Vol.39/No.4 (154) (2024)

This research develops a seismic analysis auxiliary program for structures. The main objectives are (1) to provide automation assistance for input file of TEASPA (Taiwan earthquake assessment and strengthening of structures by pushover analysis) V3 and V4 developed by the National Center for Research on Earthquake Engineering, such as calculating the effective flange width of beams, the effective length of beams and columns, adjusting the plastic hinge position of windowsill columns, etc. This aims to reduce the tedious input work and minimize human errors for engineers. (2) Based on the theory of TEASPA V4, a modified model for column plastic hinges is proposed. It offers automated calculation of nonlinear hinge parameters, addressing to improve the slow convergence in using P-M interaction plastic hinges for columns. This modification also enables users of ETABS versions with only M3 plastic hinge function to conduct seismic assessments for high-rise buildings according to TEASPA V4. In modified P-M column hinges, the seismic-induced moment and axial force are assumed to increase proportionally. The corresponding axial force at the yield point of the P-M curve is determined, and the capacity of the column is calculated based on this force. Additionally, the program provides a function for determining seismic capacity using the ATC-40 capacity spectrum method or the method based on design code, obtaining seismic performance corresponding to different ductility. Two buildings are analyzed as examples, and the results are compared against TEASPA V3 and V4, including base shear strength, seismic performance, and discussions on failure modes to validate the accuracy of this program. The program can be downloaded at:                          https://teaspa.ncree.org.tw/Home/ DownloadFile/13

It has been shown that the current formula for predicting the shear strength of masonry window spandrel may not be reliable. Thus, a series of cyclically loading tests were conducted for the reinforced concrete (RC) frames with different heights of masonry window spandrels and then a new formula is proposed to predict the shear strength. Herein, a further study is focused on the effect of using these new and old formulas in pushover analysis of old RC buildings with masonry window spandrel. The results reveal: (1) The use of the old formula for high masonry window spandrel may underestimate its shear strength. Hence, it might be damaged first and there is no short column failure. As a result, the performance-target ground acceleration (Ap ) of the building under analysis will be overestimated; (2) There is no significant difference in Ap value for using either new or old formula if the building has low masonry window spandrel; (3) Some masonry window spandrels look like high masonry window spandrels and it is expected that a short column failure will occur for the RC building under analysis. However, it shows no short column failure. This is because these masonry window spandrels are low masonry window spandrels because they may have a large width or their brick bond has a large critical failure angle. Since the old shear strength formula underestimates the shear strength of the high masonry window spandrels, it is likely to cause these high masonry window spandrels fail first without short column failure in the pushover analysis. Consequently, the Ap value is overestimated. Thus, buildings with insufficient seismic resistance cannot be detected early. Based on this, it is strongly recommended that the authority should revise the old shear strength formula for masonry window spandrel to improve the reliability of seismic evaluation of RC buildings.

As one of the major disasters on earth, earthquakes and their impacts cover a wide range of social, economic, and environmental aspects. However, forecasting earthquakes is currently impracticable, so many researchers have adopted various measures to cope with possible earthquake effects, such as earthquake early warning (EEW), structural health monitoring (SHM), earthquake-resistant structures, etc. This development allows us to respond to events and reduce impacts quickly. Although those advances are successful, they heavily rely on the availability and variety of earthquake data, which is often limited for large earthquakes or areas that are not earthquake-prone. Therefore, not much earthquake data can be used for structural analysis due to the deficiency of observation. In order to address this issue, this study introduces the variational autoencoder (VAE), a machine learning (ML) based approach. VAE is a generative model capable of automatically extracting the seismic features and reproducing the earthquake data. Moreover, it can generate artificial earthquake waveforms with diversity by using the extracted features, which provides a new way to synthesize waveforms. In this study, the 921 earthquake was first adopted, and a total of 293 waveforms were used for training. The preliminary results show that VAE is great while generating artificial earthquake waveforms. Subsequently, VAE is applied to the earthquake data from seven regions in Taiwan, and the final results verify the feasibility. As a result, VAE can provide merits for the development of structural and earthquake engineering, and the paper ends by suggesting future research.

Large-scale testing machines with dynamic compression and shear testing capabilities play a crucial role in developing seismic isolation technology and testing full-scale seismic isolators. However, to date, relatively little research has been conducted on its dynamic performance verification and system parameter identification. Only a few studies have established the empirical model to predict the relationship between system friction and peak velocity of the Caltrans seismic response modification device (SRMD) test system in the University of California, San Diego (UCSD), based on the various characterization testing. To support academia and industry, the dynamic characteristics of the biaxial dynamic testing system (BATS) at the National Center for Research on Earthquake Engineering (NCREE) must be thoroughly investigated. When no specimens are installed, the system friction of BATS generated by the various sliding surfaces can be identified and mathematically characterized using the horizontal triangular reversed loading test results; then, the effective mass of BATS can be estimated using the horizontal sinusoidal reversal loading test results to solve the inertia force problem. Under vertical compression loading, it is assumed that the system friction of BATS and the shear force of the specimen are simply related to the applied total normal force (or vertical compression load) and horizontal excitation rate. An iteration methodology is proposed to identify and mathematically describe the dependency of the friction performance of BATS and the specimen on total normal forces (or vertical compression loads) and horizontal excitation rates by iterating the horizontal triangular and sinusoidal reversed loading test results. To simplify the tests, a lubricated flat sliding bearing is used as the specimen, subjected to horizontal triangular and sinusoidal reversed loading with a constant vertical compression load. The reliability of the proposed mathematical model for BATS and the feasibility of the proposed direct force measurement strategy are further demonstrated by comparing the calibrated force response with the directly measured response.