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Solid design and craftsmanship are a necessity for structures and infrastructures that must stand up to natural disasters on a regular basis. Continuous research developments in the engineering field are imperative for sustaining buildings against the threat of earthquakes and other natural disasters. Performance-Based Seismic Design of Concrete Structures and Infrastructures is an informative reference source on all the latest trends and emerging data associated with structural design. Highlighting key topics such as seismic assessments, shear wall structures, and infrastructure resilience, this is an ideal resource for all academicians, students, professionals, and researchers that are seeking new knowledge on the best methods and techniques for designing solid structural designs.
Traditional concentrically braced frames, CBF, are stiff and provide limited to moderate ductility, while moment resisting frames, MRF, are able to dissipate seismic energy when undergoing large lateral displacements. However, these traditional earthquake resistant systems do not show uniformly distributed damage along the building height. Changes in structural proprieties during nonlinear hysteresis behaviour may lead to drift concentration and weak-storey response. Moreover, both traditional systems are susceptible to long-duration subduction earthquakes. The pursuit of these issues led to the concept of utilizing multiple-resisting structural systems that act progressively so that the overall seismic resistance is not significantly reduced during long-duration earthquakes. The structural system consisting of a rigid braced frame that provides primary stable cyclic behavior and a moment frame acting as a backup system with good flexural behavior is the steel Braced Dual System studied herein. The objectives of this study are: a) to investigate the seismic response of steel Braced Dual building from yielding to failure, as well as, to identify the types of failure mechanism; b) to assess the seismic response of Braced Dual System against the traditional MRFs and CBFs with moderate ductility through incremental dynamic analysis; c) to evaluate the effect of long duration subduction earthquakes versus crustal type earthquakes on these building systems through collapse safety criteria using FEMA P695 procedure and to assess the probability of exceeding defined performance levels using fragility analysis. To carry out these objectives, detail numerical models were developed using the OpenSees framework. The prototype 8-storey office building is located on firm soil in Vancouver, B.C. and is subjected to two sets of crustal and subduction ground motions. Two traditional earthquake resistant systems (MD-CBF, MD-MRF) and the Braced Dual System are considered. Design is conducted according to NBCC2015 and CSA/S16-14. From nonlinear time history analysis, the following results are reported: for the Braced Dual System, two types of failure mechanism involving either one floor or two adjacent floors (in general the bottom floors) were identified which also involve flexural yielding of MRF beam of critical floors; the Braced Dual System provides larger ductility than the MD-CBF, shows significant increase of seismic resistant capacity for similar seismic demands, provides the largest collapse margin ratio and collapse safety capacity under both earthquake types. In addition, the building with Braced Dual System shows a progressive seismic behavior and a more uniform damage distribution along the building height. From fragility analysis resulted that at Collapse Prevention (CP) limit state, the Braced Dual System experiences 100% probability of exceedance after it was subjected to two times larger seismic demand than the MD-CBF or MD-MRF systems. All studied structural systems are sensitive to long duration subduction earthquake.
Performance-Based Seismic Design (PBSD) is a structural design methodology that has become more common in urban centers around the world, particularly for the design of high-rise buildings. The primary benefit of PBSD is that it substantiates exceptions to prescribed code requirements, such as height limits applied to specific structural systems, and allows project teams to demonstrate higher performance levels for structures during a seismic event.However, the methodology also involves significantly more effort in the analysis and design stages, with verification of building performance required at multiple seismic demand levels using Nonlinear Response History Analysis (NRHA). The design process also requires substantial knowledge of overall building performance and analytical modeling, in order to proportion and detail structural systems to meet specific performance objectives.This CTBUH Technical Guide provides structural engineers, developers, and contractors with a general understanding of the PBSD process by presenting case studies that demonstrate the issues commonly encountered when using the methodology, along with their corresponding solutions. The guide also provides references to the latest industry guidelines, as applied in the western United States, with the goal of disseminating these methods to an international audience for the advancement and expansion of PBSD principles worldwide.
Concentrically braced frames (CBFs) have been one of the fundamental structural systems for lateral force resistance chosen by designers for low-rise steel construction since the early part of the twentieth century. CBFs designed using the building codes and standards of the 1960s were designed using the principle that they remained in the linearly elastic range. The current design philosophy of the 2010 National Building Code of Canada (NBCC) and CSA-S16-09 is based on the principles of capacity design and recognises the cyclic inelastic behaviour of CBFs. Since no detailing or design requirements for an inelastic seismic response were included in structures designed with past building codes, these structures are likely to exhibit seismic deficiences, including lack of lateral resistance and insufficient ductility. Guidelines for evaluating the performance of CBFs are required in order to provide recommendations for seismic evaluation and rehabilitation for such existing buildings for future building codes. The behaviour of one-storey steel structures built with the 1965 National Building Code of Canada (NRCC 1965) and CSA-S16-65 (CSA 1965) under current building code standards for seismic design was studied in order to aid in establishing such guidelines. The response of a series of sixteen one-storey buildings with varying aspect ratios and heights was studied, subjected to ten artificial and ten historical earthquake ground motions. The nonlinear seismic behaviour of the CBFs was determined using an analytic Open Sees, Open System for Earthquake Engineering Simulatuion (OpenSees 201), model for nonlinear time history dynamic analysis, including drift and ductility demands on the braces. The intended performance level in the design earthquakes, as well as the acceptance criteria used in the braced frame analysis were established using FEMA P695 (FEMA 2009) criteria. In general, although acceptable performance was not acheived in all cases, the one-storey stee structures built with the 1965 National Building Code of Canada, on average, performed well, for the seven failure criteria outlined in this study.
Seismic design of multi-story buildings requires capacity design principles that allow for distributed damage (plastic member deformations) to occur over the building height while preventing soft-story failure mechanisms that may lead to collapse. Seismic evaluation of steel concentrically braced frame (CBF) buildings has revealed that they exhibit soft-story behavior due to non-uniform brace degradation and non-ductile failure modes. This research proposes a rehabilitative design procedure for existing buildings that uses a stiff rocking core to redistribute plastic deformations along the structure’s height. Additionally, an improved design procedure for braced frame columns is proposed for new frame design. Several representative frames were designed and evaluated using nonlinear transient seismic finite element analysis and large-scale hybrid experimental testing. Predicted, analytical, and experimental response results show reasonable agreement, and the proposed techniques are believed to be reliable for achieving desirable seismic performance in low- to mid-rise steel braced frame structures.
This volume highlights the latest advances, innovations, and applications in the field of seismic design and performance of steel structures, as presented by leading international researchers and engineers at the 10th International Conference on the Behaviour of Steel Structures in Seismic Areas (STESSA), held in Timisoara, Romania, on 25-27 May 2022. It covers a diverse range of topics such as behaviour of structural members and connections, performance of structural systems, mixed and composite structures, energy dissipation systems, self-centring and low-damage systems, assessment and retrofitting, codes and standards, light-gauge systems. The contributions, which were selected by means of a rigorous international peer-review process, present a wealth of exciting ideas that will open novel research directions and foster multidisciplinary collaboration among different specialists.