Steel building

Résumé

A steel building is a metal structure fabricated with steel for the internal support and for exterior cladding, as opposed to steel framed buildings which generally use other materials for floors, walls, and external envelope. Steel buildings are used for a variety of purposes including storage, work spaces and living accommodation. They are classified into specific types depending on how they are used. History Steel buildings first gained popularity in the early 20th century. Their use became more widespread during World War II and significantly expanded after the war when steel became more available. Steel buildings have been widely accepted, in part due to cost efficiency. The range of application has expanded with improved materials, products and design capabilities with the availability of computer aided design software. Advantages Steel provides several advantages over other building materials, such as wood:

Steel is structurally sound and manufactured

Source officielle

https://en.wikipedia.org/wiki/Steel_building

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This paper proposes a nonmodel-based framework for estimating story-based engineering demand parameters (EDPs) in instrumented steel frame buildings with steel moment-resisting frames (MRFs). The proposed framework utilizes a wavelet-based damage-sensitive feature and basic building geometric information to infer the building damage state at a given seismic intensity. The story-based EDPs are predicted with a reasonable accuracy compared to those predicted from rigorous nonlinear response history analyses that typically require the explicit use of a nonlinear building model. The efficiency of the proposed framework is demonstrated through a number of illustrative examples including actual instrumented steel frame buildings that experienced the 1994 Northridge earthquake in Los Angeles. It is shown that if the building content is known the proposed framework can facilitate building-specific seismic risk and loss assessment within minutes after an earthquake provided that the recorded floor absolute acceleration histories at discrete locations along the height of the building are accessible. The nonmodel-based framework is also extended at the city-scale through the development of generalized earthquake-induced damage and loss maps for the same earthquake event. The same framework can facilitate the decision-making for effective pre-disaster measures for earthquake disaster risk management of building assets.

Elsevier2018

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Experimental investigation of the cyclic properties of welds in mild structural steels

Selimcan Ozden

Structural steels have long been used in construction applications. Their mechanical properties and behavior under seismic loading or under fatigue design are of considerable interest for researchers and engineers. Although extensive studies have been conducted on the cyclic behavior of structural steels, they mostly focus on base material responses. However, base material response can be affected by changes in microstructural properties of steels. In steel construction this situation often arises in welding different components where due to thermal loading certain regions change their crystallographic phases and consequently their mechanical properties. This master's thesis is dedicated to the investigation of the lesser known large amplitude cyclic material behavior of these regions termed Heat Affected Zones (HAZ). The behavior of welded connections is of paramount importance for structural integrity. Their behavior under extreme loading conditions can be the determining factors for the failure of joints and subsequent structural collapse. Field observations following significant earthquake events (e.g. 1994 Northrigde incident) has shown that the assumed ductility of the steel construction can be put into question when poorly executed welded structural joints suffer premature fracture. The head-boomed experience from these suggests that failures often arise from combination of ill-conceived detailing and insufficient weld quality (e.g. large defects on low thoughness). As the understanding of this problem progressed, better detailing properties and quality controls have been proposed to avoid brittle nature of joint failure. In this master’s thesis the author investigates the behavior of S355J2+N structural steel as HAZ of welded material and base material subjected to uniaxial cyclic loading and large inelastic strain demands under seismic loading in the experimental and numerical level. HAZ at welded specimens is obtained through thermal loading in the laboratory environment. Uniaxial cyclic loading tests are performed in the laboratory as well. In addition, comparisons between the base and welded metals for the steel class of S355J2+N are provided as well including material parameters for Voce-Chaboche and Updated Voce-Chaboche models. Results of this study reveal that under cyclic loading welded material hardens more than base material. In addition, plateau region exercised in base material disappears in welded material and welded specimens experience rounding around the yield stress which is not the case for base material. Accuracy of simulation of welded material and correctness of model parameters greatly depend on whether Voce-Chaboche or Updated Voce-Chaboche model is applied to the right material being investigated.

2021

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, ,

Building-specific loss assessment methodologies utilize component fragility curves to compute the expected losses in the aftermath of earthquakes. Such curves are not available for steel columns assuming they remain elastic due to capacity design considerations. Nonetheless, first-story steel columns in moment-resisting frames (MRFs) are expected to experience damage, through flexural yielding and formation of geometric instabilities. This paper utilizes an experimental database that was recently assembled to develop two sets of univariate drift-based column fragility curves that consider the influence of loading history. Ordinal logistic regression is also employed to develop multivariate fragility curves that capture geometric and loading parameters that affect the column performance. The implications of the proposed fragility curves on building-specific loss assessment is demonstrated using a case of an 8-story office building with steel MRFs. It is shown that structural repair costs in this case may increase by 10%, regardless of the seismic intensity, when column damage is considered. Similarly, the contribution of structural component repairs to expected annual losses may double over the building lifespan.

2018

Chargement

Experimental investigation of the cyclic properties of welds in mild structural steels

Selimcan Ozden

2021