The method applies to a class of buildings that dominates urban landscapes across the seismic world: regular reinforced concrete structures of two to eight stories, with story heights not exceeding four meters, and without significant structural irregularities. These are the apartment blocks, schools, offices and mixed-use buildings that line the streets of Istanbul, Athens, Santiago, Manila and countless other cities sitting near active faults. The procedure covers both frame-only systems, in which moment-resisting frames carry all lateral loads, and dual systems that combine frames with structural walls. By targeting precisely this building stock, the researchers have aimed their tool at the scale of the problem where improved preliminary design can save the most lives.

What makes the approach remarkable is its economy of input. Rather than demanding a complete structural model, the simplified method requires only estimated gravity loads, column tributary areas, the number of stories, story heights, plan areas, and the short-period design spectral acceleration for the site. From these basic quantities, the procedure uses fundamental mechanics of materials and minimum reinforcement requirements to proportion beams, columns and walls so that the resulting structure achieves adequate strength, stiffness and ductility at both the member level and the system level. In other words, the method embeds the core lessons of decades of earthquake engineering, capacity design principles and ductile detailing into a streamlined calculation sequence that a practicing engineer can complete in minutes rather than days.

The intellectual lineage of the procedure stretches back decades. Uğur Ersoy, one of Turkey’s most influential reinforced concrete researchers, developed the original formulation, which drew on international experience with simplified design guides, including the American Concrete Institute’s simplified design documents, Japanese seismic provisions, and the empirical wall-index observations of Shiga and colleagues after Japanese earthquakes. That heritage matters because the method is not an abstract exercise; it distills field evidence about which buildings survived past earthquakes and why. Buildings with sufficient walls, well-proportioned members and sensible proportions have repeatedly performed better in Chile, Japan and Turkey, and the new procedure translates those observations into explicit design rules for the modern code environment.

The real test of any simplified method is whether its output can survive scrutiny by the most demanding analysis tools available. The research team put 27 buildings, 11 frame-only structures and 16 dual frame-wall systems, through nonlinear static pushover analyses. Every one of these buildings was designed solely with the simplified method, using realistic and hypothetical configurations representative of actual practice. The pushover analyses pushed each structure laterally until its components reached defined performance limits, allowing the researchers to evaluate performance levels and shear demand-to-capacity ratios for every beam, column and wall according to ASCE 41-23, ACI 369.1-22 and ACI 318-25, three of the most authoritative standards in American structural engineering practice.

The results are striking. Under the design-basis earthquake, columns and walls in all of the evaluated buildings achieved at least the life safety performance level, the standard that ensures structural elements may be damaged but remain able to protect occupants. Beams, which are intentionally detailed to yield and dissipate energy before more critical members do, ranged between life safety and collapse prevention, exactly the hierarchy that modern capacity design seeks to enforce. Shear capacity proved adequate for nearly all members, with the only exceptions being a few short-span beams that fell outside the method’s stated applicability limits, a finding that reinforces the importance of respecting the boundaries within which any simplified tool is valid.

Comparisons with designs produced through the full TBER 2018 code route revealed another important property: the simplified method provides an acceptable level of conservatism. That conservatism manifests primarily in member dimensions rather than in reinforcement quantities, meaning the procedure tends to produce somewhat larger columns, beams and walls while keeping steel demands reasonable. For practitioners, this is a reassuring outcome. It suggests the method erringly errs on the side of robustness, giving early-stage designs a comfortable margin that will be refined, but not radically overhauled, in the final code-compliant design phase that follows.

The urgency behind this work is impossible to separate from recent seismic tragedy. The February 2023 Kahramanmaraş earthquake doublets in Türkiye, with magnitudes of 7.8 and 7.6, caused catastrophic damage to thousands of reinforced concrete buildings and prompted a wave of reconnaissance studies documenting failures that better preliminary design could have prevented. The study’s reference list is punctuated with field reports from that disaster and from earlier Turkish earthquakes in Kocaeli, Bingöl and Van, alongside lessons from the 1985 Chile and 1995 Kobe events. This context gives the research its emotional weight: every paragraph of the validation effort is ultimately about preventing the next collapse, particularly in a country where millions of people live in buildings of exactly the type the method addresses.

The researchers are careful to position the tool correctly within the design workflow. The simplified method is a preliminary design procedure, not a substitute for final structural design. It dispenses with elaborate analysis at the concept stage, when architects and engineers are negotiating layouts, column grids and wall locations, and it guarantees instead a minimum acceptable level of seismic performance from the very first sketch. The final code-compliant design, with its full three-dimensional modeling, modal response spectrum or time-history analysis, and detailed reinforcement design, is performed subsequently. By front-loading seismic competence into the earliest decisions, the method prevents the most dangerous failure mode of the design process itself: the discovery, late in the project, that the chosen architecture cannot be made seismically sound without painful and expensive redesign.

The authors conclude that the simplified method offers a practical, intuitive, rapid and reliable tool for the preliminary seismic design of regular low- to medium-rise reinforced concrete buildings. In an era when performance-based design has become increasingly sophisticated and computationally demanding, there is something quietly revolutionary about a procedure that argues for simplicity as a safety feature. Complex codes are only as effective as the practitioners who apply them correctly, and the gap between cutting-edge analysis and everyday practice is where many seismic vulnerabilities are born. By closing that gap with a method grounded in mechanics, validated against modern performance standards, and now written into a national seismic code, this research demonstrates that sometimes the most powerful engineering innovation is the one that makes doing the right thing the easiest thing to do. For the residents of eight-story apartment buildings from Istanbul to wherever the next great earthquake will strike, that simplicity may prove to be the difference between a shaken building and a collapsed one.

Subject of Research: Simplified preliminary seismic design of low-to-medium rise reinforced concrete buildings

Article Title: A simple preliminary seismic design procedure for low-to-medium rise reinforced concrete buildings

Article References: A simple preliminary seismic design procedure for low-to-medium rise reinforced concrete buildings. (n.d.). https://doi.org/10.1007/s10518-026-02696-2

Image Credits: AI Generated

DOI: 10.1007/s10518-026-02696-2

Keywords: seismic design, reinforced concrete, earthquake engineering, preliminary design, TBER 2018, ASCE 41-23, pushover analysis, dual systems, moment-resisting frames, life safety, capacity design, Bulletin of Earthquake Engineering