masonry infill panels designed not to take any seismic inplane forces
masonry infill panels designed not to take any seismic inplane forces
(OP)
I am conducting a reference design of masonry infill panels inside a concrete frame which has been designed to seismic design category B. Masonry infill panels must be detailed in such a way that it will not perform as a shear wall under ground seismic movement. This might be achieved by isolating the masonry panel from the primary frame (UBC 97 method) but this will weaken its out-of-plane strength and the wall may fail as a result of internal wind pressure. I reckon a few concrete wind posts are needed together with horizontal tie bars to ensure its out-of-plane integrity. I am not familiar with American codes. Are there any codes/standards or good practice guides for this calculations/detailings. Another question is: is there any restriction on masonry infill panel deflection for seismic design?
I wish to thank you all in advance.
I wish to thank you all in advance.






RE: masonry infill panels designed not to take any seismic inplane forces
RE: masonry infill panels designed not to take any seismic inplane forces
It may be built according to current ideal assumptions, but will change over time to where the in-fill panels begin to take up and redistribute loads.
Many studies on the subject and behavior have be made internationally because this type of construction is common in multi-story apartments and commercial buildings. The lack of real original construction information on older buildings is highly variable. I do not know of any specific studies, but most of the work I heard about was from Central and South America where the constuction was common to produce old buildings today where the long term effects can be observed. It is avery complex combination of variable material properties and loading.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: masonry infill panels designed not to take any seismic inplane forces
Wind post and horizontal bars will be required for this case. Wind post alone is not going to keep all blocks work together under crowd load and/or internal pressure as arching action is not going to come into being without a solid contact with the main frame.
I had ordered appropriate American codes for masonry infill panel design, i.e. TMS402/ACI530/ASCE5. Infill panels and wind posts will be designed separately. I will think about the issues arising from masonry creep and concrete shrinkage, i.e. gaps between two media will be decided after considering all these factors.
RE: masonry infill panels designed not to take any seismic inplane forces
DaveAtkins
RE: masonry infill panels designed not to take any seismic inplane forces
But the wall is going to be 4.4 meter tall and over 8 meter long (this means I need movement joint to cope with temperature change). I have not got the American masonry code yet but I really doubt it can stand in one-way and also in a decent thickness.
My friend in the US said that typically two criteria would be required for my case:
1) Infill panel height <4m
2) Height/thickness<30
Shall I place a beam when the height exceeds 4m? Or satisfying the second criterion only is going to be sufficient.
RE: masonry infill panels designed not to take any seismic inplane forces
RE: masonry infill panels designed not to take any seismic inplane forces
That is why I wish to place a wind post by the column (but with a gap) and this post, together with tie bars, will give an encastre boundary to the panel (its top is only restrained in horizontal direction).
RE: masonry infill panels designed not to take any seismic inplane forces
American codes are weak on the subject and may not address it because it is used quite rarely compared to other locations.
Clay brick are a problem because the long term effects of the material are different from the concrete in the frame. If concrete block are commonly used, the isolation situation is minimized because the CMUs have properties similar to the concrete frame. The block are usually cured when laid while the concrete frame will shrink as it cures. The construction process becomes a factor. On larger structures, the frame is usually in place long before (weeks) the infill is placed. For the more common smaller project the process is different and floor-by-floor construction is common.
On smaller structures (residential and 2-3 story apartments, the panel dimension are smaller and the masonry is used in interior walls the studies of performance have been very positive when the panels are not isolated. In a seismic event the panels work with the frame and translates the structure into a "bee-hive" or honeycomb structure with great rigidity. There may be some minor cracks that can be repaired easily, but with maximum wall spacing of 4 meters and poured in place concrete floor slabs, the life safety is not a problem and repairs are minimal.
In some countries, 20 story apartments in large complexes are built with interchangeable designs (6" loadbearing concrete masonry of different specified strengths or a frame of 6" thick by ??? inch columns with 6" CMU infill) on a single site of buildings.
Bottom line - The effects of the infill material (and its long term shrinkage/expansion) on the frame and then most importantly, the panel dimensions, since that represents the greatest area of the frame/panel combination, depending on the construction process.
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: masonry infill panels designed not to take any seismic inplane forces
Clay masonry: <15m (more frequent spacing of movement is required if different types of clay units are used. Or cladding is used.)
Calcium silicate masonry: 7.5m~9m
Concrete masonry: 6m~9m
Compressible joint is also required for external walls but required difference between spacing is greater than those required for contraction joints.
RE: masonry infill panels designed not to take any seismic inplane forces
RE: masonry infill panels designed not to take any seismic inplane forces
DaveAtkins
RE: masonry infill panels designed not to take any seismic inplane forces
I see the meat of the question as how one details the panels so that they do NOT contribute to the lateral force resisting system.
I have a similar multi-story problem in hand in that the owner wants solid walls for hygiene reasons (food facility - no gaps or hollow areas) but wants to wait until the last minute to decide where the walls will be. Many of the walls need to be designed as removable (for future equipment openings) and/or don't extend all the way to the foundation. We agreed on a concrete frame rather than shear walls but we still need to detail a system whose walls either don't contribute, or if they do works with these "accidental" shear walls in place. It is turning out to be a real challenge - even in SDC B.
RE: masonry infill panels designed not to take any seismic inplane forces
Why dont you use a sacrificial drywall that can be replaced after an earthquake?
RE: masonry infill panels designed not to take any seismic inplane forces