Serdar Soyoz

Dynamic and cyclic response of a full-scale 2-storey cold-formed steel structure with and without infill materials

Cold-Formed Steel (CFS) has become more and more popular in recent years as an alternative construction material. Short construction time and very high strength to weight ratio under lateral forces made cold-formed steel an attractive option in earthquake prone countries such as Japan, New Zealand and the US. These structures are formed of CFS frames with either boards and sheatings attached to the frames or infill materials sprayed to the frames on-site. This paper presents the results of dynamic and cyclic experiments conducted on two different 3-D and 2-storey models. The first model was CFS frame system without infill material and the second one was with infill material. In order to identify the actual dynamic characteristics of models such as modal frequencies and damping ratios, large-scale tests are conducted instead of 2-D panel tests. Ambient vibration tests were carried out to determine modal frequencies of the models at different damage states and forced vibration tests were carried out to determine modal damping ratios at high vibration levels. In addition to ambient and forced vibration tests, cyclic tests were performed to obtain the hysteretic behavior of the model. It was observed that with the application of infill material, lateral load resisting capacity increased by 3.5 times, ductility of the model increased from 2.58 to 3.96 and damping ratio increased from 6.7 to 9.0%. In addition to identification of dynamic characteristics, the main motivation of this study is to investigate the possible use of ambient vibration surveys in the determination of damage level. Results showed that ambient vibration surveys can be used as a damage detection tool after an earthquake or any other hazard.

In-Plane Seismic Response Analyses of a Historical Brick Masonry Building Using Equivalent Frame and 3D FEM Modeling Approaches

ABSTRACT This article aims at contributing to the seismic performance assessment of a historic brick masonry building by finding a strength reduction coefficient through the use of linear and nonlinear modeling approaches, using Finite Element Method and Equivalent Frame modeling. To reduce the uncertainties, ambient vibration tests (AVT) were implemented. Series of simulations was performed using nonlinear dynamic analyses and incremental dynamic analysis curves were compared with the pushover curves. Results indicate that the mass-proportional pushover curve meets the mean of results obtained from IDA and the strength reduction coefficient falls into the range given in EN 1998–1 for unreinforced masonry.

Quantifying the value of SHM for emergency management of bridges at-risk from seismic damage based on their performance indicators

This paper proposes a framework for quantifying the value of information that can be derived from a structural health monitoring (SHM) system installed on a bridge which may sustain damage in the mainshock of an earthquake and further damage in an aftershock. The pre-posterior Bayesian analysis and the decision tree are the two main tools employed. The evolution of the damage state of the bridge with an SHM system is cast as a time-dependent, stochastic, discrete-state, observable dynamical system. An optimality problem is then formulated how to decide on the adoption of SHM and how to manage traffic and usage of a possibly damaged structure using the information from SHM. The objective function is the expected total cost or risk. The paper then discusses how to quantify bridge damage probability through stochastic seismic hazard and fragility analysis, how to update these probabilities using SHM technologies, and how to quantify bridge failure consequences.