Journal of Numerical Methods in Civil Engineering
Volume:6 Issue: 3, Mar 2022

One of the key parameters in climate change is Precipitable Water Vapor (PWV) which plays an important role in identifying precipitation distribution, hydrological cycles and important meteorological and climatic phenomena. Therefore, it is important to study the long-term changes in PWV time series in an area. MODIS near-infrared PWV product (MOD-NIR-PWV) provides a suitable spatial coverage of PWV with a resolution of 1 km and temporal resolution of 1 day. This study compares statistically the time series of MODIS PWV from 2000 to 2018 with radiosonde values. MODIS data under cloudless conditions at a maximum distance of 1 km from the position of the radiosonde station were used for statistical analysis. The results show that the consistency between two sets of water vapor data in terms of correlation coefficient was obtained at 0.81, 0.78 and 0.67 in Tehran, Isfahan and Mashhad stations, respectively. Also, the linear trend of PWV time series in the study areas was investigated using Mann-Kendall (MK) statistical test. PWV values in both datasets have undergone similar trends, according to time series analysis of radiosonde and MODIS. Therefore, free remote sensing methods such as MODIS products along with local data can be used for long-term studies of PWV to study the trends of the PWV parameter. Furthermore, a decrease in precipitation and an increase in surface temperature along with an increase in the PWV value of MODIS data was observed in studies with synoptic data in the studied stations, which may in some way reflect the effects of global warming in the studied stations.

In the present research, behavior of SPSPs with two rectangular openings and effect of strengthening different subpanels with various stiffener arrangements is investigated. In the next step, to investigate the effect of changing opening width on the trend of degradation shear stiffness and strength of the panel, the opening width is changed. In the third step, to study the effect of changing opening height on the behavior of the whole panel, the opening height is changed. Based on the results obtained, it is observed that for SPSPs with constant plate thickness and opening dimensions, strengthening various subpanels with different stiffener arrangements has no effect on the values of shear stiffness of the panel, and only the shear strength of the panel is changed. In the case of panels with constant opening dimensions and plate thickness and stiffened corner panels (height of subpanels equal to opening height), changing the number of horizontal and vertical stiffeners to stiff corner panels with different stiffener arrangements, has no effect on shear stiffness. Only the shear strength is changed in these models. For SPSPs with constant opening dimensions and constant plate thickness and different stiffener arrangements to stiff corner panels, by increasing number of both horizontal and vertical stiffeners, no changes on the shear stiffness is created, and its effect on the value of shear strength is negligible. However, using L3T3 and L1T0 stiffener arrangements result in obtaining maximum and minimum values of shear strength, respectively. In addition, the effect of changing opening width in the SPSPs with constant opening height and also the effect of changing opening height in the SPSPs with constant opening width on the values of shear strength and stiffness of the specimens is investigated.

Rapid evaluation of demand parameters of different types of  buildings is crucial for social restoration after damaging earthquakes. Previous studies proposed numerous methodologies to measure the performance of buildings for assessing the potential risk under the seismic hazard. However, time-consuming Nonlinear Response History Analysis (NRHA) barricaded implementing a prompt loss estimation for emergency confronting actions. The present study proposes a swift framework for demand estimation in concrete moment-resisting buildings using artificial neural networks. For this purpose, a simplified model is developed based on the HAZUS method. To eliminate the required time-consuming NRHA from the post-earthquake actions, Artificial Neural Networks (ANNs) are used. Before the event, ANNs are studied to estimate the demand parameters using a set of time-history analyses. This study applies to a suite of 111 earthquake events, originally developed in the SAC project and uniformly scaled from 0.1 g to 1.5 g , to achieve a generalized prediction model. Bayesian Optimization (BO) algorithm is carried out to tune the architecture of the NNs. Results reveal that the presented approach is reliable for predicting the structural response, and is cost-effective compared to the conventional NRHA. This framework can be implemented in the body of a risk assessment platform to expedite the postearthquake actions required for crisis management.

In this article, to study the effect of pulse-type near-fault earthquakes on the seismic demands of steel moment frames, 15-story 2D-frame was analyzed under the influence of 20 near-fields with forward directivity effect and 2 far-field records. The relationship between Effective Cyclic Energy, ECE and displacement demands, velocity and hysteretic curve of SDOF systems in two near- and far-fault earthquake was evaluated. Then, by examining the relative and absolute cumulative input energy history along with the kinetic energy in one section and the maximum inter-story drift for 4 different levels of nonlinear behaviour (R = 1.0, 2.0, 4.0, and 6.0) in a section, the effect of higher modes was evaluated. The study of inter-story drift profile for two near-fault earthquakes with and without visible pulse indicated the formation of maximum drift concentration, IDRmax, in the upper stories for low nonlinear degrees in record with visible pulse, which itself is an indication of its effect on higher mode contribution. However, in the pulse-free records, in addition to IDRmax intensification in the upper stories, the lower stories also have large structural demands. In other words, in these records, in the lower stories, mainly the dynamic instability is involved.

In Iran and some other countries, elastomer bearings in seat-type bridges are used with no sole/masonry plates and there is no positive connection between superstructure and substructure. Different codes have diverse provisions regarding the coefficient of friction (μ) between elastomer bearing and superstructure/substructure and also the design strength of shear keys (Vsk). Developing a finite element model for bearing slip, this paper investigates how different assumptions for μ and Vsk could affect the seismic performance. Incremental dynamic analysis is used to investigate the probability of unseating, residual displacement and nonlinear deformation in the substructure on a prototype three-span bridge. While performance during past earthquakes is fairly good, evaluating response using codes’ recommended value, i.e., μ=0.2, leads to an unacceptably high probability of unseating. Regarding design strength of shear keys, it is shown that design for weak shear keys could lead to relatively large transverse displacement during small to large earthquakes, and on the other hand, strong shear keys does not provide better protection against large transverse displacement during intense ground shakings.

The incidence angle of seismic waves affects the maximum response of bridges. Furthermore, long-span structures experience different seismic excitations at supports because of the spatial variability of ground motions. Moreover, for curved bridges, because of the irregular shape and the interaction between bending and torsion, the maximum response of the structure would be correlated to the input angle of the earthquake. In this study, the dynamic response of a long-span reinforced concrete curved bridge under asynchronous input motions for different inclinations of seismic incidence was investigated. For the numerical study, a curved plan bridge from the Caltrans bridges portfolio is selected and analyzed for various load and soil scenarios. The correlated arrays are generated by the method described in the paper and implemented to investigate the bridge. From the outcomes, the directionality effect of ground motions is evident that the responses change corresponding to the input angle of the seismic wave. For the case of multiple support excitations, the maximum response is different from the uniform load pattern. Finally, to find the most unfavorable input angles, an incremental dynamic analysis was performed. The results showed that the maximum response for each column occurs for different angles of earthquake incidence. The results showed that the responses of the structure increased under some angles of incidence. Additionally, responses from multiple-support were more varied in comparison with uniform excitations under different input angles, and in some cases larger than the responses caused by uniform excitations.

In recent years, there has been a growing seismic demand for existing bridges and the final redesign of bridges, especially after a major earthquake One method to strengthen concrete frames on bridges is to use steel sheets or profiles to use the confining force. During this study, a sample at 30% scale under gravity and lateral cycle loading was examined within the laboratory. A finite element model is additionally used to compare the behavior of laboratory samples. The laboratory sample was a model of a typical bridge in iran that was generally designed with deficient detailing requirements in agreement with the typical regulations of the 1970s. A finite element analysis set was used to evaluate various parameters in improving the behavior of the laboratory sample. The finite element model correctly predicted the weakness of the model. Subsequently, a reinforced specimen was investigated by increasing the prestressing force within the concrete beam and the thickness of the frp sheets utilized in the bridge pier by the finite element method. The results show the energy absorbed within the hysteresis curves improved the propagation of the failure. The  result also  showed that  a 100% increase in the prestressing load caused a 67% increase in resistance .

The present paper establishes the Flanged reinforced concrete (RC) Shear Wall Laboratory (FlashLab) Software Program. Despite their extensive applications in recent years, flanged RC shear walls have rarely been experimentally and numerically studied, mainly due to the difficult and time-consuming fabrication of experimental samples, numerical models, and also their analysis. FlashLab is a finite element method (FEM)-based simulator of flanged RC shear walls. Drawing on ABAQUS, FlashLab employs shell elements with longitudinal and transverse reinforcements to accurately and rapidly model the cyclic behavior of flanged RC shear walls. The FlashLab algorithms are on the basis of the Python programming language and can examine flanged RC shear walls, with a general cross-section, which make it possible to parametrically investigate various variables. In order to validate FlashLab, this paper numerically simulates T-, H-, and L-shaped RC shear walls and compares the results to the experimental data, indicating good agreement between the numerical and experimental results to an extent that the proposed numerical laboratory is capable of predicting the backbone curve with an accuracy more than 90 percent. Moreover, to verify the simulation performance of FlashLab, the shear-lag effect was parametrically studied as a unique phenomenon in flanged RC shear walls. The findings of the current study clearly demonstrates the robustness and efficiency of FlashLab in the behaviour simulation of flanged RC shear walls.