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The present study has as its main objective, the search and development for a model of evaluation and diagnosis of the origins of pathologies, in a rehabilitation process of architectural heritage that allows possible corrective measures to be applied at an early stage of appreciation, defining rigorously the reinforcement and consolidation options necessary to improve the overall construction performance. Understanding the original tectonics of the building, becomes essential for a conscious and adequate performance decision-making in an intervention that is desirable to be minimal and not intrusive, facilitating the optimization of solutions depending on the state of conservation in which the building is. Historical and morphological characteristics of the construction were considered, in order to define and study the best solutions for an appropriate intervention. The proposal for structural stabilization, from the perspective of greater sustainability, observes all the requirements and recommendations of the international charters on heritage rehabilitation - in addition to national legislation, the contemporary intervention principles, guaranteeing the safeguarding of its identity.
*Address all correspondence to: cmfrancopt@gmail.com
1. Introduction
Taking advantage of a case study that was once carried out on a building in the entire state of neglect, for its research and its unequivocal architectural value, with a view to transmitting the scientific and technological knowledge and consequent endogenization then acquired, all the information collected was compiled. to the date and before the intervention in the meantime, including photographic records already in the initial phase of the work.
The work presented here aims to establish an intervention methodology - in an approach directed to the evaluation of the structural system, defining as a priority the global stabilization of the building.
The prior assessment of the building’s state of conservation, through the on-site observation of pathologies and anomalies caused by years of neglect, makes it possible to define an appropriate concept for structural stabilization, which may be replicated in similar buildings, not only in Portugal as well as in any part of the world where there are examples of recognized architectural interest, favoring the adoption of less intrusive solutions, betting on the recovery and rehabilitation of materials and traditional construction techniques that are part of the set of cultural values materialized in the building, where adaptation to the new regulatory requirements for use and structural performance, constitutes an additional challenge to which it is intended to respond, in order to satisfy the requirements of comfort, functional efficiency and sustainability.
Prior to interventions in classified Architectural Heritage and in the design phase, not only the applicable national legislation should be considered, but also the letters and recommendations, criteria and international standards on the protection of Architectural Heritage.
The studies and projects for the works of conservation, modification, reintegration and restoration in classified properties, or in the process of being classified, will have to be elaborated and subscribed by technicians of legally recognized qualification or under their direct responsibility, for which the works or interventions, will be subject to authorization and monitoring by the competent authorities for the final decision of the classification procedure.
Portuguese legislation establishes the bases of the policy and regime for the protection and enhancement of cultural heritage - Law n° 107/2001 of 8 September, in conjunction with Decree-Law n° 308/2009 of 23 October, defining the concepts, rights and duties of the owners of heritage with relevant cultural interest, namely architectural, with values of memory, antiquity, authenticity, originality, rarity, uniqueness or exemplarity, being a fundamental task of the State and duty of citizens, their protection and enhancement [1].
“The houses that are capable of proposing this decisive encounter are, without any doubt, great architecture. AND, like all successful models, they have a broad and mixed ancestry where art permanently intersectswith the life(s), which is another noble functionof architecture” [2].
The case study presented evaluates an important 19th-century example of private housing construction – Casa Sommer (Figure 1), in the heart of the historic center of Cascais, Portugal, simultaneously combining two trends - romantic and neoclassical, two most relevant stylistic currents at the international level of the 19th century.
Figure 1.
Casa Sommer – 3 D model (Geostar, levantamentos arquitetónicos).
As main characteristics of this type of architecture, it stands out its orthogonal lines, the regular, geometric and symmetrical shapes as well as the columned portico. Consisting of an almost quadrangular plan (10.24x11.73 m), with three overlapping floors, with an approximate area of 132.00 m2 per floor, shown externally on the facades through cornices that form architraves. Its verticality is assumed by the elevation of 2.60 m of the noble floor in relation to the street, imposing itself in this way on the public square.
The vertical communication between the different floors is ensured by the staircase strategically placed under the transversal axis of the building, in which the openings in the east façade ensure the natural lighting and ventilation of the interior space. The portico of columns with a square shaft, based on a square base, supporting the porch balustrade in stone, imposes the main entrance of the House.
The building was built from an almost quadrangular base (10.24x11.73 m), a geometry that gives it favorable performance in terms of seismic behavior. The outer walls were built in irregular masonry of two-piece stone, cut out on both sides and with horizontal paneled orientation, of the type of masonry with mortar joints, filling the inner core with smaller stones [3]. In this constructive typology, the stones are laid on top of each other - in a joint forest, wrapped in lime and sand mortar - usually at the time with a 1: 2 line, in which ceramic shards and stone frames are transversely inserted in order to fill the gaps. Empty spaces, giving not only better adherence of the elements but also allowing the execution of regular beds for the laying of successive layers.
The walls are supported by direct foundations, in a simple extension of them with widening already in the ground, of identical constructive composition. The thickness of the wall is variable: 0.75 m from the foundations to the level of the landing of the front staircase; 0.65 m from this level to the threshold of Floor 2; 0.60 m in the outer envelope of Floors 2 and 3.
The start of the cornerstones in the form of pilasters, aims to increase their area of contact with the terrain and consequently an improvement in the distribution of loads, takes on a projection resulting from the difference of its base geometry of 1.00x1.00 m, from the foundations to dimension of the level of the frontal staircase, from here it is reduced to 0.80x0.80 m. It was common for lime mortar to be applied to the plaster 1: 3.
The renders were executed in successive layers, thus managing to minimize the cyclical effects of the contractions / expansions to which the different materials are subjected, considerably increasing the durability of the work as a whole. The interior walls of the Ground Floor (Figure 2), are also made of irregular stone masonry, completely identical to the typology of the exterior walls, with the exception of the thickness which is 0.40 m thick, forming the start of the stairwell and the support of the walls of the axial corridor of the house, give the necessary stiffness to the general foundation of the building.
Figure 2.
Structural walls.
The interior walls in wooden partition (Figure 3) of the remaining floors have not only the usefulness of compartmentalization of spaces but also the function of structural locking of the building “in the old buildings they almost always play a structural function of relief, since the building itself the architecture of the buildings, the organization of the spaces and the structural limitations of the available elements cause the resistant capacity of most of the walls to be mobilized“[4].
Figure 3.
Wood partition wall structure.
The partitions made up of a structure made of wooden cones, in a set of vertical, horizontal and diagonal pieces - crosses of St°. André (Figure 3), carved and nailed so as to allow them to fit simultaneously with each other and with the braces, establishing the connection to the floors. The horizontal lath of trapezoidal section, also in a little house, serves as a support for the plastering of weak sand mortar and aerial lime, whose usual feature at the time was 1: 3, (weak retraction and weak mechanical resistance, giving good adhesion to the base and good workability) [5].
3.2 Floors
The structure of the pavements of the raised floors is composed of elements in white wood, applied in the form of Portuguese-style flooring, with a thickness of 0.03 m and a variable width (0.12 / 0.15 m), resting on beams with 0.17x0.08 m arranged in the direction of the smallest span, built into the outer walls, with a distance of 0.36 m from each other (Figure 4).
Figure 4.
In situ survey of the wooden floor structure.
3.3 Roofs
The roof is made of white cone wood, with symmetrical hipped roof, with a structure made up of two trusses, fixed to the crevice existing in its perimeter, interconnected by bars and slats to support the ceramic tiles (Figure 5).
Figure 5.
Wooden structure of the roof.
The structural typology of the roof, together with devices for connection to the exterior walls, using metal parts called bolts (Figure 6), anchored on the outer side of the wall, in the transverse direction of the beams, as a whole guarantees the necessary bracing of the building [6].
To determine the level of conservation, while visiting the building under analysis, based on the inspection of visible anomalies according to the evaluation criteria and rules contained in the Evaluation Form developed by LNEC, in the framework of the preparation of the NRAU. The National Laboratory of Civil Engineering (LNEC) thus conceived the method of assessing the state of conservation of buildings (MAEC) which aims to determine with rigor, objectivity and transparency the state of conservation of buildings and the existence of basic infrastructures., which is completed in Appendix 1, approved by Decree No. 1192-B / 2006 of 3 November, published in the Diário da República, 1st series— No. 212—3 November 2006, integrating the relevant elements to determine the level of conservation, under the terms of paragraph 2 of article 33 of Law no. 6/2006, of 27 February, which approved the New Urban Lease Regime (NRAU).
The ordinance establishes the general assessment criteria in number 1 of Article 3: The assessment of the level of anomaly that affects each functional element is carried out by combining the following four criteria:
Consequence of the anomaly in satisfying functional requirements;
Type and extent of work required to correct the anomaly;
Relevance of the locations affected by the anomaly;
Existence of an alternative for the affected space or equipment.
Total das ponderações atribuídas aos elementos aplicáveis
61
Índice de anomalias
2.51
AVALIAÇÃO
Com base na observação das condições presentes e visiveis e nos termos do artigo 6° da Portaria n.° 1192-B/2006, declaro que:
Estado de conservação do locado:
Mau
Estado de conservação dos elementos funcionais 1 a 17:
Médio
Calcular
Grave risco para a saúde:
☑
Table 1.
Results of the evaluation form.
In the presence of classified heritage, a strategy based on an “observational approach” should be chosen, however, assiduous verification is guaranteed during the course of the intervention, the effectiveness of the measures corrective measures to be proposed in order to guarantee the necessary adjustments in face of the reality that will be found on site [7].
The main anomalies found in the survey carried out on the building, with special concern for the structural state of the construction, should be pointed out on the designed parts, previously prepared for the purpose - plans, section and elevations, which may be considered an undisputed target for correction and / or Repair.
The evaluation of crack openings was based on the lessons of classes given by the late Professor Doctor Architect António de Santa Rita, as it is considered a simple and objective method, therefore suitable for this type of analysis.
Cracks in masonry walls are classified according to related criteria, with the size of the opening, the activity, the shape, the causes, the direction.
The classification of cracks, according to their respective causes, is perhaps the most suitable method for studying these pathologies, as the solutions to the problem will be defined from this analysis.
Based on what is described in the crack classifications, the basis for cataloging the typical configurations of cracks in masonry was elaborated, registering its location on the elevations of the building.
South wall: cracks of considerable openings, caused by the foundation of the southeast corner foundation, as a result of a greater traction effort in the west / east direction, which should deserve special attention in the intervention proposal (Figure 7).
Figure 7.
South facade with crack location.
Fissures F1, F2, F3, F4 (Figure 8), F5 (Figure 9), F6, F7 and F8 are thus considered as wide cracks, whose activity needs to be monitored, with diagonal orientation of causes related to the laying of foundations.
In order to systematize the information collected in situ, a List of Pathologies was elaborated, based on the studies of Pathologies of buildings carried out by the Laboratory of Physics of Constructions (LFC) of the Faculty of Engineering of the University of Porto (FEUP) in collaboration with the Group of Construction Pathology Studies - PATORREB. Grouped in a set of Pathology Cards (Annex 2), where they describe not only the problems found, but also their main causes, methods of evaluation and possible solutions for intervention.
For a better interpretation and an adequate diagnosis, it will be necessary the records, elaborated during the previous inspection carried out to the building, expressed on the elevations and plans, of the pathologies found not only in its exterior surroundings but also in its interior space (Figures 10 and 11).
Figure 10.
Record on the pathology plan.
Figure 11.
Register of pathologies on the nascent facade.
In addition to the inspection carried out, the complementary photographic record becomes essential for an illuminating reading of the situation found during the evaluation. A complete photographic survey of each facade should then be presented, focusing on the main existing anomalies.
The pavement in contact with the ground has a high degree of humidity as a result of the deficiency or absence of an adequate imperialization, consequently allowing the direct entry of rainwater into the interior space, causing damage directly to the pavements and baseboards and, furthermore, by capillarity, causing blistering and plaster breakdown.
The slab of the 2nd floor terrace, which is supported by the entrance porch, is aggravated in addition to anomalies similar to those detected in the kitchen slab, due to its exposure to the aggressive external environment.
These pathologies result from depassivation corrosion of the metallic structure, in a reaction induced by carbonation, due to the presence of a structure with environmental exposure to air and humidity (Figure 12) caused by marine salt water chlorides, transported by air as it is close to the sea.
Figure 12.
Corrosion of metallic elements.
According to the classification of Standard NP EN 206–1: 2007 (Environmental Management Study Notes - Specification, Performance, Production and Compliance), which establishes aspects related to concrete, namely the specification and performance in accordance with environmental exposure, taking into account one of the main factors of attack on concrete containing reinforcement or with metallic elements:
Attack on armor or other embedded metals (corrosion induced by carbonation or chloride ions).
Due to its location, the building that was the object of study, we can attribute Class XC 3 to corrosion induced by carbonation, and also Class XS1 to corrosion induced by marine chlorides of salts originating in salt water, from sea water, transported by air, as it is close to the sea.
Floor 2 and Floor 3 - floors and support structure in the areas of the sanitary facilities are rotten, an anomaly caused by ruptures in the water and / or sewage systems, highlighting the fact that it is on the floor which facilitated the collapse of the adjoining floor ceiling (Figures 13 and 14).
“utilitas, venustas e firmitas”, Vitrúvius (1st century BC): Its standards of proportions and its conceptual principles - utility, beauty and solidity.
Since antiquity, although restricted to a limited territory from Roman times, there are registers of regulatory norms on heritage protection: Decree of about the year 44 AD, discovered in the historic city of Herculano, Italy - forcing anyone to demolish a building for speculative purposes to pay the authorities twice the purchase price. During the period of the Roman empire, an Edict dated 17 July of the year 389 appears - “It is forbidden to disfigure the exterior ornaments of private buildings with modern additions and damage the historic buildings of an important city for reasons of greed, for the sake of profit”.
Pope Gregory I (590–604) proposes and practices a policy of reusing the immense Roman legacy abandoned after fall of the western Roman Empire. The great patrician domus are turned into monasteries, their halls of reception in churches. He warns his missionaries not to destroy the pagan temples and buildings, but rather by the otherwise they must be preserved and prepared and properly adapted - placing their altars and their relics, for Christian worship [8].
Eurocode EC 8, part 3 - “Assessment and rehabilitation of buildings”, establishes the criteria for assessing the seismic performance of existing buildings, describing the approach regarding the corrective measures to be taken. It also establishes criteria for measures to repair and / or reinforce structural elements in the design and final dimensioning of the new elements to be introduced and their necessary connections to the original structural system.
The structural elements in wood, together with the masonry, are of equal importance for the stability of the building. Due to its great vulnerability to deterioration agents and in view of the need to adapt the construction to the new uses and safety criteria currently required, it is absolutely necessary to provide for an adequate intervention, aiming at increasing the resistance of the deteriorated element, either through its reinforcement using new materials and / or by reconstructing the section with anomalies, using the same material - with or without connecting elements [9].
Using a basic model that intends to represent the genesis of structures designed by man, an attempt was made to conceive an Archetype, which in a simple and schematic way summarizes the structure of the study.
Prostheses introduction - shown in black in the photograph, for the damaged sections of the element: Type A repair: in its lower support (Figure 15); Type B repair: on its upper support (Figure 16); Type C repair: wherever there is an anomaly (Figure 17); Type D repair: integral replacement of the element (Figure 18).
Knowing and understanding the structural concept of pre-existence, the materials and construction systems that compose it, in an approach and collection of information about the object, through the performance of visual inspections, soundings and / or tests that may be deemed necessary, will contribute to the design of a conscious intervention, sustained in the domain of knowledge resulting from a careful assessment of its pathologies and its causes.
The rehabilitation of masonry walls and wooden structural elements, due to the importance of their structural function in old buildings, is the object of most of the study and, consequently, of greater concern in the elaboration of intervention proposals. Notwithstanding the techniques to be adopted are classified as not very intrusive, they allow to achieve the intended objectives, without causing changes in the original structural scheme and in the various constituent preexisting structural elements.
The increase in the strength of masonry can be achieved relatively easily through reinforcement by confinement, by adding a new material (composites, mesh, sheets or metal profiles). The wooden structure must be preserved by the reconstitution / repositioning of the element with the same material and / or material different from the original, or by the insertion of new structural elements, whose resistance can be mobilized in order to transfer the loads between the structure to be reinforced. and that new element.
The great challenge will be to guarantee the improvement of the building’s overall behavior, as a result of the careful repair / replacement of masonry and structural wood, reestablishing its structural functions now reinforced by the intervention. We tried to develop an intelligible model, from which it is intended to expose the concept of the intervention that is defended.
References
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