THE ROYAL PALACE IN CASERTA: NON- DESTRUCTIVE TESTS …€¦ · 11] to design and build the Royal...

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International Journal of Advanced Research in Engineering and Technology (IJARET)

Volume 11, Issue 5, May 2020, pp. 537-546, Article ID: IJARET_11_05_055

Available online athttp://www.iaeme.com/IJARET/issues.asp?JType=IJARET&VType=11&IType=5

ISSN Print: 0976-6480 and ISSN Online: 0976-6499

DOI: 10.34218/IJARET.11.5.2020.055

© IAEME Publication Scopus Indexed

THE ROYAL PALACE IN CASERTA: NON-

DESTRUCTIVE TESTS FOR SAFETY AND

CONSERVATION

M. Guadagnuolo, I. Titomanlio, G. Faella

Department of Architecture and Industrial Design

University of Campania “Luigi Vanvitelli”, Aversa (CE), Italy

C. Gambardella

Pegaso online University, Napoli, Italy.

ABSTRACT

The paper deals with the in-situ surveys performed within an integrated knowledge

plan aimed at the conservation design of the façades of the Royal Palace in Caserta

(“Reggia di Caserta”) in Campania, Italy. Surface penetrating radar tests, covermeter

testing, infrared thermography analyses, and endoscopic inspections were performed

as complementary methods of surveys. The paper describes the equipment, the testing

arrangement and the main outcomes. The falling of some large portions of facing slabs

is identified to be due to the oxidation of the metal cramps. The position of the anchor

cramps has then systematically identified, showing that they are not arranged according

to specific alignment rules. This allows assessing the structural safety of the facing

stones and drawing data for the restoration activity and the conservation management

plan.

Keywords: Cultural heritage, Facing slab safety, Masonry, In-situ testing

Cite this Article: M. Guadagnuolo, I. Titomanlio, G. Faella and C. Gambardella, The

Royal Palace in Caserta: Non-Destructive Tests for Safety and Conservation,

International Journal of Advanced Research in Engineering and Technology (IJARET),

11(5), 2020, pp. 537-546.

http://www.iaeme.com/IJARET/issues.asp?JType=IJARET&VType=11&IType=5

1. INTRODUCTION

Cultural heritage and monumental architecture are of great value to society from a cultural,

environmental, social and economic point of view, and their safeguarding is of paramount

importance [1-2]. Frequently their preservation and safety are related to their non-structural

elements [3], and then an integrated approach is necessary [4]. Adequate knowledge of building

structures for assessing structural safety and defining appropriate restoration solutions is a key

step in the design process. Also, because today it is possible to perform particularly detailed

non-linear numerical analyses [5]. Despite the recent advances in non-destructive testing

M. Guadagnuolo, I. Titomanlio, G. Faella and C. Gambardella


technology [6-9], today no technique is suitable for all situations, and then the careful

application of complementary techniques often provides the most reliable information.

This paper deals with the experimental activities performed on the façades of the Royal

Palace in Caserta (Campania, Italy), as step of the fundamental path of knowledge. The activity

firstly involved historical researches and subsequently in-situ tests, as laser scanning surveys

and non-destructive testing on masonry structures and façades. The safety of façades facing

stones and overhanging masonry elements was mainly investigated. In fact, due to the oxidation

of the metal cramps of the veneer facing stones, in recent years, some stone slabs of

considerable size, and from a great height, fell. The fall of façade elements represents an

element of great criticality for the conservation of cultural heritage and public safety, and their

securing requires a thorough knowledge of the supporting structural elements and state of

conservation.

2. HISTORICAL RESEARCH

The Royal Palace in Caserta (Italy) is one of the great examples of late eighteenth-century

architecture with its park and its sophisticated watercourses. In 1930 Gino Chierici declared:

“the royal palace is one of the most harmonic, logical, most perfect architectural designs of all

time” (Figure 1). The Bourbon king Charles III wanted the palace to be the seat of power and

to represent the magnificence of their dynasty. He commissioned architect Luigi Vanvitelli [10-

11] to design and build the Royal Palace, competing with the Versailles Palace [12-15].

Figure 1 The Royal Palace in Caserta

In the same years, Vanvitelli was involved in the restoration of the Basilica of Loreto

(commissioned by the Pontifical State) but he answered positively to the call of King Charles

III [16-17]. Vanvitelli was commissioned to design the complex composed by the Palace, the

Park, the buildings surrounding the urban area, and the Aqueduct (later called Carolino) (Figure

2). In 1751 the final project was approved and the following year the foundation stone was laid

with a great ceremony. Gennaro Maldarelli painted that moment under the canopy of the Throne

Room.

Several artists were involved to work with Vanvitelli. Marcello Fronton collaborated on the

building design and Francesco Collecini collaborated on the park and the aqueduct design. The

building lasted several years and some details were left unfinished [18]. Ferdinand IV, who

later became Ferdinand I (the king who came after Charles III) did not share the same

enthusiasm for the Palace. In 1773 Vanvitelli died and his son Carlo continued the work. The

The Royal Palace in Caserta: Non-Destructive Tests for Safety and Conservation


father's genius was hard to interpret, so it was difficult to finish the building according to the

original project [19-21].

Figure 2 The Royal Palace in Caserta: historical design

The Palace currently covers an area of approximately 44000 square meters. The materials

needed for building the Palace (at the time the cost was 6.133.507 ducats) mostly came from

existing quarries in the area or the kingdom's territories: San Nicola la Strada, Bellona

(travertine), Mondragone (gray marble), San Leucio (lime), Bacoli (pozzolan), Gaeta (arena),

Capua (bricks), Sicily, Calabria and Puglia (various marbles) [18]. The choice of marble was

handled by French sculptor Giuseppe Canart. He was a restorer at the king's service and a

connoisseur of ancient marbles (white Carrara marble was used for some statues and

decorations). The rectangular layout of the Palace, (247x190 meters) was divided into four

courtyards (each of 3800 sq, m). This design concept was defined as an optimal model of

architecture, meeting to space distribution requirements according to the intended use [22-23].

The total height of the Palace is 41 meters. It was composed by 1.200 rooms lit by 241

windows at the front and 241 on the back. The chimneys on the roof were 1026, indicating the

presence of fireplaces in almost every room.

Different types of vaults (cross vaults, barrel vaults, cloister vaults, rib vaults, etc.) were

used. This made necessary outer walls 3.50 m thick at the ground floor. The roof had timber

trusses made in abetone of Sila and large tiles coming from the furnaces of Portici, put in place

by talented teachers Zappi and Rossi.

Immediately after the central gate, the superb three naves gallery (high and wide the main,

narrower, and lower the side ones) leads to the central octagon. Here bundles of Bigliemi stone

columns hold four strong large arches, set up the access to the four courtyards and, on the right

side, to the majestic staircase decorated with polychrome marbles (18.50 meters wide, 14.50

meters high and 117 steps long) [19]. Besides the octagon gallery, the green park provides a

beautiful scenic movement. The Royal Palace was declared World Heritage by UNESCO in

1997.

The thorough historical documentation, which covers many features of the Palace building,

does not contain a description or a graphic representation of the technique through which the

large facing slabs of the internal and external façades were anchored to the wall structure at the

back. This shortcoming made necessary to carry out an in-depth experimental activity in-situ,

as described below.

3. EQUIPMENT AND TESTING ARRANGEMENT

3.1. Surface penetrating radar test

The Surface Penetrating Radar (SPR) applied to masonry buildings [24-25] allows detecting

the presence and location of anomalies or hidden objects using the electromagnetic waves



reflection phenomenon [26-27]. The tests were carried out using a multi-frequency SPR

equipment with several antennae (from 800 to 2000 MHz), software "K2" and "IDS_Gred" for

data acquisition and processing. The purpose of the SPR tests was the inspection of the veneer

facing stones, the identification of the masonry stratigraphy, and the search of anomalies and

hidden metal cramps in the exterior and interior façades of the Royal Palace. The scans were

executed according to a thick grid for identifying all possible anomalies, as illustrated in the

following.

3.2. Infrared thermography analysis

The infrared thermographic technique provides a visible representation of infrared energy

radiated by an object, according to the fundamental law of Planck (all objects at temperatures

above absolute zero emit infrared radiation) [28-29]. The scan cameras with infrared is a global

approach, which allows a rapid assessment of large regions without requiring direct access to

the wall. The high-resolution FLIR “ThermaCam SC3000 Thermal Imaging System”, was used.

This camera utilizes an advanced sensor that provides extremely high sensitivity (less than 20

mK at 30°C), allowing ultra-precise accuracy in measurement. Many infrared thermographic

images, taken from several points of view, allowed analyzing several features of the building

structures of the Royal Palace [30-31].

3.3. Fiberscope testing

The endoscopic test allows a visual examination of internal cavities or the interior of small

diameter holes made in specific points of the building. The technique is based on the properties

of optical fibers to transmit light through successive reflections. The flexible fiberscope "XL

PRO Base System" was used. This fiberscope has a high-resolution camera (with 440.000 pixel

true-color images), and a flexible probe with diameters from 3.9 to 8.4 mm. Visual inspections

were performed in several locations where was deemed necessary to observe and identify

anomalies or internal wall components, to better understand the actual condition of the

structure.

3.4. Covermeter testing

The covermeter inspection allows identifying and measuring dimensions and covering of

hidden metallic elements. The covermeter “Protovale CoverMaster CM9” was used. The target

was the search of the anchor cramps of the veneer facing stones of the courtyard exterior and

interior walls. The scan was performed using a dense pitch grid. The results were compared to

those provided by the SPR survey, to have only one position of all identified metal elements.

4. MAIN RESULTS OF NON-DESTRUCTIVE TESTS

The main purpose of the tests was the identification of the anchor cramps supporting the facing

stones of façades, to monitor their state of conservation. Many were strongly oxidized, as visible

for the few accessible (Figure 3). Due to the consequent loss of bearing capacity or cramp

volume enlargement (that break the stones), some facing stones could fall with possible

dramatic effects, because of their large size and height above the ground. Some detachments

and collapses already occurred in the past years, as shown in Figure 4.

The results of the tests performed on the north outer façade (identified by the letter A in

Figure 5) and on the south facade of the south-east courtyard (identified by the letter B in Figure

5) are described in the following.



Figure 3 Metal cramps oxidized

Figure 4 Detachments of facing stone parts due to cramp oxidation

Figure 5 The façades analyzed in the paper

4.1. North outer façade (A)

Figure 6 shows the longitudinal SPR scans performed on the north outer façade. The

longitudinal and transverse radargrams of the lower part of the façade (Figure 7) allowed to

identify the stratigraphy of the outer layers of the wall. After the first dense layer about 15 cm

thick, corresponding to the veneer facing slabs, there is a succession of a denser layer (about 25

cm thick, probably regular tuff masonry) and a less compact layer (about 15 cm thick, probably

chaotic tuff masonry with voids).



The SPR scans also detected several metal elements and some small cavities, and

irregularities inside the wall. The covermeter scans recognized the position and depth of the

metal elements. Unfortunately, both the survey techniques (SPR and covermeter) identified

both the metal cramps and the lead plates placed between the facing stones to align them

horizontally during the construction. Both cramps and plates do not have a regular arrangement,

but the anchor cramps have greater penetration into the wall than the lead plates. Furthermore,

the cramps have different geometry and size while the lead plates are much more regular in size

and small (few centimeters wide and less than a centimeter thick). Figure 8 shows the schematic

synthesis of the metal elements detected in the first 30 cm in depth in the lower portion of the

examined wall. Blue and red markers identify anchor cramps while black circles identify the

lead plates.

Figure 6 Longitudinal SPR scans on the north outer façade



Figure 7 Longitudinal and transverse radargrams of the north outer façade

4.2. South facade of the south-east courtyard (B)

The SPR scans performed on the south facade of the south-east courtyard confirmed the same

masonry stratigraphy obtained for the other façades.

The veneer facing stones of the façade, in addition to the oxidation of the metal cramps,

showed degradation phenomena and repairs executed in the past (Figure 9). Therefore, infrared

thermography scans and fiberscope inspection were performed (Figure 10). These surveys

allowed detecting the different materials used in the façade restoration and the degradation on

and between the facing stones, integrating the results already obtained through the SPR and

covermeter scans.

Figure 8 Synthesis of the metal elements detected in the lower part of the north outer façade



Figure 9 Degradation phenomena and repairs of the South façade of the south-east courtyard

Figure 10 Thermographic images of the South façade of the south-east courtyard

5. CONCLUSIVE REMARKS

The failure of veneer facing stones from the façade of heritage buildings has significant

consequences on conservation and public safety. This paper describes the in-situ tests

performed within an integrated knowledge plan aimed at the conservation design of the façades

of Royal Palace in Caserta (Italy).

Surface penetrating radar and covermeter testing were systematically performed on the

façades as complementary methods for qualifying the masonry and locating metal elements that

could be a source of possible safety problems, when oxidized. Where necessary, infrared

thermography scans and endoscopy inspections were executed for quantifying degraded or

deteriorated areas. The in-situ surveys allowed knowing the causes of the falling of some facing

stones and, mainly, identifying the position of the metal cramps. These were differently let into

the surface of the stones, without a specific rule. The SPR scans also provided information on

the masonry stratigraphy while the infrared thermographic surveys provided synthetic data on

previous restoration works and degradation phenomena.

All the performed surveys show that the detachment of some facing stones or part of them

is not a recent pathology. That is assumed to have happened even in past times and is now

speeded up by the increased concentration of pollutants.

ACKNOWLEDGEMENT

Authors wish to thank Architects Alfonso Donadio and Luca Ferri for their contribution in the

experimental activities. In-situ tests were performed using equipment provided by the Benecon

Scarl.



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