bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite Element Calculation about Stress Concentration Coefficient of Welded Butt Joints Based on the ABAQUS
Authors: He Bo Lin , Zhang Xiao Dong
Published: August 2011

Stress concentration coefficient of welded joints has a crucial influence on mechanical properties of welded structures. Geometrical parameters of welded joints seriously affect the stress concentration coefficient. In order to increase the mechanical properties and using safety of welded structures, it has great significance for reducing stress concentration coefficient and improving the mechanical properties of welded structures by researching and improving the geometry of welded joints . In this paper, the effect of weld toe inclination angle θ and weld edge transition arc radius r on the stress concentration coefficient of welded butt joints were analyzed by using ABAQUS finite element program, and the change rule of stress concentration coefficient with the variation of the two parameters was also researched. The calculation results indicate that reducing weld toe inclination angle or increasing transition arc radius can effectively decrease the stress concentration coefficient of welded butt joints, so as to improve the mechanical properties of welded structures. For the safe use of welded structures, the true weld edge transition arc radius r should be greater than 3mm, and weld toe inclination angle θ should be smaller than 30°.
Study on Control Strategy of Regenerative Braking in Electric Vehicles
Authors: Han Zhao Lin , Wang Yang Yang , Zhao Jing , Liu Feng
Published: August 2011

Regenerative braking of electric vehicles can not only conserve energy, but also increase driving range. Regenerative braking control strategy formulate proportional relation of regenerative braking and mechanical braking, how to distribution regenerative braking and mechanical braking has become the key problem of raising regenerative braking energy[1]．This paper research on the distribution of braking force in the braking process, formulate mathematical models and put forward a new control strategy. The new control strategy is simulated and analyzed in the ADVISOR. Used new control strategy, the results indicate that fuel economy, emission and dynamic of simulation vehicle are improved.
Studies of a High Voltage Management System in Electric Vehicles
Authors: Dai Hai Feng , Wei Xue Zhe , Sun Ze Chang , Chang Xue Yu
Published: August 2011

Vehicle safety is one of the most important design elements for all types of vehicles designed for use on public streets or roadways. Compared with traditional vehicles, besides other safety issues to be considered, a new issue that is the high voltage management problem should be taken in consideration very carefully in the electric vehicle development. This paper analyses the high voltage system in the electric vehicle and proposed a high voltage management system which implements several functions like power-up and power-down control of the high voltage system, high-voltage-circuit interlock protection, protection of electric leakage of the HV system etc. Because of the high voltage management, the electrical safety goals could be achieved and the protection of human being from high voltage hazardous becomes possible.
Response Calculation for NOPD Beam by an Improved Algorithm Based on the Endochronic Theory and Test Verification
Authors: Wang Wei , Li Yu Yan
Published: August 2011

Non-Obstructive Particle Damping (NOPD) is a new damping technique which is based on traditional particle damping and impact damping technique. NOPD Structure has a good effect on decreasing sound and vibration. A new improved algorithm based on the endochronic theory is researched in the paper. Response calculation by the algorithm and tests for NOPD beam have been done in conditions of one, two and three holes filled with tungsten particles. Results show it feasible to calculate the response of NOPD structure by the improved algorithm, which affords an effective analysis method for engineering application of NOPD technique.
Stiction Failure Mechanisms of the Micromachined Electrostatic Comb-Drive Structures
Authors: Xu Yi Shen , Gu Ji Hua , Tao Zhi
Published: August 2011

Stiction is one of the most important and almost unavoidable problems in MEMS, which usually occurs when the restoring forces of the microstructures are unable to overcome the interfacial forces. Stiction could compromise the performance and reliability of the MEMS devices or may even make them malfunction. One of the pivotal process of advancing the performance and reliability of MEMS is to comprehend the failure modes and failure mechanisms of these microdevices. This article provides a critical investigation on the stiction failure mechanisms of the micromachined electrostatic comb-drive structures, which is significant to improve the reliability of microdevices, especially for microfilters, microgrippers, microaccelerometers, microgyroscopes, microrelays, and so on.
A Selective and Sensitive Method for the Determination of Molybdenum in High Grade Pipeline Steels
Authors: Shao Xiaodong
Published: August 2011

Pipeline system is the main form of transportation for oil and natural gas. High grade pipeline steel can effectively improve the security of long-distance transportation and to reduce costs, will become the main steel for gas pipeline project. A highly selective and sensitive spectrophotometric method for the determination of molybdenum in high grade pipeline steel has been presented. This method was based on the chromogenic reaction between molybdenum(V) and sodium thiocyanate. Employing stannous chloride as a reductant, molybdenum(VI) was reduced to molybdenum(V) at the room temperature. The obtained molybdenum(V) formed an orange-red-colored (1:5) ligand complex with thiocyanate. The absorbance of the complex was measured at 470nm, and the molar extinction coefficient (e) is 1.75´104L·mol-1·cm-1. Under the optimum reaction conditions the absorption value was proportional to the concentration of molybdenum in the range of 0.11%~0.89% (mass fraction), and the relative standard deviation was less than 3.0%. The proposed method was free from the interference from a large number of analytical important elements and has been applied satisfactorily to the determination of molybdenum in X80 pipeline steel and X70 pipeline steel samples with the improved accuracy and precision.
Idling Natural Characteristic Analysis of the Torsion Absorber with Dual Mass Flywheel
Authors: Meng Xian Jie , Li Jun Wei
Published: August 2011

Based on the analysis of two kinds of torsion absorber of automobile power train, a power train idling vibration model with nine degrees of freedom is established, the generalized Jacobin algorithms and the compiled Matlab procedures are used to calculate the idling natural frequency and idling natural vibration model. The results show that the dual mass flywheel torsion absorber can keep the power train from idling resonance compared with the clutch torsion absorber and play a good role in attenuating the low frequency torsion vibration of power train.
Restraint of Period Doubling Bifurcation and Chaos Gait of the Biped Robot Based on Passive Dynamic Principle
Authors: Wu Xiao Guang , Zhao Jie , Zang Xi Zhe
Published: August 2011

Considering high sensitivity of the walking gait of the biped passive dynamic robot to its own parameters, the paper obtains a more simple and efficient restraint strategy by analyzing the restraint of the ankle-angle to the period doubling bifurcation and chaos, based on the model of humanoid forward-offset round feet. The forward offset round feet model is used to construct the dynamic equation of the passive walking and the numerical solution is for the final state of the model; while the robot’s own parameters are fixed and the slope is increased step by step, the gait features in terms of different phases of the angle are simulated and analyzed; then the self-adjustment of the gait shows that the restraint to the period doubling bifurcation or the chaos gait can be performed only by the adjustment of the ankle-angle. The result shows the superiority of our research on some aspects: the restraint to the period doubling bifurcation or the chaos gait, the reveal of the passive dynamic walking mechanism that parameters restrict each other, and the design of the control strategies in more complicated environment.
Application of Oxyhydrogen Energy to Underwater Vehicle Thermal Power System
Authors: Zhu Rui , Luo Lan , Liang Wei Ge
Published: August 2011

The possibility of oxyhydrogen energy, which use real-time generated Hydrogen and Oxygen as its source, was analyzed. A special torpedo thermal power system, which uses oxyhydrogen energy, was put forward. The key technology to realize the system was discussed. The problems which the Open-cycle torpedo thermal power system encounters was solved by the closed-cycle technology, such as exhaust noise, flight path, the working efficiency of engine was influenced by the intensity of pressure of seawater.
System Modeling and Analysis of Wind Turbine Blade Grinding Robot
Authors: Bu Chi Wu , Zhang Li Xun
Published: August 2011

A mobile grinding robot is present here for the wind turbine blade grinding work. The robot is a mobile manipulator equipped with a grinding wheel. A mobile manipulator robot is built up with a mobile platform and a robotic arm mounted on it. The dynamic model of the robot is built, and the dynamic model of the two subsystems is derived from it, so the dynamic coupling items can be deduced. In order to discover how the coupling force influence the robotic manipulator, the SimMechanics model of the robot is built up and the simulation research is carried out by the built model. The results show the influence of coupling force on the manipulator.
Numerical Simulation of Continuous Extrusion Extending Forming under the Large Expansion Ratio for Copper Strip
Authors: Yun Xin Bing , Yao Ming Liang , Wu Yang , Song Bao Yun
Published: August 2011

Continuous extrusion under the large expansion ratio is an advanced forming process for manufacturing copper strip, preventing mould structure, die structure, expansion chamber structure and the shape of the billet section is important process paraments of deformation. Based on the characteristic of the forming process, the model of rigid-plastic FEM on DEFORM-3D is established and the numerical simulation of continuous extrusion forming process of the copper strip is carried. The metal flow regularity and the mean-square deviation of velocity with the different process paraments is analyzed. As the result, when using the drum form of preventing mould with promote flow angle and the die with variable calibrating strap, the mean-square deviation of velocity is 0.58. When the second extending angle is 134°, the mean-square deviation of velocity is 0.23. When size of billet is 30 x 1.64 mm2, the mean-square deviation of velocity is only 0.19.
Statics Analysis on Beam Structures of Large Five-Axis Machining Center Based on ANSYS
Authors: Wang Yan Qing , Zhong Gao Yan , Chang Yong Biao , Liu Guo Xin
Published: August 2011

The stroke and the material characteristics of the large five-axis machining center were expounded; a structure similar to the truss of the reinforced beam plates was designed according to the design requirements of the beam structure, this structure could make the frame gain high rigidity in small size, the frame made by the rods could be constituted with high rigidity, the overall rigidity of the machining center could be improved 23% - 25%; three different beam structures were designed, and the finite element analysis software ANSYS was carried out to analyze their static characteristics, the maximum deformations in three directions X, Y, Z were obtained; compared with other structures through the comparisons on mass, stiffness and performance, the optimal structure was obtained, its mass was 1818Kg, and its maximum deformations in X, Y, Z directions were 0.45mm, 0.07mm and 0.13mm, respectively.
Investigation of Forging Process Parameters Effects on Die Fatigue Life Using Numerical Methods
Authors: Bagheri Gh. Seyed , Soleymani Yazdi M. Reza , Tahmasebi M.
Published: August 2011

In this study, the hot forging process of spline hub was simulated using the finite volume method. The proposed simulation model was compared with experimental samples and approved. Then, stress analysis of the rigid die was undertaken using the finite element method. On the basis of proposed model, the full factorial design of experiments was performed for investigating the influence of forging temperature and flash thickness on the die fatigue life. Results show that the increase in forging temperature and flash thickness, both cause the increase in the fatigue life. It is also shown that the effect of forging temperature on the fatigue life is greater than that of flash thickness. In drop-hammer forging, when number of blows decreases, the die fatigue life increases considerably.
Analysis of the Impact of Vertical Stiffness of Tire on Macpherson Front Suspension on the Basis of ADAMS/CAR
Authors: Wang Ze Peng , Cui Wen Liang
Published: August 2011

Macpherson front suspension model was established by ADAMS/CAR software. The simulation of the parallel wheel traveling and the dynamic analysis of suspension was carried out when the vertical stiffness of tire is 170N/mm and 190N/mm, respectively. Simulation result shows that the enhancement of the vertical stiffness of tire has no influence on the alignment parameters of the front wheel of suspension, but can increase the arm of force of kingpin caste and the stiffness of suspension, decreases the dive, lift and scrub radius, improve the steering returnability and the handling and stability. Analytical result can be used to direct the design of the suspension and tire of automobile.
Defects Detection for Casting of Railway Freight Car Using X-Ray Radiography
Authors: Zou Yong Ning , Li Jian Wei , Wang Jue
Published: August 2011

In order to improve detection efficiency of casting bolster and side frame of railway freight car, the method to automatically detect railway casting porosity and shrinkage cavity using watershed transformation based on X-ray digital radiography is presented. Firstly, while castings of a bolster and a side frame are scanned by 9Mev X-ray digital radiography system, the DR images are obtained. Then one of interested regions is selected in an image. Defects segmentation is implemented by using watershed transformation algorithm in this paper. Lastly, defects area and occupy rate are acquired by analyzing and computing, so that we can judge the casting quality. The experimental results show that defect regions and contours can be accurately acquired. This method has high robustness and practicality. It improves the efficiency of automated inspection of railway castings.
Numerical Simulation of Solidification Process for Impeller Investment Casting
Authors: Zhang Jie , Li Kang Wen , Ye Hai Wei , Zhang Dong Qi , Wu Peng Wei
Published: August 2011

Investment casting method can fabricate the impeller slots with non-uniform thickness and distorted surface. The process of investment casting can be simulated by employing ProCAST software. The mesh of the casting was introduced in the article. The influence about the initial temperature of shell on the defects of the casting and the pouring temperature and the pouring speed on the effective stress of the casting was studied in this article. When the initial temperature of shell was 400°C,there was no defect in the casting. The pouring temperature of the casting, will produce a very strong influence on the effective stress. When the pouring temperature in this article was 800°C, the maximum effective stress of the casting was 108MPa.
State-of-the-Art of Rotational Moulding Technique and its Application
Authors: Wang Yun , Zhang Kai , Dai Ya Chun , Liu Jiong , Zhang Yuan Yuan
Published: August 2011

With the rapid development of plastic products in the world and the increasingly sophistication of plastic technology, rotational moulding (RM), has become the most practical and irreplaceable way of producing the large and super large containers like tanks, tank, etc. Compared with injection moulding and blow moulding, RM has the characteristics of low cost and easy-to-use, and its application has been extended into many domains. The principle of rotational moulding and comparison of raw material by the requirement of rotational moulding is introduced. The paper emphasizes the introduction of state-of-the-art of RM equipment; also it points out the development of RM.
Static-Dynamic Properties of Reactive Powder Concrete with Blast Furnace Slag
Authors: Pan Huang Hsing , Peng Jen Po , Tai Yuh Shiou , Chang Chao Shun
Published: August 2011

Reactive powder concrete (RPC) containing blast furnace slag prepared for hydraulic structure with a designed strength of 150 MPa is examined. We first investigate mixture proportions of RPC to fit the strength requirement, and then, concentrate on the material with 50% replacement of silica fume by blast furnace slag to study seismic resistant properties. Results indicate that curing process and steel fiber can enhance the compressive strength, flexural strength, shear strength and fracture toughness. With 210°C curing, flexural strength of RPC containing 2% steel fibers reaches 91 MPa, almost three times without the fibers. Meanwhile, the shear strength is 47.8 MPa. Dynamic stress-strain curves determined by SHPB test display that the compressive strength of RPC increases with increasing applied strain rate. Applied strain rate dominates the stress-strain behavior and fracture energy of RPC. Toughness index of RPC is improved powerfully by adding a few steel fibers. The fracture toughness of RPC with 50% slag replacement comes to 1.08 MPa·m1/2, and reaches 2.67 MPa·m1/2 as 2% steel fibers are added.
Threshold Characteristics of Short Pulse Loads Causing Fracture in Concrete and Rocks
Authors: Smirnov Ivan V. , Petrov Yuri V. , Sudenkov Yuri V. , Cadoni Ezio
Published: August 2011

Results of experimental investigation of concrete and rocks under high rate loads of microsecond duration (2.5 µs) are presented. Tested samples are rectangular plates (150/150/15 mm) with a notch (70 mm long and 3 mm thick) containing a pre-crack (about 1 mm long). Dynamic loading was created utilizing electric wire explosion technique. An electric wire was placed between the faces of the notch at a distance of 20 mm from the tip of the pre-crack. After the wire explosion the trajectory of the extended crack and the fracture surface were studied. Measured dependence of the crack extension on the loading pulse energy gives the possibility of determining the threshold (minimal) amplitude of the load required to initiate fracture in the studied samples.
Characterisation of Aluminium Matrix Syntactic Foams under Static and Dynamic Loading
Authors: Altenaiji Mohamed , Schleyer Graham K. , Zhao Yo Yang
Published: August 2011

Development of a lightweight, strong and energy-absorbing material that has potential application for the protection of vehicles and occupants against impact and blast, is a difficult challenge facing the materials community. Aluminium matrix syntactic foams will be investigated as a possible core material as part of a multi-layered protection system for military vehicles. Aluminium matrix syntactic foams are composite materials consisting of an aluminium matrix implanted with hollow or porous ceramic particles. This paper investigates the mechanical properties of aluminium matrix syntactic foam with different sizes of ceramic micro-spheres and different grades of aluminium, fabricated by the pressure infiltration method. The static crushing behaviour of the foam was investigated under two test conditions using an Instron 4505 machine. Results are compared and discussed. The dynamic compressive response was investigated using a drop-weight impact test machine. It was found that the particle size of the ceramic micro-spheres and the grade of the aluminium metal have a significant effect on the energy absorption capacity of the material. The compressive strength of the syntactic foam was found to increase with increasing compressive strength of the metal matrix.
Influence of Free Water and Strain-Rate on the Shear Behaviour of Concrete
Authors: Forquin Pascal
Published: August 2011

Shear fracture (mode II) may be observed in concrete structures when subjected to confined or impact loading. Among the different techniques developed to investigate the shear strength of geomaterials, figures the Punch-Through Shear test (PTS test). It consists of a short cylinder with two cylindrical notches made on the lower and upper surfaces. Shear fracture is produced in the ligament due to the displacement of the central zone beside the peripheral zone. An experimental setup has been developed in LEM3 laboratory to measure the shear strength of concrete under quasi-static and dynamic loading. A high-speed hydraulic press allowed reaching strain-rates up to few per second. Steel and aluminium alloy confining rings have been used to induce a confining pressure in the fractured zone. Furthermore, radial notches have been performed in the specimen in order to deduce the radial stress at the ligament surface from the contact pressure between the confining ring and the outer surface of the specimen. The experimental results have been used to discuss the influence of free water and strain-rate on the shear behaviour of concrete.
Mechanical Characterization of Cement Composites Reinforced with Fiberglass, Carbon Nanotubes or Glass Reinforced Plastic (GRP) at High Strain Rates
Authors: Coppola Luigi , Cadoni Ezio , Forni Daniele , Buoso Alessandra
Published: August 2011

Advanced researches on concrete are directed toward investigating the behavior of reinforced concrete structures in severe conditions such as those promoted by impact loads. Some particular structures (protective shelters, nuclear reactor containment, offshore structures, military structures, chemical or Energy production plant) may be subjected to loading at very high rate of stress or strain caused by impact of missiles or flying objects, also by vehicle collisions or impulses due to explosions and earthquakes. Resistance to impact loads is guaranteed by using cementitious materials having both high strength and ductility. In order to improve ductility cementitious mortars with Glass Reinforced Plastics (GRP) replacing partially the natural sand were manufactured. Moreover, glass fiber (GF) reinforced mortars were produced to enhance toughness. For this scope two types of glass fibers were used different in length and diameter. Since the use of GRP and GF don’t produce any increase in strength of the mortars Carbon Nanotubes were added in the cement matrix to enhance tensile strength of the cementitious composite. Flexural, compressive and Hopkinson bar tests were carried out to evaluate the role of the different materials used. Replacing partially the natural sand with Glass Reinforced Plastics (GRP), compressive and flexural strength decrease (about 20%) with respect those of the reference mortar both on static and dynamic condition as a consequence of an anomalous air entrapment. Adding glass fibers (GF), GRP or/and Carbon Nanotubes (CNTs) no substantial improvement in terms of mechanical properties under static condition was occurred. The Dynamic Increase Factor of the reference mortar was higher than that of the reinforced mixtures, but fracture energy was lower. In particular, combined addition of carbon nanotubes and GRP determines an increase in the energy fracture. The higher the carbon nanotubes content, the higher both fracture energy and tensile strength because nanoparticles oppose to wave and crack propagation, increasing the high strain rate strength. GRP and CNTs reinforced mortars need more fracture energy to failure at 150 s-1 strain rate.
Analysis of the Strain-Rate Beahavior of a Basalt Fiber Reinforced Mortar
Authors: Asprone Domenico , Iucolano Fabio , Cadoni Ezio , Prota Andrea
Published: August 2011

Fiber reinforced inorganic materials, such as concrete or mortars, are expected to present good mechanical properties in case of high dynamic loading conditions, as those induced by impact or blast actions. Furthermore, basalt fibers, recently widely investigated in structural applications, are also expected to present good performance in case of high strain-rate dynamic conditions. The present paper presents the results of a dynamic characterization of basalt fiber reinforced mortar, carried out at DynaMat laboratory of the University of Applied Sciences of Southern Switzerland. Dynamic tensile failure tests have been conducted on mortar samples at selected strain rates, using a Modified Hopkinson bar apparatus.
Textile Reinforced Mortar at High Temperatures
Authors: Colombo Isabella , Colombo Matteo , Magri Anna , Zani Giulio , di Prisco Marco
Published: August 2011

Textile Reinforced Mortar (TRM) is a composite made by fine grained matrix and glass fabric reinforcement. The main advantages of this material are the reinforcement orientation in the tensile stress direction, no concrete cover requirement against corrosion and the capability to produce thin and light weight elements. Special attention was given by researchers to the time dependent loss in strength of AR-glass reinforcement embedded in a cement based matrix. Some research has shown durability models to calculate the amount to the strength loss related to material, humidity and temperature. Nevertheless, the behaviour of TRM when exposed to high temperature requires further investigations. A suitable experimental programme was planned to investigate the behaviour of TRM when exposed to high temperatures. Uniaxial tensile tests were performed after thermal cycle on 400 mm x 70 mm specimens 6 mm thick, reinforced with 2 layer of AR-glass fabric. Several thermal thresholds (20, 200, 400 and 600°C) were considered for the mechanical characterization in fire condition. Thermal cycles were performed in an oven using a heating rate of 30°C/h up to the maximum temperature and by a cooling branch at 15°C/h after a stabilization phase at the maximum temperature.
Existence of Optimal Energy Saving Parameters for Different Industrial Processes
Authors: Bratov Vladimir , Petrov Yuri V. , Volkov Grigory
Published: August 2011

It is demonstrated that energy input for fracture in many industrial processes can be optimised so that the energy cost of the process is minimised. Using a simple example of central crack it is shown that for a certain shape of the load pulse energy transmitted to the sample in order to initiate the crack has a strongly marked minimum. Received results indicate a possibility to optimise energy consumption of different industrial processes connected with fracture. Possible applications include drilling or rock pounding where energy input often accounts for the largest part of the process cost. Using this approach it will be possible to predict optimal operational parameters for bores, grinding machines, etc. and hence significantly reduce the process cost. In the second part of the paper the behaviour of energy input for initiation of fracture in conditions of contact interaction is studied. It is considered that a spherical particle is impacting the half-space. Stress field created as a result of the interaction can be estimated using the Hertz solution. Threshold particle velocity (and, hence, threshold kinetic energy) corresponding to initiation of rupture in the half-space can be found once the fracture criterion is defined. It will be shown that the value of this energy does significantly depend on load duration and has a marked minimum. Existence of energetically optimal modes of dynamic impact is claimed.
Evaluation of the Load Carrying Capacity of a Rockfall Protection Gallery
Authors: Ghadimi Khasraghy Sara , Röthlin Christina , Vogel Thomas
Published: August 2011

Mountainous areas of Switzerland are exposed to complex natural conditions, which combined with climate changes cause a variety of natural hazards. Rockfall is one of these hazards, and the risk associated with it tends to increase in recent years. The roads below the Lopper cliff at the shore of Lake Lucerne lead through one of these endangered areas. The roads are closed for traffic, following a rockfall incident in October 2009. Some rockfall protection galleries at the Lopper, which were built during 1979-1981, are subjected to a structural evaluation to allow for decisions on their further use. The current work covers estimation of the impact load carrying capacity of one of these galleries. The gallery analyzed is a cantilever pre-stressed concrete slab with variable thickness, covered by a cushion layer of soil. The behavior of the gallery is examined using finite element analyses as well as an analytical model based on a System of Multiple Degrees of Freedom (SMDF) method. The evaluation has shown that for the chosen loading case based on trajectory analyses with return periods of 30 years, the load carrying capacity of the gallery is satisfactory. However, for extreme rockfalls with return periods of 100 years, a local (punching) failure as well as a global (bending) failure can happen given that a critical section is hit
Effects of Short Fiber Reinforcement on the Local Damage of Concrete Plates under High Velocity Impact Loading
Authors: Beppu Masuhiro , Abadie Charles , Takahashi Jun , Ogawa Atsuhisa
Published: August 2011

This study presents the effects of short fiber reinforcement on the local damage of concrete plates subjected to high velocity impact. In a series of tests, three short fiber composite materials were used. Firstly, static bending tests were conducted to reveal mechanical properties in tension of the short fiber reinforced concrete. Then, high velocity impact tests were carried out to examine the effects of short fiber reinforcement on the local damage of concrete plates. Failure mode and strain behavior on the back surface of the short fiber reinforced concrete plates demonstrated that short fiber reinforcement was very effective in reducing the local damage.
Dynamic Response Analysis for Rigid Steel Portal Frames under Impact Loading
Authors: Komuro Masato , Kishi Norimitsu , Kurihashi Yusuke , Chen Wai Fah
Published: August 2011

In order to improve our basic understanding of the impact-resistant behavior of steelstructures, three-dimensional elasto-plastic FE analysis was conducted for steel portal framesunder impact loading. Here, two rigid portal frames of diﬀerent column size were numericallyanalyzed taking the impact velocity of the falling weight as variable. The results obtained fromthis study are as follows: 1) maximum displacement of the frame increases linearly with eachincrement of the input impact energy; and 2) the bending moment distribution of the wholeframe at the time when the maximum response displacement occurs is similar to that understatic loading.
Mitigating Impact Frailty of Concrete with Fiber Reinforcement
Authors: Banthia Nemy
Published: August 2011

Since 9/11, there has been an increased interest in developing a better understanding of the properties of concrete structures under impact and blast loading. Although concrete, as a material, demonstrates extreme brittleness under dynamically applied loads, fortunately, fiber reinforcement significantly enhances such resistance. Yet, the dynamic properties of both concrete and fiber reinforced concrete (FRC) remain poorly understood. This paper provides a historical perspective of our efforts aimed at understanding the impact resistance of fiber reinforced concrete, highlights some of the issues and challenges encountered and identifies the emerging areas where further research is necessary.
SMA in Mitigation of Extreme Loads in Civil Engineering: Study of their Application in a Realistic Steel Portico
Authors: Torra Vicenç , Isalgue Antonio , Auguet Carlota , Carreras Guillem , Casciati Fabio , Lovey Francisco C. , Terriault Patrick
Published: August 2011

Guaranteeing the use of Shape Memory Alloys (SMA) in mitigation of extreme load effects requires a deep study of the SMA behavior according to the specific requirements of the applications in damping. The damper was defined according the expected requirements (length of SMA and number of SMA wires). It is applied to two types of alloys (CuAlBe and NiTi) in the diagonals of a realistic steel portico (2.47 m x 4.10 m). The measurements establish that the used SMA reduces the oscillation amplitude to a less than a half.
Coupled Discrete Element/Finite Element Method for the Analysis of Large Reinforced Concrete Structures Submitted to an Impact
Authors: Daudeville Laurent , Haelewyn Jessica , Marin Philippe , Potapov Serguei
Published: August 2011

The efficiency of the discrete element method for studying the fracture of heterogeneous media has been demonstrated, but it is limited by the size of the computational model. A coupling between the discrete elements (DEM) and the finite elements (FEM) methods is proposed to handle the simulation of impacts on large structures. The structure is split into two subdomains in each of which the method is adapted to the behavior of the structure under impact. The DEM takes naturally into account the discontinuities and is used to model the media in the impact zone. The remaining structure is modeled by the FEM. We propose an adaptation of the coupling procedure to connect Discrete Element model to shell-type Finite Elements. Finally, the efficiency of this approach is shown on the simulation of a reinforced concrete slab impacted by a tubular impactor.
Numerical Simulation of Steel Bolted Beam-Column Connections Subjected to Dynamic Loading
Authors: Chang Liu , Hai Tan Kang , Ching Fung Tat , Tyas Andrew
Published: August 2011

This study presents the development of a finite element model with the capability to simulate and analyse the response of steel bolted beam-column connections subjected to rapid rate of applied loading. The effect of material strain-rate sensitivity was taken into account and a shear failure criterion was adopted to predict the failure of the connection. By comparing the simulation results with the experimental observed responses, it is found that the numerical techniques and the material model used here can predict the structural behaviour of connections reasonably well.
Experimental and Analytical Evaluation of Progressive Collapse Resistance of a Full-Scale Structure Following Sever Loss of Load Bearing Elements
Authors: Sasani Mehrdad , Kazemi-Moghaddam Ali
Published: August 2011

Experimental and analytical studies are carried out to evaluate the response of an actual reinforced concrete structure following severe initial damage, which was caused in part by simultaneous explosion (removal) of four adjacent columns. In addition, two beam segments in the vicinity of the removed columns were also exploded. The structure resisted progressive collapse following such severe initial damage. The progressive collapse resisting mechanisms primarily included the axial-flexural action of the second floor deep beams and Vierendeel action of the flat plate system in floors above. In the analytical studies, a nonlinear model of the structure is used, which accounts for axial-flexural interaction of beams and slabs. The analytical results show good agreement with experimental data.
Importance of Time-Dependent Material Behavior in Predicting Strength of Steel Columns Exposed to Fire
Authors: Morovat Mohammed Ali , Engelhardt Michael D. , Taleff Eric M. , Helwig Todd
Published: August 2011

One of the critical factors affecting the strength of steel columns at elevated temperatures is the influence of material creep. Under fire conditions, steel columns can exhibit creep buckling, a phenomenon in which the critical buckling load for a column depends not only on slenderness and temperature, but also on the duration of the applied load. This paper will propose a preliminary methodology to study the phenomenon of creep buckling in steel columns subjected to fire. Analytical solutions using the concept of time-dependent tangent modulus are developed to model time-dependent buckling behavior of steel columns at elevated temperatures. Results from computational creep buckling studies using ABAQUS® are also presented, and compared with analytical predictions. Both analytical and computational methods utilize material creep models for structural steel developed by Harmathy, and by Fields and Fields. The analytical and computational results clearly indicate that accurate knowledge of material creep is essential in studying creep buckling phenomenon at elevated temperatures, and that neglecting creep effects can lead to potentially unsafe predictions of the strength of steel columns subjected to fire.
Use of Plate Thermometers for Better Estimate of Fire Development
Authors: Byström Alexandra , Wickström Ulf , Veljkovic Milan
Published: August 2011

The concept of Adiabatic Surface Temperature (AST) opens possibilities to calculate heat transfer to a solid surface based on one temperature instead of two as is needed when heat transfer by both radiation and convection must be considered. The Adiabatic Surface Temperature is defined as the temperature of a surface which cannot absorb or lose heat to the environment, i.e. a perfect insulator. Accordingly, the AST is a weighted mean temperature of the radiation temperature and the gas temperature depending on the heat transfer coefficients. A determining factor for introducing the concept of AST is that it can be measured with a cheap and robust method called the plate thermometer (PT), even under harsh fire conditions. Alternative methods for measuring thermal exposure under similar conditions involve water cooled heat flux meters that are in most realistic situations difficult to use and very costly and impractical. This paper presents examples concerning how the concept of AST can be used in practice both in reaction-to-fire tests and in large scale scenarios where structures are exposed to high and inhomogeneous temperature conditions.
Performance of Protective Doors and Windows under Impact and Explosive Loads
Authors: Kruszka Leopold , Rekucki Ryszard
Published: August 2011

Experimental bullet-proof investigations for two types of steel protective doors under comparative perforation tests using various bullets shot from short and long typical fire-arms are presented. Protective windows are tested under soft impact of 30 kg mass and under aerial shock wave from explosion of an explosive blowing charge (aluminum cash desk windows) and a fuel-air mixture (steel protective windows of warship). The structural material of door leaves used is Polish standard building steel, while the window leaves - Polish architectural protective glass of P4A class in cash desk windows and duplex hardened glass in warship windows.
Structural Response and Reliability Analysis of RC Beam Subjected to Explosive Loading
Authors: Acito Maurizio , Stochino Flavio , Tattoni Sergio
Published: August 2011

The random nature of the explosion load, associated with the random nature of material properties, and geometric dimensional characteristics, implies the need to consider them into the reliability analysis in order to have a more correct estimation of the structural behavior. Therefore, when the randomness of these parameters in the analysis is considered, the response of the structure assumes probabilistic nature, and this makes it necessary to look into the reliability measure. This paper presents results from a parametric investigation of the reliability of reinforced concrete (RC) beam subjected to blast load. The probabilistic responses of the maximum displacement for a reinforced concrete flexural member under blast loadings are evaluated by means of nonlinear dynamic analysis with simplified equivalent single-degree-of-freedom (SDOF) system. Results of numerical simulations have shown the response of structures, in terms of maximum displacement in relation also to the blast load and the geometrical and mechanical characteristics of the beams. Monte Carlo simulation of dynamic response of the equivalent SDOF system is performed to estimate the reliability.
SDOF Models for RC and FRC Circular Plates under Blast Loads
Authors: Colombo Matteo , Martinelli Paolo
Published: August 2011

This work presents simpliﬁed models, in the form of single degree of freedom (SDOF)elasto-plastic systems, for the dynamic analysis of traditional reinforced concrete (RC) and ﬁbre-reinforced concrete (FRC) circular plates under blast loads. Two cases have been examined inthis study: simply supported and resting on Winkler-type soil plates. Both cases intend toprovide a simpliﬁed tool for predicting the response respectively for specimens subjected toblast pressure wave inside shock-tube facilities and for slabs on ground under blast loads. Thesecond case also represents the loading conditions inside a new shock tube facility speciﬁcallyintended for the investigation of underground tunnel lining subjected to blast loads.
Impact Response Analysis of Wire Ring Net System Using the Concept of Particle Method
Authors: Sonoda Yoshimi , Hata Yoshihiro , Fukunaga Kazuki
Published: August 2011

In Japan, there are many steep mountainous areas and we have local severe rain in the season, thus rock-fall accidents occur in mountain regions year after year. In order to protect an arterial road and the urban areas from the rock-fall accidents, various protective structures had been already constructed. However most of them are made of reinforced concrete and they require huge construction cost. Hence a new economical protective structure has been expected for a long time. From these needs, several high-energy absorption rock-fall nets have been developed. Some of them have specialized shock absorbing device or specialized column which has plastic rotation capacity. On the one hand, wire frame structure (called the wire ring net system) that is composed of interconnected many wire rings of about 30 cm in diameter are predominant in Europe. Because these structures can absorb large kinetic energy of a falling rock due to their deformation capacity, they are introduced from Europe as the highly-effective structures. The wire ring net system is composed of many parts (wire ring, wire rope, supporting post, etc), and it does not require large bases due to its light weight. However, there is no analysis method that can calculate their impact response (dynamic behaviour and energy absorbing capacity), and it has been only confirmed by the full-scale falling weight tests. Although, there are several cases that evaluate the performance by same tests in Japan, the test condition is limited by restriction of test station and its cost. Therefore, this study aims at simulating the impact response of wire ring net system by using the concept of particle method. The following conclusions are obtained from this study. 1) The proposed method can simulate the impact response of the wire ring net system. 2) Fracture of the wire ring net is predicted applying critical strain limit for the material.
Internal Explosions in Embedded Concrete Pipes
Authors: Bonalumi Pamela , Colombo Matteo , di Prisco Marco
Published: August 2011

Blast tests on a full-scale concrete pipe embedded in soft soil were carried out to evaluate the behavior of the soil-structure system under the internal detonation of high-energy solid explosives. Two different stages were considered: the former focused on the detonation of a low entity charge within the pipe to maintain the concrete in the elastic regime and the latter concerned with adopting larger quantities of explosive to produce cracking and failure of the structure. Cylindrical charges ranging from few grams to hundreds of grams of a high-energy solid explosive were investigated and different tests were performed for each quantity by inserting the explosive charge in a cardboard cylinder hanged up in the middle of the pipe central segment by means of three thin plastic wires. The following quantities were measured in different sections along the pipe: side-on and reflected pressure-time histories at the inner surface of the structure, pipe radial acceleration, peak particle acceleration of the surrounding soil by means of accelerometers placed at different distances and depths from the section where the explosion occurred. The experimental results obtained during the performed blast tests are thus analyzed to understand the soil-structure system behavior under such fast transient dynamic phenomena.
Soft Projectile Impacts on Thin Reinforced Concrete Slabs: Tests, Modelling and Simulations
Authors: Pontiroli Christophe , Rouquand Alain
Published: August 2011

Numerical simulations of reinforced concrete structures subjected to high velocity impacts and explosions remain a difficult task today. Since ten years and more now, the CEA-Gramat has maintained a continuous research effort with the help of different French universities in order to overcome encountered difficulties in modelling the behaviour of concrete structures under severe loading. These difficulties are related to numerical aspects (convergence difficulties of the non linear stress strain relation in 3D configuration, efficiency of the numerical procedure and robustness), but also due to the ability of the material model to simulate the accurately behaviour of a very complex and heterogeneous material like concrete. A new concrete model, named PRM model, has been developed at CEA-Gramat (Pontiroli, Rouquand & Mazars, [1], [2], [3]) to predict the concrete response under a large range of dynamic loadings.
Simplified Methods for Improving the Blast Resistance of Cold-Formed Steel Walls
Authors: Bewick Bryan , O'Laughlin Casey , Williamson Eric
Published: August 2011

In recent years, cold-formed steel stud walls have become an attractive alternative to wood stud walls. Relative to wood, cold-formed steel is highly ductile, sustainable, and unaffected by insects, mold or rot. Research has demonstrated that cold-formed steel stud walls can perform well when subjected to large blast threats, but such performance has depended upon specially designed fasteners that are expensive to manufacture and require experienced workers to install properly. Despite the potential performance of these types of wall systems when specialized fasteners are used, current U.S. Department of Defense design guidelines for conventionally constructed steel stud walls use acceptability criteria that are much more conservative than wood stud walls due to the lack of data available. Thus, the goal of the current research effort is to develop techniques for mitigating large blast threats acting against steel stud walls using conventional construction methods and materials. The research includes controlled laboratory tests that are intended to identify the various failure mechanisms that can occur for different combinations of wall system parameters. Variables considered in the testing program include stud and track section properties, stud-to-track connection details, stud orientation and wall layout, and sheathing system properties. Based on the results obtained from the testing program and supporting analyses, the most promising wall system designs will be identified, and design guidance will be developed. Final designs will be tested under actual blast loads to verify performance and to ensure that wall systems behave as desired.