Report #: 16

Report Date:

Country: GREECE

Housing Type:

Housing Sub-Type:

Author(s): T. P. Tassios, Kostas Syrmakezis

Last Updated:

Regions Where Found: Buildings of this construction type can be found in historical cities of Greece. Perhaps 10% of housing stock in the region. This type of housing construction is commonly found in both rural and urban areas.

Summary: These buildings are mainly found in the historical centers of Greek cities and provinces. The main loadbearing structure consists of stone masonry walls. The walls are built using local field stones and lime mortar. The floors and roof are of timber construction. The seismic performance is generally poor. Diagonal cracking at the horizontal and vertical joints are the common type of damage.

Length of time practiced: More than 200 years

Still Practiced: Yes

In practice as of:

Building Occupancy: Single dwelling

Typical number of stories: 2-3

Terrain-Flat: Typically

Terrain-Sloped: Typically

Comments:

Currently, this type of construction is being built. Only in historic districts, however. The main function of this building ty

Plan Shape: Rectangular, solid

Additional comments on plan shape:

Typical plan length (meters): 10

Typical plan width (meters): 15

Typical story height (meters): 41702

Type of Structural System: Masonry: Stone Masonry Walls: Rubble stone (field stone) in mud/lime mortar or without mortar (usually with timber roof)

Additional comments on structural system: The vertical load-resisting system is timber frame load-bearing wall system. - Load bearing walls - Timber or metal strengthening elements.

The lateral load-resisting system is unreinforced masonry walls. The main lateral load-resisting system consists of unreinforced stone masonry bearing walls. Floors and roof are wood structures. The wall layout in plan is critical for the lateral performance of this construction type. Also, the wall connections and roof/floor-to-wall connections are the critical elements of the lateral load resistance. The materials and type of construction are the most important factors affecting the seismic performance of these buildings.

Gravity load-bearing & lateral load-resisting systems:

Typical wall densities in direction 1: >20%

Typical wall densities in direction 2: >20%

Additional comments on typical wall densities: The typical structural wall density is more than 20 %. Total wall area/plan area (for each floor) 30-40%.

Wall Openings: The building has eleven openings per floor, of an average size of 3.5 sq m each. The estimated opening area to the total wall surface is 18%. This is relevant to the resistance of this type of building.

Is it typical for buildings of this type to have common walls with adjacent buildings?: No

Modifications of buildings: Usually demolition of interior load bearing walls, or partial demolition for the insertion of an opening.

Type of Foundation: Shallow Foundation: Rubble stone, fieldstone strip footing

Additional comments on foundation: Masonry footings (footing width by 300 mm greater as compared to the walls).

Type of Floor System: Other floor system

Additional comments on floor system: Wood planks or beams with ballast and concrete or plaster finishing;

The floors and roofs are considered to be rather flexible.

Type of Roof System: Roof system, other

Additional comments on roof system: The floors and roofs are considered to be rather flexible.

Additional comments section 2: When separated from adjacent buildings, the typical distance from a neighboring building is 5 meters.

Who is involved with the design process?: Other

Roles of those involved in the design process:

Expertise of those involved in the design process: Engineers and architects play an important role during the repair and strengthening of this type of structures.

Who typically builds this construction type?: MasonBuilder

Roles of those involved in the building process: The builders (usually traditional artisans) live in this construction type.

Expertise of those involved in building process: Experience of traditional builders.

Construction process and phasing: Traditional builders. Stones from the area and mortar made in situ. The construction of this type of housing takes place in a single phase. Typically, the building is originally designed for its final constructed size.

Construction issues

Is this construction type address by codes/standards?: No

Applicable codes or standards: Experience. European Codes.

Process for building code enforcement:

Are building permits required?: No

Is this typically informal construction?: Yes

Is this construction typically authorized as per development control rules?: No

Additional comments on building permits and development control rules: This type of structure was constructed without any explicit design requirements. Building permits are not required to build this housing type.

Typical problems associated with this type of construction:

Who typically maintains buildings of this type?: Owner(s)

Additional comments on maintenance and building condition:

Unit construction cost: Since this is a construction method that is no longer practiced, values for unit construction costs are not available.

Labor requirements: Information not available.

Additional comments section 3:

Damage patterns observed in past earthquakes for this construction type: On September 7, 1999, at 14:56 local time, a strong earthquake occurred 18 kilometres northwest of the center of Athens. The earthquake was magnitude .s =5.9 and the coordinates of the epicentre were located at 38.12.-23.64., in the area of Parnitha mountain. This earthquake came as a surprise, since no seismic activity was recorded in this region for the last 200 years. According to strong-motion recordings, the range of significant frequencies is approximately 1.5-10 Hz, while the range of the horizontal peak ground accelerations were between 0.04 to 0.36g. The most heavily damaged areas lie within a 15 km radius from the epicentre. The consequences of the earthquake were significant: 143 people died and more than 700 were injured. The structural damage was also significant, since 2,700 buildings were destroyed or were damaged beyond the repair and another 35,000 buildings experienced repairable damage. According to the EERI Reconnaissance report (see References), in the meizoseismal area, most stone masonry structures with undressed stones, constructed in the first half of the century, suffered significant damage. This included partial collapse of external walls, collapse of corners, separation of the two walls converging at a corner, and extensive cracking.

Additional comments on earthquake damage patterns: Wall: Stone masonry walls were damaged in the 1999 Athens earthquake. The damage included partial collapse of external walls, collapse of corners, separation of the two walls converging at a corner, and extensive cracking (Source: EERI)

Roof/floors: Extensive masonry cracking, due to low tensile and shear strength and unsatisfactory diaphragm action of the horizontal members.

The main reference publication used in developing the statements used in this table is FEMA 310 Handbook for the Seismic Evaluation of Buildings-A Pre-standard, Federal Emergency Management Agency, Washington, D.C., 1998.

The total width of door and window openings in a wall is: For brick masonry construction in cement mortar : less than ½ of the distance between the adjacent cross walls; For adobe masonry, stone masonry and brick masonry in mud mortar: less than 1/3 of the distance between the adjacent cross walls; For precast concrete wall structures: less than 3/4 of the length of a perimeter wall.

Vertical irregularities typically found in this construction type: Other

Horizontal irregularities typically found in this construction type: Other

Seismic deficiency in walls: Rubble stone and lime mortar. The system has low tensile and shear strength, especially for out-of-plane seismic effects.

Presence of large openings reduces the strength of the bearing walls.

Earthquake-resilient features in frame:

Seismic deficiency in roof and floors: Usually they consist of wooden elements, thus diaphragm behaviour and good connections with masonry walls cannot be ensured.

Earthquake resilient features in roof and floors: Even for steel and timber floors/roof the presence of stiffness leads to a rigid diaphragm which is highly desired.

Other earthquake-resilient features: The presence of reinforced concrete ring beams at the roof and floors levels as well as vertical confining elements (RC beams) near the opening, significantly improve the structural behavior.

For information about how seismic vulnerability ratings were selected see the Seismic Vulnerability Guidelines

Additional comments on seismic strengthening provisions: The frist step in the seismic strengthening is the deep repointing of the wall. This technique improves the tensile strength of the wall (up to 10 times). Subsequently, cement-mortar injections are applied (if required) for the further improvement - homogenization of the wall. Finally, RC jacket is applied on the wall surface (Figure 10). The overall structural resistance is greatly improved since the reinforcement (provided in concrete jacket) is activated at the critical cracking point.

Has seismic strengthening described in the above table been performed?: Yes, to a great extent.

Was the work done as a mitigation effort on an undamaged building or as a repair following earthquake damages?: Repair following the earthquake damage.

Was the construction inspected in the same manner as new construction?: Yes

Who performed the construction: a contractor or owner/user? Was an architect or engineer involved?: The construction is usually performed by a contractor, not always with the involvement - supervision of an architect and/or a civil engineer.

What has been the performance of retrofitted buildings of this type in subsequent earthquakes?: The performance was satisfactory.

ITSAK. Report on the 1999 Athens Earthquake, Institute of Engineering Seismology and Earthquake Engineering, Thessaloniki, Greece (www.itsak.gr)

EERI. Special Earthquake Report: The Athens, Greece Earthquake of September 7, 1999 (www.eeri.org/earthquakes/Reconn/Greece1099/Greece1099.html)