Oya Mercan

Bio: Oya Mercan is an academic researcher from University of Toronto. The author has contributed to research in topics: Damper & Tuned mass damper. The author has an hindex of 10, co-authored 36 publications receiving 378 citations.

Seismic evaluation of modular steel buildings

Abstract: Modular steel construction is a relatively new construction technique that considerably reduces the time spent on the construction site. However, due to the detailing and assembly requirements of multi-story modular steel buildings (MSBs), these systems are prone to undesirable failure mechanisms during large earthquakes. In this paper a 4-story MSB is designed considering realistic constraints posed during the modular construction. Using a detailed model in OpenSees an assessment of the seismic demand and capacity of this MSB is provided by performing nonlinear static pushover and incremental dynamic analyses (IDA) in two and three dimensions. Diaphragm interactions, relative displacements and rotations between modules, the force transfer through horizontal connections, column discontinuity coupled with possible high inelasticity concentration in vertical connections are some other important aspects that are specifically considered. The results that are summarized with relevant conclusions provide a better insight to the dynamic behavior of multi-story MSBs.

Experimental investigations of vertical post-tensioned connection for modular steel structures

Abstract: Modular construction is an off-site construction technique. In this method, structural volumetric modular components are produced in a factory and assembled on-site to form a larger, permanent building. Typical vertical connections of modular steel buildings (MSBs) are provided by on-site welding. Welding may interfere with the finishing of the modules and also when several modules are placed together at a given floor level complete access for welding is compromised. As an alternative to on-site welding, the present paper proposes a new vertical post-tensioned (PT) connection for MSBs. This connection is comprised of a post-tensioned threaded rod installed inside hollow structural sections (HSS) columns and a steel box placed between two modules. In order to evaluate the general and the seismic performance of the proposed connection, eight quasi-static cyclic loading tests were performed in T-shaped subassemblies. A combination of three different steel boxes and three initial post-tensioning loads levels were considered. Additionally, two quasi-static cyclic loading tests were performed using standard welded connections. No local buckling was observed in any of the specimens and no welding fractures occurred up to 3% drift demand. Results indicated that in comparison to the welded connection the proposed PT connection have similar lateral stiffness and strain distribution, and a higher cumulative energy dissipation capability. Therefore, the proposed connection has the potential to eliminate on-site welding in the assembly of the modules while providing the lateral resistance required.

Investigations of the application of gyro-mass dampers with various types of supplemental dampers for vibration control of building structures

Abstract: A gyro-mass damper (GMD) is an inertia-based passive control device. It has a gear assembly that amplifies the rotational inertias developed in the gears and generates a resultant resisting force that is proportional to the relative acceleration at the end terminals of the GMD. The amplification provided by the gear assembly can be adjusted by changing the gear masses or the gear ratios of the compound gears. Although similar inertia-based devices have been successfully used for vibration mitigation of motor vehicles and optical tables, there are only a few studies that investigated their application in building structures. This number is even lower for the particular type of inertial damper that has been considered in this study, i.e., GMD. Unlike other types of inertial dampers, the supplemental energy dissipation component of GMDs is not built-in to the device and can be independently attached as an external component. This allows the design engineers to use this cost-effective device and select any available energy dissipation device to use in parallel. In this study, using a small-scale GMD, by considering the rotational inertias of the intermediate gears, characteristic equation which describes the relationship between the applied relative acceleration and the resulting resisting force is derived and experimentally verified. For the introduction of GMDs into building structures, three different configurations are evaluated: (i) stand-alone GMD, (ii) GMD-brace system, and (iii) GMD–Viscous damper–Brace (GVB) system. The structure-GMD interaction, considering these three configurations, is investigated in frequency domain and in time domain through energy balance equations and time history analyses. It is shown that by selecting the system parameters properly, GVB systems with nonlinear viscous dampers can effectively improve the seismic behaviour of the structure. This is discussed in more detail when the effects of the damper nonlinearities, as well as the various GMD equivalent mass, brace stiffness, damping values and selected ground motions are investigated. The key findings related to the design, implementation and performance considerations of these systems are provided.

Experimental investigations of tuned liquid damper-structure interactions in resonance considering multiple parameters

Abstract: As structures are constructed more slender and taller, their vibrational response and its mitigation become challenging design considerations. Tuned liquid dampers (TLDs) are cost effective and low maintenance vibration absorbers that can be used to suppress structural vibrations. A TLD dissipates energy through liquid boundary layer friction, free surface contamination, and wave breaking. The dynamic characteristics of the TLD and its interaction with the structure is quite complex. In this paper, using a state-of-the-art experimental testing method, namely real-time hybrid simulation (RTHS), a comprehensive parametric study is conducted to investigate the effectiveness of TLDs. During RTHS the TLD response is obtained experimentally while the structure is modeled in a computer, thus capturing the TLD-structure interaction in real-time. By keeping the structure as the analytical model, RTHS offers a unique flexibility in which a wide range of influential parameters can be investigated without modifying the experimental setup. The parameters considered in this study with a wide range of variation include TLD/structure mass ratio, TLD/structure frequency ratio, and structural damping ratio. Additionally, the accuracy of FVM/FEM method that couples the finite volume and finite element approaches to model the liquid and solid domains to capture TLD- structure interaction is assessed experimentally. Results obtained in this study, will not only lead to a better understanding of TLDs and their interaction with the structures but also, contribute to the enhanced design of these devices which will in turn result in their wide-spread application.

Implementation and verification of real-time hybrid simulation (RTHS) using a shake table for research and education

Abstract: In this study, as a state of the art testing method, real-time hybrid simulation (RTHS) is implemented and verified with a shake table for education and research. As an application example, the dynamic behavior of a tuned liquid damper (TLD)-structure system is investigated. RTHS is a practical and economical experimental technique which complements the strengths of computer simulation with physical testing. It separates the test structure into two substructures where part of the structure for which a reliable analytical model is not available is tested physically (experimental substructure) and coupled together with the analytical model of the remaining structure (analytical substructure). The implementation of RTHS involves challenges in accurate control of the experimental substructure as well as the synchronization of the signals. The details of the hardware and the software developed and the steps taken to improve the controller are discussed in this paper so that the implementation of RTHS is proper...

New advancements, challenges and opportunities of multi-storey modular buildings – A state-of-the-art review

Abstract: Modular construction offers faster and safer manufacturing, better predictability to completion time, superior quality, less workers on site, less resource wastage, and a more environmentally friendly solution than the conventional construction process. Despite having several advantages of modular construction, the private sector still relies heavily on the traditional on-site construction method. To understand the scientific reason behind this situation, this paper critically reviews the recent developments, performances, challenges and future opportunities of modular buildings. Modular constructions are extensively used for low-rise buildings and further attracts strong interest for multi-storey building structures. Prefabricated modules demonstrated satisfactory performance under static, dynamic impact, cyclic, seismic, blast, fire and long-term sustained loading, and offer environmental, economic and social benefits. The acceptance and application of modular construction will further spread with the development of design guidelines, more skilled workers, addressing handing and transportation difficulties, and the development of novel interlocking connections between modules. Recently, composite materials demonstrated high potential to manufacture prefabricated building modules. In Australia, it is expected that modular construction will increase from the current stage of 3% to 5–10% by year 2030.

A holistic review of off-site construction literature published between 2008 and 2018

Abstract: Off-site construction (i.e., OSC) has become an emerging research domain in the recent decade. Through a three-step holistic review approach incorporating bibliometric search, scientometric analysis, and in-depth qualitative discussion, this study contributes to the body of knowledge in OSC by critically reviewing and summarizing: 1) the latest research keywords and main research topics in OSC; 2) the performance of OSC compared to that of conventional construction approach; 3) current research gaps in integrating OSC with other emerging construction concepts; and 4) future research directions in OSC. OSC is a domain that can be extended to cross-disciplinary research from the perspectives of engineering, management, and technology. Existing research have been focusing on many research disciplines, such as structural behaviors and joint connections of prefabricated components, scheduling and planning of off-site activities, as well as performance evaluation of OSC. However, further research is needed in integrating the emerging digital construction technology, integrated project delivery method, lean construction, and issues of sustainability of OSC. There are still limited studies linking OSC to the concept of Design for Manufacturing and Assembly. Future research should also adopt a larger database and allow for comprehensive evaluation of OSC performance.

Structural response of modular buildings – An overview

Abstract: Prefabrication by off-site manufacturing leads to a reduced overall construction schedule, improved quality, and reduced resource wastage. Modular building is therefore increasingly popular and promoted. With the recent promotion a number of relevant studies have been completed, however, a review of the design, construction, and performance of modular buildings under different loading conditions is lacking. This paper presents a state-of-the-art review of modular building structures. First, structural forms and construction materials are presented as a brief introduction to the modular structures. Modular building is shown to refer not to a single structure type, but a variety of structural systems and materials. These modular structures might perform differently to similar traditional structures and the structural performance is highly dependent on inter- and intra-module connections. The structural response of modules to different hazards is then considered, followed by the current design practice and methodology. As a currently developing area there is great potential for innovation in modular structures and several key research areas are identified for further work.

Experimental study on interior connections in modular steel buildings

Abstract: In modular steel buildings, traditional architectures are separated into prefabricated room-sized volumetric units that are manufactured offsite and installed onsite. The connections between the modules are important for load transfer. Conventional inter-module connections mainly use direct plates and connect them using bolts; however, this may prove problematic for the inner connecting regions. A new type of design with beam-to-beam bolted connections is proposed in this paper; this design provides easy working access without being affected by the structural members. The static performance, hysteretic performance, skeleton curves, ductile performance, energy dissipation capacity, and stiffness degradation patterns of the joints are obtained by experiments and finite element analyses. The results showed that because of the construction between two unit joints, gaps would be formed between the upper and bottom columns, and this gap can influence the deformation patterns and distribution of bending loads at each unit joint. The weld quality at the unit joints is critical to ensure overall safety. Stiffeners can effectively increase the stiffness and load bearing capacity, but may reduce ductility performance. The deforming ability of the connection is also closely influenced by the stiffness of the floor beam column joint and ceiling beam column joint and their relative intermediate magnitudes.