International Journal of Earthquake and Impact Engineering (8 papers in press)
New Approach in Simulation of Soil-Structure Interaction (SSI) Problems Including Damper Effects
by Kemal Edip, Aleksandra Bogdanovic, Marta Stojmanovska, Angela Poposka, Ehsan Noroozinejad Farsangi
Abstract: In this paper, numerical simulation of the issues related to soil-structure interaction (SSI) in the structures equipped with prestressed damping device (PDD) is presented. More specifically, this research examines the impacts of dampers on the interaction between the soil and the structure, considering a variety of conditions, including the effects of the soil boundaries simulated by infinite elements. Comparative analysis of the results with different disposition of the dampers is made using ANSYS nonlinear platform. It could be observed from the results of the numerical analysis that regarding the impact of dampers in the structure on SSI, the selection of the damper type has a significant role.
Keywords: Soil-Structure Interaction; Seismic Excitations; Prestressed Damping Device (PDD); Boundary Conditions; Infinite Element.
The Response of Tall Buildings to Far-Field Earthquakes and the Case of a 49-Story Steel Building
by Sifat Muin, ABOLHASSAN ASTANEH-ASL, C.E.M. TOPKAYA
Abstract: This paper investigates the seismic response of an instrumented 49-story steel structure in San Francisco to weak, far-field, and strong, near-field ground motions. The instrumentation records obtained during the 1989 Loma Prieta earthquake are used to verify the accuracy of the predictions of the time-history analysis of the model. The Chi-Chi-002 ground-motion record from the 1992 Chi-Chi earthquake in Taiwan, (PGA=0.08g) representing a weak, far-field earthquake and the record from the 1994 Northridge Newhall earthquake (PGA=0.60g) representing a strong, near-field earthquake were used in the study. The results showed that the force, acceleration, and displacement responses of this long-period structure to the weak far-field ground motion is much larger than its response to the strong, near-field ground motion. Also, the response attenuates at a slower rate for the weak, far-field earthquake, indicating the possibility of greater damage, both to structural and non-structural elements, during the earthquake. Interim seismic design recommendations are formulated to address this issue in the design of tall buildings with long periods.
Keywords: structural engineering; earthquake engineering; the design of steel structures; nonlinear time-history analysis; seismic design; tall buildings; instrumented buildings; far-field earthquakes; near-field earthquakes; dynamic resonance; long-period motion; seismic performance; drift control; seismic response.
Prediction Accuracy of Underground Blast Variables: Decision Tree and Artificial Neural Network
by Saha Dauji
Abstract: Accurate prediction of blast induced ground vibration variables pertaining to particle velocity and frequency are of interest for design of controlled blasting operations for mining, tunnelling or excavation projects. The safety of the adjacent structures and installations are of particular concern in underground blasting operations in built environments and this can only be ensured with prediction of the particle velocity and frequency with good precision. Empirical and numerical approaches are widely reported in literature. These methods have inherent limitations especially when number of variables is large. Data driven approaches are quite adept in such scenarios for producing correct estimates. Different data driven tools such as artificial neural network (ANN), genetic programming, gene expression program, adaptive neuro-fuzzy inference system, support vector machine (SVM), and random forest (RF) have found application in blast related predictions, with various degrees of success. Decision tree (DT) has been successfully employed for solution of various civil engineering problems, and its superiority has already been established in certain problems compared to the universally popular ANN. In this article, DT is employed in prediction of blast variables for the first time. Furthermore, whether DT would be comparable or preferable to the other soft computing tools in this domain is critically examined. The performance of DT models was found to be equally good (for particle velocity variable) or better than (for frequency variables) ANN models developed in this study, and unequivocally superior to the SVM or RF models reported in literature for the same set of data. Additionally the clarity in decision rule based estimation foster easy comprehension and future implementation.
Keywords: Underground blast; Decision tree; Artificial neural network; Ground vibration;.
Probabilistic Seismic Hazard Assessment of District Headquarters of Kashmir Valley in Jammu and Kashmir, India
by Fida Anjum, Shaista Jan, Yawar Mushtaq Raina
Abstract: This study aims at characterizing the probable 99 faults of region by carrying out the probabilistic seismic hazard analysis for different districts of Kashmir valley by preparing seismic hazard curves and the contour maps of three ground motion parameters, namely, peak ground acceleration (PGA), short period Sa (0.02 s) and long period Sa (1.0 s) spectral acceleration for 50, 100, 500 and 2500 year return periods using the Atkinson and Boore (2006) GMPM and an updated catalogue containing event records till April 2018. On comparisionwith the earlier studies it was found that there is the need to consider the local site variability in the hazard computation. Shopian, Budgam, Baramulla and Kupawara were found to have much higher seismic hazard levels as compare to other districts. The estimated hazard values for these regions highlights that the zonal spectral values are underestimated in the Indian codal provisions. The maps, hazard curves and UHRS so developed can be used for assessing the seismic vulnerability of the existing structures and constructing risk maps for the selected areas.
Keywords: Seismicity; Earthquake; Kashmir Valley; Faults; Contour Maps; Himalaya; Rocks; peak ground acceleration; short period; long period; spectral acceleration.
Quasi-static Tests on 1:3 Scaled Arch Segments of the of the Old Bridge in Mostar
by Mladen Kustura, Goran Šunji?, Dragan ?ubela
Abstract: Abstract: Masonry stone arch, and other types of masonry structures, owed their durability through the centuries primarily to the inventiveness of the builders, who, by introducing new connection elements, managed to build structures that would resist various effects through the time. Connection elements used for assembling bridge vaults, or clamps and dowels made of wrought iron with the additional use of liquid lead and mortar, are one of the successful ways to increase stability and load-bearing capacity of this type of structures. A similar assembly technique was applied during construction of the original Old Bridge in Mostar in 1566 and its reconstruction in 2004. This paper presents experimental tests performed on 1:3 scaled arch segments of the Old Bridge in Mostar and obtained results. This experimental research was conducted in order to describe the behavior of all connection elements participating in the transfer of loads that can occur. Obtained results of the performed experimental tests are highly utilizable for further numerical analyses and verification of the existing and new mathematical models.
Keywords: masonry arch; connection elements; quasi-static laboratory tests; failure mechanism; loosening of connection.
Verifying the Periods of Vibration for Different Structural Systems using Earthquake Data and Simulation
by Aman Mwafy, Aya AbouElhamd, Suliman Gargoum
Abstract: Although expressions for evaluating the fundamental period were recommended by building codes and previous studies, further research is still needed to evaluate the design formulas based on updated data collected from both instrumented structures and dynamic response simulation of realistic buildings. In this study, large fundamental period data from two sources are collected and compared with different expressions from building codes and previous studies. The first data set is collected from 147 instrumented buildings with various lateral force resisting systems (LFRSs). The second set is obtained from the inelastic dynamic response simulation of 26 multi-story structures. Seven LFRSs are considered, including steel moment-resisting frames (SMRFs), reinforced concrete moment-resisting frames (RCMRFs), concentrically braced frames (CBFs), eccentrically braced frames (EBFs), reinforced concrete shear walls (RCSWs), masonry buildings and pre-cast structures. The correlations between the collected period data with the code approach for predicting the fundamental periods confirm that the design provisions are conservative enough for different heights of SMRFs, RCMRFs, and CBFs in addition to EBFs higher than 40m. For low-to-medium rise RCSWs and EBFs along with low-rise masonry and pre-cast structures, recently proposed expressions in previous studies provide better conservative estimates for the fundamental periods. More data is highly needed to arrive at a reliable formula for the design of high-rise SW structures in different seismic regions. The study provides insights into the effectiveness of the current expressions for estimating the dynamic characteristics of buildings with different LFRSs and assist in arriving at a reliable and cost-effective design in earthquake-prone regions.
Keywords: Dynamic response; structural systems; buildings; fundamental period; design provisions; instrumented structures.
A New Row-Wise Parallel Finite Element Analysis Algorithm with Dynamic Load Balancing
by Ammar Al-Sayegh, Elisa Sotelino
Abstract: A parallel scheme is devised to efficiently parallelize all steps of Parallel Finite Element Analysis in this study. In addition, this scheme is based on a row-wise matrix distribution. A new Row-Wise Parallel Finite Element Analysis algorithm that exploits the nature of distributed compressed row sparse matrices and multivectors to improve concurrency is developed. A new dynamic load balancing technique has also been devised. The dynamic load balancing technique has been designed specifically to balance the computational workload among processors suitable for the analysis of nonlinear structures. This new algorithm has been implemented in ParaStruc, which is a parallel structural analysis system. Trilinos, a set of parallel numerical libraries developed by researchers in the Sandia National Laboratory has been used to build this algorithm. ParaStruc is a lightweight fully parallelized Parallel Finite Element Analysis system, which contains only three classes and a preprocessor. It is shown that this approach produces superior performance in terms of speedup, efficiency, and isoefficiency in the analysis of nonlinear structure response ranges when compared to parallel ABAQUS. The performance and efficiency of this algorithm has been verified with numerical simulations of a 200-meter 50-story 10-frame 10-bay 3-D structure subjected to various load levels.
Keywords: Structural Engineering; Structural Dynamics; Nonlinear Analysis; Finite Element Method; Parallel Computing; High Performance Computing; ABAQUS; ParaStruc.
Integrated cost-analysis approach for seismic and
thermal improvement of masonry building façades
by Linda Giresini, Simona Paone, Mauro Sassu
Abstract: The combination of structural and thermal efficiency is a new frontier in civil engineering. Indeed, the retrofitting strategies should optimize costs and technical solutions from these two points of view. If a technical solution is able to provide an improvement of both structural and energetic behavior, then the utility of the intervention can better justify the economic investment. In this paper a mesoscale approach for integrated interventions applied on masonry façades is proposed. The structural performance of the façade is evaluated by considering base shear and ductility of the structural element through non-linear static analyses. Moreover, the thermal indicator, that is the thermal transmittance, is computed with a simplified approach in terms of equivalent wall, taking into account the role of windows and doors of the façade. Economic and ecological iso-cost curves are obtained to tune the interventions conceived for a real case study, analyzing the benefit offered by different retrofitting solutions.
Keywords: Ecologic costs; economic costs; integrated approach; integrated interventions; sustainable buildings; mesoscale; cost-analysis