Wind load design of the ground-mounted photovoltaic (PV) power plants requires interpretation of ... more Wind load design of the ground-mounted photovoltaic (PV) power plants requires interpretation of the design code considering the particularities of these structures. The PV power plants consist on systems of several solar panels. Wind load pressure coefficient evaluation, by design code, for a single solar panel considered as a canopy roof, neglect the group effect and the air permeability of the system. On the other hand, the canopy roofs are structures with medium serviceability, but the PV power plants are structures with low serviceability. This paper discuss the difficulties of the wind load design for the PV power plants ground mounted in Romania and compares the Romanian, German, European and American wind design code specifications with the parameters provided by the wind tunnel test, for this type of structures. For Romanian wind load design an evolution of the 1990, 2004 and 2012 editions of the design codes specifications is also studied. Evaluation of the internal result...
In the last years BRB were used in existing structu res and in new ones as primary lateral force ... more In the last years BRB were used in existing structu res and in new ones as primary lateral force resist ing elements. Retrofit of existing buildings in seismic areas can be made by using buckling restrained bra ces (BRBs), because they have the ability to sustain la rge inelastic deformations without important loss o f strength. This study analyzes the possibility of using BRBs t o improve the seismic response of tall reinforced c oncrete buildings. Therefore dynamic nonlinear analysis was performed on two tall structures: first, one struc ture with reinforced concrete walls (that has been designed a ccording to the Romanian Seismic Design Code) and t hen he same structure with buckling restrained braces incl uded. Computation was made for three recorded accelerograms. The aim of the study was to highligh t the advantages and disadvantages of using BRBs to gether with reinforced concrete walls for improving the se ismic response of tall buildings. Parameters like n atural period, de...
This article presents a comparative study of the values of hydrodynamic pressure and their result... more This article presents a comparative study of the values of hydrodynamic pressure and their resultants occurred during the seismic action using P100-1/2013 technical rules and the relations defined in the papers:
This paper presents an analytical study which deals with the behavior of the circular plates in b... more This paper presents an analytical study which deals with the behavior of the circular plates in bending theory, considering the soil-structure interaction under Winkler's hypothesis. It was intended to illustrate the variation of internal forces and deformations according to the flexibility coefficient of plates considering three models: a fixed solid circular plate subjected to a uniformly distributed load, a fixed solid circular plate acted by a displacement applied on the exterior contour and a solid plate subjected to a temperature gradient. For this study the computation relations were written as a product between a dimensional and a non-dimensional factor, the last one indicating the variation of internal forces and deformations. For each type of action there are presented results obtained using the finite element method to illustrate the differences between this method and the analytical computation.
In current design practice, typical seismic design of bridges tends to use simplified approaches.... more In current design practice, typical seismic design of bridges tends to use simplified approaches. On the opposite side, the most advanced seismic analyses currently used in practice in all the fields of structural engineering are probably the ones used for the design of nuclear facilities, which include soil–structure interaction and motion incoherency effects. From that category, the most modern methodology is the probabilistic approach, which has been added to the new ASCE 4 standard. This type of state-of-the-art analysis is carried out in ACS SASSI software on a typical concrete bridge structure with deep foundations. A comparison of the results with the deterministic SSI approach and the typical Eurocode design from previous studies is presented at the end. Major differences in behavior are highlighted, which impact the overall safety of the structure.
... Considering critical sec-tions only at the column ends, the storey shear force may be calcula... more ... Considering critical sec-tions only at the column ends, the storey shear force may be calculated as ... Figures 6 and 7 show the time evolution of the roof displacement and base shear ... its oscillations are out of phase with the struc-ture oscillations during the earthquake excitation. ...
The paper presents selected results of an international project of the new research center in ear... more The paper presents selected results of an international project of the new research center in earthquake engineering entitled “Dan Ghiocel International Research Center” at Technical University of Civil Engineering, Bucharest, Romania. The paper investigates the seismic structure-soil-structure interaction effects (SSSI) in densely built urban areas for a 15 floor Multistory Building (MB), a Church Building (CB) and a Subway Station (SS) in the Bucharest city. A description of the SSI effects for each of the three standalone buildings is provided in a companion paper (Bogdan, Ghiocel and Cretu, 2014). Seismic input was defined by a set of three-directional spectrum compatible acceleration histories generated based on the Romanian seismic design spectrum for the Bucharest city area. The seismic SSI and SSSI analyses were performed using the state-of-the-art ACS SASSI software. Three SSSI layout scenarios were considered. The SSSI analyses were performed for both coherent (synchronous...
In this paper a functional model to estimate the inelastic displacement ratio as a function of th... more In this paper a functional model to estimate the inelastic displacement ratio as a function of the ductility factor is presented. The coefficients of the functional model are approximated using nonlinear regression. The used data is in the form of computed displacement for an inelastic single degree of freedom system with a fixed ductility factor. The inelastic seismic response spectra of constant ductility factors are used for generating data. A method for selecting ground-motions that have similar frequency content to that of the ones picked for the comparison is presented. The variability of the seismic response of nonlinear single degree of freedom systems with different hysteretic behavior is presented.
In the last years BRB were used in existing structures and in new ones as primary lateral force r... more In the last years BRB were used in existing structures and in new ones as primary lateral force resisting elements. Retrofit of existing buildings in seismic areas can be made by using buckling restrained braces (BRBs), because they have the ability to sustain large inelastic deformations without important loss of strength. This study analyzes the possibility of using BRBs to improve the seismic response of tall reinforced concrete buildings. Therefore dynamic nonlinear analysis was performed on two tall structures: first, one structure with reinforced concrete walls (that has been designed according to the Romanian Seismic Design Code) and then the same structure with buckling restrained braces included. Computation was made for three recorded accelerograms. The aim of the study was to highlight the advantages and disadvantages of using BRBs together with reinforced concrete walls for improving the seismic response of tall buildings. Parameters like natural period, deformations and stresses were carefully evaluated and then some comparatively studies were made in order to establish the efficiency of the buckling restrained braces.
The paper presents the results of a project of the new research center in earthquake engineering ... more The paper presents the results of a project of the new research center in earthquake engineering entitled "Dan Ghiocel International Research Center" at TUCEB, Romania. The paper investigates the seismic soil-structure interaction effects for different type of buildings, such as a multistory residential building, an old church and a metro subway station in the Bucharest city. The site soil profile corresponds to the INCERC site soil layering in Bucharest. This is a relatively soft and deep soil deposit. Two seismic inputs are considered: i) the 1977 Vrancea Earthquake acceleration records NS, EW and Vertical at the INCERC site and ii) a set of 3-directional spectrum compatible acceleration input histories simulated based on the Romanian seismic code design spectrum. The seismic SSI analysis was performed using the state-of-the-art ACS SASSI software (Ghiocel, 2013). The Flexible Volume (FV) substructuring method was used to perform accurate SSI analyses.
The paper presents selected results of an international project of the new research center in ear... more The paper presents selected results of an international project of the new research center in earthquake engineering entitled "Dan Ghiocel International Research Center" at Technical University of Civil Engineering, Bucharest, Romania. The paper investigates the seismic structure-soil-structure interaction effects (SSSI) in densely built urban areas for a 15 floor Multistory Building (MB), a Church Building (CB) and a Subway Station (SS) in the Bucharest city. A description of the SSI effects for each of the three standalone buildings is provided in a companion paper (Bogdan, Ghiocel and Cretu, 2014). Seismic input was defined by a set of three-directional spectrum compatible acceleration histories generated based on the Romanian seismic design spectrum for the Bucharest city area. The seismic SSI and SSSI analyses were performed using the state-of-the-art ACS SASSI software. Three SSSI layout scenarios were considered. The SSSI analyses were performed for both coherent (s...
The paper studies the influence of an optimal inter-storey isolation system on seismic behaviour ... more The paper studies the influence of an optimal inter-storey isolation system on seismic behaviour of a concrete structure. The inter-storey isolation system uses lead rubber bearings at a certain level of the structure. The structure will be subjected to a series of pulse like earthquakes in order to account for the variability of the hazard of the Vrancea source. The article will study a concrete structure which will be modelled using finite element software. The parameters and location of the story isolation system will be studied and optimized using genetic algorithms. The optimization will be applied in order to minimise displacements. The parameters which will be optimized will be the story where isolation system is equipped and its dimensions.
The testing program of the bridges before commissioning is mandatory for almost all the bridges. ... more The testing program of the bridges before commissioning is mandatory for almost all the bridges. Usually, for bridges with small spans and a simple structural type, the testing program consists only from static loading tests. When special building technologies, materials or structural models are involved in the bridge building, the dynamic testing of the bridge is required, also. The overpass from the Câmpina city entrance consists of a main passage with two lanes and, at the ends, four access roads with one lane each. The overpass is divided in five sections, acting as independent structures. These are composed from steel piers with composite decks. Each composite deck is made from a main steel girder with cross steel girders and reinforced concrete slab. Taking into account the curved shape of the bridge and the special structural type of the bridge, it was required an extended dynamic testing program, for every section of the bridge. This paper presents the dynamic test condition...
The testing program of the bridges before commissioning is mandatory for almost all the bridges. ... more The testing program of the bridges before commissioning is mandatory for almost all the bridges. Usually, for bridges with small spans and a simple structural type, the testing program consists only from static loading tests. When special building technologies, materials or structural models are involved in the bridge building, the dynamic testing of the bridge is required, also. The overpass from the Câmpina city entrance consists of a main passage with two lanes and, at the ends, four access roads with one lane each. The overpass is divided in five sections, acting as independent structures. These are composed from steel piers with composite decks. Each composite deck is made from a main steel girder with cross steel girders and reinforced concrete slab. Taking into account the curved shape of the bridge and the special structural type of the bridge, it was required an extended dynamic testing program, for every section of the bridge. This paper presents the dynamic test condition...
In this paper, the dynamic response of an isolated structure supported by lead rubber bearings is... more In this paper, the dynamic response of an isolated structure supported by lead rubber bearings is studied. The isolated building is modeled using finite element software. Each bearing is modeled using its yield force, elastic stiffness and plastic stiffness. The main objective of the paper is to find the optimal parameters of the base isolation system using genetic algorithms in order to minimize the displacement of the building. In order to minimize the objective function an elitist non-dominated sorting genetic algorithm is employed. The study focuses on a 10 story concrete structure rehabilitated according to new design prescriptions. The optimal distribution is determined using nonlinear time history analysis and three earthquakes pertinent to the Vrancea source.
Dynamic testing of road bridges is vaguely national regulated. As result, the importance and the ... more Dynamic testing of road bridges is vaguely national regulated. As result, the importance and the necessity of static and dynamic tests is diminished by various factors, human, technic or economic ones. The standard which regulates the experimental testing of rail and road bridges in Romania is STAS 12504-86. For the dynamic testing case, the Romanian standard provides some information on how to ensure the dynamic loading of bridges, it enumerates some of the characteristics that can be pursued through testing, but without giving information on how to process experimental data. The present paper illustrates a dynamic test of a road bridge, located on the A2 highway crossing the Danube-Black Sea Channel. There are presented bearings about the testing conditions, the experimental test results and a comparison with the bridge design values. The experimental results are proximate to the dynamic characteristics established in the bridge design, test algorithm and experimental data process...
Wind load design of the ground-mounted photovoltaic (PV) power plants requires interpretation of ... more Wind load design of the ground-mounted photovoltaic (PV) power plants requires interpretation of the design code considering the particularities of these structures. The PV power plants consist on systems of several solar panels. Wind load pressure coefficient evaluation, by design code, for a single solar panel considered as a canopy roof, neglect the group effect and the air permeability of the system. On the other hand, the canopy roofs are structures with medium serviceability, but the PV power plants are structures with low serviceability. This paper discuss the difficulties of the wind load design for the PV power plants ground mounted in Romania and compares the Romanian, German, European and American wind design code specifications with the parameters provided by the wind tunnel test, for this type of structures. For Romanian wind load design an evolution of the 1990, 2004 and 2012 editions of the design codes specifications is also studied. Evaluation of the internal result...
In the last years BRB were used in existing structu res and in new ones as primary lateral force ... more In the last years BRB were used in existing structu res and in new ones as primary lateral force resist ing elements. Retrofit of existing buildings in seismic areas can be made by using buckling restrained bra ces (BRBs), because they have the ability to sustain la rge inelastic deformations without important loss o f strength. This study analyzes the possibility of using BRBs t o improve the seismic response of tall reinforced c oncrete buildings. Therefore dynamic nonlinear analysis was performed on two tall structures: first, one struc ture with reinforced concrete walls (that has been designed a ccording to the Romanian Seismic Design Code) and t hen he same structure with buckling restrained braces incl uded. Computation was made for three recorded accelerograms. The aim of the study was to highligh t the advantages and disadvantages of using BRBs to gether with reinforced concrete walls for improving the se ismic response of tall buildings. Parameters like n atural period, de...
This article presents a comparative study of the values of hydrodynamic pressure and their result... more This article presents a comparative study of the values of hydrodynamic pressure and their resultants occurred during the seismic action using P100-1/2013 technical rules and the relations defined in the papers:
This paper presents an analytical study which deals with the behavior of the circular plates in b... more This paper presents an analytical study which deals with the behavior of the circular plates in bending theory, considering the soil-structure interaction under Winkler's hypothesis. It was intended to illustrate the variation of internal forces and deformations according to the flexibility coefficient of plates considering three models: a fixed solid circular plate subjected to a uniformly distributed load, a fixed solid circular plate acted by a displacement applied on the exterior contour and a solid plate subjected to a temperature gradient. For this study the computation relations were written as a product between a dimensional and a non-dimensional factor, the last one indicating the variation of internal forces and deformations. For each type of action there are presented results obtained using the finite element method to illustrate the differences between this method and the analytical computation.
In current design practice, typical seismic design of bridges tends to use simplified approaches.... more In current design practice, typical seismic design of bridges tends to use simplified approaches. On the opposite side, the most advanced seismic analyses currently used in practice in all the fields of structural engineering are probably the ones used for the design of nuclear facilities, which include soil–structure interaction and motion incoherency effects. From that category, the most modern methodology is the probabilistic approach, which has been added to the new ASCE 4 standard. This type of state-of-the-art analysis is carried out in ACS SASSI software on a typical concrete bridge structure with deep foundations. A comparison of the results with the deterministic SSI approach and the typical Eurocode design from previous studies is presented at the end. Major differences in behavior are highlighted, which impact the overall safety of the structure.
... Considering critical sec-tions only at the column ends, the storey shear force may be calcula... more ... Considering critical sec-tions only at the column ends, the storey shear force may be calculated as ... Figures 6 and 7 show the time evolution of the roof displacement and base shear ... its oscillations are out of phase with the struc-ture oscillations during the earthquake excitation. ...
The paper presents selected results of an international project of the new research center in ear... more The paper presents selected results of an international project of the new research center in earthquake engineering entitled “Dan Ghiocel International Research Center” at Technical University of Civil Engineering, Bucharest, Romania. The paper investigates the seismic structure-soil-structure interaction effects (SSSI) in densely built urban areas for a 15 floor Multistory Building (MB), a Church Building (CB) and a Subway Station (SS) in the Bucharest city. A description of the SSI effects for each of the three standalone buildings is provided in a companion paper (Bogdan, Ghiocel and Cretu, 2014). Seismic input was defined by a set of three-directional spectrum compatible acceleration histories generated based on the Romanian seismic design spectrum for the Bucharest city area. The seismic SSI and SSSI analyses were performed using the state-of-the-art ACS SASSI software. Three SSSI layout scenarios were considered. The SSSI analyses were performed for both coherent (synchronous...
In this paper a functional model to estimate the inelastic displacement ratio as a function of th... more In this paper a functional model to estimate the inelastic displacement ratio as a function of the ductility factor is presented. The coefficients of the functional model are approximated using nonlinear regression. The used data is in the form of computed displacement for an inelastic single degree of freedom system with a fixed ductility factor. The inelastic seismic response spectra of constant ductility factors are used for generating data. A method for selecting ground-motions that have similar frequency content to that of the ones picked for the comparison is presented. The variability of the seismic response of nonlinear single degree of freedom systems with different hysteretic behavior is presented.
In the last years BRB were used in existing structures and in new ones as primary lateral force r... more In the last years BRB were used in existing structures and in new ones as primary lateral force resisting elements. Retrofit of existing buildings in seismic areas can be made by using buckling restrained braces (BRBs), because they have the ability to sustain large inelastic deformations without important loss of strength. This study analyzes the possibility of using BRBs to improve the seismic response of tall reinforced concrete buildings. Therefore dynamic nonlinear analysis was performed on two tall structures: first, one structure with reinforced concrete walls (that has been designed according to the Romanian Seismic Design Code) and then the same structure with buckling restrained braces included. Computation was made for three recorded accelerograms. The aim of the study was to highlight the advantages and disadvantages of using BRBs together with reinforced concrete walls for improving the seismic response of tall buildings. Parameters like natural period, deformations and stresses were carefully evaluated and then some comparatively studies were made in order to establish the efficiency of the buckling restrained braces.
The paper presents the results of a project of the new research center in earthquake engineering ... more The paper presents the results of a project of the new research center in earthquake engineering entitled "Dan Ghiocel International Research Center" at TUCEB, Romania. The paper investigates the seismic soil-structure interaction effects for different type of buildings, such as a multistory residential building, an old church and a metro subway station in the Bucharest city. The site soil profile corresponds to the INCERC site soil layering in Bucharest. This is a relatively soft and deep soil deposit. Two seismic inputs are considered: i) the 1977 Vrancea Earthquake acceleration records NS, EW and Vertical at the INCERC site and ii) a set of 3-directional spectrum compatible acceleration input histories simulated based on the Romanian seismic code design spectrum. The seismic SSI analysis was performed using the state-of-the-art ACS SASSI software (Ghiocel, 2013). The Flexible Volume (FV) substructuring method was used to perform accurate SSI analyses.
The paper presents selected results of an international project of the new research center in ear... more The paper presents selected results of an international project of the new research center in earthquake engineering entitled "Dan Ghiocel International Research Center" at Technical University of Civil Engineering, Bucharest, Romania. The paper investigates the seismic structure-soil-structure interaction effects (SSSI) in densely built urban areas for a 15 floor Multistory Building (MB), a Church Building (CB) and a Subway Station (SS) in the Bucharest city. A description of the SSI effects for each of the three standalone buildings is provided in a companion paper (Bogdan, Ghiocel and Cretu, 2014). Seismic input was defined by a set of three-directional spectrum compatible acceleration histories generated based on the Romanian seismic design spectrum for the Bucharest city area. The seismic SSI and SSSI analyses were performed using the state-of-the-art ACS SASSI software. Three SSSI layout scenarios were considered. The SSSI analyses were performed for both coherent (s...
The paper studies the influence of an optimal inter-storey isolation system on seismic behaviour ... more The paper studies the influence of an optimal inter-storey isolation system on seismic behaviour of a concrete structure. The inter-storey isolation system uses lead rubber bearings at a certain level of the structure. The structure will be subjected to a series of pulse like earthquakes in order to account for the variability of the hazard of the Vrancea source. The article will study a concrete structure which will be modelled using finite element software. The parameters and location of the story isolation system will be studied and optimized using genetic algorithms. The optimization will be applied in order to minimise displacements. The parameters which will be optimized will be the story where isolation system is equipped and its dimensions.
The testing program of the bridges before commissioning is mandatory for almost all the bridges. ... more The testing program of the bridges before commissioning is mandatory for almost all the bridges. Usually, for bridges with small spans and a simple structural type, the testing program consists only from static loading tests. When special building technologies, materials or structural models are involved in the bridge building, the dynamic testing of the bridge is required, also. The overpass from the Câmpina city entrance consists of a main passage with two lanes and, at the ends, four access roads with one lane each. The overpass is divided in five sections, acting as independent structures. These are composed from steel piers with composite decks. Each composite deck is made from a main steel girder with cross steel girders and reinforced concrete slab. Taking into account the curved shape of the bridge and the special structural type of the bridge, it was required an extended dynamic testing program, for every section of the bridge. This paper presents the dynamic test condition...
The testing program of the bridges before commissioning is mandatory for almost all the bridges. ... more The testing program of the bridges before commissioning is mandatory for almost all the bridges. Usually, for bridges with small spans and a simple structural type, the testing program consists only from static loading tests. When special building technologies, materials or structural models are involved in the bridge building, the dynamic testing of the bridge is required, also. The overpass from the Câmpina city entrance consists of a main passage with two lanes and, at the ends, four access roads with one lane each. The overpass is divided in five sections, acting as independent structures. These are composed from steel piers with composite decks. Each composite deck is made from a main steel girder with cross steel girders and reinforced concrete slab. Taking into account the curved shape of the bridge and the special structural type of the bridge, it was required an extended dynamic testing program, for every section of the bridge. This paper presents the dynamic test condition...
In this paper, the dynamic response of an isolated structure supported by lead rubber bearings is... more In this paper, the dynamic response of an isolated structure supported by lead rubber bearings is studied. The isolated building is modeled using finite element software. Each bearing is modeled using its yield force, elastic stiffness and plastic stiffness. The main objective of the paper is to find the optimal parameters of the base isolation system using genetic algorithms in order to minimize the displacement of the building. In order to minimize the objective function an elitist non-dominated sorting genetic algorithm is employed. The study focuses on a 10 story concrete structure rehabilitated according to new design prescriptions. The optimal distribution is determined using nonlinear time history analysis and three earthquakes pertinent to the Vrancea source.
Dynamic testing of road bridges is vaguely national regulated. As result, the importance and the ... more Dynamic testing of road bridges is vaguely national regulated. As result, the importance and the necessity of static and dynamic tests is diminished by various factors, human, technic or economic ones. The standard which regulates the experimental testing of rail and road bridges in Romania is STAS 12504-86. For the dynamic testing case, the Romanian standard provides some information on how to ensure the dynamic loading of bridges, it enumerates some of the characteristics that can be pursued through testing, but without giving information on how to process experimental data. The present paper illustrates a dynamic test of a road bridge, located on the A2 highway crossing the Danube-Black Sea Channel. There are presented bearings about the testing conditions, the experimental test results and a comparison with the bridge design values. The experimental results are proximate to the dynamic characteristics established in the bridge design, test algorithm and experimental data process...
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Papers by Dan Cretu