Login
Register
Steel Construction Published the List of Highly Influential Articles of 2020
2020 Vol. 35, No. 11
Display Method:
2020, 35(11): 1-24.
doi: 10.13206/j.gjgSE20042101
Abstract
PDF (32065KB)
Abstract:
The staggered truss framing (STF) structural system is an efficient, practical and highly economical framing system, and it follows the trend of building industrialization. The STF structural system has been widely used in areas of low earthquake risk, and the merits make this system attractive in moderate to high seismic regions. The truss can be a hybrid truss, a vierendeel truss or a pratt truss. Compared with the vierendeel truss and the pratt truss, the hybrid truss is the most widely used because of its moderate rigidity and its vierendeel panel which can be set as an inner corridor. Existing tests have shown that the hybrid STF structural system has good mechanical performance but poor seismic performance and weak energy consumption capacity, and the soft storey problem is prone to occur. To enhance the seismic behaviour of STF structural systems, this paper proposed a ductile STF structure in which two-side connecting steel plates (TSCSPs) are set in the middle of the truss span and the middle span is taken as an energy dissipation section to dissipate energy. The ductile STF structure is called the two-side connecting steel plate-staggered truss framing (TSCSP-STF) structure. The steel plates of energy dissipation section would not buckle nor yield under frequent earthquakes, while only the steel plates would yield and dissipate energy under major and infrequent earthquakes. The non-dissipative sections of the truss remain elastic. In this way, the ductility and energy dissipation capacity of the traditional hybrid STF structure can be improved, and the instability and brittle failure of the web members can be mitigated or avoided.
The calculation method for the shear capacity demands of the TSCSP was derived from analyzing the shear capacity demands of the energy dissipation section. Assuming TSCSP as eccentric cross brace, we established a simplified analysis model of the TSCSP-STF structure, and then the plastic design method and process of the system. Further, a 10-story TSCSP-STF structure and a 10-story hybrid STF structure were designed with the same design conditions and nearly the same steel consumption. The design goal was to make both structures deplete the energy consumption capacity of the energy dissipation section. The seismic behaviours of the two specimens were investigated by the mode-superposition response spectrum method and Pushover analysis method.
The analysis results showed that:under the action of frequent earthquakes, the components can maintain elasticity, while under the action of major and infrequent earthquakes, the energy dissipation components can fully dissipate the seismic energy and protect the other components from damage. The plastic hinges of STF specimen were concentrated at the ends of vierendeel chords, and evenly distributed along the height of the building. The plastic hinges of TSCSP-STF specimen mainly appeared on the ties and struts of the energy dissipation sections, and the distribution was also relatively uniform. Both the TSCSP-STF structure and the hybrid STF structure designed according to the plastic design method can meet the requirements of the code for load-carrying capacity, deformation and stability under major and infrequent earthquakes. The drift of TSCSP-STF specimen was more uniformly distributed, reducing the possibility of soft-story, and has relatively better ductility.
The staggered truss framing (STF) structural system is an efficient, practical and highly economical framing system, and it follows the trend of building industrialization. The STF structural system has been widely used in areas of low earthquake risk, and the merits make this system attractive in moderate to high seismic regions. The truss can be a hybrid truss, a vierendeel truss or a pratt truss. Compared with the vierendeel truss and the pratt truss, the hybrid truss is the most widely used because of its moderate rigidity and its vierendeel panel which can be set as an inner corridor. Existing tests have shown that the hybrid STF structural system has good mechanical performance but poor seismic performance and weak energy consumption capacity, and the soft storey problem is prone to occur. To enhance the seismic behaviour of STF structural systems, this paper proposed a ductile STF structure in which two-side connecting steel plates (TSCSPs) are set in the middle of the truss span and the middle span is taken as an energy dissipation section to dissipate energy. The ductile STF structure is called the two-side connecting steel plate-staggered truss framing (TSCSP-STF) structure. The steel plates of energy dissipation section would not buckle nor yield under frequent earthquakes, while only the steel plates would yield and dissipate energy under major and infrequent earthquakes. The non-dissipative sections of the truss remain elastic. In this way, the ductility and energy dissipation capacity of the traditional hybrid STF structure can be improved, and the instability and brittle failure of the web members can be mitigated or avoided.
The calculation method for the shear capacity demands of the TSCSP was derived from analyzing the shear capacity demands of the energy dissipation section. Assuming TSCSP as eccentric cross brace, we established a simplified analysis model of the TSCSP-STF structure, and then the plastic design method and process of the system. Further, a 10-story TSCSP-STF structure and a 10-story hybrid STF structure were designed with the same design conditions and nearly the same steel consumption. The design goal was to make both structures deplete the energy consumption capacity of the energy dissipation section. The seismic behaviours of the two specimens were investigated by the mode-superposition response spectrum method and Pushover analysis method.
The analysis results showed that:under the action of frequent earthquakes, the components can maintain elasticity, while under the action of major and infrequent earthquakes, the energy dissipation components can fully dissipate the seismic energy and protect the other components from damage. The plastic hinges of STF specimen were concentrated at the ends of vierendeel chords, and evenly distributed along the height of the building. The plastic hinges of TSCSP-STF specimen mainly appeared on the ties and struts of the energy dissipation sections, and the distribution was also relatively uniform. Both the TSCSP-STF structure and the hybrid STF structure designed according to the plastic design method can meet the requirements of the code for load-carrying capacity, deformation and stability under major and infrequent earthquakes. The drift of TSCSP-STF specimen was more uniformly distributed, reducing the possibility of soft-story, and has relatively better ductility.
2020, 35(11): 25-39.
doi: 10.13206/j.gjgSE20042102
Abstract:
Stagger truss structure system was derived from the middle of 1960s, with the advantages of open space, free layout, light weight, and convenient construction. The internal force of the frame column in stagger truss system is generally small because of the good overall mechanical performance and light weight, so the design of the steel column in the structure is usually controlled by the slenderness ratio. Construction Technology Co., Ltd. designed an RC column-staggered truss structure by replacing the conventional steel columns with precast RC columns. The application of the precast RC columns reduces the cost of the structure without reducing the quality and the convenient construction. A finite element model of a 9-story RC column-staggered truss structure in an area of 7-degree (0.1g) seismic fortification intensity was established by MSC. MARC software based on a practical project and the pushover analysis was conducted. According to the performance point of the structure, the seismic performance of the structure was analyzed in terms of the story drift, inter-story drift ratio, and member yielding sequence. Three models of removing partial diagonal web members were established based on the original model, and the failure effect of partial diagonal web members on seismic performance was analyzed.
The results are as follows:1) The maximum inter-story drift ratio of the RC column-staggered truss structure under the action of frequent earthquakes and rare earthquakes is far less than the limit value of the Specification for Design of Staggered Steel Truss Framing Systems (JGJ/T 329-2015). The maximum inter-story drift ratio appeared at the third and second floors. 2) The first yield diagonal web appeared in the of the middle and lower part of the stagger truss near the outside. With the increase of the seismic action, the diagonal web of the staggered truss on the inside also gradually yielded. 3) The structural capacity curves of the structures with diagonal web failures are basically the same as those of the original structures. With the increase of seismic fortitution level, the difference of peak displacement decreases from 8% to 3%. 4) The structural capacity curve does not decrease significantly with the failure of the partial diagonal web. The maximum inter-story drift ratio of the structure with partial diagonal web removed respectively increased by 11.9% and 32.7% under frequent earthquakes and rare earthquakes. The structure with partial diagonal web removed can still meet the design requirements of Specification for Design of Staggered Steel Truss Framing Systems (JGJ/T 329-2015). 5) There are 2-4 more members yielding in the structure with partial diagonal web removed, but the overall structure is still in an elastic state. the RC column-staggered truss structure has the characteristics of high rigidity and good seismic performance, meeting the seismic performance requirements of "no damage under frequent earthquake, no unrepairable damage under design-based earthquake, and no collapse under rare earthquake". The structures without partial diagonal web members show inferior seismic performance than the original one, but they can still meet the design requirements.
Stagger truss structure system was derived from the middle of 1960s, with the advantages of open space, free layout, light weight, and convenient construction. The internal force of the frame column in stagger truss system is generally small because of the good overall mechanical performance and light weight, so the design of the steel column in the structure is usually controlled by the slenderness ratio. Construction Technology Co., Ltd. designed an RC column-staggered truss structure by replacing the conventional steel columns with precast RC columns. The application of the precast RC columns reduces the cost of the structure without reducing the quality and the convenient construction. A finite element model of a 9-story RC column-staggered truss structure in an area of 7-degree (0.1g) seismic fortification intensity was established by MSC. MARC software based on a practical project and the pushover analysis was conducted. According to the performance point of the structure, the seismic performance of the structure was analyzed in terms of the story drift, inter-story drift ratio, and member yielding sequence. Three models of removing partial diagonal web members were established based on the original model, and the failure effect of partial diagonal web members on seismic performance was analyzed.
The results are as follows:1) The maximum inter-story drift ratio of the RC column-staggered truss structure under the action of frequent earthquakes and rare earthquakes is far less than the limit value of the Specification for Design of Staggered Steel Truss Framing Systems (JGJ/T 329-2015). The maximum inter-story drift ratio appeared at the third and second floors. 2) The first yield diagonal web appeared in the of the middle and lower part of the stagger truss near the outside. With the increase of the seismic action, the diagonal web of the staggered truss on the inside also gradually yielded. 3) The structural capacity curves of the structures with diagonal web failures are basically the same as those of the original structures. With the increase of seismic fortitution level, the difference of peak displacement decreases from 8% to 3%. 4) The structural capacity curve does not decrease significantly with the failure of the partial diagonal web. The maximum inter-story drift ratio of the structure with partial diagonal web removed respectively increased by 11.9% and 32.7% under frequent earthquakes and rare earthquakes. The structure with partial diagonal web removed can still meet the design requirements of Specification for Design of Staggered Steel Truss Framing Systems (JGJ/T 329-2015). 5) There are 2-4 more members yielding in the structure with partial diagonal web removed, but the overall structure is still in an elastic state. the RC column-staggered truss structure has the characteristics of high rigidity and good seismic performance, meeting the seismic performance requirements of "no damage under frequent earthquake, no unrepairable damage under design-based earthquake, and no collapse under rare earthquake". The structures without partial diagonal web members show inferior seismic performance than the original one, but they can still meet the design requirements.
2020, 35(11): 40-54.
doi: 10.13206/j.gjgSE20042001
Abstract:
The staggered truss structural system originated from America in the 1960s, which has been widely used. Typical staggered truss structural system consists of columns, floors, plane trusses, etc. The H-shaped steel, steel pipe, and concrete-filled steel tube (CFT) can be used as structural columns. The slabs can be designed to be hollow slab, composite slab, cast-in-place reinforced concrete slab, etc. In addition, there are three typical types of trusses, i. e. open-web truss, parker truss, and hybrid truss. This structural system has advantages of large space, light structural weight, convenient construction process, economic benefits, high efficiency, and environmentally friendly. In addition, the structure has light weight and good integrity, resulting in a small internal force of the column. When steel columns are used, the slenderness ratio is usually considered as the design control condition, resulting in a waste of materials. The precast reinforced concrete (RC) column is characterized by solid section and convenient construction process. Application of precast RC column into the staggered truss structural system can make better use of the mechanical properties of the column and improve economic benefits of this type of structural system. However, a robust column to truss joint is necessary for the application of RC columns. China Construction Science & Technology Co., Ltd., designed and developed a prefabricated staggered truss structural system consisting of RC columns, steel trusses and pre-stressed concrete floor. The inelastic static analysis of this structural system was conducted by Chongqing University to evaluate its seismic performance. A host of experimental and theoretical studies have been conducted to investigate the seismic performance of the truss and staggered truss structural system. For the column to truss joint of staggered truss structural system, preliminary investigations are still limited, and previous studies mainly focused on the mechanical performance of steel or CFT column to truss joint.
In this study, a finite element model (FEM) is established to investigate the mechanical behavior of the proposed RC column to truss joint used in a practical project. The stress distribution, internal force and loaddisplacement curves of the joint under five kinds of most unfavorable working conditions in the structural analysis are analyzed. The investigated parameters include the axial load ratio of RC column, with/without restriction of chord horizontal displacement, and load condition of web members. The results are as follows:1) The internal force of the member can be transferred to the corbel or embedded steel plate through the gusset plate and then transferred to the column through the anchor bars, demonstrating that the joint is designed reasonably with a clear force transfer path. 2) All kinds of members yield before of reinforcement within the joint region, meeting the design requirement of "strong joint and weak member". 3) The material strength of the chord and web is better used in the case where the horizontal displacement of the chord is restricted despite of a lower degree of reinforcement stress development in the RC column. 4)The load bearing capacity and displacement are greater in the cases where the horizontal displacement of the chord is not released, which is benefit from a better use of material strength of the chord and web member. In the case whose axial load ratio is 0, the load of the web member increases approximately linearly with increasing the displacement of the web member at the initial loading stage. The plastic deformation within the joint region gradually increases once the displacement of the web member exceeds 5 mm, resulting in a slower increase of the load of the web member. 5) The bending moment and shear force of the chord are generally small in all working conditions except for the shear force in the case whose axial load ratio is 0. The axial force of the chord is significantly larger in the cases where the horizontal displacement is restricted and the axial force of the chord increases by approximately 10%. 6) It is suggested to appropriately increase the longitudinal reinforcement ratio of the RC column to alleviate the eccentric effect of the column caused by the corbel, further improve its safety reserve.
The staggered truss structural system originated from America in the 1960s, which has been widely used. Typical staggered truss structural system consists of columns, floors, plane trusses, etc. The H-shaped steel, steel pipe, and concrete-filled steel tube (CFT) can be used as structural columns. The slabs can be designed to be hollow slab, composite slab, cast-in-place reinforced concrete slab, etc. In addition, there are three typical types of trusses, i. e. open-web truss, parker truss, and hybrid truss. This structural system has advantages of large space, light structural weight, convenient construction process, economic benefits, high efficiency, and environmentally friendly. In addition, the structure has light weight and good integrity, resulting in a small internal force of the column. When steel columns are used, the slenderness ratio is usually considered as the design control condition, resulting in a waste of materials. The precast reinforced concrete (RC) column is characterized by solid section and convenient construction process. Application of precast RC column into the staggered truss structural system can make better use of the mechanical properties of the column and improve economic benefits of this type of structural system. However, a robust column to truss joint is necessary for the application of RC columns. China Construction Science & Technology Co., Ltd., designed and developed a prefabricated staggered truss structural system consisting of RC columns, steel trusses and pre-stressed concrete floor. The inelastic static analysis of this structural system was conducted by Chongqing University to evaluate its seismic performance. A host of experimental and theoretical studies have been conducted to investigate the seismic performance of the truss and staggered truss structural system. For the column to truss joint of staggered truss structural system, preliminary investigations are still limited, and previous studies mainly focused on the mechanical performance of steel or CFT column to truss joint.
In this study, a finite element model (FEM) is established to investigate the mechanical behavior of the proposed RC column to truss joint used in a practical project. The stress distribution, internal force and loaddisplacement curves of the joint under five kinds of most unfavorable working conditions in the structural analysis are analyzed. The investigated parameters include the axial load ratio of RC column, with/without restriction of chord horizontal displacement, and load condition of web members. The results are as follows:1) The internal force of the member can be transferred to the corbel or embedded steel plate through the gusset plate and then transferred to the column through the anchor bars, demonstrating that the joint is designed reasonably with a clear force transfer path. 2) All kinds of members yield before of reinforcement within the joint region, meeting the design requirement of "strong joint and weak member". 3) The material strength of the chord and web is better used in the case where the horizontal displacement of the chord is restricted despite of a lower degree of reinforcement stress development in the RC column. 4)The load bearing capacity and displacement are greater in the cases where the horizontal displacement of the chord is not released, which is benefit from a better use of material strength of the chord and web member. In the case whose axial load ratio is 0, the load of the web member increases approximately linearly with increasing the displacement of the web member at the initial loading stage. The plastic deformation within the joint region gradually increases once the displacement of the web member exceeds 5 mm, resulting in a slower increase of the load of the web member. 5) The bending moment and shear force of the chord are generally small in all working conditions except for the shear force in the case whose axial load ratio is 0. The axial force of the chord is significantly larger in the cases where the horizontal displacement is restricted and the axial force of the chord increases by approximately 10%. 6) It is suggested to appropriately increase the longitudinal reinforcement ratio of the RC column to alleviate the eccentric effect of the column caused by the corbel, further improve its safety reserve.
2020, 35(11): 55-64.
doi: 10.13206/j.gjgS20042601
Abstract:
Staggered truss structure is a new type of fabricated steel structure system with the characteristics of large span, large space, large stiffness and good economy. However, due to its unique structure, the calculation method of the fabricated staggered truss structure system is completely different from the traditional steel frame structure, especially the assumption of the floor has a great influence on the overall calculation of the staggered truss structure system; and how to consider the influence of the construction on the plane truss in the calculation and analysis of the fabricated staggered truss structure in the design stage is also the control index. Based on the analysis of the key technology of staggered truss structure, and combined with Hangzhou Xiaoshan International Airport No. 5 and No. 6 apartment building project as an example, this paper focuses on the truss layout and floor calculation of staggered truss structure in the process of design and construction, as well as the elastic response spectrum method analysis and static elastic-plastic analysis of the project, and explores the plastic development mechanism of staggered truss structure. The research shows that the simplified floor calculation model solves the calculation problems in the design stage of staggered truss, and it is a kind of modeling calculation method that can be directly applied; and through the comparative analysis of two finite element analysis software of etbas and YJK, the fabricated staggered truss structure of steel structure has good energy dissipation mechanism and seismic performance, which is worthy of popularization and application Structure system.
Staggered truss structure is a new type of fabricated steel structure system with the characteristics of large span, large space, large stiffness and good economy. However, due to its unique structure, the calculation method of the fabricated staggered truss structure system is completely different from the traditional steel frame structure, especially the assumption of the floor has a great influence on the overall calculation of the staggered truss structure system; and how to consider the influence of the construction on the plane truss in the calculation and analysis of the fabricated staggered truss structure in the design stage is also the control index. Based on the analysis of the key technology of staggered truss structure, and combined with Hangzhou Xiaoshan International Airport No. 5 and No. 6 apartment building project as an example, this paper focuses on the truss layout and floor calculation of staggered truss structure in the process of design and construction, as well as the elastic response spectrum method analysis and static elastic-plastic analysis of the project, and explores the plastic development mechanism of staggered truss structure. The research shows that the simplified floor calculation model solves the calculation problems in the design stage of staggered truss, and it is a kind of modeling calculation method that can be directly applied; and through the comparative analysis of two finite element analysis software of etbas and YJK, the fabricated staggered truss structure of steel structure has good energy dissipation mechanism and seismic performance, which is worthy of popularization and application Structure system.
