WALL FIBBER GLASS REINFORCEMENT- 7th Int. Mansonry Conf-Enviado Finalmente

7/27/2019 WALL FIBBER GLASS REINFORCEMENT- 7th Int. Mansonry Conf-Enviado Finalmente

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7th International Masonry Conference - 2006Masonry restoration, repair, rehabilitation and refurbishment

FIBREGLASS REINFORCEMENT IN

BRICK BEARING WALLS

BY

Prof. Arch. G. VALLETTA*Prof. Arch. G. PEDEMONTE*

Arch. J. J. FONTANA** University of Uruguay -.Faculty of Architecture Institute of Construction Science.

E-mail: [email protected]. Ing. Q. R. TALERO2*

Dr. Ing. Q. A. DELGADO2*

2*Inst. C.C. Eduardo Torroja-CSIC-Spain;E-mail: [email protected]

ABSTRACTThe present article addresses the viability of reinforcing brick walls with non-traditional materials such as

fibreglass.Inasmuch as the development of this technique is still in the research stage world-wide and practical building

experience is scant, strength tests were conducted on specially designed specimens made of recycled demolitionbrick dating from the early 20th century. The experiments were run as specified in Spanish standard UNE-EN1052-1 (April 1991i).Of the various fibre reinforcement systems, the type analyzed here consisted in composite materials made from

carbon fibre or fibreglass fabric and structural adhesive epoxy resins. The use of fibreglass reinforcement inrubble walls was studied in the context of local construction practice, materials, mortar and procedures.

1. HISTORY

Many thousands of square metres of buildings were erected in the River Plate countries in the period runningfrom approximately 1860 to 1930. The construction technique used, similar throughout the period and across theregion, underwent only minor variations that if anything highlighted its characteristic features, generating social,architectural and town planning repercussions that endowed the urban fabric with a very distinctive personality.With the economic bonanza of the following decades, the general rise in the standard of living, the appearance ofnew technologies and changing tastes respecting where and how to live, cities such as Montevideo and others inUruguay and Argentina witnessed the migration of their populations from existing quarters fitted with all thenecessary services to other areas. Cities began to sprawl and the urban profile of some quarters changed dueeither to the erection of new buildings or the neglect of existing neighbourhoods, which eventually deterioratedinto slums. This process, which has been going on in Montevideo for many years, was intensified by the

recession ensuing from the loss of markets for the countrys traditional products such as beef, leather, cerealsand so on. As a result of these developments, very briefly summarized here, a number of Montevideos quartersare completely run down and in some cases, such as in the inner city, afflicted by delinquency or populated bynon-family or otherwise complex groupings.While housing and retail establishments continued to sprout up in the rest of the city, these quarters remained

isolated and ignored by individuals and investors as possible construction sites. Fortunately, for some years now,attention has been focused on these buildings for economic, social, architectural and town planning reasons. Thishas been the case of the Reus and Palermo quarters, and recently in the old or inner city. A significant movementis afoot to revalue the buildings from that period. This is very important from the economic standpoint for thereuse of existing buildings, from the social standpoint because it revitalizes a social groups identification with itstimes, and from the architectural and town planning standpoints because it rebuilds the urban fabric with samplesof all the building styles known to the area since it has been inhabited by human beings.

Insert Figure 1, 2 and 3 here

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mailto:[email protected]:[email protected]:[email protected]:[email protected]


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This process has been greatly favoured by the recent tendency to conserve the national heritage, as well as bythe groups engaging in this endeavour and the courses, congresses and conferences on the subject. As isnormally the case in architecture, the process has no single point of origin but is the result of the convergence ofthe interests of private citizens, official sensitivity to the issue, and the concerns of engineers; there can be nolinear or continuous process without all three of these elements.The need has thus been felt to stress the importance of the issue and put forward a procedure for intervening in

this type of buildings with a clear understanding of how they were built and utmost respect for their structuralinteractions. In the second half of the nineteenth and the early twentieth century, the River Plate countriesbenefited from an inflow of Italian, Spanish and French immigrants with high professional and in some caseseven financial status, drawn by a continent in bloom, with recently or reasonably consolidated republics. Amongthem were very highly qualified engineers who left their imprint on both shores of the Plate, such as M. Palanti(Barollo Building in Buenos Aires and Salvo Building in Montevideo) or Luigi Andreoni in Uruguay, to mention onlytwo of the many disembarking on that part of the world.This study broaches the typology used both in small to medium-sized single family housing and in larger

buildings, initially designed as large-scale dwellings that could be used today to house public or private, cultural,administrative or educational facilities.Figures 1 and 2 shows the standard floor plans for double- or single-span portal frame housing. The typical

facades are visible in the photographs and depicted in Figures 3 and 4, along with a cross-section showing thestructural layout: bearing walls, foundations, orientation of the vaulting in the roofs of single storey homes and theinter-storey flooring in multiple storey buildings, visible in the photographs of houses in the inner city originally

occupied by the most well-to-do families.

2. STRUCTURAL DESIGN

Generally speaking, the structural design consists in linear loads on bearing walls built with traditionallymanufactured brick and mortars containing little or no cement (clay in some cases), with linear foundations ofvolumes of stones sunken in mortar and steel beams for non-bearing walls. The construction-structural system isdepicted in Figure 9, where the bearing walls are shown as thick lines. Roofs are usually designed as rows ofshallow vaults made with hollow fillers or three or four clay bricks forming arches. The fillers or bricks rest on steeldouble-tee joists with a total height of 140 mm and wings measuring 60 mm spaced at approximately 70-cmintervals. The joists rest, in turn, are supported by the bearing walls, which usually include the facade, the firstwall parallel to the facade and a perpendicular wall, as shown in Figure 9. This same scheme is repeated in largerbuildings. In older or less expensive buildings the joists are made of wood instead of steel. These members arenormally covered with a sub-flooring consisting of lime mortar containing ceramic rubble, on which the finished

flooring fired clay tile or wood is laid, supported by guides made of the same material or of the clay tile usedas finish flooring on the roof deck.

Insert Figure 4, 5, 6 and 7 here

Since the construction system was similar in single family housing and rental flat buildings or structuresdesigned for other purposes and the reasons for and consequences of desertion were the same, the samepathologies are invariably found when the buildings are studied for reuse. The defects due to neglect revolveprimarily around the inflow of rainwater with all that involves in terms of the deterioration of the rusted steel joistsin roofs and inter-storey floors and the concomitant loss of bearing capacity. The changes in the adjacent lotsgenerate additional problems, namely:

1) Larger built areas and therefore lower soil evaporation rates.2) Heavier loads, placing the terrain under greater stress.3) Heavier traffic on adjacent streets, with an increase in aggressive exhaust gas and vibration not

originally present, and so forth.

Insert Figure 8 and 9 here

Other problems often found in conjunction with the above include the change of original purpose andconsequential variations in live loads: when industrial buildings are converted into housing the live loads involvedare smaller, but when buildings originally designed as housing are refurbished for use as educational or culturalfacilities, their bearing capacity must be increased to accommodate the live loads for public buildings specified inthe existing legislation.

2.1 RESTORATION

The structural reconsolidation project to make these buildings able to be used again presents two fundamentalaspects:Two main considerations must be addressed when rehabilitating these buildings:

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2.1.1 When the original purpose is maintained replace or restore the bearing capacity of deterioratedmembers. Where the members are to be replaced, the new members must be designed to the originalspecifications of the part replaced, namely its bearing capacity, strain and plasticity, to avoid the generation ofstress that would do more harm than good, or the appearance of situations that might compromise the rest of thestructure due to differential expansion or contraction. The type of structures described exhibits extremely elasticbehaviour and involves the interaction of many members of different characteristics that constitute a complexwhole, with components made of iron, clay masonry units, mortar and so on. Moreover, such structures, havingbeen in place for over 70 or 80 years, have settled undergone deformation and adopted the positionscorresponding to the loads borne.

2.1.2. In the event of a change in purpose that entails an increase in live loads, any action must betaken with extreme care, since the existing parts must be reinforced or new structural members added. This callsfor verification of the performance of the existing members when subjected to new stress as a result of the newloads, which, like the original moments, should preferably be distributed. Where loads exceed the allowablestress the reinforcement or addition of new structural members must be as un-aggressive as possible.In the past (particularly in the nineteen sixties and seventies), interventions of this nature in the region or in

Europe often caused irreparable damage due to the use of materials exhibiting behaviour that differedsubstantially from that of the original members, but which were in vogue at the time: reinforced concrete or heavyrendering with a high percentage of cement or acrylic paint, for instance. Today, fortunately, the use of materialsdifferent from those existing in a structure is not recommended, for technology has at least brought an awarenessof the limitations of current knowledge; in other words, it is generally recognized that since there is presently no

way of knowing how certain materials might react, experiments should not be conducted in existing buildingswithout a full understanding of their short- and long-term effects.This is an enormous step forward in the attitude of structural engineers toward standing historic or heritage

buildings. The University of the Republic of Uruguays Faculty of Architecture has begun to experiment withreinforcing bearing walls using nineteenth century brick specimens from demolition works with differentmaterials (fibreglass and others); similar experiments are also underway in several European universities withwhich the faculty has been exchanging experiences and findings. Moreover, thanks to recent computer software,structures can be modelled by varying the behavioural conditions to find the ones that most closely simulate thecracking found in a given building, thereby identifying the most plausible hypothesis with respect to the underlyingpathology.Consequently, new technologies should enable researchers to analyze new materials and systems prior to

deploying them in buildings without being certain of their actual behaviour once in place.

3. EXPERIMENTAL PROCEDURES

The potential for the use of fibreglass in the construction industry, particularly as reinforcement, lies in its lightweight, resistance to rust and deterioration and ease of use with the concomitant savings in labour.In light of the high cost of such fibres, the qualities and quantities used must be rationalized on the grounds of

technical and economic performance as compared to better known and widely employed traditional solutions.In this regard the use of a technology with certain advantages over traditional reinforcement systems, based on

the properties of the material involved, regarded to date to be inalterable and shown to be worksite-friendly, maylower both rehabilitation costs and maintenance expenses during the service life of the structure.

3.1 BACKGROUND

Composite materials made from carbon fibre or fibreglass fabric and structural adhesive epoxy resins areamong the categories of fibre reinforcement technologies. Since experience with their use in construction is stillscant and their many applications have given rise to a good deal of research, the state of the art is still in themaking. International recommendations stress the need to verify design methods with tests and trials.No domestic experiments have yet been run in Uruguay to test fibreglass fabric reinforcement in bearing rubble

walls. On the contrary, national studies have been run on the application of carbon fibre which has some of thesame properties as fibreglass in reinforced concrete structures.The experience acquired in other countries endorses such applications. And the advantages and drawbacks to

the use of fibreglass in bearing wall reconstruction and rehabilitation have been discussed in numerous congresspapers. No system is intrinsically good, however, until the actual possibility of applying it in a specific environmentcan be verified.The present study aimed to analyze the application of fibreglass reinforcement technology to traditional rubble

walls under the conditions existing in Uruguay as regards type of materials, mortars, rubble and buildingprocedures.

3.2 DEVELOPMENT AND ANALYSIS

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The procedure adopted by the Institute of Construction Science (ICS) was to conduct tests on rubble specimensmade with brick retrieved from demolition works.While this approach lays no claim to statistical validity, it did make it possible to empirically validate the initial

hypothesis and ratify the relevance of pursuing this line of research.The initial hypothesis was that specimens should perform better under stress when one of their surfaces is

reinforced with fibreglass. This hypothesis was confirmed for bending strength, as the results discussed belowshow.

3.3 TESTING

The strength of un-reinforced controls as well as fibreglass-reinforced specimens was determined as set out inSpanish standard UNE-EN 1052-1 (April 1991).Both compression and flexural strength tests were conducted.The trials were run at the ICS Laboratory, Faculty of Architecture, University of the Republic.

The characteristics of the materials used are given below:

Type of rubble: 5 x 14 x 20-cm recycled brick, dating from 1909.Source: recycled housing, Montevideo, Uruguay.

Mortar dosage: (sand Portland cement lime) 5 -1 - 1Characteristics of the specimens tested:

3.3.1 COMPRESSIVE STRENGTH

Insert Figure 10 and Table 1 here

3.3.2. FLEXURAL STRENGTH

Insert Table 2 hereInsert Figure 11 and 12 here

3.4. CONTROL (un-reinforced) SPECIMEN TESTS

3.4.1. a COMPRESSIVE STRENGTH (no reinforcement).

Mean compressive strength: f (daN/cm2) = 37.42

3.4.1. b FLEXURAL STRENGTH (no reinforcement).Flexural strength tests along a plane of rupture parallel or perpendicular to the joint. The results show:

3.4.1. b.1 Flexural strength along a plane of rupture perpendicular to the horizontal joints: Mean flexuralstrength: fm (daN/cm

2) = 10.49

3.4.1. b.2 Flexural strength along a plane of rupture parallel to the horizontal joints: Mean flexural strength: fm(daN/cm2) = 3.21

These figures were taken as the baseline data or the rupture values for structurally strong members made ofclay brick laid in mortar. The purpose was to reinforce these members either to bear the larger loads ensuingfrom a new use for the building or to restore the structural strength lost in members no longer serviceable due tocracking, for whatever reason. The bricks and mortars were also tested separately.The aim was to quantify how far allowable loading could be increased without compromising the structure.The same types of specimens, reinforced with fibreglass on one or both sides, were tested for compressive and

bending strength as specified in the above standard. The results were as follows:

3.5. REINFORCED SPECIMEN TESTS.

3.5.1. a. COMPRESSIVE STRENGTH (with reinforcement on one or two sides)

3.5.1. a.1 Specimens reinforced on one side:

Mean compressive strength: f (daN/cm

2

) = 41.89

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3.5.1. a.2. Specimens reinforced on both sides:

Mean compressive strength:f (daN/cm2) = 39.75

Given that the increase in strength was found to be nil or practically nil under these conditions, work has begun

to design conditions able to capitalize on the merits of the solution, in particular in light of the flexural strength testresults.3.5.1. b. BENDING STRENGTH (reinforcement on the loaded side)3.5.1. b.1 Flexural strength along a plane of rupture perpendicular to the horizontal joints:

Mean flexural strength: fm (daN/cm2) = 30.28

3.5.1. b.2 Flexural strength along a plane of rupture parallel to the horizontal joints:

Mean flexural strength: fm (daN/cm2) = 6.19

4. CONCLUSIONS

There is a significant increase in capacity of resistance strength, i.e., the contribution made by the

reinforcement adhered to the specimen, was with respect to the bending moment and extension stress.Figures 20 and 21

It is the shear stress, when exceeding the limit tension strength of the rubble specimen that caused the

structural members to break. It is this stress that causes most of the fissures in walls, as we can see infigures 13 and 14, where we already tested the capacity of reaction in situ.

This phenomenon causes the cracking in walls, either because it is in excess of the materials

compressive stress so it pushes outside the volume of the wall or of the specimen, beginning the sheareffort growing the values till them overpass the limit of tensile capacity.

So this is the behaviour under flexural or buckling strength.

The problem is to be able to reconstruct the theory conditions of reinforcement in the work-site, in the

real work.

Insert figures 13 to 21

5. FUTURE ACTION

Consequently, the challenge is to seek worksite-feasible solutions or procedures for applying the

reinforcement and repeat the tests under those conditions.

The complications likely to appear when using the material tested here primarily its reaction with the

mortar as well as other aspects such as ageing, weathering and so on, should also be studied.

Other tests should be conducted with non-organic fibres (plastic, aramide and similar).

Finishes should also be tested for suitability: paint, sprayed material, rough-coating and so on.

Although funding to continue this work has not yet been forthcoming, the research team is persuaded that it can be

raised. The issue addressed is acquiring importance due to the need for new technologies to recycle, restore and/orrehabilitate existing buildings either for their historic value or with a view to the possible reutilization of housingsolutions.

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Figure 4 and 5- Prototype of single or doublecorridor

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Figure 1, 2 and 3- Urban fabric inquarters and the inner city

saln

dormitorio

dormitorio

cocina

bao

escritoriosaln

dormitorio

dormitorio comedor

cocina

bao

Figure 7- Section

Figure. 6- Facade and perspective


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Figure 9- Structural typology

Figure 8- Vaulting


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No. of specimens: 4

General description of specimens:Prismatic,

Length: 2 bricksDepth: 1 brickHeight: 8 courses

Joint height/width: 1.0 to 1.5 cmBond: coursed

Rtulos: Longitud Length;Espesor depth; Altura height

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Figure 10 specimen for compression tests

Table 1 specimen for compression tests


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Stress perpendicular to joints. Stress parallel to joints.

No. of specimens: 5 No. of specimens: 5


Length: 3 bricksHeight:: 1 brickDepth: 5 courses



Length: 8 coursesHeight: 1 brickDepth: 2 bricks


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Table 2 Flexural Strength

Figure 11 Stress perpendicular to joints Figure 12 Stress parallel to joints

Figure 13 and 14 Walls reinforced with fibber

Figure 15 Beginning of compressionbeginning

Stress perpendicular to joints

Figure 16 and 17 Compression results: Fissuresbeginning

Stress perpendicular to joints


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WALL FIBBER GLASS REINFORCEMENT- 7th Int. Mansonry Conf-Enviado Finalmente