mestrado em engenharia civil 2011 / 2012 - fenixeducristina/rrest/aulas_apresentacoes/07... ·...

Reabilitação e Reforço de Estruturas

Mestrado em Engenharia Civil

2011 / 2012

1/92011/2012

Eduardo Júlio

Reabilitação e Reforço de EstruturasAula 23.2: Conservação do Património.

Intervenção estrutural na Capela de S. Jorge de Aljubarrota.


1. INTRODUCTION

2. HISTORICAL SYNOPSIS

3. DESCRIPTION OF THE CHAPEL

4. RECENT INTERVENTION ON THE CHAPEL

5. DESCRIPTION OF THE STUDIES PERFORMED

6. DIAGNOSIS OF THE STATE OF CONSERVATION

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6. DIAGNOSIS OF THE STATE OF CONSERVATION OF THE VAULT

7. INTERVENTION


- Interventions on monuments should be performed with theonly objective of its conservation.

- Frequently, non-intervention or, at least, minimum

1. INTRODUCTION





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- Frequently, non-intervention or, at least, minimumintervention is considered to be the best option to achievethat purpose.

- The diagnosis of the state of conservation of the monumentand the correct assessment of its structural behaviour are,for this reason, extremely important.


7. INTERVENTION


In this communication, the structural intervention in the chapelof “S. Jorge de Aljubarrota” is presented.

The interest of this case study is due to the following unusual

1. INTRODUCTION





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The interest of this case study is due to the following unusualfacts:

(a) the existence of a severe hidden anomaly;

(b) the proposed irreversible intervention to safeguard themonument.


7. INTERVENTION


On the 22nd of October of 1383, Portuguese king D. Fernandodies. Being his daughter married to the Castilian king, it isinevitable that Portugal looses its independence.

1. INTRODUCTION





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7. INTERVENTION


Following this event, the people entitle D. João, “Mestre deAvis”, protector of the kingdom. Several battles take place untilthe mythical battle of Aljubarrota where, on the 14th of August of1385, Portuguese troops, commanded by general D. NunoÁlvares Pereira, defeat the Castilian troops.

1. INTRODUCTION





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7. INTERVENTION


With this triumph, D. João becomes theuncontested king of Portugal and, to celebrate thisvictory, he orders the erection of the monastery of“Santa Maria da Vitória” and founds the village ofBatalha.

1. INTRODUCTION





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7. INTERVENTION


D. Nuno Álvares Pereira orders the erection of the chapel of “S.Jorge de Aljubarrota” on the exact location where his standardwas placed, before the confrontation.

1. INTRODUCTION





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7. INTERVENTION


The chapel has a rectangular plant nave with a two slopewooden roof, connected to a quadrangular plant main-altar witha cross-vault.

1. INTRODUCTION





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7. INTERVENTION


Since the construction, the chapel has experienced severalinterventions and morphological changes. The most recentones are well documented1.1. INTRODUCTION





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1 - Mendonça, I, Capela de São Jorge de Aljubarrota, Inventário do Património Arquitectónico, 1991, http://www.monumentos.pt


7. INTERVENTION


Before 1872, although not registered, the interventions leftbehind revealing elements.

The key stone of the vault of the main-altar, richly ornamentedwith a pelican, symbol of D. João II, witnesses an interventionperformed during this period.

1. INTRODUCTION





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7. INTERVENTION


In 2003, due to a high state of degradation of the chapel, aninspection and diagnosis of the situation was performed byIPPAR (Portuguese Institute of the Architectural Heritage).

It was concluded that the state of the roof allowed the infiltrationof rain water, justifying the moisture spots visible at the vault,as well as at the chapel walls.

1. INTRODUCTION





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7. INTERVENTION


Also in 2003, IPPAR began conservation works on the chapel.

It was observed that the stone blocks of the vault exhibited ahigh state of degradation.

It was decided to abort this operation and to cover again theareas where the cement mortar had been removed.

1. INTRODUCTION





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areas where the cement mortar had been removed.5. DESCRIPTION OF THE STUDIES PERFORMED


7. INTERVENTION


Following the previously described situation, it was decided toperform studies:

(a) to determine the cause of the observed anomaly;

1. INTRODUCTION





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(b) to characterize the state of conservation of the vault;

(c) to evaluate the structural stability of the latter; and

(d) to propose an intervention to safeguard the monument.

PERFORMED


7. INTERVENTION


Electromagnetic prospecting and electric resistivityprospecting

1. INTRODUCTION





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PERFORMED


7. INTERVENTION

These works indicated that the chapel is situated on a claylayer that, being impermeable, facilitates water accumulationon a superficial layer of clayey sandstone with coble stones.


1. INTRODUCTION





Electromagnetic prospecting and electric resistivityprospecting

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This fact associated with the use of high porosity materials in the walls promote the presence of rising damp by capillarity in the monument.

PERFORMED


7. INTERVENTION


In situ testing of temperature and moisture

For the measured values of relative humidity and temperature,water condensation on the walls is possible to occur, for atemperature reduction to 18-19 ºC.

1. INTRODUCTION





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PERFORMED


7. INTERVENTION


State of conservation of the vault

Three soundings were conducted at the base, followed by avisual inspection using an endoscope.

1. INTRODUCTION





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PERFORMED


7. INTERVENTION


Geological characterization of the stone from the vault

It was not possible to analyse thin plates of the removedmaterial since it did not present the necessary cohesion. Forthis reason, only a mineralogical analysis by X-ray diffraction ofthis sample was performed and compared with a sampleremoved from the main door pediment.

1. INTRODUCTION





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0 10 20 30 40 50 60

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1000

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3000

4000

5000

6000

7000

8000

9000

10000

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amostra da lama da sondagem amostra do frontão da porta

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PERFORMED


7. INTERVENTION


Geological characterization of the stone from the vault

Comparing samples it was possible to conclude that limestoneof identical composition was present in both, composed byCalcite (CaCO3), Quartz (SiO2) and traces of clayey minerals.

1. INTRODUCTION





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Calcite (CaCO3), Quartz (SiO2) and traces of clayey minerals.

There was not found any salt in both samples. Themacroscopic analysis of the samples allows to state that thismaterial is a white limestone, dominantly oolitic.

PERFORMED


7. INTERVENTION


Mechanical characterization of the stone from the vault

Samples obtained from healthy blocks placed near the chapelduring the intervention in 2003 were tested on a universaltesting machine, registering an average value of 58 MPacompressive strength.

1. INTRODUCTION





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PERFORMED


7. INTERVENTION


Structural stability of the chapel

This was analysed with a commercial finite element software,considering the structure subjected to the static action of itsdead weight and also when subjected to a seismic action,determined according to the Portuguese safety code (RSA).1. INTRODUCTION





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PERFORMED


7. INTERVENTION


Structural stability of the vault

The most conservative scenario was considered,corresponding to total lost of cohesion and strength of thestone blocks of the vault.

The analysis was performed only considering the cement

1. INTRODUCTION





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The analysis was performed only considering the cementbased mortar, covering the intrados of the vault with an averagewidth of 30 mm, and the visible part of the stone nervures asstructural material.

PERFORMED


7. INTERVENTION



Considering the isolated action of the dead weight of thestructure, the level of stresses is, generally, of smallimportance.

In the case of the highest compression stresses, ofapproximately 2.5 MPa, this can probably be assured by themortar layer.

1. INTRODUCTION





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Envolvente das tensões principais σ1 na face exterior, considerando E=1.0 GPa.

mortar layer.PERFORMED


7. INTERVENTION



Maximum tension stresses of 1.5 MPa, should indicate crackingthat can not be observed, until now, in place. The self-sustaining capacity of the vault is, so far and somehow,assured.

1. INTRODUCTION





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Envolvente das tensões principais σ3 na face interior, considerando E=1.0 GPa.

PERFORMED


7. INTERVENTION



At the envelopes of principal stresses, σ1 and σ3, for thecombinations of actions considering the seismic action, it canbe observed, as expected, significant increase of the maximumvalues of tension and compression principal stresses.

1. INTRODUCTION





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Envolvente das tensões principais σ1 na face exterior, considerando E=1.0 GPa.

PERFORMED


7. INTERVENTION



For instance, it can be observed that tension stresses of around5 MPa can occur at the inner layer of mortar, which, evidently,can not be resisted by this material.

1. INTRODUCTION





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Envolvente das tensões principais σ3 na face interior, considerando E=1.0 GPa.

PERFORMED


7. INTERVENTION


(1) The chapel was subjected to rain water infiltrationsthrough the nave roof and the vault of the main-altar during long period(s) of time;

(2) The chapel is erected on a little permeable ground,

1. INTRODUCTION





6. DIAGNOSIS OF THE STATE OF

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(2) The chapel is erected on a little permeable ground, facilitating the accumulation of rain water at the surface, which is favourable to the presence of rising damp by capillarity at the chapel walls;

(3) The cement based mortars, applied in previous interventions on the walls and on the intrados of the chapel vault, contributed probably to prevent these elements to expel the water infiltrated or adsorbed;


7. INTERVENTION


(4) From the numerical modelling of the structural behaviour of the chapel, it is licit to conclude that the vault still has part of its self-sustaining capacity;

(5) In the case of changes in the hygrothermic conditions of the

1. INTRODUCTION





6. DIAGNOSIS OF THE STATE OF

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(5) In the case of changes in the hygrothermic conditions of the vault, the state of degradation of the stone can develop and reach the limit situation assumed in the numerical simulation, which would imply the collapse of the vault;

(6) From the dynamical analysis, it also results evident that the stress increase introduced by an intense earthquake will imply the collapse of the vault.


7. INTERVENTION


(1) Opening of “windows” on the cement based mortar of the intrados of the vault to characterize the state of degradation of the stone material at the surface;

(2) Soundings to evaluate the state of degradation in depth.

1. INTRODUCTION






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(2) Soundings to evaluate the state of degradation in depth.

(3) In the case of generalized degradation of the stone, at the surface and in depth, the substitution of the blocks of the main-altar vault is, in this case, the correct option, i.e. the one that best safeguards the monument.


7. INTERVENTION


1. INTRODUCTION






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7. INTERVENTION


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7. INTERVENTION


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7. INTERVENTION


Reconstruction

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7. INTERVENTION


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Reconstruction

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7. INTERVENTION


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Reconstruction

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Reconstruction

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7. INTERVENTION

mestrado em engenharia civil 2011 / 2012 - fenixeducristina/rrest/aulas_apresentacoes/07... ·...

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