Seismic performance evaluation of an infilled rocking wall frame structure through quasi-static cyclic testing

Earthquake investigations have illustrated that even code-compliant reinforced concrete frames may suffer from soft-story mechanism.This damage mode results in poor ductility and limited energy dissipation.Continuous components offer alternatives that may avoid such failures.A novel infilled rocking wall frame system is proposed that takes advantage of continuous component and rocking characteristics.Previous studies have investigated similar systems that combine a reinforced concrete frame and a wall with rocking behavior used.However,a large-scale experimental study of a reinforced concrete frame combined with a rocking wall has not been reported.In this study,a seismic performance evaluation of the newly proposed infilled rocking wall frame structure was conducted through quasi-static cyclic testing.Critical joints were designed and verified.Numerical models were established and calibrated to estimate frame shear forces.The results evaluation demonstrate that an infilled rocking wall frame can effectively avoid soft-story mechanisms.Capacity and initial stiffness are greatly improved and self-centering behavior is achieved with the help of the infilled rocking wall.Drift distribution becomes more uniform with height.Concrete cracks and damage occurs in desired areas.The infilled rocking wall frame offers a promising approach to achieving seismic resilience.

Nonlinear pushover analysis of infilled concrete frames

Six reinforced concrete frames with or without masonry infills were constructed and tested under horizontal cyclic loads. All six frames had identical details in which the transverse reinforcement in columns was provided by rectangular hoops that did not meet current ACI specifications for ductile frames. For comparison purposes, the columns in three of these frames were jacketed by carbon-fiber-reinforced-polymer （CFRP） sheets to avoid possible shear failure. A nonlinear pushover analysis, in which the force-deformation relationships of individual elements were developed based on ACI 318, FEMA 356, and Chen＇s model, was carried out for these frames and compared to test results. Both the failure mechanisms and impact of infills on the behaviors of these frames were examined in the study. Conclusions from the present analysis provide structural engineers with valuable information for evaluation and design of infilled concrete frame building structures.

Strength and stiffness reduction factors for infilled frames with openings

Framed structures are usually infilled with masonry walls. They may cause a significant increase in both stiffness and strength, reducing the deformation demand and increasing the energy dissipation capacity of the system. On the other hand, irregular arrangements of the masonry panels may lead to the concentration of damage in some regions, with negative effects; for example soft story mechanisms and shear failures in short columns. Therefore, the presence ofinfill walls should not be neglected, especially in regions of moderate and high seismicity. To this aim, simple models are available for solid infills walls, such as the diagonal no-tension strut model, while infilled frames with openings have not been adequately investigated. In this study, the effect of openings on the strength and stiffness of infilled frames is investigated by means of about 150 experimental and numerical tests. The main parameters involved are identified and a simple model to take into account the openings in the infills is developed and compared with other models proposed by different researchers. The model, which is based on the use of strength and stiffness reduction factors, takes into account the opening dimensions and presence of reinforcing elements around the opening. An example of an application of the proposed reduction factors is also presented.

An approach to measure infill matric suction of irregular infilled rock joints under constant normal stiffness shearing

Rock joints infilled with sediments can strongly influence the strength of rock mass. As infilled joints often exist under unsaturated condition, this study investigated the influence of matric suction of infill on the overall joint shear strength. A novel technique that allows direct measurement of matric suction of infill using high capacity tensiometers(HCTs) during direct shear of infilled joints under constant normal stiffness(CNS) is described. The CNS apparatus was modified to accommodate the HCT and the procedure is explained in detail. Joint specimens were simulated by gypsum plaster using threedimensional(3D) printed surface moulds, and filled with kaolin and sand mixture prepared at different water contents. Shear behaviours of both planar infilled joints and rough joints having joint roughness coefficients(JRCs) of 8-10 and 18-20 with the ratios of infill thickness to asperity height(t/a)equal to 0.5 were investigated. Matric suction shows predominantly unimodal behaviour during shearing of both planar and rough joints, which is closely associated with the variation of unloading rate and volumetric changes of the infill material. As expected, two-peak behaviour was observed for the rough joints and both peaks increased with the increase of infill matric suction. The results suggest that the contribution of matric suction of infill on the joint peak normalised shear stress is relatively independent of the joint roughness.

Experimental Investigation to Establish the Possibility of Realistic Simulation of the Behavior of Single Storey—One Bay Infilled R.C.Frames in Scale 1:9,Subjected to Horizontal Cyclic Loading

In order to study the dynamic behaviour of construction,specifically seismic response of structures,as many researchers did,we have resorted to modelling methods,based on the scaled internal forces.Therefore,this research includes results of an experimental investigation aimed to establish the possibility of realistic simulations of the cyclic response of small-scale models of one bay,one-storey reinforced concrete frames with masonry infills as a preliminary step for simulating the dynamic response of such structural.So,the specimens constructed were 1:9 scale R/C frames.These 1:9 scale infill frames were constructed with prototype materials and were tested in an extensive experimental sequence representing specimens of a scale near the prototype(1:3).The tested laboratory models include 1:3 scale infilled R/C frames that were built from original material such as steel,concrete and masonry infills(hollow masonry units and mortar).With the same scale,geometry and construction materials used for the construction of a 1:3 scale 5-story three dimensional building.This program consisted of 16 models,5 bare and 11 masonry infilled.all models refer to single-storey one-bay 1:9 scale as for the original structure and a one third of the scale(1:3)as for the prototype(1:3).The reinforced concrete specimens were designed in such a way as to prevent shear failure of the columns.Finally,the present paper was carried out in the Laboratory of Strength of Materials and Structures in the Department of Civil Engineering at Aristotle University of Thessaloniki.

Performance evaluation of low-rise infilled reinforced concrete frames designed by considering local effects on column shear demand

The interactions between reinforced concrete(RC)frames and infill walls play an important role in the seismic response of frames,particularly for low-rise frames.Infill walls can increase the overall lateral strength and stiffness of the frame owing to their high strength and stiffness.However,local wall-frame interactions can also lead to increased shear demand in the columns owing to the compressive diagonal strut force from the infill wall,which can result in failure or in serious situations,collapse.In this study,the effectiveness of a design strategy to consider the complex infill wall interaction was investigated.The approach was used to design example RC frames with infill walls in locations with different seismicity levels in Thailand.The performance of these frames was assessed using nonlinear static,and dynamic analyses.The performance of the frames and the failure modes were compared with those of frames designed without considering the infill wall or the local interactions.It was found that even though the overall responses of the buildings designed with and without consideration of the local interaction of the infill walls were similar in terms the overall lateral strength,the failure modes were different.The proposed method can eliminate the column shear failure from the building.Finally,the merits and limitations of this approach are discussed and summarized.

Experimental and numerical simulation of bird-strike performance of lattice-material-infilled curved plate

The anti-bird-strike performance of a lattice-material-infilled curved plate is investigated herein.Since automatically filling the curved structure by classical lattice material filling methods will cause a large number of manufacturing defects,a space-dependent lattice material filling method for the curved plate is firstly proposed in this paper Next,using a face-centered cubic lattice,a lattice-material-infilled test piece with a hollow ratio of 40.8%is built.The test pieces are manufactured via additive manufacturing using titanium alloy.In bird-strike experimental tests,the test pieces are crashed against gelatin birds at an impact velocity of 200 m/s.Dynamic strain gauges are used to record the crash history and the results are discussed.Furthermore,a numerical analysis to simulate the bird-strike experiment is performed.The results from the experimental tests and numerical simulation agree well.This work shows that the lattice-material-infilled curved plate yields promising bird-strike resistance.Therefore,lattice-infilled materials are feasible for protecting aerospace components against bird-strike as well as for reducing the component weight.

Meter-Scale Thin-Walled Structure with Lattice Infill for Fuel Tank Supporting Component of Satellite:Multiscale Design and Experimental Verification

Lightweight thin-walled structures with lattice infill are widely desired in satellite for their high stiffness-to-weight ratio and superior buckling strength resulting fromthe sandwich effect.Such structures can be fabricated bymetallic additive manufacturing technique,such as selective laser melting(SLM).However,the maximum dimensions of actual structures are usually in a sub-meter scale,which results in restrictions on their appliance in aerospace and other fields.In this work,a meter-scale thin-walled structure with lattice infill is designed for the fuel tank supporting component of the satellite by integrating a self-supporting lattice into the thickness optimization of the thin-wall.The designed structure is fabricated by SLM of AlSi10Mg and cold metal transfer welding technique.Quasi-static mechanical tests and vibration tests are both conducted to verify the mechanical strength of the designed large-scale lattice thin-walled structure.The experimental results indicate that themeter-scale thin-walled structure with lattice infill could meet the dimension and lightweight requirements of most spacecrafts.

A novel production data analysis method for multi-fractured horizontal wells with infill well-caused fracture interference

Tightening the well spacing for unconventional tight reservoirs is an efficient technique to enhance oil and gas recoveries.Infill well-caused fracture connection between wells is widely reported in the field with small well spacing.This will make it difficult to make formation evaluation and fracture characterization between wells compared to single well cases.In this paper,a novel production data analysis(PDA)method is proposed for fracture characterization with the consideration of interwell fracture connections after the hydraulic fracturing of the infill.The PDA method is based on a semianalytical model,in which the small-scaled fractures are treated with the concept of stimulated reservoir volume(SRV).Thus,the fracture connections between wells are classified into three types,including SRV,fractures,and both SRV and fractures.The physical model is discretized into several linear flow regions,so the mathematical model can be solved semianalytically.An integrated workflow is proposed to analyze the production data for the wellpad,and three steps are mainly included in the workflow,including PDA for the parent well before infill,PDA for the parent well after infill,and PDA for the infill well.In each step,the production performance in the early linear and bilinear flow regimes are analyzed with approximate solutions in the square and fourth root-of-time plots.Because only the relationship between unknown model parameters can be obtained with the approximate solutions,history matching to the production data in log-log plots is further used to determine each unknown parameter.The PDA method is benchmarked with a synthetic case generated by the numerical simulator tNavigator and a field case from Southwestern China.The results show that both good matches and precise parameters can be obtained with the proposed PDA method.The connected fracture number will not be sensitive in PDA when the wells are connected with high-conductive dSRV.The innovation of this paper is that a practical method is provided for PDA analysis of well groups with fracture connection,and it will be a good technique for fracture characterization and well-interference analysis for tight formations.

Airfoil Shape Optimisation Using a Multi-Fidelity Surrogate-Assisted Metaheuristic with a New Multi-Objective Infill Sampling Technique

This work presents multi-fidelity multi-objective infill-sampling surrogate-assisted optimization for airfoil shape optimization.The optimization problem is posed to maximize the lift and drag coefficient ratio subject to airfoil geometry constraints.Computational Fluid Dynamic(CFD)and XFoil tools are used for high and low-fidelity simulations of the airfoil to find the real objective function value.A special multi-objective sub-optimization problem is proposed for multiple points infill sampling exploration to improve the surrogate model constructed.To validate and further assess the proposed methods,a conventional surrogate-assisted optimization method and an infill sampling surrogate-assisted optimization criterion are applied with multi-fidelity simulation,while their numerical performance is investigated.The results obtained show that the proposed technique is the best performer for the demonstrated airfoil shape optimization.According to this study,applying multi-fidelity with multi-objective infill sampling criteria for surrogate-assisted optimization is a powerful design tool.

Production characteristics and displacement mechanisms of infilling polymer-surfactant-preformed particle gel flooding in post-polymer flooding reservoirs:A review of practice in Ng3 block of Gudao Oilfield

The pilot test of infilling polymer-surfactant-preformed particle gel(PPG)flooding has been successfully implemented after polymer flooding in Ng3 block of Gudao Oilfield in China.However,the production characteristics and displacement mechanisms are still unclear,which restricts its further popularization and application.Aiming at this problem,this paper firstly analyzes the production performance of the pilot test and proposed four response types according to the change of water cut curves,including W-type,U-type,V-type response,and no response.Furthermore,the underlying reasons of these four types are analyzed from the aspects of seepage resistance and sweep efficiency.The overall sweep efficiency of gradual-rising W-type,gradual-decreasing W-type,and early V-type response increases from 0.81 to 0.93,0.55 to 0.89,and 0.94 to 1,respectively.And the sum of seepage resistance along the connection line between production well and injection well for U-type and delayed V-type response increases from 0.0994 to 0.2425,and 0.0677 to 0.1654,respectively.Then,the remaining oil distribution after polymer flooding is summarized into four types on the basis of production and geological characteristics,namely disconnected remaining oil,streamline unswept remaining oil,rhythm remaining oil,and interlayer-controlled remaining oil.Furthermore,the main displacement mechanisms for each type are clarified based on the dimensionless seepage resistance and water absorption profile.Generally,improving connectivity by well pattern infilling is the most important for producing disconnected remaining oil.The synergistic effect of well pattern infilling and polymer-surfactant-PPG flooding increases the dimensionless seepage resistance of water channeling regions and forces the subsequent injected water to turn to regions with streamline unswept remaining oil.The improvement of the water absorption profile by polymer-surfactant-PPG flooding and separated layer water injection contributes to displacing rhythm remaining oil and interlayer-controlled remaining oil.Finally,the paper analyzes the relationships between the remaining oil distribution after polymer flooding and production characteristics of infilling polymer-surfactant-PPG flooding.The study helps to deepen the understanding of infilling polymer-surfactant-PPG flooding and has reference significance for more commercial implementations in the future.

Research Progress of Aerodynamic Multi-Objective Optimization on High-Speed Train Nose Shape

The aerodynamic optimization design of high-speed trains(HSTs)is crucial for energy conservation,environmental preservation,operational safety,and speeding up.This study aims to review the current state and progress of the aerodynamic multi-objective optimization of HSTs.First,the study explores the impact of train nose shape parameters on aerodynamic performance.The parameterization methods involved in the aerodynamic multiobjective optimization ofHSTs are summarized and classified as shape-based and disturbance-based parameterizationmethods.Meanwhile,the advantages and limitations of each parameterizationmethod,aswell as the applicable scope,are briefly discussed.In addition,the NSGA-II algorithm,particle swarm optimization algorithm,standard genetic algorithm,and other commonly used multi-objective optimization algorithms and the improvements in the field of aerodynamic optimization for HSTs are summarized.Second,this study investigates the aerodynamic multi-objective optimization technology for HSTs using the surrogate model,focusing on the Kriging surrogate models,neural network,and support vector regression.Moreover,the construction methods of surrogate models are summarized,and the influence of different sample infill criteria on the efficiency ofmulti-objective optimization is analyzed.Meanwhile,advanced aerodynamic optimization methods in the field of aircraft have been briefly introduced to guide research on the aerodynamic optimization of HSTs.Finally,based on the summary of the research progress of the aerodynamicmulti-objective optimization ofHSTs,future research directions are proposed,such as intelligent recognition technology of characteristic parameters,collaborative optimization of multiple operating environments,and sample infill criterion of the surrogate model.

An Experimental Study of Composite Columns Filled with Eucalyptus nitens Timber under Axial Compression

Eucalyptus nitens(E.nitens)has been much used for producing paper but also shows promise for structural applications.In this study,static compressive tests were undertaken to examine its suitability to be used in an innovative composite column.The composite column was comprised of a rectangular steel tube with E.nitens timber infill.The nonlinear compressive behaviour of the composite column filled with E.nitens wood for both dry and wet conditions was examined.The same tests on rectangular steel tubes and bare dry and wet E.nitens samples were also undertaken as a comparison.For samples with different conditions,the ultimate capacity was evaluated and the effect of each condition on the compressive behaviour of the composite column was clarified.The steel tubes showed greater ductile behaviour,and more ductility was found in the wet samples.The steel tubes with E.nitens timber infill samples exhibited a greater linear elastic range connected with higher maximum loads,while the bare timber samples could support only lower maximum loads.The results from this research were promising for the use of rectangular steel tubes with E.nitens timber infill in structural applications.

学用SAS软件捷径(3) 第三讲读入外部数据并作统计分析

汤旦林，李晓强．学用ＳＡＳ软件捷径（３）．数理统计与管理，１９９７，１６（４），４６～４８．进行统计分析时，利用外部文件输入数据既安全又方便。学会适当调用ＳＡＳ中的统计过程，并对结果作正确解释的关键在于：事先掌握一定的统计知识。

鲁西北平原地下水补给空间演化规律

采用改进后的INFIL3.0模型计算鲁西北平原的地下水补给,分析灌溉和城市化因素影响下,地下水补给量的空间演化规律。计算结果表明:2001-2009年,鲁西北平原地下水补给量为105 mm,补给系数为0.13,计算结果得到了验证。鲁西北平原地下水补给时空变异性较大。在时间上,地下水补给年际变化较大,呈增加趋势,年内有2个峰值,分别在4月和10月。在空间上,地下水补给由西北向东南增大,空间分布差异受灌溉影响显著。地下水补给量的空间演化结果显示,鲁西北平原存在一定的节水空间,城市化扩张会导致补给量减少,弱透水面面积增加10%,补给量减少10mm。模型计算结果可为区域地下水资源评价提供技术支持。

基于INFIL3.0模型的地下水补给计算与分析

采用扩展后的INFIL3.0模型计算了石津灌区根区层下净入渗补给量和潜在入渗补给系数,并分析了其时空变化规律。计算结果显示,石津灌区多年平均净入渗补给量为79mm,多年平均潜在入渗补给系数为0.135;根区层下净入渗补给量和潜在入渗补给系数的空间变异性主要表现为渠灌区>井渠双灌区>井灌区,时间变异性表现为入渗补给量峰值出现在强降雨期间。最后,从水量均衡要素的角度分析了入渗补给过程,表明降雨是引起入渗补给的主要因素,当前灌溉制度是合理的。

Numerical investigation on the effect of depletion-induced stress reorientation on infill well hydraulic fracture propagation

Depletion-induced stress change causes the redistribution of stress field in reservoirs,which can lead to the reorientation of principal stresses.Stress reorientation has a direct impact on fracture propagation of infill wells.To understand the effect of stress reorientation on the propagation of infill well’s fractures,an integrated simulation workflow that combines the reservoir flow calculation and the infill well hydraulic fracturing modeling is adopted.The reservoir simulation is computed to examine the relationship between the extent of stress reversal region and reservoir properties.Then,the hydraulic fracturing model considering the altered stress field for production is built to characterize the stress evolution of secondary fracturing.Numerical simulations show that stress reorientation may occur due to the decreasing of the horizontal stresses in an elliptical region around the parent well.Also,the initial stress difference is the driving factor for stress reorientation.However,the bottom hole pressure,permeability and other properties connected with fluid flow control timing of the stress reorientation.The decrease of the horizontal stresses around the parent well lead to asymmetrical propagation of a hydraulic fracture of the infill well.The study provides insights on understanding the influence of stress reorientation to the infill well fracturing treatment and interference between parent and infill wells.

Effects of pre-existing cracks and infillings on strength of natural rocks--Cases of sandstone, argillite and basalt

This study aims to examine the influence of pre-existing discontinuities on the strengths of four natural rocks of different origins.A series of unconfined compression tests was performed on specimens of two types of sandstones,argillite and basalt that contain open and filled cracks.It was found that the presence of cracks tends to decrease the overall strength for all studied rocks;however,the magnitude of strength reduction is related to the property of rock.The larger strength decrease was observed for the relatively harder argillite and basalt,compared to the softer sandstone.It was also found that the infill material could increase the strength of rock specimens,while the obtained strength depended on the characteristics of the fill material.

An effective simplified model of composite compression struts for partially-restrained steel frame with reinforced concrete infill walls

To resolve the issue regarding inaccurate prediction of the hysteretic behavior by micro-based numerical analysis for partially-restrained（PR）steel frames with solid reinforced concrete（RC）infill walls,an innovative simplified model of composite compression struts is proposed on the basis of experimental observation on the cracking distribution,load transferring mechanism,and failure modes of RC infill walls filled in PR steel frame.The proposed composite compression struts model for the solid RC infill walls is composed ofαinclined struts and main diagonal struts.Theαinclined struts are used to reflect the part of the lateral force resisted by shear connectors along the frame-wall interface,while the main diagonal struts are introduced to take into account the rest of the lateral force transferred along the diagonal direction due to the complicated interaction between the steel frame and RC infill walls.This study derives appropriate formulas for the effective widths of theαinclined strut and main diagonal strut,respectively.An example of PR steel frame with RC infill walls simulating simulated by the composite inclined compression struts model is illustrated.The maximum lateral strength and the hysteresis curve shape obtained from the proposed composite strut model are in good agreement with those from the test results,and the backbone curve of a PR steel frame with RC infill walls can be predicted precisely when the inter-story drift is within 1%.This simplified model can also predict the structural stiffness and the equivalent viscous damping ratio well when the inter-story drift ratio exceeds 0.5%.

Performance of masonry enclosure walls:lessons learned from recent earthquakes

This paper discusses the issue of performance requirements and construction criteria for masonry enclosure and infill walls. Vertical building enclosures in European countries are very often constituted by non-load-bearing masonry walls, using horizontally perforated clay bricks. These walls are generally supported and confined by a reinforced concrete frame structure of columns and beams/slabs. Since these walls are commonly considered to be nonstructural elements and their influence on the structural response is ignored, their consideration in the design of structures as well as their connection to the adjacent structural elements is frequently negligent or insufficiently detailed. As a consequence, nonstructural elements, as for wall enclosures, are relatively sensitive to drift and acceleration demands when buildings are subjected to seismic actions. Many international standards and technical documents stress the need for design acceptability criteria for nonstructural elements, however they do not specifically indicate how to prevent collapse and severe cracking, and how to enhance the overall stability in the case of moderate to high seismic loading. Furthermore, a review of appropriate measures to improve enclosure wall performance and both in-plane and out-of-plane integrity under seismic actions is addressed.