6. Tipos Compuestos 55
6.3. Registros o Estructuras
2-2-1- Mechanism of break down in stone building:
The main types of failure in stone buildings are as followed:
• Mode (I): Failure due to the collapse of the façade.
• Mode (II): Failure due to the wall bending.
• Mode (III): Failure due to the wall cut.
• Collapse on the isolated walls.
2-2-1-1- Mode (I): Failure due to the collapse of the façade:
This type of failure happen when separation of the façade due to the motion that involves one or more of structure panels of the building at the upper floors of the construction.
Fig (2-16) photo and diagram of the Failure due to the collapse of the façade.
Fig (2-17)photos of building at “Messina, Sicily”
after the earthquake (28 December 1908).
Fig (2-18) photo the cracks in the connection between the façade and the building.
2-2-1-2- Mode (II): Failure due to the wall bending:
This type of failure happen due to frontal cracks in the façade that causes separation of one part or more of the walls then collapse of the central zone of the wall at the form of (V shape) at the upper part of the façade.
The Italian Architecture in Alexandria, Egypt (the conservation of the Italian residential buildings)
Part (2): Theoretical study ____________________ Chapter (2): Structural failure and interventions in stone building
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53
Fig (2-19) photo and diagram of the Failure due to the wall bending.
Source: (lecture by Prof. T. Panzeca, at Kore university of Enna, Italy).
Fig (2-20) photos of buildings at “Messina, Sicily” after the earthquake (28 December 1908).
Source: http://www.grifasi-sicilia.com/messina_terremoto_1908_porta_messina_gbr.html
2-2-1-3- Mode (III): Failure due to the wall cut:
This type of failure happen due to separation of the wall and rotate it out side around the lower edge leaving the panels and the building and causes collapse in the façade.
Fig (2-21) photo and diagram of the Failure due to the wall cut.
Source: (lecture by Prof. T. Panzeca, at Kore university of Enna, Italy).
Fig (2-22) photos of buildings at “Messina, Sicily” after the earthquake (28 December 1908).
Source: http://www.grifasi-sicilia.com/messina_terremoto_1908_via_porta_imperiale.html
2-2-1-4- Collapse on the isolated walls:
This breakout in walls mainly occurs in presence of an excessive load and/or additional tension that is created when the foundations is subjected to motion or settlement, It appears as 45° cracks on one or both sides of the walls. The stability of the structure in this case is depending on the relation between the length and the dimension of the cross section. This phenomenon is often tied to the non homogeneity of the building system (stone and mortar).
Fig (2-23) photos of Collapse on the isolated walls.
Source: (lecture by Prof. T. Panzeca, at Kore university of Enna, Italy).
Fig (2-24) photos of cracks on the isolated walls due to over loading or foundation movement.
Source: (lecture by Prof. T. Panzeca, at Kore university of Enna, Italy).
The Italian Architecture in Alexandria, Egypt (the conservation of the Italian residential buildings)
Part (2): Theoretical study ____________________ Chapter (2): Structural failure and interventions in stone building
___________________________________________________________________________
55
2-2-2- Structural improvement integrations in stone building:
Interventions improvements are required in stone building due to the damage level, it’s place and the structural element that require intervention and some of the basic intervention are listed below:
2-2-2-1- Reinforcement of the structure with steel:
Using steel bars to reinforcement the stone structure is a traditional process as seen in some of the ancient building. But sometimes it causes a serious damage to the stone due to the corrosion of the iron bars that leads to increasing of its volume causing cracks in the stones.
Fig. (2-25) photos and sketch of using steel bar in ancient buildings.
Source: (lecture by Prof. T. Panzeca, at Kore university of Enna, Italy).
Fig. (2-26) photos of the corrosion of old steel bars that damage the nearby stones.
Source: (Restoration project of “Rampenseri castle, Sicily, Italy by Prof. T. Panzeca).
So it is recommended to use steel bars inserted inside a (PVC tubes) that prevent direct contact between steel and stone also make it possible to maintain the steel when necessary.
The steel bars inserted at the corners of the building in the top of the outer walls and connected with steel plates and bolts as seen in Fig. (2-?).
Fig.(2-27) Sketches of using steel bar inserted at the corners of the building inside (PVC tubes) and connected with steel plates and bolts . Source: (lecture by Prof. T. Panzeca, at Kore university of Enna, Italy).
Fig. (2-28) photos of the steel bars inserted at the top corners of outer walls and the connection with steel plates and bolts. Source: (Restoration project of “Rampenseri castle, Sicily, Italy by Prof. T. Panzeca).
In cases of deferent thickness in the walls the bars are connected throw intermediate plate and the cables are inserted in two levels
Fig. (2-29) photos of using steel bar in case of deferent thickness in the walls.
Source: (Restoration project of “Rampenseri castle, Sicily, Italy by Prof. T. Panzeca).
Fig.(2-30) Sketches of using steel bar in case of deferent thickness in the walls.
Source: (lecture by Prof. T. Panzeca, at Kore university of Enna, Italy).
2-2-2-2- Interventions on the wooden beams:
floors on the old stone building mostly supported on wooden beams, and those beams suffer from damage due to over weight that cause buckling at the middle of the beam; or the damage at connection with walls due to humidity and wood deterioration.
The Italian Architecture in Alexandria, Egypt (the conservation of the Italian residential buildings)
Part (2): Theoretical study ____________________ Chapter (2): Structural failure and interventions in stone building
___________________________________________________________________________
57
Fig. (2-31) photos of damages on old wood beams that support the roofs.
Source: (photos by the researcher at “Okalle Monfrato”, Alexandria, Egypt).
When replacing the old wooden beams it is better to introduce the beams into walls throw steel cases with steel plate and bolts at top as shown in Fig.(2-32) that cases helps to make strong connection, transforming the loads from beams to the walls and make it easy to maintain or change the beams when needed.
Fig.(2-32) Sketches of using steel cases to support the connection between the wooden beams and the stone structure. Source: (lecture by Prof. T. Panzeca, at Kore university of Enna, Italy).
Fig. (2-33) photos of the steel cases that contain the wooden beams and connect it with the walls.
Source: (Restoration project of “Rampenseri castle, Sicily, Italy by Prof. T. Panzeca).
Fig. (2-34) photos of upper cover of the steel cases that prevent it from sliding.
Source: (Restoration project of “Rampenseri castle, Sicily, Italy by Prof. T. Panzeca).
2-2-2-3- Interventions on the wooden roofs:
Final covering in most of the old building are made of wooden trusses and those trusses transform loads to stone arches and then to the walls, in some cases the arches are damage or can’t support the load from the truss as in Fig.(2-35).
Fig.(2-35) Sketches of wooden truss supported on stone arches and the damage due to movement of the truss. Source: (lecture by Prof. T. Panzeca, at Kore university of Enna, Italy).
In that case it better to support the wooden beam of the truss directly on the walls and connect the parts of the beam together with steel bar to eliminate the horizontal forces.
Fig.(2-36) Sketches of wooden beam of the truss directly supported on the walls and connect the parts of the beam together with steel bar. Source: (lecture by Prof. T. Panzeca, at Kore university of Enna, Italy).
After finishing the wooden truss it is covered with layer of wood and fixed on it a layer of corrugated cartoon sheets covered with water resistance material to isolate the structure from rains, and on this layer fixed the final finished surface.
The Italian Architecture in Alexandria, Egypt (the conservation of the Italian residential buildings)
Part (2): Theoretical study ____________________ Chapter (2): Structural failure and interventions in stone building
___________________________________________________________________________
59
Fig.(2-37) photos of the wooden beams supported only on the walls and separated from the stone arches.
Fig.(2-38) photo of the intermediate connection of the beams throw steel part.
Fig.(2-39) photo of covering the roof with thin layer of wood before the final finishing.
Fig.(2-40) photos of the final finishing layer supported on sheets of cartoon coated with water resistance material. Source: (Restoration project of “Rampenseri castle, Sicily, Italy by Prof. T. Panzeca).
2-2-2-4- Recovery of arches and vaults:
Stone arches and vaults manly consists of cut stones but together to form the arch and supported on each other with it’s own weight only, so if any stone peace of the arch get damaged it may cause failure to the whole arch.
Fig.(2-41) photo of cracks in the arch and separation between it’s stones.
Fig.(2-42) photo of supporting the arches during the restoration process.
Source: (Restoration project of “Rampenseri castle, Sicily, Italy by Prof. T. Panzeca).
In this case, the arch must be supported with external supports –strong enough to carry out the loads- then remove the damage stone and connect the remaining part s of the arch with steel pars and then rearrange the arch again, that process transform the loads away from the damaged stone and keep the arch works as structure element.
Fig.(2-43) Sketches of supporting the arch, reinforce it and replacement of damaged parts.
Source: (lecture by Prof. T. Panzeca, at Kore university of Enna, Italy).
In some cases the loads transformed from the arch or vault to the walls cause torsion on the walls and that cause failure to the arch system, so the walls must be connected together with steel bars to resist the loads.
Fig.(2-44) photos of connecting the carrying walls of the arch or vaults with steel bars.
Source: (Restoration project of “Rampenseri castle, Sicily, Italy by Prof. T. Panzeca).
In other the arch are over loaded due to the weight of the filling material above it, and in this case it is difficult to restore the arch because of the existence of the loads, so the loads must be temporary transformed with steel supports until the restoration of the arch and then reload the again and these supports must be located as in Fig.(2-?).
The Italian Architecture in Alexandria, Egypt (the conservation of the Italian residential buildings)
Part (2): Theoretical study ____________________ Chapter (2): Structural failure and interventions in stone building
___________________________________________________________________________
61
Fig.(2-45) Sketches of supporting the loads above the arch during restoration.
Source: (lecture by Prof. T. Panzeca, at Kore university of Enna, Italy).
Notes:
1. Barry A.Richardson, "Defects and Deterioration in Buildings", 2nd edition, SPON PRESS, London.2001.
2. Panzeca, T. “Lectures of restoration” Kore university of Enna, Italy, 2008.