Office building in Tianjin

Building use

Office building

Country/Region

China

Overview

The reinforced concrete core -mega braced frame tube system is used, which the mega braced frame tube consists of 4 hexagonal columns at edges of the building, 9 belt trussed, and mega bracings.

Basic information (construction date, number of stories, gross floor area, adopted design code, engineer(s), Contractor(s), etc.)

Construction date: 2015
Number of stories: 117
Gross floor area: 370,000m2
Adopted design code: GB 50011-2010; GB 50010-2010; GB 50017-2003; JGJ 3-2010; JGJ 99-2015; JGJ 138-2001; CECS 159:2004; CECS 28:90
Engineer(s): East China Architectural Design & Research Institute Co., Ltd and Arup Group Limited
Contractor(s): China Construction third Engineering Bureau Ltd

Issue and/or innovation

1. The giant bracings and belt trusses are not at the same plane. The multi-cell special-shaped concrete-filled steel tubular (CFST) is applied in giant columns, which is convenient for the connection between huge bracings, belt trusses, and giant columns.
2. The reinforced steel cages are set in the multi-cell giant columns. Rachel reinforcement and vertical stiffening ribs are applied in order to enhance the stability of the columns.
3. Out-covering high-strength prestressed anchor bolt column footing joints are applied in the giant column footings, which reaches the tensile requirement of column footing for strong earthquakes.
4. The steel tubes of the giant columns are large, thus the columns need to be cut and lifted separately before welding in vertical direction to complete assembly of the columns. There is a lot of welding work on site, therefore, the effect of residual stresses due to welding on structural behanvior needs to be evaluated. According to experimental results, the combined welding seam method is utilized, which reduces work quantities and avoids relatively high welding stresses.

Reason for composite solution

1. The reinforced concrete core -mega braced frame tube system is used in the tower building, which the mega braced frame tube consists of 4 hexagonal columns at edges of the building, 9 belt trussed, and mega bracings. The composite structure of steel beams and profiled steel sheets are used in the floor structure.
2. The main functions of 4 mega columns are transferring vertical loads and resisting lateral loads and they undertake huge loads. The concrete-filled steel tubular columns with specially shaped sections are applied. Q345GJ steel and C50-C70 self-compacting concrete are used in these columns with a maximum cross-section of 45m2.
3. The steel plate or steel member is embedded inside the shear wall in the core, which efficiently reduces the thickness of the shear wall in the core. In comparison with the reinforced concrete shear wall, the composite shear wall has significantly better ductility. The use of composite shear walls can reduce the self-weight of the structure,increase load-carrying and shear capacity. Therefore, the structural performance of the core tube under rare earthquake is improved.

Specific solution/technical details

1. The loading features of multi-cell special-shaped concrete-filled steel tubular columns are studied using experiments and numerical investigations, which indicates steel and concrete of mega columns can reach the plane section assumption. The tie bar and vertical stiffening ribs can improve the ductility of the mega columns.
2. According to the plane section assumption, the calculation method of load-carrying capacity of the mega columns is suggested. It is reasonable that the load-carrying capacity of giant columns can be validated by the N-MX-MY curve surface.
3. It has been proved that the effect of welding residual stresses on the behavior of mega columns can be neglected in accordance with various combined welding seam experiments. Total penetration welding is used for horizontal seams and assembly seams on the exterior of the mega columns. The performance of giant columns can be lightly affected by the interior vertical seams, thus partial penetration welding can be applied.

Impact or effectiveness

1. In comparison with concrete elements, the cross-section of the mega columns reduces effectively. The formwork is canceled, which significantly saves construction time.
2. In comparison with steel structures, the cost of mega columns is significantly reduced.
3. The connection joints of the multi-cell special-shaped concrete-filled steel tubular columns, mega bracings, and belt trussed are conveniently assembled and the load can be directly transferred.
4. The stability of multi-cell columns has been enhanced that improving the ductility after the reasonable detail was applied.
5. Optimization of combined welding seams of the mega columns reduces a lot of welding work in the processing and assembling stages, which meets the environmental requirement.

References / Technical Papers Content

Bao, L. J., Wang, D. S., Zhou, J. L. et al. Design and Rethinking of Mega Brace in Tianjin 117 Tower [J]. Progress in Steel Building Structures. 2014, 16 (2).
Bao, L. J., Tong, J., Chen, J. X. et al. Structural design summary of the tower of Tianjin Goldin 117 Building [J]. 2022, 52 (9).