The importance of studying the behavior of the progressive collapse of steel frame buildings has been demonstrated by the loss of almost 3000 people in the World Trade Center (WTC) September 11th attack. Numerous studies have established that the alternate load path method (ALPM) of analysis can be used to study the robustness of a structure in order to prevent the collapse from occurring. The method utilises an event-independent approach, where the actual load arising from the complicated triggering event is not considered. The method proposes the removal of one or more load bearing elements of a structure, such as a column, thus causing the structure to be susceptible to dynamic effects. However, the current ALPM practice of using a single removal time in representing different extreme events only provides a limited assessment of the overall structural robustness. Furthermore, the location of the column to be removed also requires careful consideration, since different removal locations will initiate different responses from the structure. This study proposes two approaches in the effort to further enhance the utilisation of the alternate load path method. Firstly, the study proposes the use of a removal time variation during the column removal process to obtain a more comprehensive view of the structural resistance to progressive collapse. In addition to the removal time, different modelling approaches are used by considering different elements - beam elements and shell elements. These are herein extensively investigated. Secondly, a systematic algorithm was developed using MATLAB and the SAP 2000 finite element software version 15, for selecting the location of columns to be removed so as to determine which removal location would cause the most distress to the structure. The selection of the column location is based on newly proposed damage assessment criteria developed in this work, which are independent of the column grid spacing and consequently their use is more general and suitable for all types of buildings. The finite element method was used as an investigative tool. The general finite element package SAP 2000 version 15 and ABAQUS/standard version 6.10 have been chosen to carry out the detailed column removal analyses. The effect of varying the removal time and the modelling approach in a column removal analysis was first investigated on a small scale structure, namely, a two bay steel frame structure using a nonlinear dynamic implicit analysis. In order to evaluate the effectiveness of the proposed algorithm, the analysis was than extended to more detailed structures encompassing two types of 3-dimensional ten storey steel frame finite element models, namely a moment resisting frame and a braced frame. The results from both the preliminary and the primary models clearly demonstrate that the faster column removal time causes larger dynamic effects in telms of veliical displacement and energy manifestation in all the numerical models. A clear implication of these results is that an accurate and comprehensive assessment of structural robustness using ALPM necessitates the use of a removal time range, not just a single removal time. With regards to the modelling approaches, modelling the beam element without a proper offset i.e. based upon the centreline to centreline geometry of the beam element model may overestimate the actual stiffness of the structure. For the location of the column to be removed, the proposed algorithm has successfully determined the worst column locations that cause the maximum response to the two primary models. The proposed algorithm has the potential to be a very useful enhancement to the current ALPM procedure. It can be concluded after a detailed investigation of the results presented in this study, that it is crucial to carefully and systematically select the position of columns for removal, which would result in the most significant response in the structure, and then to investigate the structural response under various removal times for those columns.

No description available.

No description available.

The level of moisture a construction is exposed to may have an adverse effect on health and structure. Using straw, an organic material, as the construction medium, introduces concerns about biodegradability and spore germination, highlighting the uncertainties surround the level at which straw is susceptible to decay. A physical model is presented in this thesis offering a method by which to quantify and evaluate the risk posed to straw bale constructions from moisture. The model, utilising the development of an innovative Risk Assessment System based on fuzzy logic, is supported by empirical research conducted in static and dynamic environments. The model relies upon the interpretation of data provided by monitoring devices, and an understanding as to the complexities of vapour transition through a straw bale and the interaction of moisture within. Using commonly descriptive terminology to describe the risk posed to the straw, the model, is capable of providing a greater understanding of straw bale construction and advising interested parties on potential weaknesses, taking into account: moisture, temperature, historic and predicted environmental conditions, limitations of analytical techniques, and the effect of direct sunlight. The concept of the model is to provide an early response mechanism to warn of the potential of adverse effects and thereby averting the need for destructive investigation and remedial action. The interpretation of monitoring device data underpins the research conducted in this thesis, prior to which, there existed a gap in knowledge concerning the understanding of how moisture interacts with straw. The development of a novel compressed straw probe, as a monitoring device, offers the ability to establish an immediate moisture content measurement using a resistance meter, or of recent moisture levels using gravimetric analysis, supported by olfactory and visual verifications, enhancing the accuracy. Monitoring device results, compensated for temperature and density by equations developed from empirical data, are applied to a contour plot, via the Risk Assessment System, to provide an diagrammatic interpretation of the risk posed. Any potential problem is then flagged and a report generated providing advice. Other contributions to knowledge made within the thesis consist of: monitoring device evaluations, determining the rate at which moisture is transferred through a bale, defining the interaction of moisture with straw, the capacity for moisture storage of renders and the subsequent implications, identification of transient moisture and the effect of solar gain, resistance meter calibration, and the hygroscopic, hydrophobic and hydrophilic tendencies of straw.

In Europe it is estimated that around 50% of infrastructure funding is currently utilised for repair and maintenance of structures. In the UK, chloride ingress into concrete and subsequent corrosion of reinforcement is responsible for the premature deterioration of majority of concrete structures. This can be attributed to two main factors: (1) inadequate concrete specification; and (2) lack of performance-focused maintenance strategies that ensures a required service life. Several service life models (SLMs) exist for studying the chloride induced corrosion and these are great tools for understanding how a concrete will perform in a given exposure environment. However, only very few designers use SLMs and the main reasons for the lack of uptake of this approach are: (1) the complex nature of the models; (2) lack of explanation and guidance on the role of input parameters; and (3) the lack of guidance on the interpretation of outputs. This prompted a study into the benefits and shortcomings of SLMs in order to understand the reasons why this methodology has not been integrated fully into practices in the industry. In this thesis a new approach for identifying the most critical input parameters that could be used in service life modelling of concrete structures which are exposed to chloride exposure environments was proposed on the basis of sensitivity analysis of each parameter on the service life. This approach was established to simplify the process of modelling by reducing complex and numerous input parameters to easily definable (for designers) and/or measurable ones (for asset owners), termed in this thesis as Key Performance Indicators (KPls). The use of KPls was demonstrated through laboratory and field investigations to allow engineers to specify concrete based on expected performance in the chloride exposure environment or asset managers to determine the remaining service life of concrete structures in service.

Galleting is the practice of inserting chips of stone into the mortar joints of masonry. Its long and enduring history is not explained by the belief that it is primarily decorative and a convincing purpose is sought. Information is not only in short supply but also inconsistent in the unsubstantiated views expressed. A detailed understanding of galleted masonry is necessary for its correct conservation. To better understand the subject a wide range of galleted mortar joints were photographed, questionnaires were sent to professionals and their views correlated and a separate convenience survey conducted. The geographical spread of galleting was plotted and the origins of galleting sought through secondary data sources. Finally, a series of new and innovative tests was devised to establish the influence of gallets on the strength and durability of lime mortar joints. A definition and taxonomy was devised to aid positive identification of galleting. Lime mortar joints are susceptible to early failure due to the slow progression of carbonation, exposure to weathering and the build-up of stresses. It was found that the incorporation of gallets into joints resolved this by significantly increasing compressive strength and reducing shrinkage. The gallets, being stronger than the mortar, accommodate the shear stresses and minimise the risk of failure. At the same time, they increase the durability of a wall and reduce damage due to weathering. Results show that galleting has been in use for many centuries, is more widespread than is generally recognised and almost certainly started out as a significant structural element in masonry construction. The true purpose of galleting and its relationship to the mortar in which it is bedded throws new light onto the use of non-hydraulic lime mortar in construction and conservation work. This will help conservationists and operatives to understand the complex nature of this traditional form of building.

Masonry is a composite material made of masonry units bonded together with mortar. A large number of historical buildings constructed using masonry can be found all over the world. Little or no seismic loading was considered when they were built. Therefore, masonry structures often need to be retrofitted or strengthened. This research proposed a new strengthening approach using a collar-jointed technique. Namely, the approach is implemented by building another masonry wall parallel to the existing single-leaf wall and bonding the two together using a mortar collar joint. Furthermore, collar-jointed masonry wall construction is also a popular construction system in reality. This thesis considers two different types of collar wall strengthening applications: pre- and post-damaged walls. The results found out that the pre-damaged strengthening could improve the lateral resistance by about 50% while the post-damaged retrofitting can only restore the initial strength. A simplified micro-scale finite element model for fracture in masonry walls was developed. The mortar joints and the brick-mortar interfaces are taken to have zero-thickness. The bricks were modelled as elastic elements while the brick-mortar interfaces were represented using a Mohr-Coulomb failure surface with a tension cut-off and a linear compression cap. One feature of the research was to identify the material parameters for the constitutive model. The material parameters were tuned by minimizing the difference between the experimental and numerical results of a single leaf wall panel. The model was then validated by assigning the parameters to the single-leaf masonry wall as well as to the double-leaf wall to predict its mechanical behaviour. Good agreement with experimental results was found. Furthermore, masonry is also widely used in the form of infill panels within RC frames. Therefore, the collar-jointed technique has also been extended and applied to the infilled RC frame. The numerical results showed that the collar-jointed technique could provide some benefits to the composite structure.

Soil based construction materials (SBCMs) are formed of a mixture of gravel, sand and clay which, when mixed with water, may be used for construction. They can be an environmentally-friendly alternative to more traditional construction materials such as concrete and fired brick. SBCMs commonly incorporate foreign material into the soil to enhance the material properties. Many guides on SBCM construction advocate the use of cement as a stabiliser to strengthen the material, which detracts from the environmental credentials that earthen construction materials possess. Alternatives methods to strengthen SBCMs are therefore needed. In this thesis, waste wool fibres from a carpet manufacture are investigated as a potential alternative fibrous reinforcement in rammed earth (RE), and its effect on the behaviour of stabilised and unstabilised RE is assessed. Compressive tests, shear tests and splitting tests are performed to study the effect of fibrous (wool) and chemical (cement) stabilisation on RE, and recommendations on further use of these materials are made. Tests are also performed to investigate the shrinkage of different clays (bentonite and kaolinite) used in RE when mixed with sand or wool, in order to determine the effects of these materials on shrinkage behaviour. Finally, advice is provided regarding the use of fibrous reinforcement in SBCMs, which is applicable to both the SBCM industry and research, and new and pre-existing research areas are identified to prompt further study.

In current practice a plane stress framework comprising elastic moduli and Poisson’s ratios is most commonly used to represent the mechanical properties of architectural fabrics. This is often done to enable structural analysis utilising commercially available, non-specialist, finite element packages. Plane stress material models endeavour to fit a flat plane to the highly non-linear stress strain response surface of architectural fabric. Neural networks have been identified as a possible alternative to plane stress material models. Through a process of training they are capable of capturing the relationship between experimental input and output data. With the addition of historical inputs and internal variables it has been demonstrated that neural network models are capable of representing complex history dependant behaviour. The resulting neural network architectural fabric material models have been implemented within custom large strain finite element code. The finite element code, capable of using either a neural network or plane stress material model, utilises a dynamic relaxation solution algorithm and includes geodesic string control for soap film form-finding. Analytical FORM reliability analysis using implied stiffness matrices' derived from the equations of the neural network model has also been investigated.

Climatically induced cycles of temperature and moisture content may result in the weathering of building stone through various mechanisms. It is now increasingly possible that, in response to changing climatic conditions, patterns of moisture movement along with thermal gradients within building stone will significantly be altered and increase in complexity. To understand the ongoing dynamically varying micro-environmental conditions in and around stone masonry and to predict future trends, there is a growing need to continuously monitor environmental parameters that control weathering mechanisms in stone. Despite rather advanced non-destructive methods currently used for assessing the deterioration process in stone, the fate and extent of inner contamination remains largely unaccounted for by such methods. Therefore, real-time monitoring of spatial and temporal variations in environmental parameters of building stone is invaluable, not only from the standpoint of economic planning and maintenance, but also on cultural, technical and scientific grounds. This thesis studies the spatial and temporal variations in moisture and temperature conditions in building stone using electrical resistance based sensors. The experimental work reported in this thesis has been carried out to simultaneously address two strands of research viz., 1) To study temperature and moisture changes in building stone in response to variations in simulated and natural micro-environmental conditions and 2) To develop electrical resistance based monitoring technique for long-term monitoring needs of stone masonry structures.