Managing Intervention Works for Conservation and Revitalization: A Case Study of the Bârnova Monastery, Iași

Abstract

This study offers insights into the management of intervention works aimed at conserving and revitalizing historical structures, focusing on the Bârnova Monastery in Iași, Romania. The study begins by contextualizing the broader challenges associated with preserving heritage churches and monastic buildings, elucidating the architectural characteristics and structural aspects typical of traditional Romanian Orthodox churches. Subsequently, the study delves into a detailed case analysis centered on the restoration of the medieval Bârnova Monastery, particularly its paramount structure, the Saint George Church, erected in the XVII century. This church exemplifies the traditional Orthodox architectural and structural norms prevalent during the medieval period. Through a structural diagnosis, the study identifies the vulnerabilities of the Saint George Church, which have been exacerbated by the impact of approximately 24 earthquakes of magnitudes exceeding 6.0 throughout its history. In response, a multifaceted approach to strengthening was devised, involving a combination of grouting and the installation of steel rods within vertically drilled galleries spanning the entire height of the walls. The adoption of this integrated strengthening strategy proved advantageous, significantly enhancing the seismic resilience of the church while simultaneously addressing the preservation needs of its historical features. This case study not only contributes to the body of knowledge on conservation and revitalization practices but also offers valuable insights into the effective management of intervention works for safeguarding heritage structures against seismic risks.

1. Introduction

Cultural and religious heritage structures serve as tangible records of our collective human past, embodying centuries of architectural ingenuity and societal development. Yet, the conservation and management of these invaluable assets’ present formidable challenges, particularly when confronting historical edifices characterized by incomplete archival data and intricate architectural narratives [1,2,3,4]. As technology progresses, novel solutions have arisen to confront these challenges and facilitate the stewardship and conservation of historical treasures. Conservation entails the active upkeep and management of a structure or space to ensure its enduring existence [5,6,7]. Diverging from preservation, conservation acknowledges the potential necessity for adaptive changes to accommodate contemporary needs and structural requirements while honoring its historical significance [8,9,10]. The overarching goal of conservation is to strike a delicate equilibrium between safeguarding the original “essence” of the structure and enabling practical functionality.

Central to conservation endeavors are routine inspections, maintenance routines, and reparative interventions designed to thwart the encroachment of decay. This methodology is underpinned by a commitment to sustainable resource utilization, incorporating energy-efficient technologies, and enhancing the overall functionality of the building. Moreover, conservation efforts entail addressing structural deficiencies to ensure the safety and stability of the edifice, thereby extending its lifespan and bolstering the sustainability of the built environment [11,12,13,14]. In line with European directives, including the Communication from the Commission “Towards an integrated approach to cultural heritage for Europe” (2014), and the Council of Europe European Heritage Strategy for the 21st Century (2017), there exists a pressing imperative to reorient cultural heritage policies, positioning them as focal points within an integrated framework that prioritizes conservation, protection, and promotion by society as a whole [15]. This collective responsibility encompasses both national authorities and local communities, recognizing cultural heritage as a shared resource and a common good vulnerable to neglect and deterioration without concerted efforts towards its preservation.

Romania, through initiatives such as the “National Heritage Buildings Catalogue—Year 172 (XVI)—No. 646 bis.”, exemplifies a commitment to heritage conservation, with numerous churches and monastic complexes delineated as sites of exceptional religious, cultural, and social significance [16]. Within this context, prioritizing structural diagnosis, and strengthening interventions across the ecclesiastical portfolio emerges as a requisite measure to avert cultural heritage losses, mitigate maintenance expenses, and safeguard human lives. This holistic approach underscores the intrinsic value of cultural heritage as a reservoir of shared memory and a catalyst for societal cohesion, underscoring the imperative for sustained conservation efforts underpinned by principles of sustainability and innovation.

The seismic vulnerability inherent in aged masonry churches has been extensively scrutinized and delineated across various scholarly works [17,18,19,20,21,22,23,24]. Their inadequate structural performance primarily stems from the characteristic architectural configurations and geometrical attributes, compounded by the limited tensile strength of masonry, rendering them susceptible to out-of-plane loading, alongside a dearth of adequately rigid components in horizontal orientations, which may exacerbate what is commonly referred to as “box behavior” within the structure. Within Romania, several methodologies for strengthening these structures have been widely employed, including the “framing system” technique [25,26], entailing the envelopment of structural masonry elements within a newly reinforced concrete framework, reinforcement via metallic/composite elements [27,28,29,30,31], application of mortar jacketing, structural repointing of masonry components [32], implementation of base isolation methods [33], and deployment of vertical steel rods (occasionally post-tensioned) within drilled galleries traversing the entirety of masonry walls [34].

The selection of an appropriate strengthening methodology from the aforementioned repertoire necessitates meticulous consideration of numerous factors, including the age and current condition of the structure, the materials employed in its construction, the desired outcomes of the intervention, and the available financial resources. The objective of the present research endeavor was to furnish insights into the structural evaluation and rehabilitative strategies employed in the restoration of a medieval heritage church situated in Bârnova, Iași, Romania. Founded by the Moldavian ruler Miron Barnovschi-Movilă (1626–1629, 1633), from whom it derives its name, and subsequently completed under the reign of Eustratie Dabija (1661–1666), the church serves as the focal point of a substantial monastic complex [35].

Throughout its storied history, this heritage edifice has weathered numerous trials, including seismic disturbances and invasions, yet it has endured, retaining its significance as a bastion of spirituality, enlightenment, and cultural enrichment within the community.

2. The Church of Saint George of the Bârnova Monastery

The Bârnova Monastery is a monk monastery situated near the city of Iasi, amidst the forests of the Central Moldavian Plateau, beneath Pietrăriei Hill, in the commune of Bârnova. The monastery was founded by the ruler of Moldavia, Miron Barnovschi-Movila (1626–1629, 1633), from whom it derives its name, although the construction works were completed under the reign of the ruler Eustratie Dabija (1661–1666).

The church boasts a magnificent exterior appearance, constructed in the Galata style, featuring a triconch plan with two domes: one massive dome above the narthex and another slimmer, octagonal dome adorned externally (Figure 1). For the first time in Moldavia, the churches of Miron Barnoschi-Movilă feature a bell tower attached to the church, positioned above the narthex. This addition alters and enriches the overall exterior appearance of the church. The tower above the narthex serves a defensive purpose, with a hidden chamber on the first floor where church valuables could be concealed in times of peril, and a second-floor room equipped for defense, featuring arrow slits in the walls for firearm use. Access to this tower is through a secret door, concealed in the era by the steward of a choir stall in the narthex. Additionally, the presence of massive lateral buttresses on the corners of the narthex is also notable [36].

The church of the Bârnova Monastery is divided, following the Byzantine tradition, into the narthex, nave, and altar. From a religious perspective, the latter represents the mystical and timeless manifestation of the divine throne of God. The narthex is rectangular, supported externally at the corners by massive buttresses. Inside, it features a vault with two domes, adorned all around with embossed twists and small shields. The narthex resembles that of the Dragomirna Monastery but with simpler vaults and lacking the lavish ornamentation of Anastasie Crimca’s foundation [37,38]. The partition wall between the narthex and nave is absent, replaced by three arches and two thick pillars, representing one of the architectural characteristics of 17th-century Moldavian church architecture, with the prototype of this new division first found at the Galata Monastery. The nave has the peculiarity of transmitting the weight of the dome onto the side walls through transverse arches, similar to the Dragomirna Monastery. However, it lacks the ribs adorned with twists, as well as the intersecting arches of the vault. A large iconostasis separates the nave from the Altar. The church of the Bârnova Monastery is not painted.

The structural framework of the church comprises load-bearing walls constructed of stone and brick masonry. The thickness of the structural walls varies between 0.40 and 2.00 m. The floors (vaults) are constructed of brick masonry in a dome shape. The roof structure is made of pine wood, supported by the structural walls, and consists of rafters, ridge beams, purlins, braces, eaves and decking. The roofing material is metal sheeting. The building has a basement plus ground floor height regime.

According to the geotechnical study, the soil stratification is as follows: a brown vegetative soil layer with a thickness of 0.50 m, followed by a yellow dusty clay with high plasticity in a dense plastic state, interspersed with limestone, with a thickness of 1.90 m. This is succeeded by a yellow clay with high plasticity in a dense plastic state, with centimeter-sized gravel intercalations, with a thickness of 1.60 m. Next is a densely packed, reddish, shell-bearing, fine sand layer, with a thickness of 0.40 m. Following this is a yellow-grey fatty clay with brown zones, containing shell intrusions and exhibiting very high plasticity in a dense plastic state, extending beneath the investigated area. Six boreholes were made for this study, and the thicknesses of the layers differ between them. Groundwater was intercepted at depths of −7.20 m in borehole F1, −4.50 m in borehole F2, −4.00 m in borehole F3, −4.90 m in borehole F5, and −4.50 m in borehole F6. The bearing capacity of the soil, according to the geotechnical study, is P_critical = 270 kPa. The foundations of the structures are made of stone masonry, and the soil on which they are founded is a yellow-brown, densely plastic dusty clay.

3. Structural Diagnosis

3.1. Visual Investigation

The degradations observed during the visual inspection consisted of weathered stone and bricks due to exposure to rain, freezing, and thawing on all exterior walls. In the altar area, fissures were noticed around the extended window opening towards the vault keystone, as well as below windows. In the nave, displacements were identified between the chimney and the arch in the wall (Figure 2b), as well as fissures in the masonry of the apses. In the narthex, cracks were identified in the masonry above the entrance extending into the narthex vault (Figure 2c), cracks above windows, below windows, as well as fractures of the buttresses at the point of contact with the exterior walls (Figure 2d).

As depicted in Figure 1e,f the cracks appeared in the most vulnerable sections of the structure, affecting both horizontal and vertical elements. Furthermore, the pattern of cracking aligns with the typical modes of damage or failure observed in Orthodox churches. The structural deficiencies were evidenced by a continuous longitudinal fracture, originating from the porch and extending to the altar (Figure 2a), resulting in the division of the nave into two sections. Similarly, the occurrence of multiple transverse fractures in the upper regions (the less rigid areas) of the altar, nave, narthex, and porch indicated further subdivision of the structure into multiple segments. Additionally, there was an observed tendency for separation between the porch and the narthex, as evidenced by the ongoing development of cracks in the longitudinal walls.

In the case of the Church of Saint George, it was observed that the uncontrolled presence of water poses a significant threat to the preservation of heritage assets, a concern that has persisted throughout architectural history [39,40]. Specifically, water infiltration from the ground via capillary action, facilitated by the porous nature of the stones and mortar, was noted (see Figure 3). This phenomenon, commonly referred to as rising damp, is widely recognized as detrimental to porous materials, as it can exacerbate frost-induced damage and render them susceptible to additional degradation mechanisms, including biological growth and wind erosion [41,42]. Through visual inspection, it is obvious that the church was profoundly affected by rising damp, manifesting in at least two common degradation patterns on the external walls: discoloration (darkening) (see Figure 3a) and efflorescence (see Figure 3b).

3.2. Structural Analysis

The monastery is located in Romania, in the Iași County, in the village of Bârnova, situated 7 km away from the city of Iași, and it currently enjoys both local and overall stability under current conditions.

As per the CR1-1-3/2012 Norm, the snow load zone imposes values of 2.5 kN/m² with a mean recurrence interval of 50 years [43]. Concurrently, the wind load zone, in accordance with the CR1-1-4/2012 Norm, exerts a reference wind pressure of 0.7 kPa at a height of 10 m [44]. These load zones are pertinent to Climatic Zone IV, characterized by temperatures as low as −18 degrees Celsius. Such climatic and load considerations are crucial for ensuring structural integrity and resilience against environmental factors in the designated area.

According to the technical expertise and archival documents of the monastery, the Church of Saint George has endured earthquakes in the following years: 1637, 1650, 1679, 1681, 1701, 1721, 1738, 1778, 1790, 1793, 1802, 1829, 1838, 1868, 1880, 1894, 1908, 1912, 1934, 1940, 1945, 1977, 1986, and 1990. Although there is no strict proportionality between the Mercalli scale and the Richter scale, by correlating the documented destruction with seismic events, we can conclude that all these earthquakes had a magnitude exceeding 6.

Seismic analysis was conducted in accordance with the Romanian standard P100-3/2019, utilizing an average reference return period of 100 years [45]. While Eurocode 8 provides a comprehensive framework for seismic design applicable across Europe, the P100 norm is specifically tailored to address the unique seismicity of Romania. The Vrancea seismic zone, characterized by its frequent and intense intermediate-depth earthquakes, necessitates a specialized approach that is accurately reflected in the P100 standards. The design peak ground acceleration (PGA) was specified as 0.20 g, with a corner period (Tc) of 0.7 s [45]. Eurocode 8 uses a two-parameter model, including the soil factor (S) and damping correction factor (η), to modify the spectral shape based on local soil conditions and different damping ratios. On the other hand, P100 simplifies this by using the dynamic amplification factor (βo) for all spectra, set at 2.5, and includes modifications in the long-period range to account for the specific seismic characteristics of Romania without the need for additional soil or damping factors.

A behavior factor (q) of 1.5 was adopted, which is deemed suitable for heritage buildings constructed of unreinforced masonry, while an importance factor (ɣ_I) of 1.2 was applied. The normalized elastic response spectrum (β) was determined to be 2.75, with damping (ξ) set at 8%, based on the seismic response of the structure and the specific characteristics of the seismic input.

As per the guidelines outlined in the Romanian standard P100/3-2019, the seismic risk classifications for existing buildings are determined through the assessment of index R₃, which denotes the corresponding structural seismic safety level [45]. In the case of masonry structures, R₃ is quantified as the ratio between the aggregate shear capacities of the structural walls and the aggregate effective shear loads induced by seismic activity, as expressed by Equation (1) in the standard.

$$R_{3i}=\frac{S_{cap,i}}{F_{b,i}}$$

(1)

where:

• S_cap,i is the shear capacity of the structural wall “i”, based on the characteristic failure mode;
• $S_{cap,i}=V_{f1} or V_{f2}$;
• $V_{f1}=\frac{N_d}{c_p{\lambda }_p}{\nu }_d(1-1.15{\nu }_d)$— shear force associated for eccentric compression failure of an unreinforced masonry wall subjected to the design axial force;
• ${\lambda }_p=\frac{H_p}{l_w}$—shape factor;
• $H_p$—height of the wall;
• $l_w$—length of the wall;
• $c_p$—coefficient that accounts for the bearing conditions (1 for clamped wall, 2 for cantilever wall);
• ${\sigma }_0=\frac{N_d}{t{l}_w}$—compressive stress corresponding to the design axial force;
• $t$—thickness of the wall;
• ${\nu }_d=\frac{{\sigma }_0}{f_d}$;
• $f_d$—design compressive strength;
• $V_{f2}=\min (V_{f21}, V_{f22})$—shear capacity of the unreinforced masonry wall;
• $V_{f21}=f_{vd}D\prime t$—design shear force corresponding to the failure by sliding in mortar joints;
• D′—length of the compressed region of the wall;
• $f_{vd}$—shear strength associated with failure by sliding in mortar joints;
• $V_{f22}=\frac{{tl}_w{f}_{td}}{b}\sqrt{1+\frac{{\sigma }_0}{f_{td}}}$—design shear force corresponding to failure by diagonal fracture;
• $1.00\le b={\lambda }_p \le 1.5$;
• $f_{td}$—design tensile strength;
• F_b,i is the shear load produced by the seismic action to the structural wall “i”;
• $F_{b,i}=\frac{G_i}{{\sum G}_i}{F}_b$;
• G_i is the mass of the structural wall “i”;
• ΣG_i is the mass of the whole building.

The compressive strength of the stone (70.620 N/mm²) was assessed by testing five cylindrical specimens, with diameters between 69 and 74 mm and heights ranging from 52 to 57 mm. These specimens were meticulously extracted from the uppermost section of the stone walls, and their geometrical configurations, as specified in [46], were achieved using water-jet cutting techniques. The load was applied to smooth, flat surfaces, which were prepared to eliminate any abrupt irregularities. No mortar capping was required, as the tolerances were within the limits set by the standard [46].

The compressive strength of the bricks (5.547 N/mm²) was evaluated by testing five specimens taken from the topmost part of the church tower, following the procedures outlined in [47]. Due to the inability to extract whole brick specimens, the compressive strength was calculated based on the area of the partial brick specimens.

The compressive strength of the mortar (1.071 N/mm²) was determined by testing five mortar joint specimens extracted from the stone walls, in accordance with the provisions of [48]. The thickness of the extracted joints varied between 31 and 44 mm, and the densities of the specimens ranged from 1591 to 1633 kg/m³.

The structural seismic safety assessment of the church revealed a safety level of 34% in the transverse direction and 41% in the longitudinal direction, thereby categorizing the church into the first seismic risk class. These values were determined without taking into account the existing structural degradations. This classification is of utmost concern as it signifies a high risk of imminent collapse.

4. Conservation and Restoration of Saint George Church

Considering the imminent collapse identified during the technical assessment, it was decided to carry out urgent works aimed at conserving, restoring, and revitalizing the Church of Saint George. These works included:

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the installation of vertical tie rods starting from the foundation level;

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natural hydraulic lime-based (NHL 5 mortar) grouting into the stone masonry at the foundation level;

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natural hydraulic lime-based (NHL 5 mortar) grouting of brick masonry to repair brick connections;

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construction of RC girders at the cornice level with transverse connections at the level of the existing arches;

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installation of RC girders only on the exterior of the tower in the attic, with the insertion of vertical tie rods connecting the girders from the base of the tower to its cornice;

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natural hydraulic lime-based (NHL 5 mortar) grouting of all cracks in the stone and brick masonry to repair connections;

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inspection of all timber roof elements and replacement of those inadequate;

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cessation of dampness and protection against moisture with a hydrophobic solution grouted into the stone masonry at the foundation and at its contact surface with the soil.

Ternary grouting, based on natural hydraulic lime (NHL 5 mortar), was employed on the stone/brick masonry walls and foundation to restore uniform strength, continuity, cohesion and compactness, while preserving the morphological characteristics of these elements. Previous research indicates that grouting with an injectable mixture is among the most proper techniques for structural rehabilitation of stone masonry heritage buildings [49]. Experimental evidence suggests that a properly formulated mixture can effectively fill even the smallest cracks (approximately 0.20–0.30 mm) and voids.

The lime mixture used for grouting had a fluidity of 15 s, determined with the standard flow cone, and sedimentation was below 15 mL. The grouting system consisted of: an air compressor, a drill equipped with a drill bit, a mixer for preparing the mixture, a mechanical injection pump, and a standard flow cone. Before proceeding with the grouting along the entire length of the cracks and on both faces of the masonry, the plaster was removed, and areas with displaced or shattered bricks were rearranged through resetting (Figure 4a). The mortar joints of the masonry were deepened and cleaned to a depth of 3–4 cm. Along the path of the cracks, holes were drilled with a depth of at least 1/2 of the wall thickness, spaced approximately 30 cm apart (Figure 4b). In these holes, PVC (polyvinyl chloride) studs of about 70 mm in length with an outer diameter of 13 mm and an inner diameter of 12 mm were inserted. After checking the studs and removing impurities, water was introduced approximately 30 min before grouting to moisten the masonry, verify the quality of sealing, and ensure the continuity of the crack path. The grouting mixture was prepared in quantities that can be used within a maximum of one hour. Drawing upon the expertise of site supervisors and experts, the grout was injected through the PVC nozzles at a nearly constant pressure of 3 bar, as informed by past experiences [22].

To halt capillary water transport, at the foundation level and along all masonry plinths on both sides of the structure, the grouting was also conducted using a hydrophobic mixture. This hydrophobic material consisted of a 10% waterproofing product, and it was mixed up with the lime mortar grout [50].

For the installation of the vertical tie rods, it was necessary in the first stage to construct anchoring pads for the tie rods within the stone masonry at the foundation of the church (Figure 5). These pads intersected with the channels prepared for the vertical tie rods in the area of their anchoring. Concrete was poured into the prepared channels to ensure a continuous connection around each zone (narthex, nave, altar), with care taken to achieve a continuous bond. Additionally, to maintain continuity, concrete pouring was conducted continuously in each region.

The dismantling of the masonry in the regions of the girders, on the exterior walls, was carried out by removing brick by brick until the lower level of the reinforced concrete girder was reached. Holes were drilled with a core drill for vertical ties and horizontal connectors. The holes for anchoring the girders were made at intervals of 50–60 cm along their length. All hole surfaces were thoroughly brushed with a wire brush. Subsequently, the holes were cleaned with compressed air jets and washed with high-pressure water jets. Figure 6 illustrates the configurations of the reinforced concrete girders (highlighted in blue) and the connections between them and the vertical steel rods (highlighted in red).

The slots for the tower girders were made at the specified levels in the project (Figure 7 and Figure 8). For anchoring the girders in the exterior walls, PC52 connectors of ø10 were installed at maximum intervals of 60 cm. Similarly, after the slots were made, the surface was cleaned with wire brushes, compressed air jets, and high-pressure water jets. The casings and bars of the tie rods were inserted into the slots/galleries and injected with micro-concrete until filled. The concrete works were carried out only after the qualitative acceptance of the formwork and reinforcement works, as well as after ensuring the conditions for the normal progress of the works, according to the indications provided in the technical expertise and tender book.

After the reinforced concrete girders were completed, work commenced on the timber structural elements. The actual execution was carried out by sequentially dismantling a specific area and removing and replacing the deteriorated elements with high-quality timber elements previously treated against fungi and fire.

In the case of intervention works aimed at the conservation and revitalization of historical structures, the overarching goal is to achieve remarkable structural improvement through minimally invasive means. In the context of the Saint George Church at the Bârnova Monastery, the technical condition was assessed qualitatively, through the identification of degradation and damage, and quantitatively, through seismic safety calculations. It was observed that, due to the accumulated deterioration over time and the lack of necessary funds for consolidation and rehabilitation, the church was in a structurally deficient state, and remediation through less invasive means was not feasible. However, by implementing a well-developed management strategy, the architectural essence of the structure was preserved, and the safety level was improved to 71% in the transverse direction and 91% in the longitudinal direction.

5. Discussions and Conclusions

The management of intervention works for the conservation and revitalization of historical structures presents a multifaceted challenge, necessitating a comprehensive understanding of architectural heritage, structural vulnerabilities, and effective rehabilitation strategies. This case study offers valuable insights gleaned from the conservation efforts undertaken at the Bârnova Monastery, situated in Iași, Romania.

Through a meticulous structural diagnosis, the vulnerabilities of the Saint George Church, a paramount structure within the monastery complex, were identified. These vulnerabilities, exacerbated by historical seismic events, underscored the imperative need for urgent intervention to safeguard this cultural heritage asset. The integrated strengthening approach adopted, comprising grouting and vertical rod installations, emerged as a judicious strategy to enhance both the seismic resilience and structural integrity of the church while preserving its historical authenticity.

The implementation of natural hydraulic lime-based grouting, augmented with a hydrophobic mixture to mitigate capillary water transport, exemplified a tailored approach to address the unique preservation needs of the masonry walls and foundation. The selection of materials and techniques was informed by empirical evidence and best practices in heritage conservation, ensuring compatibility with the structural substrates and morphological features of the heritage edifice.

Furthermore, the utilization of vertical tie rods, anchored within the foundation and integrated with reinforced concrete girders, exemplified a proactive measure to reinforce the structural stability of the church against seismic loads. This intervention, coupled with meticulous attention to detail in the execution of repair works for timber structural elements, exemplifies a holistic approach to heritage conservation that balances structural resilience, historical authenticity, and architectural integrity.

In conclusion, the case study of the Bârnova Monastery underscores the importance of adopting a multidisciplinary approach to intervention works, integrating architectural expertise, structural engineering principles, and heritage conservation practices. By leveraging innovative solutions and empirical knowledge, conservation efforts can effectively safeguard cultural heritage assets against deterioration, ensuring their continued relevance and resilience for future generations. This study contributes to the broader discourse on heritage conservation and offers practical insights for the management of intervention works in historical structures, thereby advancing the collective endeavor to preserve our architectural heritage for posterity.