Interpretation of significant ground-response and structure strong motions recorded during the 1994 Northridge earthquake

1996 ◽  
Vol 86 (1B) ◽  
pp. S231-S246 ◽  
Author(s):  
A. F. Shakal ◽  
M. J. Huang ◽  
R. B. Darragh
Keyword(s):  
Flexible Structures ◽  
Northridge Earthquake ◽  
Moment Frame ◽  
Ground Response ◽  
Short Period ◽  
Frame Buildings ◽  
Story Drift ◽  
San Fernando ◽  
San Fernando Valley ◽  
The Moment

Abstract Some of the largest accelerations and velocities ever recorded at ground-response and structural sites occurred during the Northridge earthquake. These motions are greater than most existing attenuation models would have predicted. Although the motions are large, the correspondence between measured acceleration and damage requires further study, since some sites with high acceleration experienced only moderate damage. Also, some peak vertical accelerations were larger than the horizontal, but in general, they are smaller and fit the pattern observed in previous earthquakes. Strong-motion records processed to date show significant differences in acceleration and velocity waveforms and amplitudes across the San Fernando Valley. Analysis of processed data from several buildings in the San Fernando Valley indicates that short-period buildings such as shear-wall buildings experienced large forces and relatively low inter-story drift during the Northridge earthquake. However, long-period (1 to 5 sec) steel or concrete moment-frame buildings experienced large inter-story drift. For this earthquake, accelerations did not always amplify from base to roof for flexible structures like the moment-frame buildings, but the displacements were always larger at the roof. The drifts at many of the moment-frame buildings were larger than the drift limit for working stress design in the building code. The records from a base-isolated building indicate that high-frequency motion was reduced significantly by the isolators. The isolators deformed about 3.5 cm, which is much less than the design displacement. The records from a parking structure show important features of the seismic response of this class of structure.

Seismology

1995 ◽  
Vol 11 (2_suppl) ◽  
pp. 1-12
Keyword(s):  
Los Angeles ◽  
Seismic Hazard ◽  
Focal Depth ◽  
High Rate ◽  
Northridge Earthquake ◽  
Los Angeles Basin ◽  
San Fernando ◽  
Northern Edge ◽  
San Fernando Valley ◽  
The Moment

The Northridge earthquake occurred on January 17, 1994, at 4:31 a.m. Pacific Standard Time. The hypocenter was about 32 km west-northwest of Los Angeles in the San Fernando Valley at a relatively deep focal depth of 19 km. The moment magnitude for the earthquake is Mw6.7. The earthquake occurred on a south-southwest dipping thrust ramp beneath the San Fernando Valley and, thus, reemphasized the seismic hazard of concealed faults in the greater Los Angeles region. The Northridge earthquake also indicates a continuing high rate of seismicity along the northern edge of the Los Angeles basin.

Application of Fracture Mechanics to Steel Connections in Moment Frames under Seismic Loading

1997 ◽  
Vol 1 (1) ◽  
pp. 23-37 ◽  
Author(s):  
C. Joh ◽  
W.F. Chen
Keyword(s):  
Fracture Mechanics ◽  
Steel Structures ◽  
Northridge Earthquake ◽  
Moment Frames ◽  
Moment Connections ◽  
Related Factors ◽  
Steel Connections ◽  
Moment Connection ◽  
San Fernando ◽  
The Moment

The 6.8 magnitude Northridge earthquake that shook California's San Fernando Valley on January 17 in 1994, did not cause the collapse of any steel structures but connections, confidently designed and constructed in the past with traditional code simplification and common site welding techniques, were discovered not to meet our expectations. This paper reviews connection failures during the 1994 Northridge earthquake and the design philosophy and examines the post-Northridge earthquake experimental and analytical researches. Possible causes of the moment connections damage are categorized into three classes; welding-related factors, design-related factors, and material-related factors. For the analyses, the idealizations of the moment connection considering each factor are studied. From the idealization of the moment connection, the five-plate model is analyzed to investigate the stress concentration and stress state of the connection. The equivalent design crack models are investigated using the fracture mechanics approach.

scholarly journals Experimental Study on the Seismic Performance of Steel H-Shaped Beam-to-Column Connections

2020 ◽  
Vol 20 (5) ◽  
pp. 1-9
Author(s):  
Seongyeon Seo
Keyword(s):  
Seismic Performance ◽  
Steel Structures ◽  
Initial Stiffness ◽  
Moment Frame ◽  
Shaped Beam ◽  
Shear Connections ◽  
Story Drift ◽  
Frame System ◽  
The Moment ◽  
Plastic Rotation Capacity

In terms of the moment frame system of steel structures, early brittle fractures developed in the H-shaped beam-to-column connection during the Northridge and Kobe earthquakes, thereby indicating insufficient seismic performance of these components. In this study, experiments were conducted on two-side shear connections of web and rib plate reinforcements of the flanges on an H-shaped beam-to-column connection. According to the test results, the H-shaped beam-to-column connections with two-side shear connections of beam web and rib plate reinforcements of the flanges were superior to the existing connections in terms of initial stiffness, energy dissipation capacity, and plastic rotational capacity. The test values exceeded 4.2%, 0.027 rad, and 125% in terms of story drift ratio, total plastic rotation capacity, and full plastic moment of the beam, respectively. Accordingly, the proposed H-shaped beam-to-column connection showed better performance than that of the intermediate moment frame regarding seismic design.

Design Guidelines for Steel Moment Frames for New Buildings

2003 ◽  
Vol 19 (2) ◽  
pp. 269-290
Author(s):  
C. Mark Saunders
Keyword(s):  
Lateral Force ◽  
Design Guidelines ◽  
Northridge Earthquake ◽  
Moment Frames ◽  
Steel Moment Frames ◽  
Moment Frame ◽  
Steel Moment Frame ◽  
Simple Set ◽  
Frame Buildings ◽  
New Buildings

The damage to steel moment frames observed in the Northridge earthquake of 1994 led to requirements in codes for use of tested connections, when these systems were to be employed in new buildings. One of the primary goals of the FEMA/SAC project was to develop guidelines for the design of steel moment frames that would return the design process to a relatively simple set of procedures similar to those used in the design of other lateral force-resisting systems. Recommended Seismic Design Criteria for New Steel Moment-Frame Buildings, FEMA-350, presents design guidelines for use of steel moment frames in new buildings, developed from the FEMA/SAC research. This paper provides a general summary of the criteria, and a description of the prequalified connections and recommendations for their use.

scholarly journals Performance of Two 18-Story Steel Moment-Frame Buildings in Southern California during Two Large Simulated San Andreas Earthquakes

2006 ◽  
Vol 22 (4) ◽  
pp. 1035-1061 ◽  
Author(s):  
Swaminathan Krishnan ◽  
Chen Ji ◽  
Dimitri Komatitsch ◽  
Jeroen Tromp
Keyword(s):  
Los Angeles ◽  
Southern California ◽  
Building Code ◽  
Los Angeles Basin ◽  
Moment Frame ◽  
Steel Moment Frame ◽  
Existing Building ◽  
San Andreas ◽  
Frame Buildings ◽  
San Fernando

Using state-of-the-art computational tools in seismology and structural engineering, validated using data from the Mw=6.7 January 1994 Northridge earthquake, we determine the damage to two 18-story steel moment-frame buildings, one existing and one new, located in southern California due to ground motions from two hypothetical magnitude 7.9 earthquakes on the San Andreas Fault. The new building has the same configuration as the existing building but has been redesigned to current building code standards. Two cases are considered: rupture initiating at Parkfield and propagating from north to south, and rupture propagating from south to north and terminating at Parkfield. Severe damage occurs in these buildings at many locations in the region in the north-to-south rupture scenario. Peak velocities of 1 m.s−1 and 2 m.s−1 occur in the Los Angeles Basin and San Fernando Valley, respectively, while the corresponding peak displacements are about 1 m and 2 m, respectively. Peak interstory drifts in the two buildings exceed 0.10 and 0.06 in many areas of the San Fernando Valley and the Los Angeles Basin, respectively. The redesigned building performs significantly better than the existing building; however, its improved design based on the 1997 Uniform Building Code is still not adequate to prevent serious damage. The results from the south-to-north scenario are not as alarming, although damage is serious enough to cause significant business interruption and compromise life safety.

Evaluating and Upgrading Welded Steel Moment-Frame Buildings Using FEMA-351

2003 ◽  
Vol 19 (2) ◽  
pp. 317-334 ◽  
Author(s):  
John D. Hooper
Keyword(s):  
Earthquake Engineering ◽  
Joint Venture ◽  
Northridge Earthquake ◽  
Seismic Evaluation ◽  
Moment Frame ◽  
Steel Moment Frame ◽  
Welded Steel ◽  
Frame Design ◽  
Frame Buildings ◽  
Simplified Procedures

In July 2000, the SAC Joint Venture (a joint venture of the Structural Engineers Association of California, the Applied Technology Council, and California Universities for Research in Earthquake Engineering) prepared a series of recommendations regarding welded steel moment-frame design, evaluation, and upgrade procedures. FEMA-351, Recommended Seismic Evaluation and Upgrade Criteria for Existing Welded Steel Moment-Frame Buildings, was developed to evaluate the probable performance of existing steel moment-frame buildings in future earthquakes and to provide guidance or upgrading these buildings. The procedures introduced in FEMA-351 allow the determination of the level of confidence a structure will be able to achieve based on a specified performance objective, using simplified analytical methods. Simplified procedures for estimating the probable post-earthquake repair costs and nonstructural damage, based on the losses incurred in the 1994 Northridge earthquake, are presented as well. This paper provides a brief chapter-by-chapter overview of the information contained in FEMA-351 and emphasizes the performance evaluation procedures by stepping through the process using an example building.

Seismic Design Guidelines and Provisions for Steel-Framed Buildings: FEMA 267/267A and 1997 AISC Seismic Provisions

2000 ◽  
Vol 16 (1) ◽  
pp. 179-203
Author(s):  
James O. Malley ◽  
Charles J. Carter ◽  
C. Mark Saunders
Keyword(s):  
Wide Spectrum ◽  
Steel Structures ◽  
Design Guidelines ◽  
Northridge Earthquake ◽  
Earthquake Hazards ◽  
Steel Buildings ◽  
Moment Frame ◽  
Steel Moment Frame ◽  
Welded Steel ◽  
Frame Buildings

One of the important surprises of the Northridge earthquake of January 17, 1994, was the widespread and unanticipated brittle fracture of welded steel beam-to-column connections. Although no casualties or collapses occurred during the Northridge earthquake as a result of these connection failures, and many WSMF buildings were not damaged at all, a wide spectrum of brittle connection damage did occur, ranging from minor cracking to completely severed columns. This paper summarizes two of the most important documents that have been developed in response to the damage suffered to steel moment frame buildings in the Northridge earthquake. The first, FEMA 267, Interim Guidelines: Evaluation, Repair, Modification and Design of Welded Steel Moment Frame Structures, was generated from studies undertaken as part of a project initiated by the U.S. Federal Emergency Management Agency (FEMA) to reduce the earthquake hazards posed by steel moment-resisting frame buildings. The second document addressed in this paper is the 1997 edition of the American Institute of Steel Construction (AISC) Seismic Provisions for Structural Steel Buildings (commonly referred to as the AISC Seismic Provisions) that incorporates the new information generated by the FEMA-sponsored project and other investigations on the seismic performance of steel structures, and has been adopted by reference into the 2000 International Building Code (IBC).

scholarly journals KATEGORI DESAIN SEISMIK WILAYAH KOTA PALEMBANG BERDASARKAN SNI 03-1726-2012 DENGAN MENGGUNAKAN PETA HAZARD GEMPA INDONESIA 2010

2017 ◽  
Vol 4 (1) ◽  
pp. 23
Author(s):  
Sapta Sapta ◽  
Sari Farlianti
Keyword(s):  
Seismic Design ◽  
Spectral Response ◽  
Earthquake Hazard ◽  
Frame Structure ◽  
Risk Level ◽  
Moment Frame ◽  
Short Period ◽  
Using Data ◽  
The Moment ◽  
High Level

Seismic Design category described the Risk level of Seismicity are used as the basis for the selection of the Moment Frame Structure  that will be used in the implementation of the design of structures that use the SNI 03-2847-2013. KDS in SNI 03-1726-2012, classified into three levels respectively, namely; Low (SDC A and B), intermediate (SDC C) and high (SDC D, E and F). Classification of SDC are determined based on the values of the SDS and the SD1 is the spectral response acceleration parameter design on a short period and a period of 1,00 second. The value of the SDS and the SD1 is determined the condition of soil density (soft, medium or hard) on the regions reviewed. From the results of the analysis performed using data on Earthquake Hazard Map 2010 by using application designs spectra and on the website of http://puskim.pu.go.id  obtained the value soil for SDS Badger, medium and hard respectively worth 0.43; 0.278; 0.209 SD1 and 0.361; 0.234; 0.179, so it can be inferred that the Palembang area with a high level of risk, namely KDS D, which in the planning of the structure requires using the structure of Special Moment Frame (SRPMK) which refers to the SNI 03-2847-2013. Key words:  Seismic Design category (SDC), Map of the earthquake area, Moment Frame

scholarly journals Improving resilience of moment frames using steel pipe dampers

2018 ◽  
Vol 195 ◽  
pp. 02014
Author(s):  
Junaedi Utomo ◽  
Antonius
Keyword(s):  
Numerical Study ◽  
Steel Pipe ◽  
Frame Structures ◽  
Earthquake Risk ◽  
Moment Frames ◽  
Moment Frame ◽  
Story Drift ◽  
Moment Resisting ◽  
Lateral Displacements ◽  
The Moment

Earthquake resiliency of moment resisting frames, either new or existing ones, are important for maintaining community functionality. Improving earthquake resiliency needs a strong initiative in reducing earthquake risk. Steel pipe dampers can be used to increase earthquake resiliency. Steel pipe dampers, when installed at strategic locations in the moment frame structures, dissipate most of the earthquake energy in structures through inelastic deformation so that other components of the structure are protected. Steel pipe dampers control vibration in moment frame structures and are a disposable component in structures so that the damaged dampers can be replaced easily. Steel pipe dampers are cheap and require low workmanship, therefore the recovery time after disasters is short and the cost of recovery is low. Utilizing steel pipe dampers in passive energy dissipation systems help maintain community functionality during and after disasters. Lateral displacements were quantified and used as performance indicators. Significant drift and inter story drift reduction were achieved during a numerical study. All structural components, except the steel pipe dampers, remain elastic, indicating the effectiveness of the dampers in reducing the losses due to earthquakes.

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