Abstract Steel faced sandwich panels with polyurethane foam core PUR are widely used for façade systems, due to their high strength‐to‐weight ratio and very good thermal properties. For ordinary civil engineering applications, their design is generally controlled by stiffness rather than strength, excepting the under pressure (suction) due to wind, where pullover failure of the fasteners may occur. Accordingly, the ductility and energy absorption demands are not generally specified. For extreme loadings, like those generated by blast, they may suffer extensive damage or destruction, with high potential for collateral risk to occupants. The paper addresses the behavior of sandwich panels under extreme out of plane loads, and factors that may enhance their ductility and energy absorption capacity. Numerical models are calibrated against relevant test data and employed in a parametric study. Appropriate end fastening and lateral stiffness at the supports are particularly effective in increasing the ductility and prevent premature failure of the wall panels.

Steel frame structures are widely used in various types of constructions. With much longer experience and tradition in practice, the Moment Resisting Frames (MRF) and Concentrically Braced Frames (CBF) were the predominant lateral load resisting systems for many decades, thanks to their architectural versatility and high ductility (MRF) or high lateral stiffness (CBF), respectively. On the other hand, the much newer Eccentrically Braced Frame EBF system, may be a viable alternative, thanks to an appropriate combination of stiffness and ductility. In this study, we investigated the effect of composite action between the link beam and the concrete slab on the monotonic and cyclic response of EBFs with long links. The results indicated an increase of initial stiffness and yield resistance of the system, but a small impact on the ductility. Also, the simple detachment of the concrete slab from the beam by the lack of shear studs does not fully eliminate the composite action in links, which may affect both the local and global behavior.

External explosions, either accidental or intentional, pose a serious threat to the communities but also a challenge to the structural engineers. Such threats include detonation of high energy explosives (e.g., improvised explosive devices), which can cause structural failures (local damage of structural/nonstructural members or even global failures) and serious injuries or deaths. This risk can be minimized by increasing the standoff distance, but also through structural conception and design, e.g., avoiding brittle materials especially on the facades, adopting specialized construction techniques and detailing. The study investigates the capacity of light steel building facades to resist the effects of close-range explosions and main parameters affecting the ultimate strength and deformation capacity. Pressure-impulse P-I curves are derived from numerical analyses performed with Etabs finite element based structural analysis and design program. Numerical models are calibrated against benchmark tests obtained in a full-scale experimental program.

The building sector continues to play an essential role in reducing worldwide energy consumption. The reduced consumption is accompanied by stricter regulation for the thermotechnical design of the building envelope. The redefined nearly Zero Energy Building levels that will come into force for each member state will pressure designers to rethink the constructive details so that mandatory levels can be reached, without increasing the construction costs over an optimum level but at the same time reducing greenhouse gas emissions. The paper aims to illustrate the main conclusions obtained in assessing the thermo-energy performance of a steel-framed building representing a holistically designed modular laboratory located in a moderate continental temperate climate, characteristic of the south-eastern part of the Pannonian Depression with some sub-Mediterranean influences. An extensive numerical simulation of the main junctions was performed. The thermal performance was established in terms of the main parameters, the adjusted thermal resistances and global thermal insulation coefficient. Further on, the energy consumption for heating was established, and the associated energy rating was in compliance with the Romanian regulations. A parametric study was done to illustrate the energy performance of the investigated case in the five representative climatic zones from Romania. An important conclusion of the research indicates that an emphasis must be placed on the thermotechnical design of Light Steel Framed solutions against increased thermal bridge areas caused by the steel’s high thermal conductivity for all building components to reach nZEB levels. Nevertheless, the results indicate an exemplary behaviour compared to classical solutions, but at the same time, the need for an iterative redesign so that all thermo-energy performance indicators are achieved.

Building constructions are susceptible to significant risks from numerous low probability hazards during their design lifetime. Typical examples include fire, impact, explosion, earthquake, and severe weather hazards (wind, snow). The probable risks also include a special category pertaining to unidentifiable events, such as human errors in design and construction. As such exposures and hazards are difficult to quantify, the consequences can be severe, ranging from injuries or loss of life to serious economic costs. The paper presents the results of investigations conducted in the aftermath of a partial collapse during the construction of an intermediate roof built from hybrid steel-timber trusses in an existing market. The experimental tests and numerical simulations allowed the investigators to reconstruct the chain of events and identify the local damage that triggered the progressive collapse.

The building sector continues to register a significant rise in energy demand and environmental impact, notably in developing countries. A considerable proportion of this energy is required during the operational phase of buildings for interior heating and cooling, leading to a necessity of building performance improvement. A holistic approach in building design and construction represents a step to moderate construction costs in conjunction with reduced long-term operating costs and a low impact on the environment. The present paper presents an experimental evaluation of the energy efficiency of a building under real climate conditions; the building, which represents a holistically designed modular laboratory, is located in a moderate continental temperate climate, characteristic of the south-eastern part of the Pannonian Depression, with some sub-Mediterranean influences. Considerations for the holistic design of the building, including multi-object optimization and integrated design with a high regard for technology and operational life are described. The paper provides a genuine overview of the energy efficiency response of the building during six months of operational use through a monitored energy management system. The energetic analysis presented in the paper represents an intermediary stage as not all the energetic users were installed nor all the energetic suppliers. However, the results showed a reliable thermal response in the behaviour of recycled-PET thermal wadding used as insulation material in the building and for the intermediary stage in which the building has only secondary energy users, the energetic balance proves its efficiency, keeping the buffer stock of energy high values over 90%.

Buildings' structural components are sized for anticipated actions that can occur during their lifetime. However, for unforeseen loading events, like accidental explosions produced at close distance, the forces imparted to the structure can be only approximated. Therefore, the local failure of some members is most likely to occur. Providing alternate load paths can prevent propagation of collapse and preserve the global structural integrity. In case of multi-storey buildings, the contribution of the floor system and beam-floor interaction to the load redistribution capacity can be significant if properly accounted for in design. The study presented in the paper investigates the response of a multi-story steel frame building at the direct effect of a close-in explosion. The main parameters are the degree of interaction and the capacity ratio between steel beams and concrete slab.

The frame structures with eccentrically braced frames (EBF) are used world-wide and is the alternative to the centrically braced frames (CBF). The dissipative elements of eccentrically braced frames are characterised by the forming of plastic hinges, situated at the extremities of frame elements, preferably in the beams. The strength and ductility of EBF is directly related to the strength and ductility of the links The seismic energy is dissipated by means of elasto-plastic bending cycles (for the long link). This paper presents numerical studies with the objective to investigate the behaviour of 2D steel and composite eccentrically braced frames under seismic loading with active links which yield in bending. For a comparative analysis between the behaviour of eccentrically braced frames with steel sections and the ones with composite sections (without connection in dissipative zones), when are subjected to seismic loads a series of nonlinear static analysis - push-over were carried out for both types of structures.

Eccentrically braced frames (EBF) are frequently used for the structures in seismic areas as an alternative to the concentrically braced frames (CBF) and moment resisting frames (MRF). When are designed to dissipate the seismic induced energy, the potential plastic zones (dissipative elements) must have a predictable behaviour. The other structural elements are non-dissipative and must be designed to remain essentially in elastic stage under seismic action. The strength, stiffness, and ductility of EBF is directly related to the configuration of the links. While short links are preferred for their larger stiffness and deformation capacity, long or intermediate links may be also required, especially due to architectural or space usage constraints. This paper presents the result of numerical studies with the objective to investigate and compare the behaviour of steel and composite eccentrically braced frames under seismic loading with different link configurations. Numerical models were calibrated against test data.

The paper is dealing with the problem of a functional conversion (involving both architectural and structural issues) applied to the case of an industrial building. As well known, temporary tents, designed according to the European Code EN13782, represent a remarkable stake on the building market and a fast and practical solution for some situations. It is exactly the case approached by the paper, where the investor has initially decided to erect on his platform a provisional shelter for agricultural machines and subsequent staff, built of a light steel structure covered by PVC roofing and cladding. This temporary tent has been acquired from a specialized supplier in form of a series product. After using the tent for a number of years, the investor has decided to convert the existing structure from architectural and structural point of view by switching to a permanent structure designed accordingly. Important changes were thus imposed both to the architectural part (technological flows, openings, facades) and especially to the structural part where this switch imposed a re-design to the codes of permanent structures (especially as far as climatic loadings are concerned). The required architectural change implied the building of a 70 cm high concrete plinth and replacing the PVC membrane temporary roofing and cladding by permanent 60 mm thick PUR sandwich panels. Together with a new system of openings this has led to renewed facades of the buildings. As for the structural change, the required conversion has imposed a thorough checking of the existing steel structure (very slender and typical to a tent) in view of transforming it into a permanent structure. The consolidation measures of the existing galvanized steel structure are described, together with the measures applied at infrastructure level in order to implement the required conversion.

The period between 1960s and 1970s had a significant impact in Romania on the urban development of major cities. Because the vast expansion of the industry, the urban population has massively increased, due the large number of workers coming from the rural areas. This intense process has led to a shortage of homes on the housing market. In order to rapidly build new homes, standard residential project types were erected using large prefabricated concrete panels. By using repetitive patterns, such buildings were built in a short amount of time through the entire country. Nowadays, these buildings represent 1.8% of the built environment and accommodate more than half of a city's population. Even though these units have reached only half their intended life span, they fail to satisfy present living standards and consume huge amounts of energy for heating, cooling, ventilation and lighting. Due to the fact that these building are based on standardised projects and were built in such a large scale, the creation of a system that brings them to current standards will not only benefit the building but also it will significantly improve the quality of life within. With the transition of the existing power grids to a "smart grid" such units can become micro power plants in future electricity networks thus contributing to micro-generation and energy storage. If one is to consider the EU 20-20-20 commitments, to find ideas for alternative and innovative strategies for further improving these building through locally adapted measures can be seen as one of the most addressed issues of today. This research offers a possible retrofitting scenario of these buildings towards a sustainable future. The building envelope is upgraded using a modular insulation system with integrated solar cells. Renewable energy systems for cooling and ventilation are integrated in order to provide flexibility of the indoor climate. Due to their small floor area, the space within the apartments is redesigned for a more efficient use of space and an improved natural lighting. Active core modules are placed on top of the unused attics and a solar panel array is introduced. Furthermore accessibility issues are addressed by facilitating access for disabled people and implementing an elevator system that currently these building do not have.

Eccentrically braced frame, both steel and composite, are a very useful solution because it combines the ductility of moment-resisting frames (MRF) and the lateral stiffness of concentrically braced frames (CBF). Also, are used due to architectural reason, because in case of centrically braced frame there are fewer solutions (restrictions). In case of eccentrically braced frame, when the beam is designed in a composite solution concrete-steel, the actual seismic provisions [1, 2] require that in the potentially plastic areas of the beam complete disconnection between the concrete slab and the steel beam. However, the lack of the connection between the concrete slab and the steel beam does not lead to behaviour similar to that one of a steel only beam. The concrete slab has an influence on the behaviour of the plastic hinge in this area.

Eccentrically Braced Frames (EBF) are used world-wide and represent the alternative to the Concentrically Braced Frames (CBF) and Moment Resisting Frames (MRF). Eccentrically braced frames are characterized by high lateral rigidity, while the dissipation occurs in link elements, by inelastic distortion. The strength and ductility of EBF is directly related to the strength and ductility of the links, development of plastic hinges is designed to be at the extremities of frame elements, preferably in the beams and only at limit states in columns. The seismic energy is dissipated by means of elasto-plastic shear cycles (for the short link), bending cycles (for the long link) and shear and bending cycles (for the intermediate link).This paper presents the result of numerical studies with the objective to investigate and compare the behaviour of 2D steel and composite eccentrically braced frames under seismic loading with active links which yield in bending.

Multistory steel frames are expected to provide resistance to progressive collapse following local damage or failure caused by extreme loading events. Features like ductility and continuity provide more deformation capacity and redistribution of loads so that the structure can bridge over damaged elements. Special measures should be taken to ensure that the connections can withstand the extreme loading and deformation demands arising from the occurrence of local failure. In addition, two-way frames will enhance the progressive collapse resistance over planar systems as the loading demand on each element reduces.In this study, we investigated the response of two-way steel frame systems under the removal of a central column. Extended end-plate bolted connections were used to join the beams to the columns. First, an experimental test was carried out, and then, a numerical model was validated using the advanced non-linear dynamic analysis software Extreme Loading for Structures. The system was capable of developing large deformations associated with catenary response in the beams without failure of the connections. The beam ultimate rotation is larger than the deformation limit given in the codes. (C) 2016 Elsevier Ltd. All rights reserved.

The frame structures with eccentrically braced frames (EBF) are used world-wide and represent the alternative to the concentrically braced frames (CBF). The dissipative elements of eccentrically braced frames are characterized by the forming of plastic hinges, situated at the extremities of frame elements, preferably in the beams, and only at limit states in columns. The strength and ductility of EBF is directly related to the strength and ductility of the links. The seismic energy is dissipated by means of elasto-plastic shear cycles (for the short link), bending cycles (for the long link) and shear and bending cycles (for the intermediate link). This paper presents numerical studies with the objective to investigate the behaviour of 2D steel and composite eccentrically braced frames under seismic loading with active links which yield in bending.

Resistance to progressive collapse under extreme loading is a measure of the structural robustness, and relies primarily on resistance of key elements, continuity between elements and ductility of elements and their connections. In case some hazards occur simultaneously or consecutively in a very short period of time, e.g. fire after explosion or impact, the capacity of the members and connections can be exceeded and this can initiate the progressive collapse of the structure. The paper presents the results of a research program that focused on the ultimate capacity of connection macro-components under large deformation demands and different loading rates. The specimens were extracted from extended end plate bolted beam-to-column connections with different strength and stiffness ratios to the beams.

In Technical University of Cluj Laboratory, several tests according to ECCS loading procedure were carried out. The tested specimens were composite columns of fully encased type subject to a variable transverse load at one end while keeping a constant value of the axial compression force into them. The complex evolution of the hysteretic cyclic curves representing the transverse force versus the associated displacement up to a pronounced deterioration of the column bases leads to a simplified analytical characterization for the loss of resistance and the reduction of stiffness. The analytical work was made at INSA Rennes, under the coordination of prof. Jean-Marie Aribert. A possible approach to investigate better the column seismic performances is illustrated in the last part going from a basic experimental research to a theoretical interpretation in terms of q factor of inverted pendulum structures (one-storey frame) for which the dissipative zones are located in the composite columns.