More than just about aesthetics!

This interaction explores the key considerations in tensile material selection, factors to be considered while designing tensile structures, and how they drive the net-zero goals of airports.

What factors must be considered by architects and builders while selecting materials for tensile structures?
Modern airports often build their canopies and roofing structures with tensile membranes. Tensile membrane structures (TMS) consist of a prestressed membrane supported by pre-tensioned cables or a rigid frame structure, supported in turn with masts and anchorages. PVC-coated polyester, PTFE-coated fibreglass, and ETFE foils, having excellent resistance to tensile stresses, are the commonly used membrane fabrics. PVC-coated fabrics for tensile architecture should be selected based on the specifications by IS 19115:2025. Key considerations in membrane fabric choice include adequate fabric strength and stiffness, low creep to minimise loss of prestress over time, UV resistance for open-air TMS, translucency to reduce lighting requirements, heat reflectivity for efficient thermal control, abrasion resistance of coated fabric, and smooth surface texture to prevent dust accumulation.

Given the fact that tensile fabrics are often lightweight, how can the structural integrity of tensile structures be ensured?
The structural integrity of TMS is achieved through a combination of form, in-plane or membrane tension, and supporting components. Structural stability begins with finding the correct shape using form-finding, which identifies a self-equilibrated anticlastic shape for a design prestress. The prestress applied during installation and stretching of the “patterned” fabric should be high enough that the structure remains stable under wind, snow, etc. However, architects should also ensure that stresses remain within permissible limits under all conditions. It is also important to ensure that prestress is maintained throughout the service life, and loss of prestress, if any, should be rectified. The erection process should ensure that the overall stability and integrity of the membrane components are maintained throughout this stage. In addition, the membrane design should account for ponding effects. Architects should also work to minimise errors during fabrication, patterning, and erection.

How do factors such as load, wind, light, and rainfall influence tensile material selection and design?Being lightweight materials, self-weight is minimal in these structures and, consequently, the seismic forces. However, a major factor in the design is the overall shape of a TMS, which needs to be properly assessed during the conceptual stage. Wind imposes dynamic forces that can cause fluttering or uplift. Membranes must be aerodynamically shaped and supported by stable anchorage systems. Measures should be taken to prevent the curvature inversion. UV resistance is essential to prevent degradation from prolonged sun exposure. Reflective coatings can reduce solar gain and aid in thermal control. Membranes must be designed with sufficient slope to ensure water runoff and prevent ponding in case of rain and snowfall.

How do tensile structures influence the net-zero goals of airports?
TMS’ lightweight construction reduces material usage, thereby lowering embodied carbon and construction-related emissions. Being translucent, tensile membranes allow natural light to penetrate, reducing the need for artificial lighting during the day and lowering operational energy consumption. Coated fabrics reflect solar radiation, helping reduce the cooling load in terminals and other indoor spaces.  Unlike conventional structures, TMS can be easily dismantled, repaired, and reconfigured if needed, making them modular and flexible in use. Steel, used in cables and masts, is one of the most reusable or recyclable materials; the fabric can also be reused.