Wall-frame Structures Research Articles

Seismic performance evaluation of an infilled rocking wall frame structure through quasi-static cyclic testing

Earthquake investigations have illustrated that even code-compliant reinforced concrete frames may suffer from soft-story mechanism. This damage mode results in poor ductility and limited energy dissipation. Continuous components offer alternatives that may avoid such failures. A novel infilled rocking wall frame system is proposed that takes advantage of continuous component and rocking characteristics. Previous studies have investigated similar systems that combine a reinforced concrete frame and a wall with rocking behavior used. However, a large-scale experimental study of a reinforced concrete frame combined with a rocking wall has not been reported. In this study, a seismic performance evaluation of the newly proposed infilled rocking wall frame structure was conducted through quasi-static cyclic testing. Critical joints were designed and verified. Numerical models were established and calibrated to estimate frame shear forces. The results evaluation demonstrate that an infilled rocking wall frame can effectively avoid soft-story mechanisms. Capacity and initial stiffness are greatly improved and self-centering behavior is achieved with the help of the infilled rocking wall. Drift distribution becomes more uniform with height. Concrete cracks and damage occurs in desired areas. The infilled rocking wall frame offers a promising approach to achieving seismic resilience.

Modified spectrum-based pushover analysis for estimating seismic demand of dual wall-frame systems

Although many advanced pushover-based models have been developed for the fast prediction of seismic demand of tall buildings, most of these models are only focused on the analysis of moment-resisting frame structures. The seismic behaviour of dual wall-frame structures is very different from that of a moment-resisting frame structure, as structural walls and frames have totally different deflected shapes under the action of lateral loading, thus resulting in a strong structural interaction between the two load-resisting systems. There are few pushover-based models, in which the different structural responses between structural walls and frame structures are included. In this paper, modification of the spectrum-based pushover analysis (SPA) is presented to consider the structural interaction between shear walls and frames and the different damage modes of a dual wall-frame structure. In the modified spectrum-based pushover analysis (MSPA) method, the force vectors applied to the structure and formulations for determining the total roof displacement are changed to take the wall-frame interaction into account. The applicability and accuracy of MSPA in predicting the seismic demand of dual wall-frame structures are investigated through a case study of four 25-storey reinforced concrete wall-frame structures subjected to different levels of the input ground motions. Comparison of the results from nonlinear response time history analysis (NLRHA), several advanced pushover-based models and the proposed MSPA method has been made. It is seen that only MSPA can predict the distribution of the seismic demand along the height of buildings well, and the seismic demand from MSPA shows very good agreement with that from NLRHA.

Energy distribution in RC shear wall-frame structures subject to repeated earthquakes

Repeated earthquakes are possible events in seismic zones. The aftershocks can grow so large that they can be regarded as design-level earthquakes. These can affect the nonlinear behavior of structures. Different studies indicated that the destructions caused by earthquakes were highly influenced by the seismic energy induced to the structure during the earthquake. This study investigated the seismic behavior of RC shear wall-frame structures and the structural response and energy distribution in these structures subject to single and sequence of natural records. To this end, 10-, 15-, and 20-story structures were assessed for the selected structural system. Previous studies assessed the displacement, maximum drift, maximum residual drift, and energy distribution in structures. Therefore, this research aimed to study the records of the repeated sequences and their energy concepts. The results of analyses revealed that repeated earthquakes led to increase in seismic requirements of RC shear wall-frame structure, but it did not cause structural collapse. In addition, the presence of the second record reduced the residual structural displacement in some cases. Nevertheless, the effect of repeated earthquakes should be taken into consideration in the assessment of the reliability of structures. Other results on energy distribution indicate that an increase in the structure height will possibly increase the contribution of α[M] and decrease the contribution of β[K] in dissipation of input energy.

Study of Shear Wall Frame Structure Subjected to Earthquake Loading in G+15 Building

Study of Shear Wall Frame Structure Subjected to Earthquake Loading in G+15 Building

Experimental investigations on permanent magnet based wheel mechanism for safe navigation of climbing robot

This paper presents excremental studies on permanent magnet based wheel mechanism for safe navigation of climbing robot on ferrous wall surface structures. Three types of wheel mechanism (Wheel 1, Wheel 2 and Wheel 3) are manufactured and compared for their working performance experimentally for climbing robot locomotion trials. The Wheel 1 mechanism with MS hub is very compact, simple in design with easy assemble/dissemble features, and having less manufacturing cost. However, the adhesion force of the prototype wheel is comparable with already reported permanent magnet based adhesion mechanism. Wheel 1 design is further improved by developing Wheel 2 and 3 versions by changing hub material from mild steel to Aluminum. These wheel mechanisms are light in weight and more powerful to achieve maximum adhesion force i.e., 210 N and 251 N with and without rubber grip, respectively, at only 200 gm wheel weight as compared to previously reported permanent magnetic adhesion mechanism. Thus, more payload carrying capacity climbing robot can be developed using these developed mechanisms for field trials of climbing robot. A comprehensive experimental study on the influence of rubber grip thickness, air gap, wheel tilt angle and test surface thickness variation on adhesion force of these developed wheel mechanisms have been reported. The influence of both static and kinetic coefficient of friction (COF) for vertical surface locomotion of climbing robot has also been investigated. These developed wheel mechanisms have been further demonstrated using a four-wheel differential drive prototype-climbing robot for safe navigation testing first on a 2-D framed plane wall structure and next on a 3-D framed wall structure. It is found from the laboratory trials that based on these wheel mechanisms, the climbing robot can safely navigate remotely on even surface for these chosen structures.

Linear‐elastic lateral load analysis and seismic design of pin‐supported wall‐frame structures with yielding dampers

SummaryThis paper describes an analytical investigation on a reinforced concrete lateral load resisting structural system comprising a pin‐supported (base‐rocking) shear wall coupled with a moment frame on 1 or both sides of the wall. Yielding dampers are used to provide supplemental energy dissipation through the relative displacements at the vertical connections between the wall and the frames. The study extends a previous linear‐elastic model for pin‐supported wall‐frame structures by including the effects of the dampers. A closed‐form solution of the lateral load behavior of the structure is derived by approximating the discrete wall‐frame‐damper interactions with distributed (ie, continuous) properties. The validity of the model is verified by comparing the closed‐form results with computational models using OpenSees program. Then, a parametric analysis is conducted to investigate the effects of the wall, frame, and damper stiffness on the behavior of the structure. It is found that the damper stiffness significantly affects the distribution of shear forces and bending moments over the wall height. Finally, the performance‐based plastic design approach extended to the wall‐frame‐damper system is proposed. Case studies are carried out to design 2 damped pin‐supported wall‐frame structures using the proposed approach. Nonlinear dynamic time‐history analyses are conducted to verify the effectiveness of this method. Results indicate that the designed structures can achieve the performance level with the story drift ratios less than target values, and weak‐story failure mechanism is not observed. The approach can be used in engineering applications.

Performance evaluation of infilled rocking wall frame structure

SummaryConventional reinforced concrete (RC) frame structures are prone to soft‐story mechanism. This deficiency can be eliminated by introducing rocking wall system. Previously studied rocking wall systems usually have the rocking wall situated outside the frame, which results in some challenges and inconvenience. In the study, a novel infilled rocking wall frame (IRWF) system is proposed, which uses infilled RC wall to create a rocking wall within the RC frame. To evaluate seismic performance of the proposed system, both an IRWF model and an RC frame (RCF) model were designed according to Chinese seismic design code. Time history analysis and incremental dynamic analysis were conducted to compare both systems. The results show that IRWF system has more uniform drift and higher collapse margin ratio compared to the RCF system. Economic evaluation of IRWF system was investigated using the state‐of‐the‐art ATC‐58 performance‐based assessment methodology. The result shows superior performance of the IRWF system. The annualized loss of the IRWF model is about 28% less than the RCF model. This shows IRWF system is a viable and efficient alternative resilient seismic force resisting system.

Experimental Study on Seismic Performance of Full Precast Shear Wall-Frame Structures

To study the seismic behaviors of full precast shear wall-frame structures with prefabricated shear wall panels and prefabricated frames. Two geometrically identical half-scale two-story two-bay RC shear wall-frame structure specimens were constructed and tested under quasi-static reversed cyclic loading (One specimen named RC-1 is cast-in-place concrete shear wall-frame structure, the other one is a precast specimen named PC-3). The test results show that the specimen PC-3 have similar failure pattern with the specimen RC-1. The experimental investigation indicates that the reliably connected, well-designed and constructed full prefabricated shear wall-frame structures with prefabricated shear wall panels and prefabricated frames, have good seismic performance and can meet the seismic requirements and be used in anti-seismic zone.

Experimental investigation on reparability of an infilled rocking wall frame structure

SummaryImproving seismic performance is one of the critical objectives in earthquake engineering. With the development of economy and society, reparability and fast resilience of a structure are becoming increasingly important. Reinforced concrete (RC) frame structure is prone to soft story mechanism. As a result, deformation and damage are so concentrated that reparability is severely hampered. Rocking wall provides an available approach for deformation control in RC frame by introducing a continuous component along the height. Previous researches mostly focus on seismic responses of rocking wall frame structures, while damage mode and reparability have not been investigated in detail. In this study, a novel infilled rocking wall frame (IRWF) structure is proposed. A half‐scaled IRWF model was designed according to Chinese seismic design code. The model was subjected to cyclic pushover testing up to structure drift ratio of 1/50 (amplitude 1/50), and its reparability was evaluated thereafter. Retrofit was implemented by wrapping steel plates and installing friction dampers. The retrofitted model was further loaded up to amplitude 1/30. The IRWF model showed excellent reparability and satisfactory seismic performance on deformation control, damage mode, hysteresis behavior, and beam‐to‐column joint rotation. After retrofitting, capacity of the model was improved by 11% with limited crack distribution. The model did not degrade until amplitude 1/30, due to shear failure in frame beams. The retrofit procedure was proved effective, and reparability of the IRWF model was demonstrated. Seismic resilience tends to be achieved in the proposed system.

Seismic Behavior of Shear Wall-Frame Systems Considering Foundation Stiffness

In this paper, the influence of foundation stiffness on the seismic behavior of shear wall-frame systems was investigated. First, a basic differential equation was established to account for the interaction between the foundation and superstructure. By solving the equation, the influence of foundation stiffness on the lateral stiffness, inter-story drift, and internal force distribution of the superstructure at the elastic stage was elucidated. Subsequently, the concept and method for determining the range of foundation stiffness suitable for shear wall-frame systems were proposed. By taking a 12-story shear wall-frame structure built on a shallow foundation as an example, a parametric study was performed for various frame-to-wall relative stiffness ratios and foundation stiffnesses. The effect of shallow foundation stiffness on the base shear distribution and energy dissipation of the superstructure was clarified, with results compared with those of the fixed-base model. The analysis results indicated that the degeneration of foundation stiffness due to earthquake damages will result in significant redistribution of internal forces, namely, the internal forces of the walls decrease, while those of the frames increase. In particular, the shear-force and bending moment of the bottom frame columns rise drastically, which may greatly reduce the safety margin and should be considered in practical design.

Generalized finite element analysis of high-rise wall-frame structural systems

PurposeThis paper aims to propose a generalized finite element technique that can accurately approximate the solution of the flexural-shear cantilever model of wall-frame structures proposed by Heidebrecht and Stafford Smith.Design/methodology/approachThis approach adopts scaled monomials as enrichment functions, and they are highly effective in accurately capturing the solution of the problem, as it consists of smooth functions such as polynomials, hyperbolic and trigonometric functions. Several numerical experiments are performed on the static and modal analyses of the flexural-shear cantilever wall-frame structures using the proposed generalized finite element method (GFEM), and their accuracies are compared with those obtained using the standard finite element method.FindingsThe proposed GFEM is able to achieve theoretical convergence rates of the static and modal analyses, which are, in principle, identical to those of the standard FEM, for various polynomial orders of its shape functions such as quadratic, cubic and quartic orders. The proposed GFEM with quartic enrichment functions can provide more accurate solutions than the standard FEM, and thus can be effectively used at the initial design stage of high-rise wall-frame structures.Originality/valueThis work is the first paper where the GFEM is applied to the analysis of high-rise wall-frame structures, and the developed technique can be used as a good analysis tool at the initial design stage.

Modal parameter identification and damping ratio estimation from the full-scale measurements of a typical Tibetan wooden structure

Tibetan heritage buildings have a high historical and cultural value. They have endured adverse environmental loadings over hundreds of years without significant damage. However, there are few reports on their structural characteristics under normal environmental loadings and their behavior under dynamic loadings. In this research, a typical Tibetan wooden wall-frame building is selected to study its dynamic characteristics. Field measurements of the structure were conducted under environmental excitation to collect acceleration responses. The stochastic subspace identification (SSI) method was adopted to calculate the structural modal parameters and obtain the out-of-plane vibration characteristics of the slab and frames. The results indicated that the wall-frame structure had a lower out-of-plane stiffness and greater in-plane stiffness due to the presence of stone walls. Due to poor identified damping ratio estimates from the SSI method, a method based on the variance upper bound was proposed to complement the existing variance lower bound method for estimating the modal damping ratio to address the significant damping variability obtained from different points and measurements. The feasibility of the proposed method was illustrated with the measured data from the floor slab of the structure. The variance lower and upper bound methods both provided consistent results compared to those from the traditional SSI method.

Multi-objective optimization of a dissipative connection for seismic protection of wall-frame structures

This paper deals with the optimum design of a passive seismic control strategy which adopts a linear dissipative connection in a wall-frame system. The two sub-structures, the wall and the frame, respectively, are modeled as single degree of freedom systems, and are excited by a ground motion represented by a filtered non stationary stochastic process. The passive control strategy is based on a "global protection", which aims to protect both sub-structures. For this purpose, a multi-objective optimum design is formulated where two conflicting objective functions coexist: these are the displacement of the frame and the shear in the wall. In order to obtain the optimum solution in terms of Pareto set, a genetic algorithm approach—the NSGA-II—is adopted. The novelty of the proposed method is the use of a multi-dimensional criterion for the design of the dissipative connection and to consider a global seismic protection criterion. This is a very important issue in modern Technical Codes, where several performance requirements are fixed and often conflicting.

Low CO2 design approach of reinforced concrete structures for the targeted CO2 reduction

In this study, the low CO2 design process of reinforced concrete (RC) structures considering the targeted CO2 reduction was presented. The considered system boundary for each processing was presented in the ISO 13315-2. The domestic life cycle inventory database (LCI DB) was used for CO2 assessment of concrete structures. Based on the design process presented in this study, three case studies on the life cycle CO2 assessment of RC shear wall–frame structure were conducted. As the compressive strength of the column was increased from 24 to 40 MPa, the amount of CO2 emissions was increased by about 14% and the targeted CO2 reduction of 20% is not met. As substitution level of ground-granulated blast-furnace slag (GGBS) is 25%, the amount of CO2 emissions and CO2 uptake by concrete carbonation was decreased. The amount of CO2 emissions of the column and total member was decreased by 26 and 22%, respectively, compared to that of OPC. Therefore, substituting GGBS will be more effective to meet the targeted CO2 reduction ratio, rather than increasing the compressive strength of concrete.

An approach for minimum rotational response of medium-rise asymmetric structures under seismic excitations

Studied in this article is the elastic and inelastic rotational behavior of asymmetric multi-story buildings under unidirectional and bidirectional excitations in relation to the location of the modal center of rigidity. The concept of this point in mono-symmetric uniform buildings has been outlined by the author in earlier papers, and its significance lies on the property that when its location is within a close distance from the mass axis the torsional response is mitigated. At present, a generalized definition of this point is given for buildings with double eccentricity, using (1) the approach of the continuum medium and (2) the stiffness matrix methodology. To determine the location of modal center of rigidity in practical terms, a few modal quantities are required (element frequencies and effective modal masses), which may be easily obtained by commercial engineering software. To verify the aforesaid property of modal center of rigidity under unidirectional and bidirectional excitations, the rotational response of 10-story wall-frame structures is examined under the ground motions of Erzincan 1992 and Kobe 1995.

Seismic Behavior and Design of Wall–EDD–Frame Systems

Walls and frames have different deflection lines and, depending on the seismic mass they support, may often poses different natural periods. In many cases, wall-frame structures present an advantageous behavior. In these structures the walls and the frames are rigidly connected. Nevertheless, if the walls and the frames were not rigidly connected, an opportunity for an efficient passive control strategy would arise: Connecting the two systems by energy dissipation devices (EDDs) to result in wall-EDD-frame systems. This, depending on the parameters of the system, is expected to lead to an efficient energy dissipation mechanism. This paper studies the seismic behavior of wall-EDD-frame systems in the context of retrofitting existing frame structures. The controlling non-dimensional parameters of such systems are first identified. This is followed by a rigorous and extensive parametric study that reveals the pros and cons of the new system versus wall-frame systems. The effect of the controlling parameters on the behavior of the new system are analyzed and discussed. Finally, tools are given for initial design of such retrofitting schemes. These enable both choosing the most appropriate retrofitting alternative and selecting initial values for its parameters.

Reliability assessment of wall-frame structures

Abstract Assessment of the reliability of wall-frame structures using simulation based method is often prohibited by the costly and lengthily computations. The present paper introduces a response surface based technique to quickly extract the reliability and safety information. The proposed method couples the finite element (FE) model of wall-frame structure, an improved response surface scheme and the second order reliability method (SORM). At the beginning, the large number of the random variables is reduced via preliminary sensitivity analysis. Then, the failure region is reached through a repetitive strategy integrated with recommended experimental designs. The efficiency and accuracy of the scheme are verified using Monte Carlo simulation. Moreover, both serviceability and flexural limit states are used in the verification. Tens of simulations are used instead of hundreds or thousands. The method is simple, efficient and can be easily implemented. For the considered example, the lateral load and the wall stiffness are the most important variables.

Wall-Frame and Hollow Shear Wall Structural System and its Application

Wall-frame and hollow shear wall structure system is composited of Window hole wall designed wall-frame and horizontal wall designed hollow shear wall. The system is less weight and earthquake effect than the solid shear wall system, and has a good ductility. At the same time, the system has simple construction, high economic efficiency and good energy-saving emission reduction effect.

Study on Seismic Performance of a Stiffened Steel Plate Shear Wall with Slits

To determine the force mechanism for the steel plate shear wall with slits, the pushover analysis method was used in this study. An estimated equation for the lateral bearing capacity which considered the effect of edge stiffener was proposed. A simplified elastic-plastic analytical model for the stiffened steel slit wall composed of beam elements was presented, where the effects of edge stiffeners were taken into account. The wall-frame analysis model was established, and the geometric parameters were defined. Pushover analysis of two specimens was carried out, and the analysis was validated by comparing the results from the experiment, the shell element model, and a simplified model. The simplified model provided a good prediction of the lateral stiffness and the strength of the steel slit wall, with less than 10% error compared with the experimental results. The mutual effects of the bearing wall and the frame were also predicted correctly. In the end, the seismic performance evaluation of a steel slit wall-frame structure was presented. The results showed that the steel slit wall could prevent the beams and columns from being damaged by an earthquake and that the steel slit wall was an efficient energy dissipation component.

A Simplified Transfer Matrix Method for Horizontal Seismic Response of Wall-Frame Structures Considering SSI

Based on the double member model of wall-frame structure and the corresponding transfer matrix method, the concept of frequent impedance of rigid foundation is introduced so that SSI can be taken into account. This method is more convenient and efficient compared to finite element method because of fewer structural parameters and faster calculation speed. Necessary structure parameters include 7 parameters of each storey, geometry size and total mass of foundation and elastic parameters of site soil. Totally 39 examples were calculated for 13 values of foundation mass and 3 kinds of soil, which are compared to the result of fix bottom model of upper structure. Results show that SSI does not always deduce a decrease of seismic response. Sometimes SSI may increases structural displacement evidently. The simplified method would provide structure designers an efficient tool to understand seismic behavior of wall-frame structures with various foundation and site soil.