Journal of Seismology and Earthquake Engineering
Volume:19 Issue: 1, Spring 2017

Nonlinear time-history analysis is becoming more common in seismic analysis and design of structures. The key issue in performing this kind of analysis is the appropriate input ground motion. Many engineers select recorded motions from locations other than the project site and modify them by scaling or spectrum matching. A wavelet-based procedure has been used to generate ground motions that are design spectrum compatible. Near-fault ground motions containing strong velocity pulses are of interest in the fields of seismology and earthquake engineering. Sites located in the vicinity of seismic faults may experience ground motions with the effect of forward directivity, causing most of the seismic energy in a single pulse registered early in the velocity history. Baker introduced a quantitative way to distinguish and classify this kind of records. The principle purpose of this article is to survey generating spectrum-compatible time-histories for near-fault via wavelet transform by Baker’s method.

In current work, an effective method is introduced for the optimal cross-section distribution in steel moment resisting frames under severe earthquakes by means of uniform deformation theory and adaptive method. The main goal is to distribute the construction material (weight) along the height of the structure in such a way that the lowest damage due to earthquakes is obtained. In adaptive method, materials gradually transfer from strong parts to weak parts by an iteration procedure during nonlinear time history analysis. In order to demonstrate the effectiveness of the proposed method, the optimal distribution of the cross-sections is obtained for 5 and 10 story steel moment resisting frames. In order to reduce the sensitivity of the optimal response to discrete cross-sections, continuous cross-sections fitted between DIN-Standard cross-sections have been used in order to achieve its optimal state. The steel moment resisting frames are optimized under five natural earthquakes. Results indicate that the optimal frames designed by this method show not only a more uniform deformation under earthquakes, but also less weight in comparison to the original structure designed according to the ASCE07-10 code. The reduction in structural weight reaches 40% in some cases leading to significant reduction in frame construction costs.

Selection of Ground Motion Prediction Equations (GMPEs) within the Seismic Hazard Analysis (SHA) is an important and timely research line of inquiry. A set of 22 regional and worldwide GMPEs have been selected in this research for the purpose of classification. They are classified into clusters in which each cluster is defined to have the most dissimilarity with the other clusters as well as having the most similarity within the cluster. The C-mean clustering algorithm is modified and adapted in order to be applicable in the current study. In addition, six groups are defined for different focal mechanisms and soil types. Then, the GMPE clustering is performed for each group and the obtained clusters are proposed and discussed. The results confirm that the obtained spectral ordinated from GMPEs of different clusters can meaningfully differed from each other.

Observations from past earthquakes in addition to the results from analytical and numerical studies have shown that topographic irregularities significantly affect seismic site responses. Nonetheless, few studies have focused on the effect of topography amplification on the seismic vulnerability of buildings adjacent to slopes. In this study, using “match up damage index to damage thresholds” method introduced in HAZUS, fragility curves were developed for steel moment-resisting frames (SMRF) built adjacent to slopes. A two-dimensional finite-element model of the soil was implemented in ABAQUS to develop the fragility curves. Six models of combination of soil-structure and topography were considered. Furthermore, three types of buildings at different distances from the crest of the slope were considered. The results indicated that slope effect leads to up to 37% increase in the damage probability and illustrated that amplification factor had a range of 1.1 to 1.35, moreover, in comparison with slight states, the probability damage growth rate in moderate and extensive states are higher.

Recovery and post-recovery stages are crucial parts of a risk management system to achieve several to return the affected area to pre-disaster stage after the catastrophe, to organize essential elements for the prevention of the next disaster, and to increase the capacity of the society. It is important to evaluate the functionality of this stage in any reconstruction program. This paper makes an effort to study the long-term results of reconstruction and recovery (recovery for short) efforts after 1990 Rudbar-Manjil Earthquake in Iran. It both evaluates the vulnerability of the existing buildings and, based on that, evaluates region’s safety. Two separated analyses have been used for the evaluation of buildings’ vulnerability: 1) survey of random buildings, and 2) the regional analysis. The results indicate that two decades after the event; more than 80% of existing buildings are still seismically vulnerable and show that recovery efforts has failed to improve the region’s safety. In this investigation, to establish a safe development culture in after future disaster, it is proposed to have a pre-designed recovery plan with following strategies: 1) Maximum use of local construction technology and technique in the recovery stage. 2) Designing a comprehensive and steady educational program to teach the safe and new methods of reconstruction to local workers. 3) Creation and promotion of an effective system of supervision

According to the modern seismic design codes, the structural collapse is a catastrophic state which is not acceptable, even under very rare earthquakes. Hence, evaluation of collapse safety margin for structures design based on code requirements is very important. The paper tackles this issue considering RC frame structures designed according to Iranian seismic standard (Standard 2800). Incremental Dynamic Analysis (IDA) is carried out using 22 natural ground motion records. The study includes RC moment resisting frames with 3, 6 and 10 stories considering two types of soil classifications (Type II and III) and two alternatives of ductility levels (intermediate and high), as defined in standard 2800. It is concluded that while all structures on the sites with soil class II demonstrate sufficient margin against collapse, taller structures on soil class III show lower than acceptable collapse margin. It is also noted that the collapse margin is generally reduced with the increased height of the structure.