• Journal of the Earthquake Engineering Society of Korea
• /
• v.20 no.6
• /
• pp.401-412
• /
• 2016

On Tuesday, January 17, 1995, an earthquake of magnitude 7.2 struck the Port of Kobe. In effect, the port was practically destroyed. After a hazard investigation, researchers reached a consensus to adopt a performance-based design in port and harbor structures in Japan. A residual displacement of geotechnical structures after an earthquake is one of the most important engineering demands in performance-based earthquake-resistant design. Thus, it is essential to provide reliable responses of geotechnical structures after an earthquake through various techniques. Today, a nonlinear explicit response history analysis(NERHA) of geotechnical structures is the most efficient way to achieve this goal. However, verification of the effective stress analysis, including post liquefaction behavior, is difficult to perform at a laboratory scale. This study aims to rigorously verify the NERHA by using well-defined field measurements, existing numerical tools, and constitutive models. The man-made, Port Island, in Kobe provides intensive hazard investigation data, strong motion records of 1995 Kobe earthquake, and sufficient engineering parameters of the soil. Two dimensional numerical analysis was conducted on the caisson quay wall section at Port Island subjected to the 1995 Kobe earthquake. The analysis result matches very well with the hazard investigation data. The NERHA procedure presented in this paper can be used in further studies to explain and examine the effects of other factors on the seismic behavior of gravity quay walls in liquefiable soil areas.

• Journal of The Korean Digital Architecture Interior Association
• /
• v.11 no.2
• /
• pp.115-121
• /
• 2011

Occurrence of earthquakes have been increased all over the world and also, magnitude of earthquakes have been larger these days. Earthquake can be happened in Korea and is not a safe country any more. Many buildings are exposed at danger without any alternatives against earthquake in Korea. Among various kinds of buildings, school buildings are very important and urgent, because many students stays at school and young students have some difficulty to evacuate. Also, most existing school buildings in Korea were not designed considering earthquake resistant design codes. Thus, in this study, 3 types of braces were applied for seismic retrofits of existing school buildings using commercial structural analysis software and effective seismic retrofits were evaluated and discussed based on results by time history analysis.

• Steel and Composite Structures
• /
• v.44 no.3
• /
• pp.325-337
• /
• 2022

In this research, an earthquake-resistant structural system consisting of a pin-connected steel frame and a bracing with metallic fuses is proposed. Contrary to the conventional braced frames, the main structural elements are deemed to remain elastic under earthquakes and the seismic energy is efficiently dissipated by the damper-braces with an amplification mechanism. The superiority of the proposed damping system lies in easy manufacture, high yield capacity and energy dissipation, and an effortless replacement of damaged fuses after earthquake events. Furthermore, the stiffness and the yield capacity are almost decoupled in the proposed damper-brace which makes it highly versatile for performance-based seismic design compared to most other dampers. A special attention is paid to derive the theoretical formulation for nonlinear behavior of the proposed damper-brace, which is verified using analytical results. Next, a direct displacement-based design procedure is provided for the proposed system and an example structure is designed and analyzed thoroughly to check its seismic performance. The results show that the proposed system designed with the provided procedure satisfies the given performance objective and can be used for developing highly efficient low-damage structures.

• Computers and Concrete
• /
• v.16 no.1
• /
• pp.99-123
• /
• 2015

In this study, structural vulnerability of reinforced concrete moment resisting frames (RC-MRFs) by considering the Iran-specific characteristics is investigated to manage the earthquake risk in terms of multicomponent seismic excitations. Low and medium rise RC-MRFs, which constitute approximately 80-90% of the total buildings stock in Iran, are focused in this fragility-based assessment. The seismic design of 3-12 story RC-MRFs are carried out according to the Iranian Code of Practice for Seismic Resistant Design of Buildings (Standard No. 2800), and the analytical models are formed accordingly in open source nonlinear platforms. Frame structures are categorized in three subclasses according to the specific characteristics of construction practice and the observed seismic performance after major earthquakes in Iran. Both far and near fields' ground motions have been considered in the fragility estimation. An optimal intensity measure (IM) called Sa, avg and beta probability distribution were used to obtain reliable fragility-based database for earthquake damage and loss estimation of RC buildings stock in urban areas of Iran. Nonlinear incremental dynamic analyses by means of lumped-parameter based structural models have been simulated and performed to extract the fragility curves. Approximate confidence bounds are developed to represent the epistemic uncertainties inherent in the fragility estimations. Consequently, it's shown that including vertical ground motion in the analysis is highly recommended for reliable seismic assessment of RC buildings.

• Earthquakes and Structures
• /
• v.25 no.1
• /
• pp.1-13
• /
• 2023

Reinforced concrete (RC) moment frames are used as lateral seismic load resisting systems in mid- and high-rise buildings in different regions of the world. Based on the seismic design provisions and construction details presented in design codes, RC frames with different levels of ductility (ordinary, intermediate, and special) can be designed and constructed. In Iran, there are RC buildings with various uses which have been constructed based on different editions of design codes. The seismic performance of RC structures (particularly moment frames) in real seismic events is of great importance. In this paper, the observations made on damaged RC moment frames after the destructive Sarpol-e Zahab earthquake with a moment magnitude of 7.3 are reported. Different levels of damage from the development of cracks in the structural and non-structural elements to the total collapse of buildings were observed. Furthermore, undesirable failure modes which are not expected in ductile seismic-resistant buildings were frequently observed in the damaged buildings. The RC moment frames built based on the previous editions of the design codes showed partial or total collapse in this seismic event. The extensive destruction of RC moment frames compared with the other structural systems (such as braced steel frames and confined masonry buildings) was attributed not only to the deficiencies in the construction practice of these buildings but also to the design procedure. In addition, the failure and collapse of masonry infills in RC moment frames were frequent modes of failure in this seismic event. In this paper, the main reasons related to design practice which led to extensive damage in the RC moment frames and their collapse are addressed.

• Structural Engineering and Mechanics
• /
• v.12 no.6
• /
• pp.573-594
• /
• 2001

A two-level displacement-based design procedure is developed. To obtain the displacement demands, elastic spectra for occasional earthquakes and inelastic spectra for rare earthquakes are used. Minimum global stiffness and strength to be supplied to the structure are based on specified maximum permissible drift limits and on the condition that the structure responds within the elastic range for occasional earthquakes. The performance of the structure may be assessed by an inelastic push-over analysis to the required displacement and the evaluation of damage indices. The approach is applied to the design of a five-story reinforced concrete coupled wall structure located in the most hazardous seismic region of Argentina. The inelastic dynamic response of the structure subjected to real and artificially generated acceleration time histories is also analyzed. Finally, advantages and limitations of the proposed procedure from the conceptual point of view and practical application are discussed.

• Structural Engineering and Mechanics
• /
• v.63 no.2
• /
• pp.259-268
• /
• 2017

In this paper, the incremental nonlinear dynamic analysis is used to evaluate the seismic performance of steel moment frame structures. To this purpose, three special moment frame structure with 5, 10 and 15 stories are designed according to the Iran's national building code for steel structures and the provisions for design of earthquake resistant buildings (2800 code). Incremental Nonlinear Analysis (IDA) is performed for 15 different ground motions, and responses of the structures are evaluated. For the immediate occupancy and the collapse prevention performance levels, the probability that seismic demand exceeds the seismic capacity of the structures is computed based on FEMA350. Also, fragility curves are plotted for three high-code damage levels using HASUS provisions. Based on the obtained results, it is evident that increase in the height of the frame structures reduces the reliability level. In addition, it is concluded that for the design earthquake the probability of exceeding average collapse prevention level is considerably larger than high and full collapse prevention levels.9.

• Smart Structures and Systems
• /
• v.1 no.2
• /
• pp.141-158
• /
• 2005

A new design of distributed crack sensors based on the topological change of transmission line cables is presented for the condition assessment of reinforced concrete (RC) structures during and immediately after an earthquake event. This study is primarily focused on the performance of cable sensors under dynamic loading, particularly a feature that allows for some "memory" of the crack history of an RC member. This feature enables the post-earthquake condition assessment of structural members such as RC columns, in which the earthquake-induced cracks are closed immediately after an earthquake event due to gravity loads, and are visually undetectable. Factors affecting the onset of the feature were investigated experimentally with small-scale RC beams under cyclic loading. Test results indicated that both crack width and the number of loading cycles were instrumental in the onset of the memory feature of cable sensors. Practical issues related to dynamic acquisition with the sensors are discussed. The sensors were proven to be fatigue resistant from shake table tests of RC columns. The sensors continued to show useful performance after the columns can no longer support additional loads.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.27 no.2
• /
• pp.91-99
• /
• 2023

Structural vibration induced by earthquake hazards is one of the most significant concerns in structure performance-based design. Structural hazards evoked from seismic events must be properly identified to make buildings resilient enough to withstand extreme earthquake loadings. To investigate the effects of combined earthquake-resistant systems, shear walls and five types of dampers are incorporated in nineteen structural models by altering their arrangements. All the building models were developed as per ACI 318-14 and ASCE 7-16. Seismic fragility curves were developed from the incremental dynamic analyses (IDA) performed by using seven sets of ground motions, and eventually, by following FEMA P695 provisions, the collapse margin ratio (CMR) was computed from the collapse curves. It is evident from the results that the seismic performance of the proposed combined shear wall-damper system is significantly better than the models equipped with shear walls only. The scrutinized dual seismic resisting system is expected to be applied practically to ensure a multi-level shield for tall structures in high seismic risk zones.

• Structural Engineering and Mechanics
• /
• v.53 no.2
• /
• pp.227-248
• /
• 2015

A CFPBS (Cone-type Friction Pendulum Bearing System) was developed to control the acceleration delivered to a structure to prevent the damage and degradation of critical communication equipment during earthquakes. This study evaluated the isolation performance of the CFPBS by numerical analysis. The CFPBS was manufactured in the shape of a cone differenced with the existing FPS (Friction Pendulum System), and a pattern was engraved on the friction surface. The natural frequencies of the CFPBS were evaluated from a free-vibration test with a seismic isolator system consisting of 4 CFPBS. To confirm the earthquake-resistant performance, a numerical analysis program was prepared using the equation of the CFPBS induced from the equations of motion. The equation reported by Tsai for the rolling-type seismic isolation bearings was proposed to design the equation of the CFPBS. Artificial seismic waves that satisfy the maximum earthquake scale of the Korean Building Code-Structural (KBC-2005) were created and verified to review the earthquake-resistant performance of the CFPBS by numerical analysis. The superstructural mass of the CFPBS and the skew angle of friction surface were considered for numerical analysis with El Centro NS, Kobe NS and artificial seismic waves. The CFPBS isolation performance evaluation was based on the numerical analysis results, and comparative analysis was performed between the results from numerical analysis and simplified theoretical equation under the same conditions. The validity of numerical analysis was verified from the shaking table test.