Fracture and general yield for carbon steel pipes with local wall thinning

Monotonic bending tests without internal pressure are conducted on 4 and 3.5 in. diameter full-scale carbon steel pipe specimens with local wall thinning in order to evaluate the structural integrity of power plant piping. The local wall thinning is simulated as erosion/corrosion metal loss. The eroded area of the wall thinning is subjected to tensile or compressive stress by applied bending moment. The maximum moments obtained from the tests are compared with the plastic collapse moments based on the net-section stress approach. The net-section stress approach based on flow stress σ_f gives a conservative estimation, sometimes overly conservative. Although the net-section approach based on ultimate tensile strength σ_u gives a slightly non-conservative estimation for some cases, the calculated values are close to the experimental data. Using the net-section stress approach based on σ_u, the eroded depth and the angle at which a pipe undergoes general yielding were obtained.     

Fracture behavior of carbon steel pipe with local wall thinning subjected to bending load

To evaluate the structural integrity of power plant piping, monotonic bending tests are conducted on 4- and 3.5-in. diameter full-scale carbon steel pipe specimens with local wall thinning. The local wall thinning is simulated as erosion/corrosion metal loss. The eroded area of the wall thinning is subjected to tensile or compressive stress by applied bending moment. The deformations or fracture behaviors at maximum moments are found to be classified into three types. When the eroded area is subjected to tensile stress, ovalization or crack initiation/growth occurs at the maximum moment. When an eroded area is subjected to compressive stress, ovalization or local buckling occurs. The occurrence of ovalization, crack initiation/growth, or local buckling depends on the initial size of local wall thinning. From the relationships among ovalization, crack growth and local buckling, allowable sizes for local wall thinning are proposed.     

Correlation of in-plane bending test and FEA results for thin-walled elbows

The objective of this study is to validate a finite element analysis (FEA) simulation methodology to predict the global behavior of thin-walled elbows subjected to in-plane bending. Two in-plane closing mode bending tests and one in-plane opening mode bending test were conducted on 2″ schedule 10 elbows, and a nonlinear FEA procedure was used to simulate the tests. A detailed FEA study was carried out to determine the relative importance of weld size and location, measured wall thicknesses, and original cross-section dimensions on the reconciliation results. When the weld bead was included in the analysis, the reconciliation results for load–displacement behavior and some of the strain measurements were excellent. For those cases in which the strain measurements reconciliations were not so good, a possible explanation is provided.     

Low cycle fatigue behaviors of elbow pipe with local wall thinning

Low cycle fatigue tests were conducted using 100A elbow specimens made of STPT410 carbon steel with local wall thinning. Local wall thinning by erosion/corrosion was simulated by machined pipe wall thinning. The local wall thinning areas were located at three different areas, called extrados, crown and intrados. The elbow specimens were subjected to cyclic in-plane bending under displacement control without internal pressure. The effects of eroded conditions, such as eroded ratio, eroded angle and position, on the low cycle fatigue behavior and fatigue life were discussed by using experimental results and finite element analyses. Also the location of crack initiation and the crack growth direction could be predicted by three dimensional elasto-plastic finite element analyses. In addition, the safety margin of eroded elbows against seismic loading was discussed by comparing the fictitious stress of elbows with the allowable stress limit demanded by the design code.     

Experimental investigation of the failure behavior of notched wall-thinned pipes

The present study performed full-scale pipe tests using 100A Schedule 80 pipe specimens with simulated notched and circular wall thinning to investigate the failure behavior of notched wall-thinned pipes. The tests were conducted under both monotonic and cyclic bending moments at a constant internal pressure of 10 MPa at room temperature. The failure pattern, load carrying capacity, deformation ability, and fatigue strength of the notched wall-thinned pipes were evaluated by comparing results to those of circular wall-thinned pipes. The investigation showed that the effect of the type of thinning on the failure behavior was more sensitive under cyclic loading conditions than under monotonic loading conditions. The load carrying capacity of pipes with notched wall thinning was approximately the same or slightly less than that of pipes with circular wall thinning when the thinning area was subjected to tensile stress. However, when the thinning area was subjected to compressive stress, the load carrying capacity of pipes with notched wall thinning was greater than that of pipes containing circular wall thinning. The deformation ability and fatigue strength increased proportionally with the axial length of the thinning defect, and thus these properties were significantly reduced in notched wall-thinned pipes.     

Interpretation of results of meppen slab tests—Comparison with parametric investigations

Within the experiments performed at Meppen test site, reinforced concrete slabs are tested extremely stressed under the impact of highly deformable projectiles. A main objective of these tests consists in an approvement of theoretically founded methods, which are applied to the treatment of aircraft impact load. Comparative computational investigations are carried out, using a dynamic, physically nonlinear method. Most of the parameter variations examined at Meppen concern with the structural design, with regard to the relations between bending and shear bearing capacity.By varying the bending and the shear reinforcement, the portions between bending and transverse shear deformations are distinctly influenced, and thus the amount of the total displacements as well. This corresponds with different degrees of damage and crack formation in the experiments.In the range of ultimate slab resistance, the results generally show a high sensitivity with respect to the load conditions. These are strongly influenced by the impact velocity as well as by the deformation behaviour of the projectiles.In the experiments, the structural behaviour of the test slabs demonstrates a greater sensitivity to altering thicknesses than to variations of the equivalent amount of reinforcement.     

Study on reactor building structure using ultrahigh strength materials

This study was promoted to realize the optimal nuclear reactor building structure of the future. As the first step, the study regarding ultrahigh strength reinforced-concrete (RC) shear walls was positively verified. The tests conducted were relevant to ultrahigh strength concrete material tests, pure shear tests of RC flat panels, bending shear tests and simulation analyses of RC shear walls, S-joint tests and mixed-structure tests. From the results of this study, it was verified that mixed structures using ultrahigh strength material can be realized.     

Post-test analysis of a 1:10-scale top slab model of ABWR/RCCV subjected to internal pressure

Construction of the first Advanced Boiling Water Reactor (ABWR) in Japan employing a reinforced concrete containment vessel (RCCV) was started in 1991. As RCCV itself is the first structure of its kind in Japan, thorough verification tests have been performed. This paper presents the results of simulation analysis of the Top Slab partial model of the RCCV subjected to internal pressure beyond design load. The Top Slab portion is complicated, being composed of a flat Top Slab, cylindrical wall and fuel pool girders, that its simulation analysis requires the evaluation of nonlinear structural behavior of reinforced concrete members due to membrane, bending and shear forces. This paper reports that Finite Element analysis with 3-D solid elements has given a good quantitative agreement between experimental and analysis results with respect to deformation, failure load and each nonlinear behavior.     

Study on steel plate reinforced concrete panels subjected to cyclic in-plane shear

This paper describes the derivation of the equation for evaluating the strength of steel plate reinforced concrete structure (SC) and the experimental results of SC panels subjected to in-plane shear.Two experimental research programs were carried out. One was the experimental study in which the influence of the axial force and the partitioning web were investigated, another was that in which the influence of the opening was investigated.In the former program, nine specimens were loaded in cyclic in-plane shear. The test parameters were the thickness of the surface steel plate, the effects of the partitioning web and the axial force. The experimental results were compared with the calculated results, and good agreement between the calculated results and the experimental results was shown.In the later programs, six specimens having an opening were loaded in cyclic in-plane shear, and were compared with the results of the specimen without opening. FEM analysis was used to supplement experimental data. Finally, we proposed the equation to calculate the reduction ratio from the opening for design.     

Seismic behaviour and design of steel coupling beams in a hybrid coupled shear wall systems

The hybrid coupled shear wall system is more efficient and economical than individual structural walls because the steel coupling beams connected shear walls significantly increase the strength, stiffness and energy dissipation capacity of the system. In this study, experimental studies on the steel coupling beam were carried out. The main test variables were the ratios of the coupling beam strength to the connection strength. In addition, the seismic design methods are presented for steel coupling beam–wall connection and shear critical and flexure critical steel coupling beams in hybrid coupled shear wall system consisting of steel coupling beams and reinforced concrete shear walls. Finally, this paper provides background for design guidelines in hybrid coupled shear walls that include steel coupling beam–wall connections and steel coupling beams.     

CARR铱源试验靶件设计和试验验证

为配合中国先进研究堆(CARR)铱源辐照生产项目,设计制造了铱源试验靶件,对试验靶件的设计参数、结构尺寸进行了介绍。在堆外使用专门的传热装置模拟铱源靶件的外部和内部传热工况,测量了用于模拟辐照罐壁面温度和样品温度的传热装置的壁面温度和内部温度,结果验证了热工分析方法是合适的。入堆试验靶件由含有铱片样品的辐照罐和等量发热的模拟罐组成。堆内试验获得的数据综合验证了试验靶件物理热工的分析结果,这个结果可对CARR铱源辐照生产安全评审提供依据且偏于安全。     

Fracture and deformation behaviors of tee pipe with local wall thinning

Monotonic four-point bending tests were conducted using tee pipe specimens having local wall thinning. The effects of local wall thinning on the fracture behaviors of tee pipes were investigated. Local wall thinning was machined on the inside of pipes in order to simulate metal loss due to erosion corrosion. The configurations of the eroded area were l = 100 mm in eroded axial length, d/t = 0.5 and 0.8 in eroded ratio, and 2θ = 90° in eroded angle. The area undergoing local wall thinning was subjected to either tensile or compressive stress. It was found that the type of fracture could be classified into ovalization, local buckling, and crack initiation, depending on pipe shape, eroded ratio, and stress at the eroded area. Fracture behaviors of the tee pipes were compared with those of straight pipes. Three-dimensional elasto-plastic analyses were also carried out using the finite element method, which was able to accurately simulate fracture behaviors.     

Failure behavior of carbon steel pipe with local wall thinning near orifice

Monotonic four-point bending tests were conducted using pipe specimens having an orifice undergoing local wall thinning. The effects of local wall thinning on the fracture behaviors of pipe were investigated. Local wall thinning was machined on the inside of pipes in order to simulate erosion corrosion metal loss. The configurations of the eroded area were l = 100 mm in axial length, d/t = 0.5 and 0.8 in thickness ratio, and 2θ = 180° in angle. The area undergoing local wall thinning was subjected to either tensile or compressive stress. Failure type could be classified into ovalization, local buckling, and crack initiation, depending on thickness ratio, and stress at the eroded area. Three-dimensional elasto-plastic analyses were also carried out using the finite element method, which is able to accurately simulate fracture behaviors. Failure analysis map was constructed for pipes with or without orifice based on the results of finite element analyses in order to investigate the effect of orifice on the failure behaviors.     

Tension tests of concrete containment wall elements

Tension tests of concrete containment wall elements were conducted as part of a three-phase research program sponsored by the Electric Power Research Institute (EPRI). The objective of the EPRI experimental/analytical program is twofold. The first objective is to provide the utility industry with a test-verified analytical method for making realistic estimates of actual capacities of reinforced and prestressed concrete containments under internal over-pressurization from postulated degraded core accidents. The second objective is to determine qualitative and quantitative leak rate characteristics of typical containment cross-sections with and without penetrations. This paper covers the experimental portion the the EPRI program.The testing program for Phase 1 included eight large-scale specimens representing elements from the wall of a containment. Each specimen was 60-in (1525-mm) square, 24-in (610-mm) thick, and had full-size reinforcing bars. Six specimens were representative of prototypical reinforced concrete containment designs. The remaining two specimens represented prototypical prestressed containment designs.Various reinforcement configurations and loading arrangements resulted in data that permit comparisons of the effects of controlled variables on cracking and subsequent concrete/reinforcement/liner interaction in containment elements.Subtle differences, due to variations in reinforcement patterns and load applications among the eight specimens, are being used to benchmark the codes being developed in the analytical portion of the EPRI program.Phases 2 and 3 of the test program will examine leak rate characteristics and failure mechanisms at penetrations and structural discontinuities.     

Testing of large-scale concrete containment structural elements

The tests described in this paper are part of an Electric Power Research Institute (EPRI) program (Research Project 2172-2) to provide a test-verified analytical method of estimating capacities of concrete reactor containment buildings under internal overpressurization from postulated degraded core accidents.Experimental study in Phase 2 of the investigation, on which this paper is based, includes tests of five large-scale specimens with steel liner plates representing structural elements of prestressed concrete containment buildings. Four square wall element specimens and one specimen representing the wall/basemat junction region were tested.This experimental work indicates that under internal overpressurization or other accident conditions, highly localized strains in the steel liner plate can result in liner tearing and subsequent containment leakage. These results support the theory of leak before break where liner tearing occurs in a controlled manner and leakage and depressurization occur rather than global failure.     

Results of large-scale test of discontinuity region in a prestressed concrete containment

The test described in this paper is part of an Electric Power Research Institute (EPRI) program (Research Program RP2172-2) to provide a test-verified analytical method of estimating capacities of concrete reactor containment buildings under internal overpressurization from postulated degraded core accidents.Phase 2 of the EPRI program, on which this paper is based, includes tests of five large-scale specimens with steel liner plates. The specimens represent structural elements of prestressed concrete containment buildings. Four full-scale square wall element specimens and one specimen representing the wall/basemat junction region were tested. This paper describes results of the wall/basemat junction region test.Results of this experimental work indicate that highly localized strains in the steel liner plate caused by internal overpressurization or other accident conditions can result in liner tearing and subsequent containment leakage. It appears that this liner tearing occurs in a controller manner. Extrapolating from these test results, leakage and depressurization is more likely to occur than global failure.     

The bearing strength of steel coupling beam-reinforced concrete shear wall connections

Increasingly, engineers are designing hybrid and mixed building systems of structural steel and reinforced concrete to produce more efficient structures than can be realized using either material alone. In particular, hybrid coupled shear wall of them are known to be efficient lateral load resisting system. However, due to lack of information, current design equations to compute the bearing strength of steel coupling beam–wall connections in a hybrid coupled shear walls are tacit about cases in which the beams have connection details to the walls that include stud bolts and horizontal ties in hybrid coupled shear walls. There were carried out experimental and analytical studies on steel coupling beam–wall connections in a hybrid wall system. Experimental study was carried out to verify the bearing strength of steel coupling beam–wall connections. The test variables included the reinforcement details that confer a ductile behavior on the steel coupling beam–wall connection, i.e., the stud bolts and the horizontal ties in the steel coupling beam–wall connections. The equations proposed in this study to predict strength for steel coupling beam-reinforced concrete shear wall connections were in good agreement with both our test results and other test data from the literature.     

Investigation of the ductile fracture properties of type 304 stainless steel plate, welds, and 4-inch pipe

J-integral fracture toughness tests were performed on welded 304 stainless steel 2-inch plate and 4-inch diameter pipe. The 2-inch plate was welded using a hot-wire automatic gas tungsten arc process. This weldment was machined into 1T and 2T compact specimens for single specimen unloading compliance J-integral tests. The specimens were cut to measure the fracure toughness of the base metal, weld metal and the heat affected zone (HAZ). The tests were performed at 550°F, 300°F and room temperature. The results of the J-integral tests indicate that the J_Ic of the base plate ranged from 4400 to 6100 in lbs/in² at 550°F. The J_Ic values for the tests performed at 300°F and room temperature were beyond the measurement capacity of the specimens and appear to indicate that J_Ic was greater than 8000 in lb/in². The J-integral tests performed on the weld metal specimens indicate that the J_Ic values ranged from 930 to 2150 in lbs/in² at 550°F. The J_Ic values of the weld metal specimens tested at 300°F and room temperature were 2300 and 3000 in lbs/in² respectively. One HAZ specimen was tested at 550°F and found to have a J_Ic value of 2980 in lbs/in² which indicates that the HAZ is an average of the base metal and weld metal thoughness. These test results indicate that there is a significant reduction in the initiation fracture toughness as a result of welding.The second phase of this task dealt with the fracture toughness testing of 4-inch diameter 304 stainless steel pipes containing a gas tungsten arc weld. The pipes were tested at 550°F in four point bending. Three tests were performed, two with a through wall flaw growing circumferentially and the third pipe had a part through radial flaw in combination with the circumferential flaw. These tests were performed using unloading compliance and d.c. potential drop crack length estimate methods. The results of these test indicate that the presence of a complex crack (radial and circumferential) reduces in the initiation toughness and the tearing modulus of the pipe material compared to a pipe with only a circumferentially growing crack.     

Simulation of strong motion earthquake effects on structures using explosive blasts

This paper presents the results of three separate test programs which were conducted to determine the feasibility of simulating strong motion earthquake effects using dynamite blasting techniques. The three programs measured blast induced structural responses at: (1) the UCLA Field Station; (2) the Enrico Fermi Nuclear Power Plant, Monroe, Michigan; and (3) the experimental gas-cooled reactor facility (EGCR), Oak Ridge National Laboratory. The evaluation of the tests indicates that the simulation of strong earthquake excitations using subsurface blasting techniques is a valuable testing tool. Each of the three discussed tests indicate that reliable estimates of natural frequencies and mode shapes of vibration can be obtained directly.     

Research on modeling shear transfer in reinforced concrete nuclear structures

This paper provides an overview of research in modeling the mechanisms of shear transfer in reinforced concrete nuclear structures. Bases for the development of analytical models are discussed. Preliminary analysis results are presented for the wall specimens to study the behavior of a containment wall portion under biaxial tension and tangential shear loading. Further research needs and interests are suggested for improved analysis capabilities and design.