A mixed-panel acoustic screen for an elevated highway retrofit — balancing viaduct load limits, wind exposure and an existing-structure interface with absorptive tube, reinforced acrylic and micro-perforated metal panels.
This project shows a reusable pattern for elevated highway retrofits: start from the acoustic target, then choose the lightest panel mix that still meets Rw ≥ 26 dB (non-transparent) and NRC ≥ 0.60 (absorptive) under JT/T 646-2025. Mixing a lighter transparent module with absorptive metal modules cuts dead load on the existing deck, a shared H-section post system unifies the wall, and segmenting at bridge expansion joints prevents thermal and dynamic stress.
The S207 Xiuzhou–Xianju Expressway viaduct retrofit carried a straightforward brief with a difficult envelope: deliver a continuous acoustic screen along an elevated roadway near housing, without adding avoidable dead load to a structure already designed to a fixed budget. Zhaobang Metal acted as the barrier material supplier — absorptive and transparent panels, H-section posts and fixing accessories, with shop drawings and acoustic interface data. As with all projects, on-site erection was performed by the local contractor and EPC under the project's own structural and acoustic supervision.
| Parameter | Supplied specification |
|---|---|
| Location | S207 Xiuzhou–Xianju Expressway viaduct retrofit |
| Total barrier length | 6,200 m |
| Barrier height | 3.5 m (above deck) |
| Post system | H-section steel columns |
| Panel system | Absorptive tube + reinforced acrylic (PMMA) panel + micro-perforated metal panel |
| Acoustic target | Panels specified to JT/T 646-2025: Rw ≥ 26 dB (non-transparent), NRC ≥ 0.60 (absorptive), generally aligned with the corridor's insert-loss expectation |
| Corrosion protection | Hot-dip galvanized posts + powder-coated panels (RAL), typical for an outdoor C3–C4 environment |
| Project role | Material supply (panels, posts, accessories), shop drawings, acoustic data; erection by local contractor |
1. Viaduct load budget. The existing elevated deck had a defined residual load capacity, so a heavy all-full-metal wall would have forced structural strengthening. We kept the panel mix light: the transparent reinforced-acrylic module weighs far less than an equivalent solid metal panel, while the absorptive metal modules were held to 0.8–1.5 mm sheet thickness typical for this class.
2. Wind exposure on an open viaduct. An elevated structure sees higher design wind speeds than a ground-level road. The H-section posts and foundations were sized from the site wind zone, with post spacing finalized in the 2.0–2.5 m band typical for elevated, wind-exposed sections.
3. Adapting to the existing structure. The new screen attached to a deck edge and parapet not originally built for a barrier. Connections used cast-in anchors and brackets detailed around the existing geometry, and the alignment followed bridge expansion joints so the barrier moved with the structure instead of fighting it.
Absorptive tube. The workhorse of the wall — a perforated, absorptive element with a mineral-wool or fibre-composite core that soaks up incident sound on the source side and limits reflection. Our standard absorptive panels reach NRC 0.80–0.95, above the NRC ≥ 0.60 baseline in JT/T 646-2025.
Reinforced acrylic (PMMA) panel. A transparent module used where the community needed sightlines and daylight. It is impact-rated and UV-stabilised, and shares the same H-post fixing as the metal panels so the wall stays continuous.
Micro-perforated metal panel. A finer-perforation absorptive face that delivers high NRC with a cleaner architectural look, generally preferred on visible frontages of an elevated road. All three modules stack on the H-section post system into one unified barrier. For the full construction reference see the noise barrier specifications page, and the noise barrier product page for the supply envelope.
Module lengths and post spacing. Panels were supplied in standard modular lengths (1.96 m / 2.46 m / 3.0 m typical) and fixed between H-section steel posts at a spacing finalized for the viaduct wind zone, generally 2.0–2.5 m on exposed sections.
Expansion joints. The barrier was segmented to follow the bridge expansion joints, letting the screen expand and contract with the deck under temperature and traffic movement, avoiding the cracking you get when a rigid wall is built across a moving joint.
Drainage and coordination. Absorptive cores were detailed with drainage so infill stays dry — waterlogged infill loses absorption and adds dead load — and fixings were coordinated with the deck waterproofing. Zhaobang provided shop drawings and acoustic data; the local contractor handled foundations and erection. See the noise barrier installation guide for the typical sequence.
The supplied package delivered a continuous 6,200 m acoustic screen along the S207 viaduct. Panels were inspected and accepted against the project's acoustic and structural requirements: the non-transparent and absorptive panels were specified to meet or exceed the JT/T 646-2025 thresholds (Rw ≥ 26 dB for non-transparent panels, NRC ≥ 0.60 for absorptive panels), and the post-foundation system was verified for the site wind load under GB/T 51335-2018.
Acceptance generally followed the typical highway pattern of visual and dimensional inspection plus acoustic spot checks against the design insert-loss target from the HJ/T 90-2004 acoustic report. Because the transparent and metal modules share one post system, the wall reads as a single continuous barrier. A full record of comparable work is on the projects page.
The first step is to read the viaduct's residual load budget before choosing a panel mass. On the S207 retrofit we avoided an all-full-metal wall and instead mixed a lighter reinforced acrylic (PMMA) transparent module with absorptive metal modules, which reduced dead load on the existing deck while keeping continuous acoustic coverage. Panel sheet thickness was held to 0.8–1.5 mm typical, and post spacing was finalized with the structural engineer so the H-section columns carried wind load without over-sizing the foundation. The rule is simple: fix the acoustic target first, then select the lightest panel construction that still meets the Rw and NRC thresholds.
Yes. On this project the reinforced acrylic (PMMA) transparent panels, the absorptive metal tube panels and the micro-perforated metal panels were all mounted on the same H-section steel post system, so they stacked into one continuous wall along the viaduct. Sharing a post system is the standard way to combine sightline and absorptive functions without doubling the structure. The transparent modules are impact-rated and UV-stabilised for outdoor service, and the metal modules provide the bulk of the sound reduction. Zhaobang supplies the mixed panel set with matching fixing accessories so the contractor erects one unified barrier.
For Chinese highway projects the reference is JT/T 646 (Highway Noise Barriers), updated in 2025 across parts 646.1, 646.2 and 646.4 by the Ministry of Transport, with the official texts published on jtst.mot.gov.cn. It requires a weighted sound reduction index Rw ≥ 26 dB for non-transparent panels and a noise reduction coefficient NRC ≥ 0.60 for absorptive panels, plus structural, safety and durability requirements. The structural design of the post-foundation system should follow GB/T 51335-2018, and the acoustic design and measurement should follow HJ/T 90-2004. Zhaobang panels for this project were specified to meet or exceed those thresholds.