Hi, .. . . Eng. Anas Dawas. I'm glad to try to help you on this.
I understand your question and I had to expand my DATABASE to answer with full experience.In Brazil we do not have Earthquakes so I had a limited experience in this design. Because of this, I was thinking if the transfer beam with D-REGIONS and I was associate to STM approaches initially to solve localized structural themes like beam openings and variable depth, and so specific optimizations like that:
So Let's try to solve this!!
I do some personal research and here some of my thoughts:
*Unsymmetrical forms of building can have low performance than those with symmetric configurations.
I supposed that I am seeing a structural concrete seismic resistant frame "MRF" and assuming you are giving preference to the selection of a "Structural Concrete Frame" to advance with your answer.
Essential items in the ASCE 7-16:
CHAPTER C2 COMBINATIONS OF LOADS
C2.3.6 Basic Combinations with Seismic Load Effects
"The seismic load effect including overstrength factor, Em, is combined with other loads. The purpose for load combinations with overstrength factor is to approximate the maximum seismic load combination for the design of critical elements, including discontinuous systems, transfer beams and columns supporting discontinuous systems, and collectors. The allowable stress increase for load combinations with overstrength is to provide compatibility with past practice".
C12.3 DIAPHRAGM FLEXIBILITY, CONFIGURATION IRREGULARITIES, AND REDUNDANCY
C12.3.2 Irregular and Regular Classification
. . . The configuration of a structure can significantly affect its performance during a strong earthquake that produces the ground motion contemplated in the standard. Structural configuration can be divided into two aspects: horizontal and vertical. Most seismic design provisions were derived for buildings that have regular configurations, but earthquakes have shown repeatedly that buildings that have irregular configurations suffer greater damage. "This situation prevails even with good design and construction."…
C18.104.22.168 Vertical Irregularity
Vertical lateral force-resisting elements at adjoining stories that are offset from each other in the vertical plane of the elements and impose overturning demands on supporting structural elements, such as beams, columns, trusses, walls, or slabs, are classified as in-plane discontinuity irregularities (Type 4).
C22.214.171.124 Elements Supporting Discontinuous Walls or Frames.
. . . The purpose of requiring elements (e.g., beams, columns, trusses, slabs, and walls) that support discontinuous walls or frames to be designed to resist seismic load effects including overstrength is to protect the gravity load-carrying system against possible overloads caused by overstrength of the seismic force-resisting system. Either columns or beams may be subject to such failure; therefore, both should include this design requirement. Beams may be subject to failure caused by overloads in either the downward or upward directions of force. Examples include reinforced concrete beams . . .
"The connection between the discontinuous element and the supporting member must be adequate to transmit the forces required for the design of the discontinuous element".
*First of all, we might recognize THAT D-REGION IS ALWAYS IMPORTANT WHEN SHEAR FORCES EXISTS!!
*So I performed an additional Structural Analysis as well. . . for this simply imaginary simulation:
*In my view – It Would be important give concern where the ABRUPT CHANGES in GEOMETRY can cause the UNCONVENTIONAL FLOW on the SHEAR forces. Designing the TRANSFER BEAM and the 2 COLUMNS BELLOW would be interesting to increase RESILIENCE: (TB, C and B) or +A in the future if you plan to remove column "B" in order to CREATE some additional Aesthetics SPACE between the C- - -A.
I think it was my first time on this topic (SEISMIC), I hope it would be right on the majority of the explanations, if not, things not all the time have to be perfect, sometimes correct me as well if needed.Thanks, Andre.
. . . and you can find an additional material over this question linking the JOINT SEI, CASE and NCSEA and the STRUCTURE MAGAZINE Initiative, by accessing our colleague: Emily Guglielmo, P.E., C.E., F.SEI:
Anas, your concern on the SEISMIC RESISTANT FRAMING SYSTEM made me reflect upon SHEAR. . . it is not only a SEISMIC concern, as it opened my mind to the Dangerous into general Structures. . .
I do think 3 Major Areas can be enhanced and really Motivate STRUCTURAL ENGINEERS for the Future: "Earthquake, Impact and Blast". And the reason for that is they are governed by special envelopes, I can imagine why Shear effects sometimes are not well covered along the years (neglected). Because the codes of practice might have been test for conventional structures, so with different and newer structures it still remains uncertainty, specially when reinforcement are not present. Elements without proper reinforcement are critical! Therefore, We should pay more attention on the design. Over repair is costly as well, and in some cases the structure has already collapsed and it is difficult to save human lives.
In STRUCTURAL ENGINEERING, future designs with SHEAR can be critical. Some reduction in member sizes not always compensate structures for being light, with drastic changes in geometries to a more intense energy flux the element goes heavier, thus the subject is on a higher stress, the elegant design must be complex and simply at the same time to attend several different perform objectives like thermal or deflection, or at least his own self load (dead load). And it bring us to the case where every single point (D-region) of the structure matters. Unreinforced SHEAR is a common practice for Structural Elements such as: retaining walls, footings, silos, and earth-covered structures, the cases of "simple slabs" sometimes might not require by codes to induce Stirrups (transverse reinforcement). We also should give more attention to the likely elements while SE Profession advances, trying to reduce the size and dimension that longer spans or high altitudes requires for optimization models that can be applied to general structures in a small and large scale. We might have to invent something flexible, high adaptable that are far away from our current technique of design, but we also have to think in present time. Maybe structures would not be made of concrete, but they can modify themselves or incorporated in something new. Maybe we can reach this new level in the next years far from those questions.
With all this in mind, we must remember how advancements will not neglect something to deal with the new and unknow (we can call this uncertainty), and it can be climate change for now, misery for the masses, or an undiscovered phenomena or another type of risk to manage. We need imagination, but must validate somehow by testing, research and use our intuition to solve those big challenges to different possibilities and potential scenarios for favorable conditions.
The best way is to validated that, always before put those theories in practice.
thank you for this post!