307 research outputs found
Stress-strain model for high strength concrete confined by FRP
No full textDuctility of High Strength Concrete (HSC) columns can be increased by lateral confinement. The conventional confinement with steel reinforcement may not always be adequate to provide the ductility levels desired by the engineer. The lateral confinement by FRP can provide significantly higher confinement stresses than the conventional steel reinforcement, and convenient for repair applications. Confining pressure applied by FRP is a function of the lateral strain of concrete. Therefore information of axial stress, axial strain and lateral strain relationships of concrete is fundamental in the design of confinement. Many existing models are based on test results with low confining pressures which are not suitable for modelling FRP confined concrete. The authors present a model in this paper which is suitable for use in designing FRP confinement of concrete. Model results are compared with experimental results of FRP confined columns. The results demonstrate the model is suitable for this use
Re-life of buildings - decision support tools for maximising project efficiency
No full textThis paper describes the process adopted in developing an integrated decision support framework for planning of office building refurbishment projects, with specific emphasize on optimising rentable floor space, structural strengthening, residual life and sustainability. Expert opinion on the issues to be considered in a tool is being captured through the DELPHI process, which is currently ongoing. The methodology for development of the integrated tool will be validated through decisions taken during a case study project: refurbishment of CH1 building of Melbourne City Council, which will be followed through to completion by the research team. Current status of the CH1 planning will be presented in the context of the research project
Towards a Rule-based matrix for evaluating distress mechanisms in bridges
No full textOne of the key issues facing public asset owners is the decision of refurbishing aged built\ud
assets. This decision requires an assessment of the “remaining service life” of the key\ud
components in a building. The remaining service life is significantly dependent upon the\ud
existing condition of the asset and future degradation patterns considering durability and\ud
functional obsolescence. Recently developed methods on Residual Service Life\ud
modelling, require sophisticated data that are not readily available. Most of the data\ud
available are in the form of reports prior to undertaking major repairs or in the form of\ud
sessional audit reports. Valuable information from these available sources can serve as\ud
bench marks for estimating the reference service life. The authors have acquired similar\ud
informations from a public asset building in Melbourne. Using these informations, the\ud
residual service life of a case study building façade has been estimated in this paper based\ud
on state-of-the-art approaches. These estimations have been evaluated against expert\ud
opinion. Though the results are encouraging it is clear that the state-of-the-art\ud
methodologies can only provide meaningful estimates provided the level and quality of\ud
data are available. This investigation resulted in the development of a new framework for\ud
maintenance that integrates the condition assessment procedures and factors influencing\ud
residual service lif
Comparison between ACI 440 and FIB 14 design guidelines in using CFRP for strengthening of a concrete bridge headstock\ud
No full textThis paper compares and reviews the recommendations and contents of the guide for the\ud
design and construction of externally bonded FRP systems for strengthening concrete structures reported\ud
by ACI committee 440 and technical report of Externally bonded FRP reinforcement for RC structures (FIB\ud
14) in application of carbon fiber reinforced polymer (CFRP) composites in strengthening of an aging\ud
reinforced concrete headstock. The paper also discusses the background, limitations, strengthening for\ud
flexure and shear, and other related issues in use of FRP for strengthening of a typical reinforced concrete\ud
headstock structure such as durability, de-bonding, strengthening limits, fire and environmental conditions.\ud
A case study of strengthening of a bridge headstock using FRP composites is presented as a worked\ud
example in order to illustrate and compare the differences between these two design guidelines when\ud
used in conjunction with the philosophy of the Austroads (1992) bridge design code
Decision support in using fibre reinforced polymer (FRP) composites in rehabilitation of concrete bridge structures
No full textThis paper compares and reviews the recommendations and contents of the guide for the\ud
design and construction of externally bonded FRP systems for strengthening concrete structures reported\ud
by ACI committee 440 and technical report of Externally bonded FRP reinforcement for RC structures (FIB\ud
14) in application of carbon fiber reinforced polymer (CFRP) composites in strengthening of an aging\ud
reinforced concrete headstock. The paper also discusses the background, limitations, strengthening for\ud
flexure and shear, and other related issues in use of FRP for strengthening of a typical reinforced concrete\ud
headstock structure such as durability, de-bonding, strengthening limits, fire and environmental conditions.\ud
A case study of strengthening of a bridge headstock using FRP composites is presented as a worked\ud
example in order to illustrate and compare the differences between these two design guidelines when\ud
used in conjunction with the philosophy of the Austroads (1992) bridge design code
Strategies for minimising the whole of life cycle cost of reinforced concrete bridge exposed to aggressive environments
No full textn design of bridge structures, it is common to adopt a 100 year design life. However, analysis of a number of case study bridges in Australia has indicated that the actual design life can be significantly reduced due to premature deterioration resulting from exposure to aggressive environments. A closer analysis of the cost of rehabilitation of these structures has raised some interesting questions. What would be the real service life of a bridge exposed to certain aggressive environments? What is the strategy of conducting bridge rehabilitation? And what are the life cycle costs associated with rehabilitation? A research project funded by the CRC for Construction Innovation in Australia is aimed at addressing these issues. This paper presents a concept map for assisting decision makers to appropriately choose the best treatment for bridge rehabilitation affected by premature deterioration through exposure to aggressive environments in Australia. The decision analysis is referred to a whole of life cycle cost analysis by considering appropriate elements of bridge rehabilitation costs. In addition, the results of bridges inspections in Queensland are presente
Effectiveness of variably tuned liquid damper in suppressing dynamic excitation
No full textTuned liquid damper (TLD) is a special type of auxiliary damping device which relies on the sloshing of a liquid (water) in a container to counteract the forces acting on the structure. In this paper a new kind of TLD with some movable baffles is experimentally studied. These movable baffles change the dynamic characteristics of the TLD, specially frequency and damping. Response of a five storey benchmark building was utilized to investigate the efficiency of variably tuned liquid damper (VTLD) under dynamic excitations. By observing the performance of VTLD this study investigates the effects of probable mistuning by changing the depth of water and frequency ratio as well. The damping ratios of the building in several conditions of baffles angles were evaluated using logarithmic decrement technique. The results show that one can enhance the performance of TLDs by installing some movable baffles and overcome probable mistuning of the TLD. © 2011 Taylor & Francis Group, London
Evaluation of creep, shrinkage and modulus of elasticity models for high strength concrete
No full textIn the literature and codes of practice, various equations are recommended for calculating typical material properties of compressive strength, elastic modulus, shrinkage strain and creep coefficient of concrete. The various equations are reported to give significantly different estimates leading to great uncertainty, particularly when estimating axial shortening of vertical concrete elements such as columns, cores and walls in a tall building that typically utilises high strength concrete. The main aim of this paper is to evaluate the various equations from relevant concrete codes and literature used to estimate the material properties of both normal strength concrete (NSC) and high strength concrete (HSC). Selected prediction equations are also compared to recent laboratory results from site delivered HSC
Thermogravimetry analysis of deteriorated timber bridge elements
No full textManagement of timber bridges in Australia is mostly carried out by local councils. Most councils need to make informed decisions based on visual inspections. However, these have been proven to be inadequate mainly due to the lack of scientific evaluation. This paper presents the results of Thermogravimetry (TGA) carried out on a case study bridge in the western region of Melbourne
Dynamic characteristics of reinforced concrete beams
No full textDynamic characteristics of simply supported reinforced concrete (RC) beams of 1200 x 150 x 100 mm were nvestigated by finite element method (FEM), assuming inear behaviour
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