WO2012042510A1

WO2012042510A1 - Tube-jack system and method for testing irregular masonry walls

Info

Publication number: WO2012042510A1
Application number: PCT/IB2011/054333
Authority: WO
Inventors: José Luís FERREIRA DA SILVA RAMOS; Francisco Manuel Carvalho Pinto Fernandes; Paulo Mateus Mendes; Leandro Nuno Martins Vieira Marques
Original assignee: Universidade Do Minho
Priority date: 2010-10-01
Filing date: 2011-10-03
Publication date: 2012-04-05
Also published as: EP2622318A1

Abstract

System and method to analyze the pressure (or stresses), the deformability (Elastic moduli) and strength of masonry or adobe structural elements (1). The system comprises a number of tube-jacks (2), expandable tubular elements, connected in parallel, with a number of displacement transducers measuring the displacement of the masonry near the line of the tube-jacks, that when inserted into holes drilled in a stressed masonry element or wall (1), and inflated with fluid, through suitable connectors (3, 4, 6) to a pressure generator, expand to the size of the holes, and provide the necessary stress and displacement measurements, together a pressure gauge (5), to calculate the existing local compressive stress, the deformability and whenever possible, the strength of the masonry. Application includes historical and heritage constructions containing masonry or adobe structural elements with large and irregular stone units and nonlinear mortar joints.

Description

D E S C R I P T I O N

"TUBE-JACK SYSTEM AND METHOD FOR TESTING IRREGULAR MASONRY

WALLS"

TECHNICAL FIELD

The invention relates to a method for inspection and diagnosis for masonry elements within structures. More specifically, it relates to a non-destructive or minor- destructive method for detection of mechanical characteristics (stresses, deformability and strength) in the area of preservation of irregular masonry.

SUMMARY

The present invention relates to a new method and system to analyze the pressure (or stresses), the deformability (Elastic moduli) and strength of masonry or adobe structural elements. The Tube-jack testing method is used to detect the existing compressive stress in masonry elements. The tube-jack system consists of a number of tube-jacks connected in parallel, with an number of linear voltage displacement transducers measuring the displacement of the masonry near the line of the tube-jacks, that when inserted into holes drilled in a stressed masonry element, and inflated with a fluid like air, water or oil, expand to the size of the holes, and provide the necessary stress and displacement measurements to calculate the existing local compressive stress, the deformability and whenever possible, the strength of the masonry. This invention is characterized as being highly applicable to historical and heritage constructions containing masonry or adobe structural elements with large and irregular stone units and nonlinear mortar joints because of the method's use of small diameter tube-jacks that can be inserted in masonry joints, preventing damage to the historic masonry units in the inspection and diagnosis of the structure.

The present invention describes a ystem for mechanical testing of irregular masonry walls (1) comprising:

- a plurality of elastically inflatable tubes, herein referred as tube-jacks (2), suitable to be inserted into holes (11) of the wall (1) to be tested;

- pressure connectors (13);

- one or more pressure generators (14), connected through said pressure connectors (13) to the tube-jacks (2);

- a fluid inside the tube- jacks (2), pressure connectors (13) and pressure generators ( 14 ) ;

such that the pressure generator or generators (14) are able to inflate and expand diametrically the tube-jacks (2) .

In a preferred embodiment, the fluid is air, water or hydraulic oil.

In a preferred embodiment, the tube diameter is 20 - 40 mm.

A preferred embodiment further comprises displacement transducers (12) able to measure displacement of the wall (1) in the direction of the compressive stress caused by an expansion of the tube-jacks (2) .

In a preferred embodiment, the displacement transducers (12) are LVDTs. The present invention also describes a method for mechanical testing of walls (1) comprising the steps of:

- inserting a plurality of elastically inflatable tubes, herein referred as tube-jacks (2), into holes (11) of the wall (1) to be tested;

- connecting the tube-jacks (2) to pressure connectors (13) ;

- connecting the pressure connectors (13) to a pressure generator(s) (14);

- using the pressure generator (s) (14) to pressurize a fluid inside pressure connectors (13) and the tube-jacks (2), such that the tube-jacks (2) inflate and expand diametrically .

In a preferred embodiment, the fluid is air, water or hydraulic oil.

In a preferred embodiment, the holes (11) are positioned in the mortar between the masonry units.

In a preferred embodiment, the holes (11) are positioned in the path of the joints between masonry units, regardless of the straightness of the path.

In a preferred embodiment, the holes (11) are positioned in a path approximately linear and perpendicular to the assumed line of compressive stress in the masonry elements.

In a preferred embodiment, the holes (11) are positioned 50

- 125mm apart.

A preferred embodiment further comprises the steps of :

- placing displacement transducers (12) on either or both surfaces of the wall (1), able to measure displacement of the wall (1) in the direction of the compressive stress caused by the inflation of the tube- jacks (2);

- measuring the displacement of the wall (1) and the pressure applied to the tube- jacks (2), on one or more times ;

- calculating mechanical parameters of the wall (1) with the displacement and pressure measurements.

A preferred embodiment further comprises the steps of :

- placing the displacement transducers (12) on the surface of the wall (1) before the holes (11) for inserting the tube-jacks (2) are made;

- measuring the displacement of the wall (1) before the holes (11) for inserting the tube-jacks (2) are made;

- inserting the tube-jacks (2);

- increasing the pressure applied to the tube-jacks (2), until the displacement of the wall (1) equals the displacement of the wall (1) before the holes (11) for inserting the tube-jacks (2) were made;

A preferred embodiment further comprises the steps:

- inserting a plurality of tube-jacks (2), into holes (11) of the wall (1) to be tested, positioned along two approximately linear and approximately parallel paths, perpendicular to the assumed line of compressive stress in the masonry elements;

- measuring the displacement of the wall (1) by the displacement transducers (12) placed perpendicular-to and between the two lines of holes (11), when increasing the pressure is applied to the tube-jacks (2);

- calculating mechanical parameters of the wall (1) with the displacement and pressure measurements. In a preferred embodiment, the displacement transducers (12) are positioned approximately perpendicular to the line of tube-jacks (2) and parallel to the assumed direction of compressive stress in the masonry elements.

In a preferred embodiment, the displacement transducers (12) are LVDTs.

In a preferred embodiment, the tube diameter is 20 - 40 mm.

In a preferred embodiment, the holes (11) are through holes (11) ·

BACKGROUND ART

Masonry structures of all types can fall into disrepair or become damaged by natural or human actions. In order to design the most appropriate and effective interventions necessary to preserve a masonry structure, determination of mechanical characteristics of the structural masonry elements is often necessary. If the masonry structure is of historic value, it is often the case that techniques which induce a minimal amount of damage to the structure are preferred in order to preserve as much of the irreplaceable structure as possible.

In the field of inspection and diagnosis, flat-jack testing is known as a relatively non-destructive technique among the various types of tests that can be performed on a masonry structure. The primary goal of conducting an in- situ flat-jack test is to determine the existing mechanical properties of the masonry such as the local compressive stress and deformability . Thus, this test is usually performed on structural elements such as walls and columns. The devices required for flat-jack tests are easy to move and use and it is possible to obtain results concurrently with the performance of the test.

However, there are disadvantages to using the flat-jack testing method with irregular masonry walls. When the flat- jack test is performed, a cutting device, such as a saw, makes a thin slit in the masonry element into which the flat-jack is inserted. Because of the length of normal sized flat-jacks (400mm), the stress distribution along the slit is non-uniform, with high stress peaks near the edges of the slit. This non-uniform stress distribution influences the accuracy of the flat-jack test results. In addition, this slit is usually cut in a horizontal mortar joint of a masonry element. Many masonry structures are built with stone pieces of various shapes and sizes. The randomness of the stone units results in an irregular construction pattern with mortar joints that are not in horizontal lines. Therefore, during a flat-jack test on an irregular stone masonry element, a number of masonry units may also be subject to unwanted partial damage. Due to these damages, additional repair to the masonry in the tested area will be required once the testing is concluded. Furthermore, utilization of the equipment used to cut the slit for the flat-jack can be cumbersome, and, at times, multiple cuts are required to attain a suitable opening to install the jack.

In order to solve these problems with flat-jack testing or create a new method for determining the required structural characteristics, several techniques have been presented in the past. The document JP58097636 refers to a simple flat- jack device used to determine the Young's modulus in concrete. The concept is the same as the previously described flat-jack where the jack is embedded in the concrete, a stress is induced in the concrete by inflating the jack with oil, and the measurements of the displacement of the concrete and pressure in the jack can be used to determine the Young's modulus. This device and procedure have the same issues as previously described by the flat- jack and also do not solve the issue of damaging masonry units during a test on irregular masonry.

A second document, CN101419143, refers to a device that can perform a bidirectional composite stress loading test on a brick body. While this may be useful for determining the characteristics of a single masonry unit, it does not solve the issues related to determining the stress in a structural masonry element and does not provide a method that produces limited damage on the masonry units.

The document ITRM960219 refers to a cylindrical jack that can be used to determine the modulus of elasticity of the masonry. The method uses a diamond coring machine to make the first hole in the masonry. This device consists of a tube with a rigid layer and flexible layer. Oil or another substance is pumped into the flexible layer. The deformation of the masonry between the two layers is measured to determine the modulus of elasticity. This differs from the present invention in that in this ITRM960219 document the masonry deformation is measured between the two cylindrical layers of the cylindrical jack whereas in the tube-jacks of the present invention, the fluid is pumped into the interior of the tubes and the deformation is measured on the surface of the masonry and in between the lines of tube-jacks for the determination of the modulus of elasticity. With the cylindrical jack method of ITRM960219, the coring and drilling must be done in the stone units and the test is localized to the cored material. Thus, this technique of ITRM960219 does not solve the issue of protecting the masonry units and is too localized to determine the modulus of elasticity of the masonry composite material.

DISCLOSURE OF THE INVENTION

The present invention comprises both an in-situ testing method for determining mechanical characteristics of any kind of masonry (i.e., masonry with regular or irregular units and mortar joints) and the developed jacking component of the system, the tube- jack. The tube- jack component consists of a tube closed at one end and fitted with a connector at the other end (See #2 in Figure 5) . When injected with air, water or oil through the connector end, the tube is able to inflate elastically - and expand diametrically. The use of air is preferable to water or oil because of its cleanliness in the case that the tube fails.

Thus, the tube-jack consists of a hollow device that is filled with a fluid that can be pressurized and used to inflate the space and induce a pressure on the surrounding material. The tube-jack differs in equipment compared with flat-jack. The flat plate, pressurized with oil, in the flat-jack system is replaced with a desired number of tubes, with the possibility of pressurization with air or an alternative fluid, in the tube-jack system. The utilization of tubes on irregular masonry walls eliminates the need to create straight slots which may cause partial damage to the masonry units and a high undistributed stress along the slot. Additionally, the tube- jacks inserted into the holes can be instrumented with strain or other deformability sensors at different positions, allowing the collection of information about the contact stress distribution throughout the length of the hole. The new system allows for the testing of multi-leaf walls (i.e. walls compose by different stone arrangements in the external surfaces and a different internal core) because the holes can be done in the complete thickness of the walls. It also produces less drastic changes in the stress distribution around the openings and leaves less damage on the tested area, which is the most desirable advantage of this system.

The tube-jack testing system consists of a number of tube- jacks - diametrically expandable - connected in parallel; an equal number of LVDTs (linear voltage displacement transducers) or other similar transducers available in the art; an air compressor, water or oil pump; and a data acquisition system, as shown in Figure 3. When the tube- jacks are inserted into holes drilled in a stressed masonry element and the tube-jacks are inflated to fill and expand the size of the holes, the stress in the masonry element can be determined based on displacement and pressure measurements collected by the transducers and recorded by the data acquisition system. Various lengths of tube-jacks can be employed in the system to span the width of the wall section. This ability to test the complete section of the wall is an improvement over the flat-jack testing methods. Drilling is according to an embodiment a preferred method but other suitable ways to create a hole ih a wall may be used, dependant on wall materials, thicknesses, etc... The first step in the tube-jack testing method is positioning the holes and measuring the initial distance between target points on the masonry wall and between the holes. The following task is drilling the holes in the masonry element where the tube-jacks will be inserted. The holes are drilled in the mortar between the stone units and can be located simply by following the path of the joints regardless of the straightness of the path as shown in Figure 1. In the case of adobe walls, the holes can be at the most convenient points, without any specification. The line of tube-jack holes should be substantially perpendicular to the assumed line of compressive stress in the masonry element, for optimum results. The tube-jack system permits the freedom to follow the path of the joints and eliminates the need to cut in inappropriate locations and damage the masonry units (See Figure 2) . This is one of the most significant innovations. Numerical analysis showed that it was appropriate to locate the holes at an equal spacing of approximately 50 to 125mm (but other distances may be appropriate dependant on materials, thicknesses, etc..) in order to ensure adequate space for drilling and placing of the tube-jacks and to have the tube-jacks close enough to each other to produce a relaxation of the masonry in the line of the tube-jacks for measuring the displacements .

LVDTs or similar transducers, used to measure the displacement of the masonry element before and after the tube-jack holes are made and during the inflation of the tube-jacks, are positioned on the surface of the masonry element in an embodiment approximately between the specified locations for the tube-jack holes. In another embodiment they are individually positioned along an approximately perpendicular line to the line of tube-jacks and parallel to the assumed direction of compressive stress in the masonry element (See Figure 4) . They shall be preferably installed prior to drilling the holes and beginning the test in order to measure the distances before the test begins. All of the used transducers, including those specified for measuring the pressure of the air, water or oil in the following sections, shall be preferably connected to the same data acquisition system, which can consist of a computer with hardware components connected by USB cables.

Displacement transducers are available in numerous formats and types - electrically resistive or capacitive, optical, ultrasound, etc... - any suitable to the purposes above described .

After positioning the holes, applying the LVDTs and drilling the specified number of holes, tube-jacks are inserted into the holes. It is recommended to insert the tube-jack immediately after drilling the holes and removing the mortar so that mortar surrounding the hole is not allowed to fill the hollow space. If additional deformation occurs after the tubes are placed in the holes, the flexibility of the tubes will bear the deformed shape of the cross-section of the hole. Thus, the tubes must be flexible, but strong enough to support high pressures. Tube diameters are preferably between 20 and 40 mm (but other diameters may be appropriate dependant on materials, thicknesses, etc..) . It is recommended that the test be conducted as soon as possible after formation of the holes so as to avoid material relaxation around the holes and compressive cracks, vertical cracks parallel to the direction of the compressive stresses. Following the insertion of the tube-jacks into the holes, air, water, or oil must be pumped into the tubes by means of conventional equipment. For example an air compressor can be used to pump air into and inflate the tube-jacks. All the tube-jacks are preferably connected in a parallel system and therefore will inevitably have the same internal pressure, but independent pumps may be used provided care is taken to ensure the pressure is substantially the same between tube-jacks. The pressure level can be controlled manually or automatically and is measured with a pressure gauge and/or transducer located between, or at, the tube- jacks and the pump/air compressor (See Figure 5) . The tube- jacks are inflated until distances between measured reference points on the surface of the masonry element, on either side of the jacks and in the direction parallel to that of the compressive stress where the LVDTs were placed, retain their original values before drilling, within a tolerance specified by the technician performing the test. The measured value of the pressure in the tube-jacks at this point can be used to determine the compressive stress in the masonry element.

The local compressive stress in the masonry element is approximately equal to the stress inside the tube-jacks and is determined using Eq. 1. Existing correction factors are necessary to obtain the actual stress inside the tube- jacks .

Eq. 1 depicts the formula used to calculate this stress (am) . am = Km Ka p ( 1 ) where, 0 < Km ≤ 1 is the jack correction factor (also known as calibration factor) , 0 < Ka ≤ 1 is the area correction factor, and p (psi or MPa) is the jack pressure required to recreate the original opening, as marked by the reference points, within the allowed tolerance. The jack correction factor is the ability of the tube to be inflated; with value of 0 representing a tube that cannot be inflated and a value of 1 representing a tube that can be expanded without any increase in pressure. This value is provided by the manufacturer.

The area correction factor must be calculated, e.g. by the operator. This value is determined by numerical parametric analysis in preliminary modeling of the tube-jack method and device. In this analysis the progressive opening of the hoses is simulated, as well as the tube-jacks inflating. The stresses in the wall and in the tubes and the displacements in the wall are measured until the initial state of stress was reestablished. The correction factor is obtained by dividing the applied pressure in the tube-jacks by the initial pressure in the wall at the moment of reestablishing the local stress in the wall. The value ranges between 0.7 and 0.85 for tubes with diameters of 2 to 4 cm when the tube-jacks are separated by 7.5 to 10 cm.

A similar procedure is carried out to determine the Young's Modulus of the masonry, the double tube-jack test. Following the completion of the previously described test for determining the stress in the masonry, the single tube- jack test, a second row of holes, in an approximately parallel mortar joint to the first row, is located and drilled. Tube-jacks are placed in both rows of holes and connected in parallel to the air compressor or water or oil pump. LVDTs are positioned perpendicular-to the tube- jack hoses and between the two lines of holes. Measurements of the displacements and pressures are recorded as the pressure in the tube-jacks is increased and pressure is subsequently applied to the masonry between the rows of tube-jacks. The load-displacement relationship is monitored during the test and used to determine the Young's Modulus and possibly extrapolate the compressive strength of the masonry. When the relationship becomes nonlinear, indicating the failure load is approaching, the test is stopped. Loading and un-loading cycles can also be performed .

Although elastically inflatable tubes are described in most embodiments as preferred, other embodiments will be possible making for example use of fluid-tight sleeves or even mechanically expanding wedges or anchors with expandable sleeves .

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures provide preferred embodiments for illustrating the description and should not be seen as limiting the scope of invention.

Figure 1 - Represents drilled holes (11) on a sample wall for a single tube-jack test.

Figure 2 - Represents general configurations for possible lines of holes (11) for tube-jack testing in irregular masonry

Figure 3 - Represents a general view of the Tube-jack testing apparatus including the tube-jacks inserted into the holes (11), LVDTs (12), connection tubes (13) and pump (14), and computer (15).

Figure 4 - Represents a close-up view of several devices of the Tube-jack system including the LVDTs (12), the tube- jacks (2) and connection tubes (13) .

Figure 5 - Represents a plan view of the tube-jack system set-up including a length of masonry wall (1), tube-jacks (2) inserted in holes drilled through the entire width of the wall, L and T-connectors for the piping system (3 and 4), pressure gauge (5), and connection (6) to air compressor or pump.

Figure 6 - Represents the modeled wall including boundary conditions and vertical loading .

Figure 7 - Represents the stress distribution in MPa over the length (distance in mm) of the modeled wall after cutting a 40cm slit for a flat-jack test.

Figure 8 - Represents the stress distribution in MPa over the length (distance in mm) of the wall after drilling 9 tube-jack holes over a length of 90cm.

Figure 9 - Represents the pressure-relative displacement relationship in the Tube-Jack models when there is a 100 mm distance between holes for various diameters and for two different Young's moduli of the walls.

Figure 10 - Represents the modeled regularly aligned brick masonry wall including isotropic brick and mortar elements .

Figure 11 - Represents the modeled irregular stone masonry wall including isotropic stone and mortar elements . Figure 12 - Represents the pressure-relative displacement relationship for the tube-jack test modeled in the irregular stone masonry wall .

MODES FOR CARRYING OUT THE INVENTION

For the purpose of demonstrating the tube-jack method and device, several exemplary embodiments were performed. The method of using a line of tube-jacks as an extended flat- jack was modeled with plane-stress elements in the finite element modeling program DIANA (DIANA, 2009). A simple wall of an isotropic material with mass density of 2000 kg/m3, Young's modulus of 1.5 GPa, and the Poison's ratio of 0.20; with dimensions of 3.22 m in width, 0.20 m in thickness and 2.815 m in height, was used for the model. A vertical uniform load of 0.4 MPa was applied to the top surface and the wall was simply supported at the base and free on all other sides, as shown in Figure 6.

The results indicated that the tube-jack tests produced smaller stress concentrations around the openings of the holes than the flat-jack test method produced, as shown in Figure 7 and 8. A reduction in the stresses at the edges of the holes means that the likelihood of damage in these locations will be decreased. Additionally, it was determined that the deformations following the drilling of the holes for the tube-jacks were of a much smaller magnitude than for flat- jack slits. Consequently, deformations during tube-jack tests require a higher sensitivity in the measurement devices, LVDTs. Overall; the models revealed that the tube-jack tests produced results for the stress concentration in the wall in the range of the theoretical value, 0.4313 MPa. Correction factors were applied to the resultant stress concentrations in the range of 0.75 to 0.83, based on various sizes of holes drilled in the wall from 0.2mm in diameter up to 0.4mm in diameter, to obtain the theoretical value, as shown in Figure 9.

Model embodiments were also constructed consisting of two isotropic materials, stone and mortar. One model consisted of regularly aligned brick masonry and the other model of irregularly shaped stone masonry. The brick or stone units had a mass density of 3000 kg/m3, Young's modulus of 50 GPa, and Poison ratio of 0.20. The mortar properties consisted of a mass density of 1800 kg/m3, Young's modulus of 5 GPa, and Poison ratio of 0.20. The masonry walls had a width of 2.50 m, thickness of 0.35 m and height of 2.55 m and were loaded with a distributed load equal to 14χ10^Λ4 N/m on the top of the wall to produce an average stress in the masonry of 0.40 MPa (the final stress state at the level of the tube-jacks also considered the self-weight of the wall), as shown in Figures 10 and 11. Based on pressure versus relative displacement plots, the resulting stresses at the level of the tube-jacks, produced by performing a phase analysis with these two models by varying the pressure in the tube-jack holes between 0 and 1 MPa, are very close to the theoretical values. In fact, correction factors were around 1.0 to 1.1 for both models. The pressure-relative displacement results are shown for the modeled irregular masonry wall tube- jack test in Figure 12.

The following claims set out particular embodiments of the invention .

Claims

C L A I M S

1. System for mechanical testing of irregular masonry walls (1) comprising:

a. a plurality of elastically inflatable tubes, herein referred as tube-jacks (2), suitable to be inserted into holes (11) of the wall (1) to be tested; b. pressure connectors (13) ;

c. one or more pressure generators (14), connected through said pressure connectors (13) to the tube- j acks ( 2 ) ;

d. a fluid inside the tube-jacks (2), pressure connectors (13) and pressure generators ( 14 ) ; such that the pressure generator or generators (14) are able to inflate and expand diametrically the tube-jacks (2) .

2. System according to claim 1 wherein the fluid is air, water or hydraulic oil.

3. System according to any of the previous claims wherein the tube diameter is 20 - 40 mm.

4. System according to any of the previous claims further comprising displacement transducers (12) able to measure displacement of the wall (1) in the direction of the compressive stress caused by an expansion of the tube- jacks ( 2 ) .

5. System according to any of the previous claims wherein the displacement transducers (12) are LVDTs.

6. Method for mechanical testing of walls (1) comprising the steps of :

a. inserting a plurality of elastically inflatable tubes, herein referred as tube-jacks (2), into holes (11) of the wall (1) to be tested;

b. connecting the tube-jacks (2) to pressure connectors ( 13 ) ;

c. connecting the pressure connectors (13) to a pressure generator(s) (14);

d. using the pressure generator(s) (14) to pressurize a fluid inside pressure connectors (13) and the tube-jacks (2), such that the tube-jacks (2) inflate and expand diametrically.

7. Method according to the previous claim wherein the fluid is air, water or hydraulic oil.

8. Method for mechanical testing of masonry walls (1) according to any claim 6 - 7 wherein the holes (11) are positioned in the mortar between the masonry units.

9. Method according to the previous claim wherein the holes (11) are positioned in the path of the joints between masonry units, regardless of the straightness of the path.

10. Method according to any of the previous claims 6 - 9 wherein the holes (11) are positioned in a path approximately linear and perpendicular to the assumed line of compressive stress in the masonry elements.

11. Method according to any of the previous claims 6 - 10 wherein the holes (11) are positioned 50 - 125mm apart.

12. Method according to any of the previous claims 6 - 11 further comprising the steps of:

a. placing displacement transducers (12) on either or both surfaces of the wall (1), able to measure displacement of the wall (1) in the direction of the compressive stress caused by the inflation of the tube-jacks (2);

b. measuring the displacement of the wall (1) and the pressure applied to the tube-jacks (2), on one or more times;

c. calculating mechanical parameters of the wall (1) with the displacement and pressure measurements.

13. Method according to the previous claim further comprising :

a. placing the displacement transducers (12) on the surface of the wall (1) before the holes (11) for inserting the tube-jacks (2) are made;

b. measuring the displacement of the wall (1) before the holes (11) for inserting the tube-jacks (2) are made ;

c. inserting the tube-jacks (2);

d. increasing the pressure applied to the tube-jacks (2), until the displacement of the wall (1) equals the displacement of the wall (1) before the holes (11) for inserting the tube-jacks (2) were made; e. calculating mechanical parameters of the wall (1) with the displacement and pressure measurements.

14. Method according to the claim 12 further comprising: a. inserting a plurality of tube-jacks (2), into holes (11) of the wall (1) to be tested, positioned along two approximately linear and approximately parallel paths, perpendicular to the assumed line of compressive stress in the masonry elements; b. measuring the displacement of the wall (1) by the displacement transducers (12) placed perpendicular- to and between the two lines of holes (11), when increasing the pressure is applied to the tube- j acks ( 2 ) ;

15. Method according to any of the previous claims 12 - 14 wherein the displacement transducers (12) are positioned approximately perpendicular to the line of tube-jacks (2) and parallel to the assumed direction of compressive stress in the masonry elements.

16. Method according to any of the previous claims 12 - 15 wherein the displacement transducers (12) are LVDTs .

17. Method according to any of the previous claims 6 - 16 wherein the tube diameter is 20 - 40 mm.

18. Method according to any of the previous claims 6 - 17 wherein the holes (11) are through holes (11).