Preliminary seismic analysis of fabricated steel frame systems with pin beam-column connections and buckling restrained braces

This study aims to propose an improved fabricated high-rise steel frame system with buckling restrained braces (BRBs) and pin beam-column connections, which is applicable to seismic areas. In this system, damages to the main structural members resulted from earthquake ground motions can be prevented by BRBs which are capable of resisting all the lateral seismic loads, whilst the other structural members are mainly responsible to carry the gravity loads. Having explicit load-carrying characteristics, this system is thought to have a competitive advantage of rapid construction. In this study, a 3D finite element model of a specific fin-plate connection, a typical type of pin beam-column connections, is built and its rotational stiffness is evaluated. Subsequently, a high-rise steel frame model with both BRBs and the fin-plate connections are established. The earthquakeresistant performances of the model under different levels of seismic excitation are analyzed using the nonlinear dynamic time-history method. Numerical results indicate that the proposed system performs elastically under frequent earthquakes, whereas under severe earthquakes the main structural components are well within their capacities. Furthermore, the BRBs show significant energy dissipation capacity under severe earthquakes

Probabilistic evaluation of the seismic performance of a concrete highway bridge in Queensland

Being intraplate, the Australian continent has shown low seismicity in its recorded history. However, Australia has been acknowledged as not completely free from seismic hazard. Performance-based earthquake engineering (PBEE) methodology has been widely developed during the past two decades, and has become a key approach for seismic analysis and design. Yet such an approach has not been implemented in Australian structural codes. Therefore, further research is required to develop a domestic approach for Australian applications. In this study, the seismic capacity of a concrete highway bridge is evaluated through a probabilistic method. For this purpose, an analytical model of a typical highway bridge in Queensland was built in OpenSees. The important seismic responses to be considered include the curvature ductility of columns, and the deformations in bearings and abutments. The main uncertainties are related to the source and ground motion models for potential Australian earthquakes. A set of synthetic intraplate ground motions, which was provided by the GeoscienceAustralian, is anticipated to be used in the generation of future probabilistic ground motion maps for Australia, and is presently used for nonlinear incremental dynamic analyses (IDA). The results of this study in the form of seismic capacity limit-states can be further employed for developing performance-based seismic design and/or seismic risk and fragility analyses of Queensland highway bridges

Comparative analysis of internal and external-hex crown connection systems - a finite element study

The abutment connection with the crown is fundamental to the structural stability of the implant system and to the prevention of mechanical exertion that can compromise the success of the implant treatment. The aim of this study is to clarify the difference in the stress distribution patterns between implants with internal and external-hex connections with the crown using the Finite Element Method (FEM). Material and Methods: The internal and external-hex connections of the Neoss and 3i implant systems respectively, are considered. The geometrical properties of the implant systems are modeled using three-dimensional (3D) brick elements. Loading conditions include a masticatory force of 200, 500 and 1000N applied to the occlusal surface of the crown along with an abutment screw torque of 110, 320 and 550Nmm. The von Mises stress distributions in the crown are examined for all loading conditions. Assumptions made in the modeling include: 1. half of the implant system is modeled and symmetrical boundary conditions applied; 2. temperature sensitive elements are used to replicate the torque within the abutment screw. Results: The connection type strongly influences the resulting stress characteristics within the crown. The magnitude of stress produced by the internal-hex implant system is generally lower than that of the external-hex system. The internal-hex system held an advantage by including the use of an abutment between the abutment screw and the crown. Conclusions: The geometrical design of the external-hex system tends to induce stress concentrations in the crown at a distance of 2.89mm from the apex. At this location the torque applied to the abutment screw also affects the stresses, so that the compressive stresses on the right hand side of the crown are increased. The internal-hex system has reduced stress concentrations in the crown. However, because the torque is transferred through the abutment screw to the abutment contact, changing the torque has greater effect on this hex system than the masticatory force. Overall the masticatory force is more influential on the stress within the crown for the external-hex system and the torque is more influential on the internal-hex system.Griffith Sciences, Griffith School of EngineeringFull Tex

Asian Concrete Model Code (ACMC) and Australian Concrete Structures Standard (AS3600) Compared

Griffith Sciences, Griffith School of EngineeringNo Full Tex

Reinforced and prestressed concrete: Analysis and design with emphasis on the appliction of As 3600-2009

xxxi+427hlm.;26c

On the prevailing construction waste recycling practices : a South East Queensland study

Waste generated from construction and building demolition work constitutes about 68% of all solid waste generated each year in South East Queensland. Consequently, it has created a serious waste management problem. The State Governments of Victoria and New South Wales have been encouraging the use of recycled materials from construction and related waste; they have also promulgated specifications for their use. In Queensland, however, similar regulations are not anticipated in the near future, which explains the lack of funded research conducted in this important arena. This paper presents an evaluation of the prevailing waste recycling practices in Queensland. Nine sites were visited, including two construction sites, three demolition sites, three recycling plants and one landfill in South East Queensland. The difficulties encountered by the recycling programme operators and their associates at these sites are described and the benefits of recycling construction materials are presented. One of the major barriers is that the local councils disallow the use of recycled materials in new construction work. To help rectify these impediments to recycling, recommendations are given to increase the use of recycled construction waste in South East Queensland

Finite element simulation of bone remodelling in the human mandible surrounding dental implant

Dental implant is a biocompatible titanium device surgically placed into the jaw bone to support a prosthetic tooth crown in order to replace missing teeth. However, placement of an implant changes the normal mechanical environment of jawbone, which causes the bone density to redistribute and adapt to the new environment by remodelling. This study aims to predict the density distribution in human jawbone surrounding a dental implant. Based on some popular yet distinctive theories for bone remodelling, a new algorithm is proposed that takes into account both the 'lazy zone' effect and the self-organizational control process. The proposed algorithm is first verified by a two-dimensional (2D) plate model simulating bone tissue, then, a 2D finite element model of implant and jawbone is studied. The effects of two parameters, viz the reference value of strain energy density (SED) and the 'lazy zone' region, on density distribution are also investigated. The proposed algorithm is proven to be effective, and the predicted density distribution patterns correlate well with clinical observations. This study has demonstrated that consideration of the lazy zone is less important than consideration of the stress and strain (quantified as SED) induced within the bone

Comparative analysis of two implant-crown connection systems. A finite element study

The internal and external-hex connections of the Neoss and 3i implant systems, were compared in a three-dimensional Finite Element Analysis. Chewing forces of 200, 500 and 1000N and abutment screw preloads of 110, 320 and 550Nmm were studied. The connection type strongly inß uences the stress proÞ le within the crown, with the external-hex connection exhibiting greater stresses than the internal-hex

Evaluation of multiple implant-bone parameters on stress characteristics in the mandible under traumatic loading conditions

Purpose: The inter-relationships between various implant and bone parameters were evaluated for their influence on the von Mises stress distribution within the mandible using the finite element procedure. The maximum compressive stresses in cancellous and cortical bone were compared to the published stress-strain data to determine bone fracturing status when the maximum (traumatic) loading is applied. Materials and Methods: Parameters considered herein include the implant diameter and length. Also considered are Young's modulus of cancellous bone and that of cortical bone, along with its thickness. The implant-bone system was modeled using two-dimensional plane strain elements, 50% osseointegration between implant and cancellous bone was assumed, and linear relationships were assumed between the stress value and Young's modulus of both cancellous and cortical bone at any specific point within the mandible. Results: Implant length was more influential than implant diameter within cancellous bone, whereas implant diameter was more influential in cortical bone. A ranking of all the parameters indicated that the applied masticatory force had a more significant influence on the stress difference, in both cancellous and cortical bone, than all other parameters. Young's modulus of cortical bone and implant length were least influential in cancellous and cortical bone, respectively. Under traumatic loading, cancellous bone fractured for all parameter combinations. When all parameters were set to their average values, the cortical bone did not fracture under traumatic loading. However, it fractured if all the parameters were all set to the minimum values. Conclusion: Quantitative evaluation and ranking of the major implant and bone parameters will help provide practical guidelines that are useful for the design and testing of dental implants. The study may also be of interest to dental professionals in evaluating possible implant placement options under various clinical scenarios. INT J ORAL MAXILLOFAC IMPLANTS 2010;25:461-47

Stress evaluation of dental implant wall thickness using numerical techniques

Using the Finite Element Method, four implant diameters were evaluated for their effect on the stress distribution at the implant wall. A two-dimensional model of the implant and mandibular bone used triangular and quadrilateral plane strain elements to compute the von Mises stress in the bone with varied masticatory forces and abutment screw preloads. The masticatory force is found to be more influential than abutment screw preload, and implant wall thickness significantly influences the stress magnitude within the implant