Structural design of a house in Batumi: calculations, seismic loads, drawings

Structural design of a house: what the engineer calculates

The structural design of a house answers the question of what the house stands on and why it will not fall down. The structural engineer collects the loads from the weight of the house, furniture, people, snow and wind, adds earthquakes, and calculates the foundation, columns, beams, floors and stairs. The result is drawings with member sizes, concrete grade, rebar diameter and spacing, details and schedules. The crew ties the rebar from them, and technical supervision checks it was tied correctly.

What the section includes

• load collection and a structural model of the building;
• seismic analysis to Georgian codes;
• a foundation based on the soil report;
• columns, beams, walls and floors with reinforcement;
• stairs, cantilevers, balconies and terraces;
• rebar and concrete schedules by element.

Without a soil report the structural engineer cannot honestly calculate a foundation: they either build in a large margin or take a risk. Which surveys are needed is on the geotechnical survey page.

Seismic loads

Adjara is in a seismic zone, and that is the main thing that sets calculations here apart from those in calm regions. What matters is not only column sizes but also the details: tie spacing near supports, anchorage of beams into columns, the connection of floors to walls, and symmetry of the building's stiffness. An elegant cantilever or a large opening without a column is possible, but only if the structural engineer has calculated it. How houses are built for earthquakes is on the earthquake-resistant construction page.

Drawings for the crew

A good structural section can be read on site without calling the engineer. For each element there is a formwork drawing, a reinforcement layout with bar marks, a schedule and notes: concrete grade, cover, lap positions. What this looks like on site is on the reinforcement page.

Slopes and retaining walls

On a slope the structure of the house and of the plot cannot be separated: foundations at different levels, retaining walls that hold back the soil and sometimes the house itself, drainage behind the walls. A retaining wall taller than a person is calculated as seriously as the house itself, because after a downpour it holds back not only soil but water too. How foundations are built on a slope is on the foundations on slopes page.

Checking someone else's design

If someone else made the design, a structural engineer can check it: are the calculations sufficient, do the drawings match the architecture, are seismic loads and soil taken into account. We often find that the structure was done "for the permit" without working details, or the foundation was calculated without a soil report. It is better to find out before construction, while a fix costs the designer's time rather than concrete and rebar. On site, technical supervision makes sure the section is followed; more on the technical supervision page.

How much structural design costs

The structural section of a design with seismic analysis costs from 27 ₾ per m². Foundation calculations and working drawings based on the soil report from 1 680 ₾, a retaining wall calculation taking the soil into account from 2 520 ₾. A structural engineer's check of a finished design from 1 680 ₾. A geotechnical survey from 3 000 ₾, a structural survey for an extra storey or reconstruction with calculations from 4 200 ₾. The final cost is set after reviewing the architecture and the soil report and agreeing the scope of the section.