DESIGN AND CONSTRUCTION OF A 29-STORY HOTEL BUILDING
Ivo Podhorsky
Introduction
Between 1976 and 1982 a tourist complex for 2500 guests was designed and built in Dagomis on Black Sea coast near the city of Sochi, Russia. The largest building in the complex was a 29-story hotel building for 1600 guests with 180000 m3 of enclosed space. The conceptual design was made in Moscow, Russia (then part of USSR) while the rest of the design was made in Zagreb, Croatia (then part of Yugoslavia) according to Soviet building codes. The contractors came also from Croatia. The large and complex structure of the building had a special trait – according to the owner’s request no permanent expansion joints were allowed although its maximum dimension in plan is approx. 130 m.
Description of the structure
The building has the form of an irregular three-legged star. The central part is hexagonal with three curved sides and the “legs” are rectangular. The main characteristics of the reinforced concrete structure built in situ are presented on Figures 1, 2, and 3. In lower four stories, where larger rooms are needed, the structure is a space frame with 7,20 m spans in longitudinal direction. In upper stories (6th to 28th) with hotel rooms the structural system consists of transversal and longitudinal walls with 3,60 m spans in longitudinal direction. The transition between two systems is provided in fifth floor (for services and auxiliary contents) by means of strong beams in both transversal and longitudinal direction. In central part the box section walls for elevators and staircases are placed, as well as the frame structure. The rigid floor slabs connect structural elements. The foundation structure consists of a mat and drilled piles which carry all the loads to the base rock.
During construction the structure is exposed to larger temperature effects than in the finished building which is enclosed and insulated. Moreover, during construction the shrinkage effects are also acting. Therefore, provisional joints were designed across the whole width and height of the structure at four positions: three at the contact of the central part and “legs” and one more in the middle of the long “leg” (Fig. 3). The details of the provisional joints are given on Figures 4 and 5.
Modeling, analysis, and design of the structure
Although a mainframe computer (CDC Cyber 27) and a very sophisticated program for analysis of space structures /1/ were used, at that time the structure was too complex (at least, for us) to form a detailed model in which each element of the structure would be represented by a corresponding member of the model. Therefore, a simplified global model was used, which was made of macro-elements representing typical sections of the actual structures. The properties of the macro-elements were calculated by analyzing typical sections represented by local models. The section properties were calculated based on concrete sections of the elements. Only for the analysis of temperature effects the section properties taking into account the cracking were used according to /2/.
The analysis for the global model was carried out for three load cases – two static (wind loads and temperature effects) and one dynamic (seismic analysis). The structure was designed to the base shear that amounted to 5,5% of the building weight which corresponds to the design seismicity of the region (VIII MCS) and the dynamic properties of the structure (the fundamental frequency about 1Hz).
For most of walls, columns, and beams reinforcement design the seismic forces had the dominant influence except for the columns at the ends of “legs” which were most influenced by temperature effects. The additional reinforcement for floor slabs resulting from temperature effects was along the whole length of the “legs” and anchored in the central part slab.
The execution of works
Originally it was planned to fill in (close) the provisional joints after the completion of external walls, which means that the structure is in roughly the same condition as in use. But, after the structure was completed, the contractors requested to consider the possibility of earlier filling of the joints in order to simplify and speed up the execution of works. Therefore it was decided to measure the real strains of the structure due to temperature effects by measuring the relative displacements of the adjoining sections of the structure at provisional joints. The measurement was carried out at eleven spots: four on first and sixth floor each, one on 23rd floor (long leg) and two on 25th floor (short legs). The measurement spots are given in Fig. 3. The pointed bars 20mm in diameter were built in neighboring elements (Fig. 6). The measurements were carried out during three months by means of vernier calipers every day at 7 a.m. and 3 p.m. At the same time the air temperature was also measured. The results of the measurements gave evidence of a considerable thermal inertia of the concrete structure. While the air temperature changed in the range of 20°C the structure temperature changed in the range of 3,7°C or less. The shrinkage process was also mostly completed because the structure was finished a year ago. Therefore it was decided to fill in the temporary joints.
References
/1/ Bathe, K.J., Wilson, E.L., Peterson, F.E., “SAP IV: A Structural Analysis Program for Static and Dynamic Response of Linear Systems”, EERC, Report No EERC 73-11, June 1973/April 1974.
/2/ НИИЖБ, Руководство по расчету статически неопределимых железобетонных конструкций, Стройиздат, Москва 1975.
The author
Prof. dr. Ivo Podhorsky, Faculty of Architecture, University of Zagreb, 10000 Zagreb, Croatia Telephone +385-1-6681719, Fax +385-1-4828079, e-mail:
Fig. 1 The plan of a typical upper floor (6th to 28th)
Fig. 2 The plan of a typical lower floor (1st to 4th)
Fig. 3 The longitudinal section of the building
P.J. - provisional joint
® - measurement spot on provisional joint
Fig. 4 Provisional joint – the lower floor slabs
Fig. 5 Provisional joint – the upper floor slabs
Fig. 6 Detail of a measurement spot at provisional joint