The Chongqing Longxing Football Stadium project is located in Liangjiang New District, Chongqing. It is a 60,000-seat

professional football stadium that hosts top international and domestic football events. It was originally a construction project for the 2023 Asian Cup Football Semi-finals. The stadium design is inspired by Chongqing's "hot lifestyle, hot development momentum" and the Asian Cup's "hot football passion", with smooth curve elements of convergence, rotation, and rise throughout the design (Figure 1). The building height of the project is 61m, the main structure is a steel structure ball grid, the outer canopy perforated aluminum plate system is about 80,000 m2 (of which the roof part TPO single-layer waterproof membrane Langxuanming roof is about 40,000 m2), and the ETFE membrane structure is about 20,000 square meters.

1. Roof design

The roof of the Chongqing Longxing Football Stadium is composed of a 3mm thick fluorocarbon spray perforated aluminum veneer decorative layer, a TPO single-layer waterproof membrane and an ETFE membrane structure (Figure 2). The roof is a semi-open system, in which the 3mm thick fluorocarbon spray perforated aluminum veneer is divided into approximately 3mx0.8m, distributed in a parallelogram, and the function is outdoor decoration, not involving waterproofing, insulation, sound insulation and other system functions.

1.1 Single-layer waterproof membrane roofing system

The football field roof waterproofing system adopts a single-layer waterproof membrane roofing system. The membrane adopts a 15mm thick polyester fiber reinforced TPO waterproof membrane. The structural layers are: first, the support layer of the 1.0mm thick aluminum-zinc-magnesium corrugated steel plate is nailed and fixed to the purlin system, and the vapor barrier membrane is laid on the corrugated plate, and then the insulation rock wool with a density of 180kg/m' is fully laid on it for leveling, and finally the single-layer TPO waterproof membrane is fully laid by the non-perforated mechanical fixing method (Figure 3-4).

The structural parameters of the TPO single-layer waterproofing membrane roofing system are as follows.

1) The large surface waterproof layer uses 1.5 mm thick polyester fiber reinforced TPO waterproofing membrane, which is connected to the corrugated steel plate by non-perforated mechanical fixing method, and the joint position is welded by hot air; the waterproof layer above the stainless steel gutter uses 1.5 mm thick polyester fiber reinforced backing TPO waterproofing membrane, which is fully bonded to the stainless steel gutter by adhesive, and the membranes are connected to form a whole by hot air welding.

2) The indoor thermal insulation rock wool uses 180kg/m' high-density hydrophobic rock wool, with a fireproof grade of Class A non-combustible and a thickness of 50mm. The roof system of this project is a semi-open canopy structure. There is no energy-saving and thermal insulation requirement for the entire roof. The thermal insulation rock wool is mainly used for the laying and leveling of TPO membranes and noise reduction.

3) The roof vapor barrier uses a composite polypropylene vapor barrier membrane with a thickness of 0.3mm. The vapor barrier is completely sealed to ensure that water vapor cannot enter the upper insulation layer from the inner field side.

4) The bottom supporting laminated steel plate of the roof structure adopts 1.0mm thick color coated aluminum zinc magnesium corrugated steel plate, plate type YX35-125-750, the base material is aluminum zinc magnesium high-strength steel plate, the outer surface treatment adopts continuous roll fluorocarbon pre-roll coating two rolls and two baking treatment, and the back is completed with polyester paint and panel one-time roller coating.