk evaluation. The fuzzy reasoning technique (FRT) is useful for quantifying and dealing effectively with the lack of certainty related to the domain of building construction projects. PC was incorporated into the model which allows safety risks to be assessed correctly. Furthermore, the modified fuzzy analytical hierarchy process (MFAHP) and fuzzy technique for order preference by similarity to ideal solution (FTOPSIS) methods are integrated into a new construction safety risks model for the evaluation of important safety risks. Four specific case studies are employed to illustrate the applicability and performance of the proposed model.

Structural members of reinforced concrete (R/C) buildings designed according to older, less stringent seismic codes are often vulnerable to shear or flexure-shear failure followed by axial failure. Thus, such substandard R/C structures are susceptible to vertical collapse, which pertains to the exceedance of vertical resistance of columns and connecting beams and can lead to the whole structure – or a substantial part of it – undergoing collapse. The largest database of shear and flexure-shear critical R/C columns cycled well beyond the onset of shear failure and/or up to the onset of axial failure is compiled and empirical relationships are developed for key parameters affecting the response of such members after the initiation of shear failure. A novel shear hysteresis model is proposed employing these relationships, based on experimental observations that deformations after the onset of shear failure tend to concentrate in a specific member region. A computationally efficient finite element model of the member-type is proposed, using the above shear hysteretic model and combining it with displacements arising from flexural and bond-slip deformations to get the full lateral force-lateral displacement response. It accounts for the interaction between flexural and shear deformations inside the potential plastic hinges, the distribution of flexural and shear flexibility along the element, as well as the location and extent of post-peak shear damage, without relying on assumptions about the bending moment distribution and avoiding shortcomings of previous beam-column models pertinent to numerical localisation. Thus, the full-range hysteretic response of substandard R/C elements can be predicted up to the onset of axial failure subsequent to shear failure with or without prior flexural yielding, while simultaneously accounting for potential flexural and anchorage failure modes. The proposed model is implemented in a finite element structural analysis software and its predictive capabilities are verified against quasi-static cyclic and shake-table test results of column and frame specimens. The model is shown to be sufficiently accurate not only in terms of total response, but more crucially in terms of individual deformation components. Overall, it is believed that the accuracy, versatility and simplicity of this model make it a valuable tool in seismic analysis of complex substandard R/C buildings. An experimental investigation of shear and flexure-shear critical R/C elements is carried out with the aim of independently validating the beam-column model. Furthermore, an opportunity is provided to verify the model’s underlying assumptions, which is of paramount importance for the reliability of its analytical predictions. The experiments were designed in such a manner as to investigate the effect of vertical load redistribution from axially failing members on the lateral post-peak response of neighbouring columns.

In 1968 a relatively small gas exposition on the 18th floor of the Ronan Point tower building resulted in the partial collapse of the structure. This event highlighted that progress collapse may occur to structures under an accidental loading event. Other events, including the bombing of the Murrah federal building in 1993 in Oklahoma, have resulted in the common design requirement that a structure be capable of surviving the removal of a load bearing element. This approach, often referred to as the sudden column loss scenario, effectively ignores the cause of the damage and focuses on the structure’s response afterwards. The refinement of the analysis varies, with options to include the nonlinear and dynamic behaviours associated with extreme events, or to use simplified linear and static models with factors included to account for the full behaviour. Previous research into progressive collapse has highlighted that providing ductility in the connections, and avoiding brittle failures, is important in ensuring the structure maintains integrity after a column loss event. However, the majority of this work has been focused on the behaviour of steel and Reinforced Concrete (RC) frame structures. As flat slab construction is a popular method for many structures, due to the flexibility it offers for layouts and its low storey heights, it is an important to consider flat slab behaviour in more detail. Furthermore, slab elements behave differently to frame structures due to the Alternative Load Paths (ALPs) that can develop after a column loss via two-dimensional bending mechanisms. Additionally, punching shear failure is a known issue due to the thin section depths. This work addresses the issue of the response of RC flat slab structures after a sudden column loss. As previous case studies have demonstrated that brittle failures may lead to progressive collapse of such structures, a complete understanding of the response is required. The nonlinear behaviour of a slab structure, due to both material and geometric factors, is investigated to determine the additional capacity available beyond the usual design limits. Additionally, the dynamic factors involved, primarily due to inertial effects, are also considered. To achieve this, experimental and numerical studies were conducted. A series of 1/3 scale models of slab substructures were constructed to replicate column loss events. Two types of tests were conducted, a static push down test with a support removed and a sudden dynamic column removal case. Displacements, strains and support reactions were recorded throughout, along with cracking patterns. For the dynamic tests a high speed camera was used to obtain the deflection response in the short time period after removal and to observe the formation of cracks. Comparisons between the two cases allowed determination of the dynamic effects on the response of the system. The experimental programme was then replicated using a Finite Element (FE) model. The results taken from the experimental case were used to validate the material and modelling assumptions made during the numerical simulations. This validated model was finally used to investigate a wider range of variables and assess the response of typical structural arrangements, with particular focus on the nonlinear and dynamic factors involved after a sudden column loss. The experimental and numeral investigations demonstrated that after the loss of a column, flat slab structures can maintain integrity due to a change in the load paths away from the removal location. Although in some cases a large amount of flexural damage to the concrete and reinforcement occurred, such effects did not lead to complete failure. However, during the experimental programme some punching shear failures occurred, usually at the corner column locations. From the numerical analysis, shear forces of over twice the fully supported condition occurred as a result of removing a column, which may exceed the designed capacity. Comparisons between a static and dynamic analysis provides information into a suitable Dynamic Amplification Factor (DAF) for use with simplified modelling approaches. Based on the range of structures considered, the maximum increase in deflections as a result of a sudden removal was 1.62 times the static case, this is less than the commonly used factor of 2.0. Additionally, this factor reduces as the nonlinearity increases due to further damage, with a smallest DAF calculated at 1.39. This factor can be reduced further if the column is not removed instantaneously. Finally, the material strengthening effect, due to high strain rates, was considered with the conclusion that as such effects only make a limited increase in the capacity of the slab and may be conservatively ignored. In conclusion, RC flat slab structures are capable of resisting progressive collapse after the loss of a column. This is primarily due to their ability to develop ALPs. However, while flexural damage is usually fairly minimal, progressive punching shear failure is a critical design condition as it may result in a complete collapse. Furthermore, the inertial effects involved after a sudden removal can increase the damage sustained, although current design methods may be over conservative.

The present paper present a taxonomic study of the Brazilian species of the genus Aspilia Thou. (Compositae-Heliantheae). AlI taxa involved, and their geografical distribution, are described, discussed, and illustrated. The material examined is listed, and a dichotomus key for the identification of the Brazilian species of Aspilia, is presented. About 1200 exsiccatae, from 22 Brazilian and 16 foreign herbaria, were studied, 61 species are recognized, 19 of which are new to science. The genus is maintained in the tribe Heliantheae. The genus Aspilia can be distinguished from other genera of Heliantheae in having ligulate and neuter radial flowers with two or three conspicuous veins, and central achenium slightly compressed, with a scar at its base, from the carpophore. The genus, with about 155 recognise species, occurs in Afr ica, Madagascar, and Tropical. America from Mexico to Argentina. In Brazil, most species are found in "ambientes rupestres", in "cerrados", in gallery forests, and in "restinga", mainly in the states of Minas Gerais, Goiás, Bahia, Mato Grosso, and Mato Grosso do Sul / Expõe-se neste trabalho um estudo taxonômico das espécies brasileiras do gênero Aspilia Th. (Compositae-Heliantheae). Os taxa, com suas respectivas distribuições geográficas, são descritos, discutidos e ilustrados.Elaborou-se relação de material examinado e uma chave dicotômica com a finalidade de identificar as espécies brasileiras, muitas das quais apresentam grande afinidade entre si. Com base no estudo de cerca de 1.200 exsicatas, provenientes de 22 herbários nacionais e 16 herbários do exterior, 61 espécies são reconhecidas, das quais 19 são novas. O gênero é mantido na tribo Heliantheae s.l., subtribo Ecliptinae. O gênero Aspilia, além de outras características de menor expressão, pode ser distinguido de outros da tribo por apresentar flores do raio liguladas e neutras, com duas a três nervuras conspícuas e aquênio do disco, levemente comprimido, com cicatriz na base. O gênero com cerca de 155 nomes é encontrado na África, Madagascar e no continenete americano desde o México até à Argentina. - No Brasil, a maioria das espécies se encontra em ambiente rupestre, cerrado, mata de galeria e restinga, principalmente nos Estados de Minas Gerais, Goiás, Bahia, Mato Grosso e Mato Grosso do Sul

The present paper present a taxonomic study of the Brazilian species of the genus Aspilia Thou. (Compositae-Heliantheae). AlI taxa involved, and their geografical distribution, are described, discussed, and illustrated. The material examined is listed, and a dichotomus key for the identification of the Brazilian species of Aspilia, is presented. About 1200 exsiccatae, from 22 Brazilian and 16 foreign herbaria, were studied, 61 species are recognized, 19 of which are new to science. The genus is maintained in the tribe Heliantheae. The genus Aspilia can be distinguished from other genera of Heliantheae in having ligulate and neuter radial flowers with two or three conspicuous veins, and central achenium slightly compressed, with a scar at its base, from the carpophore. The genus, with about 155 recognise species, occurs in Afr ica, Madagascar, and Tropical. America from Mexico to Argentina. In Brazil, most species are found in "ambientes rupestres", in "cerrados", in gallery forests, and in "restinga", mainly in the states of Minas Gerais, Goiás, Bahia, Mato Grosso, and Mato Grosso do Sul / Expõe-se neste trabalho um estudo taxonômico das espécies brasileiras do gênero Aspilia Th. (Compositae-Heliantheae). Os taxa, com suas respectivas distribuições geográficas, são descritos, discutidos e ilustrados.Elaborou-se relação de material examinado e uma chave dicotômica com a finalidade de identificar as espécies brasileiras, muitas das quais apresentam grande afinidade entre si. Com base no estudo de cerca de 1.200 exsicatas, provenientes de 22 herbários nacionais e 16 herbários do exterior, 61 espécies são reconhecidas, das quais 19 são novas. O gênero é mantido na tribo Heliantheae s.l., subtribo Ecliptinae. O gênero Aspilia, além de outras características de menor expressão, pode ser distinguido de outros da tribo por apresentar flores do raio liguladas e neutras, com duas a três nervuras conspícuas e aquênio do disco, levemente comprimido, com cicatriz na base. O gênero com cerca de 155 nomes é encontrado na África, Madagascar e no continenete americano desde o México até à Argentina. - No Brasil, a maioria das espécies se encontra em ambiente rupestre, cerrado, mata de galeria e restinga, principalmente nos Estados de Minas Gerais, Goiás, Bahia, Mato Grosso e Mato Grosso do Sul

The arch is usually described in engineering text books as a curved structure, which under the action of vertical loads, exerts an inclined pressure on its supports. It is really intermediary between a curved beam and a curved strut, approaching the former or the latter according as the bending stresses or compressive stresses are correspondingly predominant. The theory of masonry arches has been, and is now in an unsatisfactory state owing to several reasons. Firstly, the materials of construction are generally cheap, and consequently, economy is not considered important. Secondly, up to quite a short time ago, investigators persisted in a type of theory which was admittedly indeterminate. Thirdly, the enormous advance in the production of iron and steel in the Nineteenth Century gave a great impulse to the erection of structures made of these materials, and so, although engineers began to be alive to the importance of both experimental data and theory in structural design, the masonry arch was somewhat neglected. Fourthly, there were so many arches already built, that the dimensions of new arches were almost always based on these existing ones to, the detriment of research. There is, therefore, up to the present practically no useful data on which to base a satisfactory theory. Empirical results are certainly necessary as the conditions under which an arch bears its load are too varied to admit of treatment by pure theory.