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Building Upward: Methodological Approach to Defining Criteria and Guidelines for Interventions for Italian Post-War Housing Refurbishment in a Seismic Area Angelo Bertolazzi, P.E., Ph.D. 1; Marco Campagnola2; Giorgio Croatto3; Umberto Turrini4; and Giovanni Santi5 1Univ.

of Padova, Dept. of Civil, Environmental, and Architectural Engineering, [AQ1]Padova 35131,

Italy (corresponding author). Email: [email protected] 2Univ.

of Padova, Dept. of Civil, Environmental, and Architectural Engineering, [AQ2]Padova 35131,

Italy. 3Univ.

of Padova, Dept. of Civil, Environmental and Architectural Engineering, [AQ3]Padova 35131,

Italy. 4Univ.

of Padova, Dept. of Civil, Environmental and Architectural Engineering, [AQ4]Padova 35131,

Italy. 5Univ.

of Padova, Dept. of Civil, Environmental and Architectural Engineering, [AQ4]Padova 35131,

USA. 6Univ.

of Padova, Dept. of Civil, Environmental and Architectural Engineering, [AQ4]Padova 35131,

U.S.A. 7University

of Pisa, Dept. of Energy, Systems, Territory, and Construction Engineering[AQ5].

Abstract Refurbishment of existing buildings, in order to reduce environmental impact, both in terms of land take and CO2 emissions, must be one of the priorities of the whole building sector. Quantitatively,

residential housing built in 1950–1990 accounts for the highest energy consumption, since its lowquality technology has caused its swift material and performance-related decay (not to mention social and urban), as reported in 2011 by the Building Performance Institute Europe (BPIE). In Italy, the earthquakes in Umbria and Marche (1997), Abruzzo (2009), Emilia (2012), and Lazio (2016) made it imperative to resort to seismic risk prevention, before the energy-consumption analysis. The paper presents the first results of the research concerning methodologies and qualitative analyses, whose objects have been twofold:  identifying the criteria and guidelines of intervention when adding floors, paying particular attention to construction-related and structural aspects within the seismic analysis; and

 testing such criteria through one case study, namely a 1970’s Azienda Territoriale Edilizia Residenziale (ATER) social housing building in Rovigo.

The analysis of the building and its modelling through ad hoc software (Revit and Midas) has determined a first evaluation of its feasibility in a digital environment, analysing the building’s structural behavior under seismic action before and after the intervention—besides while work was in progress—underlining the potentialities and drawbacks that adding floors implies. Author keywords: Refurbishment; Social housing; Floor addition; Reinforced-concrete frame; Seismic risk; Cross-laminated timber (CLT)[AQ6].

Introduction The urgency of reducing land take and environmental impact with regard to CO2 emissions has made the upgrading of XX-century[AQ7] buildings an absolute priority for the whole building sector (scientific researchers, engineering and design professionals, local municipalities, and other stakeholders), as spelled out by the Roadmap to a Resource Efficient Europe (Roadmap to a Resource Efficient Europe ) (Table. 1). (Multiindicator non-industrial amd Cohen (1995)’s) of all buildings—in Italy and elsewhere in Europe—residential housing (dating back to 1950–1990 and built without attention to seismic-resistant construction and energy consumption) accounts for the highest percentage of urban areas. The most noticeable consequence has been the swift downgrading of housing from a social and environmental point of view, since low technological quality has led to a rapid decay as far as materials and performances are concerned (Gorse and Highfield ; Carotti ).

The 2011 Building Performance Institute Europe (BPIE) report (Amasiu et al. ) has analysed European buildings, underlining the sector’s wide-ranging complexity, mostly resulting from various project-linked construction techniques and urban policy strategies enacted by EU countries between 1950 and 2000. The report also says how 75% of the total urban area is taken up by housing [Fig. 1(a)], about 83% of which was built between 1950 and 1990 [Fig. 1(b)] to meet two kinds of demands: a merely quantitative one for the massive residential settlements (1950–1970) [Figs. 2(a and b)] [AQ8]and another (1970–1990) that, though still quantitative, was more bent on quality. Both, however, are far from attending to energy consumption issues. Focusing now on Italy, according to the same BPIE report, the residential sector constitutes 83% of the total buildings, 85% of which were from to the 1950–1990s, when norms in reducing energy consumption started being implemented. It is to be underlined, anyway, that buildings from the 1980s and 1990s (which amount for 13.8% of the total), in spite of the first national building codes dealing with reducing energy consumption, are still far from being energy friendly (Appendix 1). Nowadays building refurbishment offers the greatest potentialities in the field of construction as a whole with positive economic, social, and environmental side effects. According the BPIE report (Amasiu et al. ), the improvement in the field of construction regarding energy efficiency and use of existing buildings would lead to a 42% drop in total energy consumption, a 35% cut on greenhouse gas emissions, and over 50% reduction of new raw material production. For a long time, in fact, demolition has been regarded as the only viable solution (because it is cheaper than refurbishment). However, the wide-ranging issues posed and the differentiated features of buildings have demanded new multidisciplinary insights into the approach and plans, along with a wider range of possible interventions: from regeneration of the building to conservative restoration, from energy to structural refurbishment (Grecchi and Malighetti ; Bromley et al. ; Pearce ; Kohler and Hassler ; Latham ). Among the various possible interventions, the addition of floors has been attracting new interest in EU countries. On the one hand, adding a new floor to an existing building meets the demand for further housing without any land take. On the other hand, such a volume increase may become the driving force for an economically sustainable refurbishment, since a highly technological volume increase may provide energy to the whole building. In this way, it becomes upgraded to[AQ9] an architectural, energy-friendly, urban, and social point of view (Ferrante ). This is also in keeping with

the EU guidelines to reduce land take by 2050 (European Commission ), agreed on at a national and regional level. These guidelines promote the simplification of procedures regarding interventions of rehabilitation and upgrading of decayed urban areas, the protection of agricultural areas, incentives for urban upgrading thanks to advantageous fiscal compacts, and favouring the energy efficiency of the buildings by means of demolition and rebuilding. However, quite undesirable issues stem from the fact that the structure of the building may not be able to bear any further weight or the impact of a possible earthquake (European Commission ).

Notation List In Italy, however, the earthquakes in Umbria and Marche (1997), Abruzzo (2009), Emilia (2012), and Lazio (2016) were made as an imperative to deep seismic risk prevention, before every energyconsumption analysis in the refurbishment project. Two have been the main objects of the research:  The first, of a general character, has focused on setting down criteria and guidelines of intervention as the essential starting point of technically feasible and economically sustainable refurbishment of Italian post-war residential housing, paying particular attention on the seismic risk analysis; and  The second, of a more specific character, instead, has focused on a case study from a geometrical, material, and construction-related point of view, devising light and reversible construction systems to be applied to the floor addition. The intervention has been analysed in a digital setting, above all focusing on the remaining structural behaviour of the building before, after, and during building, within the seismic behavior analysis. Applying the criteria of intervention to a real case study not only has verified them critically but also evidenced the feasibility of performing the addition of floors by means of structural crosslaminated timber (CLT) panels.

Methodology

The research “Upone” is currently being developed by the Civil, Architectural, and Environmental Engineering Department of Padua University and the Department of Engineering of Pisa University. It is characterized by a marked project-based approach, whose objective is a construction system based on the typological and construction-related study of buildings from the 60s and 70s. This paper reports a first test of its feasibility, studying an existing case study representative of 60s and 70s Italian residential buildings. The study has been further divided into three subsections connected from a logical and methodological point of view. The main sections are: 1. analysis of existing buildings from the point of view of the common housing typologies in 60s and 70s, focusing on materials, construction techniques, and the setup of existing structural elements. This analysis was in order to discover both the critical issues that might result from the new stresses caused by the addition of a floor and its weight-sharing and construction-related features; 2. focus on a real case study, that is, an Azienda Territoriale Edilizia Residenziale (ATER) building in Rovigo built in the early 70s, which has been analysed from a geometric, material, and construction-related point of view, to realistically define its features and the remaining resistance that the weight-bearing elements are capable of producing, as a consequence of both the decay of the material and the previously existing structural setup in relation with one of the buildings after the addition of one floor (Appendix 2); and

3. design a light, flexible, and modular system based on CLT panels. This system has been studied to be applied both to flat and pitched roofs. At this stage, the structure has been tested (before and after the intervention, as well as while work was in progress) in a digital setup by special software (Revit and Midas), focusing the structural analysis on seismic risk.

Italian Residential Buildings: Materials, Techniques, and Construction Types 1960–1979 The analysis of the 60’s and 70’s technological horizon and of the case study focuses on methodological aspects related to the upgrading project (Table 2), beside underlining criteria and guidelines, concerning the sustainability and reversibility. Italian building techniques have preserved traditional features up to the 60s (Poretti ), though modern techniques and materials have been the objects of experiments, leading to halfway between

tradition and innovation construction and structural typologies (Guenzi ). For example, concrete has always been regarded as one of the various possible materials, together with other more traditional structural elements, and its employment has been limited to substituting some parts of the building, that is, wallworks or some types of horizontal structures. Since the early 20th century, the reinforcedconcrete framework—whose real performing features were not immediately understood—presented a wide range of technical solutions, especially within a mixed-type construction where the traditional wallwork had a more relevant structural and construction-related role than a mere building envelope (Bertolazzi ). This was the result of Italian entrepreneurs securely connected to the brickwork tradition, but also from post-World War II political decisions that preferred traditional technical choices rather than the industrialised construction (and therefore the prefabrication), as witnessed by the Piano INA-Casa (1949–1963) (Beretta ; Pace ). This has influenced Italian construction up to today, accounting for its extremely heterogeneous features. The main construction type emerging from analysing post-World War II residential housing has been the reinforced-concrete framework with hollow clay tile concrete floors and full-brick (later on, it was hollow brick) infill walls [Figs. 3(a and b)]. The success of this construction type is witnessed by its increasing five times between 1950 and 1990 (Table 3). Starting from 1945, Italian technical handbooks have been describing in detail what were more often defined as “elastic structures,” that is, made up of elements capable of withstanding strain bending, while hollow bricks have been increasingly used for infill walls (Rossini and Segrè ). The structural construction-related pattern that was getting established starting from the 50s underlies the settlement layout that has been the constant feature of Italian residential housing. The protagonists of the building boom in towns have been either turret-like multistory blocks of flats [Fig. 3(c)] or horizontally lying apartment buildings. The latter have been hampered from a planimetrical point of view by the need to position stairs and have therefore several accesses (horizontal and especially vertical), which nowadays makes upgrading difficult [Fig. 4(a)].

The resulting most common elementary typological module consists of a collective, accessible by inmates [AQ10]stairwell and lift leading to the various stories of the building. Generally, there are two apartments on each floor, though in some cases there may be as many as four or six [Fig. 4(b)]. Such typological modules have been separately used in horizontally lying apartment buildings obtained by merely adding and joining a further module to the short transverse side. This implies that the heads of the modules should be blind, with no openings to the outside, to allow for the next module to be joined. In all various kinds of horizontally lying apartment buildings, therefore, openings are necessarily confined to the longer, opposite sides. The preceding survey dealing with typological and construction-related aspects apply to residential buildings, both private and public. In the latter case, in fact, even if in some instances more industrialized techniques have been used, and innovative layouts and spatial solutions experimented, most interventions in smaller buildings (e.g., Rovigo) have followed the previously summarized layouts and technical solutions (Appendix 3).

Interventions on Existing Buildings: Criteria and Guidelines for the Addition of Floors The complexity, the variables, and the number of residential buildings—raised from the 50s onward in Italy and elsewhere in Europe—make necessary the identification of general guidelines steering the seismic and energy-saving refurbishment. These prove better than new project-related parameters or new assessment methodologies, which have already been widely laid down by new binding norms [DM [AQ11]January 14, 2008, Norme Tecniche delle [AQ12]Costruzioni or NTC () and subsequent additions], especially after the seismic events in Italy during the last 20 years (Appendix 4). Such guidelines must mainly aim to provide an operative tool for implementing project-based plans, where existing building knowledge is the necessary starting point for technically feasible and economically sustainable interventions. In the present research, the first step has been analysing present-day Italian norms—as far as the addition of floors is concerned—referring to specific national and regional norms as No. 14/2009 law “Piano Casa,” where a norm allows volume increasing to promote construction, thanks to lateral and vertical extensions of existing buildings. At the same time,

it further improves energy performances, architectural features, and seismic upgrading. Such norms deal with two hypotheses of intervention: adding a lateral volume or adding [AQ13]above the existent building. The first one involves fewer technical problems; however, it is rarely viable due to the high housing density in the outskirts of towns and to binding architectural norms regulating distances between buildings, between roads and buildings, and in general between private property boundaries. The second step, that is, the addition of a floor—though resorting to increased volumes—does not tamper with buffer zones. Its feasibility depends only on the capacity of the building to bear the addition of further structural elements in terms of resistance. From this point of view, reference must be made to NTC (), defining how interventions must be carried out in order to ensure the desired degree of safety (Appendix 5). In the case of the addition of a floor, the intervention result must be tested when such a floor is connected to the existing building and interactions are such as to cause noteworthy variations to the structural behaviour of the existing building. Regarding interventions increasing volumes (especially vertically) have mostly proven unfeasible, owing to their excessive costs caused by the necessary upgrading to meet the new seismic norms. The problems posed by the interaction between what is newly built and what is old as far as structures are concerned are of primary relevance. Fitting new structures to an already-settled static context, without correctly calculating the globally induced structural variations in relation to rigidity, masses, and centres of mass distribution, may even lead to catastrophic consequences both for the building and especially for its dwellers if an earthquake strikes (Franchini and Turrini ). When a floor is added, a most attentive check on how the two structures collaborate must be carried out: the new structural organism consists of collaborating structures. In general, as with new composite steel/concrete or wood/concrete structures, even in this case the two structures should be checked as forming only one structural organism, with their modified rigidities and masses, as well as the elements interconnecting them (Turrini ). From a feasibility standpoint, [AQ14]in order to carry out a sustainable floor addition, some functional and construction-related guidelines have been laid down (Table 4), which have been

checked via a study case. After the analysis of 60’s and 70’s residential buildings, the main operational requirements are:  limiting weights added to the existing structure, and  cutting down installation times, to reduce construction costs. Therefore, the guidelines in order to reach the first operational requirement are:  using light elements,  studying the interface between the added floor and the existing building, and  reviewing [AQ15]the reversibility of the structure. On the other side, the guidelines about the second requirement are:  largely resorting to prefabrication,  dry-laid elements. A first assessment of the criteria of intervention was performed, so as to suggest further new criteria to be added to the former. This proves that a fact-based check is always valuable and provides more thorough insights. In examining each preliminary criterium in detail, some considerations may be reached. The criteria devised in the first phase mainly regarded limiting the loads added to the existing building, choosing the solutions that kept them unchanged, or, better still, helped decrease loads between “as built” and the project design. This leads to structural and architectural choices resorting to light finishing materials, affording high thermal performances, and decreasing foundation loads or even seinng-up[AQ16] the preconditions for improving foundations. It is nearly impossible to examine the soils under a building and even more so to devise a strategy of reinforcement without almost totally demolishing the floors of ground-floor flats. This specific goal—reducing foundation loads—can be reached, since the weights of the pitched roofs of existing buildings can easily equal the weight of the new volume that is to be added. This statement will be thoroughly discussed in the case study, providing the real amounts of the loads measured before, during, and after the intervention, as reported in the following paragraph.

Finally, in order to reach the reversibility, the interface between the existing building and the new volume is fundamental. The new project should [AQ17]improve its overall static behaviour without new stresses, and so resorting to incompatible static patterns (as cantilever elements, wide openings, or project-related solutions creating concentrated loads) does not allow a homogeneous distribution of the new loads on the existing structures. In order to verify such criteria, they have been applied to a study case that has provided data to confirm them (or not). It has also been suggested to focus on some relevant items, such as the rising of the barycenter of the global masses of the building in relation to the basic behaviours of vibration, as will be shown further. Transferring theoretical findings to a concrete case has allowed the integration of the identified criteria. The analysis of 1950–1990 Italian residential neighborhoods has underlined its very high density, which makes the addition of floors operationally difficult. Limited construction times not only lead to reduced costs but also to less inconvenience for those living there. Providing them with temporary dwellings while adding another floor to their homes may further boost building activities. At the same time, dry-laying elements and high levels of prefabrication reduces intervention [AQ18]times that—if possible by the conditions around the existing building, such as easy access and transport of preassembled parts—can allow completion of a living module directly on top of the building, drastically reducing the finished work (Ferrante ).

The Case Study: The Rovigo Azienda Territoriale [AQ19]Edilizia Residenziale Building The building was singled out in order to experiment the validity of the intervention criteria belonging to the Rovigo Istituto Autonomo Case Popolari (IACP)—later ATER—residential complex, raised according to the construction plan laid down by No. 1179/01.11.1965 law whose aim was boosting construction. The project was laid down in 1967 and the building completed in 1972. The complex consists of 13 housing blocks, 4 of which were detached [Figs. 5(a and b)]. All are aboveground four-story blocks, the ground floor being used as a garage, the remaining three floors having

two 90 and 80 m2 apartments each [Fig. 6(a)]. The choice as a case study has been dictated by evaluations regarding structural and construction-related features and their being capable of representing the technological setup of the period under survey.

Description of the Construction Elements and the Structure The load-bearing structure consists of a reinforced-concrete framework made up of three longitudinally layered frames connected transversely by beams. The plateau-shaped foundation with a ventilated underfloor cavity is situated at a −1.26 m level to the ground level, and the hollow clay tile concrete floors are laid along a north-south orientation. Archived inquiries have underlined how while work was in progress it was decided (September 3, 1970 DL, in historical archive ATER Rovigo) they would resort to a plateau foundation (in contrast to the original project that had a planned continuous foundation surrounded by a short step). Also, on that occasion, the floor was rebuilt, resorting in hollow clay tile concrete with a ventilated underfloor cavity. The change was dictated by the geotechnical surveys of the ground. The bearing piles rise vertically, with recesses and projections at the floor levels. In particular, tapering has been spotted in the piles inside each floor. The sections examined [Fig. 6(b)], which do not follow a precise pattern, vary between 0.25 and 0.50 m, and only some vertical elements have their longer sides between 0.6 and 0.7 m. The main (0.4–0.7 m long) beams—wider than the uplifted edges supporting them—lie with an east-west orientation and are as thick as the complete floor: 0.24 m on the bottom three floor levels, and 0.20 m the top [AQ20]floor levels. The structural 0.2 m-thick hollow clay tile concrete roofing is supported at its pitch by a reinforced-concrete beam set on top of the top floor and supported by nonreinforced brick pillars. The infill walls of the frame differ. Stone has been used on the ground floor, full bare brick on the short sides, and plastered brick on the other sides. The steel rods inside the concrete elements have been assessed by means of analyses of archived documents, norms then in force and in situ surveys carried out with suitable instruments (pacometer).

The figures resulted from the assessment tally with the ones set down by the norms about reinforced concrete of those times. The norms in force at the time the project was made and the building raised were the ones in Regio Decreto No. 2229/1939 “Norms concerning raising concrete or reinforced concrete buildings.” With regard to the features of the materials, the norms in Regio Decreto 2229/1939 said that the average cubic strength at 28gg[AQ21] of concrete should record at least 120 kg/cm2, three times as much as the reckoned safety load, to the highest figure of 180 kg/cm 2 in pressed elements, and up to 225 kg/cm2 for the ones inflexed or subjected to combined pressing and flexing stresses. In relation to the lowest reference figures that can be applied to define the reinforcement bars of piles according to Regio Decreto No. 2229/1939 (Appendix 6), and with the original construction details [Fig. 6(c)], it has instead been possible to define the lowest reinforcement figures for each section of the piles with satisfactory approximation (Table 5).

Deterioration, Flow Sides, Seismic Fragility, and Definition of Basic MaterialRelated Parameters The direct survey of the building has allowed the assessment of some signs of deterioration: reinforcement covering falling down [Fig. 7(a)], flaking off [Fig. 7(b)], biological attack by moss. At the joints of the panels of the central framework, traces of puncturing could be seen [Fig. 7(c)], evidence of the low standard of construction details. The joints were generally without any bracketing, and therefore their degree of containment was low. The steel bars used in longitudinal reinforcement, as in most buildings of the time, are smooth and have grappling hooks at both ends, with no connection between the upper and lower bars. The heterogeneous materials and the distributive layout of infill walls causes the building to present a soft story at the ground level, mainly along its longitude. Here, the whole deformation tolerance rests with the beam-pile system, since buttresses or concrete cores causing meaningful stiffening are absent. As years went by, the inadequacy of construction details has brought to light the collapse-prone features of junction structures, in particular junction panels, that is, the elements of intersection between piles and beams. In particular, this is what has been noticed:

 inadequate containment by means of brackets, leading to possible formation of plastic hinges;  insufficient (sometimes completely absent) transverse reinforcement in the areas of the junctions;  inadequate details regarding the anchoring of longitudinal reinforcements ends, mostly by means of bent hooks;  insufficient longitudinal reinforcement of the pillars;  insufficient overlapping of the longitudinal reinforcement irons of the piles and above-floor level; and  low-quality steel and concrete, to be noticed by the scanty adhesion of the smooth reinforcement bars. From the point of view of seismic resistance, instead, the most serious problem is posed by the closeness of the two blocks of flats, which can result in seismic pounding, should an earthquake strike. After examining the original available works and the geometric reliefs carried out in situ, we have chosen to apply the LC1 [AQ22]level of knowledge:  for wallwork elements, reference should be made to minimum values for resistance and to medium values of interval for elastic modules, as reported in the C8A.2.1 table in NTC (); and  for concrete elements, reference should be made to the usual values in the construction practice of the time. To the ascertained level of knowledge is connected a confidence factor of [AQ23]CF = 1.35. Setting up a suitable model for linear dynamic analysis is also allowed. Not possessing experimental data stemming from nondestructive, semidestructive, and destructive tests, it has been decided to define a class of concrete having cubic resistance halfway in the scale of the previously quoted values to make reference to. With reference to present-day types of concrete and their mechanical performances, it has been deemed profitable to resort to C16/20 concrete, that is to say concrete having [AQ24]fck = 16 N/mm2 cylindrical characteristic resistance and Rck = 20 N/mm2 cubic characteristic resistance, according to the Italian building code that foresaw the concrete classification using samples of cylindrical or cubic form.

The Addition of Floors: Flexible Additional Modules Project

Relying on the previous general criteria and on the analysis of existing buildings, the addition of floors has been approached by the flexible additional modules (FAM) project developed as a reversible and light construction system for upgrading residential housing (Appendix 7). Its most innovative feature is its adaptability to the various planimetric situations of existing buildings as well as to the different urban environments. The FAM system [Figs. 8(a and b)] results from a typological study of post-World War II Italian residential housing, with reference to materials and the structural patterns and layouts most commonly used. Besides the materials, the construction systems, and the structural typologies listed in the previous sections, the research has shown that the average gauge of multistory residential housing with reinforced-steel framework is about 4.5–5 m, a figure confirmed by both technical handbooks and 2011 ISTAT (Istituto Nazionale di Statistica) data. In FAM, the main material is CLT; it is used in panels and has considerable advantages:  CLT panels allow the added floor to be free from the top structures of existing buildings and from the gauges of structural frameworks, which sometimes vary;  CLT panels afford outstanding energy-savings and acoustic performances that can even be further improved with suitable cladding; and  CLT panels, being modular, (maximum height = 2.95 m) allow a reduction in the number of the elements and metallic connectors, which results in sizable cuts in installation times. Resorting to a CTL load-bearing structure (both for floor and walls) supported by the existing reinforced-concrete frame and connected by means of HEA 280 (H European series A)-flanged beams meets some of the requirements both of the structure of the existing building and of the newly added floor. The space between the existing and the new floor is configured, along with a technical compartment, appropriately protected by the overlay coating, which is then expected to continue on the underlying part (Fig. 9). Regarding the former, a direct connection between the CLT wall and the former roof is avoided. Its limited thickness (200 mm) and poor mechanical performances with resistance and warping make it difficult to resort directly to connection systems (i.e., hold down and cut-to-size plates). At the same time, the steel beam HEA system allows the loads of the added floor to be directly transferred to the reinforced-concrete framework, without further weighing down on the structure below. With the latter, instead, it is possible to house CTL walls in grooves on the metal beams, while the CLT structural

floor can be laid directly on the top face of the HEA beam. Creating 180 mm-wide channels along the centre line of the beams provides[AQ25] the housing of the wires and pipes of the new floor as well the vents of the original building (Fig. 10). The application of the FAM system has allowed the creation of new volumes on top of the building chosen as a study case, raising two modular interconnected residential units, thanks to the central stairwell of the existing building. The stairwell’s location, which is typical of the residential buildings of this period, has facilitated the project of elevation for access to new housing units, which would have been much more burdensome in the case of different planimetric settings [Figs. 11(a and b)]. After removing the existing roof, the two modules (types A and B) have been set up, adding an entire new floor to the building. Type A consists of two apartments, their sizes being 72[AQ26] and 78 m2. The Type B apartments also have two, sized 66 [AQ27]and 68 m2. A shared landing leads to the apartments; it can be reached thanks to a staircase added when designing the addition (Fig. 12).

Structural Considerations on Upward Addition Solutions and Analysis of the Results The expansion, also in superelevation, are widely dealt with in the current Italian norms, defining the required steps to satisfy new safety levels, as stated in the 8.4.1 paragraph “Adaptation intervention” of NTC (). The norm—DM January 14, 2008, at 8.4.1 point—forces the safety assessment and, if necessary, with the adaptation of the whole buildings, for the following interventions: 1. upward addition; 1.2.

great enlargement involving the structure with more than a 10% increase in foundation

loads; 1.3.

enlargement of the whole building through structurally related works. The norm states to

proceed to the local verification of every parts and/or elements of the structure, even if they concern limited portions of the building; and 1.4.

structural interventions aimed to transforming the previous building into a different one,

through a systematic set of structural works.

Formatted: Bullets and Numbering

Every enlargement needs an adjustment if the new part is structurally connected to the existing building and the new volume introduces significant changes to the structural behavior of the existing one. In the case studied, therefore, regardless of the dynamic analysis results, it is necessary to provide for the building’s seismic upgrading, which usually involves significant interventions, both from a functional and economic point of view. Moreover, according to current norms, the characteristics of the materials used and the techniques used in structural junctions (type of steel, reinforcement spaces, etc.) (Appendix 8) are required to proceed to structural adaptation. In order to be in keeping with the new design methods, as the new 2016 Public Procurement Code, the upward addition was studied by an integrated procedure, based on the computer modeling of the Revit Autodesk program and the structural modulator/solver FEM Midas Gen 2017 [Figs. 13(a– c)]. Modelling Min an information-technology environment has focused on defining the stages of construction, the assessment of the existing building, the transitional stage with the removal of the roof, and the project showing the addition of the floor completed. It is relevant to underline how essential such a procedure is. The static behaviour of the building in the transitional stage cannot be undervalued, that is, when the global structural setups can be modified—even meaningfully—should they prove inadequate and dangerous if undergoing possible uncontrollable dynamic actions (earthquakes). The evaluation of the building’s seismic behavior is carried out by a linear dynamic analysis. The seismic action modeling is therefore made through the identification of response spectra according to the case study (Rovigo) site, the characteristics of the soil, and the structure. The soil categories, the topographic categories, and the related topographic amplification coefficients provided by the Italian norms are described in Tables 6 and 7. The geognostic surveys show that the soil stratigraphy is predominantly a silty-sandy type with alternating layers of silt and sand, of limited extension, namely a “E” category. The topographic amplification coefficient is related to the case study structure location

and terrain geometry. The L1 ATER Rovigo Building has been defined a coefficient ST = 1.0, related to a topographic category T1 or “flat surfaces, slopes, and reliefs with an average inclination of ≤ 15°.” The seismic action for the case study site was determined by the program Spettri-NTCver.1.0.3 (Fig. 14). Independent ad dipendet[AQ28] parameters for the seismic analysis are in Tables 8 and 9, and the project spectrum used for linear dynamic analysis is reported in Fig. 15. The dynamic analysis that traces [AQ29]the behaviour of the buildings is meant as a displacement and way of vibrating, leading to the following considerations. Throughout the three stages of building transformation, the two housing blocks, “west block” and “east block,” show comparable global behaviours, stemming from a similar—though not analogous—geometry. They have been analysed separately since they do not form an uninterrupted structure and have shown quite similar behaviours. Throughout the three stages of transformation, they show evidence of a first translational (along the y-axis) way of vibrating, a second translational (along the x-axis) way of vibrating, and a third is rotational. However, the ensuing periods of vibration and the highest displacements of the plane are different (Fig. 16). In the first stage of the intervention, the removal of the roof causes a 930 kN reduction of the mass, leading to a general reduction of the periods of the main ways of vibrating. However, different from what may be surmised, the reduction of the mass at the top makes conditions worse [Fig. 17(a)]. The principal period nearing the plateau area (i.e., where the diagram presents an almost parallel line to the x-axis) in fact causes about 17% higher accelerations than the ones at the start connected to greater actions and displacements of the plane: 3.3 cm at the start, 4.0 cm midway, 4.7 cm after the addition of the floor has been completed. The recorded figures confirm the hypotheses formulated during the preliminary analyses regarding the possible occurrence of pounding. In order to prevent the damages caused by the close proximity of the two buildings, it is therefore necessary to take precautionary measures, whether or not any addition of floors is planned. Coming to the stage of adding the floor, the new volume produces a slightly greater mass than the mass of the demolished roof (the difference being 250 kN), even if the analyses show an

approximate 10% increase in the periods connected to the ways of vibrating. Such a condition causes the reference acceleration to be reduced as a result of it moving farther away from the TC [AQ30]period of the spectrum [Fig. 17(b)]. Following the tests carried out on the real model, the preliminary guidelines formulated at the beginning have proved valid. Moreover, new meaningful findings and observations have made them more complete, especially:  verifying the structural setup of the building even at a transition stage, in order to detect possible potentially dangerous behaviours against the occurrence of unavoidable events: earthquakes, wind, snow; and  verifying the shifting of the barycenters of the global masses: their rising can in fact cause even greater displacements of the plane compared to the situation at the start. Very synthetically, after the necessary additions suggested by the analysis of the case study, the two new guidelines concerning limiting the added loads on the existing structure are (Table 10):  Studying the interface between the added floor and the existing building at the transitional stage; and  Assessing the position of the barycenter before, during, and after the addition of the floors. Regarding the frailty of the existing building, out of the considerations so far laid down about the construction techniques and the materials used, it can be stated that post-World War II buildings may show evidence of even glaring structural problems, particularly with earthquake-triggered dynamic actions. These problems have proved to be dramatically relevant nowadays, urging interventions not only on post-World War II buildings but in the light of the recently crumbled fivestory block of flats in Torre Annunziata (Napoli). Their seismic vulnerability and evident structural shortcomings depend on the underlying structural conception and their general features, such as irregularity in plans or raising walls. Interventions can be targeted on seismic and static retrofitting of reinforced-concrete structures, modifying them globally or partially. Local interventions may focus on individual floors or piles, whereas global interventions may involve:

 new either stress-discharging or hyperstress-resistant buttresses;  reinforcing existing walls, for example, lift shaft or stairwell walls, perimeter walls;  strengthening curtain walls; and  base insulation. Global interventions are usually the most suitable and reliable ones from a structural point of view, though they often prove to seriously impact existing structures. In conclusion, therefore, the research has so far ascertained whether the additions of walls compatible with existing buildings are viable, by means of analysing the most suitable methodologies, which depend on new functions and the global behaviour of the buildings after the interventions are completed. The guidelines have further been verified on the case study of a period building; this has provided precious feedback as well as additional verifications of previous considerations; this has led the previously formulated hypotheses being streamlined in the light of the figures obtained.

Conclusions and Future Developments To sum up, it can then be stated that in these kinds of buildings, increasing the mass at the top does not improve the existing structure and may even lead to amplified displacements, even though the structure is subjected to lower accelerations. Therefore, the hypothesis formulated is that the barycenter of the masses must have shifted upward. The consequence is that the main problem cannot be regarded as being absolute mass value but rather its geometric position, since it has been observed that with a relatively scanty increase of weight at the top, the periods of vibration compared with what they were before such increase, prove noteworthy. So, different from possible hypotheses, greater displacements of the plane have been observed than in the two former stages. As said before, this must be due to the rising upward of the barycenter of the masses of the structure, which must be borne in mind as a new guideline to be added to the ones already laid down. The research so far has tested the feasibility of floor additions that would not prove harmful to the existing building, by means of analysing the most suitable methodologies of intervention with a view to the building’s new functions, its layout, and ultimately its global behaviour after the

intervention. The guidelines laid down for the architectural solutions have then been verified in the case study of a 70’s building. This has provided valuable feedback on early assessments, which has led to review of the formerly hypothesised specifications even in the light of the numeric results obtained. The main result has been achieved at a methodological level by defining the logic framework within which the project has been developed, from carrying on research regarding those years’ housing typologies and construction techniques to analysing the case study focusing on its decay-caused shortcomings as well as its potential, so as to lay down a project capable of coming to terms with the existing building from the point of view both of construction and distribution. Resorting to a CLT construction system has in fact made the added floor lighter—by fitting it to the existing structural gridwork—and used the existing stair well and lift shaft, thus potentially cutting building costs. As far as future developments are concerned, this will lead to a further phase of study focused on the feasibility of adding more than one floor, with a view of optimizing the economic return of the intervention and of envisaging a wider-ranging social impact, namely the alienation of the building, once the energy-friendly and structural upgrading has been completed. The research can also embrace new studies on cladding, such as the Exterior Insulation and Finishing System (EIFS), capable of compensating the thermal variations of the energy-upgraded building in the summer. Such solutions can be applied to the existing building and to the added floor (or floors), so as to make the envelope globally efficient. Appendixes 1. The first national law dealing with curbing energy consumption in buildings is law No. 370, April 3, 1976, “Norms cutting on energy consumption for thermal uses in buildings,” which for the first time set down the required energy performances of the components as well as the first requirements for planning, setting up, running, and maintaining thermal plants for central heating and providing hot water in public and private buildings. Moreover, rules about implementing the aforementioned law were issued (DPR 1052, June 28, 1977 and DM March 10, 1977, “Determining climatic zones and the highest acceptable volume coefficients of heat loss for each zone”);

2. With reference to NTC (), it is to be underlined that more and more comprehensive data about the building ought to be gathered, leading to structural tests based on fair appraisal and correct assessment of the context in which the building is placed; 2.3. Generally, the lengths of such buildings vary, whereas their depth remains constant throughout the axis

Formatted: Bullets and Numbering

of transverse development, varying between 9 and 12 m, in keeping with the inside layout of the apartments and the need to ensure an outside opening to each room. With regard to the height, volume, and ground area of the buildings, instead, the prescriptions and limitations have been basically laid down by the land-take plans of local councils. From this point of view, as it will be subsequently discussed, the building chosen as a case study is perfectly representative of the 1960’s and 1970’s Italian residential buildings; 2.4. Italy is one of the Mediterranean countries with the highest seismic risk, since it is located in the convergence zone between the Eurasian and African plate and is therefore subject to considerable compression forces due to tectonic movements. In 2003, a process was started in Italy for the estimation of seismic risk (PCM Ordinance 3274/2003—Official Gazette No. 108 08/08/2003). This analysis is based on data, methods, and approaches updated and shared internationally. This work led to the implementation of the Earthquake Danger Map (MPS04) in 2004, which describes the seismic risk through the parameter of maximum expected acceleration on harsh or flat ground with a probability in excess of 10% in 50 years; 5. Upgrading the existing buildings to meet certain safety criteria is compulsory when adding floors, increasing volumes by means of extensions structurally connected to the existing building, changing class and/or use causing more than a 10% increase in global loads on foundations, or carrying out transformations as the result of which the new building is structurally different from the original one; 6. Such figures are: longitudinal reinforcement area [AQ31](As) As 0.8% Ac se Ac < 2000 cm2 e As 0.5% Ac se Ac > 8000 cm2, where Ac = concrete area; the gauge between transversal bracketing (p) p 0.5 cm minimum thickness of concrete, and p 10 φ mm (φ = bars diameter) minimum section of longitudinal reinforcement bars; length of overlapping (L) L = 40 diameters; reinforcement covering (c) c > 2 cm and reinforcement gap (i) i φ (φ = bars diameter) and i 2 cm; 6.7. The FAM project stems from a research carried out within the Civil, Architectural, and Environmental Engineering Department of the Padua University, dealing with developing reversible and innovative construction systems applied to the addition of floors in residential buildings, aiming to their upgrading. The FAM project has been awarded the first prize in the Urban Densification: The City on the City, Building Upward competition, of 3rd Campus Archizinc 2014–2015; and

Formatted: Bullets and Numbering

8. The study of some old structural reports highlighted that the pillars were generally dimensioned only for vertical loads, according to typical simple compression stresses. Rarely has the frame calculation of the bending effects caused by wind or eccentricity of vertical loads been taken into account.

References Amasiu, B., C. Despret, M. Economidou, J. Maio, I. Nolte, and O. Ralf. 2011. Europe’s buildings under microscope. A country-by-country review of the energy performance of buildings. Brussels, Belgium: Building Performance Institute Europe (BPIE). Beretta, L. 1963. I 14 anni del piano INA-Casa. [In Italian.] [AQ32]Rome. Bertolazzi, A. 2015. Modernismi litici 1920–1940. [In Italian.][AQ33] Milan. Bromley, R. D. F., A. R. Tallon, and C. J. Thomas. 2005. “City centre regeneration through residential development: contributing to sustainability.” Urban Stud. 42 (13): 2407–2429. [CrossRef][10.1080/00420980500379537] Carotti, A. 2011. Riqualificazione energetica degli edifici. Linee guida per progettazione integrata. [In Italian.] Turin, USA: [AQ34]Utet Scienze Tecniche. European Commission. 2016. Future brief: No net land take by 2050? Brussels, Belgium: EC. Ferrante, A. 2012. A.A.A. Adeguamento, Adattabilità, Architettura. Teorie e metodi per la riqualificazione architettonica, energetica ed ambientale del patrimonio edilizio esistente. [AQ35][In Italian.] Milan, Italy: Bruno Mondadori. Ferrante, A. 2016. Towards nearly zero energy: Urban settings in the mediterranean climate. Oxford, UK: Elsevier. Franchini, F., and U. Turrini. 2012. Parametri di reversibilità nel recupero architettonico e strutturale. [In Italian.] [AQ36]Padova, Italy: Progetto Libreria. Gorse, C., and D. Highfield. 2009. Refurbishment and upgrading of buildings. New York: Taylor & Francis.

Grecchi, M., and L. E. Malighetti. 2008. Ripensare il costruito. Il progetto di recupero e rifunzionalizzazione degli edifici. [In Italian.] [AQ37]Rimini, Italy: Maggioli Editore. Griffini, E. A. 1948. La costruzione razionale della casa. [In Italian.] [AQ38]Milan, Italy: Hoepli. Guenzi, C. 1981. “La manualistica italiana.” [In Italian.] Rassegna [AQ39](5): 73. Kohler, N., and U. Hassler. 2002. “The building stock as a research object.” Build. Res. Inf. 30 (4): 226– 236. [CrossRef][10.1080/09613210110102238] Latham, D. 2000. Creative Re-Use of buildings. Shaftesbury, UK: Donhead Publishing Ltd. NTC. 2008. “Norme tecniche per le costruzioni.” [In Italian.] [AQ40]DM January 14, 2008. Pace, S. 1993. “Una solidarietà agevolata: il piano Ina-Casa, 1948–1949.” [In Italian.] [AQ41]Rassegna (54): 20–27. Pearce, A.R. 2004. “Rehabilitation as a strategy to increase the sustainability of the built environment.” Accessed November 18, 2016. [AQ42]http://maven.gtri.gatech.edu/sfi/resources/pdf. Poretti, S. 2007. “Struttura e architettura nel modernismo italiano.” [In Italian.] Rassegna di Architettura e Urbanistica [AQ43](121–122): 11. Ridolfi, M. 1946. Manuale dell’Architetto. [AQ44][In Italian.] Rome: Centro Nazionale delle Ricerche. Roadmap to a Resource Efficient Europe. 2011. [AQ45]Accessed June 19, 2017. http://eurlex.europa.eu/legal-content/IT/TXT/?uri=CELEX:52011DC0571. Rohracher, H. 2001. [AQ46]“Managing the technological transition to sustainable construction of buildings: A socio-technical perspective.” Technol. Anal. Strategic Manage. 13 (1): 137–150. [CrossRef][10.1080/09537320120040491] Rossini, G., and D. Segrè. 1968. Vol 1 of Tecnologia edilizia. [AQ47][In Italian.] Milan, Italy: Hoepli.

Turrini, U. 2013. Edifici storici in cemento armato: dal recupero reversibile di volumetrie alle problematiche strutturali. Ricerca ed attivitá sperimentale operativa. [In Italian.] [AQ48]Padova, Italy: Edizioni Progetto. BLS.. 2014. How the government measures unemployment. Technical Documentation. Washington, DC: BLS. BLS.. 2015. “Industry employment and output projections to 2024.” Monthly Labor Review. Accessed June 6, 2018. https://www.bls.gov/opub/mlr/2015/article/industry-employment-and-output-projectionsto-2024.htm. BRT.. 1983. More construction for the money. Construction Industry Cost-Effectiveness Project, Summary Rep. Washington, DC: BRT. BRT.. 1997. Confronting the skilled construction workforce shortage. Construction Cost-Effectiveness Task Force, Summary Rep. Washington, DC: BRT. CURT (Construction Users Roundtable). 2001. The skilled construction workforce shortage and the CURT 2001 Workforce Development Survey results. Cincinnati, Oh: CURT. Fujita, S. 2014. On the causes of declines in the labor force participation rate. Philadelphia, PA: Federal Reserve Bank of Philadelphia. Fujita, S. 2014. On the causes of declines in the labor force participation rate. SA: Federal Reserve Bank of Philadelphia. Fig. 1. The US Census regions. (a) Percentage of residential and nonresidential buildings; and (b) age ranges of European residential stock. (Data from Amasiu et al. .) Fig. 2. Massive residential settlements in Europe: Saint Denis banlieue in Paris. (Image by authors.) Fig. 3. (a) Multilayered reinforced-concrete framework (reprinted from Ridolfi ); (b) hollow brick and brick-concrete floors (reprinted from Griffini ); and c) 1951–1952 multistory residential buildings in Rome (reprinted from Beretta ). Fig. 4. Residential typologies in Italy during the 50s and 60s: (a) vertical connections in multistory buildings; and (b) layout of each floor.

Formatted: book_ref, Line spacing: single

Fig. 5. (a) Location of the case study: L1 ATER building in Rovigo, 2. Railway station, 3. Rovigo city centre (Image courtesy of ATER Rovigo); and b) north prospect of L1 ATER building in Rovigo. (Image by authors.) Fig. 6. Original drawings of the Rovigo L1 ATER building: (a) north, south, and east prospects; (b) structural plan; and (c)construction details. (Images courtesy of ATER Rovigo.) Fig. 7. Main forms of deterioration in reinforced-concrete structures: (a) reinforcement covering falling down under the balcony; (b) flaking off in a pillar; and (c) puncturing on a beam board. (Images by authors.) Fig. 8. FAM system (a) concept of the system; and (b) the system as applied to the Rovigo L1 ATER building. Fig. 9. Construction details of the panel-bracketing beam: (a) support-bearing section; and (b) centerline section. Fig. 10. Prospect of the wall and its connection. Notice the channels for wiring and piping scooped out of the load-bearing beam. Fig. 11. (a) Project layout, where it is visible to use the same stairwell to reach the new housing units; and (b) axonometric view of the first A + B module. Fig. 12. Module A floor plan. Fig. 13. (a) Architectural model; (b) structural model; and (c) analytical model of the building. Fig. 14. Screenshot of the Spettri-NTCver.1.0.3 program, which determines the seismic action for the site of interest. Fig. 15. Spectrum of the project used for dynamic linear analyses. SLV, 475 years, E, T1. Fig. 16. Diagrams of the three ways of building vibration in different configurations: actual, intermediate, project step.

Fig. 17. Spectrum of project, change of the period from the (a) start to the intermediate stage; and (b) intermediate to the final stage.[AQ49] Table 1. Resource efficiency—the interlinks between sectors and resources, EU policy initiatives, and the building sector Resource Fossil fuels

Materials and minerals Water Air Land Soils Ecosystems: Biodiversity Marine resources Waste EU policy initiatives

Building sector Reduce fossil fuels use via better energy efficiency and renewable energy use in buildings Build zero-energy buildings and increase the renovation rate of existing buildings Optimise material use Use sustainable materials Improve water efficiency of buildings and appliances Reduce greenhouse gas emissions from buildings Improve indoor air quality Avoid additional land take (e.g., for urban sprawl) Remediate contaminated sites Avoid urban sprawl on fertile soil Minimize soil sealing Ensure sufficient and connected green spaces as part of green infrastructures Reduce acidification resulting from greenhouse gas emissions Recycle construction and demolition waste (70% till 2020) Strategy for the sustainable competitiveness of the EU construction sector (2011) Communication on sustainable buildings (2013) Initiative on water efficiency in buildings (2012)

Table 2. Methodological layout of structural upgrading interventions of post-World War II buildings Action Focusing on the materials, techniques, and construction systems Focusing on a case study typical

Instruments Norms, textbooks, and reviews of the time

of the formerly defined

Archive documents, direct, geometrical, material, structural, and decay-related survey

technological horizon Modeling the existing building in simulated

Ad hoc software (Revit and Midas)

Goals Defining the technological horizon of the period under survey. Defining confidence levels (CL)

Implementing a virtual model for a first test of the building

environment

Determining the real (mechanical building and physical) building’s features

In situ and laboratory tests

before, after, and while work is in progress of the floor addition Static and dynamic test of the building and correct assessment of general conditions

Table 3. XX-century[AQ50] Italian residential housing with reference to the used materials Time

%

Before 1919 1919–1945 1945–1961 1962–1971 1972–1981 1982–1991 1992–2001 Total

7 12.3 14.8 17.5 17.7 11.5 7.0 87.8

Building material: bearing walls and/or mixed masonries[AQ51] 2,026,538 1,183,869 1,166,107 1,056,383 823,523 418,914 228,648 6,903,982

Building material: reinforced concrete[AQ52] — 84,413 288,784 591,702 789,163 620,698 394,445 2,768,205

Building material: other materials and techniques[AQ53] 123,721 116,533 204,938 319,872 370,520 250,890 167,934 1,554,408

Table 4. Criteria of intervention connected to the operational requirements of the addition of a floor Operational requirements Limiting weights added to existing structure

Cutting down installation times

Criteria of intervention Using light elements Studying the interface between the added floor and the existing building Reversibility of the structure Largely resorting to prefabrication Dry-laid elements

Table 5. Figures of lowest reinforcement (Af) of the piles of the existing building obtained by crossing the information gathered from archive documents and direct surveys, with the 2229/1939 RD norms Section n° 1 2 3 4 5 6 7

Dim a (cm) 30 35 35 30 40 40 35

Dim b (cm) 35 60 40 40 40 50 35

Ac (cm2) 1,050 2,100 1,400 1,200 1,600 2,000 1,225

Afmin (cm2) 8.40 16.80 11.20 9.60 12.80 16.00 9.80

Number of buildings 2,150,529 1,383,815 1,659,829 1,967,957 1,983,206 1,290,502 791,027 11,226,595

8 9 10 11 12 13 14 15

30 30 25 30 70 45 30 25

50 60 35 25 24 30 30 25

1,500 1,800 875 750 1,680 1,350 900 625

12.00 14.40 7.00 6.00 14.40 10.80 7.20 5.00

Table 6. Soil categories and their description Descriptiona Rocky outcrops or very rigid soils, with Vs 30 values ≥ 800 m/s and a maximum alteration layer of 3 m.b B Soft rocks and deposits of very thick coarse-grained soils or very thick finegrained soils, with layer thicknesses more than 30 m and better mechanical qualities with increasing depth. Vs 30 values are between 360 and 800 m/s (i.e., NSPT, 30 > 50 for coarse-grained soils and cU 30 > 250 kPa for fine-grained soils).c C Deposits of medium-thick coarse-grained or fine-grained and on average consistent soils, with layer thicknesses more than 30 m and better mechanical qualities with increasing depth. Vs 30 values are between 360 and 800 m/s (i.e., 15 < NSPT, 30 < 50 for coarse-grained soils and 70 < cU 30 < 250 kPa for fine-grained soils). D Deposits of poorly thickened coarse-grained or fine-grained less[AQ54]consistent soils, with layer thicknesses more than 30 m and better mechanical qualities with increasing depth. Vs 30 values ≤ 180 m/s (i.e., NSPT, 30 < 15 for coarse-grained solis and cU, 30 < 70 kPa for fine-grained soils). E Soils of subsoil types C and D, for thicknesses not exceeding 20 m, placed on the reference substrate (Vs > 800 m/s) Source: Data from NTC (). Category A

aThe

Associated General Contractors.

bThe

Construction Industry Institute.

cThe

US Green Building Council.

Table 7. Topographic categories and related topographic amplification coefficients Topographic category T1

T2 T3

Building location flat surfaces, slopes, and reliefs with an average inclination of ≤ 15° on the top of the slope on the ridge of the relief

ST[AQ55] 1

1,2 1,2

T4 Source: Data from NTC ().

on the ridge of the relief

1,4

Table 8. Parameters referred to the L1 building Parameters Foundation soil Topography category Topographic amplification coefficient

Category E T1

Value Vs 800 m/s —

ST[AQ56]

1,0

Table 9. Independent parameters for the seismic analysis Limit state ag F0[AQ57] Tc SS[AQ58] CC[AQ59] ST[AQ60] q[AQ61]

SLV 0.064 g 2.748 0.356 s 1.6 1.738 1 1.5

Table 10. Dependent parameters Parameter S MU TB TC TD

Value[AQ62] 1.6 0.667 0.206 s 0.619 s 1.855 s

Table 11. Criteria of intervention as related to the construction-related requirements of the addition of floors following verification in a computer environment [AQ63] Operational requirements Limiting the added loads on the existing structure

Criteria of intervention Using light elements Studying the interface between the added floor and the existing building Studying the interface between the added floor and the existing building at the transitional stage Reversibility of the structure

Cutting down installation times

Assessing the position of the barycenter before, during, and after the addition of floors Largely resorting to prefabrication Dry-laid elements

Note: Bold indicates added criteria. AQ1: For affiliation #1, please check that the city, postal code, country, and email are correct. AQ2: For affiliation #2, please check that the city, postal code, and country are correct. AQ3: For affiliation #3, check that the city, postal code, and country are correct. AQ4: For affiliation #4, please check that the city, postal code, and country are correct. AQ5: For affiliation #5, please provide the city, postal code, and country. AQ6: Please reconsider the keyword "Social housing." It only appears once in the body of the manuscript. I added “CLT” to the keyword "Cross-laminated timber" since “CLT” is used throughout. AQ7: Is "XX-century" intention or should there be numbers in place of the XX? AQ8: Should this be referring to Figs. 1(a and b)? There is no "a" or "b" in Fig. 2. AQ9: Please review this change from "upgraded from" to "upgraded to." Does that retain the meaning? AQ10: Is the term "inmates stairwell" correct or should "inmates" be a different word? Please review. AQ11: Please provide the expansion for "DM." AQ12: Please check. The definition in the references uses "per le" instead of "delle." AQ13: Please check the addition of the word "adding" for clarity. Does it keep the meaning intact? AQ14: This sentence was recast for clarity. Please check that the meaning is intact. AQ15: Please check the addition of the word "reviewing." AQ16: Please correct this phrase "seinng-up." The meaning is unclear. AQ17: Please review this sentence to make sure the edits maintained your meaning. AQ18: Please review this sentence to make sure the editing changes keep your meaning intact. AQ19: Please verify whether it's "Territoriale" or "Territoria." In the abstract, at its first mention, the word "Territoriale" is used. AQ20: Should there be a number before "top floor levels" as it is with the "bottom three floor levels"?

Commented [E1]: The author orignally had the added criteria in Table 11 as bold italics. I changed it to bold roman, per journal style.

AQ21: Please correct this unit of measurement "gg." AQ22: Please spell out the expansion for "LC1." AQ23: "FC" was changed to "CF" for confidence factor. Is that okay? AQ24: In this sentence, please define "fck" and "Rck." Also, is the capital intentional in "Rck"? AQ25: Please check this sentence. It was incomplete. The word "allows" was changed to "provides." Does this keep your meaning intact? AQ26: Please check that "72 and 78" are the correct numbers for this unit of measurement. AQ27: Please check that "66 and 68" are the correct numbers for this unit measurement. Also, is it okay that "66" comes before "68"? It was originally in the reverse order. AQ28: Please clarify the meaning of "ad dipendet parameters." AQ29: Please review this sentence to make sure the edits maintain your meaning. AQ30: Please spell out the expansion for "TC." AQ31: Please review Appendix 6. What do "se" and "e" refer to in the first line? Are they correctly placed? Should any of it be in subscript or superscript? Also, please check that the other subscript letters are correct. AQ32: For the book reference (Beretta 1963), please provide the English translation for the title and the publisher name. AQ33: For the book reference (Bertolazzi 2015), please provide the English translation for the title and the publisher name. AQ34: In the book reference (Carlotti 2011), please provide the English translation for the title and check that the publisher location is correct. AQ35: For the book reference (Ferrante 2012), please provide the English translation for the title and check that the publisher location is correct. AQ36: For the book reference (Franchini and Turrini 2012), please provide the English translation for the title and check that the publisher name and location are correct. AQ37: For the book reference (Greechi and Malighetti 2008), please provide the English translation for the title. AQ38: For the book reference (Griffini 1948), please provide the English translation for the title.

AQ39: For the journal reference (Guenzi 1981), please provide the English translation for the article title, the volume number and the DOI/URL. AQ40: For the other reference (NTC 2008), please provide the English translation for the title. AQ41: For the journal reference (Pace 1993), please provide the English translation for the title, the volume number, and the DOI/URL. AQ42: For the url reference (Pearce 2004), please provide the correct URL. AQ43: For the journal reference (Poretti 2007), please provide the English translation for the title, the volume number, and the DOI/URL. AQ44: For the book reference (Ridolfi 1946), please provide the English translation for the title. AQ45: For the url reference (Roadmap to a Resource Efficient Europe 2011), please provide the title of the article and check that the URL is correct. AQ46: The journal reference (Rohracher 2001) is not listed as a text citation. Please either add it in the text or delete it from the reference list. AQ47: In the book reference (Rossini and Segre 1968), please provide the English translation for the title. AQ48: In the book reference (Turrini 2013), please provide the English translation for the title. AQ49: Please review Fig. 17 caption to make sure the subcaptions and labels are correct. AQ50: Is "XX-century" intention or should there be numbers in place of the XX? AQ51: In Table 3, column 3, please provide the unit of measurement. AQ52: In Table 3, column 4, please provide the unit of measurement AQ53: In Table 3, column 5, please provide the unit of measurement AQ54: For Table 6, row 4, "little consistent" was changed to "less consistent," Is that okay? AQ55: The "T" was placed in subscript. Is that correct? AQ56: The "T" was placed in subscript. Is that correct? AQ57: In Table 9, row 2, please provide unit of measurement. Also, is the “0” supposed to be a subscript? AQ58: In Table 9, row 4, please provide unit of measurement.

AQ59: In Table 9, row 5, please provide unit of measurement. AQ60: In Table 9, row 6, please provide unit of measurement. Also, is the “T” supposed to be in subscript? AQ61: In Table 9, row 7, please provide unit of measurement. AQ62: In Table 10, under the "Value" column, please provide the unit of measurement. AQ63: Please provide the text citation for Table 11.