
 The spectral ratio between horizontal and vertical components (H/V ratio) of microtremors measured at the ground surface has been used to estimate fundamental periods and amplification factors of a site, although this technique lacks theoretical background. The aim of this article is to formulate the H/V technique in terms of the characteristics of Rayleigh and Love waves, and to contribute to improve the technique. The improvement includes use of not only peaks but also troughs in the H/V ratio for reliable estimation of the period and use of a newly proposed smoothing function for better estimation of the amplification factor. The formulation leads to a simple formula for the amplification factor expressed with the H/V ratio. With microtremor data measured at 546 junior high schools in 23 wards of Tokyo, the improved technique is applied to mapping site periods and amplification factors in the area.

Ground Motion Characteristics Estimated from Spectral Ratio between Horizontal and Verticcl Components of Mietremors.

Precast concrete facilitates a construction method using durable and rapidly erectable prefabricated members to create cost-effective and high-quality structures. In this method, the conne...

Seismic-Resistant Precast Concrete Structures: State of the Art

An experimental investigation of crumb rubber concrete confined by fibre reinforced polymer tubes

This paper presents the cyclic behavior of four self-centering bridge bents with different construction details, including external energy dissipaters and neoprene isolation. The columns of these bents consisted of precast posttensioned concrete-filled fiber tubes (PPT-CFFT). A fifth monolithic moment resisting concrete bent was also tested as a reference specimen. The tests showed that PPT-CFFT bents can be used in bridge construction as a lateral load resistance system. The PPT-CFFT bents without external energy dissipaters displayed a lateral drift of approximately 9.2% without experiencing significant damage or residual displacement. The PPT-CFFT specimen with external energy dissipaters reached a drift angle of 9.2% with some damage. The reinforced concrete specimen failed at a drift angle of approximately 6.9% with substantial damage and residual displacement.

Seismic Behavior of Self-Centering Precast Segmental Bridge Bents

Presented herein is an updated model for empirical prediction of 5 %-damped elastic response spectra in the period range 0–10 s, peak ground acceleration and velocity, based on a global dataset of digital acceleration records. The predictive model features saturation of the shaking parameters with both magnitude $$M_{W}$$
 and distance $$R_{ RUP }$$
 , magnitude-dependent distance attenuation, alternative parameterisations of the amplification effects due to local site conditions (based either on ground types or $$V_{S,30}$$
 ) and corrective terms for style-of-faulting. The calibration dataset comprises more than $$1{,}880\times 2$$
 orthogonal horizontal accelerometer records with $$R_{ RUP }< 150$$
  km from 98 global earthquakes with $$4.5\le M_{W}\le 7.9$$
 . The processing technique applied to the acceleration data optimises the reliability of the predictions at long periods, as required by displacement-based design techniques. Developed independently of the recent NGA-West2 and RESORCE-based models, the new predictive tool effectively contributes to capturing the epistemic uncertainties associated with the prediction of seismic shaking levels for engineering applications.

/pdf/updated-predictive-equations-for-broadband-0-01-10-s-3ooc20b6mf.pdf

Updated predictive equations for broadband (0.01–10 s) horizontal response spectra and peak ground motions, based on a global dataset of digital acceleration records

Precast segmental construction technique is an excellent candidate for economic rapid bridge construction in highly congested urban environments and environmentally sensitive regions. This paper presents the seismic behavior of four hybrid segmental columns consisting of precast posttensioned concrete-filled fiber tubes (PPT-CFFTs). A fifth monolithic column was also tested as a reference specimen. The columns were tested under increasing lateral loading cycles in a displacement control. The columns had circular cross section diameters of 203 mm and heights of 1,524 mm each. The parameters investigated included different construction details and energy dissipation systems. The PPT-CFFT columns developed lateral strength and deformation capacity comparable to those of the monolithic reinforced concrete column. However, the PPT-CFFT columns dissipated smaller hysteretic energy compared to that of the monolithic reinforced concrete column. Finally, a simple model was used to predict the backbone curves of se...

Seismic Behavior of Posttensioned Concrete-Filled Fiber Tubes

Correctly accounting for the uncertainty in ground‐motion prediction is a critical component of probabilistic seismic‐hazard analysis (PSHA). This prediction is commonly achieved using empirical ground‐motion prediction equations. The differences between the observed and predicted ground‐motion parameters are generally assumed to follow a normal distribution with a mean of zero and a standard deviation sigma. Recent work has focused on the development of partially nonergodic PSHA, where the repeatable effects of site response on ground‐motion parameters are removed from their total standard deviation. The resulting value is known as single‐station standard deviation or single‐station sigma. If event‐to‐event variability is also removed from the single‐station standard deviation, the resulting value is referred to as the event‐corrected single‐station standard deviation (![Graphic][1] ). In this work, a large database of ground motions from multiple regions is used to obtain global estimates of these parameters. Results show that the event‐corrected single‐station standard deviation is remarkably stable across tectonic regions. Various models for this parameter are proposed accounting for potential magnitude and distance dependencies. The article also discusses requirements for using single‐station standard deviation in a PSHA. These include the need for an independent estimate of the site term (e.g., the repeatable component of the ground‐motion residual at a given station) and properly accounting for the epistemic uncertainty in both the site term and the site‐specific single‐station standard deviation. Values for the epistemic uncertainty on ![Graphic][2] are proposed based on the station‐to‐station variability of this parameter.

 [1]: /embed/inline-graphic-1.gif
 [2]: /embed/inline-graphic-2.gif

A Model for Single‐Station Standard Deviation Using Data from Various Tectonic Regions

A segmental precast posttensioned (SPPT) bridge pier is an economic recentering structural system. Understanding the seismic behavior of a SPPT system is an important step toward its application in high seismic zones. This paper presents a detailed three-dimensional finite-element (FE) model that was developed using the ABAQUS platform. A brief description and discussion of cyclic tests on eight large-scale SPPT piers is also presented. Four of the piers were constructed and tested to a predefined degree of damage. Then, these piers were retrofitted and retested. The FE models developed and presented in this paper predicted the backbone curves of the piers that were tested directly after construction with an average error of 7% for drift angles smaller than 2.5%. For drift angles greater than 2.5%, the average error reached 13%. For piers that were retrofitted and retested, the error in predicting the backbone curve depended on the state of damage before the retest. When preexistent microcracks we...

Behavior of Segmental Precast Posttensioned Bridge Piers under Lateral Loads

Analysis of segmental piers consisted of concrete filled FRP tubes

The Kiban-Kyoshin network (KiK-net) database is an important resource for ground motion (GM) studies. The processing of the KiK-net records is a necessary first step to enable their use in engineer...

Haitham M. Dawood

Papers

Seismic Behavior of Posttensioned Concrete-Filled Fiber Tubes

A Model for Single‐Station Standard Deviation Using Data from Various Tectonic Regions

Behavior of Segmental Precast Posttensioned Bridge Piers under Lateral Loads

Analysis of segmental piers consisted of concrete filled FRP tubes

A Flatfile for the KiK-net Database Processed Using an Automated Protocol