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New Development of High Strength Bolt Connections in Steel Structures
Zhaoxin Hou, Chao Gong, Yanxia Zhang, Zihao Liang, Weiqiao Liang, Wujun Fang
2021, 36(1): 1-12.   doi: 10.13206/j.gjgS20081901
Abstract(6) PDF (1607KB)(0)
As an effective structural connection between steel components, high strength bolt connection has been widely used in the construction filed nowadays. With the development of high strength bolt connection technology, new objects have shown up including new types of bolt, new technology, new equipment and so on. Investigation and conclusion of these new technologies have been conducted, which can provide the technical reference to the revision of the related specificitions as well as providing more choices for design and construction. The new types of high strength bolt consist of 12.9 and upper grade high strength bolt, blind bolt and ring groove rivet. Nowadays, there are research work and engineering practices of these new bolts in China, but engineering applications develop poor due to the absence of related specificitions. Investigation of new high strength bolt technology is mainly about bolt pretension indicator and bolt corrosion protection. Referring to their characteristics, comparison of these two technologies have been conducted among the research work worldwide. The new pretension indicator can eliminate the human error caused by using the traditional one, and therefore it can improve the accuracy of constructing bolt pretension. High strength bolt corrosion protection can effectively retard bolt corrosion, and therefore reduce the maintenance.
There are differences between domestic and foreign specificitions and comparison among these specificitions can provide references to the revision of current ones. Comparisons of calculation of bolt prying force and bolt pretension force as well as bearing capacity of friction-type and bearing-type high strength bolt connection among different specificitions have been conducted and show that: 1) Calculation results of bolt frying force from Chinese specificitions are more conservative. 2) The required bolt-pretension force in Chinese code is 15% smaller than that of American code and 10% smaller than that of European code. 3) The shear resistance formulas among different specificitions are consistent but the definition of contact surface and mean slip coefficient are different. 4) Bearing strength of bearing-type high strength bolt connection calculated from American code is the highest one and the higher one is from European code while the poorest one is from Chinese code. For tension strength and shear resistance, European code provides the highest values and European code shows the higher values while Chinese code provides with the poorest values. In general, Chinese code is conservative than foreign codes.
Performance Analysis of High-Efficient Prefabricated Steel Frame with Slit Steel Plate Shear Wall
Yanxia Zhang, Ailin Zhang, Zhaoxin Hou, Zhanyang Pang
2021, 36(1): 13-33.   doi: 10.13206/j.gjgSE20061101
Abstract(2) PDF (27347KB)(0)
In recent years, earthquake disasters have occurred frequently. Traditional steel structure buildings have large residual deformations after earthquakes and are difficult to repair. However, self-centering structures have achieved the anti-seismic goal of minimal damage in the earthquake and continued to use without repairing or minor repairing after the earthquake, which has been widely concerned by scholars at home and abroad. A new type of high-efficiency assembly self-centering steel frame structure system based on prestressing technology and bolt connection has been proposed in recent years, and the goal of high-efficiency assembly without high-altitude tensioning and short construction period is achieved under the premise of similar functions to the traditional self-centering steel structure system. On this basis, an efficient assembly steel frame with slotted steel plate shear wall structure was proposed and the pseudo-static test study of the structure was completed. The structure is mainly composed of two parts, a high-efficiency assembly steel frame and a slotted steel plate shear wall respectively, which are connected by high-strength bolts to achieve efficient assembly. The high-efficiency assembly steel frame is composed of steel columns and prestressed steel beams, which are connected by steel strands and high-strength bolts.
The ABAQUS finite element software was used to numerically simulate the structure test of the high-efficiency assembly steel frame with slotted steel plate shear wall. The main components such as steel columns, prestressed steel beams and steel plate shear walls in the high-efficiency assembly steel frame structure were all adopted C3D8R eight-node hexahedral linear elements, and the prestressed steel strands adopted T3D3 three-dimensional three-node truss elements. The effects of geometric nonlinearity and material nonlinearity were considered when calculating the model, and the numerical simulation adopts the same displacement loading system as the experiment. The test and numerical simulation of the structure ended at elastoplastic story drift limit 1/50.
The numerical simulation and test results were compared and analyzed to verify the reliability of the finite element analysis method. At the same time, to further study the seismic performance of the high-efficiency assembly steel frame with slotted steel plate shear wall and the effect of the slotted steel plate shear wall, the performance of the high-efficiency assembly steel frames with and without slotted steel plate shear wall, such as hysteresis curves, energy consumption performance, stiffness, self-centering capacity and equivalent plastic strain were compared and analyzed.
The results show that the hysteresis curve and frame gap opening width obtained by the numerical simulation are in good agreement with the test, and the effect of the opening and closure mechanism of the node can be simulated well. Efficiently assembled steel frame with slotted steel plate shear wall has a good opening closing mechanism and self-centering capability, high initial rigidity, good energy consumption capacity, and high lateral bearing capacity. Efficiently assembled steel frame with slotted steel plate shear wall structure has small residual gap opening, and the maximum force during the test is much smaller than the yield force of the steel strand. The high-efficiency assembly steel frame basically maintains elastic state except for the slight plasticity at the column feet, which provides a good foundation for the structure to withstand greater earthquake action. By comparing the numerical simulation results of the high-efficiency assembly steel frames with and without slotted steel plate shear wall, it can be seen that the slotted steel plate shear wall can effectively improve the rigidity of the structure and energy consumption capacity. The energy consumption of the slotted steel plate shear wall buckling can provide good protection of the main structure of the frame, so that the function of the main structure can be quickly restored by replacing the slotted steel plate shear wall after an earthquake.
Experimental Study of Box-Shaped Steel Column Bolted Connection
Yanxia Zhang, Zhaoxin Hou, Ailin Zhang, Mengyao Cheng
2021, 36(1): 34-49.   doi: 10.13206/j.gjgSE20061102
Abstract(1) PDF (24103KB)(0)
Since the 2013 National Construction Conference, state and local governments have issued a serious of documents to promote the development of prefabricated buildings. It conforms to the national policies and is also the trend of construction industry to actively develop and adopt prefabricated structures, especially prefabricated steel structure and to realize standardized design, factory production, and assembly construction. Box-shaped columns are widely used in steel structure buildings because of their equal bending stiffness in the two main axis directions. At present, box-shaped columns basically use fully-penetrated welded connection technology, which has many problems such as low construction efficiency, high labor costs, environmental pollution, severe damage upon earthquakes, and poor durability of on-site welding.
Based on the above key problems to be solved, a box-shaped steel column bolted connection was proposed. In this connection, the upper and lower installation units of the box-shaped steel column are connected by flange plates with high-strength bolts. In order to enhance the performance and improve mechanical properties of the core area of the connection, a core tube is set at the key position of the upper and lower units. In order to ensure the good co-working performance of the core tube and column, it is required that the gap between the core tube and the column wall does not exceed 2 mm. When the machining accuracy is not satisfied, there are two measures to improve it. Compensation plate can be set between the core tube and the column wall, or blind bolts can be installed to reduce the gap between the core tube and the column wall to ensure the co-working performance. Two kinds of the bolted connections with blind bolts and compensation plates were designed and tested under low-cycle reciprocating loads to study the mechanical performance of the bolted connections, and to make contrast with that of the fully-penetrated welded connection to study the rigid connecting behavior of the bolted connection.
The test results indicate that the setting of the core tube can provide certain flexural and shear resistance. When the story drift is 0.005 rad (1/200), the core tube contacts the column wall and work together to make the box-shaped steel column bolted connection more excellent. As the story drift is no more than 0.04 rad(1/25), the hysteresis performance and stiffness degradation trend of the both box-shaped steel bolted column connections are close to each other. When the story drift reaches 0.05 rad(1/20), the hysteresis performance of the box-shaped steel column bolted connection with blind bolts is better than that of the box-shaped steel column bolted connection with compensation plates. In the whole loading process, both of the box-shaped steel column bolted connections have excellent ductility, and the connection with blind bolts performs better and can significantly reduce bolt tension. The box-shaped steel column bolted connection with compensation plates and the box-shaped steel column bolted connection with blind bolts are damaged at 0.05 rad and 0.06 rad, respectively and the latter one can withstand greater deformation. The box-shaped steel column bolted connections can be selected flexibly according to the actual needs as conducting engineering design. The box-shaped steel bolted column connections possess similarly static performance with that of the fully-penetrated welded connection and can be designed as rigid connection when applied in actual engineering. The box-shaped steel bolted column connection technology realizes fully-bolted rigid connection and efficient assembly of steel structure system, which has great strategic significance to promote the upgrading of construction industrialization, improve construction efficiency, reduce environmental pollution and promote ecological civilization.
Experimental Investigation on the Effects of Temperature on the Bearing Capacity of High Strength Bolt Connections
Zhaoxin Hou, Chao Gong, Zihao Liang, Gang Wang, Zhidong Yao
2021, 36(1): 50-59.   doi: 10.13206/j.gjgS20081803
Abstract(4) PDF (7827KB)(0)
High strength bolt connection is one of major method used in steel structure construction on site. Taking the form of slotted hole in bolt connection, it will be more convenient and efficient in construction since this form shows better tolerance in installation deviation. At present, there is less research focused on high strength slotted bolt connection while it is blank in the research field of high strength slotted bolt connection under high temperature. 14 tests were conducted according to different experiment schemes including standard or slotted hole high strength bolt connection and different test temperatures of room temperature, 130 ℃ and 200 ℃. Among these 14 tests, slippage in bolt connection was studied and variables including temperature, bolt hole style, bolt diameter and so on were considered. The high temperature strain gauge was adopted to observe the change of bolt pretension force throughout the tests.
The results indicated that: 1) From 20 ℃ to 130 ℃, effects of temperature on slipping load and displacement were measured. Reductions were observed while temperature rising to 130 ℃ and it showed 0.9%~4.3% reduction in anti-slip load, 7.5%~7.8% reduction in mean slip coefficient and 22.4% reduction in bolt pretension.2) From 130 ℃ to 200 ℃, effects of temperature were significant. Comparing to room temperature, reduction about anti-slip load of M30 bolt was 9% and 34% respectively for 130 ℃ and 200 ℃ while reduction about mean slip coefficient was 11% and 7% respectively. Irregular change of bolt pretension was observed under this temperature situation.3) Under room temperature, anti-slip load and mean slip coefficient were decreased in slotted hole bolt connection comparing to standard hole style. Such reduction weakened with the increasing of bolt diameter in slotted hole bolt connection. The anti-slip load dropped 11.0% and 4.0% while the mean slip coefficient decreased 12.0% and 10.0% respectively for M20 and M30 slotted hole bolt connection compared with standard hole style under room temperature.4) At 130 ℃, reductions of slotted hole bolt connection for anti-slip load and mean slip coefficient were 9.0% and 13.0% respectively compared with standard hole style. The reduction was greater at 130 ℃ than room temperature.5) Slotted hole bolt connection would aggravate the relaxation of bolt pretension. Reduction of M30 bolt-pretension was 16.3% for standard hole connection and 30.7% for slotted hole bolt connection. Difference of 14.4% was observed.6) From 20 ℃ to 130 ℃, mean slip coefficient of M20 bolt was about 30.0% greater than that of M30 bolt, indicating that the mean slip coefficient improves with the increase of bolt connection stiffness. However, mean slip coefficient of M30 bolt connection was 12.4% smaller than that of M20 bolt connection at 200 ℃ and there was error in the measurement of mean slip coefficient for M20 bolt connection.7) At 130 ℃, reduction of bolt pretension for M20 and M30 bolt connection was 28.4% and 16.3% respectively, indicating that the bolt pretension relaxation weakens with the increase of bolt connection stiffness. With the temperature increasing to 200 ℃, reduction of mean slip coefficient for M20 bolt connection became obvious and greater with higher discreteness than that of 130 ℃. However, pretension of M30 bolt connection showed up and down changes without obvious pattern for temperature rising to 200 ℃.