Papers by Keyword: RC Structure

Abstract: The high-rise buildings in built-up areas affect the surrounding pedestrian-level wind environment. Unpleasant gust strong wind especially between the buildings, on corners, the crossing points and passages, will experience these locations as not comfortable or dangerous. The series of parametric wind tunnel studies were carried out to investigate the effects of building width, height and the gap width between buildings on the pedestrian-level wind environment. In the article, we will discuss build up area around designed reinforced concrete structure with atypical shape - TWIN CITY A1 Bratislava (developer company: HB Reavis). We indicated the high wind speed areas for discomfort under strong wind conditions experimentally in BLWT wind tunnel and using CFD simulation. It is important to note that the wind effects applied on the reinforced-concrete structures and occurring around these structures are one of the most important input parameters in their design. Therefore, they should not be neglected. As it was mentioned above, this paper deals only with the wind effects occurring around the examined structure. The wind effects applied on the structure – determination of the external wind pressure coefficients, were discussed in [1].

Abstract: Adding braces to moment frames is considered to be quite an efficient technique for increasing the global stiffness and strength of the structure. It has not only been used in steel moment frames, but also in reinforced concrete (RC) moment frames in recent years. It certainly can increase the energy absorption capacity of structures and also decrease the demand imposed by seismic ground motions. Steel braces are anchored firmly to boundary beams and columns. They are modeled as truss elements and increase earthquake resistance of the building. Buckling restrained braced frames (BRBFs) in which members yield under both tension and compression without significant buckling have been used in recent years in order to ensure the desired seismic performance of special concentrically braced frames. BRBFs are similar to the special concentrically braced frames in that seismic accelerations are resisted by a building-frame members and diagonal braces whereas the design procedure is different. BRBs should be designed to permit ductile yielding both in compression and tension. In this paper, flat-slab RC building with two different configurations of buckling restraint braces (BRBs) is studied. The buildings have 4-storey with 5 bays in both X-and Y-directions and have been designed according to Turkish Specification of Reinforced Concrete Design (TS 500). In order to explore overall behavior up to failure and lateral load resisting capacities for these buildings, nonlinear static analyses have then been performed using SAP 2000-V14.1. Pushover analysis under constant gravity loads and monotonically increasing lateral forces during an earthquake until a target displacement is reached is generally carried out as an effective tool for performance based design. The major outcome of a pushover analysis is the capacity curve which shows the base shear vs. the roof displacement relationship and represents the overall performance of the building. The results of the analyses are presented in terms of capacity curve and energy dissipation.

Abstract: In this paper authors present analysis of limits when formulas for limiting the span/depth ratio, given in EN1992-1-1 section 7.4.2, for different reinforced concrete members subjected to bending, are applicable. Recommendations about how to take the compression reinforcement in calculations into account, when deflection of bending members should be assessed, are also proposed.

Abstract: After steel structure was added on top of a concrete frame structure, the mass, stiffness, natural period and damping ratio of the original frame structure has changed significantly. Using finite element software ANSYS and software PKPM respectively, model of the original frame structure and the new structure with story-adding steel structure were built. Furthermore, seismic performance of the three structures was studied. Weak location of the structure was found out. Finally, the main factors were analyzed. Results show that whiplash effect is not obvious when one-story steel structure was added on the top of the original frame structure. Also, seismic performance of the frame structure with two-story steel structures on the top is perfect. Some suggestions are put forward for designing the similar structure.

Abstract: Almost all high-rise buildings have been constructed in the Republic of Armenia for past twenty-five years are Reinforced Concrete (RC) shear wall–frame structures, where shear walls provide most of the stiffness of buildings. The walls in these buildings are designed to sustain earthquake and wind loads. Vulnerability of them during earthquake action depends on many different factors. Some of them are the openings and its location in the walls. Usage of ground stories as parking and garages is demanded large openings in shear walls therefore determination of ultimate sizes of openings is important problems for designers. In this paper, FEM (Finite Element Method) models are used for investigation of stress-strain state of RC wall–frame buildings with various openings in the walls under action of seismic forces. Limitation of size and position of openings are considered in the paper taking into account of building code of Armenia. Various schemes of openings are considered in the article. The existing experimental data of shear walls were performed in various laboratories have been compared with our numerical investigation of RC models based on nonlinear computer analyses. Dynamic analyses of structures using accelerograms are showed sequence of damages in RC wall-frame models. The recommendations for limitation of ratio area of an opening to the whole area of a wall are proposed at the end of the article.

Abstract: This is a report on the performance of 4 types of cool roof system through field tests. Cool roof means solar protection on roof surface [1]. The tested systems were solar cells as a shading device, several types of thermal insulation paint as heat reflectors, a rooftop garden as an outside thermal insulator on a roof and a water pond on a roof as a coolant with sensible heat and evaporation. The test results indicated obvious temperature difference between the cool roof and the ordinary surface. The heat flux was calculated from the results to estimate the cooling load saving. Finally, these results were examined from the viewpoint of cost performance.

Abstract: In the paper, the improved coupling convection and diffusion model of chloride ion penetration in reinforced concrete (RC) structures under corrosive environments is presented, in which many major influence factors such as environmental temperature and relative humidity, water ratio of concrete, and stress state etc are considered. Based on Fourth-Moment stochastic simulation theory, the estimation of the depassivation probability of reinforcement in corrosive RC is analyzed. And many important conclusions on depassivation of reinforcement is gained, which will be useful for repair, rehabilitation, and replacement of RC structures in corrosive environments.

Abstract: Restoring force model is a simplified mathematical model derived from restoring force-deformation curves in lots of tests. Selecting a reasonable restoring force model is the basis of conducting dynamic nonlinear analysis of structure. The work further investigates the advantage and disadvantage of the restoring force models presented in this paper. Classified and brief comments about the existing drawbacks of restoring force models and its application are conducted. Lastly, some useful suggestions are proposed for the further research.

Abstract: This study investigates a displacement-based procedure for the seismic assessment and retrofitting of a six-storey RC structure, designed for gravity loads without specific earthquake-resistant provisions. The procedure is based on a simplified approach using nonlinear static pushover analyses and allows to compare alternative retrofitting strategies countering different structural deficiencies. Accurate numerical models were developed in order to provide reliable predictions of the behaviour of the building identifying the main structural deficiencies. Two retrofitting solutions based on alternative strategies were proposed for the RC structure. The introduction of concentric steel bracings decreased the displacement demand on the structure, thus reducing damage in structural members. A more uniform distribution of storey drift was observed throughout the height of the building. The application of FRP wrapping increased the deformation capacity of the columns and significantly enhanced the global ductility of the structure, without modifying the displacement demand. The validity of the simplified procedure and the effectiveness of the retrofitting interventions were assessed by nonlinear dynamic analyses.

Abstract: A pseudolinear equivalent method is proposed to analyze the nonlinear deformation of reinforced concrete structure member. In this method, the real moment of a bending member is transformed into equivalent moment by means of acquiring the bending moment-curvature relation of the section, and then the equivalent concentrated forces along the member are gained through the differential relationship between bending moment, shear force and distributed force. By this method, the problem of nonlinear system can be transformed into the problem of linear system. This method can analyze the deformation of RC structure members with constant or variant sections, which can be extended to analyze the nonlinear deformation of the structure members made of other kinds of engineering materials. The analyzed result given by this method fits the result attained from finite element method very well, which proves the feasibility of the model.