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Linear and nonlinear response history analyses (RHA) are often conducted for predicting the seismic demand and capacity of structures. The proper selection of ground motions is critical to ...

In the last decade the quality and the amount of observational asteroseismic data that has been made available by space based missions had a tremendous upgrowth. The determination of asteroseismic parameters to estimate the fundamental physical processes occurring in stars' interiors, can be done today in a way that has never been possible before. In this work we propose to compute the seismic observable $\beta$, which is a proxy of the phase shift of the acoustic modes propagating in the envelope of the Sun-like stars. This seismic parameter $\beta$ can be used to identify rapid variation regions usually known as glitches. We show that a small variation in the structure, smaller than 1% in the sound speed, produces a glitch in the acoustic potential that could explain the oscillatory character of $\beta$. This method allows us to determine the location and the thickness of the glitch with precision. We applied this idea to the Sun-like star $\alpha$ Centauri A and found a glitch located at approximately $0.94\,R$ (1400 s) and with a thickness of 0.2% of the stars' radius. This is fully consistent with the data and also validates other seismic tests., Comment: 11 pages, 7 figures, 2 tables

The effectiveness of a novel Post-Tensioned Metal Strapping (PTMS) technique at enhancing the seismic behavior of a substandard RC building was investigated through full-scale, shake-table tests during the EU-funded project BANDIT. The building had inadequate reinforcement detailing in columns and joints to replicate old construction practices. After the bare building was initially damaged significantly, it was repaired and strengthened with PTMS to perform additional seismic tests. The PTMS technique improved considerably the seismic performance of the tested building. While the bare building experienced critical damage at an earthquake of PGA = 0.15 g, the PTMS-strengthened building sustained a PGA = 0.35 g earthquake without compromising stability.\ud \ud

A series of seismic tests of mechanical snubbers on a full-scale model piping system provided a unique opportunity for detailed scrutiny of snubber seismic behavior on an actual piping system. The observed snubber behavior is a complicated pattern of braking and releasing, drag and drift, and the dynamic characteristics of the snubber, as well as the input motion, play a role in the response of the snubber. The snubbers were effective in limiting pipe displacements. Relative accelerations across the snubber were larger than expected. Snubber hysteretic behavior was irregular. Results from this testing are important in understanding snubber behavior, evaluating snubber performance, and in assessing alternatives to snubbers.

Numerical modeling and Response Displacement Method are applied to assess the effects of the presence of cross passages and geological formations on the seismic responses of the Qianjiang River tunnel, in order to determine the proper locations of cross passages. The numerical analysis shows that the presence of cross passages affects the longitudinal seismic response of the main tunnel significantly within a 25-m distance from the intersections of cross passages with main tunnels. So, the possible local failure of the intersections will be a major concern. This is largely attributed to the complicated geologic formations and irregular ground conditions. The analysis based on the Response Displacement Method indicates that cross passages in flat and uniform ground layers can mitigate the local failure at the intersections. Optimal location for cross passages are proposed based on the detailed analysis of the geologic profiles of Qianjiang River Tunnel.

In the last 4 years, a high-resolution 3D motion capture system named 3DVision was installed at ENEA Casaccia as integration to more conventional instrumentation for measuring motion parameters during seismic tests, such as accelerometers, LVDTs, wire transducers and laser displacement sensors. In the present paper, some examples are illustrated to show the ENEA experiences with this relatively new technique in comparison to the other consolidated measurement systems. 3DVision is described in terms of flexibility and accuracy and specific potentialities are stressed. The main peculiarities of the 3DVision system derive from its capability of monitoring in real-time the absolute 3D position of more than a hundred measurement points without locating any active sensor or cable on the studied structure and on the shaking table, but only by means of cheap passive markers. Consequently, any risk of instrumentation damage in case of destructive tests is intrinsically avoided and the acquisition of hundreds of channels is guaranteed. Within the DySCo virtual lab, the 3DVision friendly graphical interface for real-time monitoring and its synchronous overlay function between markers wireframe and tests movies revealed particularly effective for remote sharing of the experimental campaigns with research partners via the internet. Also a remarkable contribution is given by the possibility of integrating and comparing experimental data with FE results at the same positions, calibrating FEM boundary conditions (materials properties, model constraints, loads etc.) in order to improve the simulation significance and reliability for similar cases. Through the DySCO web portal such numerical simulations and computations can be carried out exploiting the software and hardware resources available in the ENEA-GRID. © 2013 WIT Press.

Krauklis waves are a special wave mode bound to and propagating along fluid-filled fractures. They are of great interest because when propagating back and forth a fracture, they may fall into resonance and emit seismic signals with a characteristic frequency. This resonant behavior can lead to strongly frequencydependent propagation effects for seismic waves and may explain seismic tremor generation in volcanos or affect micro-seismic signals in fractured fluid reservoirs. All existing studies assume a Krauklis wave initiation inside a fracture, for example by hydro-fracturing. Here, Krauklis wave initiation by an incident plane P-wave is studied. The P-wave is scattered at the fracture, but also, two Krauklis waves are initiated, one at each fracture tip (i.e., diffraction-points of the fracture). The initiation of Krauklis waves strongly depends on the fracture orientation with respect to the incident P-wave. High-amplitude Krauklis waves are initiated at moderate (12°–40°) and high (>65°) incident angles with a distinct gap at around 50°. The initiated Krauklis waves are only visible within, but not outside the fracture. Nevertheless, the fact that P-waves can initiate Krauklis waves has important implications for earthquake signals propagating through fluid-bearing fractured rocks (volcanic areas, fluid-reservoirs) or for active seismic surveys in fractured reservoir situations.

Tight sandstone gas with abundant reserve and wide distribution will be the key field in seismic prospecting. We introduce the digital characterization for the micro pore structures in tight sandstone based on high-resolution CT scanning technology, and then build a pore geometry model with several types of pore shapes and two types of pore connectivity. When elastic wave propagates in this kind of porous medium, fluid in pores with different shapes and connectivity will respond differently, which affect the elastic properties of tight sandstones. Therefore, we apply Biot-Gassmann equation and Mori-Tanaka model to analyze the connected and isolated pores respectively, and then formulate a new rock physics model. By comparison with experimental data, this model can give more reasonable explanation.

The effect of fault crossing on the response of the seismically isolated Bolu Viaduct is investigated. The seismic ground motions at the site of the Viaduct are generated following a rigorous methodology, which is based on seismological data available in the literature and finite-fault modelling techniques of the extended source. The generated motions are used to study the effect of fault crossing and fault crossing angle on the nonlinear behaviour of the seismically isolated Viaduct. It is shown that fault crossing is an important factor in the earthquake response of seismically isolated bridges, and that this effect needs to be considered in the design and detailing of the isolation system.

Seismic issues are international interests. Non-linear Time History Analysis simulates the structure behavior under severe Earthquake movement more properly than other methods. In this paper, Non-linear time history analysis will be presented with one of the world famous project. Yerba Buena Island (YBI) West-Bound (WB) Ramps are portion of San Francisco-Oakland Bay Bridge Project. The Ramps are touched down to Yerba Buena Island (YBI) from YBI WB Widening by hinges. This project is located at a 0.627g Site Specific Response for Safety Evaluation Earthquake (SEE). YBI WB On-ramp is a highly horizontally Curved Bridge with radius of 127.3 feet (38.8 meters). Seismic behavior is very important for the project. In order to understand structural non-linear behavior, especially highly horizontally curved bridge behavior under severe earthquake events, YBI WB On-ramp stand-alone bridge is analyzed by non-linear time history analysis method. SAP 2000 with Hilber-Hughes-Taylor α direct integration method is used for Non-linear Time History Analysis (NL-THA). Seismic Modeling is discussed in this paper. Then six sets of acceleration time histories are used for NL-THA by SAP 2000. Open System for Earthquake Engineering Simulation (Open-SEEs) program developed by University of California-Berkeley is used to verify the SAP NL-THA accuracy in this paper. Site Specific Response Spectra ARS is also used for liner analysis and compared with results of Non-linear Time History Analysis and Open-SEEs Analysis. Non-linear push-over analysis is performed to determine the structural capacity and ductility under severe earthquake events. Finally, discrepancies between different program analyses are discussed and recommendations are presented.

The seismically vulnerable East Span of the San Francisco-Oakland Bay Bridge will be replaced with a dual east bound and west bound 3.6 km long parallel structure. The iconic single tower asymmetric self-anchored suspension bridge was selected by an international panel of experts from a total of four design alternatives that were developed for the signature main span. Analytically, geometrically, and in the design of practical details for fabrication and durability, the Self Anchored Suspension Bridge is a unique structure requiring innovative solutions and departures from conventional design. Whether a similar bridge of this scale will ever again be proposed is unknown. However, the set of methods and technologies developed to meet these challenges offer an illustrative study of designing a world class structure, an architectural icon, and a seismic innovation all at one time in one of the most seismically challenged areas in the world. The bridge will be open to traffic by the summer of 2013.

Two-stage analysis has been performed by structural engineers since its introduction to the code in the 1988 Uniform Building Code. This analysis procedure simplifies the analysis and design of a flexible structure supported by a rigid structure while allowing proper base shear scaling and use of R-factors of the two structures. However, despite its original intent, two-stage analysis can prove to be difficult to implement in complicated structures. Through our experience with the design of two new hospitals and evaluation of one existing hospital, we highlight to practicing seismic engineers and code developers some challenges and recommendations regarding (a) code interpretation and intent of the two-stage analysis provisions, (b) application, idealization and modeling of boundary conditions and soil springs, and (c) use and limitations of analysis models and software.

This paper describes the results of an extensive study on the seismic behavior of a viscoelastically damped structure under mild and strong earthquake ground motions. Shaking-table studies were conducted on a 2/5-scale five-story steel model with added viscoelastic (VE) dampers under various ambient temperatures, damper-placement cases, and earthquake intensities. Three types of VE dampers distinguished by dimensions and viscoelastic materials designed to provide the structure with similar damping ratios at room temperature were used. Analytical studies were carried out to predict the equivalent damping ratios and seismic response of the viscoelastically damped structure. Experimental results show that the VE dampers are effective in attenuating seismic structural response under mild and strong earthquake ground motions. Numerical results show that the structural damping and structural response with added VE dampers can be easily and accurately calculated by the proposed analytical methods. The methods are readily available to practical applications.

The use of lightweight fill, such as EPS-block geofoam, is a slope stabilization procedure that can be used to reduce the weight of the sliding mass and, thereby, reduce the driving forces of the sliding mass. This paper proposes the use of the horizontal slice method (HSM) for seismic stability analysis of slopes stabilized or repaired with EPS-block geofoam.

Bu çalışmada, yapı altında yüksek dayanımlı geotekstil malzemenin ultra yüksek moleküler ağırlıklı polietilen esaslı geomembran (UHMWPE) üzerine yerleştirilmesi ile oluşturulan bir sismik izolasyon sisteminin (kompozit sistem) dinamik davranışı incelenmiştir. Tez içerisinde, bahsi geçen sismik izolasyon sisteminin kullanıldığı ve kullanılmadığı durumlar için model binalar üzerinde harmonik ve uyarlanmış deprem hareketleri altında yapılan sarsma tablası deney sonuçları sunulmuştur. Bu sistemin kullanılması durumunda, kullanılmadığı duruma göre elde edilecek iyileştirme çalışmanın odak noktasını teşkil etmektedir. Deney sonuçlarına göre, test edilen sismik izolasyon sisteminin kullanılması durumunda harmonik taban hareketi altında yapıya gelen ivmelerin büyük oranda düştüğü ve göreli kat öteleme oranlarının ciddi miktarda azaldığı tespit edilmiştir. Diğer taraftan deprem hareketleri altında spektral ivmelerin önemli ölçüde düştüğü gözlemlenmiştir. Bu durum yapıların dinamik etkiler altındaki güvenilirliğini, yapının yatayda deplasman yapması karşılığında, önemli oranda artırmaktadır. In this research, the dynamic behavior of a seismic isolation system composed of high strength geotextile placed over an ultra-high molecular weight polyethylene (UHMWPE) geomembrane (together called as composite liner) beneath the structure is investigated experimentally. The results of the shaking table experiments which were performed on model structures both under harmonic and modified earthquake motions with and without the seismic isolation (composite liner system), are presented in the thesis. The main focus is given on the potential improvement obtained by use of the composite liner system as compared to the unisolated cases. Based on the performed experiments, it is observed that the utilization of composite liner system provides significant reduction in the accelerations and interstorey drift ratios of structures under harmonic motions while signifant drop is obtained in the spectral accelerations under earthquake motions which provide noticeable improvement in the durability of structures under dynamic effects at the expense of increased translational displacements. 198

In structural behavior, the analysis of civil buildings by seismic tests has been generalized by the use of shaking tables. This method requires advanced control systems. In our research we show the implementation of a Model Reference Adaptive Control (MRAC) to control the position of a shaking table, modified by the introduction of a Smith predictor to compensate the error produced by the system delay. The mechanic is based on a Slider-crank device. The control system is implemented on a 32 bits platform by Microchip, and the control is done via a remote server using the RENATA network. The results of our adaptive control system were experimentally verified using the shaking table with a 24 kg mass as a load.

The seismic excitation experienced by structures is a function of the earthquake source, travel path effects, local site effects, and soilstructure interaction (SSI) influences. The result of the first three of these factors is referred to as free-field ground motion. The structural response to free-field motion is influenced by the SSI. In particular, accelerations within structures are affected by the flexibility of the foundation support and variations between the foundation and free-field motions. Consequently, an accurate assessment of inertial forces and displacements in structures can require a rational treatment of SSI effects. In the current study, to depict these effects on the seismic response of moment-resisting building frames, a 10-story moment-resisting building frame resting on a shallow foundation was selected in conjunction with three soil types with shear-wave velocities of less than 600 m/s, representing Soil Classes Ce, De, and Ee according to an existing Australian Standard. The structural sections were designed after applying dynamic nonlinear time-history analysis, based on both the elastic method, and inelastic procedure using the elastic-perfectly plastic behavior of the structural elements. The frame sections were modeled and analyzed using the finite-difference method andthe FLAC 2D software under two different boundary conditions: (1) fixed-base (no SSI) and (2) considering the SSI. Fully nonlinear dynamic analysis under the influence of various earthquake records was conducted and the results of the two different cases for elastic and inelastic behavior of the structuralmodel were extracted, compared, and discussed. The results indicate that the performance level of themodel resting on Soil Class Ce does not change substantially and remains in the life safe level while the performance level of themodel resting on Soil Classes De and Ee substantially increase from the life safe level to near collapse for both elastic and inelastic cases. Thus, considering SSI effects in the elastic and inelastic seismic design of concrete moment-resisting building frames resting on Soil Classes De and Ee is essential. Generally, by decreasing the dynamic properties of the subsoil such as the shear-wave velocity and shear modulus, the base shear ratios decrease while interstory drifts of the moment-resisting building frames increase relatively. In brief, the conventional elastic and inelastic design procedure excluding the SSI is not adequate to guarantee structural safety for moment-resisting building frames resting on Soil Classes De and Ee. © 2013 American Society of Civil Engineers.

A procedure is developed for including the effects of accidental torsion in seismic design of buildings. It has four steps. First, the ratio between the fundamental frequencies of uncoupled torsional and lateral motions of the building is computed. This ratio and plan dimensions are then used to estimate the increase in displacements at the edge of the building resulting from all sources of accidental torsion. Third, from these edge displacements the increase in displacements at the location of interior resisting planes are estimated. Finally, the design forces in structural members are computed by amplifying the forces ignoring accidental torsion by the increase in building displacements determined previously. This procedure has several advantages over the code-specified static and dynamic analysis procedures to include accidental torsion, such as: (1) The elimination of cumbersome static or three-dimensional dynamic analyses to account for accidental torsion effects in building design; and (2) the inclusion of the effects of all sources of accidental torsion. Two building examples are presented to illustrate these advantages as well as the computational steps required to implement the new procedure.

This paper addresses the concern that the current provisions in the code, on buckling and lateral bracing of steel moment frames, allows significant uncontrolled member distortions to occur, due to seismic events, which could lead to poor performance. The paper includes historical considerations on buckling and lateral bracing pertinent to the understanding of buckling and lateral bracing issues, relating to steel moment frames. Considerations and recommendations are given relating to the control of buckling. The paper also provides recommended alternative simplified procedures to evaluate lateral bracing of moment frame girders based upon the principles of mechanics.

The performance of glazing systems in past (mostly US) earthquakes is reviewed. The mechanism of glass failure in curtain walls and possible sources of seismic failure of glass is explained. In general, past earthquakes have revealed that glass held in punched window frames, storefronts, and curtain walls are vulnerable. Some approaches to reduce glass damage in earthquakes are also discussed. Such methods include the use of large glass-to-frame clearance, the use of safety film, and the use of structural silicone glazing. Recent research on innovative ways to mitigate seismic damage to architectural glass is also reviewed. Finally, current trends in curtain wall construction for improved seismic performance of architectural glass are discussed.

This study investigates the applicability of force-displacement equations suggested in currently used design codes, based on “Guidelines for the seismic design of oil and gas pipeline systems” of ASCE (1984)[1] as their main reference, to introduce the soil-pipe interaction for segmented type of pipeline systems. Hence, results of finite element method (FEM) analyses are verified by full-scale experiments on a segmented ductile iron pipeline with 93mm diameter and 15m length. Pipeline is installed at a 60cm depth from the ground surface in two types of sandy soil with different values of sub-grade reaction. Adopted fault is a reverse type which has an intersection angle of 60 degrees with pipeline and moves in three same steps to reach its total movement of 35cm. Findings reveal that the aforesaid interaction equations are basically developed for continuous pipelines and the effect of connection joints on the integrated structural behavior of segmented pipelines is not considered in them. Hence, suggesting them by currently used guidelines for seismic design of fault crossing segmented pipelines leads to overestimation of soil resistance against relative downward movement of pipeline in surrounding soil continuum.

Drilled shaft foundations have been used for several decades for highway and building applications; however they have only seen limited use in foundations for modern utility scale wind turbines. The limited use of drilled shaft foundations for wind turbines is likely due to the perceived difficulty in fatigue analysis, load and resistance factor design, and meeting the dynamic stiffness requirements of the foundation system. The discussion provided in this paper demonstrates how all of these elements can be brought together in a practical manner to create an economical, robust foundation design taking into account all of the potential geotechnical hazards affecting the site. This paper presents a case history of a wind energy project located in Palm Springs, California in an area subject to high seismic loading from the nearby San Andreas Fault Zone, severe scour due to the project location in a flood plain, and constrained by endangered species habitat areas. This paper follows the project through design, including analysis of seismic loading, dynamic stiffness, soilstructure interaction, concrete and steel fatigue and drilled shaft capacity. Construction aspects of the project are also included in the paper.

The initial anisotropy of natural clays can be characterized by the elastic shear moduli measured by wave propagation techniques both in situ and in the laboratory. This paper summarizes results of studies of the initial anisotropy of fresh water glacial clays from two sites in the Chicago area. Advanced cross-hole seismic tests which measure both horizontally propagating and vertically- and horizontallypolarized shear wave velocities and seismic cone penetration tests (sCPT) were performed in situ. Bender elements were used to measure propagation velocities on laboratory specimens cut from high quality block samples of soft to medium clays obtained from the excavation for the Ford Design Center project. These clays are lightly overconsolidated, supraglacial tills. Laboratory specimens of hard clay from the One Museum Park West site were obtained with a Pitcher barrel sampler; these clays are overconsolidated, basal tills. Both in situ and laboratory results for the soft to medium clays indicate that the magnitude of the shear moduli are the same in each polarized direction. These clays are slightly cross anisotropic. For the harder clays, the in situ shear moduli are larger than those measured in the laboratory, presumably as a result of the sample disturbance arising from Pitcher barrel sampling.

Structures Congress 2012 contains 202 papers on topics that are redefining structural engineering in the areas of bridges, transportation structures, buildings, and advances in research. Topics include: blasts; bridges; buildings; business issues; nonbuilding structures; seismic issues; and sustainability. This collection, which includes papers from the CASE Spring Risk Management Convocation, will be useful to all structural engineers and allied professionals. bridge research and implementation; buildings; business; nonbuilding structures; seismic; special topics; and sustainability.

Two full-scale precast concrete cladding panels were tested in 2011 on a full-scale five-story steel fame building at the E~Defense shake table facility in Japan. The panels were designed according to common U.S. practice. Two issues evaluated were: 1) the effect of acceleration on the cladding panel, and 2) the effectiveness of the current slotted-bolt sliding connection to allow for inter-story earthquake motion. The cladding tests represented one type of standard US cladding facade design where cladding is designed to accommodate inter-story drift though racking of individual panels. Panels were cast in Japan but steel connections were designed and fabricated in the US to accurately simulate the behavior of American cladding construction. A 50 mm vertical seismic joint was installed between the two panels. Two full-height column cover panels were tested, a return cover 3D shape, and a flat panel. Instrumentation measured the acceleration of the panels and the movement of the slotted connections. Findings include the ability of slotted connections to slide while being accelerated in a full scale 3D seismic motion and development of fragility curves relating damage to panel and/or floor acceleration.

This paper investigates the behavior and performance of open-web truss-moment framing system under cyclic loading. An open-web truss-moment frame of a four-story building was designed as an ordinary moment resisting frame (OMRF) for this investigation. Three full-scale, half-span subassemblages from this building were tested under severe cyclic deformation to determine their hysteretic behavior. Based on the experimental results, a simple analytical model for inelastic cyclic behavior of open web truss frames was developed. This model was used to analytically evaluate the behavior and performance of the four-story building subjected to several severe earthquake excitations. The system performs poorly because of buckling and fracture of the web members, which led to unstable hysteretic loops.

A series of simulated seismic tests have been conducted using mild steel and stainless steel plain pipe specimens. These specimens were pressurised and subjected to fully reversed cyclic bending moments at frequencies of about 5 Hz. The bending moments and surface strains on the pipe wall were monitored and are reported here. Significant ratchetting was observed which, in the case of the mild steel specimens, lead to gross swelling and eventual failure. Although ratchetting was observed in the stainless steel specimens it was not so pronounced and failure appeared to be by low cycle fatigue.

A formulation for modeling links in eccentrically braced steel frames (EBFs) subjected to random inelastic cyclic loading is presented. The formulation is plasticitybased, and includes shear and fl...

The history of steel bell and spigot joints with fiber-center lead gasket for concrete pressure pipe in California dates back to 1933, and the modern joints with O-ring gaskets for concrete and steel pressure pipelines to 1940. The performance of these gasketed joints in the seismically active region of California has been excellent. There have been isolated occurrences of damage to both unrestrained gasketed joints and welded restrained joints. The damage generally occurred at the end of concrete encasements or at structures or near bends. Several case studies will evaluate the effect of three large recent earthquakes on nearby pipelines. This paper will show that the empirical evidence suggests that gasketed joints of concrete pressure pipe and intermediate diameter steel pipe perform well in earthquakes and they should be considered for pipeline projects in seismically active regions. Recommendations will be made regarding measures that may reduce the risk of damage to pipelines using gasketed joints.

Using numerical simulation method, dynamic response regularity of highway roadbed retaining wall under the action of earthquake is simulated. Calculation model is established with reference to the basic size of anti‐seismic retaining wall. The seismic dynamic response characteristics of two different types retaining walls using to strengthen highway roadbed which include upright retaining wall, inclined retaining wall and balance weight retaining wall is calculated. Their seismic efficiency is compared and some regular conclusions are reached.

Since the "5.12" WenChuan Earthquake occurred in China, evaluation of the ultimate aseismic capacity has been a crucial issue for seismic safety design of high core rock-fill dams. However, reasonable evaluation of the ultimate aseismic capacity of high rock-fill dams still confuses the hydraulic engineers. Thus an original approach to evaluate the ultimate aseismic capacity is proposed. In this approach, the ultimate peak acceleration of input motion which the dam could tolerate is taken as an important index to evaluate the ultimate aseismic capacity. The ultimate peak acceleration can be directly achieved on the basis of 'Specifications for seismic design of hydraulic structures' instead of trial and error method. Then, the proposed method is adopted to evaluate the ultimate aseismic capacity of the 240m ChangHe high rock-fill dam. In addition, comprehensive studies on the dynamic response and potential failure mode as the rock-fill dam subjected to the ultimate tolerable input motion, that is, the rock-fill dam is at verge of failure, are presented. Consequently, the corresponding reinforced design for the high rock-fill dams can be carried out effectively on the basis of the dynamic analysis as the dam reach the ultimate limit equilibrium state.

The Xi'an city metro system is located within an active geological area containing several ground fissure sites. This potential geological hazard can cause serious threats to construction of the new metro system. In this research study, prototype model tests were conducted to investigate the effects of the ground fissures on the metro system under earthquake forces. The prototype model box was loaded with several seismic forces of different characteristics and the changes in the ground fissures were surveyed. Test results showed that 1) The existing ground fissures opened wider under the applied seismic forces and new fissures appeared close to the existing cracks, 2) The seismic forces caused larger soil settlements within the vicinity of the ground fissures and the long duration earthquake forces resulted in larger soil settlements, 3) The laboratory prototype model tests resulted in very useful information in terms of the behavior of the ground fissures and their interactions with the metro system under the simulated seismic forces.

ASCE 7-10 Minimum Design Loads for Buildings and Other Structures contains several changes regarding wind loads. The major editorial change is a complete reorganization to a multiple-chapter format as done previously for seismic loads with the objective being to make the provisions easier to follow. Technical changes include the introduction of new wind speed maps to be used with a 1.0 load factor for LRFD and a 0.6 load factor for ASD, the reintroduction of Exposure D for water surfaces in hurricane-prone regions, and revised wind-borne debris regions. A new simplified procedure for buildings up to 160 ft has been added based on the provisions for buildings of all heights.

As engineers are being guided with greater frequency to ASCE 31, Seismic Evaluation of Existing Buildings , and ASCE 41, Seismic Rehabilitation of Existing Buildings , by state and federal government requirements as well as model building codes, greater numbers of buildings are being evaluated, upgraded, and even designed in accordance with the methodologies and criteria prescribed therein. By using these flawed standards, harm is being inflicted by the structural engineering profession on society-at-large. While the contributors to the original documents have been well aware of major technical problems with these documents since long before publication, efforts to mitigate the problems have been slow, and engineering studies of buildings across the country — including all buildings considered for lease by the Federal Government — are being impacted by these problems. To our knowledge, no formal efforts have yet been put forth to warn anyone — not engineers, not building owners, not government officials, and not building officials — that reliance on the documents can easily lead to wrong results — even though engineers most familiar with ASCE 31 and 41 acknowledge that in their own practice, use of the documents often entails modifying or ignoring major components of the published methodologies. In fact, despite the recent renewal of efforts by the associated ASCE committees to improve these standards as much as seven years after publication (and much more than a decade after the bases of these documents, FEMA 310 and 356, were published), these so-called standards remain highly flawed and continue to adversely affect the public interest. This paper discusses a selection of mind-boggling problems with ASCE 31 and 41, focusing on some aspects about which every engineer planning to use the documents ought to be aware.

ASCE 4, Seismic Analysis of Safety-Related Nuclear Structures and Commentary , was first issued in 1986. It was expanded, revised and re-issued in 1998. The second revision of the standard will soon be completed by the Working Group on Revision of ASCE 4, which is part of the ASCE Committee for Dynamic Analysis of Nuclear Structures. This standard provides prescriptive criteria for the analysis of safety-related (Seismic Category I ) structures, systems and components (SSCs). It is designed to be used in conjunction with ASCE-43/SEI 43-05, Seismic Design Criteria for Structures, Systems and Components in Nuclear Facilities. It addresses all aspects of seismic analysis: site response, modeling, and analysis for all types of SSCs. The standard also provides guidance on Quality Assurance requirements and Peer Review needs. Taken together, ASCE4 and ASCE/SEI43-05 may be adapted by federal agencies such as the U.S. Nuclear Regulatory Commission and the U.S. Department of Energy as the minimum expected seismic analysis and design requirements for nuclear facilities. This overview paper highlights the proposed changes to the ASCE 4-98 Standard proposed by the Working Group. These changes, if adapted, will become effective following consensus balloting and public comment of the proposed changes.

This paper discusses the effectiveness of simplified nonlinear static methods for predicting the seismic response of various steel moment resisting frames (MRFs) and shear wall structures. Different nonlinear static analysis procedures are discussed. Results from focused studies of different archetype structural systems are compared with nonlinear response history analysis (NRHA). The main engineering demand parameters considered are story drift ratios, story shear forces and overturning moments. Suggestions are made for improving accuracy and required effort of alternative nonlinear static procedures used to predict the seismic response of steel MRF and shear wall structural systems.

The axial and lateral monotonic and cyclic behavior of helical pile foundations was investigated and new helical screw systems suitable for seismic loadings were developed. More than one hundred full scale field load tests were conducted on instrumented helical screw piles installed in cohesive soil. The piles included: plain helical screw piles (P-HSP); grouted (G-HSPs); fiber reinforced polymer (FRP-G-HSPs); and reinforced grouted (RG-HSPs). The (RG-HSP) piles axial capacity was more than twice that for P-HSP, with minimal reduction after cyclic loading, and their lateral capacity was more than 3 times the P-HSPs capacity. A 3-D finite element model was established.

A new method of connecting members, at certain joints of a lateral force resisting structure, improves the response to seismic excitation. These connections that permit a small initial slip (displacement or rotation) are called sequential connectors. A sequential system is a structure consisting of units coupled in parallel in which at least one unit is attached by sequential connectors, and at least one other unit is attached by standard connections. A standard structure is transformed into a sequential system by replacing one or more (but not all) standard connections by sequential connectors. The effectiveness of sequential coupling, in some cases, is comparable to sensor-initiated active controls. Sequential systems exhibit an interesting and even surprising response to dynamic excitation. The paper outlines the characteristics of sequential systems and provides a numerical comparison of their performance with an identical structure using standard connections; the structure using standard connections shows a displacement response that is 40% higher. If the response of the two systems is identical, the standard system requires 40% more material.

The continuing expansion of HOV lanes and limited right-of-way on urban freeways have led to increased use of back-to-back MSE walls. Because these lanes are often constructed in the existing median, many of the back-to-back structures have small aspect ratios, with the distance between the two walls often less than 0.7 times the wall height. There are no FHWA design guidelines for back-to-back walls closer than 1.2 times the wall height. In this paper, results from dynamic constitutive models are compared to those from the traditional Mononabe-Okabe pseudo-static approach. Compared to the results of conventional design methodology, data from the dynamic analyses show that walls with smaller aspect ratios exhibit greater deformation than walls having a higher aspect ratio, although this trend is obscured at lower accelerations. The study also shows that the current state-of-the-practice pseudo-static method is conservative.

In this study, eight earthquake centrifuge tests were performed on a model of a cantilever retaining wall to study the seismic response of a retaining wall with anisotropic backfills. A special rigid container was designed and used to prepare models with different directions of soil deposition. The eight centrifuge models had 0, ±45 and 90 degrees of sand deposition angles and with dry or saturated backfills. It was shown that the fabric anisotropy had a strong effect on the settlement of backfill and the response of the retaining wall. It was also clear that the acceleration in the soil was sensitive to the fabric anisotropy of granular materials.

Most existing methods of estimating the settlement of footings in cohesionless soils under working stresses are empirical and based on correlations with field measurements of settlement. The result is considerable scatter and a lack of a basis for long term improvements. In this paper we propose a method of analysis based on equivalent-linear elasticity that involves measurement of real soil properties and uses simple analytical methods. We also propose methods to determine and/or estimate the needed soil properties. We report here on load tests of two footings and one plate with diameters ranging from 0.25 m to 0.91 m, in silty sand, in which measured settlement is compared with settlement predicted using the theory and soil properties determined in the field from seismic tests. We also compare measured settlements with values calculated with Schmertmann’s widely used method based on penetration testing.

Seismic restraint of nonstructural components (i.e., building contents and all building elements not part of the building structure) has gained in importance over the past decade. The primary objectives associated with seismic design of nonstructural components can be stated as: 1. Mitigation of falling hazards, particularly in or around paths of egress; 2. Mitigation of the release of hazardous materials; 3. Ongoing operability of structures and buildings vital to post-earthquake recovery (e.g. hospitals and fire stations); and 4. Mitigation of property and commercial losses. The requirements of ASCE/SEI 7–10 Chapter 13 are specifically intended to address the first three concerns, i.e., reduction (not elimination) of risks to building occupants associated with dislodgement and disruption of fixed building contents and systems, prevention of haz/tox release, and improvement of the likelihood that essential facilities will continue to function after an earthquake. While not a stated goal, some degree of property protection may result from successful implementation of the provisions; however, significant reduction of property losses, e.g., associated with pipe rupture and consequential flooding may require implementation of a greater degree of protection (such as leak tightness in piping systems). In this context the provisions of ASCE/SEI 7–10 are reviewed, specifically with regards to highlighted changes from the 2005 edition in the areas of anchorage, the treatment of architectural, electrical and mechanical components, system certification, and exempted components.

The ASCE/SEI Seismic Design Provisions embody the seismic design requirements enforced by U.S. Building Codes. Since 1998, the basis for these seismic design requirements contained in ASCE 7 has been the NEHRP Recommended Provisions for Seismic Regulation of Buildings and Other Structures, developed and published by the Building Seismic Safety Council of the National Institute of Building Sciences under contract to the Federal Emergency Management Agency. BSSC has published the NEHRP Provision since 1985. The BSSC Provision provide a forum for new seismic design criteria including to be developed under an informal consensus process, and readied for adoption in ASCE 7 and other standards. Traditionally the NEHRP Provisions have provided a vehicle for the development of new analytical procedures, new structural systems and even entire design procedures. The 2009 NEHRP Provisions were instrumental in the development of new seismic hazard maps included in ASCE/SEI 7–10 as well as design provisions for AAC wall systems and cold–formed steel moment resisting frame systems, as well as extensive requirements for nonbuilding structures. Importantly, the NEHPR Provisions are accompanied by a complete commentary to the ASCE/SEI-7 seismic requirements as well as recommended new technologies that are not yet ready for adoption into the standard, but which may be suitable for such adoption in future years.

New provisions for computing peak ground acceleration (PGA) for soil liquefaction and stability evaluations have been introduced in Section 11.8.3 of the 2010 NEHRP Seismic Provisions and the ASCE 7–10 standard. The PGA provisions consist of maps of the Maximum Considered Earthquake (MCE), geometric mean, horizontal component, bedrock PGA, plus a site-coefficient (F PGA ) table to convert the bedrock PGA value to one corresponding to another site class. Of particular note is the requirement that liquefaction must now be evaluated for the MCE, rather than the design earthquake, as currently required in the 2006 International Building Code (IBC) and ASCE 7-05.

This paper contains the findings of an experimental study on the seismic response of two types of standard frictional bridge bearings: (a) steel-reinforced elastomeric bearings with PTFE disks, and (b) PTFE spherical bearings. The experimental program which was conducted partly at UC San Diego and partly at UC Berkeley included cyclic tests at various velocities and displacements for which these bearings have not been designed but may experience during an earthquake. The primary conclusions of these tests are that PTFE-elastomeric bearings perform adequately but cannot accommodate rotations reliably. Spherical bearings featuring general-purpose adhesives perform very poorly under seismic conditions; however, when high-temperatures adhesives are used in their construction, these bearings perform very well under seismic conditions.

There are considerable changes in the sections on suspended ceilings between ASCE 7-05 and ASCE 7-10. These changes fall into two categories: changes in the requirements and changes in the cited references. Additionally, many requirements have been relocated from ASCE 7 to the cited reference, reducing conflicts between the two documents and greatly simplifying the understanding of the requirements. Since the commentary for these code sections is currently limited, this paper will also review the history and rationale behind the current requirements. This is to aid in applying the requirements to field conditions as well as designing custom applications to constructions not covered by ASCE 7.

Finite Element Method has been used to investigate the interaction of soil-retaining wall under the effect of earthquake induced forces. By numerical analysis the behavior of modeled gravity retaining walls have been evaluated under the effect of four real earthquake spectra. Different soil mechanical properties, cohesion and internal friction angle, has been considered. Height of wall was also varied in numerical analysis. Results obtained from numerical analysis then were compared with those calculated by using Mononobe-Okabe method.

In shaking table studies considerable attention is paid to the design of the foundation and the anchorage of the specimen. All analyses consider completely rigid shaking table (actuators and platform). However, since long interaction between the shaking table and massive specimens has been clearly observed, namely a decrease in frequency of the specimen “on the shaking table” with respect to that “on a rigid base”. This paper investigates the validity domain of the rigid “Azalee” shaking table at the CEA (Saclay) laboratory. It demonstrates that, for this large shaking table, most of the interaction is due to the platform deformation during the test. Two charts giving the reduction in frequency as a function of specimen parameters are obtained using a simplified specimen model for lateral and vertical modes, without local deformation between the specimen and the platform. They are validated in three large experimental tests performed in the past 10 years, within the CAMUS, ECOLEADER and SMART projects. Using them it is easy to estimate the minimum decrease in frequency of a specimen fixed on the platform. If this first estimation shows significant interaction, a more detailed study is needed. A simplified FE model of the platform is available for a definite evaluation of the interaction. A second evaluation takes into account the local deformations between the specimen and the platform. For large specimens these local deformations can reduce the frequency by almost 50%. Evaluations of the interaction were made after past Azalee shaking table tests, using simplified models. This paper will help experimental and numerical researchers to better take care, during the design of the test, of the boundary conditions between the platform of the shaking table and the specimen. More detailed comparisons to numerical analyses of large shaking table tests will now be possible for the Azalee table.

Headed reinforcing bars increasingly are being used in reinforced concrete structures. This paper reports on a study to evaluate the applicability of these headed bars in exterior beam-column joints. A total of 12 pullout tests were first performed to examine anchorage behavior of headed bars subjected to monotonic and repeated loading. Variables such as the head size, shape, and head attaching technique were examined. Reversed cyclic tests of two full-scale exterior beam-column joints were conducted to assess seismic performance. The pullout test results revealed that all types of heads and head-attaching techniques performed almost equally well, while the seismic test results indicated that the joint using small-headed bars showed better seismic performance than the joint using hooked bars in terms of damage extent, joint behavior, lateral drift capacity, and energy dissipation. In particular, the joint with headed bars generally satisfied ACI 374 acceptance criteria. The findings also indicate that small-headed bars can be effectively anchored in exterior beam-column joints under inelastic deformation reversals and that they perform well with a development length shorter than that needed for hooked bars.