Proposal on Non-Linear Response Analysis Method in Frequency

The objective of this report is to propose a non-linear response analysis method in frequency domain based on the stress and strain relationship of soil in frequency domain. First of all, a new model for the strain and frequency dependent characteristics between shear modulus and damping constant with respect to the complex shear modulus is proposed, considering the following two characteristics; One is the similarity of stress-strain relationship between time domain and frequency domain. The other one is a non-stationary characteristics in frequency domain caused by non-linearity of soil. A new non-linear dynamic response analysis method in frequency domain is proposed by incorporating the new model of the stress-strain relationship in frequency domain into the commonly used nonlinear response analysis method in frequency domain. The accuracy of this method is evaluated by the comparison of the analytical results obtained by two kind of non-linear dynamic response analysis codes. Hence, “YUSAYUSA2” and “SHAKE” is used as the co de in time domain, in frequency domain respectively. It is found that this proposed method is useful to take into account of nonstationary behavior caused by non-linearity of soil

Experimental Studies on the Elastic-Plastic Behavior of Braced Frames under Repeated Horizontal Loading. Part 1 Experiments of Braces with an H-shaped Cross Section in a Frame

An experimental study is conducted to obtain the hysteretic characteristics of the brace itself in a braced frame under repeated loading. Braces with an H-shaped cross section are tested in a single or a double bracing system. The effects of the slenderness ratio, the buckling plane and the local buckling are investigated. Furthermore, the fundamental properties of a brace for the formulation of the hysteretic characteristics under repeated loading are extracted

Dynamic Compliance of Pile Group Considering Nonlinear Behavior Around Piles

Static and dynamic loading test of a foundation are carried out to obtain the behavior of a pile and a pile group. A conventional analysis based on the elastic wave theory are modified to obtain the complex rigidity of a pile group and are compared with the test results. It is shown that the analysis based on the conventional elastic wave theory are not enough to predict the dynamic behavior of piles since they do not take into account both the effect of slip and/or separation between the pile surface and the surrounding ground and the nonlinear behavior of the ground near the pile. An element to be put between the pile and surrounding ground is proposed so as to improve the analysis. The characteristics of the new element is represented as a compliance function which can be obtained from a static loading test of single pile

Modeling and Interpretation of Downhole Temperature in a Horizontal Well with Multiple Fractures

Downhole temperature data obtained by either temperature logging or fiber-optic cables has been used to evaluate stimulation treatments and post-stimulation performance of horizontal wells with multiple fractures. Qualitative detection of transverse fractures, poor zonal isolation, and inflow locations is possible; however downhole temperature behavior in those wells is not fully understood from the theoretical modeling perspective. In this study, comprehensive numerical flow and thermal models for a horizontal well with multiple fractures are presented. The well experiences single phase water flow during injection and shut-in, and gas-water two-phase flow during production. These models are formulated for reservoir and wellbore domains using mass, momentum and energy conservation in transient conditions. These models are coupled to obtain profiles of wellbore and sandface temperature as one of the solutions. These models enable us to simulate field operations in multistage fracturing treatments; injection and shut-in occur alternately for each stage from toe to heel with sufficient zonal isolation. Following the stimulation treatments, these models are used to simulate temperature behavior during production in gas-water two phase flow. The developed model is applied for several synthetic cases. These case studies show capabilities of the developed model to simulate downhole temperature behavior during processes of injection, shut-in and production. A single fracture case shows injected fluid lowers temperature in the fracture below the geothermal temperature even after one month of shut-in. This affects the temperature interpretation during production. The initial temperature is different than the geothermal temperature, as assumed by previously published work. A synthetic case with five fractures show capabilities of detection of fracture locations from the shut-in temperature profile. The temperature profiles obtained during production show different characteristics of the wellbore temperature and sandface temperature due to fluid mixing in the wellbore. The developed model was also applied to field cases. One of the field cases shows possibility to evaluate relative fracture length based on the shut-in temperature behavior, and the results are consistent with other measurements qualitatively. The model was also applied for flow profiling of a field case. The estimated flow profile by this work is consistent with the interpretation by production logging tool and the temperature model by a single phase gas. These field cases show capabilities of the temperature interpretation to obtain further understanding of the downhole conditions in a horizontal well with multiple fractures

Temperature Prediction Model for Horizontal Well with Multiple Fractures in Shale Reservoir

Fracture diagnostics is a key technology for well performance prediction of a horizontal well in a shale reservoir. The combination of multiple fracture diagnostic techniques gives reliable results, and temperature data has potential to provide more reliability on the results. In this work, we show an application of a temperature prediction model for a horizontal well with multiple hydraulic fractures in order to investigate the possibility of evaluating reservoir and hydraulic fracture parameters using temperature data. The model consists of wellbore model and reservoir model. The wellbore model was formulated based on mass, momentum and energy balance. The reservoir flow model was solved by a numerical reservoir simulation, and the reservoir thermal model was formulated by transient energy balance equation considering viscous dissipation heating and temperature variation caused by fluid expansion besides heat conduction and convection. The reservoir flow and reservoir thermal model were coupled with the wellbore model to predict temperature distribution in a horizontal well considering boundary conditions at the contact of reservoir and wellbore. In the reservoir system, primary hydraulic fractures which are transverse to the horizontal well were modeled with thin grid cells explicitly, and the hydraulically-induced fracture network around the horizontal well was modeled as higher permeable zone to unstimulated matrix zone. The reservoir grids between two primary fractures were logarithmically spaced in order to capture transient flow behavior. We applied the model to synthetic examples: horizontal well with identical five fractures and with different five fractures. The results show two fundamental mechanisms: heat conduction between formation and wellbore fluid at non-perforated zone, and wellbore fluid mixing effect at each fracture. The synthetic example with identical fractures shows that fracture locations affect wellbore temperature distribution because of fluid mixing effect between reservoir inflow and wellbore fluid. And also, the synthetic example with different fractures shows that the fracture heterogeneity causes different magnitude of temperature change due to inflow variation per fracture. In addition, the model was applied to synthetic examples without network fracture region in order to find the effects by the network. It reveals that under constant rate condition, network fracture masks large temperature change due to small pressure change at the contact between fracture and formation, and that under constant BHP condition, network fracture augments temperature change with the increase of flow rate in wellbore and inflow rate from reservoir. Sensitivity studies were performed on temperature distribution to identify influential parameters out of the reservoir and hydraulic fracture parameters including reservoir porosity, reservoir permeability, fracture half-length, fracture height, fracture permeability, fracture porosity, fracture network parameters, and fracture interference between multiple clusters. In this work, in order to find contributions by a target fracture, temperature change sensitivity is evaluated. Single fracture case reveals that fracture permeability, network fracture parameters and fracture geometries are primary influential parameters on temperature change at the fracture location. And also, multiple fractures case shows that temperature change is augmented with the increase of fracture geometry and is decreased with the increase of fracture permeability. These results show the possibility of using temperature to determine these sensitive parameters, and also the quantified parameter sensitivities provide better understandings of the temperature behavior of horizontal well with multiple fractures

Euclid detectability of pair instability supernovae in binary population synthesis models consistent with merging binary black holes

We infer the expected detection number of pair instability supernovae (PISNe) during the operation of the Euclid space telescope, based on two binary population models that are consistent with binary black holes (BHs) observed by gravitational waves. The two models consider different PISN criteria depending on the $^{12}$C$(\alpha, \gamma)^{16}$O reaction rate. The fiducial and $3\sigma$ models adopt the standard and $3\sigma$-smaller $^{12}$C$(\alpha, \gamma)^{16}$O reaction rate, which predicts that stars with helium core masses $65-135 M_\odot$ and $90-180 M_\odot$ cause PISNe, respectively. Our fiducial model predicts that Euclid detects several Type I or hydrogen-poor PISNe. For the $3\sigma$ model, detection of $\sim 1$ Type I PISN by Euclid is expected if the stellar mass distribution extends to $M_{\max} \sim 600 M_\odot$, but the expected number becomes significantly smaller if $M_{\max} \sim 300 M_\odot$. Thus, we may be able to prove or distinguish the fiducial and $3\sigma$ models by the observed PISN rate. This will help us to constrain the origin of binary BHs and the $^{12}$C$(\alpha, \gamma)^{16}$O reaction rate. PISN ejecta mass estimates from light curves and spectra obtained by follow-up observations would also be important to constrain the $^{12}$C$(\alpha, \gamma)^{16}$O reaction rate.Comment: 4 pages, 4 figures, submitte

Geotechnical Aspect of Damage In Adapazari City During the 1999 Kocaeli, Turkey, Earthquake

This report summerizes detailed investigation on the structural damage and its geotechnical condition in the Adapazaý City, Turkey, during the 1999 Kocaeli earthquake by the reconnaissance team of the Japanese Geotechnical Society. Damages to individual buildings were investigated along several streets in the downtown area. A little rough investigation was made almost all downtown area, in which damages were classified by its cause, i.e., inertia force or soil liquefaction. These investigations as well as hearing investigation and areal investigation by means of helicopters made clear the area where there was an island a few hundred years ago by which the name of Adapazarý i.e., ada (island) + pazarý (market), came from. In addition, the damage in the Adapazarý City is shown to be strongly affected by the ground condition because damage caused by liquefaciton was observed only outside the old island and areas where significant structural damage was observed were concentrated near the boundary between the old riverbed and island

Analyses of Liquefaction-Induced Deformation of Grounds and Structures by a Simple Method

The authors proposed a simple method to estimate liquefaction-induced deformation of grounds and structures. Adaptability of the method to the settlement of footings was studied. Centrifuge tests for the footing of transmission tower were selected to demonstrate the adaptability of the method. Analyses were carried out under the same conditions of the centrifuge tests. By comparing the analyzed results with the tested results, it was concluded that the effect of thickness of liquefied layer and soil density on the settlement of footing can be evaluated well by the simple method. Effect of countermeasures on the settlement of footing also could be evaluated well

Effective Stress Analysis by Shear Strain Controllable Model and its Application to Centrifuge Shaking Model Test

Effective stress FEM which is able to control the growth of shear strains is proposed. Its validity is firstly confirmed through the simulation of undrained cyclic torsional shear tests. Then, it is applied to simulation of centrifuge shaking model tests; the experimental model consists of a caisson type quay wall and reclamation laid on the sand layer. Development of shear strain is shown to be controlled arbitrary keeping the excess porewater pressure generation unchanged through the simulation of undrained cyclic torsional shear test, which indicates that proposed model can be applicable to variety of soils with different density and fines contents. Displacement is shown to be controlled keeping excess porewater pressure generation constant in the centrifugal model, too, and good agreement is obtained between test and analysis by controlling the parameter for shear strain development