1 Introduction
1.1 Scope
This report sets out the structural design basis for the new six-storey office building, including the basement car park. It records the design codes, loads, materials and performance criteria agreed with the client and the independent checker.
1.2 Reference documents
The design is based on the architectural drawings issued at Stage 3, the fire strategy report FS-002 and the geotechnical interpretative report by Baltic Ground Engineering.
2 Design codes and standards
2.1 Eurocodes and National Annexes
The structure is designed to the Eurocodes. Wind actions follow BS EN 1991-1-4 and the UK National AnnexLVS EN 1991-1-4 and the Latvian National Annex. Concrete design follows EN 1992-1-1 and steel design follows EN 1993-1-1.
3 Actions (loads)
3.1 Permanent actions
Self-weight is calculated from member sizes. A superimposed dead load of 1.5 kN/m²1.8 kN/m² is allowed for services, ceilings and raised floors.
3.2 Imposed floor actions
Imposed floor actions are taken from EN 1991-1-1 Table 6.2 and summarised in Table 1.
| Area | Category | qk (kN/m²) |
|---|---|---|
| Offices | B | |
| Corridors and stairs | C3 | 5.0 |
| Plant rooms | E | 7.5 |
3.3 Wind actions
The basic wind velocity is 21 m/s. The site is taken as terrain category III in all directions.
3.4 Snow actions
The characteristic ground snow load is sk = 1.10 kN/m²sk = 1.25 kN/m² in line with the National Annex.
4 Foundations
4.1 Ground conditions
Made ground overlies soft clay and dense sand. Groundwater was recorded at 3.5 m2.1 m below ground level.
4.2 Piles
The building is supported on 600 mm diameter continuous flight auger (CFA) piles founded in the dense sand. CFA piles are chosen to avoid vibration next to the existing building at No. 12.
5 Fire resistance
Structural fire resistance is R90 for the superstructure and R120 for the basement, in line with the fire strategy.
6 Serviceability
Floor deflections are limited to span/250span/360 after the installation of finishes.
Vibration of the office floors is not assessed at this stage. Floor vibration is assessed to SCI P354 with a response factor limit of 4.
7 Robustness
The building is consequence class CC2b and is designed with horizontal and vertical ties.