Structural Design
Seismic Performance Assessment and Retrofitting
We calculate the seismic performance of existing buildings to TBDY 2018 using data we measure on site and results determined in the laboratory, and draw the retrofitting design where it is needed.
Seismic performance of an existing building
We assess the seismic performance of an existing building by measuring what is actually there. We take the column and shear wall dimensions on site. Concrete strength and the condition of the reinforcement come from laboratory results, and with this information we build a model and calculate which members fall short under the design earthquake. The report shows whether the building meets the target performance level; if it does not, the retrofitting design starts from that result.
We usually do this work for owners who want to add a story or change the use of a building. The same question comes up when an industrial building is adapted for a new business. Owners who want to know the condition of their building and organizations that manage public buildings also come to us. Gölcük and its surroundings have many buildings built before the 1999 Kocaeli earthquake. For these we ask for on-site testing rather than calculating with the concrete class and reinforcement written on the drawings. Besides reinforced concrete buildings, we have also assessed listed masonry buildings and existing steel structures such as a steel canopy.
When we hand over the report, we go through the drawings with the owner, showing which member falls short and why, and what the intervention we propose will change. We set the retrofitting options side by side with their costs and their effect on the use of the building; the owner decides which one is built.
Scope of services
On-site inspection and as-built survey
We measure the structural system on site and mark member dimensions, grid misalignments and visible damage on the plan. Where no drawings can be found, we draw the as-built survey from scratch.
Material testing
Core sampling and reinforcement detection are carried out by authorized laboratories. We plan which members are sampled and at how many points, and carry the result reports into the calculation.
Performance assessment
We determine the knowledge level to TBDY 2018, model the building and check each member individually. Where necessary we also run a nonlinear analysis.
Comparing the options
We weigh up the retrofitting options with the owner in terms of cost, construction time and whether the building has to be vacated.
Retrofitting design
We repeat the analysis for the building strengthened with the chosen method and prepare the calculation report, construction drawings and execution details.
During construction
If removing the plaster reveals something different from the as-built survey, we look at the member on site and update the detail.
Applicable regulations and standards
The assessment and retrofitting design of existing buildings is carried out under Chapter 15 of the Turkish Building Earthquake Code 2018 (TBDY 2018). The knowledge level is set according to the extent of the information collected from the building, and the material strengths used in the calculation depend on that level. If the survey and tests are incomplete, the building can appear weaker in the calculation than it really is. TS 500 (the Turkish standard for the design of reinforced concrete structures) is used for the reinforced concrete design of strengthened members, and TS 498 for load values.
Risky-building assessment under Law No. 6306 on the Transformation of Areas under Disaster Risk is carried out by institutions licensed by the Ministry. We do not carry out risky-building assessments. When one is needed, we refer you to a licensed institution and take on the technical coordination in the process. Our work is the performance assessment and the retrofitting design.
How we work
First meeting and documents
We ask for the approved drawings, the permit and ground information if they exist. In this meeting we talk about earlier alterations to the building and what you want to do.
On-site inspection
We carry out the as-built survey and record the structural members and visible damage with photographs and notes.
Material and reinforcement testing
An authorized laboratory takes the cores and detects the reinforcement. We mark the points; the knowledge level is settled once the results arrive.
Analysis
We build the model, find the performance level of the building and report the inadequate members one by one.
Retrofitting design
We select a suitable method, analyze the strengthened structure again and draw the construction drawings.
The main retrofitting methods are reinforced concrete jacketing of columns, new reinforced concrete shear walls added inside or outside the building, fiber-reinforced polymer (FRP) wrapping to increase shear and axial capacity, and steel bracing in suitable structures. Most projects use several of them together. The choice depends on the concrete strength, the existing reinforcement, whether the foundation can carry the extra load and whether the building stays in use during the works. In buildings that receive new shear walls, foundation strengthening is part of the design.
Deliverables
- As-built survey drawings and on-site inspection notes
- Evaluation of the material test results
- Seismic performance assessment report
- Retrofitting calculation report
- Retrofitting construction drawings and execution details
- Summary of approximate construction quantities
Frequently asked questions
Can I get a risky-building report?
Not from us. Under Law No. 6306, risky-building assessment falls within the authority of institutions licensed by the Ministry. If needed, we refer you to a licensed institution.
Does a performance assessment mean breaking into the building?
Yes, at a limited number of points. The plaster and concrete surface is opened up for core sampling and reinforcement detection, and these points are repaired after the laboratory work. We choose sampling points where they will not weaken the structural member and will disturb the use of the building as little as possible.
Can the building be occupied during retrofitting?
It depends on the method. Solutions such as shear walls added from the outside or FRP wrapping disturb use less. We answer this question when we compare the options.
Can every building be retrofitted?
No. Where the concrete strength is very low or the structural system is heavily damaged, retrofitting may not be economical. If the result points that way, we say so plainly in the report.
Is the retrofitting design submitted to the municipality?
Yes. Retrofitting work that intervenes in the structural system needs a permit from the relevant authority, and the work itself is carried out under authorized supervision. We prepare the design in a form that suits this application.
Examples from practice
Our projects in this field
- Seismic performance assessment of a registered historic masonry museum buildingYalova · 2023
- Seismic performance assessment of a multi-story reinforced concrete library buildingKocaeli / İzmit · 2023
- Seismic performance assessment of a two-story reinforced concrete library buildingKocaeli / Gölcük · 2023
Request a quote for your project
Write to us with the type of building, its location and the documents you have. We will agree the scope and timeline with you and send a written quote.