scholarly journals Evaluating the Behaviour Factor of Medium Ductile SMRF Structures

2017 ◽  
Author(s):  
Djamal Yahmi ◽  
Taïeb Branci ◽  
Abdelhamid Bouchaïr ◽  
Eric Fournely
Keyword(s):  
Limit State ◽  
Pushover Analysis ◽  
Design Procedure ◽  
Ultimate Limit State ◽  
Eurocode 8 ◽  
Q Factor ◽  
Local Response ◽  
Base Shear ◽  
Behaviour Factor ◽  
Steel Moment Resisting Frames

In seismic codes, the capacity of structures is calculated using capacity design procedure based on the concept of base shear. The critical parameter in this procedure is the behaviour factor (q-factor), which allows designing the structures at the ultimate limit state accounting for their ductility and reserve strength. In this paper, the q-factor is evaluated for medium ductile steel moment-resisting frames (SMRF) using pushover analysis. The influence of specific parameters, such as the stories number, the “Column/Beam” capacity and the local response of structural members, is studied. The results show that the most important parameter that affects the q-factor is the local response of first-storey columns, while the “Column/Beam” capacity has a less effect on this factor. Furthermore, it is observed that the q-factor value assigned to the studied frames in Eurocode-8 is systematically underestimated for low-rise frame, while the use of this value for high-rise frame is potentially unsafe.

Ductility Enhancement in Reinforced Concrete Structure with Buckling Restrained Braced Frames

2016 ◽  
Vol 847 ◽  
pp. 281-289
Author(s):  
Erkan Senol ◽  
Ismail Kose ◽  
Bilge Doran ◽  
Pelin Elif Mezrea ◽  
Bulent Akbas
Keyword(s):  
Reinforced Concrete ◽  
Pushover Analysis ◽  
Design Procedure ◽  
Braced Frames ◽  
Base Shear ◽  
Moment Frames ◽  
Concentrically Braced Frames ◽  
Capacity Curve ◽  
Concentrically Braced ◽  
Buckling Restrained Braced Frames

Adding braces to moment frames is considered to be quite an efficient technique for increasing the global stiffness and strength of the structure. It has not only been used in steel moment frames, but also in reinforced concrete (RC) moment frames in recent years. It certainly can increase the energy absorption capacity of structures and also decrease the demand imposed by seismic ground motions. Steel braces are anchored firmly to boundary beams and columns. They are modeled as truss elements and increase earthquake resistance of the building. Buckling restrained braced frames (BRBFs) in which members yield under both tension and compression without significant buckling have been used in recent years in order to ensure the desired seismic performance of special concentrically braced frames. BRBFs are similar to the special concentrically braced frames in that seismic accelerations are resisted by a building-frame members and diagonal braces whereas the design procedure is different. BRBs should be designed to permit ductile yielding both in compression and tension. In this paper, flat-slab RC building with two different configurations of buckling restraint braces (BRBs) is studied. The buildings have 4-storey with 5 bays in both X-and Y-directions and have been designed according to Turkish Specification of Reinforced Concrete Design (TS 500). In order to explore overall behavior up to failure and lateral load resisting capacities for these buildings, nonlinear static analyses have then been performed using SAP 2000-V14.1. Pushover analysis under constant gravity loads and monotonically increasing lateral forces during an earthquake until a target displacement is reached is generally carried out as an effective tool for performance based design. The major outcome of a pushover analysis is the capacity curve which shows the base shear vs. the roof displacement relationship and represents the overall performance of the building. The results of the analyses are presented in terms of capacity curve and energy dissipation.

An Evaluation of Two-Level Seismic Design Procedure

1993 ◽  
Vol 9 (1) ◽  
pp. 121-135 ◽  
Author(s):  
Chia-Ming Uang
Keyword(s):  
Structural Damage ◽  
Limit State ◽  
Design Procedure ◽  
Reduction Factor ◽  
Performance Criteria ◽  
Ultimate Limit State ◽  
Seismic Codes ◽  
Seismic Force ◽  
Force Reduction Factor ◽  
Force Reduction

The two-level design philosophy is recognized by modern seismic codes. When this philosophy is implemented in the code, the intensities of the two design earthquakes, the structural performance criteria, explicit versus implicit design approach, and the effectiveness to achieve the performance criteria vary considerably from one code to the other. For the ultimate limit state, the UBC was compared with seismic codes of Canada, Japan, and Eurocode. It was found that a trend to deviate from the UBC approach of using a single seismic force reduction factor (i.e., Rw) is apparent. Instead, an approach using a compound force reduction factor which considers the contribution of structural ductility and structural overstrength is preferred. For the serviceability limit state, a comparison of the level of design earthquakes and performance criteria of the UBC, Tri-Services Manual, and the Japanese code indicates that the UBC produces the most flexible structure, and that UBC does not control structural damage. It is suggested that the UBC adopts an explicit serviceability design procedure.

Response Modification Factor for Y-Eccentric-Braced Steel Frame Structures Designed Based on Chinese Code

2014 ◽  
Vol 580-583 ◽  
pp. 1449-1457
Author(s):  
Wen Xia Yang ◽  
Qiang Gu ◽  
Ping Zhou Cao ◽  
Rong Jin Shi
Keyword(s):  
Pushover Analysis ◽  
Design Procedure ◽  
Response Spectra ◽  
Elastic Response ◽  
Base Shear ◽  
Response Modification Factor ◽  
Linear Elastic ◽  
Elastic Response Spectra ◽  
Modification Factor ◽  
Steel Frame Structures

In current seismic design procedure, structure base shear is calculated according to the linear elastic response spectra divided by the response modification factor, which accounts for ductility and overstrength of a structural system. In this paper, the response modification factors of Y-eccentric braced steel frames (YECBF) designed based on Chinese Code were evaluated by an improved pushover analysis on 12 examples with various stories and spans lengths. According to the analysis results, the effects of fundamental periods, storey numbers, and spans of frames on the behavior factor were studied. In the end, an appropriate response modification factor was proposed for YECBF designed base on Chinese Code.

Underground Tunnels Exposed to Internal Blast: Effect of the Explosive Source Position

2016 ◽  
Vol 711 ◽  
pp. 852-859
Author(s):  
Matteo Colombo ◽  
Paolo Martinelli ◽  
Marco di Prisco
Keyword(s):  
Limit State ◽  
Design Procedure ◽  
Internal Diameter ◽  
Ultimate Limit State ◽  
Fe Model ◽  
Average Width ◽  
Internal Explosion ◽  
Explosive Source ◽  
Blast Effect ◽  
Tunnel Cross Section

The design procedure recently proposed by the same authors and based on a simplified FE model for underground tunnels subjected to internal explosion is extended in this work taking into account different possible positions of the explosive source inside the tunnel. The situation in which the internal explosion is preceded by fire accidents is also analyzed. The reference situation is represented by the explosive source located at the center of the tunnel cross–section. The tunnel geometry considered is that of the metro line in Brescia, Italy. It has an internal diameter of about 8.15 m and is located about 23.1 m below the surface. Six segments and a smaller key segment (6+1) make up the tunnel. The ring has an average width of about 1.5 m. Dynamic analyses were carried out in order to reproduce the blast scenario. The aim of this work is to evaluate the influence of the position of the explosive source on the tunnel dynamic response. An ultimate limit state criterion based on the eccentric ultimate flexural capacity and capable of including fire–blast interaction is adopted. An innovative layered precast tunnel segment solution made of different fiber–reinforced cementitious composites is considered.

Extreme Modal Combinations for Pushover Analysis of RC Buildings

2013 ◽  
Vol 553 ◽  
pp. 117-124
Author(s):  
Ante Mihanović ◽  
Boris Trogrlić ◽  
Ivan Balić
Keyword(s):  
Limit State ◽  
Pushover Analysis ◽  
Mode Shapes ◽  
Eurocode 8 ◽  
Elastic Model ◽  
Seismic Action ◽  
Target Displacement ◽  
Ground Acceleration ◽  
Higher Modes ◽  
Practical Procedure

The pushover method is a practical procedure for comprehensive nonlinear analysis of structures subjected to seismic action. Application of this method, in accordance with the Eurocode 8 rules and due to engineering simplicity, favours application utilizing the first mode. The aim of the presented research in this paper was to find the influence of multi modal combinations in assessing the bearing capacity of reinforced concrete (RC) frames and walls. This paper presents a procedure in which the most extreme state is defined by the lowest ground acceleration caused by a predetermined shape of an elastic spectrum. The extreme bearing value is obtained by the envelope principle. Mode shapes and period sizes are determined on a linear elastic model while the limit state of the load bearing system is evaluated in a nonlinear state of structures. Results of the analysis show that influences of higher modes are significantly higher and that the safety/reliability, indicated by the criteria for the target displacement, in accordance with Eurocode 8 (Annex B), is not achieved. Inclusion of higher modes, in some presented examples, decreases the peak ground acceleration by more than two times, which is significantly less favourable than the target displacement criteria.

scholarly journals A RATIONALIZED SEISMIC DESIGN METHOD FOR BUILDINGS IN EARTHQUAKE-PRONE DEVELOPING COUNTRIES

2021 ◽  
Vol 11 (4) ◽  
pp. 266-279
Author(s):  
Tint Lwin ◽  
Takeshi Koike ◽  
Ji Dang
Keyword(s):  
Developing Countries ◽  
Seismic Design ◽  
Design Method ◽  
Limit State ◽  
Design Procedure ◽  
Ultimate Limit State ◽  
Design Guideline ◽  
Seismic Safety ◽  
Seismic Design Method ◽  
Ultimate Limit

In general, the US codes such as the UBC-97 and ASCE-7 are widely used in developing countries including Myanmar, Syria, Philippines and so on. When the current seismic design guideline based on the UBC-97 and ACI 318-99 in Myanmar is assessed, several problems can be found in the following items: firstly, the fundamental period is not checked in modeling; secondly, reduction factor R is introduced a priori for the base shear estimation. And finally, a limit state assessment is done only for Design Basic Earthquake (DBE) but not for other design earthquakes. As a result, adequate yield strength is not checked for Maximum Operational Earthquake (MOE). Then there is no way to assess the seismic safety of the ultimate limit state for Maximum Considered Earthquake (MCE). In order to solve these problems, a rationalized seismic design method for earthquake prone developing countries is proposed. A new seismic design method is developed for MOE and MCE with adequate yield acceleration and typical period of the building estimated by using pushover analysis. A simplified procedure to estimate the inelastic response for a given design spectrum is also proposed. Finally, this design procedure can provide a rational method to assess the seismic safety for the ultimate limit of the building.

From Design to Earthquake Loss Assessment of Steel Moment-Resisting Frames

2018 ◽  
Vol 763 ◽  
pp. 124-130 ◽  
Author(s):  
Luís Macedo ◽  
Antonio Silva ◽  
José Miguel Castro
Keyword(s):  
Seismic Design ◽  
Eurocode 8 ◽  
Loss Assessment ◽  
Behaviour Factor ◽  
Steel Moment Resisting Frames ◽  
Performance Factors ◽  
Moment Resisting Frames ◽  
Moment Resisting ◽  
Earthquake Loss ◽  
Steel Mrfs

Steel moment-resisting frames (MRFs) are well known for their ductile and stable hysteretic behaviour. For this reason, they are an attractive and effective structural system for seismic resistance. Current seismic design codes, namely Eurocode 8, provide system performance factors that should be used in the seismic design under different ductility classes. However, recent research studies have shown that the use of the code-prescribed performance factors lead to stiffer and heavier structural solutions that are not consistent with the performance-based design assumptions. A new methodology, Improved Force-Based Design (IFBD), has recently been proposed with the aim of a more rational determination of the adopted value of the behaviour factor, q, instead of using the upper bound reference values provided by the design code. This paper investigates if the obtained values of q for both EC8 and IFBD concerning steel MRFs are not only adequate, but also provide sufficient margins against collapse under maximum considered earthquake (MCE) ground motions. To this end, the methodology proposed in FEMA P695 was used. Additionally, the expected direct economic seismic losses are computed according to the PEER-PBEE methodology.

Seismic Reliability of a Fixed Offshore Platform Against Collapse

2014 ◽  
Author(s):  
Mojtaba Dyanati ◽  
Qindan Huang
Keyword(s):  
Seismic Performance ◽  
Limit State ◽  
Shear Capacity ◽  
Offshore Platform ◽  
Ultimate Limit State ◽  
State Function ◽  
Base Shear ◽  
Offshore Structure ◽  
Seismic Reliability ◽  
Fixed Offshore Platform

As many jacket type steel platforms have been constructed in the highly active seismic area, seismic reliability evaluation of such structures is desirable. Ultimate limit state (ULS) with base shear capacity and demand can be used to estimate seismic performance of fixed offshore platform against collapse. Base shear capacity is evaluated from pushover analysis on a 3D finite element model of the offshore structure using different load patterns. Base shear demand is calculated from spectral acceleration at a given site and the total mass of the platform. Uncertainties are considered in both capacity and demand evaluations. With the limit state function, seismic fragility of a prototype structure is assessed using reliability analysis. The results indicate that various load patterns affect the seismic performance evaluation. It is also found that the steel yield stress is a critical parameter in the reliability of the steel jacket platforms.

Design of Mooring Lines of Floating Offshore Wind Turbine in Jeju Offshore Area

2014 ◽  
Author(s):  
Hyungjun Kim ◽  
Joonmo Choung ◽  
Gi-Young Jeon
Keyword(s):  
Wind Turbine ◽  
Limit State ◽  
Design Procedure ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Ultimate Limit State ◽  
Mooring Lines ◽  
Offshore Area ◽  
Floating Offshore Wind Turbine ◽  
Wind Turbine System

This paper presents a mooring design procedure of a floating offshore wind turbine. The offshore environment data of Jeju south sea collected from Korea Hydrographic and Oceanographic Administration (KHOA) are used as environmental conditions for hydrodynamic analysis. A semi-submersible floating wind turbine system is considered based on Offshore Code Comparison Collaborative Continuation (OC4) DeepCWind platform and the National Renewable Energy Laboratory (NREL) 5MW class wind turbine. Catenary mooring with studless chain is chosen as the mooring system. Important design decisions such as how large the nominal sizes are, how long the mooring lines are, how far the anchor points are located, are demonstrated in detail. Considering ultimate limit state and fatigue limit state based on 100-year return period and 50 year design life, respectively, long-term predictions of breaking strength and fatigue are performed.

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