How can you design a structure that meets deflection criteria?

Design a structure meeting deflection criteria by: 1. Analyzing Loads: Consider all applied loads and their effects. 2. Material Selection: Choose appropriate materials with suitable stiffness. 3. Section Design: Optimize section sizes for minimal deflection. 4. Structural System: Use efficient structural systems to reduce deflection. 5. Limit State Design: Ensure compliance with deflection limits in relevant design codes. 6. Support Conditions: Establish proper support conditions for reduced deflection. 7. Continuous Monitoring: Implement regular monitoring during and after construction.

Designing to meet deflection criteria poses a challenging task, particularly given the close relationship between deflection and the moment of inertia of a structural member. Constraints on member size often limit the effectiveness of using high-quality materials alone. One viable method to address deflection criteria, especially under dead load conditions, involves the strategic application of pre-camber to the member prior to installation. Calculating the pre-camber amount based on dead load deflection offers a systematic approach to achieve desired performance standards.

Designing a structure meeting deflection criteria involves defining requirements, selecting materials for stiffness, optimizing dimensions for strength and stiffness, configuring supports strategically, ensuring even load distribution, considering long-term effects, using accurate structural analysis, incorporating reinforcement and prestressing, employing an iterative design approach. This comprehensive process ensures compliance with deflection criteria and long-term structural stability.

Deflection is a serviceability issue in Structural Engineering. It should be addressed as per governing codes and user comfort.

There are two types of deflections. One is short term (initial) deflection due to permanent loads applied. And other is long term deflection, In case of concrete structures,long term deflection includes effect of creep, temperature and shrinkage. For any important member, it is advisable to check the long term deflection to avoid excessive cracking in the member and to avoid failure.

The most important thing in this step is to model the slab section considering the cracks that happens in the working stage which affect calculated deflection value ... it is can be done by two methods : 1- performing linear analysis with section modifiers definition after calculating the effective inertia (Ieff). 2- performing nonlinear analysis with section RFT and concrete modulus of rapture definition in software .

I had an experience in implementation of a 35 meter length steel truss bridge for crossing a waste water pipe line with the 3 part those length were 10 meter. It’s obvious in assembling this structure, we must be considering the negative deflection for avoid of installation positive deflection. it’s necessary that notice in designed drawings. The inexperience designers do not apply this in their sketch’s and drawings. For this purpose, we did act 17cm negative deflection with the putting steel scheme gasket between flanges. Finally we have a good looking steel truss.

Once geometry, material or stiffness is changed, be sure to check the failure criteria to ensure it meets the design expectations (i.e. by stiffening an element, the stresses in the structure can be reorganized in such a way that an element may then be subjected to a fragile failure mode or to local instability).

Remember to be as precise as possible with the load combination or load that is producing the deflection. It is very common to take into account Live Load + Dead Load, but this depends on the standard, and also take into account the combined accidental effects (earthquake, wind) when applicable.