Existing Building Stock Research Articles

Performance Prediction of Anchors in SFRC using Minimally Invasive and Non‐Destructive Techniques

AbstractFastenings are crucial for the upgrade of existing structures, by either enhancing structural components or modernising and expanding structures and structural systems. Whilst concrete is prevailing in the existing building stock, new types of concrete composites are increasingly used to improve the sustainability and overall structural performance of built assets. The addition of short dispersed fibres is a material technology with several applications. This paper addresses the synergy of fastening elements, introducing localised loads in concrete substrates, and of fibres, particularly in terms of the fibre orientation and density in the load application area, which is a significant quality aspect. The possibility to forecast this synergy based on non‐destructive or minimally invasive testing methods is an efficient tool to increase confidence in the design load‐bearing performance of the anchorages. Initially, previous literature and own investigations on such techniques are presented. Furthermore, a methodology is presented on associating such information to predict a single anchor's resistance on the basis of sophisticated non‐linear analyses and testing with engineered fibres alignments.

Shape Memory Alloy‐Based Seismic Retrofit of an existing URM Building

AbstractMasonry buildings constitute a considerable part of the existing building stock and are often related to significant architectural and cultural value. Empirical construction, accumulated damage, material heterogeneity and anisotropic behavior deteriorate their structural and seismic capacity, increasing thus the risk of undergoing severe damage and even collapse. To enhance these buildings' performance, various retrofit schemes have been developed and have been included in current codes and standards, mostly utilizing conventional materials and improvement of their intervention techniques. Recently, research efforts are oriented to the application of emerging metal materials with advanced properties endowed with re‐centering abilities that conventional materials lack, aiming to achieve vibration control and mitigate potential structural damage.This work investigates the use of shape memory alloys (SMAs) for the seismic protection of masonry buildings focusing on the exploitation of their superelastic effect, namely the ability to revert to their original shape after being subjected to large deformations. The research adopts a case study approach, developing an SMA based retrofit scheme to be applied to an existing listed unreinforced masonry building in Thessaloniki. For the purposes of the study, finite element modeling is performed, while response spectrum analysis is carried out to assess the effectiveness of the introduced retrofit strategy.

Energy-Efficient Solutions: A Multi-Criteria Decision Aid Tool to Achieve the Targets of the European EPDB Directive

The building and construction sector has a significant impact on the CO2 emissions and pollutants released into the atmosphere, which contribute to climate change. The EPDB Directive mandates the achievement of minimum energy class E for all residential buildings by 2030 and energy class D by 2033. Particularly, in Italy, about 86% of the existing building stock predates the enactment of any energy laws or regulations, making it imperative to apply the energy efficiency interventions. This paper provides a support decision tool for the identification of the standardized interventions in the building envelope, the air conditioning system, and domestic hot water production. This study is focused on a specific construction period class (1976–1990) in six different climatic zones. The methodological approach is based on a cataloguing phase and the definition of ante operam energy classes as well as on case study identification, energy requalification intervention identification, solution simulations, and cost estimation. By simulating the standardized interventions for each climatic zone, a range of possible combinations is identified. The most advantageous ones are determined based on a cost–benefit analysis considering the potential class jump achieved. The research result is a matrix of energy efficiency interventions that is applicable to each climatic zone and can be extended to the existing housing stock.

Development of recommendations for the implementation of seismic risk mitigation policy in the Russian Federation based on world experience

The current state of practice of seismic risk mitigation policy in the following countries is analyzed: Japan, USA, China, Italy and the Russian Federation. In particular, the paper compares seismic retrofit policies for existing buildings and financing mechanisms for comprehensive seismic risk mitigation in the context of each country's regulatory framework. The analysis of the current seismic risk mitigation policy in the Russian Federation leads to the conclusion that it needs serious modernization and reorganization, including: 1) development of a new generation of standards specifying nonlinear analysis methods and 2) development of effective financing mechanisms for the seismic evaluation and seismic modernization of the existing building stock. 
 The aim of this paper is to identify best practices in seismic retrofitting policy that may be useful for the implementation and adjustment of seismic risk mitigation policies in the Russian Federation at the federal and regional levels. 
 The result of the paper is a set of recommendations based on the most effective seismic risk mitigation policy instruments, grouped according to the key stages of the seismic amplification process:
 – risk assessment of existing buildings;
 – knowledge transfer; 
 – setting targets for the seismic modernization; 
 – implementation of the seismic strengthening policy;
 – policy implementation monitoring.

Experiences from seasonal Arctic solar photovoltaics (PV) generation- An empirical data analysis from a research infrastructure in Northern Finland

The European Union's highly anticipated “solar strategy” to equip the new and existing building stocks with solar PV panels displays a promising trend in the solar PV industry. However, from Finland's perspective, generating solar PV energy in an Arctic setting is characterised by a few common ambiguities, further lowering the motivation. There are several methodologies for identifying and bridging the gaps to provide accurate conclusions. This article employs the observational and empirical approach in presenting the solar PV energy generation data from the research infrastructure in Oulu, a North Finland city. Empirical evidence from a solar PV system from an Arctic background with a macro to micro-level analysis and documentation is expected to bridge the gap between uncertainties and reality and improve the understanding of the region's seasonal, monthly and annual solar PV generation. Spring was the best period for generating solar PV energy, and autumn was the least favourable for generating solar PV energy in the Arctic. Rooftop inclined solar PV have a better potential during spring and summer, and vertical PV quantitatively generate more energy in autumn and winter. Lower tilt angles proved optimal, as these angles eminently capture the spring and summer irradiation.

Decision-making approaches for optimal seismic/energy integrated retrofitting of existing buildings

Given the ambitious targets of carbon emission reduction set for the very near future, it is now expected that retrofitting operations on existing buildings aim both at reducing their operational energy consumption and at improving their seismic performance. Indeed, it is now well acknowledged that, if a sole energy efficiency upgrade is provided to a given building, in case of an earthquake occurrence, double economic and environmental losses will be experienced due to both the lost investment for energy retrofitting and the repair and retrofitting activities for post-earthquake damage. Moreover, social losses may also be experienced in terms of casualties, injured or homeless due to the seismic and structural deficiencies of the existing structure. To aid thus the process of a coupled seismic/energy renovation of the existing building stock, several multi-criteria decision-making (MCDM) approaches have been developed for the identification of optimal retrofitting solutions for buildings. Such procedures typically consider a range of economic, social, technical, and, more recently, environmental aspects that are assumed to be of interest to decision makers (e.g., installation cost, duration of works, architectural impact, need for specialised workers, etc.). The present study demonstrates the application to a case-study school building of two different MCDM approaches, which account for seismic vulnerability and energy efficiency, as well as related environmental impacts of buildings. The main differences between the two procedures are explored in terms of considered decision-making parameters and corresponding weights, rankings of retrofitting options and identification of the optimal retrofitting strategies.

Performance criteria expressed by means of relative displacements for a retrofitted masonry school building

In order to study how retrofitting techniques applied to URM structures influence the failure modes and the displacement capacity of the buildings, a school building from Bucharest was modelled using 3DMacro software. The mixed structural system required a particular approach for the calculation model, in a software able to capture the interaction between the reinforced concrete elements (columns and tie beams) and the URM masonry panels.Damage pattern evolution was analyzed for the three models capturing the gradual seismic improvements done in the past century, transforming the unreinforced masonry structure into a confined masonry one, with few RC elements, and eventually into a fully jacketed structure with densely spaced RC columns. The results obtained from the nonlinear static analyses were validated by means of global and local displacement limits associated with specific damage criteria.The damage suffered after 1977 Vrancea earthquake and the current performance requirements in terms of seismic safety led to structural changes aimed at improving the behavior of masonry structures by means of interventions that marked the transition from an unreinforced masonry structural system to a retrofitted masonry structural system. The comparative analyses carried out between the behavior of the initial and the strengthened structure of the school intend to highlight the benefits of the retrofitting interventions performed, but also the situations in which the applied strengthening measures might prove to be excessive. Considering the case study is representative for the existing building stock in the education sector in Romania which needed subsequent seismic retrofitting in order to reach the required seismic safety, the results highlight the improved behavior after these interventions. The present works represent a topic of interest at national level, since it targets a large part of the existing building stock subjected to losses in case of an earthquake. Moreover, the past retrofitting interventions assessed in this paper represent a typical intervention done for similar structures, and therefore, the results obtained are representative for the Romanian building stock.

Fragility curves for different intensity measures for a gravity load-designed RC hospital building: A case study

An awareness of the vulnerability of strategic facilities such as hospital buildings is essential to manage post-earthquake events in seismic areas and to plan the allocation of funds for ensuring not only their capacity versus collapse, but also their functionality immediately after seismic events.Fragility functions represent an important scientific approach in the vulnerability assessment procedures for existing building stocks, and the consequent mitigation of seismic risk. It is worth noting that most of the literature on Fragility Curves (FCs) refers to building stocks, but to analyse a considerable number of structures it is often necessary to use simplified building models. The rare discovery in the technical offices of the hospital of very detailed as-built drawingshas allowed for modelling as much as possible adherent to the actual building. The purpose of this work is to provide multiple sets of FCs for a complex reinforced concrete hospital building designed only for gravity loads. These sets can represent a useful tool for the validation of similar structures, which cannot always be traced back to simplified cases. Furthermore, FCs are evaluated for five different Intensity Measures (IMs) to determine the best choice for this parameter. Peak Ground Acceleration, Spectral Acceleration corresponding to the fundamental period of a structure (both intact and damaged), Housner Intensity, and the Geometric Mean of the Spectral Acceleration between 0.2T1 and 3T1 are chosen as different IMs.Incremental Dynamic Analyses are performed on a three-dimensional model to evaluate the FCs for four damage levels. The results are then compared, showing that four out of five intensity indices give consistent results.

Assessment of Subsidization Strategies for Multi-Objective Optimization of Energy Efficiency Measures for Building Renovation at District Scale

In recent years, public authorities around the world have used incentive strategies to encourage the renovation of the existing building stock to meet the set carbon neutrality targets. However, the design of the incentives typically does not consider that the subsidized energy efficiency measures should result in robust long-term improvements with respect to various objectives. Moreover, building energy retrofit analyses are commonly conducted at the individual building level rather than at urban scale, which could instead significantly accelerate the renovation rate. In this context, the current research aims to combine these different factors to support the design of building energy retrofit programs. We developed 21 subsidization strategies and their impact was evaluated on a parametric multi-objective optimization with respect to energy, economic, and environmental performance for a district located in Bolzano, Northern Italy. The optimization was performed considering a set of energy efficiency measures, pertaining to building envelope, climate change, economic scenarios, and two types of energy supplies. The results showed that (1) the impact of climate change is limited for the climate of Bolzano; (2) the type of energy supply strongly influences the economic feasibility of the retrofit investments; (3) when the investment is profitable, the optimal solutions include those measures with the largest impact on energy efficiency; and (4) subsidization strategies modify the number and composition of the Pareto solutions.

From Building Information Model to Digital Twin: A Framework for Building Thermal Comfort Monitoring, Visualizing, and Assessment

The existing building stock is globally responsible for 17.5% of greenhouse gas emissions due to their operation to achieve occupant satisfaction, thus requiring a vast intervention. However, reducing building stock emissions and optimizing building energy performance cannot be considered independently by the users’ well-being. The thermal comfort conditions and their monitoring represent a central issue that could optimize building energy usage while achieving good indoor environmental conditions. This document describes the first findings of ongoing research focused on the development of a building monitoring system, based on the integration of Building Information Modeling tools and sensor technology through Dynamo Visual Programming. Starting from the development of an Asset Information Model, which represents the virtual replica of a building that currently hosts the administrative offices of the municipality of Cagliari, the first step presented in this contribution shows a thermal comfort monitoring system, scalable and modular, that allows effective gathering and elaboration of data about comfort levels in each of the building’s rooms. The system proves to be a helpful support for facility managers to control building thermal comfort conditions and HVAC systems to assure their best operative status or plan suitable interventions to achieve it.

Experimental study of bond behavior on sprayed and poured mortar–brick interface with latex bonding agent under conventional and humid environments

Sprayed mortars are able to enhance masonry walls, particularly for improving the resistance of the existing building stock to horizontal forces such as seismic. This is the case of numerous neighborhoods around the world constructed using load-bearing masonry walls before the 1950s. These mortars are sprayed on site and, to strengthen the interface, for example, latex interface bonding agents are applied between the sprayed mortar and masonry walls. Latex, being sensitive to ambient humidity, undergoes changes in its mechanical properties that directly impact the entire structure of the enhanced wall. But this crucial influence of ambient humidity on the latex layer has often been scarcely analyzed in previous studies. To overcome this gap, this research paper conducts an experimental investigation on the interfacial behavior under different humidity curing environments. It also compares interfaces formed through pouring and spraying methods. Several samples with latex interfacial bonding agents were tested using direct tension and direct shear tests to obtain stress–strain curves. Bond strength, fracture energy, and stiffness were determined using the traction separation method (TSL). This experiments found out that ambient humidity conditions significantly affected interfacial properties. In most cases, conventional curing environments resulted in higher peak stresses and fracture energies compared to humid conditions. Overall, sprayed mortar samples exhibited better interfacial properties than poured ones. Sprayed mortar samples demonstrated higher overall stiffness. The experimental results were fitted using three TSL models, with Schneider’s model providing the most accurate representation of interfacial behavior after optimization.

An archetype-based automated procedure to derive global-local seismic fragility of masonry building aggregates: META-FORMA-XL

The paper presents an automated procedure for deriving fragility curves for typological masonry aggregates, named META-FORMA-XL (MEchanical-Typological Approach FOR Masonry Aggregates – X Local). The topic deals with the urban-scale seismic vulnerability analysis, which can provide powerful information for developing risk mitigation plans and implementing strategies for reducing expected losses. However, when masonry buildings in aggregate are analysed, many issues arise, related to the lack of data, the complexity of the structural configurations and the presence of uncertainties. To this scope, the proposed procedure aims to investigate the seismic behaviour of masonry aggregates, based on numerical analyses carried out on ideal representations of the existing building stock, indicated as archetypes, by modelling geometrical and mechanical uncertainties characterizing buildings in the studied area. The archetype buildings are made according to exposure analyses by combining typical inventory collection forms and information derived from freely available databases. By investigating the seismic response of numerical models for a high number of archetype buildings, fragility curves are derived for all limit-states and two main directions, accounting for global and local damage mechanisms. The procedure is tested on low-rise row masonry aggregates in Southern Italy. The output of the procedure is validated on a real case study, for which a near-full information on the geometrical and mechanical features is available, providing a critical comparison in terms of fragility curves. Results highlight several advantages of the proposed approach, such as the possibility of identifying the most likely collapse mechanism for a specific masonry aggregation, the simplicity and the celerity of the analyses despite the large number of archetype models, and the exhaustive consideration of the uncertainties. Finally, the proposed concept can be readily extended to other aggregation forms and structural typologies.

Assessment of building retrofit scenarios using embodied energy and life cycle impact assessment

PurposeCrucial transition of the Indian residential building sector into a low-emission economy require an in-depth understanding of the potentials for retrofitting the existing building stock. There are, however, limited studies that have recognised the interdependencies and trade-offs in the embodied energy and life cycle impact assessment of retrofit interventions. This research appraises the life cycle assessment and embodied energy output of a residential building in India to assess the environmental implications of selected retrofit scenarios.Design/methodology/approachThis study utilises a single case study building project in South India to assess the effectiveness and impact of three retrofit scenarios based on life cycle assessment (LCA) and embodied energy (EE) estimates. The LCA was conducted using SimaPro version 9.3 and with background data from Ecoinvent database version 3.81. The EE estimates were calculated using material coefficients from relevant databases in the published literature. Monte Carlo Simulation is then used to allow for uncertainties in the estimates for the scenarios.FindingsThe three key findings that materialized from the study are as follows: (1) the retrofitting of Indian residential buildings could achieve up to 20% reduction in the life cycle energy emissions, (2) the modification of the building envelope and upgrading of the building service systems could suffice in providing optimum operational energy savings, if the electricity from the grid is sourced from renewable plants, and (3) the production of LEDs and other building services systems has the highest environmental impacts across a suite of LCA indicators.Originality/valueThe retrofitting of residential buildings in India will lead to better and improved opportunities to meet the commitments in the Paris Climate Change Agreement and will lead to enhanced savings for building owners.

Improving the Energy Performance and Economic Benefits of Aged Residential Buildings by Retrofitting in Hot–Humid Regions of China

The existing building stock faces the challenge of low energy efficiency and requires renovation and upgrading to meet society′s goals of carbon reduction and sustainable development. This study presents an optimization framework utilizing genetic algorithms to develop robust retrofit plans that balance the need for improved energy efficiency, cost-effectiveness considerations for householders, and uncertainties regarding climate conditions. A case study of an aged residential building in a hot and humid region of China is used to demonstrate the proposed method. The optimization results show a potential energy demand reduction of 81.5%. However, due to the relatively long time required to realize economic benefits from high investments, short-term optimization tends to favor solutions with high energy demand and low primary costs. To effectively reduce carbon emissions, it is recommended to consider the long-term economic benefits of retrofits and prioritize solutions with high energy efficiency. However, it is important to acknowledge that the expensive nature of retrofit investments may pose barriers to residents. Society should provide adequate support and guidance to facilitate residential renovation efforts.

A Hybrid Artificial Neural Network—Particle Swarm Optimization Algorithm Model for the Determination of Target Displacements in Mid-Rise Regular Reinforced-Concrete Buildings

The realistic determination of damage estimation and building performance depends on target displacements in performance-based earthquake engineering. In this study, target displacements were obtained by performing pushover analysis for a sample reinforced-concrete building model, taking into account 60 different peak ground accelerations for each of the five different stories. Three different target displacements were obtained for damage estimation, such as damage limitation (DL), significant damage (SD), and near collapse (NC), obtained for each peak ground acceleration for five different numbers of stories, respectively. It aims to develop an artificial neural network (ANN)-based sustainable model to predict target displacements under different seismic risks for mid-rise regular reinforced-concrete buildings, which make up a large part of the existing building stock, using all the data obtained. For this purpose, a hybrid structure was established with the particle swarm optimization algorithm (PSO), and the network structure’s hyper parameters were optimized. Three different hybrid models were created in order to predict the target displacements most successfully. It was found that the ANN established with particles with the best position revealed by the hybrid models produced successful results in the calculation of the performance score. The created hybrid models produced 99% successful results in DL estimation, 99% in SD estimation, and 99% in NC estimation in determining target displacements in mid-rise regular reinforced-concrete buildings. The hybrid model also revealed which parameters should be used in ANN for estimating target displacements under different seismic risks.

GHG emissions from building renovation versus new-build: incentives from assessment methods

A variety of life cycle assessment (LCA) calculation methods and rules exist in European countries for building performance evaluation based on new-build. However, the increased focus on the retention and renovation of the existing building stock raises questions about the appropriateness of these the methods and rules when applied to renovation cases. Using a real renovation case, Danish, Finnish and Swedish LCA-based greenhouse gas emissions (GHGe) assessments are assessed for how they position building renovation in relation to demolition and new-build reference values. The influence of these three different methods is examined for future development policies. Results show that upfront emissions for renovation are significantly lower for all approaches. The Swedish approach had the lowest GHG emissions compared with a scenario with demolition and new-build due to the method, which only includes upfront emissions of new materials. The Danish and Finnish renovation cases each performed worse in comparison with the new-build future emissions, specifically from operational energy use. Therefore, method development should consider incentives for upfront and future emissions. Furthermore, methods could account for the existing materials in the building, which are included in the Danish and Finnish approaches. This would provide incentive for renovation and reuse. Policy relevance Future policymaking needs to consider the influence of LCA methods on climate impact assessment of building renovations. The temporal differences occur when renovation is compared with demolition and new-build. Policy needs to take account of these temporal differences for apportioning GHG emissions between upfront and future emissions. A key question is whether existing materials should be included in the assessment as this would incentivise the reuse of these materials. Differences in accounting for the impacts of biogenic carbon in materials yields different results. This is a key issue in carbon accounting and will influence future practice.

Building energy consumption under occupants’ behavior uncertainty in pre and post-renovation scenarios: a case study in Italy

In Europe, the energy renovation of the existing building stock is a great opportunity to significantly reduce energy consumption and greenhouse gas (GHG) emissions and reach the European sustainability targets. In this framework, building energy simulations (BES) tools are very useful in verifying energy retrofit measures' effectiveness and compliance with national standards. However, an inaccurate numerical prediction, the so-called “performance gap” between measured and numerical performance, is often obtained, mainly due to the inherent uncertainty of model input. Due to its stochastic nature, the occupants’ behavior (OB) is considered among the key contributors to this gap. However, the most recent Building Energy Model (BEM) approaches adopt deterministic hourly-defined profiles for characterizing OB, thus neglecting the related uncertainty. In this work, the impact of OB uncertainties on energy consumption (EC) prediction is evaluated by adopting a Karhunen-Loève Expansion sampling technique, used to randomly perturb OB profiles such as heating setpoint (HS), internal thermal loads (IL), and windows opening (NV). Two BEMs of a typical Italian residential building in pre- and post-renovation scenarios are considered and calibrated on real EC data. The results demonstrated that HS uncertainty has the highest impact on EC in all scenarios. Moreover, the higher the energy performance of the building, the higher the impact of OB, especially for IL and NV patterns.

Adaptive reuse of industrial heritage building – comparative life cycle assessment using a case study in Norway

Materials production dominates the total Greenhouse gas (GHG) emissions in the construction industry. On the other hand, most existing building stocks are expected to last for the next 30 years, which can contribute to increasing resource efficiency, reducing environmental impact, and creating social, cultural, and economic values for society. Therefore, it becomes vital to investigate the environmental impacts of adaptive reuse of existing buildings using a life cycle approach. The objective of this study is to explore the environmental performance of adaptive reuse of an industrial heritage building compared to new construction using a life cycle assessment (LCA) method. The environmental impacts of the selected case study are evaluated using four scenarios, with two adaptive reuse scenarios, a warehouse or an office building and two new construction scenarios, a new warehouse or a new office building. One-Click LCA is used as an LCA tool, and the scenarios are compared by total carbon footprint, life cycle models, GHG emissions per building elements and material types. The results show that among the four scenarios, the adaptive to warehouse scenario is the best adaptation option with considerably lower environmental impact, followed by the adaptive office scenario. This paper highlights that adaptation of existing industrial heritage buildings, with the least materials replacement option, is worthwhile. The further evaluation needed for the study’s limitation is also highlighted for data efficiency and potential for further research.

Comparative Life Cycle Assessment of refurbishment alternatives for façade assemblies typically used in existing buildings in the Mediterranean region in Spain

The building sector is a major contributor to the environmental impact in the European Union due to energy consumed, extraction of resources and greenhouse gas emissions. Particularly, the existing building stock represents a greater challenge than new constructions, since up to 85% of the buildings existing in 2050 have already been built. The extensive lifespan of buildings mean that construction assemblies remain standing for long periods of time, which accounts for most of the embodied environmental impact and affects its energy performance during the use stage. Also, because the façade surfaces generally cover most of the building envelope, they have strong potential to reduce existing buildings’ environmental impacts and energy consumption, when undertaking major refurbishments. This paper aims to compare the environmental performance of different refurbishment alternatives for façade assemblies typically used in existing buildings in the Mediterranean region in Spain. For this purpose, a three-step methodology based on a life cycle approach was applied: (I) Identification of existing façade assemblies and their related refurbishment alternatives, (II) Bill of Materials, and (III) Environmental, cost and energetic impact of each façade and their refurbishment alternatives were analysed with the Life Cycle Assessment and Life Cycle Cost methodologies and U-values calculation, respectively. The results were used to draw conclusions to help construction sector practitioners, such as building designers and contractors, to make decisions during the design and construction stages in major renovation projects. They could also be used to select the optimum façade refurbishment alternatives, aiming at nearly zero-energy buildings.

Energy retrofitting of heritage buildings: an integrated methodology

A resilient and sustainable way of life presupposes the reduction of the energy consumption and the relevant greenhouse gas (carbon) emissions. This approach leads to the establishment and implementation of various directives and regulations regarding the refurbishment of the existing building stock. Often, these regulations exclude heritage buildings due to the lack of robust methodologies which will ensure a balance between the energy retrofitting and preservation of the building’s heritage values. Heritage buildings however, host a variety of public uses and their holistic and successful energy upgrade could serve as an excellent example of a heritage building energy refurbishment to the community. Thus, there is an emerging need for developing such methodologies. This paper aims to propose an integrated methodology for the energy retrofitting of heritage buildings, based on a multi-criteria decision-making process for the selection of the appropriate retrofitting solutions considering simultaneously the heritage significance, the heritage and the energy impact.