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The use of longer and deeper precast concrete girders has created concern regarding their rollover instability, particularly during construction. Current design and construction specifications do not provide any specific guidelines that can be used to evaluate the rollover instability of a girder. Therefore, analytical and simplified numerical studies were performed to evaluate the critical wind load, lateral displacement and rotational angle that would induce rollover instability of a girder supported on an elastomeric bearing pad. The influence of the length and section properties of the girder on rollover instability was also investigated. The analytical method proposed in this study can be effectively used for evaluating the lateral behaviour and rollover instability of bridge girders and can also provide management values for securing the lateral stability of girders. The paper also provides a worked problem for a long-span typical European girder to determine critical values with application of the proposed method.

Summary In suspension bridges, hanger cables are the main load‐supporting members. The tension of the hanger cables of a suspension bridge is a very important parameter for assessing the integrity and safety of the bridge. In general, indirect methods are used to measure the tension of the hanger cables of a suspension bridge in use. A representative indirect method is the vibration method, which extracts modal frequencies from the cables' responses and then measures the cable tension using the cables' geometric conditions and the modal frequencies. In this study, ambient vibration tests were conducted on a suspension bridge in use to verify the validity of the image‐based back analysis method, which can estimate the tension of remote hanger cables using the modal frequencies as a parameter. The tension estimated through back analysis, which was conducted to minimize the difference between the modal frequencies calculated using finite element analysis of the hanger cables and the measured modal frequencies, was compared with that measured using the vibration method. It was confirmed that reliable tension estimation is possible even with low‐order modal frequencies when the image‐based back analysis method is used.

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In this study, dynamic characteristics and seismic capacity of the nuclear power plant piping system are evaluated by model test results using multi-platform shake table. The model is 21.2 m long and consists of straight pipes, elbows, and reducers. The stainless steel pipe diameters are 60.3 mm (2 in.) and 88.9 mm (3 in.) and the system was assembled in accordance with ASME code criteria. The dynamic characteristics such as natural frequency, damping and acceleration responses of the piping system were estimated using the measured acceleration, displacement and strain data. The natural frequencies of the specimen were not changed significantly before and after the testing and the failure and leakage of the piping system was not observed until the final excitation. The damping ratio was estimated in the range of 3.13 ~ 4.98 % and it is found that the allowable stress(345 MPa) according to ASME criteria is 2.5 times larger than the measured maximum stress (138 MPa) of the piping system even under the maximum excitation level of this test.

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