Theater, Tirana”

taken into account only three first modes of failure, by studying the capacity curves of certain structural typologies, to get the right strategy for strengthening and updating the structure. The modelling of the structure behavior and its safety assessment by mesh process (finiteelements) can highly benefit of the ETABS, which enables us to create layered walls, considering the non-linearity of each layer that represent materials data. (Vesho, Guri, & Marku, 2019) The most important step is transformation and conversion of panels in piers and spandrels labeling [47]. The vertical panels working in compression are converted in the Piers (frame elements that work in compression), while the horizontal panels under the openings below are converted to the spandrels (beams in bending) (Pitilakis, Crowley, & Kaynia, 2014). The methodology for the analytical part was performed on modal analysis (CEN Eurocode 8, Eurocode 8: Design of structures for earthquake resistance Part 3: Strengthening and repair of buildings, 2003). Investigation procedures: In general the necessity of monitoring and investigating the “building integrity or the load carrying capacity of a unreinforced masonry building arises for several reasons including: assessment of the safety and stability of the structure before or after a seismic event, extension of the building and also the change of use, assessment of the effectiveness of repair innovative techniques applied to structures or different materials, and long-term monitoring of material parameters and structural performance.” (Binda, Saisi, & Tiraboschi, June 2000)

8.1.4 Modal analysis “Structural evaluation and seismic performance of the National Theater, Tirana”

Below is presented the object to be analyzed, the National Theater building after interventions. The “constructive-structural project with drawings and technical specifications for this building are taken from the technical archives” of Tirana, to be analyzed and investigated later.

47 pier = column, spandrel = beam. Both piers and spandrels are equivalent panels constructed of shell elements, showing the element way of work according the static concept.

Figure 187. The National Theater finite elements structural model analyzed (SAP2000 V.22)

The typology of the existing building is a composite-masonry structure which consist of a mixture between wood and concrete with 2 different masonry thicknesses, 23cm at basement level and 20cm. The last thickness is mainly used as a separating wall between rooms and on the upper levels. (Menghini, Pashako, & Stigliano, Architettura Moderna Italiana per le citta d'Albania, Modelli e interpretazioni, 2012) This kind of masonry structures have low masses and they respond well to seismic waves, but due to the interventions that have been occurred the masses have changed. The building has been modeled in SAP2000 v22 and due to the lack of the program for masonry type of buildings the masonry has been modeled as a reinforced concrete wall with a decreased capacity. Mechanical properties of masonry: • Material property data Masonry • Directional symmetry type: Isotropic • Weight per unit volume: 8 kN/m3 • Mass per unit volume: 256 kg/m3

Material mechanical property data: • Modulus of elasticity: E=18608 MPa • Shear Modulus: G=7753 MPa • Poisson’s ratio: u=0.2 • Coefficient of thermal expansion: A=10-5 l/C

The masonry behavior is modeled as a linear shell-thin with a low compressive strength concrete. The importance is to see where the combination of the vertical stresses S1-1 and the horizontal stresses S2-2 would intersect and create additional stresses.