Large Mosque Dome Steel Structural Design

1. Project Overview

The total construction area of the Hangzhou mosque dome is 16375m². The building is an attached main building with the worship hall as the core and main body. The building plane is hexagonal, with a maximum size of 63mx69m. The main part has five floors above the ground and is covered with a curved roof. Set up a basement. There is a pair of bunker towers (minaret towers) at the main entrance on the east side of the main body. The height of the building to the cornice of the dome is 23.30m, the highest point of the curved roof is 58.27m, and the highest point of the Bunker Building is 58.31m. The building as a whole form a strong Islamic architectural style, the effect is shown in Figure 1.

Figure 1 mosque dome design

The main part is arranged in a setback from the third floor to the fifth floor. The main functions are the worship hall, office, etc. The main column grid size is (6~8)mx(6~11)m. The main story height is 3.9m~6m. The main section of the frame column is 700×700, the main section of the frame beam is 350×800 and 250×700, and the concrete strength grade is C35. The diameter of the curved roof is 31m and the height is 27.12m. The fire water tank floor is set at an elevation of 40.60m inside the curved roof. Part of the Bunker Building is octagonal in plan, with a plan size of 4.2mx4.2m.

The structural design service life of this mosque dome project is 100 years, the safety level of the building structure is Class I, the seismic fortification category is Class B, and the foundation design class is Class B. The seismic fortification intensity is VI degree, the design basic seismic acceleration value is 0.05g, the earthquake design group is the first group, the construction site category is I category, the structural importance coefficient is 1.1, the ground roughness category is B category, and the occurrence occurs once every 100 years The basic wind pressure is 0.5kN/m2.

In order to meet the needs of architectural modeling and use functions, the part below the main roof adopts a reinforced concrete frame structure, and the floor adopts an ordinary reinforced concrete structure. The dome adopts a steel frame structure, and the fire water tank floor adopts patterned steel plates. The structural design of this project was completed in August 2012, and the complete acceptance was completed in January 2016, and it has now been put into use.

2 Structural selection and layout

2.1 Worship Hall

2.1.1 Structure selection

According to the layout of the building, the column network of the worship hall is relatively regular, and the span is suitable. The use of reinforced concrete structures is more economical and reasonable, and the construction is convenient. The span of the curved dome is relatively large, and the cross-sectional size of the concrete components is large, so it is difficult to control deformation and cracks, and the construction is also relatively difficult; because the fire water tank is installed inside the dome, the load is large, and the net-bright structure is easy to lose stability, and the platform It is difficult to deal with the rigidly connected joints; the steel structure frame has a small section size and lightweight, which is more suitable for the curved roof of this project. The large roof of the main body is equipped with a ring beam with high rigidity as the supporting beam of the curved roof, and the ring truss at the bottom of the dome rests on the supporting ring beam through the anti-seismic ball bearing.

2.1.2 Structural layout

The plane of the main body of the worship hall is hexagonal, and the column nets are oblique to each other. At the same time, due to the needs of building functions, it is not suitable to set up seismic joints. There are large openings in the structure at an elevation of 12.600m, and the floor is partially discontinuous. Therefore, the following design measures are taken:

①The floor thickness of this floor is increased to 180, double-layer two-way reinforcement, and at the same time, the side reinforcement of the beam is appropriately increased to improve the out-of-plane Rigidity and strength;

② Increase the height of the 14.050m side beam to the 12.600m slab bottom to further improve the overall rigidity;

③ By adjusting the side beam section and column section, the torsional effect of the structure is controlled to ensure that the floor is in consideration of accidental eccentricity The maximum elastic horizontal displacement and the average elastic horizontal displacement at both ends are controlled within 1.4. At the same time, the elastic plate model that conforms to the actual stiffness change in the plane of the floor is adopted when designing the reinforcement of the structural members, and the influence of torsion is considered. The steel mosque dome has a slope-to-height ratio of 1.8 and is nearly hemispherical. In order to eliminate the horizontal thrust at the bottom of the dome as much as possible, after communicating with the construction professional, the bottom of the dome is tangentially vertical. At the same time, a 245m-high ring truss is installed at the bottom of the dome. and horizontal effects. The main body of the dome is equipped with 18 radial arched steel beams, which are rigidly connected with ring-shaped steel beams at the level of the water tank platform to form an overall frame. The arched steel beams are connected by H-shaped steel secondary beams arranged horizontally to resist the radial force under the external load. As a whole structural system, the dome is supported on the reinforced concrete circular girder at the elevation of 23.480m in the worship hall through six anti-seismic ball bearings. Ball bearings are designed with only hoop and vertical constraints, releasing radial constraints.

2.2 Bunker House (minaret)

2.2.1 Structure selection

The protruding roof height of the Bunker Building structure is 38.85m, the structural plane size is 42mx42m, and the aspect ratio reaches 9.25. The reinforced concrete structure scheme and the steel structure scheme were compared during the design. The reinforced concrete structure scheme has a large self-weight, and the displacement angle of the pure frame structure is large, which cannot meet the requirements of use; the steel structure scheme is light in weight and the corresponding seismic force is also small. The structural displacement can be effectively controlled by setting inter-column supports.

2.2.2 Mosque dome structural layout

The plane of the Bunker Building is octagonal, with eight ф355 steel pipe columns arranged at eight corner points, and cross braces are set between the columns. Due to architectural modeling requirements, four of the steel columns fell on the concrete wall of the stairwell, and four of the steel columns fell on the lifting beams at the top of the stairwell. The column foot adopts an outsourcing type column foot to ensure the rigid connection of the column bottom. In order to improve the rigidity of the overall structure, steel beams are installed around every 23m along the height direction, and floor slabs are installed every 46m to serve as maintenance and rest platforms. The beam-column joints are intersecting joints, and the structural layout is shown in Figure 2.

Figure 2 Layout plan of the minaret

The Hangzhou mosque dome adopts a structural system with a lower reinforced concrete frame and an upper steel frame dome. As an independent force-bearing system, the dome is supported on the concrete ring beam of the large roof through six anti-seismic ball bearings.