World Housing Encyclopedia an Encyclopedia of Housing Construction in Seismically Active Areas of the World an initiative of Earthquake Engineering Research Institute (EERI) and International Association for Earthquake Engineering (IAEE) HOUSING REPORT Unreinforced Brick Masonry Apartment Building Report # 73 Report Date 05-06-2002 Country SLOVENIA Housing Type Unreinforced Masonry Building Housing Sub-Type Unreinforced Masonry Building : Brick masonry in lime/cement mortar Author(s) Marjana Lutman, Miha Tomazevic Reviewer(s) Dina D'Ayala Important This encyclopedia contains information contributed by various earthquake engineering professionals around the world. All opinions, findings, conclusions & recommendations expressed herein are those of the various participants, and do not necessarily reflect the views of the Earthquake Engineering Research Institute, the International Association for Earthquake Engineering, the Engineering Information Foundation, John A. Martin & Associates, Inc. or the participants' organizations. Summary This construction was commonly used for residential buildings in all Slovenian towns, and it constitutes up to 30% of the entire housing stock in Slovenia. The majority of these buildings were built between 1920 and 1965. They are generally medium-rise, usually 4 to 6 stories high. The walls are unreinforced brick masonry construction laid in lime/cement mortar. In some cases, the wall density in the longitudinal direction is significantly smaller than in the transverse direction. In pre-1950 construction, there are mainly wooden floor structures without RC tie-beams. In post-1950s construction, there are concrete floors with RC bond- beams provided in the structural walls. Roof structures are either made of wood (pitched roofs) or reinforced concrete (flat roofs). Since this construction was widely practiced prior to the development of the seismic code (the first such code was issued in 1964), many buildings of this type exceed the allowable number of stories permitted by the current seismic code (maximum 2 or 3 stories for unreinforced masonry construction). Buildings of this type have been exposed to earthquake effects in Slovenia. However, this construction type experienced the most significant damage in the 1963 Skopje, Macedonia, earthquake, which severely damaged or caused the collapse of many buildings. 1. General Information Buildings of this construction type can be found in all Slovenian towns, and it constitutes up to 30 % of the entire housing stock in Slovenia. This construction type was also practiced in other countries in the region, in particular Montenegro and Macedonia, which were part of the former Yugoslavia. This type of housing construction is commonly found in urban areas. This construction type has been in practice for less than 100 years. Currently, this type of construction is not being built. This housing construction was practiced in the period between 1920 and 1965. Figure 1A: Typical Building Figure 1B: Typical Building Figure 2: Vertical Elevation Show ing Key Load- Bearing Elements 2. Architectural Aspects 2.1 Siting These buildings are typically found in flat terrain. They do not share common walls with adjacent buildings. When separated from adjacent buildings, the typical distance from a neighboring building is 30 meters. 2.2 Building Configuration Typical shape of building plan is rectangular with length/width ratio ranging from 2.0 to 8.0. In the longitudinal direction, the building is usually divided into 2 to 5 segments. Each segment has its own entrance, staircase and elevator. The buildings of this type are characterized by two longitudinal exterior walls with the majority of openings located in these walls, and two exterior walls in the transverse direction with a few smaller window openings or no openings at all. The average area of a window opening is 1.8 m² in longitudinal exterior bearing walls. The exterior walls in the transverse direction are characterized with smaller kitchen or toilet window openings of typical area less than 0.5 m². The area of balcony door and window openings is approx. 4.0 m². The door area in the exterior and interior load bearing walls is approximately 2.0 m². The total area of openings is approximately equal to 30 % of the longitudinal exterior wall surface area. 2.3 Functional Planning The main function of this building typology is multi-family housing. In a typical building of this type, there are no elevators and 1-2 fire-protected exit staircases. Usually there are no additional exit doors besides the main entrance. There is also no additional exit staircase besides the main staircase. The main entry and the main staircase of each segment of the building represent the only means of escape from the building. 2.4 Modification to Building A few modifications have been carried out in these buildings. Since the majority of interior walls have been constructed as load bearing walls, no significant changes are observed. In some cases, an additional floor has been built atop the flat roof; the additional floor typically has a pitched roof. Figure 3: Plan of a Typical Building 3. Structural Details 3.1 Structural System Material Type of Load-Bearing Structure # Subtypes Most appropriate type Rubble stone (field stone) in mud/lime 1 mortar or w ithout mortar (usually w ith ☐ Stone Masonry timber roof) Walls Dressed stone masonry (in 2 lime/cement mortar) ☐ 3 Mud w alls ☐ 4 Mud w alls w ith horizontal w ood elements ☐ Adobe/ Earthen Walls 5 Adobe block w alls ☐ 6 Rammed earth/Pise construction ☐ Brick masonry in mud/lime 7 mortar ☐ Brick masonry in mud/lime 8 ☐ Unreinforced masonry mortar w ith vertical posts w alls Brick masonry in lime/cement 9 mortar ☑ Masonry Concrete block masonry in 10 cement mortar ☐ Clay brick/tile masonry, w ith 11 w ooden posts and beams ☐ Clay brick masonry, w ith Confined masonry 12 concrete posts/tie columns ☐ and beams Concrete blocks, tie columns 13 and beams ☐ Stone masonry in cement 14 mortar ☐ Clay brick masonry in cement Reinforced masonry 15 mortar ☐ Concrete block masonry in 16 cement mortar ☐ 17 Flat slab structure ☐ Designed for gravity loads 18 only, w ith URM infill w alls ☐ Designed for seismic effects, Moment resisting 19 w ith URM infill w alls ☐ frame Designed for seismic effects, 20 w ith structural infill w alls ☐ Dual system – Frame w ith 21 shear w all ☐ Moment frame w ith in-situ 22 shear w alls ☐ Structural concrete Structural w all Moment frame w ith precast 23 shear w alls ☐ 24 Moment frame ☐ Prestressed moment frame 25 w ith shear w alls ☐ 26 Large panel precast w alls Precast concrete ☐ Shear w all structure w ith 27 w alls cast-in-situ ☐ Shear w all structure w ith 28 precast w all panel structure ☐ 29 With brick masonry partitions ☐ Moment-resisting With cast in-situ concrete 30 frame w alls ☐ 31 With lightw eight partitions ☐ Concentric connections in all Steel 32 panels ☐ Braced frame Eccentric connections in a 33 few panels ☐ 34 Bolted plate ☐ Structural w all 35 Welded plate ☐ 36 Thatch ☐ Walls w ith bamboo/reed mesh 37 and post (Wattle and Daub) ☐ Masonry w ith horizontal 38 beams/planks at intermediate ☐ levels Load-bearing timber Post and beam frame (no Timber 39 frame special connections) ☐ Wood frame (w ith special 40 connections) ☐ Stud-w all frame w ith 41 plyw ood/gypsum board ☐ sheathing 42 Wooden panel w alls ☐ 43 Building protected w ith base-isolation systems ☐ Seismic protection systems Building protected w ith Other 44 seismic dampers ☐ Hybrid systems 45 other (described below ) ☐ The mortar is made of lime or composite lime and cement mix. 3.2 Gravity Load-Resisting System The vertical load-resisting system is un-reinforced masonry walls. The gravity-load bearing structure consists of roof and floor structures and structural walls. In the case of an additional top floor built atop the original flat RC roof structure, there is a new timber pitched roof. 3.3 Lateral Load-Resisting System The lateral load-resisting system is un-reinforced masonry walls. The lateral load-resisting system consists of exterior and interior brick masonry walls. Wall thickness varies from 380 mm (exterior and some interior walls) to 250 mm (the majority of interior walls). The mortar mix varies through the building height: pure cement mortar is used at the lowest two floors, composite lime/cement mortar is used for the middle portion and pure lime mortar for the upper floors. Due to large openings and longitudinal exterior walls, the lateral resistance in longitudinal direction is often significantly inferior as compared to the lateral resistance in the transverse direction. The lateral load transfer to load- bearing walls is accomplished through roof and floor structures. In the case of older buildings of pre-1950 construction characterized with wooden floor structures, the walls were not joined together by means of wooden or iron ties. In the case of newer buildings, all structural walls are tied together with RC edge beams of RC floors. The walls are supported by concrete strip foundations. The weakest link in this construction are usually wall-floor and wall- roof connections in case of timber floor construction. 3.4 Building Dimensions The typical plan dimensions of these buildings are: lengths between 25 and 90 meters, and widths between 10 and 13 meters. The building has 4 to 6 storey(s). The typical span of the roofing/flooring system is 5 meters. Typical Story Height:Story height ranges from 2.7 to 3 m. Typical Span: It is the typical distance between two adjacent walls and it ranges from 2.2 to 9 m. The bearing direction of floor structures, that carry load in one direction only, is usually the direction of the shorter distance between two adjacent longitudinal or transversal walls. Typical span of floor structures ranges from 2.2 to 6 m.