ACI,technical report 65 and minimum reinforcement under pure tension 1

[ramihabchi]

Hi,
1-aci 224R-95 refers to national academy of science to determine expansion joint spacing (attached graph)as one of many other methods.some reasearch says that it is the most realistic.Personally I think also that it takes into accound thermal loads so no need to include them in load combinations.the problem is that in 1995 load combinations of ACI were different than later which makes me question applicability of this attached graph with design being based on the new load combinations.I found that aci in 2008 had reapproved aci 224R-95.So my question is:does this approval means it could be used with the load combination of aci 318-08?(version of aci at time of approval)
2-I have searched codes for an approved way to determine expansion joint spacing for buildings with perimeter and inner shear walls but in vain all papers gives those for beam-column frame structure.so I decided to include thermal load using ACI 318-08 in the analysis and design of structure.the problem is that I do not find in aci a minimum reinforcement requirement to prevent brittle failure in section under pure tension as it is the case in eurocode/bael 92.I think I am missing something,shouldn't I put a minimum reinforcement in place where thermal loads effect is way greater than bending moment?and is there any common rule of expansion joint spacing in case of restrained structure by perimiter and inner shear walls?

 

[MotorCity]

The guide you have provided is simply that....a guide, and not associated with a particular code that I am aware of. To determine the expansion joint spacing, calculate the thermal expansion. Determine what amount of expansion would be objectionable. Determine the joint width and spacing of the expansion joint accordingly. As a sanity check, provide the larger of the spacing you calculated and that given in the guide. The structure will expand the same amount regardless of which code it was designed to. Thermal expansion is a function of the material, temperature, and length/area. Has nothing to do with load combinations. The FORCE generated from thermal expansion is what shows up in the load combinations.

 

[r13]

Thermal effect is the material's tendency to expend/shrinkage (movement) when subjects to change in temperature. Thermal force is the force exerts on the restraining supports that prevent the thermal movement. An expansion joint is designed to accommodate the change in length due to thermal effect, and keep the internal thermal forces to a tolerable level for a very large area under consideration. Usually, the reinforced concrete building is not very sensitive to temperature change, unless the variance is huge, such as furnace floor supporting structures, or roof of the parking garage. However, it would be quite critical for bridge design though.