Tzvetan Georgiev

University of Architecture, Civil Engineering and Geodesy · Department of Steel, Timber and Plastic Structures

AUTHOR'S SUMMARY of PhD THESIS - Extended English version

The X-braced frames are among the most used seismic resistant systems in the steel construction. In spite of their long historical development, the observed seismic behaviour during past earthquakes indicates that the traditional design cannot avoid disadvantages of brittle fracture or low cycle fatigue failure of the diagonals. The current seismic...

1. ABSTRACT An analysis of specificity in the hysteresis behavior of X-CBFs is presented. Attached is a brief overview of the undesirable modes of brittle fracture in the diagonals of such structures, often observed in the past earthquakes. A new approach for composition of frames with cross braces is developed by introduction of horizontal strut a...

Concentrically braced frames with X-bracing configuration (X-CBFs) are one of the most popular systems for seismic resistant design. Their ductile behaviour is provided primarily by yielding of braces in tension and to a small extent by plastic rotation in buckled braces. An improved CBF configuration by introducing bracings with modified sections...

The current paper presents a characteristic aspect of cyclic non-linear behaviour of steel concentrically braced frames with braces, intersecting into a floor beam (Split-X CBFs). Through experimental programme three test specimens of one-bay one-storey Split-X CBF with braces of H-cross section were tested under fully reversed cyclic constant ampl...

CFD ESTIMATION OF WIND LOADING ON A STADIUM ROOF D. Dinev , St. Raykov , Tzv. Georgiev Keywords: computer simulations, CFD, wind load, stadium roofs, aerodynamic lee effect ABSTRACT The wind effects on buildings or large facilities with a complex shape cannot be recognized within the recommendations of the design codes and usually are studied exp...

COMPARISON OF WIND LOAD FOR GRANDSTAND CANTILEVER ROOFS DETERMINED ACCORDING TO DIFFERENT DESIGN CODES Tzv. Georgiev , St. Raykov , D. Dinev Keywords: wind load, stadium roofs, design codes, Ordinance № 3, EN 1991-1-4 ABSTRACT The report overviews the recommendations for assessment of wind pressure coefficients of stadium cantilever roofs. Approp...

WIND LOADING ON STADIUM ROOFS: AN OVERVIEW St. Raykov , Tzv. Georgiev , D. Dinev Keywords: wind actions, roofs on stadium grandstands, wind tunnel, stadiums ABSTRACT Modern sports stadiums are facilities with wide range of architectural forms and structural systems, designed to comply with several different requirements. In recent years, one of t...

TWO-STOREY CONCENTRICALLY BRACED FRAMES WITH BRACES INTERSECTING A FLOOR BEAM. SPECIFICITIES CONCERNING SEISMIC DESIGN L. Raycheva , Tzv. Georgiev Keywords: seismic behaviour, concentrically braced frames, design issues, Split-X ABSTRACT Concentrically braced frames (CBFs) are one traditional structural system for bearing horizontal loads, inclu...

ORDINANCE FOR EXECUTION OF STEEL STRUCTURES. ESSENCE, NECESSITY AND OBJECTIVES Tzv. Georgiev , St. Raykov , V. Georgiev Keywords: steel structures, fabrication and erection, code of practice, BDS EN 1090-2: 2018, execution class КИ ABSTRACT Recently, the authors of the report took part in a working group engaged by section Metal Structures of the...

The authors represent a team who visited the areas affected by the strong earthquake of 26 th November 2019 as part of the Bulgarian state support to Albania. The task of the Bulgarian experts comprised a rapid visual assessment of buildings in Tirana, as members of small international groups of structural engineers, local engineers and representat...

Modern societies need built-up environment and once built, the buildings are in operation for 25, 50, 70, 100 and even more years. Thus, the ratio between the numbers of new constructions created according to the latest advances in engineering science and construction technologies and existing older generation constructions is always and worldwide...

Concentrically Braced Frames are a traditional system for seismic resistant design of buildings and engineering facilities. They are well known in the engineering community and are included in all modern seismic design codes [1, 2, 3]. In order to keep the major advantages of that system and in search of improvement of their seismic behaviour a res...

Eccentrically braced frames are a worldwide well-known and often used structural system for earthquake resistant design in areas with high seismic hazard. A specifically designed element, named “link”, accommodates the plastic deformations caused by strong earthquakes. Plastic strain is restricted within the link and the rest load-bearing elements...

Concentrically braced frames with crossed diagonals (X-CBFs) are a popular and traditional system in seismic resistant design. Their energy dissipation capacity is primarily provided by yielding of braces in tension and buckling in compression. An improved CBF configuration by introducing bracings with modified sections, resulting in low cycle fati...

The accurate and reliable determination of the slip factor is the basis for safety in the design and construction of high strength slip resistant bolted connections. Changing the regulatory framework, evolution of the construction practices and new materials in the steel construction sector require updating of knowledge regarding these bolted conne...

The paper describes and discusses the administrative, legislative, academic and educational aspects of the implementation of Eurocodes in Bulgaria and in particular the Eurocode 3. Related with that global process of standard harmonization, educational and regulation changes, some unavoidable economic, social and even psychological problems rose in...

1 Ключови думи: болтови съединения, въртящ момент, лабораторни тестове, високоякостни болтове, предварително напрягане. Научна област: стоманени конструкции РЕЗЮМЕ Точното определяне на опънната сила във високоякостните болтове, използвани в болтови съединения категория С, е от особена важност в процеса на проектиране, реализация и контрол на отгов...

The precise calibration of the bolt tension force in bolted connections category C is of high importance for the safety and reliable design, execution and operating of the steel structures. The application of Eurocode 3 (EN 1993-1-8) and EN 14399 for bolt connection design leads to change of the already established design procedures and practices,...

1 Ключови думи: болтови съединения, въртящ момент, лабораторни тестове, високоякостни болтове, предварително напрягане. Научна област: стоманени конструкции РЕЗЮМЕ Точното определяне на опънната сила във високоякостните болтове, използвани в болтови съединения категория С, е от особена важност в процеса на проектиране, реализация и контрол на отгов...

ABSTRACT The design of dissipative structural systems for earthquake effects requires clear definition of the dissipative zones and adequate detailing. Nowadays the use a structural fuse concept has became a preferable design approach enabling engineers to control the ductile structural behavior trough design. This paper deals with the influence of...

Summary The use of reduced diagonal section for concentrically braced frames is discussed into the paper. The investigation of non linear behavior with plastic deformations of the bracing diagonal is done. Several studies by FEM models are performed using the ANSYS Workbench V12 program. Some conclusions about the influence of the reduced section u...

Неотдавна на един столичен строеж се появява странния надпис “4 = 5”, вместо традиционния за такива места надпис с наименованието на строежа. В есенцията на това странно равенство “4 = 5”, всъщност се крие съдържанието на едно ново проектно решение за надстройка, позволило, чрез използването на лека стоманена конструкция (вместо традиционната за сл...

The main goal for applicability of moment resisting steel frames (MRSF) for construction needs in seismic areas is the achievement of reliable and predictable performance of the structure. This paper discusses the seismic performance of ductile MRSF. A special join designed with compliance with the domestic technological equipment for production of...

Es werden Schlankheitsanforderungen zur Klassifizierung von Biegeträgern aus I‐Querschnitten unter Berücksichtigung des interaktiven Beul‐Biegedrillknickverhaltens gestellt. Dadurch kann entschieden werden, welches Nachweisverfahren angewendet werden soll oder darf. Der Vorschlag stützt sich an den Ergebnissen eines analytischen Verfahrens sowie ex...

S/enderness reaui'rements for the classification of beams with / cross sections are proposed, taking into account the interactive effects between local buckling and lateral torsional buckling. They serve as limits lor the application of different methods for analysis of steel framed structures. The proposal is based on the results of an analytical...

Parametric studies are carried out to evaluate the behavior factors of some typical for the Bulgarian construction practice steel moment resisting frames. Several frames are designed according to current Bulgarian codes and the capacity design procedure of EC8. The q-factors are evaluated by the modified version of the Akiyama-Kato energy based met...

The good performance of steel moment-resisting frames under seismic motions depends strongly on the behaviour of their beam-to-column connections. The Northridge earthquake generated an urgent need to increase the ductility of the connections normally used in practice. This paper presents the study of beam-to-column joints in column-tree configurat...