Research and structural conservation of historic vaults

Łukasz Bednarz, Alicja Hoyenski, Gabriela Wojciechowska

doi:10.37190/arc240405

Summary

The article focuses on research and structural conservation of historic vaults. A comprehensive interdisciplinary approach to the analysis and preservation of historic vaulted structures is presented. Methods and techniques used in structural analysis and conservation of historic vaults are discussed, with particular emphasis on the latest technologies and conservation solutions.

✨ Summary generated by Artificial Intelligence. The actual Abstract can be found in the article below.

2024

4(80)

Łukasz Bednarz*, Alicja Hoyenski**, Gabriela Wojciechowska***

Research and structural conservation of historic vaults

DOI: 10.37190/arc240405

Published in open access. CC BY NC ND license

Abstract

This paper focuses on issues concerning the research and conservation of historic vaults with particular emphasis on condition analysis. Tradi-

tional and modern methods of strengthening vaults are presented, including techniques using composite materials such as: FRP (Fiber Reinforced

Polymer), FRCM (Fiber Reinforced Cementitious Matrix).

The process of assessing the condition of the vault using various methods, e.g., visual inspection, laser scanning, non-destructive NDT, is dis-

cussed. The paper presents an example of the use of carbon mesh to reinforce a vault in a historic building – highlighting the need for diagnostic mon-

itoring after repair work. The use of the HBIM (Historic Building Information Modelling) model to accurately represent the geometry and structural

analysis of the vault is described. The numerical model was created using the nite element method (FEM).

Eective conservation of historic vaults requires a harmonious combination of traditional methods and modern technologies. It has been shown

that the correct identication of structural problems and the adoption of appropriate conservation strategies are key to preserving architectural heri-

tage and ensuring its integrity for future generations. In addition, the importance of continuous diagnostic monitoring of the vault after repair enabling

ongoing assessment of the eectiveness of the methods used and early detection of possible structural problems was highlighted.

Key words: composite materials, historic vaults, exible joints, HBIM models

Introduction

As one of the most responsible structures, historic

vaults can lose their strength and aesthetic qualities when

exposed to adverse factors. Often, for reasons such as deg-

radation of materials changes in loads, altered water and

soil relations or the need to adapt to modern safety stan-

dards require strengthening measures. The conservation of

vaults often requires a combination of structural and ar-

chitectural conservation techniques. Reinforcements must

be planned and carried out with respect for the historical,

scientic and architectural values of these elements. The

design and selection of strengthening materials should re-

sult from a thorough assessment of the technical condition,

load analysis and stress distribution. The most common

methods of stabilising the technical condition and reinforc-

ing vaults include the use of tie-beam systems, glued-in

steel bars or sheets, injection and the increasingly popular

composite materials in the form of meshes, rods, cords,

mats and tapes of FRP (Fiber Reinforced Polymers) or

FRCM (Fiber Reinforced Cementitious Matrix) and poly-

meric prone joints (Jasieńko, Łodygowski, and Rapp 2006;

Kwiecień 2013; Bednarz 2021). Reinforcing the vaults

with these high-strength and exible construction materi-

als ensures increased stability and durability of the vaults.

The article presents the dierent types of reinforcement

used in the conservation of historic vaults, including tradi-

tional, modern and mixed methods, as well as an example

of the implementation of reinforcement from Silesia using

carbon nets, maintaining the authenticity and durability of

historic vaults.

Technical condition assessment of the vault

Before a strengthening and maintenance method is cho-

sen, a survey should be carried out to determine the con-

dition of the vault. This process involves several steps and

* ORCID: 0000-0002-1245-6027. Faculty of Civil Engineering,

Wrocław University of Science and Technology, Poland.

** ORCID: 0000-0003-1684-1579. Faculty of Architecture, Wro-

cław University of Science and Technology, Poland.

*** ORCID: 0000-0001-7041-5373. Faculty of Architecture, Wro -

cław University of Science and Technology, Poland, e-mail: gabriela.

wojciechowska@pwr.edu.pl

44 Łukasz Bednarz, Alicja Hoyenski, Gabriela Wojciechowska

uses various methods to gain a thorough understanding of

the current condition of the structure and to identify poten-

tial problems.

The visual inspection (Fig. 1) is the rst step in assess-

ing the technical condition of the vault. It allows the initial

identication of damage such as cracks, scratches, material

loss, dampness or deformation. Based on these observa-

tions, it can be determined which areas require more de-

tailed examination.

The condition assessment should include the produc-

tion of drawing (metric) documentation, in which struc-

tural damage, e.g., existing scratches and material loss, is

marked. The documentation should include detailed archi-

tectural drawings (Łużyniecka 2022), photographs, possi-

bly photogrammetric studies and/or 3D laser scanning to

create digital models of the structure. These models may

include geometric data augmented with metadata on mate-

rial parameters, architectural characteristics and the trans-

formation of the building – if HBIM (Historic Building In-

formation Modelling) documentation is developed or used

o-the-shelf.

It must be remembered that a correct assessment of the

state of preservation and the cause of damage results not

only from a thorough inventory and modelling, but also

from a knowledge of the history of transformations to

which the building has been subjected over the centuries.

This is followed, if possible, by material tests, includ

ing

strength tests, e.g., compressive and peel strength, chemi-

cal and physical analyses, material composition. Particular-

ly non-destructive methods (Non Destructive Test – NDT)

appear to be very useful at this stage of the procedure.

Based on the results, a suitable model should be selected

for the calculation (static or dynamic) (Scacco et al. 2020).

In vaults of brick, stone, concrete or mixed construction,

a structural analysis is recommended. Because the geom-

etry of vaults is dicult to capture in traditional computa-

tional models, FEM (Finite Element Method) models are

helpful in this respect. The use of FEM allows a detailed

analysis of the elements under the inuence of the loads

Fig. 1. Visual inspection of a failing vault using a drone

(photo by G. Wojciechowska)

Il. 1. Inspekcja wizualna sklepienia w stanie awarii przy użyciu drona

(fot. G. Wojciechowska)

acting on them (existing and designed). FE models are

valuable tools for the analysis and design of structural rein-

forcement using dierent types of materials. These models

use numerical methods to simulate the behaviour of the

structure and assess the eectiveness of the reinforcement

used. They also allow the simulation of dierent loading

variations and potential failures such as cracking, delami-

nation or overstressing.

Types of reinforcement for historic vaults

Reinforcing historic vaults is a process that requires

both knowledge of building technology and a deep un-

derstanding of the static working of these structures and

knowledge of conservation doctrine. Dierent methods are

used to ensure the durability and stability of these struc-

tures: traditional, modern or mixed. The type of reinforce-

ment chosen depends, among other things, on the technical

condition of the vault and the extent of the conservation

work that may be required, depending, for example, on the

artistic and architectural qualities of the vault.

Traditional methods

of reinforcing historic vaults

Traditional reinforcement techniques have been tested

for hundreds of years, proving their eectiveness and du-

rability. However, traditional materials may not provide

sucient strength to withstand dynamic forces in areas

exposed to vibrations from, for example, road or rail traf-

c. Traditional reinforcement methods may not meet the

requirements of current building standards for load-bear-

ing capacity and safety, especially for structures requiring

additional reinforcement due to new loads

Steel tie rods

Tie-beams can be used in a variety of vault types and

are tailored to the specic structural needs of a particular

building. They usually connect opposing vault headers,

thereby reducing strutting forces in the supports. In this

way, they prevent the vault from spreading laterally, which

could compromise the integrity of the entire structure. The

introduction of tie beams into the vault neutralises these

forces. This maintains stability and extends the life of

historic buildings. Anchoring elements must be properly

matched to the wall material to ensure adequate adhesion

and strength of the connection. Once the ends of the tie

bars are xed in the walls, the bars are tensioned using

special tensioning devices. This process involves gradu-

ally increasing the tension in the bars until a suitable level

of vault stabilisation is achieved. Steel tie rods are exposed

to corrosion and therefore need to be protected from the

elements. Various methods of protection are used, e.g.,

galvanising, painting with anti-corrosive paints, applica-

tion of protective coatings. The installation of tie-beams is

relatively non-invasive (usually the tie-beams have a small

cross-section and do not obscure the vault), which is im-

portant for historic buildings where the preservation of the

original building fabric is a priority.

Research and structural conservation of historic vaults 45

Injections

Injections are the process of introducing special injec tion

materials into cracks and ssures in masonry to strengthen

he structure from within. Injection materials include epo -

xy resins, cements, mineral mixtures and other specialised

substances to improve the cohesion and load-bearing ca-

pacity of the vault. Injections are primarily used to ad-

dress micro-spaces and cracks that can weaken the vault

structure. The process begins with a thorough analysis of

the condition of the structure, identifying the damage and

determining the areas requiring intervention. Pressurised

injection materials are then injected into the designated ar-

eas and all cracks and cavities are carefully lled. One of

the key decisions concerns the selection of the appropriate

material. Epoxy resins are characterised by their high me-

chanical strength and excellent adhesion to the substrate

– this makes them ideal for reinforcing highly stressed

structures. Cements and mineral mixtures, on the other

hand, are more compatible with historic building materi-

als, which is important in terms of preserving the authen-

ticity of the historic substance.

The injection process usually uses special injection

pumps that allow precise dosing of the material and con-

trol of the injection pressure. Monitoring and controlling

the eectiveness of the injection is also an important step,

where non-destructive methods, such as ultrasound, are of-

ten used. With these techniques, it is possible to accurately

determine the degree of gap lling and assess the eective-

ness of the reinforcement.

The injection method contributes to the strength of the

constituent materials, improves the load-bearing capacity

of the structure, and eectively seals and protects against

moisture and aggressive gases that can penetrate the ma-

sonry. The process of regenerating masonry vaults using

injection is very delicate and requires a series of carefully

selected preliminary measures. The selection of the injec-

t ant components and the adaptation of the consistency to

the specic needs of the case are crucial.

Reinforcing historic vaults using injection has many ad-

vantages. First and foremost, it is relatively non-invasive,

eectively reinforcing while preserving the original char-

acter of the monument. In addition, injections can be used

in conjunction with other strengthening methods, such as

glued-in steel bars or composite mesh, so that comprehen-

sive stabilisation of the structure can be achieved.

Bonded steel bars or sheets

The technique of inserting steel bars or plates involves

introducing steel elements into the construction of vaults

to carry additional loads and improve the integrity of the

building. The strengthening process begins with a thor-

ough analysis of the technical condition of the vault and the

iden

tication of the areas that need strengthening. Once

these areas have been determined, appropriate cuts or holes

are made in the structure into which the steel bars or plates

will be inserted. The steel elements are then thoroughly

cleaned and protected against corrosion. When steel bars

are pasted in, the elements are placed in specially prepared

channels that can be made in the vault. The bars are then

xed with special epoxy or cement adhesives to ensure

their permanent bond to the structure. These adhesives

are characterised by high strength and excellent adhesion

to a variety of building materials, which guarantees the

eectiveness of the reinforcement. As with the bars, the

pasting of the steel sheets consists of placing them in pre-

pared notches in the vault. These plates are usually pasted

on the surface of the vault or in its cross-section – depend-

ing on the specic construction and reinforcement needs.

The process requires precise surface preparation, as well

as the right choice of adhesives. This method allows for

a signicant increase in the strength of the structure, but

due to the extent of the work it does not allow for rapid

reinforcement, which is crucial when the structure needs

to be secured quickly.

Modern methods of reinforcing historic vaults

Modern reinforcement techniques use composite ma-

terials and technologies that minimally interfere with the

original structure of monuments. Modern composite mate-

rials are lightweight and have high tensile strength, making

them suitable for increasing the load-bearing capacity of

vaults without signicant additional weight. They are also

exible, allowing them to accommodate possible “move-

ments” and deformations of the vault. This is particularly

important for structures located both in areas with increased

seismic activity and in historic city centres with increased

vehicular trac. These materials are corrosion-resistant,

ensuring long-term durability and minimising the risk of

deterioration over time. Reinforcing historic structures

with innovative composite materials follows conservation

principles – it is minimally invasive and reversible (with

proper design and execution).

Among the most common modern strengthening meth-

ods are surface reinforcement with composite materials

and polymeric exible joints.

Surface reinforcement using composite materials

(FRP/FRCM)

Surface reinforcements using composite materials can

be in the form of meshes, rods, cords, mats, tapes and

sec tions of FRP or FRCM systems. Thanks to their high

strength and low weight, they eectively reinforce struc-

tures while minimising interference with the historic fab-

ric. FRCM systems use reinforcing bres (carbon, glass,

basalt, aramid, PBO (e.g., polyparaphenylene benzobi-

soxazoles) as the xing matrix; the mineral compositions

have relatively good vapour permeability and do not block

moisture migration in the form of water vapour, which is

very important when there are, for example, frescoes on

the vaults, on the side of their palisade, which require

structural intervention. It is important to remember to

analyse in detail the method of application and the type

of composites used. Improper use, disregarding the laws

of statics and building physics, can be associated with the

destruction of an object of considerable architectural and

cultural value.

46 Łukasz Bednarz, Alicja Hoyenski, Gabriela Wojciechowska

Numerous studies have shown (Valluzzi, Tinazzi, and

Mo dena 2002; Oliveira, Basilio, and Lourenço 2010; Ca-

rozzi, Milani, and Poggi 2014; Lignola et al. 2017) that

this type of reinforcement is suitable for the repair of struc-

tures, including masonry, as it provides them with an ade-

quate level of safety, especially when these are subjected

to asymmetric loads.

The term composite material refers to a material that is

constructed from at least two dierent components, with

their combination occurring at the macroscopic level. In

most composite materials, two phases are distinguished:

a matrix (matrix), which acts as a binder, and a dispersed

phase (reinforcement) (Fig. 2). The properties of the com-

posite depend on the properties of the two phases, their

proportions in the total volume of the composite, how the

dispersed phase is distributed in the matrix and its geomet-

rical features. Depending on the type of dispersed phase,

composite materials are divided into particle-reinforced,

dispersion-reinforced and bre-reinforced.

Fibre-reinforced composites, which are very often used

to reinforce masonry structures, use various bres as load-

bearing elements (Figs. 3, 4). The matrix not only binds

the bres together, but also distributes external loads be-

tween the bres and protects them from external inuences.

FRP bre-reinforced composites in polymer matrixes

(thermoplastic and thermosetting resins) and FRCM in

mineral matrixes are characterised by very good technical

performance, as well as relatively simple production meth-

ods and moderate costs. These characteristics make them

extremely eective for practical use – while providing ex-

cellent mechanical strength with minimal dead weight.

Glass bres are the oldest and cheapest bres used to

reinforce composites. A major disadvantage of the resin

matrix composite reinforcement system is the poor re

resistance of the bonding – the adhesive, where already at

Fig. 2. Composite materials

(elaborated by Ł. Bednarz)

Il. 2. Materiały kompozytowe

(oprac. Ł. Bednarz)

Fig. 3. Vault during installation of carbon mesh composite

reinforcement (photo by Ł. Bednarz)

Il. 3. Sklepienie w trakcie układania zbrojenia kompozytowego

z siatek węglowych (fot. Ł. Bednarz)

Fig. 4. Vault after reinforcement (photo by Ł. Bednarz)

Il. 4. Sklepienie po wykonaniu wzmocnienia (fot. Ł. Bednarz)

Research and structural conservation of historic vaults 47

60°C the shimmering process starts and the linear and form

deformability increases.

FRCM systems use an inorganic mortar consisting of

a hydraulic binder and additives – chemically, physically

and mechanically compatible with the substrate, especial-

ly brick masonry. FRCM systems oer several important

advantages, including: heat resistance, applicability to

damp substrates, ease of application on uneven substrates,

and applicability over a wide temperature range from +5°C

to +40°C.

Polymeric flexible joints

Polymeric exible joints are used to connect and rein-

force damaged or weakened vault components to both ensure

structural stability and maintain historic integrity (Kwie cień

2013).

In this method, susceptible polyurethanes are used

to strengthen masonry structures – primarily through injec-

tions that create exible joints that can transmit and dissi-

pate signicant amounts of deformation energy. The pliable

polyurethanes are used in two main roles: as exible joints

for lling cracks in masonry (PolyUrethane Flexible Joints

– PUFJ) and as an adhesive layer and matrix in composite

joints (Fibre Reinforced Polyurethane – FRPU).

In laboratory tests, exible polyurethane joints were

shown to signicantly increase the load-bearing capacity

of masonry structures compared to traditional repair meth-

ods such as cement mortars or rigid epoxy resins. In four-

point bending tests, polyurethane joints outperformed the

traditional ones because they did not damage the repaired

bricks. This is crucial in the conservation of historic ma-

sonry – as preserving the original material is a priority.

Vulnerable polyurethanes used as adhesives to reinforce

masonry using FRPU composites reduce the stress concen-

trations typical of rigid layers made of mineral mortars or

epoxy resins. As a result, shear stresses are more evenly

distributed, protecting composite bres and brittle masonry

substrates from localised damage that can lead to rapid peel-

ing and reduced joint eectiveness. As a result, the use of

polyurethanes increases the load-bearing capacity of the re-

inforcement and protects historic substrates from damage.

The two main applications of susceptible polyurethanes

in FRPUs are – the use of ready-made composite lami-

nates (with bres embedded in an epoxy matrix) bonded to

a weak substrate with a susceptible polyurethane adhesive,

and the use of highly deformable polyurethanes as a matrix

for the composite bres. In the rst case, the composite

laminates transfer loads more uniformly and reduce the

risk of local damage. In the second, the exible polyure-

thane matrix evens out the curvature of the bres – thus

enabling loads to be transferred evenly over a greater num-

ber of bres, increasing the strength of the composite and

reducing shear stresses in the substrate.

The use of a susceptible polyurethane matrix in FRPU

technology not only distributes stresses over all the bres in

the cross-section, but also acts as an elastic adhesive layer

and increases the ability of masonry structures to withstand

dynamic loads and uneven settlements. This is particu-

larly important for historic buildings, where maintaining

structural integrity is crucial to their longevity and safety.

Mixed methods

Reinforcing historic vaults often requires mixed meth-

ods, which combine a variety of techniques to ensure

optimal stabilisation and preserve the authenticity of the

structure. Mixed methods combine traditional and modern

technologies to achieve optimum results in the conserva-

tion process. In some cases, especially when vaults are se-

verely damaged, a combination of traditional techniques

(e.g., steel bar pasting) and modern composite materials

is used. This approach allows for optimal strengthening of

critical areas of the vault, while maintaining the structural

integrity and aesthetic appearance of the historic building.

Another example is the use of tie-beams with composite

meshes.

Diagnostic monitoring

Once the vaults have been reinforced, systematic diag-

nostic monitoring of the vaults is necessary (Bednarz 2021;

2023; Bednarz et al. 2021) to ensure that the reinforcement

is eective and that there are no signs of further damage or

material degradation. This enables and early response to

potential problems, and ensures the long-term preservation

of historic vaults.

The diagnostic monitoring of historic buildings itself,

associated with what is known as Structural Health Mon-

itoring (SHM), is the process of observing and analysing

the condition of a building in real time. It is one of the

tools of diagnostics in its broadest sense, alongside mate-

rials testing and structural analysis – extremely helpful in

the early detection of structural defects or damage posing

potential safety risks to people and the structure itself.

The purpose of diagnostic monitoring is to continu-

ously measure key geometrical, mechanical and physical

parameters of a structure or its components that change

over time. This provides knowledge of a given situation

by identifying the mechanisms of change at an early stage.

Thus, diagnostic monitoring is intended to facilitate the

implementation of appropriate preventive and corrective

measures in historic structures.

Example of implementation

of reinforcement with carbon mesh

Using the example of research carried out on the vault-

ing of a church in Silesia, it is possible to illustrate how

the methods described in this article can be used to assess

the technical condition and select an appropriate method of

structural conservation of the vaulting (Fig. 5). The lunette

vaulted church was built in the 18

century. The vaults of

the church can be divided into two zones. Zone one, which

is the largest part, is the vaulting of the nave. It is a cradle

vault divided into bays by porticos located on the dorsal side

of the vault. Within each bay there are two lunettes located

opposite each other. There are a total of ve bays with-

in the nave. The radius of the vault arch is approximately

3.45 m, the arrow approximately 3.33 m. The lunettes

with a ridge descending towards the outside. Based on

the measurements, the thickness of the vault shell was

48 Łukasz Bednarz, Alicja Hoyenski, Gabriela Wojciechowska

present between the 1

and 2

and 3

bays on

the side of the rainbow arch under the vault arches xed at

a height of approximately 6.50 m above the oor. The area

of the chancel and apse can be considered as the second

zone. The chancel has a cross vault. The thickness of the

vault shell was assumed to be about 0.12 m, with ridge

gourds about 0.30 m thick and about 0.25 m wide. The

semi-circular apse of the presbytery is covered by a vault-

ed ceiling with three radial lunettes in a complex form of

arches. The layout of the apse, like that of the entire vault,

is symmetrical (Fig. 6). The above-mentioned areas are

separated from each other by a rainbow arch. The support

of the vault in question is provided by the perimeter walls

of the nave and chancel.

The most worrying damage in the analysed building is

the cracks mainly concentrated in the zone of the vaults

and the external walls of the nave. The main axis along

which cracks and ssures appear is the axis of the nave

and the lines running transversely to the axis of the nave,

passing through the central part of the vault. They cover al-

most the entire surface of the vault. These cracks have their

continuation on the side walls and near the window open-

ings (damage to the lintels is visible). A similar situation is

present in the chancel and apse area. There, too, numerous

cracks and scratches are visible (Fig. 7). No major damage

was found in the axis of the apse.

The outstanding scratch is a crack running across the

rainbow arch, which is a continuation of the damage to the

nave vault in the main axis of the church.

The previously described scratches have varying de-

grees of opening. The largest cracks are found in the con-

nection between the vaults and the external walls (they can

be up to several centimetres wide on the dorsal side of the

vaults). Numerous cracks of considerable opening also oc-

cur on the external walls of the body and the tower. Some

of the wall scratches are also visible on the outside of the

building.

The arrangement of the described scratches indicates

the occurrence of tensile forces within the vaults and the

walls supporting them. The direction of these forces is

mainly directed across the axis of the church. The prob-

able cause of this situation is the location of the church

on a small escarpment cut o from the road by a retain-

ing wall excessively irrigated periodically by water from

surface run-o from the adjacent cemetery and trac of

heavy agricultural machinery.

Fig. 5. Laser scanning point cloud (elaborated by G. Wojciechowska)

Il. 5. Chmura punktów ze skaningu laserowego (oprac. G. Wojciechowska)

Fig. 6. HBIM model – simplified model of the body of the church

and detailed model of the vault (elaborated by A. Hoyenski)

Il. 6. Model HBIM – uproszczony model bryły kościoła

i szczegółowy model sklepienia (oprac. A. Hoyenski)

Fig. 7. View of the vault from below – damage inventory

(elaborated by A. Hoyenski)

Il. 7. Widok sklepienia od dołu – inwentaryzacja uszkodzeń

(oprac. A. Hoyenski)

assumed to be approximately 0.12 m, the ridged ridges

to be

approximately 0.30 m thick and from approximate-

ly 0.47 m to approximately 0.60 m wide. Additional re-

inforcements of the vault in question (two steel ties) are

Research and structural conservation of historic vaults 49

Description of the study

To accurately represent the geometry of the vault, laser

scanning was used. It provided precise data on the shape

and dimensions of the vault and enabled a detailed digital

representation to be created. Figure 5 shows the data in the

form of a point cloud – from this a detailed 3D model of

the vault was created (Figs. 6, 7).

Model HBIM

Historic Building Information Modelling (HBIM) is

a tool that allows the integration of collected data into

a single digital model. In the case of the church in question,

the HBIM model included data from laser scanning (vault

geometry) and non-destructive testing (material data). Due

to the specic nature of the task, the vault model was made

at a higher level of detail than the exterior walls of the

church (Fig. 6). The model was the basis for simulations

of the behaviour of the structure under dierent loads in

numerical analysis software.

Numerical model

based on the finite element method

(FEM)

The analysis of masonry structure performance and cal -

culations are very complex issues. This is due to the two-

material structure of the masonry, which consists of bricks

joined by a thin layer of mortar. This composite structure

leads to anisotropy and non-linear material behaviour. In

engineering practice, simplied calculation methods based

on long-term experimental studies conducted on real or

simplied models of masonry are often used (Magenes,

Calvi 1997; Hendry 2001).

However, when a precise analysis of both the material

itself and the structure made of it is needed, this approach

proves insucient. This is particularly the case when an-

alysing historic and historical buildings. When renovating

and reinforcing these structures, which usually have a com-

plex static system and high dead weight, it is necessary to

use more advanced calculation methods. In such cases, the

nite element method (FEM) is very helpful.

The calculations carried out using FEM allowed a de-

tailed analysis of the mechanical properties of the vault.

The numerical model was created using a homogenis-

ed material model, the parameters of which were deter-

mined, among other things, on the basis of laboratory

tests. The nite element method provided simulation of the

stress and strain distribution under various loading scenar-

ios. This made it possible to identify the weakest points in

the structure and predict potential failure locations.

Choice of amplification method

Due to the extensive damage to the vaults, with cracks

on the dorsal side reaching up to several centimetres in

opening width, and the scratching of the external walls,

it was necessary to reinforce the object at the level of the

vaults. In this case, the decision was made to use steel

ties to stien the longitudinal and transverse system of

the building. Within the vaults, injections were designed

as well as reinforcement and consolidation of the dorsal

surface with C-FRCM (Carbon Fiber Reinforced Ce

mentitious Matrix).This state-of-the-art reinforcement

method ensures adequate load-bearing capacity, dura-

bility and minimal interference with the original historic

structure.

Reinforcement of the vaults with carbon nets accord-

ing to the C-FRCM system was carried out over the entire

scratch area in a single layer on the dorsal side (Fig. 8).

Larger cavities and irregularities in the vaults were lled

with the system’s levelling mortar. An approximately

3 mm thick system-specic xing mortar was applied to

the moistened substrate. The carbon mesh was immedi-

ately blended in and covered with a second layer of the

approximately 3 mm thick system xing mortar. The mesh

was laid from armpit to armpit of the vault and from rib to

rib, extending the mesh over the ribs and over the walls to

a height of min. 20 cm.

Once the reinforcements were in place, anchoring of the

carbon mesh reinforcements to the walls was carried out

using rolled-up strips of mesh (min. 40 × 60 cm in size)

xed in the openings in the walls in an arrangement de-

termined during the work. Holes 30–36 in diameter and

at least 25 cm deep were lled with an epoxy compound

after thorough cleaning and blowing out with compressed

air, and then a coiled carbon mesh was placed in them. The

parts of the mesh protruding from the wall were blended

into the 3 mm thick xing system mortar. A similar proce-

dure was carried out on the vaults and dorsal ribs by us-

ing anchor spacing every min. 1.5 m (for linear joints) and

1 pc. / 1.5 m

(for surface connections).

Diagnostic monitoring

Once the repair work was completed, it was recom-

mended that a diagnostic monitoring system be im-

plemented that included the installation of meters to

monitor key parameters of the structure, i.e., scratches,

deviation from vertical, temperature and humidity inside

and outside. The monitoring data should be analysed on

a regular basis, allowing an ongoing assessment of the

eectiveness of the repairs and a rapid response to any

problems.

Fig. 8. Diagram of vault repair using carbon mesh

(elaborated by A. Hoyenski)

Il. 8. Schemat naprawy sklepienia przy użyciu siatki węglowej

(oprac. A. Hoyenski)

50 Łukasz Bednarz, Alicja Hoyenski, Gabriela Wojciechowska

Summary

The investigation and conservation of historic vaults is

a complex process requiring an interdisciplinary approach

combining traditional repair techniques with modern

methods of analysis and strengthening. The assessment

of the technical condition of a historic vault is non-sim-

ple and multi-stage. It requires the use of various research

methods. Visual inspection, photogrammetry, laser scan-

ning, non-destructive testing, HBIM modelling and nu-

merical modelling using FEM collectively allow precise

diagnosis and eective strengthening of historic buildings

to ensure their durability and safety.

The paper presents a variety of strengthening tech-

niques, including traditional methods such as the use of

tie-beams, injection, and the pasting of steel bars or plates,

as well as modern approaches using composite materials.

It also highlights the advantages of mixed methods

combining traditional and modern techniques to enable

a more comprehensive approach to the conservation of his-

toric structures. Special attention was given to innovative

solutions (such as the use of susceptible polyurethanes in

FRPU systems and C-FRCM composites) and their eec-

tiveness in repairing damaged masonry structures.

The practical application of the methods described is

illustrated on the example of a study of the vaults of a church

in Silesia. Thanks to a comprehensive assessment of the

technical condition and the use of carbon nets to reinforce the

vault, the durability and safety of the structure was achieved

with minimal interference with its original character.

Once a historic vault has been repaired, it is essential to

implement systematic diagnostic monitoring to enable long-

term evaluation of the eectiveness of the maintenance

work carried out and early detection of any problems. Di-

agnostic monitoring is a key element of a preventive main-

tenance strategy.

In conclusion, it can be assumed that eective conserva-

tion of historic vaults requires a harmonious combination

of traditional methods and modern technologies. An inter-

disciplinary approach taking into account the latest devel-

opments in materials engineering and digital technology is

essential in preserving cultural and architectural heritage

for future generations.

Translated by

Łukasz Bednarz,

Alicja Hoyenski,

Gabriela Wojciechowska

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Research and structural conservation of historic vaults 51

Streszczenie

Badania i konserwacja konstrukcyjna sklepień historycznych

W artykule skupiono się na zagadnieniach dotyczących badań i konserwacji sklepień historycznych ze szczególnym uwzględnieniem analizy stanu

technicznego. Przedstawiono tradycyjne oraz nowoczesne metody wzmacniania sklepień, w tym techniki wykorzystujące materiały kompozytowe,

takie jak FRP (Fiber Reinforced Polymer) i FRCM (Fiber Reinforced Cementitious Matrix).

Omówiono proces oceny stanu technicznego sklepienia, wykorzystując metody takie jak inspekcja wizualna, skaning laserowy oraz nieniszczące

badania NDT (non-destructive testing). W artykule przedstawiono przykład zastosowania siatek węglowych do wzmocnienia sklepienia w historycz-

nym obiekcie, podkreślając konieczność monitoringu diagnostycznego po przeprowadzeniu prac naprawczych. Opisano zastosowanie modelu HBIM

(Historic Building Information Modelling) do precyzyjnego odwzorowania geometrii i analizy konstrukcyjnej sklepienia. Model numeryczny został

utworzony przy użyciu metody elementów skończonych (MES).

Efektywna konserwacja sklepień historycznych wymaga harmonijnego połączenia tradycyjnych metod z nowoczesnymi technologiami. Wyka-

zano, że właściwa identykacja problemów konstrukcyjnych oraz zastosowanie odpowiednich strategii konserwatorskich są kluczowe dla zacho-

wania dziedzictwa architektonicznego i zapewnienia jego integralności na przyszłe pokolenia. Ponadto podkreślono znaczenie ciągłego monitoringu

diagnostycznego sklepienia po naprawie, co pozwala na bieżącą ocenę skuteczności zastosowanych metod oraz wczesne wykrywanie ewentualnych

problemów strukturalnych.

Słowa kluczowe: materiały kompozytowe, sklepienia historyczne, złącza podatne, modele HBIM