Viorel Popa

Experimental testing on emulative connections for precast columns using grouted corrugated steel sleeves

Seismic analysis of precast concrete structures requires specific information regarding the behaviour of the connections under large deformation cycles. If a connection is located within the critical region of a structural element, its energy dissipation capacity needs to be confirmed by experimental testing. The use of emulative connections for precast elements is attractive for designers because common conventional design methodologies and assumptions developed for cast in place structures may be readily used. The results of a structural testing program for precast columns connected using grouted corrugated steel sleeves are reported in this paper. A comparison with reference “cast in place” specimens is made and conclusions regarding the emulative characteristic of the connection are drawn. Tests were carried out on scaled concrete columns using the reaction frame at the Technical University of Civil Engineering of Bucharest. Four precast specimens and two reference specimens were tested. Analysis of the recorded data showed that the precast specimens have similar hysteretic response and energy dissipation capacity as the reference ones.

Impact of Long-Period Ground Motions on Structural Design: A Case Study for Bucharest, Romania

In this chapter, the soil conditions in the Bucharest area are evaluated using several approaches based on both observed and simulated ground motion recordings. The analysis of the recorded ground motions shows the fact that significant long-period spectral ordinates are encountered for large magnitude Vrancea intermediate-depth seismic events. A soil class C according to EN 1998-1/2004 can be assigned for Bucharest based on the shear-wave velocities of the existing boreholes in this area. However, the much deeper Quaternary sediments from the Bucharest area can generate significant long-period spectral ordinates largely exceeding the ones for a typical soil class C site. The nonlinear ground response analysis performed for INCERC site in the eastern part of Bucharest revealed ground motions with a frequency content similar to the one of the ground motion recorded during the Vrancea 1977 earthquake. Besides the peak in amplitude corresponding to a spectral period of around 1.5 s, some additional analyses have shown that another peak at around 5 s can be inferred from the available data.

Update of the P100-1 Concrete Provisions

Abstract In an effort to improve the harmonization of the Romanian design codes with the Eurocodes, the revision of the Seismic Design Code, P100-1, started in April 2010 and ended in September 2013. The main issues addressed during the revision process are presented in this paper. They include re-outlining the fundamental requirements for seismic design, revision of the seismic action, improvement of the specific provisions for the design of reinforced concrete, steel, composite, wood and masonry structures and non-structural components. This paper focuses on the specific provisions for reinforced concrete structures but general information about the fundamental requirements and the seismic action are presented as well.

Effective stiffness and displacement capacity of short reinforced concrete columns with low concrete quality

Hysteretic behaviour of reinforced concrete members is strongly dependent on local conditions such as quality of materials, workmanship, construction and design practice. Low strength concrete was found in most of the damaged concrete structures after the earthquakes that have hit Eastern Europe in the past 50 years. Quality of concrete had a great impact, especially on shear controlled reinforced concrete short columns. Existing models of the effective strength, stiffness and deformation capacity of structural members need to be confirmed locally by experimental research as the large data sets used to calibrate the analytical models comprise results obtained on specimens with various characteristics. In this study, effective stiffness and deformation models available in literature are compared with the results of an experimental testing program conducted by the authors to investigate the hysteretic response of reinforced concrete short columns with low concrete strength, designed and detailed according to the local practice in the past. The hysteretic behaviour of the specimens is presented together with a comparison of the experimental data with predicted values and conclusions on the suitability of the applied models are drawn.

In Plane Cyclic Behavior of Masonry Walls Jacketed with Fiber Reinforced Mortar and Fiber Grids

Abstract Masonry buildings represent the most vulnerable part of the building stock to seismic action in Romania. The main goal of this experimental research program is to investigate the efficiency of several retrofitting solutions using fiber reinforced polymers. Research focused on the lateral strength and displacement capacity of the retrofitted specimens. The masonry walls were built using solid bricks. Glass or carbon fiber reinforced polymers (GFRP or CFRP) embedded in a fiber reinforced mortar layer were used for jacketing. Seven specimens having essentially 25cm width, 1,75m height and 2,10m length were tested in the experimental research program. These specimens were subjected to a constant vertical compressive stress of 1,2MPa. A quasi-static load protocol was considered for the horizontal loading. This paper presents the layout of the experimental research program and some preliminary results.

Seismic Risk Assessment of Romania

This paper summarizes the UTCB results for the “National Risk Assessment—RO RISK” project. Within the RO-RISK project, coordinated by the General Inspectorate for Emergency Situations, the first nation-wide assessment of all types of natural risks was performed in 2016. The work was supported by collaboration of disaster reduction experts and earthquake risk modelling specialists from INFP and URBAN-INCERC. The seismic risk assessment was performed for the entire country, at the most detailed resolution available, which is the administrative-territorial unit. For each building typology, four limit states were considered in order to generate fragility curves. Each limit state is associated with a loss percentage, in order to generate vulnerability curves. The assessment shows that among the 10 analysed hazards, the seismic hazard produces the largest impact at country level, 75% of the population and 45% of the vital networks are exposed to moderate and high earthquake risk and Romania’s capital Bucharest, is highly exposed to earthquakes.

Design of Beam Anchorages in Beam-Column Joints in Seismic Structures

Proper anchorage of beam reinforcement in beam-column joints is necessary for a stable hysteretic behavior of seismically loaded structures subjected to large lateral displacements. Anchorage requirements associated with the use of higher strength steel such as S500 generated the need to increase the anchorage lengths and concrete strengths. Formerly used concrete strength classes such as C20/25 and C25/30 are largely replaced with higher quality concrete such as C40/50 or more. In common design practice, anchorage provisions of the repealed Romanian standard STAS 10107/0-90 are still informally used. This might lead to poor anchorage details and related structural problems. This paper draws attention on the specifications of the current standards for anchorage of beam reinforcement. Practical design rules are presented as well.

Structural Design for Large Displacement Demands in Romania

In this section, some aspects regarding the structural design and detailing of reinforced concrete buildings in Bucharest are discussed. The evaluation of the spectral shapes used in the design of buildings is discussed, as well. A new relation for the evaluation of the amplification factor for spectral displacements is proposed based on recent results obtained using ground motions recorded during intermediate-depth Vrancea earthquakes. Examples of the main structural systems used for common building in Bucharest are given. The issue of designing structural systems for relatively high levels of lateral force coupled with large displacement demands is also discussed in depth. As a general observation, the shear wall density for buildings in Bucharest is almost twice as large as that of Chilean buildings. An illustrative example for the structural design of a medium-rise reinforced concrete building in Bucharest is given and the main issues regarding the structural detailing are highlighted.

Seismic Hazard Assessment for Bucharest

In this section, a ground motion model is derived specifically for the Bucharest area using a dataset consisting of both recorded and simulated ground motions from Vrancea intermediate-depth earthquakes. The proposed ground motion model is able to capture the significant long-period spectral ordinates generated by the large magnitude Vrancea intermediate-depth earthquakes occurring at short source-to-site distances. In addition, the spectral accelerations derived from the proposed model have frequency contents similar to the recorded ground motions. The probabilistic seismic hazard assessment performed using the previously mentioned ground motion model shows a plateau of constant spectral accelerations up to around 2.0 s, while the corresponding spectral displacements can reach up to 100 cm for periods of 4.0 s. The analyses also reveal that only the larger magnitude earthquakes occurring at short source-to-site distances can generate spectral ordinates exceeding the ones proposed by the current Romanian seismic design code and this situation is valid mainly for long-period structures.

Evaluation of Soil Conditions in Bucharest

In this chapter, the soil conditions in the Bucharest area are evaluated using several approaches based on both observed and simulated ground motion recordings. The analysis of the recorded ground motions shows the fact that significant long-period spectral ordinates are encountered for large magnitude Vrancea intermediate-depth seismic events. A soil class C according to EN 1998-1/2004 can be assigned for Bucharest based on the shear-wave velocities of the existing boreholes in this area. However, the much deeper Quaternary sediments from the Bucharest area can generate significant long-period spectral ordinates largely exceeding the ones for a typical soil class C site. The nonlinear ground response analysis performed for INCERC site in the eastern part of Bucharest revealed ground motions with a frequency content similar to the one of the ground motion recorded during the Vrancea 1977 earthquake. Besides the peak in amplitude corresponding to a spectral period of around 1.5 s, some additional analyses have shown that another peak at around 5 s can be inferred from the available data.