Search results

This paper aims to present results from numerical studies on the response of fire exposed composite girders subjected to dominant flexural and shear loading. A finite element-based numerical model was developed to trace the thermal and structural response of composite girders subjected to simultaneous structural loading and fire exposure. This model accounts for various critical parameters including material and geometrical nonlinearities, property degradation at elevated temperatures, shear effects, composite interaction between concrete slab and steel girder, as well as temperature-induced local buckling. To generate test data for validation of the model, three composite girders, each comprising of hot-rolled (standard) steel girder underneath a concrete slab, were tested under simultaneous fire and gravity loading.

The validated model was then applied to investigate the effect of initial geometric imperfections, load level, thickness of slab and stiffness of shear stud on fire response of composite girders.

Results from experimental and numerical analysis indicate that the composite girder subjected to flexural loading experience failure through flexural yielding mode, while the girders under shear loading fail through in shear web buckling mode. Further, results from parametric studies clearly infer that shear limit state can govern the response of fire exposed composite girders under certain loading configuration and fire scenario.

This paper presents results from numerical studies on the response of fire exposed composite girders subjected to dominant flexural and shear loading.

The purpose of this study was to develop a three-dimensional (3D) finite element modeling (FEM) technique using the commercially available program ABAQUS to predict the thermal and structural behavior of composite beams under fire loading.

The model was benchmarked using experimental test data, and it accounts for temperature-dependent material properties, force-slip-temperature relationship for the shear studs and concrete cracking.

It was determined that composite beams can be modeled with this sequentially coupled thermal-structural 3D FEM to predict the displacement versus bottom flange temperature response and associated composite beam failure modes, including compression failure in the concrete slab, runaway deflection because of yielding of the steel beam or fracture of the shear studs.

The Eurocode stress-strain-temperature (σ-ε-T) material model for structural steel and concrete conservatively predict the composite beam deflections at temperatures above 500°C. Models that use the National Institute of Standards and Technology (NIST) stress-strain-temperature (σ-ε-T) material model more closely match the measured deflection response, as compared to the results using the Eurocode model. However, in some cases, the NIST model underestimates the composite beam deflections at temperatures above 500°C.

The purpose of this paper is to report the first of four planned fire experiments on the 9.1 × 6.1 m steel composite floor assembly as part of the two-story steel framed building constructed at the National Fire Research Laboratory.

The fire experiment was aimed to quantify the fire resistance and behavior of full-scale steel–concrete composite floor systems commonly built in the USA. The test floor assembly, designed and constructed for the 2-h fire resistance rating, was tested to failure under a natural gas fueled compartment fire and simultaneously applied mechanical loads.

Although the protected steel beams and girders achieved matching or superior performance compared to the prescribed limits of temperatures and displacements used in standard fire testing, the composite slab developed a central breach approximately at a half of the specified rating period. A minimum area of the shrinkage reinforcement (60 mm²/m) currently permitted in the US construction practice may be insufficient to maintain structural integrity of a full-scale composite floor system under the 2-h standard fire exposure.

This work was the first-of-kind fire experiment conducted in the USA to study the full system-level structural performance of a composite floor system subjected to compartment fire using natural gas as fuel to mimic a standard fire environment.

More and more organizations make parts of their information systems available to their business partners and often face integration and interoperability issues. To counter these problems, web services appeared as a promising technology to bridge the gap between organizations and their partners. While web services generally focus on the implementation of functional concerns (FC) such as ordering of goods, the reservation of flights, etc. also non‐functional concerns (NFC) such as security, reliable messaging, performance, and availability have to be addressed appropriately. The purpose of this paper is to identify web services' requirements.

In this paper the authors provide a survey on works in the area of NFCs in web services. After presenting a common terminology, the most important requirements in that context are presented. Further, the authors assess these works against the requirements.

The evaluation reveals that there is no approach that supports the requirements to a satisfying degree. Based on that, the authors motivate the need for a novel holistic approach to NFCs in web services.

The paper presents an extended version of one of the papers presented at iiWAS2010.

This paper deals with experimental and numerical investigations of the composite behaviour within concrete-filled tubular columns with embedded massive steel core (CFTES columns). As the inner profile provides the main load-bearing capacity, the load introduction and transfer is of particular interest for the structural detailing of CFTES columns. Currently, no specific design regulations are available – neither for room temperature nor fire design. The presented investigations provide a basis for design recommendations and numerical approaches on reliable shear stresses.

Three series of push-out tests at room temperature and high temperatures are analysed in terms of ultimate shear strength, bond strength and shear strength-displacement-curve shape. The test parameters involve the steel core diameter and concrete cover, applying normal strength steel and concrete. Furthermore, a three-dimensional finite element model of the push-out tests is set up in Abaqus. The model implies temperature-dependent contact properties derived from the experimental tests using the cohesive behaviour method.

The test data reveal a distinctive reduction in both ultimate shear and bond strength for high temperatures. For high temperatures, the thermal expansion coefficients dominate the composite behaviour. Using the 3D numerical model and applying a temperature-dependent joint stiffness, maximum shear stress criterion and damage evolution, the observed composite behaviour can be described in a realistic manner.

The presented experimental investigations are unique, both concerning the investigated column type and performing push-out tests at high temperatures. For the first time, a temperature-dependent reduction of capable shear stresses is identified, which is crucial for the design of structural components.

Popularly, metaphysics is considered to be the antonym for physics. Argues that this attitude is a hangover from outdated forms of empiricism and positivism. In the light of cybernetic epistemology, scientific theories are linguistic structures which help to produce predictions of events. These structures are not directly deduced from experience, but guessed and then justified a posteriori. Metaphysics provides a basis for such structures. Proposes the principle that the ultimate reality we find in the physical world is that of action. Modifies Schopenhauer's formula as the world is action and representation, with action taking ontological precedence, and not to the space‐time picture of the world. For a picture is only a picture, a representation which changes from one subject to another, from one theory to another; while action is an irrefutable reality. Thus the concept of action in abstracto is taken and on this basis an attempt is made to interpret the fundamental concepts of knowledge: what are objects, what is objective description of the world, what is space and time?

In recent times, the use of steel sections with web openings has become common as slim floor beams because they offer a reduction in weight of the steelwork, accommodate services within the floor depth and provide the composite action. The composite action in these beams is achieved either through the concrete dowels or through concrete plugs. Though these web openings offer several benefits in slim floor beams, they induce the material discontinuity in the steel web, which may affect their shear capacity and/or thermal behaviour. The purpose of this study is to investigate the thermal behaviour of slim floor beams with web openings in fire.

This research presents findings from experimental and analytical investigations conducted to study the thermal behaviour of slim floor beams with web openings in fire. For this purpose, an experimental investigation was conducted, which shows that the presence of web openings has a major influence on temperature development across the steel section as well as along the span of these beams. The behaviour of the tested slim floor beam is validated using finite element modelling. The validated finite element model is then used to conduct a sensitivity study to analyse the influence of different opening spacings, sizes and shapes on the thermal performance of slim floor beams in fire.

Test results show that the presence of web openings has a major influence on temperature development across the steel section as well as along the span of these beams. Temperatures on the web below the openings are found to be higher as compared to those recorded on the adjacent solid steel web. It is also observed that temperatures on the steel web above the openings are lesser than those on the adjacent solid steel web. Parametric studies conducted using the verified analytical modelling methods show that different opening spacings, sizes and shapes have a variable impact on the thermal behaviour of slim floor beams in fire. Closely spaced and larger opening sizes were found to have a more severe influence on their thermal behaviour in fire as compared to widely spaced and smaller openings. It was also found that the behaviour of these beams is influenced by the shape of the openings with rectangular openings resulting in more severe thermal distributions as compared to circular openings.

The findings from this research study are highly valuable as they contribute to the existing knowledge database. There is a lack of experimental and analytical investigation on performance of slim floor beams with web openings at elevated temperatures. The results and conclusions from this study will help in developing innovative designs for slim floor beams and will help in reducing the fire related risk associated with structures comprising of slim floor beams with web openings.

How can an author verify that his writing says what he means and means what he says? Authoring systems are generally specialized in document content creation and pay little attention to techniques for making communicative intentions more explicit. The new idea defended here is that the authors of technical or educational documents can improve access to, comprehension and reuse of documents, if they can explicitly add the intentions behind their writing process. A model called ‘writing intentions’ based on Speech Act theory, which analyzes and represents the author’s intentions is described here. The intentions are coded as a set of metadata and inserted in the document. SABRE (“Système Auteur Basé sur la REutilisation”, an Authoring System Based on Reuse) is a prototype based on the model of writing intentions. It has been implemented and used by authors of educational documents. Authors can express explicitly and edit their pedagogical and communication intentions. The usefulness of such a system is measured in terms of helping authors and readers find documents more efficiently by querying in terms of authorial intentions. Authors can also benefit from such query system to find existing documents for revisions and recycling.

In order for a software system to better serve the user, it should be able to adjust its behavior according to the changing needs in the environment. Oftentimes, selecting a particular action may depend upon various non‐functional requirements (NFRs) such as safety, cost, and so on. In the past, the many possible alternatives for an adaptation action by and large have not been considered systematically and rationally, keeping various NFRs in mind, hence, resulting in low‐level of confidence that such an action is indeed a best possible one that is really desirable. The purpose of this paper is to present a goal‐oriented approach to select alternative(s) based on a particular contextual event, while considering important NFRs.

The paper proposes a goal‐oriented approach in which various NFRs are treated as softgoals to be satisficed and used in exploring, analyzing and selecting among possible adaptation alternatives, in consideration of the particular contextual event.

Without the goal‐oriented methodology, which offers an ontology enriched with the notion of goals for contextual information and also integrates rules for triggering adaptation, the authors feel, through their scenario study applied to their smart‐phone application, that some critical issues might not have been considered in building a usable, useful system.

The concepts introduced in this paper provide a systematic and rational approach to select adaptation alternative(s), considering NFRs along with detecting a contextual event.

This paper presents a numerical study to predict the in-fire performance of slim floor system, composed of asymmetric steel beam, deep steel decking and in-situ concrete slab. The reliability of the proposed numerical model was verified by comparison with experimental results obtained for 4.2m beam tests. A pilot study was also conducted to examine the effect of the cross sectional modification of the steel section on performance enhancement of the model in fire.