Structural design of an office building
Our company has developed structural drawings for the office building.
Description of structural and technical solutions for the underground part of the building
Choice of foundation type
The building structures are described in this volume only the construction of the underground part of the building is described.
The foundations are grounded with gravelly soil and clays of a tight plastic consistency. The foundation slab has a broken configuration in plan and approximate dimensions in plan. The total area is 4000 m2. The thickness of the foundation slab is calculated as follows: between the axes it is 800 mm and has a top mark of -9,000, and between the axes it is 1100 mm and has a top mark of -9,000. The thickness of the foundation slab near the lift core between the axes is 1800 mm and the top elevation is -7,000. The base of the foundations is at -9,000. There are no expansion joints between the buildings.
Description of the underground structures of the building
Vertical elements
The building consists of reinforced concrete cores around the lifts and stairs, a reinforced concrete frame of beamless slabs and columns. The structural system of the stylobate is also designed with reinforced concrete cores around the lifts and staircases, and a reinforced concrete frame of beam-less slabs and columns.
The thickness of the external reinforced concrete walls that adjoin the wall in the ground, due to its geometric deviations from the design, an increase envisaged towards the "wall in the ground". In the calculations and drawings a value of 250 mm.
Dimensions of the vertical elements of the underground part of the building:
On the stylobate, the main vertical elements are reinforced concrete columns measuring 800x400mm, 600x600mm, 600x400mm, internal and external reinforced concrete walls measuring 250mm.
The underground's part slabs of the building
The floor slab above the first floor is a reinforced concrete beam-less slab, which is supported by walls and columns with a thickness of 300mm, under this slab there are 200mm thick capitals, The capitals are 200 mm thick and their sizes above columns 400/400mm and 400/500mm are 1500x1500mm, above columns 800/400mm 1800/1400mm and 1700/1500mm, above columns 600/400mm-1600/1400mm, above columns 600/600mm-1600/1600mm, above columns 450/700-1800/1400mm. There are also 200 mm thick capitals above the partitions, and their dimensions are 2600/1400 mm.
Transition plate
According to architectural and planning requirements, the vertical load-bearing structures of the above-ground part do not coincide in location with the similar elements of the underground part of the sections. Therefore another structural element has been introduced - reinforced concrete transition slabs and transition beams, which are located under the +1 floor, and have the function of redistributing the forces of the above-ground part of the building onto the walls and partitions of the underground part of the building.
Stresses and impacts
The structures and foundations of the buildings and structures of the complex are calculated according to the limit state method for the action of loads and impacts in their possible adverse combination with the coefficient of reliability of loads and the coefficient of combination of loads, taken in accordance with the requirements.
Calculations of the foundation, foundations and underground part of the building:
Designed office building with an underground parking refers to the 2nd (normal) level of responsibility and to the III geotechnical category corresponding to the constructions of high and normal levels of responsibility in complex engineering and geological conditions, as well as the construction of pits underground and underground structures in conditions of dense urban development. Reliability coefficient shall be taken as 1.0. Static and dynamic calculations of building structures and structures of the complex were comprehensively performed as for spatial system, including modeling of foundation mechanical operation, bearing structures of underground and above-ground parts, with application of certified software complex using finite-element method. The calculations were carried out taking into account the inelastic properties of foundation soils and structural materials.
The design of the individual building elements is based on actual combinations that show how and when each type of load will affect the building. The forces in the structural elements from the vertical loads were calculated considering their combinations. The computer programme "Tower & Planet & PanelPro", which has a certificate of conformity was used for modelling and analysis of all enclosure models, based on the finite element method. Tower is a general programme using the finite element method to analyse simple and complex two- or three-dimensional structures. The model is based on structural data including housing geometry, frame element dimensions and wall thicknesses, as well as material characteristics. Loads and masses are entered into the computer for use in static and dynamic analyses. The dead weights of the structures are automatically calculated. The finite element analysis provides the forces in the structural elements used to design the structures.
Determining the stiffness characteristics of the substrate
The technical report "Determination of the rigidity characteristics of the foundation for the design of the foundations of the hotel and business complex" developed Moscow. The deformation characteristics of the complex foundations were determined by means of mathematical modelling on a computer using the finite element method using non-linear geomechanical soil models. Modelling was performed using the PLAXIS geotechnical software in a planar formulation. Two cross-sections were carried out along and across the building. Geomechanical models of the soil mass to perform modelling of the computed areas and sections were built based on the analysis of geotechnical cross-sections and the results of laboratory studies of the physical and mechanical characteristics of geotechnical elements.
Progressive destruction calculation
The structural check for resistance to progressive collapse was carried out using a spatial model of the building structures in a computationally complex calculation. Based on the results of the static calculations, the most vulnerable places in the structural scheme of the buildings have been identified and the most dangerous local failure patterns have been assumed. In calculations for progressive collapse the values of loads and properties of materials are assumed to be as follows:
- The calculation was carried out for a particular combination of loads and stresses, including permanent and long-lasting temporary loads;
- Permanent and continuous temporary loads were assumed according to the current regulations with combination factors and load-bearing capacities equal to one;
- The calculation has been carried out using standard values of strength and deformation characteristics of materials, according to the existing norms, for reinforced concrete and steel structures. These resistance characteristics of materials have been increased by using additional coefficients of reliability and coefficients of working conditions, taking into account low probability of emergency influences, use of reinforcement operation beyond the yield strength of the material. These coefficients are taken as 1.15 in total.