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This paper presents an investigation of the seismic behavior of reinforced concrete (RC) structures in which shear walls are the main lateral load-resisting elements and the participation of flat slab floor systems is not considered in the seismic design procedure. In this regard, the behavior of six prototype structures (with different heights and plan layouts) is investigated through nonlinear static and time history analyses, implemented in the OpenSees platform. The results of the analyses are presented in terms of the behavior of the slab-column connections and their mode of failure at different loading stages. Moreover, the global response of the buildings is discussed in terms of some parameters, such as lateral overstrength due to the gravity flat slab-column frames. According to the nonlinear static analyses, in structures in which the slab-column connections were designed only for gravity loads, the slab-column connections exhibited a punching mode of failure even in the early stages of loading. However, the punching failure was eliminated in structures in which a minimum transverse reinforcement recommended in ACI 318 (2019) was provided in the slabs at joint regions. Furthermore, despite neglecting the contribution of gravity flat slab-column frames in the lateral load resistance of the structures, a relatively significant overstrength was imposed on the structures by the gravity frames. [ABSTRACT FROM AUTHOR]

This paper presents an air-coupled impact echo (IE) technique that relies on the phase spectrum of the collected data to find the frequencies corresponding to the reflections from delaminations. The proposed technique takes advantage of the fact that the IE compression wave is not a propagating wave, but it is the 1st order symmetrical (S1) mode Lamb wave at zero group velocity (S1-ZGV). Therefore, it searches the phase spectra of the data collected by multiple sensors to locate the frequency corresponding to the lowest phase difference. As a result, the technique reduces the effect of propagating waves, including the direct acoustic wave and ambient noise. It is named the Constant Phase IE (CPIE). The performance of the CPIE is experimentally compared with the regular amplitude spectrum-based IE technique and two other multisensor IE techniques. The CPIE shows a performance advantage, especially in a noisy environment. [ABSTRACT FROM AUTHOR]

As an important part of nonstructural components, the seismic response of indoor water supply pipes deserves much attention. This paper presents shaking table test research on water supply pipes installed in a full-scale reinforced concrete (RC) frame structure. Different material pipes and different methods for penetrating the reinforced concrete floors are combined to evaluate the difference in seismic performance. Floor response spectra and pipe acceleration amplification factors based on test data are discussed and compared with code provisions. A seismic fragility study of displacement demand is conducted based on numerical simulation. The acceleration response and displacement response of different combinations are compared. The results show that the combination of different pipe materials and different passing-through methods can cause obvious differences in the seismic response of indoor riser pipes. [ABSTRACT FROM AUTHOR]

This paper presents a new finite element model updating method for estimating structural parameters and detecting structural damage location and severity based on the structural responses (output-only data). The method uses the sensitivity relation of transmissibility data through a least-squares algorithm and appropriate normalization of the extracted equations. The proposed transmissibility-based sensitivity equation produces a more significant number of equations than the sensitivity equations based on the frequency response function (FRF), which can estimate the structural parameters with higher accuracy. The abilities of the proposed method are assessed by using numerical data of a two-story two-bay frame model and a plate structure model. In evaluating different damage cases, the number, location, and stiffness reduction of the damaged elements and the severity of the simulated damage have been accurately identified. The reliability and stability of the presented method against measurement and modeling errors are examined using error-contaminated data. The parameter estimation results prove the method's capabilities as an accurate model updating algorithm. [ABSTRACT FROM AUTHOR]

Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions. Due to the unique marine depositional environment of coral sandy soils, the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering communities. This paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three decades. The focus of coverage includes the contractive-dilative behavior, the pattern of excess pore-water pressure (EPWP) generation and the liquefaction mechanism and liquefaction resistance, the small-strain shear modulus and strain-dependent shear modulus and damping, the cyclic softening feature, and the anisotropic characteristics of undrained responses of saturated coral sandy soils. In particular, the advances made in the past decades are reviewed from the following aspects: (1) the characterization of factors that impact the mechanism and patterns of EPWP build-up; (2) the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient; (3) the establishment of the invariable form of strain-based, stress-based, or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction; (4) the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus; and (5) the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation characteristics. Insights gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjected to cyclic loadings associated with seismic events in marine environments. [ABSTRACT FROM AUTHOR]