Seismic Collapse Probability and Life Cycle Cost Assessment of Isolated Structures Subjected to Pounding With Smart Hybrid Isolation System Using a Modified Fuzzy Based Controller

The possibility of pounding on isolated structures with surrounding moat walls is one of the concerns in the design of isolation systems, especially in pulse-type near-field earthquakes. This paper puts forward the seismic probability assessment of structures equipped with passive and smart hybrid isolation systems by considering pounding possibilities. This investigation is performed on isolated structures equipped with a high damper rubber bearing (HDRB) considering stiff moat walls around the structure. In the Hybrid isolation system, magnetorheological dampers (MR) are considered an adaptive dissipation energy device along with isolators using an optimized novel interval Type-2 fuzzy logic controller with adaptive red-zone function (IT2FS+RZF) to reduce pounding possibilities. The fragility curves of the building for various cases are determined using IDA analysis, and possible damage costs are evaluated by using exceedance probability in each damage level. This study concludes that the collapse probability of the isolated structures with restrains at the code-based distance is over the acceptable limit of ASCE 7-22. The smart additional damping system with the proposed controller reduces the possible damage cost of the building by about 64% compared to the uncontrolled system and puts the collapse probability of the structure in the acceptable range.

Collapse Probability of Immediate and Special Moment Frames in Tehran under MCE

Residential buildings in most cities, which make up the most significant percentage of buildings, generally contain the most financial and human losses in the face of strong earthquakes. The purpose of this study is to investigate the possibility of the collapse of intermediate and unique steel moment frames against maximum ground excitations. In this study, through the first two steps of PEER methodology, using four steel structural frames with intermediate and unique moment frames, after designing according to the codes of national building regulations of Iran and standard 2800, this probabilistic evaluation was used to ensure their safety against collapse. In the next step, to deepen the results, 7 other sites from Tehran were selected. Their hazard spectrum was used to calculate the probability of collapse. In the end, it was observed that, with the reduction of the number of structural floors, the IDA curves at the lower IM level become horizontal in this project. The results showed that some of the 5-story steel structures under study in some parts of Tehran have a higher probability of collapse than acceptable.

Effect of Aftershock Characteristics on the Fragility Curve of Post-Mainshock RC Frames

Buildings constructed in seismic zones are not only damaged by mainshocks but may also be damaged by the impact of aftershocks and cause them to collapse. Therefore, studying the behavior of the damaged structures due to the mainshock and aftershock helps in post-mainshock decision making and also in the selection of suitable aftershock records for seismic assessing of the structure under earthquake sequences. This paper presents the effects of aftershock ground motion on the collapse capacity of post-mainshock buildings. The mean period (Tm), predominant velocity period (Tg), frequency bandwidth (Ω), the 5%-95% significant duration (Ds) and seismic records of different sites were selected to evaluate the effect of its characteristics on the collapse capacity of buildings. The intensity of the ground motions was determined by the first-mode spectral acceleration with 5% damping. Collapse capacities of two non-ductile reinforced concrete (RC) frames with 3 and 6 stories were evaluated using a set of 62 aftershock records with a wide range of characteristics. Box plot collapse diagrams and fragility curves have been developed by applying the incremental dynamic analysis (IDA). The results show that in the frequency content with a longer period, the probability of its collapse is higher. In addition, the high significant duration of aftershocks increases the collapse probability of structures. Also, the evaluation of the site characteristics shows differences in collapse capacities of the same frames in varying sites. Therefore, the effect of aftershock characteristics on the capacity of the structures is significant and it is necessary to carefully determine the seismic sequences’ recordings for the evaluation of the seismic behavior of the structures.

Seismic collapse safety of reinforced concrete moment resisting frames with/without beam-column joint detailing

FEMA-P695 procedure was applied for seismic collapse safety evaluation of reinforced concrete moment resisting frames with/without beam-column joint detailing common in Pakistan. The deficient frame lacks shear reinforcement in joints and uses concrete of low compressive strength. Shake-table tests were performed on 1:3 reduced scale two-story models, to understand the progressive inelastic response of chosen frames and calibrate the inelastic finite-element based models. The seismic design factors i.e. response modification coefficient, overstrength, ductility, and displacement amplification factors (R, W0, Rμ, Cd) were quantified. Response modification factor R = 7.05 was obtained for the frame with beam-column joint detailing while R = 5.30 was obtained for the deficient frame. The corresponding deflection amplification factor Cd/R was found equal to 0.82 and 1.03, respectively. A suite of design spectrum compatible accelerograms was obtained from PEER strong ground motions for incremental dynamic analysis of numerical models. Collapse fragility functions were developed using a probabilistic nonlinear dynamic reliability-based method. The collapse margin ratio (CMR) was calculated as the ratio of seismic intensity corresponding to the 50th percentile collapse probability to the seismic intensity corresponding to the MCE level ground motions. It was critically compared with the acceptable CMR (i.e. the CMR computed with reference to a seismic intensity corresponding to the 10% collapse probability instead of MCE level ground motions). Frame with shear reinforcement in beam-column joints has achieved CMR 11% higher than the acceptable thus passing the criterion. However, the deficient frame achieved CMR 29% less than the conforming frame. This confirms the efficacy of beam-column joint detailing in reducing collapse risk.

A New Approach for Probabilistic Risk Assessment of Ship Collision with Riverside Bridges

The configuration of riverside bridges, such as the spatial distribution, wading status, and ship accessibility of piers, is generally different from river-crossing bridges. Thus, the ship collision risk of riverside bridges cannot be assessed using conventional assessment methods applicable to river-crossing bridges. The aim of this paper is, therefore, to develop a new probabilistic method for assessing the risk of ship collision with riverside bridges. First, a fully probabilistic framework for assessing the ship-bridge collision risk is presented. Second, a new probabilistic hazard analysis model of ship collision with riverside bridges is proposed, based on a combined study of riverside bridge characterization and an improved yaw ship collision model. A simplified empirical model for evaluating ship-bridge collision force is then adopted, and the probabilistic distribution of the collision force is obtained based on Monte Carlo simulation. Furthermore, finite element simulation is conducted to estimate the collapse probability of piers. Finally, the method developed is applied to the probabilistic assessment of ship collision risk with riverside bridges located at Shabin Road, Chongqing, China. The results show that the risk of ship-bridge collision at Shabin Road is low to moderate. The example demonstrated indicates that the methodology introduced in this paper is capable of assessing the ship-bridge collision risk in a concise and rapid way.