Effect of Column to Beam Strength Ratio on Performance of Reinforced Concrete Frames (original) (raw)
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Behavior and ductility of high strength reinforced concrete frames
HBRC Journal, 2014
This paper presents an experimental study for the behavior and ductility of H.S.R.C frames. The experimental program was conducted on five specimens (frames). F1 is a control specimen consisting of beam with cross section 12 · 20 cm and length 1.85 m and two columns with cross section 12 · 20 cm and height 1.5 m. In the second specimen (F2) the depth of beam is changed from 20 cm to 30 cm but in the third specimen (F3) the dimensions of columns are changed to 12 · 30 cm while in the fourth specimen (F4) the aspect ratio h/L (height to length of panel) of frame is changed from 0.81 to 0.625. The fifth specimen (F5) has different details of connections between columns and beam. The stirrups are arranged in half spacing distance at connection with respect to the regular distance of all columns and beams. The dimension of frames is selected to represent half scale frames and tested under cyclic loading. All specimens of the experimental program are tested in the reinforced concrete testing laboratory at Housing and Building National Research Center in Cairo.
Experimental research activities and post-earthquake considerations have demonstrated that reinforced concrete columns with light or widely spaced transverse reinforcement are vulnerable to shear failure during earthquakes. According to this point by using failure limit curve, we can assess the effective parameters in shear and axial failure of reinforced concrete columns in framed buildings. In the current study by flexural, shear and axial springs which are used in series, shear and axial failures and important effective parameters have been assessed, Besides 5,10 and 15 story models with different amounts of initial axial load ratio have been analyzed by nonlinear pushover analysis. The results of analytical models contain behavior of buildings based on different initial axial load ratio and different spacing of transverse reinforcement are compared
The aim of this study is to investigate the behavior of low-rise, four-story RC framed structures when subjected to abnormal loads, specifically missing column scenarios. The study uses more than 20 unique models with varying beam and column cross sections and designs them for India's four seismic zones (Z2, Z3, Z4, and Z5) in accordance with IS 456–2000 and IS 1893–2016 using FEM based ETABS V.17 Software. The study evaluates the potential for progressive collapse of structures in all three possible cases of column removal, as per the GSA (2016) Guidelines, using the linear static analysis approach. The investigation aims to determine the progressive collapse potential of low-rise reinforced concrete framed structures designed for Indian seismic zones, and the effect of different beam and column cross sections on the structures' progressive collapse potential. The study finds that structures designed for high seismic zones (seismic zone 5 with high beam column cross section...
In high-rise buildings and heavy loaded structures where RC columns are subjected to heavy loads, the use of High Strength Concrete (HSC) in columns construction is essential for the purpose of reducing column size and increasing column capacity. However, from the economical standpoint, combination of high and normal strength concrete (NSC) in building construction is becoming common practice, where HSC is used for columns and NSC is used for the surrounding beams/slabs floor system. This creates a situation where concrete strength of the column portion at the beam/slab floor level is lower than concrete strength used for rest of the column. Previous studies indicated that such variation in concrete strength affects the load carrying capacity of the RC columns. This paper presents a theoretical study on the effect of using concrete with different strengths for columns and floor beams on the structural behavior of integrated RC building frames under static, lateral pushover and earthquake loading cases. Four-story frame was analyzed employing a ready package program for the inelastic structural analysis of buildings (IDARC-5). The obtained results indicated that under static loading, variation in the concrete strength of the transition zone has a negligible effect on the behavior of the studied frame. However, under lateral pushover and earthquake loading the behavior of the studied frame is influenced by the ratio of column concrete strength to the transition zone concrete strength. For a ratio of 1.4 or less, no real influence was noted. On exceeding this ratio, the frame response was adversely influenced. This agrees with the recommendations of the ACI 318 Building Code.
Effects of High-Strength Concrete on Progressive Collapse Resistance of Reinforced Concrete Frame
Journal of Structural Engineering, 2020
The application of extreme loads such as impact and blast may lead to progressive collapse and the robustness of a structure must be considered in this context. Although extensive studies had been carried out over the past decades to study the load resisting mechanism of reinforced concrete (RC) frames to prevent progressive collapse, the effects of high-strength-concrete (HSC) on progressive collapse resistance capacity is still unclear. Therefore, six tests of RC frames with different span-todepth ratio and concrete strength were conducted in present study. Among them, three are HSC frames and the remaining are normal strength concrete frames. It was found that the use of HSC could further enhance the compressive arch action (CAA) capacity, especially for those with low span-to-depth ratio. On the other hand, HSC can reduce the tensile catenary action (TCA) capacity at large deformation stage, primarily because of higher bond stress between concrete and rebar, leading to earlier fracture of the rebar. The analytical results from the model were compared with the test results. It was found that the refined CAA model could accurately predict the CAA capacity of NSC frames, but not for HSC frames. Moreover, existing model is hard to predict the CAA capacity of the frames with relatively small span-to-depth ratio (less than 7) accurately.
EFFECT OF USING HIGH STRENGTH CONCRETE COLUMNS ON THE STRUCTURAL BEHAVIOUR OF R.C BUILDINGS.
Strength, durability and stability are the main criteria for material selection and design in the construction industry. Consequently, development and enhancement of construction materials is always an active and attractive field for engineers and researchers. Elevated temperature (fire) is a potential threat for any structural buildings that can cause a major damage. Response of construction materials exposed to elevated temperature or fire requires a full study and analysis with lessons learned from previous cases. High strength concrete (HSC) has been used in the lower story columns of high rise buildings owing to its qualities over normal strength concrete (NSC) in many countries. But, the full structural qualities of the HSC were unable to be used because of insufficient information regarding the structural behaviour of the material and its properties. Columns moment-curvature curves were developed and maximum inter story drifts were obtained for the different frame models with variation in columns concrete strength. The study shows that frames with HSC columns have got lower stiffness and performed well in satisfying ductility demand. The maximum inter storey drifts are slightly higher for frames with HSC columns, but the contribution of the concrete strength in resisting the lateral deformations was significant. Economic comparisons were also made and it was found that the most economical frame corresponds to frame with the highest columns concrete strength.
Progressive Collapse of Reinforced Concrete Frame Structure under Column Damage Consideration
Pakistan Journal of Engineering and Applied Sciences, 2015
The research work is focused on progressive collapse analysis of reinforced concrete framed structure under column damage consideration using commercial software SAP2000. Nine story frame is selected and designed under gravity loads as per Pakistan Building Code. The frame is analyzed for progressive collapse under three damage cases; corner column damage, edge column damage and internal column damage. The frame is subjected to loading as described by General Services Administration (GSA) guideline for carrying out linear static analysis. The results include the variation of bending moment of beams and evaluation of demand capacity ratios(DCR) in the beams of the longer direction. The vertical deflections of the damaged joint are determined in cases with 0%, 40%, 60%, 80% and full damaged consideration. According to the GSA guideline atypical frame building having DCR values greater than 1.5 indicate more damage potential in the structural members. It is concluded that the edge column case with long bays is found critical because the bays with longer span have more damage as compared with smaller span bays. It can lead collapse of the frame in short interval of time and there is more possibility of loss of lives under such condition of structures. Based on this research it is suggested that the practicing engineer should incorporate the GSA guidelines for loading along with the other loads so that progressive collapse potential may be reduced up to some extent.
In the limit state of collapse design approach for reinforced concrete (RC) columns, the conceptual design criteria is formulated based on the balanced limiting strains i.e. simultaneous crushing of concrete and yielding of steel occurs in extreme concrete fiber and steel, which is designated as 0.0035 and 0.002+(f y +1.15/E s) respectively. But the tensile strain in extreme layer of steel is permitted to reach any value more than the prescribed value under crucial scenarios of high seismic influence. Therefore the premature yielding of extreme steel layer over the crushing of concrete, i.e. the under reinforced design of RC columns is not authentified by the existing design approach. Adding to this whenever RC columns are subjected to seismic forces, reversal of stresses occurs i.e. the predominant compressive forces in column changes its behavior to tensile forces. Hence it is mandatory to determine the tensile capacity of column and its corresponding ductile behavior and the strain energy stored in it. The tensile capacity of the column and the range of tension failure under combined compressive axial load and bending is thus identified by determining the Balanced Axial load factor λ ,in which the computation involves the limiting strain states in concrete and steel. A numerical study is made over the Balanced Axial Load factor λ by, varying parameters such as Column section, Percentage of reinforcement excessive limiting strains in steel and with the orientation of the column. Hence a more accepted under reinforced design approach i.e. ductile design is proposed for columns subjected to seismic forces. Analysis of Tensile Capacity of Reinforced Concrete Columns and its Ductility Performance towards Seismic Behavior
Effect of using High Strength Concrete Columns on the Structural Behaviors of Building Frame
2014
High strength concrete (HSC) has been used in the lower story columns of high rise buildings owing to its qualities over normal strength concrete (NSC) in many countries. But, the full structural qualities of the HSC were unable to be used because of insufficient information regarding the structural behavior of the material and its properties were not adequately addressed in building codes including EBCS. Analytical study was conducted at structure level to investigate the effect of using HSC column on the structural behavior of regular models of medium to high rise frame buildings under seismic lateral load in addition to gravity loads. Concrete strength variations of C30 to C90MPa were applied on the columns of the frame models. The proposed properties of the HSC class were incorporated in the analysis and design of the columns. The frames analysis was done using ETABS and columns were designed based on the EBCS column design procedure.
Pushover Analysis of Partially Strengthened Column Structures on an Existing Multi-story Building
MATEC Web of Conferences, 2019
A pushover analysis was conducted to evaluate structuralperformance of an extended building structure subjected to simulatedseismic loads. The Inna Garuda Hotel was selected as a building object ofthis research focusing on the extension building only. This 7-storyreinforced concrete building has been functioned as a hotel building in theYogyakarta City of Indonesia for over 30 years. Preliminary results of thisanalysis indicated that the performance level of this building wascategorized as an immediate occupancy (IO), however, the plastic hingeson the slim column structure components occurred. Given this condition, the structure of the building does not fulfill the concept of a strong columnweakbeam (SCWB). The research objective is to follow up on thepotential of building collapse due to the column structure weakness byconducting a research on the strengthening of slim column elements. Apushover analysis was carried out using ETABS software. A strengtheningtechnique was adopted by ...