Deflections must always be considered in slab design to meet the serviceability criteria applicable to concrete floor systems. While there are several ways to determine and calculate slab deflections, Tekla Structural Designer is arguably the most capable software solution available.
Kenny Arnott, Principal Structural Consultant at Trimble Solutions (UK) Ltd explains why.
There can be many requirements to consider when evaluating concrete floor deflections: the deflection (slope) of a slab must not be noticeable to occupants, and deflections must not cause damage to attached partitions, sheathing, and other critical non-structural elements. The most basic requirements are stipulated in the design codes, but very often more onerous project-specific limits will apply.
Flat slabs" (concrete slabs supported directly on columns/ walls without the stiffening effect of beams) offer the greatest concern and challenges in this area. Although buildings have been constructed using flat slabs and columns for many years, serviceability compliance (deflections) was traditionally evaluated by hand, without the aid of computers. However, this traditional method relied heavily on regularity, standard conditions and limits to keep design complexity to a minimum. As structures became more individual and complex, more innovative solutions were required to perform the necessary analysis.
Therefore, a growing selection of specialized slab design software became available to help engineers analyze and calculate deflections more easily. While this was good news for engineers, it meant that a variety of different software solutions would have to be purchased to meet these requirements. This in turn meant that engineers could end up creating separate analysis/design models in multiple software packages for a project. Any changes, such as column position/size adjustments, would need to be applied separately to keep them in sync with the project's master model. In fact, as you can imagine, this could become a time-consuming and potentially error-prone task.
As such, Trimble invested significant time in the development of Tekla Structural Designer to modernize the way engineers calculate slab deflections. This revolutionary software gives engineers the power to analyze and design buildings efficiently and cost-effectively.
Tekla Structural Designer is a fully automated structural design software, packed with many unique features to optimize concrete and steel design, helping engineering firms win more work and maximize profits. In terms of calculating slab deflections, Tekla Structural Designer follows the guidance of Concrete Society Technical Report 58, which advises on the interpretation of Eurocode 2. It uses iterative analysis of the crack section of a sequentially loaded slab/structure to not only accurately estimate the total life deflection, but also deflection at various construction load stages of the engineer's choice. All the different idealizations can be viewed simultaneously in one model at the same time to ensure optimum design time and ease of use.
The results of this complex analysis are displayed as contours of total deflection at any load stage, differential deflection between any two stages, effective reinforcement and slab stiffness. Our unique checkline feature allows quick pass/fail recognition of any total or differential deflection limit the engineer deems appropriate, which can then be reported at the touch of a button.
Perhaps the most notable aspect of this is the cutting speed with which Tekla Structural Designer is able to handle such a complex task. By producing results so quickly, engineers have much more freedom to make changes and rerun the program to ensure that the overall design is as optimal as possible.
Tekla Structural Designer has completely modernized the way people design concrete and steel structures; it is a convenient and painless process.
Stuart Vaughan, Director of Wentworth House Partnership, said, "We have been using Tekla Structural Designer for approximately five years as it allows us to model complex geometry, saving valuable time on site and producing a more accurate analysis compared to using a 2D method. We have also recently combined Tekla Structural Designer with Tekla Structures to enable us to produce coordinated construction information and fabrication drawings."
