Papers by Author: Xin Tang Wang

Abstract: The numerical model of analysis of fire performance of a spatial pre-stressed steel structure with large span was established based on the software Marc. The thermal response and structural response of the pre-stressed steel structure was computed for some nodes of the structure in fire. The different fire scenes were considered for analysis of response temperature, displacements and stresses of the nodes of the pre-stressed steel structure.It is concluded that the temperature rise of the nodes of the structure is far behind that of air near the nodes, however they are quite close as the fire lasted for 3600s and almost the same after 7200s.The results show that the displacement of the node right above the inner cable is the maximum and the node above the outer cable has the smallest value of displacement and the maximum value is about two and half times as large as the minimum.The results show that the reason why the cables are out of work is that the equilibrium between the cables and the rods of the structure is lost, but not that the stress relaxation caused by thermal expansion make the cables out of work.

Abstract: The post-fire axial compressive behavior of a set of self-stress lightweight aggregate concrete filled steel tubes (noted as SSLC-ST) after exposure to fire was studied. Effect of the fire temperatures of the specimens and some parameters on the axial compressive behavior of the specimens was especially discussed. The results show that the initial circumferential strain of surface of the steel tubes is much larger than the longitudinal strain of the steel tubes, and the specimens of SSLC-ST have higher post-fire axial compression bearing capacity and better plastic deformation. It was concluded that the local buckling and overall failure of the specimens take place in succession while the specimens are axially loaded, and there are a lot of slip lines with angle of 45^o on surface of the steel tubes.

Abstract: The post-fire axial compressive behavior of a set of steel fiber reinforced ceramsite concrete filled steel tubular short columns (noted as SFCC-SSC) was experimentally studied. Effect of the maximum value of fire response temperatures of the specimens and some parameters on the axial compression performance of the specimens was especially discussed. The results show that the surface of the steel tubes after fire presented dark red for 700°Cof furnace temperature and orange red for 900°C, and there was no obvious descending segment in post-fire load-displacement curves of the most specimens subjected to fire load. It was concluded that the axial bearing capacity of the specimens aftersuffering the furnace temperature of 900°C is much less than that of the specimens not subjected to fire load, and the volume of steel fiber of 0.5% of has the greatest effect on post-fire bearing capacity of specimens of SFCC-SSC.

Abstract: The post-fire behavior of a set of steel fiber reinforced lightweight aggregate concrete filled steel tubular short columns (noted as SFLC-SSC) after exposure to fire was experimentally studied. Effect of the maximum value of fire response temperatures of the tubes and their geometric parameters on the strength and the other mechanical property of the specimens were especially discussed. The experimental results show that the specimens of SFLC-SSC have higher post-fire bearing capacity and better plastic deformation. It was concluded that the maximum response temperature of the specimens has great effect on the post-fire bearing capacity of steel fiber reinforced concrete-filled steel tubes subjected to fire load, and incorporation of 0.5% of volume of steel fiber is best for enhancing the axial compressive bearing capacity of the specimens of SFLC-SSC after exposure to fire.

Abstract: The post-fire behavior of a set of self-stress lightweight aggregate concrete filled steel tubular short columns (noted as SSLC-SSC) after exposure to fire was experimentally studied. Effect of the maximum value of fire response temperatures of the tubes and their geometric parameters on the strength and the other mechanical property of the specimens were especially discussed. The experimental results show that the specimens of SSLC-SSC have higher post-fire bearing capacity and better plastic deformation, there was no obvious descent segment in post-fire load-displacement curves of the most specimens subjected to fire load. It was concluded that the maximum response temperature of specimens has great effect on the post-fire bearing capacity of self-stress concrete-filled steel tubes subjected to fire load, and the value of self-stress corresponding to 10% of dosage of expansive agent has the greatest effect on post-fire bearing capacity of specimens of SSLC-SSC.

Abstract: In this paper, one certain space under bridge which was used as a storehouse has been simulated numerically. The flow was considered turbulent and buoyant. A simple geometry was adopted, consisting of a room with a door that plays the role of inlet and another of outlet for the air. Four bundles of wood burners which considered as a volumetric heat source were placed evenly in the space. The problem was simulated by using the RNG K-ε turbulence model, modified to account for buoyancy effects. Several useful results were obtained.

Abstract: In order to study the post-fire bearing capacity and performance of the profiled sheet-light aggregate concrete composite floor after exposure to fire load, experimental study of post-fire bearing capacity of a profiled sheet-ceramsite concrete composite floor subjected to dead load, which has no shearing nails, is carried out here. Based on the experimental results, the post-fire bearing capacity of the composite floor after exposure to fire is analyzed. It is shown that the failure form of the profiled sheet-lightweight concrete composite floor after exposure to fire has obvious change compared with the floor not subjected to fire load, and the ultimate value of the equivalent distributed load applied to the top surface of the floor is up to 35 kN/m2, which may be used as basis of strengthening and repairing of the profiled sheet-lightweight aggregate concrete composite floor after exposure to fire.

Abstract: In order to study fracture mechanics of high strength steel with the moderate thickness, fracture tests were performed on 10 elliptical notched plates with the thickness of 16mm fabricated from high strength steel Q345. The effect of notch sharpness (the ratio of the length of short axis to that of long axis of elliptic notch, b/a) and notch depth (the ratio of the length of long axis of elliptic notch to the width of plate, a/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 low for the specimens with the sharper notch (a smaller ratio b/a), and the point of crack load lies in hardening phase of load-displacement curve. The fracture ductility is high for the specimens with the obtuse notch (a bigger ratio b/a), and the point of fracture load lies in necking phase of load-displacement curve. There is no qualitative relationship of fracture ductility and the notch depth (a/w). The ultimate strength of notched plates is independent of the notch sharpness (b/a) and notch depth (a/w).

Abstract: Fracture tests at low temperature (-47°C~-43°C) of 20 notched bars fabricated from E43 solder were conducted. The effect of notch radius, r, and notch depth, d/D, on fracture mode of E43 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/D ratio) show poor ductility. The stress-strain curve of E43 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 to the requirement in plastic design for structural steel.

Abstract: 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.