Now showing 1 - 10 of 52
  • Publication
    Examination of a novel wavelet based approach for bender element testing
    Accurate determination of shear wave arrival time using bender elements may be severely affected by a combination of near field effects and reflected waves. In most cases, the nearfield effect masks the first arrival and it makes its detection difficult in the time domain. Nevertheless the arrival of a shear wave creates a detectable singular point. This paper tests a recent approach for the assessment of shear wave arrival time by analysing the output signal in the time-scale domain using a multi-scale wavelet transform. Indeed, one can follow the local maxima lines of the wavelet transform modulus across scales, to detect the location of all singularities leading to detection of the first arrival.
      1162
  • Publication
    Numerical Asessment of The Thermal Performance of Structural Precast Panels
    With the increasing cost of energy the need to provide energy efficient buildings continues to grow. In 2003 the EU introduced the Energy Performance of Buildings Directive and this was enforced by all member states by 2006. The need to continually improve thermal performance has lead to member states implementing their own national initiatives, and from next year the National Standards Authority of Ireland will specify that all certified sandwich panel products comply with the incoming building regulations. The incoming building regulations stipulate that all sandwich panels achieve a U-value of 0.15 W/m2K, a reduction from the current value of 0.25 W/m2K. This is a significant challenge and requires that there be no significant heat loss through the panel. This paper presents the results of a collaborative project with a sandwich panel manufacturer whereby the thermal performance of a number of concrete panels was assessed. Each sandwich panel contained an inner concrete wythe of 150mm thickness, a 120mm layer of phenolic foam insulation and a 90mm thick outer layer of concrete. For structural reasons it is necessary to use connectors between the inner and outer concrete wythes, but these connectors have the potential to allow heat loss. In this study 2 connector types were used: 1 manufactured using FRP, the other with stainless steel. A control (non-structural) panel was manufactured containing no connectors. The thermal performance of each panel was assessed through experimental hot-box testing to determine U-values. This was complemented by a series of images taken using a thermal camera to show areas of heat loss. In addition the U-values were also determined using a theoretical numerical approach and a thermal finite element analysis (using MSC Patran) was conducted to determine the heat flux through the panel. The results showed that the connector type has a significant influence on the thermal performance of the sandwich panels, and that those containing steel connectors were not capable of providing the required U-value. The relative performance of the various panel types was consistent between analysis methods, as the finite element, the numerical and experimental approaches were in agreement. In addition, the heat losses observed through the thermal imaging camera were consistent with the heat losses predicted by the finite element analysis. It is proposed then that the use of numerical and finite element approaches has a valuable role in the design of thermally efficient sandwich panels. The experimental testing required is time consuming and requires significant effort. The analysis approach described above will make the design process more efficient and facilitate the construction of energy efficient buildings.
      659
  • Publication
    Biochemical attack on concrete in wastewater applications : a state of the art review
    The costs associated with the provision and maintenance of drinking water and wastewater infrastructure represents a significant financial demand worldwide. Maintenance costs are disproportionately high, indicating a lack of adequate durability. There remains a lack of consensus on degradation mechanisms, the performance of various cement types, the role of bacteria in the corrosion process associated with wastewater applications and testing methodologies. This paper presents a review of the literature, outlining the various research approaches undertaken in an effort to address this problem. The findings of these varying approaches are compared, and the different strategies employed are compiled and discussed. It is proposed that a key step in advancing the understanding of the associated deterioration mechanism is a combined approach that considers the interaction between biological and chemical processes. If this can be achieved then steps can be taken to establishing a performance-based approach for specifying concrete in these harsh service conditions.
      8315
  • Publication
    Digital Interoperability for the Facilities Management Domain: a Review of Semantic Web-based Approaches
    The use of Semantic Web-based Technologies (SWT) to support digital Facilities Management (FM) activities has been shown to address interoperability challenges between disciplinary stakeholders. By establishing shared understanding through ontologies, eliminating precarious file exchanges and democratising participation through non-proprietary technologies, SWTs are receiving growing interest from the research community. Despite this, no comprehensive review exists which analyses works with a specifc focus on the FM domain. This paper reviews 35 academic works and provides a broad discussion around academic and industry initiatives in SWTs for the FM domain, identifying research gaps and future directions of interest. We find that SWTs are already being used by FM practitioners and that implementation is highly case-specific and thus, developments need to be flexible and user-oriented in their design. This work towards a comprehensive domain review provides a useful reference for others in the field as well as informing our own future research activities.
      9
  • Publication
    Developing braided FRP reinforcement for concrete structures
    (Civil Engineering Research Association of Ireland, 2016-08-30) ; ;
    In recent years, significant research has been conducted, by both industry and academia, into the optimum development and use of Fibre Reinforced Polymer composite materials in infrastructure. In particular, it is widely recognised that FRPs have the potential to replace conventional internal steel rebars in concrete reinforcement and offer performance benefits related to their advanced properties, such as corrosion resistance, high tensile strength etc.A review of the available literature indicates that brittle behaviour of FRP can significantly decrease the expected ultimate load capacity and, thus have a negative effect on structure¿s long term durability. However, selecting braiding as manufacture technique and enhancing flexural capacity and shear strength through additional helical reinforcement, could provide structure with the additional ductility needed to prevent a brittle failure. Furthermore, the impact of deterioration mechanisms, focusing on the interaction between FRP and concrete in a structure, is an aspect for further investigation via laboratory testing and advanced analysis.This study summarises the results of research on structural design and manufacture methods of FRP composite materials by presenting new configuration and types of FRP reinforcement in order to encourage the use of these promising materials in construction industry.
      497
  • Publication
    Use of post-installed screws in the compressive strength assessment of in-situ concrete
    In the structural evaluation of existing concrete structures, concrete strength is an important parameter that influences the quality of the overall assessment. Non-destructive tests (NDTs) allows the inspection of larger areas of concrete at lesser cost and time than coring and provides more reliable information than visual inspection. The low reliability of common NDTs in the assessment of compressive strength of concrete limits the use of NDTs in the practical field. A new technique, post-installed screw pullout (PSP) test, based on the modified pullout of post-installed screw, is presented in this paper. The screw transfers the load to the concrete through bearing on the threads. During the complete pullout failure mode, the failure pattern involves local crushing of concrete under the threads. The PSP test was investigated in mortar and concrete to study different factors; compressive strength, presence of aggregates, and the types of aggregate. Mortar was considered to be a homogenous material and thus taken as a baseline for comparing the effect of aggregate type. Experimental studies showed that aggregates play a significant role in the assessment of compressive strength by PSP test, and a better correlation with compressive strength was observed when concretes with different aggregates were analysed separately. In the strength assessment, the degree of variability of the PSP test in terms of R-squared value, standard deviation, coefficient of variation, and RMSE for mortar and concrete with brick chips and lightweight aggregates was found to be low; however concrete with limestone aggregate showed higher variability in the test results. The study confirms that the PSP test is a viable test method with the potential to be reliable and reasonably accurate, yet cost effective; it can also contribute to the reduction of the uncertainty in the assessment of compressive strength of in-situ concrete.
      313
  • Publication
    Mechanical characterisation of braided BFRP rebars for internal concrete reinforcement
    This study investigates the tensile behaviour of basalt fibre reinforced polymer (BFRP) composites that were developed using braiding as a manufacturing technique. Those materials will be introduced in concrete reinforcement applications. Three BFRP rebar sizes with a circular constant cross section and different braided configurations are developed and characterised with respect to their internal architecture. The braid angle on each layer of the rebar, varying from 10◦ to 45◦, is an important parameter that has a direct impact on its performance characteristics. The effective longitudinal in-plane modulus (ExFRP) of each braided sample is calculated numerically using the classical laminate theory (CLT) approach and then, tensile tests are performed according to the relevant standard. Comparisons between analytical and experimental data demonstrate a significant influence of braiding parameters, like braiding angle and number of braiding layers, on the mechanical properties of BFRP rebars. In addition, it is noteworthy that all predicted moduli determined with CLT numerical approach are found to be higher than the test results and overestimate rebar’s stiffness, most probably due to the degree of undulation from braiding process.
      285
  • Publication
    The structural reliability of bridges subject to time-dependent deterioration
    The reliability of the structural performance of any given structure is affected by both in-service loading and material deterioration due to environmental attack. They must be evaluated at any given time in order to compute lifetime probability of failure. This paper presents an innovative methodology to derive the structure lifetime load effect due to existing traffic using a statistical tool known as Predictive Likelihood. Loss of resistance due to corrosion originated by chloride ingression is also taken into account. Finally the lifetime probability of failure is evaluated via the application of a time-discretization strategy
      2148
  • Publication
    The CRITHINKEDU European Course on critical thinking education for university teachers : from conception to delivery
    Within the scope of the CRITHINKEDU project1, this intellectual output (Output 3) reports the experience of conceiving and delivering a European training course on Critical Thinking (CT) education for university teachers. It draws on the proposal of the “European inventory of critical thinking skills and dispositions for the 21st century” and the “Preliminary guidelines for quality in critical thinking education” - both presented in the two previous intellectual outputs of the project (Dominguez, 2018a, 2018b). This report is targeted to each leading partner institution or to any Higher Education (HE) institution which desire to later replicate this training course at the local level, to faculty staff interested in the implementation of CT teaching practices and learning activities in their classroom. Deployments within the CRITHINKEDU project will be carried-out as part of the fourth and following intellectual output (Output 4).
      447