Seismic Performance Of Frame Structures Research Articles

Seismic Performance of Frame Structure with Hysteretic Intermediate Discontinuity

The introduction of an intermediate discontinuity in frame structures is commonly named inter-storey isolation. Inter-storey isolation is an effective technique for the seismic protection of new or existing frame structures. The devices that are used to perform the discontinuity, mainly of the structural stiffness, are placed at a higher storey level of the structure and not at the base level. In the latter years, this technique has gained increasing interest because, especially for existing buildings, it is cheaper and technically easier to implement than base isolation. In this paper, the attention is focused on the effects on a frame structure of an intermediate elasto-plastic discontinuity that can be described by a Bouc-Wen model. The frame structure with the intermediate discontinuity is modelled with a 3-DOF reduced model. Its dynamical behaviour is investigated by considering both harmonic and seismic external excitation. The results are summarized in gain maps aimed at finding the parameters that optimize the seismic behaviour of the structure.

Elasto-Plastic Short Exoskeleton to Improve the Dynamic and Seismic Performance of Frame Structures

The coupling with external mechanical systems such as oscillating masses working as tuned mass dampers, dynamic mass absorbers, elasto-plastic dampers, and rigid walls is an effective method to reduce the displacements and drifts of structures under external loads. An alternative method is provided by the coupling of the structure with an independent, auxiliary elasto-plastic system. This paper investigates the dynamic and seismic behaviour of a structure rigidly coupled with an auxiliary yielding mechanical system under harmonic and seismic ground excitation. A two-degree-of-freedom model is used to describe the dynamic and seismic behaviour of the main structure rigidly coupled to the yielding system, which is described by a one-degree-of-freedom model. The auxiliary system has an elasto-plastic constitutive behaviour that is modelled by a Bouc-Wen model. The equations of motion of the coupled system are obtained by a direct approach. The coupling with the yielding system is considered beneficial if the displacements of the coupled system reduce with respect to those of the stand-alone frame structure. An extensive parametric analysis is performed to point out the role of the mechanical parameters that describe the elasto-plastic constitutive behaviour of the auxiliary system. Results reveal that in large ranges of the parameters’ values, the coupling with the elasto-plastic system improves the performance of the frame structure.

Experimental study on the seismic performance of RC frames considering the cast sequence of infilled walls and columns

The relative values of lateral stiffness and ultimate limit state of bearing capacity of vertical members are defining factors of the seismic failure or collapse mode of structures. This paper focuses on how the different construction sequences of infilled walls and frame columns influence the seismic performance of frame structures based on the low-cycle reciprocating loading tests of six single-layer two-span frame structure models with a ratio of 1:4, including two frame models without infilled walls (F model), two frame models with walls built later (LW model), and two frame models with walls built first (FW model).According to the test results, different construction sequences of infilled walls have a significant impact on the seismic performance of frame structures. The FW model introduces the process of “building the wall first and then casting the column” with the wall and the column highly combined with each other and the infilled wall involved in the internal force distribution of the frame structure, boasting the largest bearing capacity and initial stiffness; LW model is built by “pouring the column first and then building the wall” with a low combination between wall and column, its bearing capacity and initial stiffness second to FW model; F model has the smallest bearing capacity and initial stiffness. Shear failure and poor ductility are found in the FW model due to the restraint effect of the infilled wall; bending failure in the F model with a large displacement but good ductility; shear failure tends to appear in the LW model structure with the failure in bonding between reinforcement and concrete in the end and good ductility. The research results can provide a reference for the elastic–plastic seismic response analysis considering the interaction of infilled wall and frame.

Research on Seismic Performance of Frame Structure with Beam Staircases

Beam staircases are widely used in frame structures. In structural design, stair flights are often ignored in the model establishment, and their loads are only added to the stair beams. However, under a seismic load, the flight of stairs will increase the staircase’s stiffness and affect the seismic response characteristics of the stairs and even of the structure. According to the engineering example, the finite element numerical models of the pure frame structure without staircases, the frame structure with fixed connection beam staircases, and the frame structure with sliding connection beam staircases were established. Modal analysis, response spectrum analysis, and elastic time-history analysis were carried out. By comparing the maximum story displacement, story displacement angle, natural period, story shear force, and the internal force of components of each model, the influences of beam staircases and their bearing connection mode on the seismic performance of the building were analyzed. In addition, by examining the frame model with sliding connection beam stairs, the influences of different staircase positions on the seismic performance of the building were studied. Finally, the advantages and disadvantages of different design schemes were compared, and the effects of the modeling method, support type, and layout position of the beam staircases on the seismic performance of the frame structure were summarized. The conclusions are that the story drift angle of the sliding connection structure is larger than that of the fixed connection structure, and the internal force of the frame columns of the former is smaller than that of the latter. Moreover, the positions of the staircase will affect the horizontal displacement of the structure.

Dynamic behavior and seismic performance of base-isolated structures with electromagnetic inertial mass dampers: Analytical solutions and simulations

The newly-developed electromagnetic inertial mass damper (EIMD) consisting of an inerter element and a damping element can significantly enhance the seismic performance of frame structures. However, whether an EIMD can enhance the seismic performance of a base-isolated structure (BIS) remains largely unknown. This paper presents a comprehensive theoretical study of the BIS with an EIMD, stressing on the dynamic behavior, parameter optimization, and seismic performance. Based on a simplified two-degree-of-freedom model, we derive the closed-form solutions of the dynamic characteristic parameters, modal participation factors, and dynamic amplification factors. A parametric study is conducted to investigate the effects of the EIMD parameters on the dynamic behavior of the system, through which the seismic response control mechanism of the EIMD in BIS is comprehensively analyzed. When the BIS subjected to a total of 20 earthquake records, the parameters of the EIMD are optimized for minimizing the interstory drift of the superstructure, the absolute acceleration response of the superstructure, and the relative displacement response of the base floor, individually. The effectiveness of the EIMD in enhancing the seismic performance of base-isolated structures is validated via numerical simulation of a five-story isolated building structure. Under a typical earthquake ground motion, the peak relative displacement of the base floor is reduced by up to 56.57% in comparison to traditional BIS; whereas the peak relative displacement and the absolute acceleration of the superstructure are reduced by up to 60.00% and 52.11%, respectively. Both analytical and numerical results demonstrate that the EIMD can significantly reduce the dynamic responses of both the base floor and the superstructure.

Cyclic Tests and Numerical Analyses on Bolt-Connected Precast Reinforced Concrete Deep Beams

A bolt-connected precast reinforced concrete deep beam (RDB) is proposed as a lateral resisting component that can be used in frame structures to resist seismic loads. RDB can be installed in the steel frame by connecting to the frame beam with only high-strength bolts, which is different from the commonly used cast-in-place RC walls. Two 1/3 scaled specimens with different height-to-length ratios were tested to obtain their seismic performance. The finite element method is used to model the seismic behavior of the test specimens, and parametric analyses are conducted to study the effect on the height-to-length ratio, the strength of the concrete and the height-to-thickness ratio of RDBs. The experimental and numerical results show that the RDB with a low height-to-length ratio exhibited a shear–bending failure mode, while the RDB with a high height-to-length ratio failed with a shear-dominated failure mode. By comparing the RDB with a height-to-length ratio of 2.0, the ultimate capacity, initial stiffness and ductility of the RDB with a height-to-length ratio of 0.75 increased by 277%, 429% and 141%, respectively. It was found that the seismic performance of frame structures could be effectively adjusted by changing the height-to-length ratio and length-to-thickness of the RDB. The RDB is a desirable lateral-resisting component for existing and new frame buildings.

Seismic vulnerability of prefabricated reinforced concrete frame structure based on local outsource steel tube bolted column–column connection

In this paper, the seismic performance of a prefabricated frame structure with a local outsource steel tube bolted column–column connect is evaluated from the perspective of seismic vulnerability theory. Firstly, a simplified model of the prefabricated frame structure was constructed and validated by experiments. Then, a six-story prefabricated reinforced concrete frame structure (PRCS) and a cast-in-situ reinforced concrete frame structure (CRCS) were designed as examples to get the increment dynamic analysis (IDA) of the structure under 12 ground motions, and the two-parameter damage model was used as the structural requirement index. As a traditional structural requirement index-the maximum inter-storey drift angle cannot accurately describe the mechanism of structural damage. Therefore, two types of damage models are compared and analyzed. In addition, in order to evaluate the damage of frame structure effectively, a new damage index weighted combination method is proposed, and its feasibility is verified. Finally, the IDA curve and vulnerability curve with Kunnath two-parameter damage model and the maximum inter-story displacement angle as the requirement index are drawn. The results show that the two-parameter damage model is more accurate than the maximum inter-storey drift angle model in evaluating the seismic performance of the PRCS and CRCS. It shows that the maximum inter-story displacement angle model can overestimate the collapse resistance of the PRCS by 60.7% on average, and the collapse resistance of the CRCS by 75.67% on average. The seismic performance of the CRCS is better than that of the PRCS as the seismic intensity increases. Although the seismic performance of fabricated columns is similar to that of cast-in-place columns, there is still a certain gap in the seismic performance of frame structures.

Study on seismic performance of frame structure with viscous damping staircase

Based on the significant energy dissipation performance of the viscous damper, the force-displacement hysteresis curve is full and the Maxwell mechanical model has a weak dependence on vibration frequency. Combining the failure mode of the staircase damage with the Maxwell mechanical model, this paper proposes an earthquake-resistant frame staircase model with damped bearings. A finite element analysis of a nine-story reinforced concrete structure is performed using SAP2000. By setting three different connection methods on the staircase structure, the similarities and differences of different staircase structures to the input seismic wave feedback are analyzed to compare the advantages and disadvantages of its seismic performance.

Seismic performance of frame structures coupled with an external rocking wall

Frame structures can be coupled with external mechanical systems to improve their behaviour under external loads. Some examples of such mechanical systems are oscillating masses working as tuned mass dampers, dynamic mass absorbers, elasto-plastic dampers. Among the others possibilities, a rocking rigid block can be used to improve the seismic behaviour of a frame structure. In this paper a two degree of freedom model is considered representative of a general frame structure. It is coupled with a rocking rigid block through a visco-elastic device, which connects the lower part of the structure with the top of the rocking block. A Lagrangian approach is used to derive the nonlinear equation of motion that are successively solved numerically. A simulation campaign is performed to analyse the seismic behaviour of the coupled system by considering several registered earthquakes. In the analyses, the presence of rocking rigid block is assumed to be beneficial for the system if the coupling of frame structure with rocking rigid block reduces the absolute displacements and/or the inter-storey drifts. An extensive parametric analysis is performed varying the geometric characteristics of the block and the constitutive behaviour of the visco-elastic devices. The results of such analyses are presented through behaviour maps. For each of the parameters varied in the analyses, the corresponding value on the map provides ratio between displacements (or inter-storey drifts) of coupled system and of uncoupled bare frame. Such maps allow an immediate understanding of the effects of the block that has a beneficial effect when the ratio of the displacements is less than unity. Results reveal that in large ranges of the parameters’ values the rocking rigid block improves the seismic response of frame structure.

A novel procedure for the assessment of the seismic performance of frame structures by means of limit analysis

Limit analysis is a computationally efficient tool to assess the resistance and the failure mode of structures but does not provide any information on the displacement capacity, which is one of the concepts which most affects the seismic safety. Therefore, since many researchers did not consider limit analysis as a possible tool for the seismic assessment of structures, its widespread employment has been prevented. In this paper this common belief is questioned and the authors show that limit analysis can be useful in the evaluation of the seismic performance of frame structures. In particular, to overcome the limitation on the possibility to evaluate the displacements of a structure based on a limit analysis approach, an approximated capacity curve is reconstructed. The latter is based on a limit analysis strategy, which takes into account the second order effects, and evaluates the displacement capacity considering a post-peak softening branch and a threshold on the allowed plastic rotations. Then, based on this simplified capacity curve, an equivalent single degree of freedom system is defined in order to assess the seismic performance of frame structures. The proposed simplified strategy is implemented in a dedicated software and the obtained results are validated with well-established approaches based on nonlinear static analyses, showing the reliability and the computational efficiency of this methodology.

Soil-structure interaction effects on the seismic performance of frame structures

In this work, a numerical attempt has been elaborated to study the effects of soil properties, seismic impact and interaction between frame structure and soil foundation. The frame, soil and interface continuum have been modeled by using the finite element concept. In this approach, a numerical program has been established based on the direct method to analyze the soil-structure interaction under seismic loading. Adding, the developed thinlayer interface element ensuring the incompatibility of degrees of freedom between frame and soil elements is incorporated. Obtained results lead to explain (1) the influence of the soil-structure interaction on the seismic response of the frame structure and interface media, (2) the time history deflection of the superstructure and interface medium under seismic loading, (3) the effect of the interaction factor of soil-structure interaction on the seismic behavior of the interface medium and frame structure and (4) the earthquake intensity on the seismic damage. Lateral displacements at the top of the frame and at the interface level, and shear stresses at the contact between the foundation and structure are plotted and commented.

Simultaneous Effects of Soil-structure and Masonry Infill-Structure Interactions on Seismic Performance of Steel Frames

In this paper, the effects of dynamic Soil-Structure Interaction (SSI) on seismic performance of steel frames with infill wall were investigated. This study assesses these buildings seismic performance utilizing the static analysis of nonlinear simulated models to obtain the structures response. The investigation was based on structures with design and detailing characteristics representative of 2800 Iranian code. To consider the dynamic soil-structure interaction effect, soil can be modeled with a set of springs and dashpots. The results show soil-structure interaction and presence of infill wall in building can be able to change the seismic performance of frame structures. Dynamic soil-structure interaction increases system flexibility. Increasing the number of column spans in all cases of loading, increases the amount of the base shear and story drift. The analysis results, also, show that reducing the shear wave velocity in soil beneath the structure, causes soil-structure interaction effects on nonlinear structural response become significant.

The Impact of Infilled Wall on Seismic Performance of Frame Structure

In accordance with damages of infilled wall frame structures in Wenchuan earthquake, the current 2010 version of "Seismic Design Code of Building" is attached herewith increasing significance to infilled wall, which switches "consider the impact of infilled wall on seismic performance of frame structure and avoid main structure destruction caused by setting infilled wall unreasonably " from a general provision into a mandatory provision, however, a specific quantitative description on the impact of infilled wall on seismic performance of frame structure is still absent. The impact of infilled wall on seismic performance of frame structure is analyzed in the paper, and two suggestions pertain to design and research of infilled wall is proposed under current phase: on the one hand, "conceptual design" should be kept on highlighting in the seismic design of infilled wall frame structures; on the other hand, based on the concept of "performance-based seismic design", the idea that infilled wall should be treated distinctively is put forward.

The Initial Stress Effect on Seismic Performance of Frame Structure

For frame structure, due to the uneven settlement of foundation, makes the whole framework of system with initial stress caused by uneven displacement, thus produce unfavorable influence on seismic performance of frame structure. By PMCAD modeling software and finite element module SATWE, analyse the initial stress effect on seismic performance of frame structure.Results show that under the influence of initial stress, the frame structure seismic performance declined.

SEISMIC EVALUATION AND RETROFIT OF AN ASYMMETRIC REINFORCED CONCRETE FLAT SLAB BUILDING

Seismic performance evaluation of existing structures and retrofit strategies are considered as a complicated multi-criteria problem. This study presents a performance evaluation of a gravity load designed or designed to earlier codes six stories asymmetrical flat slab building. Building with flat slab system may lack the required lateral stiffness to withstand seismic lateral loads. Three different retrofit systems to increase the lateral strength and stiffness of the building are proposed and examined. These systems include the addition of external frames, using shear walls and introducing steel knee bracing. The 3-D nonlinear pushover analysis procedure is utilized in evaluating the seismic performance of the original building and the retrofitted one, capacity and demand spectrum curves are presented for each studied case. The results are compared with elastic time history analysis method. Three different real earthquake records with intensities suitable for zones I, III and IV appeared in the renewed (2003) version of the Egyptian code of loads are utilized. It is found that the applied 3-D nonlinear analysis can be considered as a powerful tool in evaluating the seismic performance of frame structures. The study also shows that how can every suggested retrofitting system upgrade the seismic behavior of the gravity load designed flat slab building. Cost analysis comparison study is carried out.

Seismic performance of frame structures with recycled aggregate concrete

This paper deals with an experimental study on the seismic performance of frame structures with recycled aggregate concrete (RAC). Based on the seismic tests of four 1:2-scaled frame specimens under low-frequency cyclic lateral load with constant vertical actions, the failure pattern, the hysteresis curves, the skeleton curves, the energy dissipation capacity, and the stiffness degradation laws of frame structures with recycled coarse aggregate (RCA) are investigated. The effects of different RCA replacement percentages (i.e., 0, 30%, 50% and 100%) on the seismic performance of the reinforced recycled aggregate concrete frames are emphasized and analyzed in detail. It is concluded that the general seismic behaviour of a frame structure with recycled aggregate concrete declines with an increase of the RCA replacement percentage. Nevertheless, a frame structure with a higher content of RCA still behaves well enough to resist an earthquake attack.

Seismic response of reinforced concrete frame subassemblages — a Canadian code perspective

The 1984 CSA standard for the design of concrete structures for buildings provided new seismic design and detailing requirements for concrete structures. Full-scale, reversed cyclic loading tests of reinforced concrete beam–slab–column subassemblages were carried out to investigate the seismic performance of frame structures designed with the latest Canadian code. The test results indicate the importance of including the influence of slab reinforcement in computing the beam capacity as well as the need to carefully design the joint regions for shear. The test results indicate the excellent performance of frame components designed with K = 0.7 (R = 4.0) and the poor performance of those designed and detailed with K = 2.0 (R = 1.5). The performance of subassemblages designed with K = 1.3 (R = 2.0) depends on the column to beam strength ratio and on the shear strength of the joints. Models to predict the flexural response as well as the shear response of key elements are described and the role of the spandrel beam in limiting the effective slab width is explained. Key words: seismic design, reinforced concrete, detailing, structures, codes.