Wan Zhen Wang

Fracture Mechanism of Joints of Steel Box Column-H Steel Beam and Performance Study of Joints Strengthened with Haunches

Fracture test was performed on conventional joint of steel box column-H steel beam. The test results indicate that the conventional joints brittle fracture at butt weld of beam flanges. The performance of joints of steel box column-H steel beam strengthened with haunches is numerically simulated based on an ellipsoidal fracture model considering of welding residual stress and welding defects. The simulated results show that, for the joints of box column-H beam strengthened with haunches, the plastic rotation of could reach 0.03rad and the bearing capacity increased by 20% compared with that of the conventional joint.

Fracture Mechanism and Ductility Construction of Joints of H-Style Beam-Square Tubular Column

Numerical simulation and fracture analysis were performed on conventional joint of H-style beam-square steel tubular column based on suggested elliptical yield model. The modified coefficient of elliptical fracture model was obtained by equivalently calculating the effects of residual stress and flaws. Using the elliptical fracture model with equivalently calculating the effects of residual stress and disfigurement for evaluation, the parameters of slot holes and horizontal haunch at beam flanges on failure mode of joints of H-style steel beam-square steel tubular column were studied by finite element method. The results indicate that the plastic rotation of joints of H-style beam-square steel tubular column with slot holes and horizontal haunch at beam flanges reach 0.03rad and meet with the requirement of the interim guidelines FEMA, and the loading capacity decrease within 15% compared with that of the conventional joint.

Buckling Analysis of Sway Steel Frames with Semi-Rigid Connections

The modified factor formulas, which are applicable to sway steel frames, are derived by considering joint relative rotational stiffness and adopting the modified stiffness factor. The finite element models of steel frames with semi-rigid and rigid connections are established using ANSYS program. Nonlinear finite element analysis of steel frames with two web and top-seat angles steel semi-rigid connections is conducted. Through bulking analysis of sway steel frames with semi-rigid connections, the effective length factor of sway steel frames is derived, which considers nonlinear rotation of two web and top-seat angles steel semi-rigid connections.

An Egg Shaped Failure Criterion for Lightweight Aggregate Concrete

Referring to an egg shaped yield function for geotechnical materials, a failure criterion for light-weight aggregate concrete is put forward, in which the tensile and compressive meridians are egg shaped curves and the failure envelopes in deviated plane is smooth elliptic curves. The suggested failure criteria could describe the failure characteristic of lightweight aggregate concrete at different stress state. The precision of the suggested egg shaped failure criteria is verified by comparing with experiment data of lightweight aggregate concrete.

Orthogonal Test of Characteristics of Complex Cememting Material of FGD Gypsum-Fly Ash

Orthogonal test method is used to study the effect of the mineral admixtures on the performance of FGD gypsum-fly ash complex cementing material. On the basic experiment, the effect of the traditional alkali and salt admixtures added to the complex cementitious system is discussed, the factors effecting on performance of the FGD gypsum were analyzed. Based on the experimental results, the best mix proportion was determined. Finally, the basic performance of complex cementitious material was tested. The experimental results show that the performance of FGD gypsum which is activated through adding the compound admixtures was similar with the ordinary interior wall materials. The strength and water resistance of FGD gypsum complex cementing material can be greatly enhanced by adding cement, quicklime and slag powder, and effect of cement is largest, and slag smallest. The performance of the gypsum complex cementing material also can be improved after incorporation of a few of chemical admixture on the basis of adding mineral activators.

Fracture Test and Analysis of Notched Bars Fabricated from Q235 Steel at Room Temperature

Tensile tests at room temperature were performed on 20 notched bars fabricated from constructional steel Q235 specified in Chinese National Standards. The effect of the notch radius, r, and that of the notch depth ratio, d/D, on the fracture model of the constructional steel is examined. The experimental results demonstrate that cracks initiate at the notched section. Specimens with a sharper notch radius (a smaller r) and a larger notch depth (a smaller d/D ratio) show poor ductility, but high fracture strength. The experimental data are further analyzed using an elliptical yield model together with an elliptical fracture model originally proposed by the first author. The stress field computed from the numerical procedure indicates that the crack initiation occurs at the center of the notched section which experiences the highest stress triaxiality ratio (óm/óseq). As the stresses at the notched section reach the limiting values determined from the elliptical fracture model, macroscopic fracture failure in the notched bar occurs.

Fracture Test on High Strength Steel Plates with Elliptical Hole

In order to study fracture mechanics of high strength steel with the moderate thickness, fracture tests were performed on 10 plates with elliptical hole fabricated from high strength steel Q345 with the thickness of 16mm. The effect of the notch sharpness (the ratio of the length of short axis to that of long axis of elliptic hole, b/a) and the notch depth (the ratio of the length of long axis of the elliptic hole to the width of plate, 2a/w) on fracture model of high strength steel was examined. Test results show that the first crack initiates at the notch edge. The fracture ductility is lower for the specimens with the sharper notch (a smaller ratio b/a) and the deeper notch (a larger ratio 2a/w), and the point of crack load lies in hardening phase of load-displacement curve. The fracture ductility is higher for the specimens with the obtuse notch (a larger ratio b/a), and the point of fracture load lies in necking phase of load-displacement curve. The ultimate strength of notched plates is independent of the notch sharpness (b/a) and the notch depth (2a/w).

Fracture Mode of E50 Solder Notched Bars at Low Temperature

Fracture tests were performed on 20 notched bars fabricated from E50 solder at low temperature (-47°C~-43°C). The effect of notch radius, r, and notch depth, d, on fracture mode of E50 solder was studied. The experimental results demonstrate that cracks initiate at the center of notch section and the notched bars fracture at the notch section at low temperature. The fracture mode is cleavage fracture and the fracture sections are coarse. Specimens with a sharper notch radius (a smaller r) and a larger notch depth (a smaller d) show poor ductility, but high fracture strength. The stress-strain curve of E50 solder tested on standard specimen at low temperature (-47°C~-43°C) exhibits the character of yielding, hardening and necking. The ratio of ultimate strength to yield strength, σu/σy, and the ductility, δ5, at low temperature meet with the requirement in plastic design for structural steel.

Numerical Analysis of Pre-Stressed Steel Trusses Subjected to Fire Load

The computational model of numerical analysis of the planar pre-stressed steel trusses subjected to fire load is established according with main consideration to the response mechanism of the structure in fire. For the convenience of application, the EC3 constitutive model of the steel materials in fire is simplified with series expansion, and the suggested formula for each stage are unified. The fire behavior of the planar pre-stressed tubular steel trusses in which two cables are set is analyzed with the model presented here and the effect law of different factors on the bearing capacity of the structures in fire are discussed. It is concluded that fire response of the pre-stressed steel trusses is affected obviously by the different model of material under the same fire conditions, and critical temperature of the structure in fire increases with strength grade of steel material, which means that choice of the proper material model used for analysis of behavior of the steel structure under fire is very important and need to be studied further.

Research on Fire Resistance Performance of Pre-Stressed Suspended Steel Reticulated Shell

Pre-stressed steel structures with large space are widely used in stadium, exhibition hall, theater and other buildings today. In order to study the fire-resistance behavior of suspended steel lattice shell of a stadium, the method of performance-based fire resistance design is used. First of all, the stadium physical model is established and the software FDS is used to determine the heating curves of the measuring points of the large space structure for two fire scenes. Compared with international standards heating curve, the heating curves of the large space structure obtained here has characteristic of local high-temperature. The finite element software MSC.MARC is further used to simulate the fire behavior of the pre-stressed steel structure with large space, in which the fire scene with 10MW design power of fire source and 30 minutes duration of fire are considered and two loading ways that overall non-uniform temperature field loading and the local high temperature components loading are accepted. The results show that the pre-stressed steel structure with large space has good fire resistance behavior, and the overall failure will not take place for the fire scene suggested here during 30 minutes duration of fire.