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U-shaped annealed profiled glass, or U channel glass is used in both the interior and exterior glass façade for decades, as it has long and durable service life and also available in a variety of colors and textures with varying translucency, allowing for sunlight to enter the buildings without the privacy concern. The conventional way to install U-shaped glass is glass captured either vertically or horizontally.
This paper introduces a newly developed project, which is a new hospital located in Kaohsiung, 2nd largest city in Taiwan. The building has 8 stories in height with 2 floors under ground with an innovative U-shaped glass exterior façade design coupled with structural silicone sealant bonding technology on the horizontal sides only.
This innovative glass façade design not only gives novel appearance, but also offers a better seismic and structurally sound performance which enabling by the application of structural silicone sealant bonding technology. Performance mock up test verified 8mm thick tempered monolithic U-shaped profiled glass in 4.1m long span can passed -5.250 kPa windload (150% design windload) and accommodate up to 31.5mm (horizontal) and 5mm (Vertical) facade movement test respectively in compliance with ASTM E330 & AAMA 501.1 related standard tests, despite the U-shaped glass was only supported on the horizontal (head and sill) sides.
This paper also details the façade design, materials selection and structural sealant glazing in shop quality insurance.
U-shaped or so-called U channel glass is a specialty architectural glass which had been used widely in both the interior and exterior façade projects and applications for decades [1 & 2]. It can be single or double glazed design and has a wide range of options from clear to un-transparent, flat or has different surface finishes (wave or texture), tinted or un-tinted, coated with Low E coating or protective films, low iron, wired or in tempered or heat strengthened treatment, it is also available in a variety of glass length, flange height and width to fulfill architect conceptional design and project needs.
Its key features are
- Available in a variety of colors and textures with varying translucency, allowing for sunlight to enter the buildings without the privacy concern and can lower artificial lighting loads
- Self-supporting uninterrupted spans without intermittent support, easy to install
The conventional way to install U-shaped glass is glass captured either vertically or horizontally.
In original German Schneider + Shumaker architect design concept, U-shaped or U channel glass was chosen as it not only gives buildings a Chinese lantern's hazy look to integrate this building into surrounding buildings, but also optimum building energy efficiency enabling by double skin façade design. However, detail engineering study done by the local Architect Tan Lai & Association Architects & Engineers and project team have decided in a very different way to fix the exterior U-shaped glass - using structural silicone bonding technology instead of conventional fix or captive support, since the U -shaped glass is very rigid so that a flexible fixing by structural silicone sealant also will be a big plus. It is worth mentioning that this project was located in southern Taiwan, Kaohsiung city. Although only 8 stories high building, but South Taiwan is no stranger to earthquakes, for instance, there was a quake (6.6 on the Richter scale) that occurred in Kaohsiung county in 2016, and many other powerful earthquakes have hit the country includes a 7.1 Richter scale quake on Sep 21st, 1999 that occurred in the middle of the country. Therefore, the project design team needs to ensure the building design can withstand these devastating events, as a result, the use of structural silicone sealant for U-shaped exterior glass skin was chosen jointly by the architects, main contractor and the curtainwall manufacturer over the traditional mechanical captive system, which interior façade wall includes conventional mechanical captive 17.52mm thick laminated vision glass, 4 sided structurally sealant glazed 17.52mm thick laminated glass sash units, alum. louver and 4mm thick alum. cladding spandrel panel, to meet local energy code for hospital design. The fixed laminated glass head/sill cap bead joints, glass edge perimeter joints and alum. cladding butt joints then sealed with silicone weatherseal sealant to provide watertight and airtight function.
Mullion and transom joint details of Façade system are shown in below Figures 1-6.
Structural Sealant Glazing (SSG) is a technique of attaching glass (or other building substrates) to a metal frame using structural silicone sealants as shown in Figure 7. In this glazing
Load tested on single U-shaped glass size was 90mm (flange height) x 262mm (W) x 4060mm (L). Load tests were performed at both facial and rear sides of U-shaped glass
To verify the proposed structural glazing system can pass local building codes, the project team prepared a full-scale unit (6112.5mm (W) x 9755mm (H) x 200-790mm (T) in size) for
Another critical element in this façade design is the use of structural silicone sealant properly. Although the use of structural silicone in curtain wall fabrications shows great success and the
Structural sealant glazing utilizes a high-performance silicone sealant to attach glass, metal, or other building materials to a metal frame in lieu of gaskets and mechanical attachments. This advanced bonding
The authors wish to acknowledge German S+S (Schneider & Shumaker) Ms. Zhou Sun (architect) and Mr. W.J. Weng, Project Manager of Yulian Façade Metal & Engineering (Curtain Wall Fabricator) and Mr. F. S. Wu, Chief Officer of Li Ming Construction Co., Ltd (main contractor).
- Website of BENDHEIM Channel Glass https://bendheim.com/
- Website of Appleton Specialty Glass (ASG) Limited www.appleton.net.cn
- Parise, C. J. and Spindler, R.G “Structural Sealant Glazing in the 1980s”, Exterior Wall System: Glass and Concrete Technology, Design, and Construction, ASTM STP 1034, 1991, pp.94-117.
- Annual Book of ASTM Standards Volume 04.07 “Designation: C1401-14 Standard Guide for Structural Sealant Glazing”, American Society for Testing and Materials, 2019.
- “Kao Ho Hospital ”ASG Single U-Shaped Glass Load Test Report issued by Cheng Kang University Civil Engineering Lab on March 27 2020.
- “Kao Ho Hospital ”Curtain Wall Performance Mock-Up Test Report Issued by Chao Li Technology Corporation on Sep 9th 2019.
- Baker, M. E “ Structural Glazing Failure – Five Case Studies ”Durability of Building and Construction Sealants and Adhesives, STP 1453, A. T. Wolf, ASTM, pp37-44, 2004.