https://www.um.edu.mt/library/oar/handle/123456789/76307 2026-04-04T07:29:34Z 2026-04-04T07:29:34Z https://www.um.edu.mt/library/oar/handle/123456789/76616 2021-06-01T14:34:54Z 2020-01-01T00:00:00Z

Title: The potential of gridshells with irregular topologies Abstract: Gridshells have emerged as an elegant and aesthetic solution for the span of large distances. Their design tends to feature a regular triangular or quadrilateral topology. Recent gridshells akin to the glass roof at the Dutch Maritime Museum, make use of irregular topologies to extend the limits of such structures. Coupled with advancements in technology, irregular gridshells have become more cost efficient, however, research on the subject is still in its infancy. The objective of this study is to investigate gridshells with an irregular topology known as kagome, in comparison to the triangular topology. This dissertation explores the effect of the regularity or lack thereof in the topology of a gridshell with respect to varying section sizes and grid densities. The performance of both topologies was discussed – both in terms of structural and cost efficiency. The structural performance is measured in terms of its buckling load, using a finite element software to carry out an eigenvalue buckling analysis. It is found that the for the same self-weight, the kagome pattern provides comparable buckling loads to the triangular, especially for finer grid densities and larger sections. The buckling shapes exhibit the intrinsic rigidity of the triangular, which cannot be matched to any other topology. Since the kagome pattern features triangular panels, they significantly improve its in-plane shear strength and activate membrane action within the kagome pattern. It is also proven that the main form of buckling was generally shell buckling, at times coupled with other forms of instability. The selection of section size should be compared on the basis of the ratio with respect to the span of the gridshell rather than the length of the member. In terms of overall cost efficiency, it is highly probable that for the same cost, the kagome pattern buckles at a larger buckling load compared to the triangular. This is because the triangular topology is attributed to a high node complexity which governs the total cost of the gridshell. For coarser grid densities, the kagome functions more like a group of beams connected together with rigid joints. In fact, this explains its reliance out-of-plane stiffness. However, it presents new cost-effective and aesthetical possibilities while still performing decently. These results encourage the investigation of new irregular topologies which still feature triangulation to some capacity for in-plane shear strength but outperform the kagome topology. Description: M.ENG.STRUCTURAL ENGINEERING

2020-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/76613 2021-06-01T14:32:06Z 2020-01-01T00:00:00Z

Title: A comparative study for a demolition versus deconstruction case : the use of a ‘polluter’s pay’ legislation as a countermeasure towards unsustainable construction waste practice Abstract: The generation of increasing volumes of Construction and Demolition Waste (CDW) has made its way to become one of the top contributors in the European Union (EU) and local waste streams. This has posed difficulties in various sectors ranging from material scarcity, reduced landfilling spaces and environmental emissions. The purpose of this research paper was to analyse the financial and envrionmental implications posed by two end of life options available for traditional limestone structures in the Maltese Islands. Field research was carried out to obtain primary data on the financial rates of the deconstruction and demolition options within the Maltese construction industry. This was followed by the construction of a Life Cycle Analysis model focusing on the end of life phase of a limestone building, in order to evaluate the respective environmental performance of each option. Whilst it was determined that deconstruction is not financially feasible when compared to its demolition counterpart, it has been identified that it is the more sustainable option of the two. Results showed that for deconstruction to be financially feasible in Malta more than 90% of the total material has to be recovered and sold to third parties, due to the high margin applied over the demolition proceedures. On the other hand, the increase in material recovery through deconstruction showed a constant reduction in the induced envrionmental impacts to a point that deconstruction processes provide net environmental gains. The correlation between the two areas of study was produced in order to provide a ground for possible future CDW policy development. The final rate per nPt of envrionmental impact, that would incentivise the engagement of deconstruction procedures, was estimated to be equal to Euro 2.79; a rate that could be implemented both as a tax rise or rebate. Description: M.ENG.STRUCTURAL ENGINEERING

2020-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/76606 2021-06-01T14:31:02Z 2020-01-01T00:00:00Z

Title: Structural assessment of the blast resistance of Maltese unreinforced masonry construction Abstract: The events at Ronan Point in the 1960s triggered a worldwide endeavour to research further into the capacity of buildings to resist the effect of blast or impulse loads, which previously had not been investigated extensively. Unfortunately, the extent of this research with respect to the local context is rather limited, and there is no definitive quantification of the structural behavior of Maltese buildings in response to blast loads. Of interest is the behavior of the most predominant building type in Malta: the unreinforced masonry (URM) building. This method of construction remains the most common and favoured building method, despite the shift in typology from two-story terraced houses to multi-story structures, including basements and around five floors above street level. The use of unreinforced masonry locally has remained prevalent, but it is inherently problematic when response to lateral loads is considered. Unreinforced masonry walls are notoriously weak under the application of lateral loads, such as seismic actions, and subsequently also blast loads. The scope of this dissertation is to determine the behaviour of local unreinforced masonry walls subjected to accidental out-of-plane loads due to blast using published blast strength data and analytical methods. This study seeks to determine the magnitude of the blast loads that would cause structural failure of URM walls with and without pre-compression. In the light of recent events, where gas leaks were reported in Maltese households throughout the past years, the risk associated with the occurrence of such leaks has been considered in this dissertation, as it is a very real and possible accident that may occur in Maltese households, and has indeed occurred in the past. Previous research related to the local context has considered different typologies and blast sources, and this dissertation continues to build on that body of work and other research related to other dynamic loads. The general blast analysis carried out in this dissertation is coupled with a parametric analysis in order to investigate the behaviour of URM walls with varying masonry units, and mortar strengths. Viable and feasible alternatives to the current method of construction have also been analyzed in order to determine the improvement in the behaviour of URM walls subjected to lateral loading. Research has shown that URM walls in isolation are not able to sustain the pressures and moments resulting from the blasts, for both masonry materials considered and varying mortar strengths. URM building analysis has shown that Globigerina Limestone walls are significantly stronger than Hollow Concrete Block walls in sustaining blast pressures, with the early failure of individual walls within the structure proving to be beneficial to the overall stability of the building. Increasingly asymmetrical typologies have also resulted in worsened strength capacities of the URM building. The use of reinforced masonry walls has proven to be significantly stronger and is therefore recommended for locally constructed masonry buildings. The results of this study have shown that the current local URM construction methodology, combined with increased building heights, has resulted in a building typology which is extremely vulnerable to the occurrence of accidental blast loads. Residential buildings are more at risk due to accidental blasts than intentional blasts. This study also highlighted the observation that local URM buildings are more vulnerable to overall collapse when subjected to seismic loading than when subjected to blast loading, which nevertheless would still cause local damage at the location of the blast loading. Description: M.ENG.STRUCTURAL ENGINEERING

2020-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/76605 2021-06-01T14:29:10Z 2020-01-01T00:00:00Z

Title: Buckling of steel flanged cruciform columns under axial loading Abstract: Doubly symmetric cruciform sections are susceptible to torsional buckling and are therefore not widely used in the construction industry; however, they are becoming more popular when two-way frame action is needed. There is very limited research on the structural behaviour of cruciform columns. In view of this, very little has been done to understand the buckling behaviour of flanged cruciform columns fabricated from beam sections. This dissertation aims to address this literature gap by explaining both the elastic and plastic buckling behaviour of these sections with regards to axial loading. Furthermore, by analysing existing design procedures presented by EN 1993-1-1 (2005), the validity of applying such procedures to the flanged cruciform section are to be questioned. This is done by first performing numerical analysis to a standard steel flanged cruciform section – consisting of a critical load analysis, as well as an inelastic analysis due to initial imperfections. Following this, by making use of LUSAS (2018), a Finite Element structural analysis software package, FEM analysis is performed – consisting of a critical eigenvalue analysis, as well as a non-linear elasto-plastic analysis. Hence, the results obtained from the FEM analysis are compared to the values obtained from the numerical analysis. An experimental test is carried out to allow for the comparison of the theoretical buckling capacity with that obtained from physical experimentation. By using numerical analysis, it was possible to obtain the theoretical critical elastic buckling load, and as expected torsional buckling failure was the predominant mode of buckling for lower values of slenderness, whilst flexural buckling failure would take place for members of higher slenderness. This showed that by making use of Eurocode (‘EN1993-1-1’, 2005) to design flanged cruciform columns there are certain risks involved in the assumptions taken in the design code. Computer analysis with LUSAS (2018) showed that the results confirmed the theoretical findings. Experimental analysis showed different results from what was expected from theoretical and computer analysis; however, due to the limited amount of experimentation further analysis could not be performed. Thus, the dissertation provides a good guideline for structural engineers when designing for steel flanged cruciform columns under axial loading. Description: M.ENG.STRUCTURAL ENGINEERING

2020-01-01T00:00:00Z