Steel Reinforced Concrete Frame Research Articles

Crack detection and damage evaluation of asymmetrical steel-reinforced concrete frame nodes using acoustic emission technology

ABSTRACT Detecting cracks in steel-reinforced concrete (SRC) frame nodes is crucial for ensuring structural safety. This study employs acoustic emission (AE) technology to monitor the growth of concrete structural defects in real time. The aim is to establish a sensitive assessment method based on AE parameters to accurately assess the damage stages of SRC frame nodes by considering the complex crack extension mechanism in SRC structures. An experimental study of the AE characteristics of SRC frame nodes under low-cycle loading was performed. The crack evolution process of SRC frame nodes was monitored and analysed using the AE parameters. The results showed that ringing count is the AE parameter more sensitive to the damage of the SRC frame node. The damage evaluation method was established based on the variation coefficient analysis of the AE parameters. Considering the sudden change in the growth rate of the damage index, the damage evolution process of the SRC frame nodes can be accurately divided into three stages: initial crack compaction, rapid crack expansion, and crack penetration. These stages are consistent with the mechanical properties of SRC frame nodes.

Research on Restoring Force Model Characteristics of Prestressed Steel Reinforced Concrete Frames

On the basis of reasonable selection of material constitutive model, the numerical model of singlebay prestressed section steel-concrete frame. was constructed by using ABAQUS and Open SEES finite element software, respectively, and numerical analyses of the whole process of monotonic and hysteretic force were carried out, and the hysteretic characteristics of this type of frame. structure were analyzed. The main parameters affecting the hysteresis characteristics of this type of frame. were determined through parametric analysis, and the restoring force model was established as a result. The results show that: the numerical model constructed by ABAQUS software can intuitively reflect the damage morphology and stress distribution of the frame, and the simulated peak load is 191kN, with an error of 10% from the test; the numerical model constructed by OPENSEES finite element software can macroscopically reflect the energy-consuming capacity of the frame, and the simulated peak load is 186kN, with an error of 12% from the test; both the axial compression ratio and the length to slenderness ratio are sensitive parameters of prestressed steel and concrete members, the load capacity of the specimen increases with the increase of the design axial compression ratio, and decreases with the increase of the length and slenderness ratio, but too small length and slenderness ratio leads to the destruction of the specimen faster, which is not conducive to the ductility of the specimen; the prestressing effect on the ductility of the hysteresis curve is not obvious; according to the mechanical properties of the section, the geometrical parameters of the member, the restoring force constructed by means of linear regression can be a good fit for this type of frame.

IMPLEMENTATION OF BUILDING INFORMATION MODELING (BIM) PRINCIPLES AND INFORMATION TECHNOLOGIES FOR STRUCTURAL ANALYSIS IN THE DESIGN OF REINFORCED CONCRETE AND СOMPOSITE STEEL-REINFORCED CONCRETE FRAMED BUILDINGS

The development of Building Information Modeling (BIM) in historical context hasbeen analyzed, including CAD systems for 2D and 3D modeling, considered predecessors of modern BIM systems, parametric 3D modeling systems, the use of information technologies for structural analysis, issues of combined use of BIM systems and information technologies for structural analysis.Using the example of a 20-story frame-monolithic residential building, the sequence of creating a building information model in PC SAPPHIRE, forming a calculation model of the reinforced concrete frame in PC Lira-SAPR through direct integration of the specified software complexes is demonstrated. The issues of preparing a building information model in PC SAPPHIRE for transfer to PCLira-SAPR are discussed, as well as the issues of refining the calculation model in PC Lira-SAPR, including assigning stiffness and load characteristics, and selecting reinforcement for structural elements. Тhe sequence of creating a calculation model of a steel-reinforced concrete frame for three options of steel-reinforced concrete columns is considered: tubular concrete columns; tubular concrete columns with rigid reinforcement by cross steel strips; tubular concrete columns with rigid reinforcement by cross double T-sections.For the selected most loaded columns, mainly on the first floor, operating under the conditions of central or off-center compression, the sequence of forming refined calculation models is demonstratedby modeling these columns and areas of their connection to the floor slabs with 3D finite elements.Equivalent stress iso-surfaces are provided, as well as separate iso-surfaces of equivalent stresses of the steel shell and separately the concrete core of the columns

Quasi-static cyclic test on seismic performance of steel reinforced concrete frame with replaceable energy-dissipating member

In view of damage controlling and earthquake-resilient performance, the steel reinforced concrete (SRC) frame with replaceable energy-dissipating member (REDM) is proposed. The REDM is consisted of high damping concrete (HDC) wall panel and several fuses made by low yielding-point (LYP) steel. At first, low-cyclic reversed loading test on fuse is carried out to explore its shear capacity and hysteretic behavior. The suitable dimension and shape of fuse is determined for further study. Then the quasi-static cyclic test considering two loading patterns is applied on two SRC-REDMs. One specimen is loaded until overall failure while another is repaired by installing a new set of REDM during the loading history. The analyses and comparisons are conducted in terms of failure mode, yielding pattern, hysteretic characteristics, stress distribution, stiffness degradation, dynamic characteristics, ductility and energy dissipation. The failure mode is summarized as bending-shear failure of the wall panel, local buckling of fuses and beam hinge failure mechanism of SRC frame. The hysteretic loops are plump while large energy dissipation capacity is represented. The seismic performance is verified by high bearing capacity and ductility. The bearing capacity and stiffness of repaired specimen is significantly rehabilitated. The new REDM has dissipated much more hysteresis energy than that of non-repairing case. The earthquake-resilient behavior is confirmed by the significant recovery in mechanical properties.

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.

Seizmičko ponašanje spregnutih posmičnih stijena s AB okvirom ojačanim čelikom i ugrađenom perforiranom čeličnom pločom

Experiments are conducted on five shear wall specimens of varying design and structural measures in order to investigate seismic behaviour of a composite shear wall with the steel-reinforced concrete frame and an embedded perforated-steel plate. In addition, low-cyclic load is applied on test specimens that have a shear span ratio of 1.5. Using the experimental data, the bearing capacity, stiffness, ductility, hysteretic energy, and failure characteristics of five specimens are analysed. The results show that the composite shear wall (CSW) with the steel reinforced concrete frame (SRCF) and embedded steel plate (ESP) has higher bearing capacity, better ductility, slower degradation of stiffness, and higher energy dissipation capacity, as compared to an ordinary reinforced concrete shear wall. Moreover, its seismic behaviour can be improved by using the ESP of an appropriate thickness. For the ESPs of identical thickness, the results show that the specimen that uses steel ties exhibits better seismic behaviour than those using welding studs. Finally, a computing model that can calculate the bearing capacity of the CSWs is developed. A comparison of calculated and measured results shows that the results are close to each other.

Numerical simulation method of SRC frame column based on FLPH model

In order to obtain the accurate numerical simulation of seismic performance for steel reinforced concrete (SRC) frame columns, a convenient and reliable numerical simulation method needs to be established. Based on the test results, a numerical simulation method of SRC frame column based on the finite length plastic hinge (FLPH) was proposed in this paper. The plastic hinge element model was obtained through analyzing the failure process of SRC column. The length of plastic hinge for SRC column was expressed by considering the contribution of bending effect and strain penetration effect in the plastic deformation of members furtherly. On the basis of the numerical integration method, the FLPH model suitable for SRC frame column was established by introducing the section stiffness correction coefficient at the integral point of the element. Finally, using the OpenSees finite element analysis platform, the test specimens were simulated by FLPH model established in this paper. The results shown that the hysteretic curves obtained by simulation are well with the experimental curves, indicated that the numerical simulation method for SRC frame column based on FLPH model can be well applied in SRC structures.

Seismic Performance of Steel-Reinforced Concrete Columns with Q690 High-Strength Steel.

In this paper, based on the low-cycle loading tests of 11 steel-reinforced concrete (SRC) frame columns with built-in Q690 steel and 5 SRC frame columns with built-in Q235 steel, a systematic study on their seismic performance was carried out. The design parameters of the specimens were the steel strength, axial compression ratio, shear span ratio, steel content, and stirrup ratio. The failure modes, stress characteristics, hysteresis curve, skeleton curve, displacement ductility performance, energy dissipation capacity, and other main seismic indicators of the specimens with different parameters were analyzed, and the corresponding relationship between the displacement ductility performance of the specimen and the energy dissipation capacity and design parameters was obtained. The results show that the load–displacement curve of the specimens is relatively full, the descending section is gentle, and various seismic performance indicators are relatively excellent, reflecting good seismic performance. Equipped with high-strength steel SRC frame columns, they can better bear the horizontal load, the displacement ductility performance is improved, and the energy dissipation capacity is slightly lower than that of ordinary-strength steel SRC frame columns. The increase in the shear span ratio, steel content, and stirrup ratio of the specimens helps to improve their seismic performance, whereas an increase in the axial compression ratio makes their seismic performance worse.

Seismic performance of ductile corrosion-free reinforced concrete frames

<abstract> <p>Corrosion of steel bars is the main cause of the deterioration of reinforced concrete (RC) structures. To avoid this problem, steel rebars can be replaced with glass-fiber-reinforced-polymer (GFRP). However, the brittle behaviour of GFRP RC elements has limited their use in many applications. The use of shape memory alloy (SMA) and/or stainless steel (SS) rebars can solve this problem, because of their ductile behaviour and corrosion resistance. However, their high price is a major obstacle. To address issues of ductility, corrosion, and cost, this paper examines the hybrid use of GFRP, SS, and SMA in RC frames. The use of SMA provides an additional advantage as it reduces seismic residual deformations. Three frames were designed. A steel RC frame, SS-GFRP RC frame, and SMA-SS-GFRP RC frame. The design criteria for the two GFRP RC frames followed previous research by the authors, which aimed at having approximately equal lateral resistance, stiffness, and ductility for GFRP and steel RC frames. The three frames were then analyzed using twenty seismic records. Their seismic performance confirmed the success of the adopted design methodology in achieving corrosion-free frames that provide adequate seismic performance.</p> </abstract>

Research on Hysteretic Models for Prestressed and Non-Prestressed Steel Reinforced Concrete Frames

The beam-column fibre model is used to simulate the entire hysteretic process of the prestressed and non-prestressed steel reinforced concrete frame, and the results are compared with the test results. Based on the analysis of a large number of parameters, the hysteretic curve characteristics of this kind of composite frame are discussed, and the load-displacement hysteretic models of single-storey and single-span composite frame are established. The models can comprehensively consider the influence of axial compression ratio and column slenderness ratio and can predict the hysteretic behaviour of this kind of composite frame under horizontal loads. The load-displacement hysteretic models are consistent with the numerical simulation results. Relevant research can provide reference for simplifying the elastic-plastic dynamic analysis of structures.

Experimental and numerical study on seismic performance of steel reinforced concrete spatial frame with irregular section columns

In order to research the seismic performance of steel reinforced concrete (SRC) spatial frame with irregular section columns, a 1/4 scaled model of two-bay and five-story spatial frame was constructed and tested under low cyclic reversed loading. The failure pattern, hysteresis curves, ductility, drift angle, stiffness degradation, strength degradation and energy dissipation capacity were analyzed. The results showed that the plastic hinges firstly appeared at the end of beams, which obeyed the design principle of “strong-column weak-beam”. The hysteresis curves were plump, indicating that the spatial frame had excellent energy dissipation capacity, but pinched at the later loading stage. The strength degradation coefficients and displacement ductility coefficients were larger than 0.8 and 4.0, respectively, and the ultimate drift angle reached 1/19, showing that the spatial frame had stable bearing capacity, good ductility and strong ability to collapse resistance. Based on the test, finite element analysis software OpenSees was employed to evaluate the seismic performance of the spatial frame and the influence of loading direction, axial compression ratio and length-width ratio of column limb was analyzed. The research results can provide reference for the application of SRC frame with irregular section columns in earthquake fortification zone.

Pseudodynamic Testing of Buildings Retrofitted with External Steel Reinforced Concrete Frames to Increase Lateral Strength for Earthquake Damage Prevention

In this study, a new technique for seismic retrofitting via the attachment of an “external steel reinforced concrete frame” (ESRCF) system was developed to strengthen medium-to-low-rise reinforced concrete (RC) buildings. Two methods (bolting and welding) were developed to connect existing RC frames and external strengthening elements; these methods are technically and practically suited to various construction conditions. The retrofitting method developed in this study can be used to perform seismic strengthening construction, while residents continue to live within the building. The method is categorized as a “strength design approach” implemented via retrofitting, allowing the lateral ultimate load capacity of RC buildings, whose failure mode is shear, to be increased easily. Test specimens were designed based on an existing RC building in Korea lacking seismic data and then strengthened using the ESRCF system. Pseudodynamic and cyclic loading tests were conducted to verify the effects of seismic retrofitting. In total, four RC frame specimens were prepared: one nonstrengthened control specimen for the cyclic loading test, one nonstrengthened control specimen, one specimen strengthened with a welded ESRCF system, and one specimen strengthened with a bolted ESRCF system for the pseudodynamic test. The earthquake response behavior with use of the proposed method, in terms of the maximum response strength, response displacement, and degree of earthquake damage, is compared with a control RC frame. The test results indicated that both the bolting and welding methods used for connecting the existing RC frame to the ESRCF effectively increased the lateral ultimate strength, resulting in reduced response displacement of building structures under large-scale earthquake conditions.

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.

Post-fire seismic performance of SRC beam to SRC column frames

This paper investigates the post-fire seismic performance of steel reinforced concrete (SRC) beam to SRC column frames. Five SRC column to SRC beam planar frame specimens were tested in a program including a loaded fire test and a following horizontal cyclic loading test. Test parameters included heating time and column load ratio. The temperature development, deformation, post-fire hysteretic and skeleton curves, stiffness, ductility and damping coefficient of SRC frames are recorded, calculated and analyzed. The measured post-fire hysteretic curves indicates that the SRC frames exhibit very good energy dissipation capacity after fire exposure. The horizontal load capacity and viscous damping coefficient of SRC frames increase with the increase of column load ratio. However, column load ratio has an adverse influence on ductility as anticipated at normal temperature. One SRC frame specimen failed during the cooling phase, which demonstrates the importance of considering the cooling phase during the fire safety design.

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.

Hysteretic Behavior of Steel Reinforced Concrete Columns Based on Damage Analysis

With the aim to model the seismic behavior of steel reinforced concrete (SRC) frame columns, in this research, hysteresis and skeleton curves were obtained based on the damage test results of SRC frame columns under low cyclic repeat loading and the hysteretic behavior of the frame columns was further analyzed. Then, the skeleton curve and hysteresis loops were further simplified. The simplified skeleton curve model was obtained through the corresponding feature points obtained by mechanical and regression analysis. The nonlinear combination seismic damage index, which was developed by the test results and can well reflect the effect of the loading path and the number of loading cycle of SRC frame columns, was used to establish the cyclic degradation index. The strength and stiffness degradation rule of the SRC frame columns was analyzed further by considering the effect of the accumulated damage caused by an earthquake. Finally, the hysteresis model of the SRC frame columns was established, and the specific hysteresis rules were given. The validity of the developed hysteresis model was verified by e comparison between the calculated results and the test results. The results showed that the model could describe the hysteresis characteristics of the SRC frame columns under cyclic loading and provide guidance for the elastoplastic time-history analysis of these structures.

Detailed numerical research on the performance of unbonded prestressed SRC frame beam under vertical cyclic load

Prestress tendons can be used to improve the serviceable performance of steel reinforced concrete (SRC) beam members. To have a comprehensive understanding of the seismic behaviors of unbonded prestressed SRC beam members, fifteen frame beam specimens, including thirteen unbonded prestressed SRC ones and two ordinary SRC ones, were designed to make the numerical multi-parameter analysis. The parameters considered were the amount of unbonded tendons, rebar, flange and web thickness of steel shape. In the paper, the load-carrying capacity, strain of steels and concrete, ductility, energy dissipation, deformation restoring capacity, stiffness and strength degradation were detailed analyzed and discussed. The results indicated that increase the amount of unbonded tendons would lower the utilization efficiency of steel and decrease the energy dissipation capacity. Raising the amounts of tendons, rebar or steel shape would reduce the specimen’s ductility and the ductility coefficient had a good linear relationship with the introduced integrate reinforcement index. According to the numerical analysis, several brief design suggestions were provided for reference. Moreover, compared with the ordinary SRC specimens, it could be observed that the energy dissipation capacity of prestressed SRC members was relatively lower, while its deformation capacity was as good as ordinary SRC ones. The application of unbonded tendons in SRC beam members greatly improved its serviceability and deformation restoring capacity.

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.

Dynamic performance of a composite building structure under seismic ground motions

This study is aimed at investigating the dynamic performance of a composite building structure under seismic ground motions. The building structure is an official fire department building located in southern Taiwan. It is composed of a seven-story reinforced concrete (RC) and an eight-story steel reinforced concrete (SRC) frame. Both frames share a common basement and are separated by expansion joints from the first to the seventh floor. Recorded floor accelerations of the building structure under eight earthquakes occurring during the period from 2011 to 2013 were examined in this paper. It is found that both frames had similar floor acceleration amplifications in the longitudinal direction, while the SRC frame revealed larger response than the RC frame in the transverse direction. Almost invariant and similar fundamental periods under the eight earthquakes in both directions were obtained from their transfer functions. Furthermore, numerical time-history simulations were carried out for the building structure under the most intensive earthquake. It is realized that the seismic response of the composite building was dominated by the first translational mode in each horizontal direction. Higher modes did not significantly contribute to the structural response. The conventional Rayleigh damping model could be appropriately applied to the time-history simulations under bi-directional excitations. Approximate floor acceleration envelopes were obtained with a compound RC and SRC structural model by using the average damping ratios determined from the different structural arrays.

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.