Nonlinear Analyses of an Instrumented Structure Damaged in the 1994 Northridge Earthquake

1998 ◽  
Vol 14 (2) ◽  
pp. 265-283 ◽  
Author(s):  
Y. Roger Li ◽  
James O. Jirsa
Keyword(s):  
Nonlinear Dynamic ◽  
Shear Failure ◽  
Time History ◽  
Lateral Force ◽  
Economic Losses ◽  
Northridge Earthquake ◽  
Dynamic Time ◽  
Nonlinear Dynamic Analyses ◽  
Structural Engineers ◽  
1994 Northridge Earthquake

The extensive damage and economic losses that occurred during the 1994 Northridge and other recent moderate earthquakes have stimulated structural engineers to consider how to protect economic investment besides meeting life safety requirements of buildings. The equivalent lateral force procedure for seismic design is based on implicit consideration of inelastic response of structures in earthquakes. Experience with past earthquakes has indicated that this procedure is inadequate in controlling damage in buildings. The objective of this study is to demonstrate the capability of nonlinear dynamic analyses to predict performance of reinforced concrete structures subjected to earthquake ground motions. An instrumented building damaged during the 1994 Northridge earthquake was analyzed using DRAIN-2D, and the results were compared with recorded response data. Both nonlinear dynamic time history and nonlinear static push-over analyses were performed, and correlations between these two nonlinear analysis methods were studied. A simplified shear failure model was proposed in the study.

Seismic Design of Lightweight Metal Building Systems

2001 ◽  
Vol 17 (1) ◽  
pp. 37-46 ◽  
Author(s):  
Timothy Wayne Mays
Keyword(s):  
Structural Steel ◽  
Linear Time ◽  
Time History ◽  
Lateral Force ◽  
Building Structures ◽  
Northridge Earthquake ◽  
Steel Buildings ◽  
Building Systems ◽  
Metal Building ◽  
Design Earthquake

As a result of failures uncovered after the Northridge earthquake, the AISC Seismic Provisions for Structural Steel Buildings has become extremely stringent in its design provisions for moment frame structures. Although the changes are justified, they are not necessary for every type of building system. Some structures can be safely designed to resist earthquake forces elastically without concern of structural collapse. Metal buildings are typically lightweight, and small inertia forces from the design earthquake will not usually result in an inelastic response of a system that is properly designed to resist wind forces. In this paper, metal building systems are analyzed using an equivalent lateral force method and a linear time history analysis to show that typical metal building systems will respond elastically to the design earthquake. Specifically, using the International Building Code along with the aforementioned document, it is shown in the following sections that for lightweight metal building structures, adherence to the AISC Seismic Provisions for Structural Steel Buildings is not required in most cases except for locations on the West Coast and a few regions east of the Rocky Mountains. Elastic design methodology is discussed and design recommendations applicable to metal building systems are provided.

Seismic evaluation of a 56-storey residential reinforced concrete high-rise building based on nonlinear dynamic time-history analyses

2010 ◽  
Vol 21 (4) ◽  
pp. 233-248 ◽  
Author(s):  
Siamak Epackachi ◽  
Rasoul Mirghaderi ◽  
Omid Esmaili ◽  
Ali Asghar Taheri Behbahani ◽  
Shahram Vahdani
Keyword(s):  
Reinforced Concrete ◽  
Nonlinear Dynamic ◽  
Time History ◽  
Seismic Evaluation ◽  
High Rise ◽  
High Rise Building ◽  
Dynamic Time

Effects of column and superstructure stiffness on the seismic response of bridges in the transverse direction

2013 ◽  
Vol 40 (8) ◽  
pp. 827-839 ◽  
Author(s):  
Payam Tehrani ◽  
Denis Mitchell
Keyword(s):  
Seismic Response ◽  
Nonlinear Dynamic ◽  
Transverse Direction ◽  
Time History ◽  
Highway Bridge ◽  
Design Code ◽  
Bridge Design ◽  
Dynamic Analyses ◽  
Nonlinear Dynamic Analyses ◽  
Degree Of Irregularity

The transverse seismic responses of continuous 4-span bridges designed based on the 2006 Canadian Highway Bridge Design Code were studied using inelastic time history analyses. A total of 648 bridge configurations were considered in which the column heights, column diameters, superstructure stiffness and mass as well as abutment restraint conditions were studied. The maximum ductility demands obtained using elastic and inelastic analyses were compared to study the influence of the degree of irregularity. The effects of column stiffness ratios and superstructure to substructure stiffness ratios on the maximum ductility demands and concentration of ductility demands were investigated. A number of different regularity indices were compared to determine the suitability of these different indices in predicting the influence of irregularity. This study demonstrates the conservative nature of the 2006 Canadian Highway Bridge Design Code and provides some guidance on factors for determining the degree of irregularity and suitable regularity indices when carrying out nonlinear dynamic analyses of bridges.

Seismic Response of an Instrumented 13-Story Steel Frame Building Damaged in the 1994 Northridge Earthquake

1997 ◽  
Vol 13 (1) ◽  
pp. 131-149 ◽  
Author(s):  
Chia-Ming Uang ◽  
Qi-Song Yu ◽  
Ali Sadre ◽  
David Bonowitz ◽  
Nabih Youssef ◽  
...  
Keyword(s):  
Time History ◽  
Regular Structure ◽  
Primary Objective ◽  
Elastic Model ◽  
Northridge Earthquake ◽  
Steel Moment Frame ◽  
Modeling And Analysis ◽  
Panel Zone ◽  
Inelastic Analysis ◽  
1994 Northridge Earthquake

This paper summarizes a case study of a 13-story welded steel moment frame (WSMF) building affected by the 1994 Northridge earthquake. The building, which was instrumented, sustained extensive damage to its welded connections. Ground motion records from the basement and response records from the sixth and twelfth floors were available. Damage data was collected with post-earthquake inspection and testing of each joint. The primary objective of the study was to compare modeled behavior with recorded response in order to assess the value of present analytical tools and modeling techniques for predicting the distribution and severity of connection failures. Calculated elastic time-history displacements matched well with recorded displacements in the E-W direction, less so in the heavily-damaged N-S direction where the elastic model was unable to simulate fractured moment connections. In the elastic analyses, joint demand was represented by beam demand-capacity ratios (DCRs). The highest beam DCRs were concentrated between the second and seventh floors; these locations correlated strongly with observed damage. Inelastic time-history analyses improved the displacement match in the N-S direction. They also indicated that panel zone yielding would have controlled the intended ductile response. This study suggests that for a regular structure, current modeling and analysis tools for both elastic and inelastic analysis, while unable to simulate premature brittle fractures, can be useful for predicting in a probabilistic way the intensity and distribution of damage expected in moderate seismic events.

scholarly journals Quasi-Resonance Effects Observed in The 1994 Northridge Earthquake, and Others

1998 ◽  
Vol 5 (3) ◽  
pp. 153-158 ◽  
Author(s):  
Edward G. Fischer ◽  
Thomas P. Fischer
Keyword(s):  
Time History ◽  
Shaking Table ◽  
Northridge Earthquake ◽  
Shaking Table Tests ◽  
Circuit Breakers ◽  
Resonance Effects ◽  
Earthquake Records ◽  
San Fernando ◽  
Conservative Simulation ◽  
1994 Northridge Earthquake

Sine-beat phenomena have been found in the 1994 Northridge earthquake records, and they are capable of producing time-history responses and damaging quasi-resonance effects in structures. Linear, single DOF (degree of freedom) oscillators, in lieu of nonlinear, multiple DOF systems, have been found adequate to discuss the failures of tall circuit breakers during the 1971 San Fernando and the 1989 Loma Prieta quakes in California. The use of sine-beat excitation for seismic-shaking-table tests of equipment continues to be a conservative simulation of earthquakes.

Influence Factors and Repair Effects of Seismic Damage to a Box Section Steel Pier

2019 ◽  
Vol 13 (03n04) ◽  
pp. 1940001
Author(s):  
Zhongqiu Fu ◽  
Dongyang Wu ◽  
Liang Fang ◽  
Donghua Chen ◽  
Bohai Ji
Keyword(s):  
Energy Dissipation ◽  
Bearing Capacity ◽  
Seismic Performance ◽  
Nonlinear Dynamic ◽  
Time History ◽  
Time History Analysis ◽  
Steel Plates ◽  
Box Section ◽  
History Analysis ◽  
Dynamic Time

The seismic performance of a steel pier of box section was studied through low-cycle cyclic testing. The damaged specimens were repaired by filling with concrete and welding steel plates. The low-cycle cyclic test was then repeated. The effects of repairs were investigated by comparison of failure mode, energy dissipation performance, and ductility before and after repair. To supplement the data, the influence of different factors on the seismic bearing capacity and ductility of steel piers were analyzed by finite element method. The repair effects were compared by threshold of the displacement from the experiment. Based on the displacement angle response of the nonlinear dynamic time history analysis, the seismic performance is checked. The results show that repair had favourable effects on the damaged specimens. The horizontal bearing capacity and ductility of the specimens filled with concrete are significantly enhanced. Reinforcement by steel plates can increase the ductility and cumulative energy dissipation of the steel pier. An axial compression ratio of 0.2 and a concrete filling ratio of 30% are suggested. The horizontal bearing capacity can be improved by increasing the steel strength while the concrete strength shows little effect. The angular displacement from nonlinear dynamic time-history analysis was less than the test threshold, so the existing methods used for seismic performance verification are safe.

Effects of coupled vertical stiffness-strength irregularity due to modified interstorey height

2011 ◽  
Vol 44 (1) ◽  
pp. 31-44
Author(s):  
Vinod K. Sadashiva ◽  
Gregory A. MacRae ◽  
Bruce L. Deam
Keyword(s):  
Time History ◽  
Lateral Force ◽  
Code Design ◽  
Maximum Increase ◽  
Vertical Stiffness ◽  
Regular Structures ◽  
Irregular Structures ◽  
Drift Ratio ◽  
Interstorey Drift ◽  
Dynamic Time

Structures may have vertical stiffness or strength irregularity for many reasons. In many practical cases, a change in storey stiffness, results a change in strength at the same storey. In this paper, the effect of a change in interstorey height is quantified. In order to do this, relationships between storey stiffness and strength resulting due to a modified interstorey height for a few common lateral force resisting systems was considered. It was applied to simple shear-type structures of 3, 5, 9 and 15 storeys, assumed to be located in Wellington. All structures were considered to have a constant mass at every floor level. Both regular and irregular structures were designed in accordance with the Equivalent Static method of the current New Zealand seismic design Standard, NZS 1170.5. Regular structures were designed to either (i) produce a constant target interstorey drift ratio at all the storeys simultaneously or (ii) to have uniform stiffness distribution over the height of the structure, with the target interstorey drift ratio at the first storey. An “interstorey height ratio” was defined as the ratio of modified to initial interstorey height, and applied separately at the first storey, mid-height storey and at the topmost storey by amounts between 0.5 and 3. The modified structures were then redesigned until the target interstorey drift ratio was achieved at the critical storey/storeys. Design structural ductility factors of 1, 2, 3, 4 and 6, and target (design) interstorey drift ratios ranging between 0.5% and 3%, were used in this study. Inelastic dynamic time-history analysis was carried out by subjecting these structures to code design level earthquake records, and the maximum interstorey drift ratio demands due to each record were used to compare the responses of regular and irregular structures. It was found that structural types in which only the storey stiffness was modified due to a change in the interstorey height produced the maximum increase in drift demands rather than structural forms with other stiffness-strength coupling cases. Shorter structures having an increased first storey height, and taller structures with an increased middle storey height generally produced greater interstorey drift demands than regular structures. For cases of increased storey stiffness due to decreased storey heights, the shorter structures with a decreased middle storey height resulted in higher median peak ISDR due to irregularity. A simple equation describing the maximum increase in response due to modifications to a storey height was developed. The equation was used along with the realistic correlations between storey stiffness and strength to obtain the governing code regularity limit.

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