Frame Dual Systems Research Articles

Improved lumped parameter model for shear wall–frame structures with geometric and material nonlinearities

Lumped parameter macroscopic structural models, such as those consisting of springs and rigid sticks, are useful for parametric studies and probabilistic analyses of individual building structures as well as for regional-level assessments on building stock. The existing lumped parameter models (LPMs) for shear wall–frame dual systems exhibit some drawbacks. There is a discrepancy in their arrangement of springs. They are calibrated to match only two modal periods of the original multi-story or even high-rise building structure. The existing models also have limitations when confronted with the P-Δ effect. After a careful investigation, this paper developed new schemes of spring-stick assemblies that accurately reproduce the elastic stiffness matrix of a two-dimensional Euler–Bernoulli or Timoshenko beam–column element and cope with geometric and material nonlinearities. The developed assemblies, which are essentially lumped parameter substitutes for beam–column elements, can be used to build LPMs for moment frames and shear walls. For moment frames, the traditional fishbone model is converted into a LPM that not only reflects the beam-to-column stiffness ratio and strength ratio but also captures the P-Δ effect. Combining the LPM for shear wall with the lumped parameter fishbone model results in an improved LPM for wall–frame dual systems. Together with lumped floor masses, the improved LPM is able to accurately predict all the global vibration modes and nonlinear seismic responses of a dual system. The proposed LPM possesses distinct advantages when simplified macroscopic models are preferred for building structures.

Ductility-related seismic modification factor for CLT shear-wall and glulam moment-resisting frame dual system

The cross-laminated timber (CLT) shear-wall and glulam moment-resisting frame (CLTW–GMRF) dual system is a recently completed research prepared for the British Columbia (BC) Forestry Innovation Investment Ltd. With the introduction of new structural systems, the need to update existing building code becomes evident. Accordingly, this study evaluates the ductility-related force modification factor ( Rd) of the CLTW–GMRF system for the National Building Code of Canada, utilizing the FEMA P-695 procedure. In two performance groups, 16 archetype buildings are designed considering different building storey heights, CLT shear-wall locations, and wall-frame moment proportions. Numerical model of the systems is developed in OpenSees and incremental dynamic analyses are conducted using 30 bi-directional ground motion records that represent the seismicity of Vancouver, BC, Canada. Collapse margin ratios are calculated to assess the adequacy of the trial Rd factors. The research determined that with an over-strength factor of 1.5, an Rd of 3 is found to be acceptable for the system.

Investigating the seismic performance of MRF-CBF dual systems under the effects of staged construction

In steel structures with moment-resisting frame-concentrically braced frame dual systems, as the moment-resisting frame can individually withstand gravity and seismic loads during construction, the braces can be installed on a story-by-story basis simultaneous with the installation of the moment frame or after its complete construction. This issue cannot be investigated and studied using ordinary analysis, where it is assumed that the entire structure is built at once, and then all the involved loads are applied to the completed structure. Accordingly, this research investigated the effects of staged construction in the mentioned dual systems with V, inverted-V (Chevron), and split-X braces. In this regard, three-dimensional models with 5, 10, 15, 20, and 25 stories incorporating these systems were generated and subjected to pushover analysis under cyclic loading protocols. From the results, it was concluded that staged construction could lead to maximum increases of 19.6% in the axial forces in internal columns due to dead load, 9.3% in the displacement corresponding to the first plastic hinge formation, 13.3% in the base shear corresponding to the first plastic hinge formation, 22.9% in the ultimate lateral strength, and 4.6% in the effective lateral stiffness. Also, staged construction was not found to significantly affect the axial forces in corner and braced-bay columns due to dead load and the energy dissipation under cyclic loading protocols.

Analysis of Effective Location of Shear Wall for High Rise Building with U – Configuration

Indonesia is one of the countries that is prone to earthquakes. In addition to the dead loads, superimposed dead loads, and live loads, the design of buildings in Indonesia must be concerned with earthquake loads. Installing shear walls in the building structure as the Special Moment Frame Dual System is one of a solution to withstand earthquake loads. However, the location of shear walls must be considered, especially in buildings with horizontal irregularities. This study aims to determine the optimum location of the shear walls in a 10-storey building that has U-configuration with dynamic earthquake loads. This research is a numerical simulation ran by modelling the structure with software. To know the effect of the shear wall’s location on a building, several variations of the shear wall configuration with different positions have been conducted. It can be seen the lateral displacement of each floor and the shear force are the response structure to withstand the dynamic earthquake loads. Shear walls that are located close to the center of mass of the building are the optimum variation because the position of the shear wall is the closest to the core area of the building, which is the rotational axis of the building.

Shear Wall and Frame Dual Systems Featuring Discontinuous Load Paths in Frame Elements in Low-to-Moderate Seismic Regions

ABSTRACT Reinforced concrete buildings constitute a significant portion of construction in Australia. Many existing buildings in Australia and other low to moderate seismic regions have been designed with little to no consideration for ductile detailing. The majority of these buildings also possess vertical irregularities, which can exacerbate their vulnerability in an earthquake event. The seismic performance of shear wall and frame dual systems possessing discontinuities in frame elements in the form of ductility and failure mechanism has been assessed. And design recommendations in terms of response modification factors and designation of appropriate methods of analysis have been provided.

Optimum design of steel braced frames considering dynamic soil-structure interaction

Recent studies on design optimization of steel frames considering soil-structure interaction have focused on static loading scenarios, and limited work has been conducted to address the design optimization under dynamic soil-structure interaction. In the present work, first, a platform is developed to perform optimization of steel frames under seismic loading considering dynamic soil-structure interaction (SSI) in order to quantify the effects of earthquake records on the optimum design. Next, verification of the adopted modeling technique is conducted using comparison of the results with the reference solution counterparts in frequency domain. For time history analyses, records from past events are selected and scaled to a target spectrum using simple scaling approach as well as spectrum matching technique. For sizing of the steel frames, a recently developed metaheuristic optimization algorithm, namely exponential big bang-big crunch optimization method, is employed. To alleviate the computational burden of the optimization process, the metaheuristic algorithm is integrated with the so-called upper bound strategy. Effects of factors such as the building height, presence of soil domain, and the utilized ground motion scaling technique are investigated and discussed. The numerical results obtained based on 5- and 10-story steel braced frame dual systems reveal that, although dynamic SSI reduced the seismic demands to some extent, given the final design pertains to different load combinations, the optimum weight difference is not considerable.

Improving seismic behaviour of core walls of dual structural systems using multi-plastic hinges

This paper studies the implication of the development of shear wall plastic hinges in high-rise dual systems. Multi-plastic hinge approach is intended to reduce the effects of higher modes of vibration in tall structural walls under earthquakes. This research investigated analytically the seismic response of three code conforming designed buildings with 16, 27 and 45 stories. These buildings which consist of a core wall/special moment frame dual system are modeled with four different approaches with single, dual, three and four plastic hinges, and some main structural responses including moment and shear distribution and values, drift ratio distribution and values, floor accelerations, contribution of frame in dual system and finally energy dissipation among plastic hinges are assessed. Findings of this research show that the application of multi-plastic hinge approach in wall design can properly affect seismic behavior of core walls and leads to improvement of system seismic capacity and economy of design. The investigation also shows that the application of multi-plastic hinge design concept can cause better use of frame nonlinear deformation capacity which would help better control of effects of higher modes. Based on analyses results, more frame contribution and improvement of wall behavior is observable in models with three and four plastic hinged walls in comparison with single plastic hinge model designed based on ACI 318-14 provisions.

Seismic performance of stiffness-based designed buckling-restrained braced frame and special moment-resisting frame dual systems

Conventional procedure for designing dual systems, proposed in seismic regulations, encompasses some limitations such as not putting a required minimum stiffness value for the secondary system. This research investigates the stiffness limit value required for the secondary system for designing buckling-restrained braced frame (BRBF) and special moment-resisting frame (SMRF) dual systems. Non-linear static and time history analyses were carried out on the sample dual structures with different heights and different relative stiffness ratios of the primary system to the secondary system. A stiffness-based designing approach is employed to ensure that the designed system comprises the predefined relative stiffness ratios. It is demonstrated that the suitable stiffness combination ratio is gained when the BRBF and SMRF subsystems have 65% and 35% of the total stiffness, respectively. Implementation of the suitable relative stiffness ratio in the dual systems designed according to the presented approach, leads to a uniform plasticity profile in the height of structures.

Analytical investigation of response modification (behaviour) factor, R, for reinforced concrete frames rehabilitated by steel chevron bracing

Steel bracing of reinforced concrete (RC) frames has received noticeable attention in recent years as a retrofitting measure to increase the shear capacity of the existing RC buildings. In order to evaluate the seismic behaviour of steel-braced RC frames, some key response parameters, including the ductility and the overstrength factors, should first be determined. These two parameters are incorporated in structural design through a force reduction or a response modification factor. In this paper, the ductility and the overstrength factors as well as the response modification factor (or seismic behaviour factor) for steel chevron-braced RC frames have been evaluated by performing inelastic pushover analyses of brace-frame systems of different heights and configurations. The effects of some parameters influencing the value of behaviour factor, including the height of the frame and share of bracing system from the applied lateral load have been investigated. It is found that the latter parameter has a more localised effect on the R values and its influence does not warrant generalisation at this stage. However, the height of this type of lateral load-resisting system has a profound effect on the R factor, as it directly affects the ductility capacity of the dual system. Finally, based on the findings presented in the article, tentative R values have been proposed for steel chevron-braced moment-resisting RC frame dual systems for different ductility demands and compared with different type of bracing systems.

Seismic behaviour factor, R, for steel X-braced and knee-braced RC buildings

The seismic behaviour factor ( R) is evaluated for steel X-braced and knee-braced RC buildings. The R factor components including ductility reduction factor and overstrength factor are extracted from inelastic pushover analyses of brace-frame systems of different heights and configurations. The effects of some parameters influencing the value of R factor, including the height of the frame, share of bracing system from the applied load and the type of bracing system are investigated. It is found that the two latter parameters have a more localised effect on the R values and their influence does not warrant generalisation at this stage. However, the height of this type of lateral load-resisting system has a profound effect on the R factor, as it directly affects the ductility capacity of the dual system. Finally, based on the findings presented in the article, tentative R values are proposed for steel-braced moment-resisting RC frame dual systems for different ductility demands.

An estimation of displacement limits for ductile systems

AbstractTo enable acceptable seismic displacement demands to be specified, the displacement capacity of a structural system needs to be known. This is controlled by selected performance criteria. It is postulated that the assignment of fractions of the required strength of the system to its components may be arbitrary. This then enables the displacement capacity of buildings to be evaluated without the knowledge of its seismic strength. A redefinition of some traditionally used structural properties is a prerequisite to applications. The study of a reinforced concrete wall–frame dual system illustrates rationale and extreme simplicity of application. Copyright © 2001 John Wiley & Sons, Ltd.