Traditional stances for steel here (Spain) were 1/500 for floor not supporting structural walls and 1/250 for roofs, both under total service level loads. Lateral deflection was not initially a concern; buildings were RC framed or masonry mainly, and industrial buildings most times tension braced frames. When first appeared, some controls were used to discern building structures as non sway or sway, and industrial buildings had their day with portal frames of unsightly lateral deflections allowed in practice due to unclear specification in codes.
By now a RC building is allowed to sustain a 1/250 total actual deflection under the applied total service level load with a proper calculation of the deflection, including stiffness degradation by mechanical cracking and creep (obviously checked generally in approximate ways) AS LONG what is called the active deflection doesn't surpass 1 cm or 1/400 of the span. This active deflection is that occurring after the floor gets the loads applied, say weight of the floors, partitions, mechanical services and live loads, of course as well properly accounting cracking and creep. The rationale must be all deflection except that active will be hidden under non-structural parts and a remaining 1/400 movement is unnoticeable at sight, reasonable in stiffness for confort respect vibration, and reasonably conservative respect breaking partitions.
Of course if one plans to add structural walls above some framed structure must be more conservative. The traditional assumption for steel was to keep total deflection under total service level loads under 1/1000. For this case, from the deflection viewpoint, the stiffer, the better.
Finally most modern codes reckon even if in hidden way that deformation controls are as much a matter of distortion as of deflection. Rules are more complex, in the case of the steel having been here significantly relaxed, for where before strength almost never controlled design, being the deflection stiffness controls those that governed the selection of the member, now are more in agreement and a selection made directly in terms of strength can be valid also from the deflection viewpoint. This surely has been made to allow for agreement with other less stringent european codes and made by the summarily way of reducing both the limit deflections (between the 1/500 and 1/300 range, there is a range of hypotheses to check) and the part of service level Live loads (50%, 30% whereas before 100%) being brought to the check. This of course means steel vibration control, ponding issues will be more of concern from now on, before almost never were, and even the stiff steel members being used were NOT tasty to feet accustomed to the rigid concrete floors, so how less now.
CTE, the current, code, also very properly extends the requirements of deformation be brought to foundation matters, so proper estimates of total and differential settlement (dishing action etc) are required. These deformations are directly compounded with the deflections under loads and may break partitions where a mere deflection check wouldn't show it be the case. I have seen this to happen, and can say even where: buildings with H plan shape under general dishing action founded with floating piles in a deep mantle of clays, and U buildings (likely also in clays or weak soils) in the arms, likely also dishing action. These midrise cases showed structurally non-meaningful diagonal cracking at some partitions and could be repaired to tolerable level after primary settlement. In clayey soils if a crack remains open midterm on, likely you will have the crack open and closing seasonally, with cycles of overall rains and temperature.
So you have an idea of what to make in almost every situation. Keeping 1/500 or 1/400 under total service level load will get you outside of most typical problematic situations, but then be sure to have accounted in adequate way settlements. To keep up stiff walls, loaded or not, better go up, masonries crack even before 1/1000 shows.
A proper control of lateral deflection in the same ranges for masonries, and to the required level in structural P-Delta terms plus requirements of cladding (mainly allowed movement of glass panels in their casings) complete the most of the significant issues -other than vibration- relative to deformation controls.
These things surely should be complemented with distortion issues here, but for now leave here to not make it too long.
lease see FAQ731-376 for tips on how to make the best use of Eng-Tips.
