Compressive membrane action in reinforced concrete beams

University of Technology Sydney. Faculty of Engineering and Information Technology.Research studies have demonstrated that membrane action is primarily a compressive load carrying mechanism that can significantly improves the load-bearing capacity of reinforced concrete beams during extreme loading scenarios such as column loss. However, the behaviour of reinforced concrete (RC) beam assemblages under membrane action has not been thoroughly explored and therefore, the development of the compressive (arching) and tensile (catenary) membrane actions in RC beams should be investigated further by experimental and analytical studies. Membrane action is affected by various parameters such as compressive strength of the concrete, reinforcement ratio and transverse reinforcement of the beam. However; previously conducted researches indicate that compressive membrane (arching) action is not considerably influenced by reinforcement ratio which was shown to be the critical parameter in development of the tensile membrane (catenary) action. Also, both translational and rotational stiffness of end supports have significant influence on development of membrane action. Development of membrane action in RC members is typically associated with geometrical as well as material nonlinearities (including concrete cracking and crushing, reinforcing bar yielding and fracture) and due to these strong nonlinearities, most of the existing implicit finite element (FE) models and simplified analytical methods fail to adequately capture the compressive and tensile membrane behaviour of RC elements. The main focus of this research project is to experimentally and numerically investigate development of membrane action in RC beam assemblages. In the experimental program, influence of various parameters including concrete compressive strength, reinforcement bar arrangement and ratio and boundary conditions on the membrane response of RC beam assemblages following a column loss scenario are investigated. Furthermore, two different classes of nonlinear FE models, i.e. a 1D discrete frame and a continuum-based FE models are developed and data obtained from the experimental program are employed to verify and validate the developed FE models. Using a simplified approach, the influence of steel bar rupture is incorporated into the formulation of an existing flexibility-based frame element and it is shown that the proposed strategy has the ability to adequately model the rupture of steel bars and its implications at global level

The Impact of Railway Stations on Residential and Commercial Property Value: A Meta-analysis

Railway stations function as nodes in transport networks and places in an urban environment. They have accessibility and environmental impacts, which contribute to property value. The literature on the effects of railway stations on property value is mixed in its finding in respect to the impact magnitude and direction, ranging from a negative to an insignificant or a positive impact. This paper attempts to explain the variation in the findings by meta-analytical procedures. Generally the variations are attributed to the nature of data, particular spatial characteristics, temporal effects and methodology. Railway station proximity is addressed from two spatial considerations: a local station effect measuring the effect for properties with in 1/4 mile range and a global station effect measuring the effect of coming 250 m closer to the station. We find that the effect of railway stations on commercial property value mainly takes place at short distances. Commercial properties within 1/4 mile rang are 12.2% more expensive than residential properties. Where the price gap between the railway station zone and the rest is about 4.2% for the average residence, it is about 16.4% for the average commercial property. At longer distances the effect on residential property values dominate. We find that for every 250 m a residence is located closer to a station its price is 2.3% higher than commercial properties. Commuter railway stations have a consistently higher positive impact on the property value compared to light and heavy railway/Metro stations. The inclusion of other accessibility variables (such as highways) in the models reduces the level of reported railway station impact. © 2007 Springer Science+Business Media, LLC

Iranian-Israeli relations in light of the Iranian Revolution

textThis thesis considers the transformation of Iranian-Israeli ties following the 1979 Iranian Revolution from a Western-allied relationship to a covert, scandalous relationship, specifically in the context of the Iran-Iraq War. I also look at the Iranian and Israeli narratives and compare the religious, historical, ideological and psycho-political underpinnings that reveal significant similarities between these two superficially diametrically opposed states, and ultimately shaped the complex and misunderstood relationship between the two countries.Middle Eastern Studie

Land Use Impacts of Rapid Transit: A Review of the Empirical Literature

This paper attempts to consolidate the existing empirical eviden ce on the land use impacts of rail rapid transit. A framework for organizing the literature is developed based on the objects of study, analytical techniques and methodological approaches used. Thirty-seven studies are reviewed co vering transit's impacts on property values, development and vacancy rates, changes in land use types, and population and emplo yment growth. Ten recurring themes in the studies ' fin dings are highligh ted. A ccessibility to transit tends to effect an average residential property value premium of six to seven percent, but o verall land use changes are typically small and require the presence of several complementary factors, such as supportive local land use policies and existing demand for high density development

A generic model for investigation of arching action in reinforced concrete members

A generic nonlinear compound frame model is developed and applied for investigation of arching action in reinforced concrete beams. This model takes account of geometrical and material nonlinearities including cracking and crushing of the concrete and yielding of reinforcing steel. Further, a non-local model is adopted to resolve the numerical sensitivity associated with compressive softening of concrete. The effect of support stiffness is incorporated into the formulation by a set of nodal rotational and translational springs that, respectively, represent the flexural and axial stiffness of the supports. The developed model is verified by available experimental data and advanced continuum-based FE models and it is shown that the generic model can predict the ultimate loading capacity and loaddisplacement response of reinforced concrete beams and one-way slabs with reasonable accuracy. Lastly, a parametric study is undertaken and effects of end supports stiffness and concrete compressive strength on development of arching action is investigated

Introduction to Volume 11

It is often the burden of an introduction to find a unifying thread or theme in the material to follow. In a field such as planning, where academic research spans everything from the role of trees in urban beautification to the effects of globalization on regional economies, the synthesizing task is often unrewarding.At first glance, the potpourri of theories and issues in this year's Journal articles offer no such emergent themes. The scope of the articles ranges from urban politics to social organization to multinational firm location to the relationship of land use and transit. Yet each contribution offers an argument that spatial policies, processes, and structures, however evolving, continue to shape modern society

Influence of concrete compressive strength on the arching behaviour of reinforced concrete beam assemblages

The influence of concrete compressive strength on the loading capacity of purely flexural RC members is minor; however, the beneficial effect of concrete compressive strength on the ultimate loading capacity of axially restrained RC beams can be fairly significant due to development of compressive arch action. Accordingly, in this study, six 2/5th scale restrained RC beam assemblages with various concrete compressive strength (ranging from 18 MPa to 67 MPa) and two different longitudinal steel bar arrangements are tested to establish the relationship between concrete compressive strength and ultimate loading capacity of restrained RC beam assemblages. In addition, nonlinear finite element (FE) model of the tested RC beam assemblages with different boundary conditions were developed and a good correlation between experimental results and FE predictions was observed. With regard to the results captured by the lab tests and nonlinear FE models, it is concluded that the ultimate loading capacity of axially restrained RC beams has an almost linear relationship with compressive strength of concrete and the slope of this line depends on the translational stiffness of end supports (along the beam axis)

Development of the compressive membrane action in partially-restrained reinforced concrete sub-assemblages

Development of compressive membrane (arching) action in longitudinally-restrained reinforced concrete (RC) beams subjected to medium to large displacements can enhance the stiffness, ultimate load capacity and the robustness of the RC frames under unexpected loading scenarios. The enhancement provided by the arching action is not considered in the current design practice and accordingly, the main objective of this paper is to evaluate the development of compressive membrane action in partially-restrained RC beam sub-assemblages. The results of experiments conducted on RC sub-assemblages with different concrete compressive strength (f′c) and reinforcement ratio (P) are briefly discussed and the tested sub-assemblages are analysed using two different types of nonlinear FE models, i.e. 2D continuum-based and 1D frame FE models. The results obtained from the numerical models as well as the experimental data are employed to quantify the enhancing effects of the compressive membrane action with respect to concrete compressive strength and reinforcing bar proportion