This paper presents an experimental study on two 1:3 scale hybrid reinforced concrete shear walls tested under displacement controlled cyclic loading. Both walls include staggered door openings at each level and represent a three-story prototype wall from a real building. The first wall (CSRCW-31-SO) was detailed with steel profiles embedded at the boundary elements, conventional bar reinforcement in the coupling beams and in the boundary piers, and a wall panel reinforced with dispersed steel fibers. Composite action between the boundary steel profiles and the fiber reinforced panel was provided by Nelson shear studs welded to the profiles. The second wall also incorporated steel profiles at the boundary elements but used conventional reinforcement throughout the entire section including the wall panel, the coupling beams, and the boundary piers. In this case the connection between the boundary profiles and the reinforced concrete was achieved through welded steel plates crossed by vertical rebars. At each displacement increment the test program documented the damage state, crack initiation and widths, lateral deformations, and the strains in the wall components. The wall with a fiber reinforced panel (CSFRCW-32-SO) showed a more ductile response than the conventionally reinforced wall. The fiber reinforcement increased the coupling beam capacity and delayed damage localization, which caused the boundary steel profiles to engage more effectively in resisting lateral demand. In the conventionally reinforced wall, the structural response was governed by the limited capacity of the coupling beams, which failed prematurely and prevented the boundary steel profiles from developing their full strength. Although the short span of the coupling beams contributed to this behavior, it was not the primary cause. These results indicate that combining dispersed steel-fiber reinforcement in the wall panel with profiled boundary elements can improve deformation capacity and enhance seismic resilience.

Shear walls are structural elements often used in case of multi-storey buildings, particularly when these are located in high seismic intensity zones. The main role of shear walls is to provide the lateral stiffness required for the building to withstand horizontal forces generated by an earthquake, as well as to contribute to the global ductility of the structure, allowing for efficient dissipation of seismic energy. The use of these structural elements is often indispensable for meeting the performance requirements imposed by current design codes regarding deformability and structural stability during seismic events. The shear walls can be constructed using different types of materials, the most common being reinforced concrete and structural steel. A modern tendency in the seismic design of structures is the implementation of steel-concrete hybrid walls, which combine reinforced concrete with structural steel in order to take advantage of the benefits offered by both materials: the stiffness of concrete sections and the high strength and deformation capacity of structural steel. The present article aims to present the design considerations of a reinforced concrete structure with eight storeys (B + G + 8S), located in a seismic zone, under two distinct cases: the first involving traditional reinforced concrete structural walls, and the second using steel-concrete hybrid walls. The structure has three bays and three spans, each measuring 5.00 m, with a story height of 3.00 m. The building has a non-accessible flat roof and is intended for office use. The analyzed structure is made of reinforced concrete and is characterized by geometric regularity in both plan and elevation. Moreover, the article presents relevant aspects concerning the seismic performance of steel-concrete hybrid walls, including design considerations, seismic behavior under cyclic loading, and the advantages of using composite walls compared to conventional reinforced concrete walls. This comparative study aims to highlight the structural efficiency of each solution and to provide practical conclusions for the design of buildings in seismic areas.

In alignment with the goals of the Paris Agreement, the EU reinforced its commitment to enhance the energy efficiency of buildings. Under the European Green Deal, the EU aims to achieve a "climate-neutral" building stock by 2050. This means that energy consumption and greenhouse gas emissions associated with buildings should be reduced to zero through energy efficiency measures and renewable energy integration. The main pathways towards an EU decarbonized building stock have been designed under the Energy Performance of Building Directive (EPBD). Although at the EU policy-making level, things are constantly developing and preparing the next steps towards the 2050 decarbonized building sector objective, there is still much ongoing research and debate related to the implementation of energy efficiency measures, particularly in eastern European countries. This study assesses the influence of building shape and wall insulation thickness on the overall heat transfer of a building and its impact on the annual heating demand. Energy efficiency in buildings is crucial for sustainable and cost-effective operatcoffions, and understanding the factors affecting heat losses is essential for optimizing energy consumption. Three distinct buildings with different A/V (Area to Volume) ratios were investigated, each representing varying architectural designs. Additionally, multiple thermal insulation thicknesses were considered for the walls, ranging from conventional to advanced thickness. The results of this study reaffirm that the A/V ratio plays an important role in a building's energy performance. Higher compactness leads to reduced heating demand, which is particularly an energy efficient design measure that has no costs. The A/V ratio should be prioritized during the design phase of a building. Moreover, national building codes and regulations should consider the A/V ratio as a factor in determining compliance with energy efficiency standards.

The paper presents the results of a research program that studies the seismic behaviour and performance of hybrid steel–concrete shear walls with openings coupled with conventional reinforced concrete beams. The experimental specimens are manufactured at a scale of 1:3 to reproduce a three-story wall with door openings and were tested under cyclic loads to simulate the real behaviour under seismic action. This paper presents the experimental behaviour of two hybrid steel-concrete shear walls with centered and staggered openings having the same reinforcement configuration at the edges. The connection of steel profiles was assured by horizontal stiffeners welded along the height of the boundary elements. The performance of both walls was analysed by performing numerical analyses using ATENA 3D numerical software. The theoretical study based on numerical models was performed and calibrated using the experimental behaviour of the tested specimens until failure. The paper concludes that the behaviour of hybrid shear walls with staggered openings is governed by the capacity of the coupling beams, which could substantially decrease the deformation and dissipation capacity of such elements. The degree of coupling plays the main role into a correct design of hybrid walls if a high dissipation energy is expected by using the yielding capacity of steel profiles. Further investigations are needed to optimise the solutions and design replaceable coupling beams.

Abstract Present paper presents a comparative study made on the seismic performance of composite steel-concrete shear walls with rectangular openings, by performing numerical analyses using ATENA 3D software. Two specimens were designed at a reduced scale 1:3 having similar arrangements in the cross-section and the same geometry. First element was conceived with centered openings while the second one was designed with staggered openings. Steel connectors disposed as horizontal stiffeners were used to design and to assure the full connection between the structural steel profiles embedded in the edges and the concrete core. The openings that were considered on each story of the walls, were having the dimension of a common architectural door. A part of the results recorded from the experimental tests were used to calibrate the numerical models. This study aims to establish the seismic performance and to investigate the influence of the openings and the geometric position on the overall seismic behavior of the composite shear walls. Key parameters which describe the seismic performance of structural elements such: bearing capacity, deformation capacity, stiffness degradation, cracks and strain development are compared between the specimens and discussed. The results showed that different arrangements of the openings could significantly modify or increase the seismic performance of the composite structural walls.

The obligation of the nZEB building standard has become a certainty of almost two years for all new buildings in Romania. This is even more relevant in the current context of the energy price crisis, as more and more building owners become aware of the importance of energy efficiency and the use of renewable energy systems. Thus, in this paper possible solutions for converting an existing single-family building into a nearly zero-energy building are analyzed and presented. The building has been designed and executed in such a way as to have an energy performance above the minimum required according to the technical regulations in force at the time of design. The current energy performance of the building has been evaluated both theoretically using a dedicated calculation program and based on energy bills for one year period. Based on the current energy performance, a series of solutions have been proposed to increase the energy performance up to the nZEB level. Analyses in terms of energy consumption and life-cycle cost were performed to identify the cost optimal solution that leads to the nZEB upgrade.

The present paper presents the results of a theoretical and experimental program developed to study the seismic performance of precast reinforced concrete wall panels, strengthened with composite materials. These type of elements, also known nowadays as lightly reinforced shear walls with medium ductility (DCM), were widely used between 1955 and 1990 in different European countries (Serbia, Bulgaria, Polonia, Romania etc) being designed at that time without using the principle of shear force associated to the bending resisting moment. The current results refer to the investigation made on five specimens, one “as-built” solid wall, two walls with initial opening and two walls with cut-out opening. Usually, the cut-out procedure is applied cutting the concrete and reinforcements in order to create a new opening or enlarging an existing one. This intervention is widely requested by owners of apartments when they reconfigure the architecture of flats, but this procedure could influence the seismic behaviour by weakening the initial performance of the wall, especially due to the reduction of stiffness. In order to investigate the specimens’ seismic behaviour, in-plane reversed cyclic lateral loadings were applied together with axial vertical loads. The specimens were monitored through the experimental tests using strain gauges, pressure and displacement transducers. Based on the experimental investigations performed on the reference undamaged walls, the specimens were repaired, then after were strengthened with the aim to reestablish the initial capacity of the elements without an important influence to the stiffness. The strengthening strategy proposed had used externally bonded FRP composite reinforcement (EBR-CFRP) and near-surface mounted FRP composite reinforcement (NSM-CFRP). The strengthened elements were tested again to study the behaviour of elements and the effectiveness of the proposed solutions. A numerical analysis was performed in order to check on the accuracy of using simple numerical models to predict the behaviour of strengthened shear walls.

The lateral resisting system comprised of hybrid shear walls is often met nowadays for high rise buildings, to reduce the lateral displacements of the building during a seismic event and to limit the damages of non-structural elements. In fact, “hybrid shear walls” term will replace the old terminology used for composite steel concrete shear walls. This structural system develops a very stable seismic behavior under cyclic lateral loads, but the seismic performance of the system could be significantly changed by the openings required for architectural or functional reasons. This paper presents in detail the seismic behavior of a composite steel-concrete shear wall designed with centered openings and partially embedded steel profiles in the edges. The composite wall was subjected to vertical and horizontal loads and tested to full failure using a cyclic loading testing procedure that simulated the action of an earthquake, aiming to record the seismic performance of the wall in terms of bearing capacity, deformation capacity, failure mode and stiffness degradation. The low-dissipative behavior recorded experimentally of the tested specimen was afterward validated and assessed in detail by performing numerical analyses using ATENA 3D Engineering software. The numerical results were extended to investigate furthermore other structural solutions to increase the bearing capacity and the seismic performance of the wall. It was found that a significant increase in deformation capacity could be obtained if the wall coupling beams are reinforced by diagonal steel bars or additional steel plates.

The structural system composed by composite steel-concrete shear walls (CSW) represents one of the recommended solutions for resisting structures placed in seismic areas. The system is able to provide high strength and limited displacements that successfully fulfil the requirements of earthquake resisting structures. The CSCSW are made of one reinforced concrete web panel which has embedded on the edges different types of steel profiles, with the purpose to improve the behaviour of the conventional reinforced concrete structural walls and to solve some technological issues on the boundary regions, such as reinforcement congestion. In practice, the CSCSW, either exterior or interior, need centred or staggered openings along the height of the structure, due to architectural or functional requirements. In the last decade the solution of solid composite walls without openings was investigated but there is a lack of information about the behaviour of such CSCSW with openings. This paper presents the experimental results on the behaviour of composite steel-concrete coupled shear walls with central openings. The specimens have partially embedded steel profiles on the edges and conventionally reinforced couplingbeams. The influence of different composite connections and the performance of the reinforced concrete with steel fibres in the overall seismic behaviour were studied. The failure modes, strength, stiffness and cracking analysis of the tested specimens are discussed herein. From the experimental tests, it was found that the ductility of the walls could significantly be improved if the traditionally reinforced concrete material is replaced by fibre reinforced concrete using hooked steel fibres.

In the construction industry, sustainability is evaluated, not only in terms of harmful emissions generated during the operation phase, but also in terms of the embodied emissions belonging to building materials and technical equipment. As a consequence, the implementation of highly efficient building materials has become crucial. The objective of this study is to investigate an insulation system based on parallel air chambers embodied in rockwool panels, and to correlate the implications of its implementation compared to an existing insulation system. The analysis was conducted on the first administrative/public building completed in Romania, according to passive house standards. The study begins with experimental investigations of insulation systems under laboratory conditions. Thus, the influence of air layers on the thermal properties of existing rockwool panels was assessed. On the basis of the experimental results, the theoretical energy demand of the high school building and life cycle analysis are determined using simulation software for both insulation solutions: existing insulation composed of solid rockwool panels, and rockwool panels with embedded air layers. The thickness of the insulating air layers is optimized, and with the help of Rayleigh–Bénard equations for each of the five climate zones that were further determined. Taken together, it is expected to achieve a better insulation system by maintaining constant embedded emissions. In conclusion, assuming a 50-year life cycle for the high school building, the insulation system composed of rockwool with embedded air layers brings about a reduction in the total energy consumption of approximately 9.82%, compared to the case of a standard insulation system based on solid rockwool panels without additional air layers.

The research focused on the solutions to create performant elements for seismic resisting structures has increased in the last decade. Different hybrid solutions that have composite steel-concrete structural shear walls with steel encased profiles (CSRCW) were studied. The benefits of this structural system include high performance characteristics in terms of ultimate loads, deformations capacity and ductility. The paper presents a comparative study on the behaviour of CSRCW, both solid and with centred openings. The study is based on the theoretical and experimental results obtained on steel-concrete composite elements 1:3 scale, tested in laboratory under cyclic lateral loads. All specimens were tested under constant vertical load and cyclically increasing horizontal (lateral) loads. The tests were performed until failure. The comparative study is focused on the main parameters: maximum load bearing capacity, stress and strain distribution in structural components, cracking patterns, deformation and degradation capacity. The conclusions indicate that the composite solution of steel concrete shear walls, lately addressed also as "hybrid", with or without openings, could offer enhanced load bearing capacity, energy absorption and relatively gradual stiffness degradation.

The construction industry is responsible for 36% of the European Union's greenhouse gas emissions. The main goal of the EU in the last decade has been to boost energy efficiency and expand the use of renewable energy in buildings. Ground-to-air heat exchangers may be a solution to reduce the use of primary energy in buildings from nonrenewable sources. The study in this paper deals with an evaluation of the heating and cooling energy potential of a ground-to-air heat exchanger (GAHE), serving a pilot energy-efficient building in Romania. The research follows a comparison between the experimental behavior of GAHE, evaluated based on measured outlet temperatures for two full years, and theoretical behavior, assessed using two computational models following EN 15241:2007 (Model 1) and EN 16798-5-1:2016 (Model 2). A comparison is made between the energy potential calculated using temperature measurements and the energy potential determined based on calculated outlet temperatures using the two models. The assessment is performed as well for conventional climate corresponding to the building location.

The evaluation of environmental aspects in the early planning phase of buildings supports the reduction of resource use and environmental impacts associated with the construction sector over the whole life-cycle of the building. In this chapter, the current calculation methodology is assessed and critically reviewed with regard to the usability option for the introduction of an automated and time efficient LCA benchmark. In order to derive a new set of benchmarks regarding the LCA, this chapter shall submit as potential data input, as it contains the conclusions of several LCA for non-residential building located in different parts of the world.

Implementation of energy efficiency and renewable energy in the construction industry has become a main strategy towards a sustainable built environment. One of the pillars of sustainable development, besides the environmental and social aspects, is the economic efficiency. Therefore, economic efficiency throughout the life cycle should be addressed as well when designing highly energy efficient buildings. Buildings are long term investments, which assume that the initial decision on the quality of the investment has long term consequences. The purpose of this chapter is to present the method of life cycle cost (LCC) analysis from the various perspectives existing in the literature and standards. LCC of evaluation is extremely important towards the promotion of energy efficiency measures in front of investors, building owners and authorities. Therefore, it is necessary for architects and engineers to have the basics for applying the LCC analysis and to include it in the design phase of a building.

Reinforced concrete shear walls are the most effective structural elements used to increase the overall lateral stiffness and deformation capacity of multi‐storey buildings structures. Due to the functional or architectural requirements, structural walls with multiple openings have to be frequently designed. This fact, impose to assure higher sectional strength of the structural elements, which have reduced the cross‐sections due to openings. Composite steel‐concrete shear walls, with steel embedded profiles, could represent alternative structural solutions to increase overall performances of such walls. This paper presents an experimental study made on three composite steel‐concrete shear walls with central openings and partially embedded steel profiles. The experimental specimens were built to 1:3 reduced scale and present different cross‐sectional arrangements. The walls were subjected to quasi‐static reversed lateral and vertical loads with the aim to analyse the nonlinear behaviour of elements. The behaviour of elements was monitored in terms of crack distribution to identify the failure stages, maximum load and lateral displacements. From the tested elements, the specimen which had hooked steel fibres embedded in the concrete attained the highest ductility, proving that the fibres contribute at the dissipation of energy from earthquakes.

The present paper presents the results of an experimental program developed to study the seismic performance of precast reinforced concrete wall panels. The specimens' characteristics and the reinforcement configuration were taken from a typical Romanian project used widely since 1981. The elements were designed at that time without using the principle of shear force associated to the bending resisting moment so they can be therefore considered as large, lightly reinforced walls of medium ductility (DCM). The used specimens were of three situation kinds, namely: as-built blank solid wall, with initial opening and with cut-out opening. The experimental test set-up and the loading strategy were designed to simulate the shear behaviour. Based on the experimental investigations performed on precast RC wall panels, subjected to in-plane reversed cyclic lateral loads, the authors identified the following: the behaviour mode, the critical regions, the maximum lateral load and the displacement capacity at ultimate stage, the cut-out opening influence on the wall's seismic performance and the accuracy of theoretical estimations.

Waste incineration air pollution control (APC) residues require pretreatment before landfilling because these types of residues encompass pollutants from an incineration gas stream. The environmental concerns of APC residues consist of a risk of leaching and subsequent release of potentially harmful substances that occur under environmental exposure. The stabilization/solidification (S/S) method of incineration residues is one of the most applied technologies for hazardous incineration residues. Portland cement is commonly used as a binder material in S/S for pollutant encapsulation, in order to change the hydrological characteristics of the landfilled material. Based on previous research, an innovative S/S method for APC residues is investigated, meant to replace Portland cement with cement-like material made from lignite fly ash (FA). To do this, a lab-scale landfill was created through the promoted S/S method and exposed to the environment for 12 months. Thus, this article assesses the lab-scale leaching behavior of a landfill disposal material exposed to environmental conditions and attempts to prove the promoted innovative S/S method. The results show that the replacement of Portland cement with a substitute material for utilization in the S/S method can mitigate energy consumption in the industrial cement subsector.

This paper presents the results of an experimental study performed on concrete structural walls subjected to vertical and cyclic lateral loads. The purpose of the study is to experimentally investigate the seismic behavior and performance of composite steel-concrete coupled walls with regular openings and conventional reinforced coupling beams. The paper also addresses the manner in which the use of steel fibers reinforced concrete and various composite steel-concrete connections influence the hysteretic performance of the walls. Four of the total five experimental specimens had centrally aligned openings, while the fifth one was designed as a solid wall and served as reference. The experimental specimens present various cross-sectional arrangements, thus the testing matrix comprises of a total of three composite steel-concrete walls with central openings (CSRCW) with steel profiles partially embedded on the edges, one conventional reinforced concrete wall (RCW) with central openings and the solid specimen, which is also a composite steel-concrete wall. Based on the experimental results, it was observed that by embedding supplementary steel fibers in the concrete matrix, the ductility loss due to openings could be regained and significantly improved. The composite connection between structural steel and concrete web panel of the walls could successfully resist until the specimens reached the ultimate failure. The paper therefore concludes on the performance of various structural solutions and details by highlighting strengths and weaknesses of the systems.

Following the 21st Conference of the Parties (COP 21), the 2015 Paris Agreement on Climae Change strengthens the attempts of the European Union to decarbonize the building sector and to facilitate the transition from fossil fuels towards cleaner energy. The last version of the Energy Performance of Buildings Directive 2018/844/EU is human centric and requires the integration of indoor environmental quality assessment, simultaneously with energy performance and cost-optimal requirements. In other words, efforts to improve the energy efficiency of buildings must actively contribute on reducing the building stock's climate impact while ensuring healthy indoor climate conditions, wellbeing and productivity. This paper introduces the cost-optimal analysis and indoor environmental quality assessment for nearly zero-energy buildings in temperate climate. The study presents several nearly zero-energy buildings (NZEB) scenarios for residential buildings, which include measures that are either upgrades that can be implemented in the as-built case study building or different other configurations of thermal envelope, technical systems and on-site renewable energy production. The cost-optimal analysis results show that among the investigated scenarios, the lowest global cost is achieved by the as-built house, which is an all electric building that has passive house envelope, mechanical ventilation with heat recovery, heat pump and solar collector. Furthermore, the study reveals that with the implementation of PV panels, the primary energy demand can be reduced with 55% at a global cost increase of only 3%. The results and data can be used to compare energy efficincy measures and the related costs between EU Member States.

Abstract The paper presents the results of experimental investigations and numerical analyses performed on reinforced concrete flat slabs. Two tests were carried out on two flat slab specimens designed without specific shear reinforcement. The present paper deals only with the experimental behaviour and numerical modelling of such slabs, this representing the initial part of a larger study which aims to evaluate the shear capacity of such deficient slabs resulted from faulty design or execution and to identify viable and efficient strengthening solutions. ATENA finite element software package was used to numerically model the behaviour of the specimens. A very good agreement was achieved between the results of experimental investigations and numerical modelling with deviations of 0.2% in terms of maximum load carrying capacity and of 7% in terms of corresponding displacement. The specimens were able to carry loads of more than 950kN, larger than those evaluated using designated Eurocodes, displaying a safety factor of 2.72.