Nonlinear Seismic Design of Multistory Frames

1975 ◽  
Vol 2 (4) ◽  
pp. 494-516 ◽  
Author(s):  
V. V. Bertero ◽  
H. Kamil
Keyword(s):  
Optimum Design ◽  
Seismic Design ◽  
Computer Aided Design ◽  
Linear Optimization ◽  
Design Procedure ◽  
Optimization Procedure ◽  
Preliminary Design ◽  
Displacement Ductility ◽  
Final Design ◽  
Design Earthquake

A five-step, computer-aided design procedure representing a significant change from current seismic design practices is proposed.In the first step, the ‘design earthquake’ and the safety and serviceability criteria are established, and appropriate values of a damping coefficient and displacement ductility factor are assumed. An iterative preliminary analysis procedure, centered around specified values of a seismic coefficient and a drift index, is used to determine the design story shears using modal analysis.Then, a preliminary design is carried out using a simplified story-wise optimization procedure. This is followed by inelastic static and dynamic analyses of the design. The maximum values of story shears and ductilities and their overall pattern, so obtained, are compared against those used initially. The procedure is repeated until a satisfactory agreement is obtained and the final design story shears are determined. In the fourth step, these shears are used to attain the final optimum design through a procedure similar to that used in the preliminary design, but using an improved story subassemblage and a more formal linear optimization technique.Finally, the reliability of the optimum design is evaluated by determining its nonlinear response to severe earthquakes and its serviceability. The design procedure is demonstrated on a 10-story 3-bay frame.

Preliminary Design of Small-Scale Supercritical CO2 Radial Inflow Turbines

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Tina Unglaube ◽  
Hsiao-Wei D. Chiang
Keyword(s):  
Optimum Design ◽  
Supercritical Co2 ◽  
Velocity Ratio ◽  
Design Procedure ◽  
Expansion Ratio ◽  
Maximum Efficiency ◽  
Design Parameters ◽  
Small Scale ◽  
Preliminary Design ◽  
Line Design

Abstract In recent years, supercritical CO2 (sCO2) Brayton cycles have drawn the attention of researchers due to their high cycle efficiencies, compact turbomachinery, and environmental friendliness. For small-scale cycles, radial inflow turbines (RIT) are the prevailing choice and one of the key components. A mean line design procedure for sCO2 RIT is developed and design space exploration conducted for a 100 kW-class turbine for a low-temperature waste-heat utilization sCO2 Brayton cycle. By varying the two design parameters, specific speed and velocity ratio, different turbine configurations are setup and compared numerically by means of computational fluid dynamics (CFD) simulations. Results are analyzed to conclude on optimum design parameters with regard to turbine efficiency and expansion ratio. Specific speeds between 0.2 and 0.5 are recommended for sCO2 RIT with small though flow (3 kg/s). The higher the velocity ratio, the bigger the turbine expansion ratio. Pairs of optimum design parameters that effectuate maximum efficiency are identified, with smaller velocity ratios prevailing for smaller specific speeds. The turbine simulation results for sCO2 are compared to well-established recommendations for the design of RIT from literature, such as the Balje diagram. It is concluded that for the design of sCO2 RITs, the same principles can be used as for those for air turbines. By achieving total-to-static stage and rotor efficiencies of 84% and 86%, respectively, the developed mean line design procedure has proven to be an effective and easily applicable tool for the preliminary design of small-scale sCO2 RIT.

SEISMIC DESIGN OF FRAME STRUCTURES EQUIPPED WITH INNOVATIVE HYSTERETIC DISSIPATIVE DEVICES

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Michele Palermo ◽  
Vittoria Laghi ◽  
Stefano Silvestri ◽  
Giada Gasparini ◽  
Tomaso Trombetti
Keyword(s):  
Seismic Design ◽  
Design Procedure ◽  
Structural Instability ◽  
Hysteretic Behavior ◽  
Frame Structure ◽  
Frame Structures ◽  
Order Effects ◽  
Final Design ◽  
Structural Engineer ◽  
Performance Based Seismic Design

In the present work, a Performance-Based Seismic Design procedure applied to multi-storey frame structures with innovative hysteretic diagonal steel devices (called Crescent Shaped Braces or CSB) is introduced. CSBs are steel elements of peculiar geometrical shapes that can be adopted in frame buildings as enhanced hysteretic diagonal braces. Based on their "boomerang" configuration and placement inside the frame structure, they are characterized by a lateral stiffness uncoupled from the yield strength and, if properly inserted, by an overall symmetric hysteretic behavior with hardening response at large drifts, thus preventing from global structural instability due to second-order effects. The procedure here presented is intended to guide the structural engineer through all the steps of the design process, from the selection of the performance objectives to the preliminary sizing of the CSB devices, up to the final design configuration. The steps are described in detail through the development of an applicative example.

Performance-Based Seismic Design Approach for High Speed Railway Bridge

2011 ◽  
Vol 383-390 ◽  
pp. 6601-6607
Author(s):  
Xing Chong Chen ◽  
Xiu Shen Xia ◽  
Li Li Xing
Keyword(s):  
Seismic Design ◽  
High Speed ◽  
Design Procedure ◽  
Reduction Factor ◽  
Railway Bridge ◽  
Strength Reduction Factor ◽  
Maximum Displacement ◽  
High Speed Railway ◽  
Displacement Ductility ◽  
Performance Based Seismic Design

Performance objectives and contents of resistance verification for high speed railway bridge are embodied and quantified based on the theory of performance-based seismic design. The resistance verification is proposed, which can control the damage under design earthquake and ensure safety of the pier under low-level earthquake. The simplified capacity spectra method for calculating displacement ductility factor is proposed by using strength reduction factor. The method for evaluating damage of RC bridge pier in high-level earthquake is presented by using maximum displacement and hysteretic energy. The proposed approach and procedures for performance-based seismic design are easily to implement. The performance-based seismic design procedure is demonstrated by using an example.

scholarly journals Direct displacement-based seismic design of concrete buildings

2000 ◽  
Vol 33 (4) ◽  
pp. 421-444 ◽  
Author(s):  
M.J.N. Priestley ◽  
M.J. Kowalsky
Keyword(s):  
Seismic Design ◽  
Design Procedure ◽  
Time History ◽  
Initial Stiffness ◽  
Concrete Buildings ◽  
History Analysis ◽  
Starting Point ◽  
Displacement Profile ◽  
Displacement Based ◽  
Design Earthquake

A seismic design procedure is developed to enable concrete buildings to be designed to achieve a specified acceptable level of damage under the design earthquake. The acceptable limit is defined as a displacement profile related to limit material strains or code specified drift limits. In this procedure, the elastic properties, including initial stiffness, strength and period, are the end product of the design rather than the starting point. It is shown that the procedure is simple to apply, and results in significant differences from the more conventional force-based procedure. Designs for multi-storey frame and wall buildings are presented, and target displacements are compared with results from inelastic time-history analysis.

A Reliability-Based Dual Level Seismic Design Procedure for Building Structures

1995 ◽  
Vol 11 (3) ◽  
pp. 417-429 ◽  
Author(s):  
Kevin R. Collins
Keyword(s):  
Seismic Design ◽  
Design Procedure ◽  
Response Spectra ◽  
The United States ◽  
Complex Problem ◽  
Building Structures ◽  
Inelastic Behavior ◽  
Earthquake Excitation ◽  
Final Design ◽  
Hazard Response

structural design, Limit design, Spectra The seismic design provisions of most building codes in the United States specify ground motion parameters for various regions of the country and provide simple formulas to determine a distribution of lateral forces for which the structure should be designed. The simple formulas typically involve the use of one or more “factors” to account for anticipated inelastic behavior of the structure, relative importance of the structure, and site soil effects. Although these code provisions are very simple to use, they oversimplify a complex problem and are based on many implicit assumptions which many designers may not appreciate. Furthermore, the reliability of the final design is not known. This paper describes the key features of an alternative seismic design procedure in which the underlying assumptions are more clearly defined and which provides a more uniform level of reliability in the final design. The procedure requires the designer to consider two levels of earthquake excitation. An “equivalent” single-degree-of-freedom model and uniform hazard response spectra are used to predict structural performance. The alternative procedure should enable designers to achieve code-specified target performance objectives for moderate and severe levels of earthquake excitation.

scholarly journals A modal seismic design procedure based on a selected level of ductility demand

2019 ◽  
Vol 52 (2) ◽  
pp. 78-94 ◽  
Author(s):  
Milad Farahanchi Baradaran ◽  
Farhad Behnamfar
Keyword(s):  
Seismic Design ◽  
Design Procedure ◽  
Structural Systems ◽  
Code Design ◽  
Vibration Modes ◽  
Ductility Demand ◽  
Final Design ◽  
Ductility Capacity ◽  
Different Levels

Determination of seismic design forces of structures is performed by the building codes usually using response reduction (or behaviour) factors that incorporate indeterminacy and ductility capacity of lateral bearing systems. In this procedure story drifts are checked as a final design step approximately preventing stories from assuming excessive ductility demands, or seismic damage. If this procedure is reversed, a more logical seismic design approach may be developed by starting with a ductility-controlled procedure. It is the incentive of this research in which by using a large number of earthquakes, first nonlinear acceleration spectra are developed for different levels of ductility demand. Then an energy-based modal procedure is developed in which the system ductility demand is distributed between the important vibration modes based on their contribution. Finally, the developed method is applied to seismic design of several buildings selected from both regular and irregular structural systems. Comparison with a sample code design establishes success of the method in developing a more rational seismic design.

A Displacement-Focused Seismic Design of Mixed Building Systems

2002 ◽  
Vol 18 (4) ◽  
pp. 689-718 ◽  
Author(s):  
Tom Paulay
Keyword(s):  
Reinforced Concrete ◽  
Seismic Design ◽  
Preliminary Design ◽  
Design Strategies ◽  
Displacement Ductility ◽  
Building Systems ◽  
Concrete Building ◽  
Displacement Based ◽  
Mixed Systems ◽  
Prediction Of Displacements

A postulated prediction of displacements in ductile reinforced concrete building systems is based on a redefinition of basic structural properties. Contrary to the ability of traditional techniques, the proposed approach permits displacement limits, relevant to ductile mixed systems, i.e., those with markedly differing components, to be established before details, such as strengths, are addressed. This should lead to significant benefits at the stage of preliminary design. Acceptable displacement limits, associated with currently introduced direct displacement-based seismic design strategies, can be readily and simply established. Similarly, limits of displacement ductility demands on components and the system, associated with current force-based approaches, can be estimated already as part of the preliminary design.

A proposed strategy for seismic design of steel buildings

1999 ◽  
Vol 26 (5) ◽  
pp. 564-571
Author(s):  
DJL Kennedy ◽  
M S Medhekar
Keyword(s):  
Seismic Design ◽  
Limit State ◽  
Evaluation Criteria ◽  
Design Procedure ◽  
Ultimate Limit State ◽  
Seismic Zone ◽  
Steel Buildings ◽  
Limit States ◽  
Design Earthquake ◽  
Ultimate Limit

The conceptual basis of the seismic design procedure in the National Building Code of Canada is reviewed. The design earthquake is specified only for the ultimate limit states at which the performance of both ordinary and important buildings is evaluated by an elastic static analysis in all zones. Criteria for checking the serviceability limit states, which apply to moderate earthquakes that may occur relatively frequently in the life of the building, are not specified explicitly. It is suggested that the current design approach could be improved by adopting a design strategy that addresses as well the serviceability limit states and associated evaluation criteria and gives methods for design and analysis as a function of the seismic zone and the importance of the structure. An earthquake with a return period of 1 in 50 years is proposed tentatively for the serviceability limit states with appropriate drift limits. The proposed serviceability limit states are shown to govern the design of buildings for values of the force modification factor greater, on average, than 3.Key words: analyses, earthquake, seismic design, serviceability limit state, steel, ultimate limit state.

A MATLAB Code for Integrated Additive Manufacturing and Level-Set Based Topology Optimization

2016 ◽  
Author(s):  
Panagiotis Vogiatzis ◽  
Shikui Chen ◽  
Chi Zhou
Keyword(s):  
Topology Optimization ◽  
3D Printing ◽  
Level Set ◽  
Design Procedure ◽  
Optimization Procedure ◽  
Optimization Method ◽  
Matlab Code ◽  
Level Set Function ◽  
Final Design ◽  
3D Printers

Since topology optimization has become an important part of the design procedure, various optimization methods have been developed through the years. One of the promising options is the use of level-set based topology optimization method. In this method, the design is the zero level of a one higher dimension level-set function Φ. The benefit of this alternative method is that the final design is characterized by its clear boundaries. This advantage is based on the fact that post-processing work is not needed on the final design and it can be directly sent to the manufacturing line. The designers, in order to visualize their innovative results, often build prototypes using 3D printers, given that the designs may have complicated features. Furthermore, cost permitting, 3D printing can also be considered for mass customization. Either way, the result of the optimization has to be translated to a file that 3D printers can recognize. In this paper, the authors have developed a MATLAB code that can be integrated in the topology optimization procedure and convert the design to an STL file (STereoLithography), which is the de facto format for 3D printing.

Drift-based seismic design procedure for Buckling Restrained Braced Frames

Structures ◽  
2021 ◽  
Vol 30 ◽  
pp. 62-74
Author(s):  
Seyed Amin Mousavi ◽  
Seyed Mehdi Zahrai ◽  
Ali Akhlagh Pasand
Keyword(s):  
Seismic Design ◽  
Design Procedure ◽  
Braced Frames ◽  
Buckling Restrained Braced Frames
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