Steel Reinforced Concrete Frame Structures Research Articles

Importance Analysis of Structural Seismic Demand Based on Support Vector Machine

Seismic demand analysis of structures plays an important role in the structural seismic calculation; however, studies on the importance analysis of seismic demand are limited. A new method based on a support vector machine (SVM) is proposed to analyze the importance of structural seismic demand and study the influence of random variables on structural seismic demand in this study, where the linear kernel function, Gauss kernel function, and polynomial kernel function are used in SVM. The time history analysis of the steel-reinforced concrete (SRC) frame structures has been carried out by the finite element software OpenSees under the action of different seismic records. Four kinds of seismic demand of the SRC frame structure are analyzed in this study, which are top displacement, maximum floor acceleration, base shear, and maximum interstory drift angle, respectively. Importance indexes of the four kinds of structural seismic demand are in good agreement with those of the Monte Carlo (MC) numerical simulation method and Tornado graphic method, which verify the accuracy of the proposed method. Moreover, the sample size of the proposed method is greatly smaller than that of the MC method. Therefore, the computation efficiency has been improved significantly by the proposed method.

Damage Index Based Seismic Failure Verification Method for SRC Frame Structures

A calculation method for structural total damage by combining two damage components from two directions that are vertical to each other is proposed. Based on the damage index, a new seismic failure checking method for steel reinforced concrete (SRC) frame structures is proposed. In this method, damage limits are corresponding to 3 design requirements of Chinese codes, and this damage based method aims at failure status checking of SRC frame structures. 4 levels of earthquakes (3 of which are 0.5 intensity higher than a frequent earthquake, seismic precautionary intensity, and rarely earthquake in Chinese codes, another one is 1.5 intensity higher than rare earthquake) were applied on a 20-stories SRC frame. Compared failure statuses checking results by using drift based method (which is introduced by Chinese codes) and the new damage based method, some difference between results which are checked by Chinese codes' method and this damage based method respectively can be observed, and reasons for these difference are: negative effects which caused by cycle loads with same maximum deformations is ignored by Chinese codes' method but it is considered by damage based method, and the difference between deformation ability of each story is ignored by Chinese codes' method but it is considered by damage based method.

The Moment-Independent Importance Analysis of Structural Seismic Requirements Based on Orthogonal Polynomial Estimation

The structural damping ratio, structural quality, yield strength, and elastic modulus of section steel, compressive strength, elastic modulus of concrete, yield strength, and elastic modulus of steel bars play important roles in the stability of the steel-reinforced concrete (SRC) frame structure, which are usually uncertain. However, their importance influence on the different seismic demands of SRC is rarely investigated simultaneously. In order to investigate the effects of the above parameters on four seismic demands (i.e., the top displacement, the maximum floor acceleration, the base shear force, and the maximum interstory displacement angle) of SRC frame structures, the orthogonal polynomial estimation method is first applied to the importance analysis of structural seismic demand based on the moment-independent method. Two engineering examples are performed to verify the accuracy and efficiency of the proposed method. The results have the characteristics of fast convergence and are in good agreement with those obtained by the moment-independent method based on kernel density estimation. The variance importance index based on Monte Carlo (MC) method is also calculated for comparison. The influence of each random variable on the four structural seismic demands is basically the same. Therefore, the accuracy and efficiency of the proposed method are proved sufficiently.

Experimental research on seismic damage of a full-web SRC frame structure

An experiment was conducted to investigate the seismic damage of a full-web steel-reinforced concrete (SRC) frame structure. A 1/3 scale, 2-bay, 3-story model of the full-web SRC frame was designed and constructed, and the load-displacement hysteretic curve, stiffness and strength degradation, displacement ductility, energy dissipation, crack propagation, failure mechanism, damage parameter, and evolution of seismic damage were investigated under low-reversed cyclic lateral loading. Based on an existing seismic damage model, the damage index was calculated and cumulative damage of the frame model was determined. The experimental results showed that the damage process of the full-web SRC frame structure consisted of four stages - namely, the undamaged stage, initial damage stage, stable development stage, the rapid development stage. Frame beams were damaged first, followed by damage to frame columns; Frame beams experienced the greatest damage. The damage value was largest for the first floor of the structure. Damage values calculated with the two methods were similar and accurately reflected the evolution of seismic damage. The research results can provide a theoretical basis for post-earthquake damage assessment of a full-web SRC frame structure.

Seismic fragility analysis of steel reinforced concrete frame structures based on different engineering demand parameters

Nowadays, performance-based seismic design is the focus of earthquake engineering research, in which the seismic performance of a structure is mainly evaluated based on seismic fragility. However, the role of Engineering Demand Parameters (EDPs) on the seismic fragility analysis of Steel Reinforced Concrete (SRC) frame structures remains unclear. This paper presents results on the effects of EDPs on the seismic behavior of a plan-asymmetric SRC building. For this purpose, a nonlinear finite element model of the SRC frame structure was numerically developed using the OpenSees software. This finite element model was then validated using experimental results. The peak interstory drift ratios, as well as the component-based and material-based damage indices, were accordingly employed as EDPs. This study additionally shows seismic fragility curves for an SRC frame structure. The achieved results for the mentioned EDPs were both compared and analyzed. The findings indicated that the EDPs play a role in the seismic fragility analysis for the SRC frame structures. The fragility curves based on a damage index could display the probability of exceeding the ultimate limit states subjected to different seismic intensities, and also showed a similar manner with those based on peak interstory drift ratios. It can be concluded that for an SRC frame structure, the results of seismic fragility analysis using the component-based damage index proved to be more cost-effective and reliable.

Mechanical behavior of lattice steel reinforced concrete inner frame with irregular section columns under cyclic reversed loading

A 1/2.5-scaled model of two-bay and three-story inner frames, which consisted of reinforced concrete beams and lattice steel reinforced concrete (SRC) irregular section columns, was constructed and tested under low cyclic reversed loading. Elasto-plastic features, integral and inter-story lateral stiffness degradation and the loading capacity of the structure were analyzed. Test results indicate that the lattice SRC inner frame has uniform lateral stiffness and the stiffness degradation process tends to be moderate. The relationship between story drift and the ratio of story stiffness degradation were obtained. The strength degradation appears to increase with the increment of displacement, but the effect is not obvious under the three cycles of each displacement level. The method of forming plastic hinge at the bottom of column is applicable for the calculation of story shear bearing capacity corresponding to the plastic moment of lattice SRC frame with irregular section columns. The elasto-plastic behaviors of the frame in positive and negative directions are similar. The ultimate elasto-plastic story drift rotation is larger than the limit value specified by the Chinese Code for The Seismic Design of Buildings (GB50011-2010), indicating that the capacity of collapse resistance of lattice SRC frame is higher. Compared with the reinforced concrete frame with irregular section columns, the ductility and energy dissipation capacity of lattice SRC frame structure are much better. The failure mechanism of the frame is the beam-hinged mechanism, which satisfies the seismic design principle of strong column and weak beam.

The Steel Reinforced Concrete Structure in Main Plant for Heat Supply

As one of the forms of composite structure system,the steel reinforced concrete(SRC) frame structure has the advantages of high carrying capacity and excellent elastic - plastic.The SRC has been widely used in high-rise structures and bridges. Meanwhile, it has promising application prospects in industrial plant construction. However, there are not many researches on the entity SRC structure in China at present, and many issues need to be explored. In this paper, we will give suggestions of application in the SRC industrial main plant , during designing of SRC frame structure in Daqing city, Heilongjiang province.

Failure Modes-Based Searching and Optimizing of Steel Reinforced Concrete Frame Structures

Taking the optimization of steel reinforced concrete frame structure as background, the searching and optimizing of structural were taken as optimization objectives by introducing failure modes. Incremental dynamic analysis (IDA) was used to search the seismic wave, which had important significance of the structure, thus, the failure modes under the seismic waves could be obtained. And three optimization methods were proposed. Finally, an example was analyzed to verify the rationality of the proposed optimization thought and method.

Response Analysis for Steel Reinforced Concrete Frame Structures under Earthquake Load

In order to understand the whole process of the steel reinforced concrete frame structure from elastic to elasto-plastic cracking gradually, damage until the collapse, the elasto-plastic finite element analysis theory and ETABS structural analysis software were used, then the spatial three-dimensional truss system model of frame structures was established. Based on the analysis of the elasto-plastic response for the frame structure under one-dimensional and two-dimensional earthquake load, the interbedded displacement angle-time curve and horizontal displacement-time curve were obtained. Through the analysis of the model, the sequence of appearance of plastic hinges in the frame structure under earthquake load was cleared and the weak location of the frame structure was detected.

Theoretical Analysis Research on Story Drift Limit for Steel Rinforced Concrete Composite Structures

Steel reinforced concrete structures are organic combination of steel and concrete and the calculation formula of inter-story drift should be between them.The calculation formula of storey yield drift for reinforced concrete frames is obtained by adding the deformantion of beams, columns and joints, and the comparison shows that theoretical results agree with test data. Inter-story yield drift ratio for steel reinforced concrete (SRC) framees are proposed by using the same assumption and procedure, and story drift limit for SRC frames with certain assurance probability are proposed according to relationship of four seismic performance levels. The conclusion obtained provide reference for engineering design of SRC frame structures.

Seismic Fragility Analysis of SRC Frame Structures

With the rapid development and extensive application of SRC (steel reinforced concrete) frame structures, the study on seismic fragility of SRC structure under earthquakes seems rather important. The seismic fragility of the SRC frame structures is studied by the method of Incremental Dynamic Analysis (IDA) in this paper. IDA method is conducted on 9 storey SRC frame structure to obtain the IDA curves of this model. Meanwhile, the seismic fragility of the model is analyzed to get the fragility curve. The result shows that IDA can describe the quantitative relationship between the exceeding probability of different states and damage degree of the target.

Research on Quantified Performance Index for Steel Reinforced Concrete Frame Structures

The interstory drift of frame structures is caused by beams, columns and joints. The calculation formula of storey yield drift for reinforced concrete frame structures is obtained by adding above three kind of deformation, and the comparative analysis show that theoretical results have good consistency with experimental data. The expression formula of storey yield drift angle for steel reinforced concrete (SRC) frame structures are analyzed by using the same hypothesis and methods, and quantified performance index for SRC frames having a certain guarantee value are proposed according to relationship of four seismic performance levels. The conclusion obtained provide basic information for performance-based seismic design of SRC frame structures.

Failure Modes-Based Multi-Objective Optimization Design of Steel Reinforced Concrete Frame Structures

The frame structure designed with the existing design code in zones of high earthquake intensity doesn’t satisfy with the expectation of strong column–weak beam. Therefore, a new optimal approach based on failure modes with the ability to limit the cost and the damage is proposed. In the process of optimization design, all the stories of a building with the same interstory drift is defined to obtiain the minor damage, while the damage values of beams and columns are difined to obtain the except failure modes. At last a six-story steel reinforced concrete frame structure is designed to verify the method developed inhere. It is concluded that the method can supply an effective way to reduce both the damage and the cost of steel reinforced concrete frame structure, and can obtain the except failure modes.

Dynamic Damage Analysis of SRC Frame Structure under Earthquake Action

Structures may enter into nonlinear stage under strong earthquake, so precise prediction of nonlinear behavior for building structure in earthquake is important which can assess the earthquake resistance safety of structures accurately. The exact numerical analysis model is required in actual engineering. In this paper the concept of nonlinear dynamic damage is introduced in steel reinforced concrete (SRC) composite structure, based on the theory of continuous damage mechanics. The damage variable is defined and computed by effective plastic strain of material, furthermore, concrete dynamic constitutive model is derived which considered plastic strain of material. Finally, the damage dynamic balance equation is established. Via comparison with test results of a three-story, two-bay SRC frame model which is tested on a shaking table, it is shown that the results of numerical analysis agree well with test results, indicating that the nonlinear dynamic balance equation is capable of describing the dynamic response of SRC frame structure with satisfactory accuracy. The research supplies theoretical basis for the seismic behavior analysis of SRC high-rise buildings.

Optimum design of SRC composite beams

Based on experimental study of bond-slip behaviours between steel shape and concrete, an optimal design scheme of single objective and discrete variables is proposed to design steel reinforced concrete (SRC) frame beams. In the optimum scheme, design variables include the layout dimensions of SRC frame structure, structural member sections, strength of concrete and steel, dimensions of steel shapes. The objective function is cost of the entire materials applied to construct SRC frame structure. The constraint conditions are main requirements stated in Chinese code for design of SRC structures, basic design rules, reasonable calculating theories and indispensable constructions, as well as some mature and consistent conclusions confirmed by experimental studies on calculating methods of SRC structures based on the bond-slip theory between steel shape and concrete. These may be a reference in analyzing and designing SRC frame structures and provide a practical method satisfying civil engineering practice and requirements stated in the codes.