Over the years, civil structural testing/ analysis for their dynamic responses and operational behavior have brought in a bunch of learnings that have both refined our intervention approach and a good set of advisories to structural and architectural consultants.
The journey began with our involvement in metro rail projects across several Indian cities. The scope of testing and analyzing metro piers, structural supports, rail beds, and other reinforcement components provided us with an in-depth understanding of the structural dynamics of these systems.
Natural frequency responses mapped at key structural locations provide insights into how the structures react to impending forces. Estimating dynamic forces requires careful consideration of numerous variables, ensuring that neither overestimations nor underestimations affect the accuracy of calculations or design. In many cases, physical measurements of interface forces are used to determine actual force values, which then serve as inputs for either modeling or empirical analysis.
The intense urbanization and massive construction activities in the leading cities all over the world have lead to optimization of structural designs driven by cost cuts and aesthetics. There are many cases that have caused structural dynamic rigidity issues during their usage and warranted complete investigation, rehabilitation and re-designing of structural components in some cases.
The Manhattan at New York - the crowded sky scrappers and their hyper designs
Two cases of interest are worth discussing here. The first involves a walkway, also known as the boardwalk, located within a large software tech park. This structure was built to provide a safe path for employees to walk to their workplace from the nearest metro station. The walkway stands approximately 9 meters above the ground, stretches over 140 meters, and is supported by visually appealing single-post tree design columns spaced at regular intervals.
Boardwalk in a IT park space
Upon the commissioning of this walkway, users reported discomfort while walking on it, with some mentioning noticeable oscillations in the structure and others even experiencing nausea and motion sickness.
A design review and detailed investigation revealed a trade-off between the dynamic loads considered during design and the aesthetic appeal of the overall boardwalk. This compromise became apparent in the structure’s performance, leading to the walkway being taken out of service.
The second case involves an Air Traffic Control tower at one of India's leading airports. Standing at 62 meters tall, the tower features a control room that protrudes from the main structural frame by approximately 3 meters. This cantilevered design element not only contributes to the tower's unique aesthetic but was also intended to provide an improved vantage point for overseeing the airport apron area.
High rise ATC towers with offset structural loads
Exposed to elements and weather conditions throughout its operational life, particularly wind loads, the Air Traffic Control tower has faced concerns regarding its structural stability. Reports indicate low-amplitude sway within the control room. While such minimal displacements are typical in tall structures, any degradation of the tower's foundation, instability of the underlying strata, or the influence of offset loads on the tower mast could contribute to further deterioration.
Dynamic stability-related issues are increasingly reported across a wide range of structures—from machine shop floors to high-rise residential complexes, bridges to commercial spaces. While most of these challenges arise post-construction, the solutions often become costly, intensive, and at times, impractical or infeasible.
NV Dynamics collaborates with leading civil design and construction teams to proactively assess designs and offer guidance on how to incorporate and account for operational loads. Statistics show that this timely intervention has led to improved structural designs and enhanced long-term operational performance.