Chinese Design Code Research Articles

A Discussion on Adaptive Applications of Some Chinese Design Codes in Guinea and Localization of Flood Standards

Chinese engineering team participated in the construction of several water conservancy and hydropower projects in areas which have differences in climate characteristics from China. Due to a lack of hydrological and climatic data and the absence of systematic design specifications in these areas, considering construction safety, most of the Chinese designs and constructions are based on the extreme values with the Chinese design codes. The S Project in Guinea established a rainfall-runoff model through open-source remote sensing satellite precipitation data and limited hydrological station measured runoff data，allowing to refine local hydrological data. Based on these data series, it was then possible to calculate flood control standards with more local hydrological characteristics in order to promote the progress of the project scientifically. In addition, combining the refined discharging curve of the outlet hole with the latest arc gate online monitoring technology, and the joint dispatch with the downstream hydropower station, permitted that the downstream K Hydropower Station created historic power generation in 2019 with significant economic and social benefits.

Seismic Intensity Measures and Fragility Analysis for Subway Stations Subjected to Near-fault Ground Motions with Velocity Pulses

ABSTRACT The purpose of this study is to explore the optimum seismic IMs for the probabilistic seismic demand model of subway stations subjected to near-fault seismic excitations with velocity pulses, and establish the seismic fragility curves based on the optimum seismic IMs. A two-storey three-span subway station is used herein as a representative case study for the cut-and-cover rectangular underground structure. Because the dynamic response of underground structure is closely related to the properties of the surrounding soil/rock, four typical classes of engineering sites covering Classes I to IV are selected in accordance with the Chinese code for seismic design of urban rail transit structures. Nonlinear time history analyses considering soil–structure interaction (SSI) are conducted on the two-dimensional numerical model of the subway station embedded in four different engineering sites. An ensemble of 121 near-fault seismic excitations with velocity pulses is used in seismic dynamic analyses so as to define the optimum IMs. Each seismic excitation is converted into the free field load at artificial boundaries of discretized numerical model of SSI system. The efficacy of 21 commonly used ground motion IMs for predicting seismic response of shallowly buried subway stations is discussed in this study. Four different criteria characterizing the adequacy of IMs, including efficiency, practicality, proficiency and sufficiency, are used in identification of the optimum IMs, on account of the statistical regression results of the selected IMs and engineering demand parameters of the subway station structure measured by maximum inter-story displacement ratio. It is concluded that for engineering sites of Classes I and II, the sustained maximum acceleration followed by peak ground acceleration are the optimum IMs, and for engineering sites of Classes III and IV, the velocity spectrum intensity is the optimum IM. Finally, based on the optimized seismic IMs, the fragility curves of subway station embedded in different site classes are developed in this study.

Experimental Investigation and Design of Hollow Section, Centrifugal Concrete-Filled GFRP Tube Columns

The compressive response of hollow section, centrifugal concrete-filled GFRP tube (HS-CFGT) members is examined experimentally and reported analytically in this paper. A total of 17 specimens separated into two groups were tested; the specimens in each group were of four different lengths and included thirteen straight columns and four tapered columns. The details of the test rigs, procedures as well as key test observations composed of ultimate-moment capacities, load-displacement curves, and failure modes were truthfully reported. The test results were analyzed to evaluate the influence of initial eccentricity on the structural performance. Therefore, the aim of this paper is: (1) to propose a proper coefficient, φe, reflecting the effect of initial eccentricity based on the Chinese design code; and (2) to determine a new confinement coefficient, kcc = 1.10, for centrifugal concrete confined by GFRP tubes. Comparisons of the present design codes and specifications of confined concrete members with test results on 17 full-scale tube columns are also presented. Accordingly, new design equations, whose predictions generally agree well with the test results, are recommended to estimate the compressive capacity of the proposed HS-CFGT columns.

An Experimental Study on the Mechanical Properties of a High Damping Rubber Bearing with Low Shape Factor

A high damping rubber bearing (HDRB) is widely utilized in base-isolation structures due to its good energy dissipation capacity and environmentally friendly properties; however, it is incapable of isolating the vertical vibration caused by earthquakes and subways effectively. Thick rubber bearings with a low shape factor have become one of the important vertical isolation forms. This paper provides an experimental comparative study on high damping rubber bearings with low shape factor (HDRB-LSF), thick lead–rubber bearings (TLRB), and lead–rubber bearings (LRB). The abilities of the bearing and energy dissipation of the above bearings are analyzed contrastively considering the influence of vertical pressure, loading frequency, shear strain, and pre-pressure. Firstly, the HDRB-LSF, TLRB, and LRB are designed according to the Chinese Code for seismic design of buildings. Secondly, cyclic vertical compression tests and horizontal shear tests, as well as their correlation tests, are conducted, respectively. The vibrational characteristics and hysteresis feature of these three bearings are critically compared. Thirdly, a corrected calculation of vertical stiffness for the thick rubber bearings is proposed based on the experimental data to provide a more accurate and realistic tool measuring the vertical mechanical properties of rubber bearings. The test results proved that the HDRB-LSF has the most advanced performance of the three bearings. For the fatigue property, the hysteresis curves of the HDRB-LSF along with TLRB are plump both horizontally and vertically, thus providing a good energy dissipation effect. Regarding vertical stiffness, results from different loading cases show that the designed HDRB-LSF possesses a better vertical isolation effect and preferable environmental protection than LRB, a larger bearing capacity, and, similarly, a more environmentally friendly property than TLRB. Hence, it can avoid the unfavorable resonance effect caused by vertical periodic coupling within the structure. All the experimental data find that the proposed corrected equation can calculate the vertical stiffness of bearings with a higher accuracy. This paper presents the results of an analytical, parametric study that aimed to further explore the low shape factor concepts of rubber bearings applied in three-dimensional isolation for building structures.

The influence of incident angles and length-diameter ratios on the round-ended cylinder under regular wave action

The round-ended cylinder is commonly applied in coastal engineering as foundation. While researches related to the round-ended cylinder are pretty limited. In the present study, the influence of the incident wave angles and length-diameter (LD) ratios is investigated through numerical simulation. An equation is then proposed to calculate the maximum horizontal wave force based on numerical solutions and verified by random cases. Additionally, results of numerical simulation, proposed equation, the Chinese design code and the American design code are compared with each other. The results show that the proposed equation has good accuracy and the product of a safety factor, in the range of 1.5–2.0, with the proposed equation result is recommended in practical engineering. Besides, small LD ratios are suggested to be adopted in the structure design.

Influence of venting coefficient on disastrous effects of aluminium powder explosions

Aluminium powder has a very high risk of explosion. To clarify the disastrous effects of the overpressure and high temperatures during an aluminium powder explosion in a constrained space and the distribution of the outdoor safe distance, the explosion and venting processes of aluminium dust in a large-scale building were investigated under different venting coefficients, Kv (Kv = Av/Ap), using computational fluid dynamics (CFD). The results show that although an increase in the venting coefficient can reduce the indoor overpressure and explosion temperature, it can also increase the distance up to which the outdoor overpressure and high temperature can cause damage. Moreover, the distance up to which explosion overpressures can be harmful to personnel and buildings increases with an increase in the venting coefficient. Hence, the safe outdoor distance may be more than 1.5–2 times the fire safe distance listed in the Chinese Code for fire protection design of buildings. The high-temperature damage caused by the explosion also increases with an increase in the venting coefficient. Therefore, the current explosion safety protection distances for aluminium powder production sites need to be revised.

An experimental study of the seismic behaviour of precast concrete shear walls with bolted-plate connections

The seismic resistance of an innovative precast reinforced concrete shear wall with vertical plates along its bottom edge to be bolted to plates protruding from the foundation was tested in reduced-scale model in the laboratory. Five precast shear walls with different wall heights and axial loads, as well as one reference cast-in-place shear wall, were tested. Horizontal cyclic loading was applied to examine the seismic performance of the specimens. The failure modes of the shear walls are discussed, along with their hysteretic behaviour, stiffness degradation, energy dissipation capacity, slip at the bolted connections, and strains in the reinforcement and in the connecting plates. The test results show that the bolted-plate connections can effectively transfer vertical and shear forces, as well as bending moments, to the foundation beam without any slip along the connection. The precast specimens exhibited approximately the same seismic behaviour as the cast-in-place one. In general, the failure mode shifts from compression-bending to shear-compression at smaller heights of the walls, with an increase in the bearing capacity, but a reduction in wall deformability and the energy-dissipation capability. At smaller values of the axial loads, the bearing capacity decreases but the deformability increases. The existing Chinese design code for normal reinforced concrete shear walls gives safe design limits also for the precast walls with bolted-plate connections.

Evaluation of the collapse mode of isolated structures subjected to multi-directional dynamic coupling excitation based on reliability theory

The identification of the structural collapse mode is an important foundation of structural anti-collapse design and safety evaluation. The collapse mode evaluation method based on probability reliability is widely used in theoretical research and engineering applications. However, studies on the collapse mode of isolated structures have rarely been reported. For the initial damage, the main control excitation and the remaining system constraints of isolated structures all being different from that of traditional fixed-base structures, the collapse mode and the collapse mechanical behaviors of the isolated structure are disparate from the traditional fixed-base structures. The most likely collapse mode of isolated structures subjected to multi-directional dynamic coupling excitation is evaluated based on reliability theory in the presented research work. First, multi-directional dynamic coupling analysis on the isolated structure is performed. Then, a reliability analysis method suitable for isolated structures is proposed, which takes the damage index as the state parameter, and calculates the failure probability based on the quadratic fourth-order moment theory method. The structural collapse probabilities under different collapse modes are calculated, in order to evaluate the most likely collapse mode of the isolated structure. Finally, the identification method is applied to one prototype isolated structure designed in accordance with the Chinese design code. The results indicate that the identification method based on cumulative damage and reliability theory could effectively be used for evaluation of the most likely collapse mode of the isolated structure.

Seismic Performance of CFST Frame-Steel Plate Shear Walls Connected to Beams Only

The safety and cost of structures composed of concrete-filled steel tube (CFST) frame-steel plate shear walls (SPSWs) with two-side connections are governed by the seismic performance. The response modification factor R and displacement amplification factor Cd are important seismic performance factors. In this paper, nonlinear seismic responses of 10-story, 15-story, and 20-story CFST frame-SPSWs (CFST-SPSWs) are studied. A nonlinear finite element model which includes both material and geometric nonlinearities is developed using the finite element software OpenSees for this study. The accuracy of model was validated by comparing with experimental results. Nonlinear seismic analysis shows that CFST-SPSWs, in high seismic region, behave in a stable and ductile manner. Also, R and Cd of CFST-SPSWs were evaluated for the structure models using incremental dynamic analysis (IDA), and the average values of 3.17 and 3.05 are recommended, respectively. The recommended R value is greater than the value (2.8) in the “Chinese Code for seismic design of buildings” for composite structures, indicating the code is conservative. The structural periods provided by current code are generally lower than the periods calculated by finite element analysis. Research results show that R and Cd increase with increasing story number, span number, and structural period. Ductility reduction factor Rμ increases with increasing span number and decreasing story number. Overstrength factor Rs increases with increasing story number and decreasing span number.

A Spiral Single-Layer Reticulated Shell Structure: Imperfection and Damage Tolerance Analysis and Stability Capacity Formulation for Conceptual Design

Single-layer reticulated shell structures are widely used, but their stability performance is not ideal. Moreover, they are sensitive to structural damage and imperfections, while the existing conventional design methods of increasing the cross-section, strengthening corrosion protection, and densifying the structural grid are not economical. This study employs a modified and bionic structure—a spiral single-layer reticulated shell structure—to solve the problem. First of all, according to the current Chinese design codes, its mathematical model and geometric model are designed. Then, its damage and imperfection tolerances are analyzed and compared with a traditional single-layer reticulated shell. We then propose a universal bearing capacity formula. Our research conclusions prove that the spiral single-layer reticulated shell structure has a higher tolerance to damage and imperfections while maintaining stability. Moreover, the precise bearing capacity formula proposed will help engineers to efficiently select the structure configurations in the conceptual design phase. Therefore, the spiral single-layer reticulated shell structure is worthy of popularization and application in engineering practice.

Stiffness amplification coefficient for composite frame beams considering slab spatial composite effect

The slab spatial composite effect arises due to compatible deformation of the reinforced concrete slab with the steel beam in composite frames. This effect can significantly amplify the stiffness of composite frame beams. Current Chinese design code adopts the stiffness amplification coefficient method for the design of composite frame beams, and the equivalent moment of inertia of the composite frame beam can be calculated to conduct the global analysis. However, the current formulae are only suitable for lateral load cases and symmetric I-shaped steel section. Therefore, this study aims to propose unified design equations of the stiffness amplification coefficient considering both vertical and lateral load cases and both symmetric and asymmetric I-shaped steel sections to address the aforementioned limitations. A series of parametric finite element analyses using the beam-shell mixed element model are conducted to derive the unified design equations. The reasonability of the proposed equations is verified by comparing the critical structural indices, such as the natural vibration period, inter-storey shear, lateral displacement, bending moment, and deflection distribution of numerical examples of multi-storey composite frames. Good accuracy is obtained through the comparison between the linear beam element model modified by the proposed equations and the beam-shell mixed element model.

Seismic Performance of Frame–Shearwall Structure with Long-Span and High-Level Steel Transfer Trusses

Based on a shaking table experiment a 1:25 scaled frame–shearwall structure model with large-span steel transfer trusses and finite-element analysis, the dynamic characteristics, seismic responses in the elastic and elastic–plastic phases, and destructive forms of the structure were studied. It was observed that cracks developed as the earthquake wave acceleration increased, but no severe cracking developed in the structure during the experiment. In the seismic responses caused by the artificial accelerogram, the site accelerogram and the El Centro accelerogram, that caused by the artificial accelerogram was the most intense. The interstory drift between transfer stories is large, which means that the transfer stories might be weak. However, the seismic performance of the steel truss transfer stories was good and the structural system was able to meet the seismic requirements regulated by the Chinese Design Code.

The seismic analysis and performance of steel frame with additional low-yield-point steel dampers

This paper describes the seismic performance of a steel frame with additional LYP steel dampers. LYP steel dampers provides passive energy dissipation device in a structure, it also reduces the lateral forces in efficient way which is produced by seismic wave. The seismic performance of structures is needed in the design of structure, especially in countries where seismic activities occur. This analysis is accomplished with the FEM and software called SAP2000. The steel frame is only analyzed using numerical simulation. This paper describes two steel frames, the first steel frame is a two story steel frame without LYP steel dampers while the second steel frame has with LYP steel dampers. The seismic mechanism analysis was accomplished with the help of nonlinear time history analysis technique and the results for inter-story drift, steel frames, base shear, the displacement of the top story and the stress of the dampers was obtained. The time history analysis was taken out with three different earthquake waves according to the Chinese code for the seismic design of buildings; the earthquake waves were divided into the three different earthquake levels in China which include the frequent, moderate and rare earthquake level. The seismic mechanism analysis was accomplished on the three different earthquakes and three different earthquake levels in China. The modal analysis was taken to obtain the frequency and the period of the steel frames. The steel frames were examined under the different load combination which is also described in the code for the seismic design of buildings to obtain the internal forces of the members of the steel frame which include the axial force, shear force and bending moment. The different load combinations are used to get the stress of the dampers. We notice that the addition of LYP steel dampers increases the seismic resistance of the steel frame as we can observe by a reduction in the displacement of the top story, base shear, and inter-story drift angle by the addition of LYP steel dampers on the steel frame. We can be able to observe the behavior of the frames under the different earthquake levels in China using the pushover analysis.

Comparison of seismic performance between typical structural steel buildings designed following the Chinese and United States codes

In this study, comparative investigations of a typical steel moment frame and a steel frame-braced core-tube structure, designed following different seismic codes, are conducted to evaluate the significant differences between the Chinese and the United States (US) seismic codes for steel buildings. The study outcomes can enhance the understanding of the differences in steel structure design between two countries, especially the differences in seismic performance. Specifically, the design outputs of the structural components, material consumptions, dynamic characteristics, and seismic loads were analyzed. Subsequently, finite element (FE) models based on the design outputs were established to assess the seismic performance and collapse margin. Furthermore, the local buckling effect of the steel components can be considered in the FE model, which can effectively predict the buckling-induced strength deterioration under excessive deformation. The comparison results reveal that, under the same design conditions in this study, both the strength requirement and deflection limit are critical factors that control the typical buildings design following the Chinese codes. However, the strength requirement is the primary factor that controls the design outcomes following the US codes. Moreover, the collapse resistance of the steel moment frames from both codes are similar, but the material consumption based on the Chinese design code is comparatively higher. In contrast, the material consumption of the steel frame-braced core-tube structures are comparable, but the collapse resistance of the US design code is better. Furthermore, the collapse analyses indicate that the local buckling effect could significantly reduce the collapse resistance.

Test on mechanical behavior of SRC L-shaped columns under combined torsion and bending moment

Investigations of the seismic behavior of steel reinforced concrete L-shaped columns under constant axial compression and cycled bending-shear-torsion load were performed. Six specimens, which considered two parameters, i.e., the moment ratio of torsion to bending (γ) and the aspect ratio (column length-to-depth ratio, ϕ), were prepared for the experiment. In this study, the failure process, torsion-displacement hysteresis curves, and flexure-displacement hysteresis curves were obtained. The failure characteristics, mechanical behavior of specimens such as the failure patterns, hysteresis curves, rigidity degradation, ductility and energy dissipation, are analyzed. The experimental research indicated that the major failures of the specimens were bending failure, bending-shear failure and bending-torsion failure as the moment ratio of torsion to bending (γ) increased. The torsion-displacement hysteresis curves were pinched in the middle, formed a slip platform, and the phenomenon of “load drop” occurred after the peak load. The bending-displacement hysteresis curves were plump, which showed that bending capacity of the specimen was better than its torsion capacity. Additionally, the energy dissipation of the specimen was dominated by torsion in the early stage and ultimately governed by the bending moment in the later phase. Test results also indicated that the displacement ductility coefficient and interstory rotation angle of the failure point were less than 3.0 and 1/50, respectively, which means the test specimen performance does not meet the requirement of the Chinese Code for Seismic Design of Buildings (GB 50011–2014) in this respect.

Suitability of Seismic Isolation for Buildings Founded on Soft Soil. Case Study of a RC Building in Shanghai

Base (seismic) isolation is a promising technology for seismic protection of buildings and other constructions. Nowadays, it is accepted that such a technique is efficient and reliable; however, it has two major limitations: soft foundation soil, and tall buildings. The first issue restrains the seismic isolation spreading, given that soft soil is frequent in densely populated areas, and usually such a soil type concentrates the highest seismicity levels. This paper aims to contribute to demonstrating that base isolation, if properly implemented, can be suitable for soft soil. A representative case study is analyzed: a 6-story reinforced concrete (RC) building with base isolation that has recently been built in Shanghai. Since the building is founded on soft soil, concern regarding base isolation suitability arose; even the Chinese design code does not recommend this solution for soft soil. To clarify this issue, non-linear time-history analyses are carried out for a number of natural and artificial seismic inputs that represent the site seismicity; the superstructure behavior is linear, while nonlinearities are concentrated in the isolation layer. The adequacy of base isolation is assessed in the superstructure (in terms of reduction of interstory drift, absolute acceleration and shear force) and in the isolation layer (in terms of axial force, torsion angle and shear strain). The relevance of soil–structure interaction is discussed. The behavior when the mechanical parameters of the isolation units have experienced important changes is also analyzed. The major conclusion is that base isolation of ordinary mid-height RC buildings founded on soft soil can perform satisfactorily in medium seismicity regions.

Experimental and numerical study on impact behavior of beam-column substructures of steel frame

In this paper, three welded flange-bolted web (WFBW) beam-column connections with three types of weld access holes (fan-shaped, enlarged and FEMA weld access holes) were experimentally examined under impact loading. The design of such connections was based on the North American seismic code FEMA350 and the Chinese design codes. The impact tests on of the connections were conducted to experimentally study the dynamic collapse of a steel frame under a column removal scenario. The dynamic responses including failure modes and time history process of the substructures were obtained and presented. Test results show that the weld access hole has a significant effect on impact behavior of the connections under impact loading. Different failure modes of the specimens were observed and discussed. The specimen with FEMA weld access hole is found to have a great advantage of improved structural ductility, impact resilience as well as energy dissipation and no obvious reduction of the plastic rotation capacity over the other two specimens. The specimens with enlarged and FEMA weld access holes show better rotation capacity to resist impact loads, while its ultimate rotation reach the seismic design limit in FEMA350 standard for WFBW connection. The steel frame with WFBW connection is difficult to give full allowance to catenary action due to the premature failure of connection. Furthermore, the finite element analyses give reasonable accuracy when compared with the test results. The simulation results can be used in the future to predict failure modes and ductile fracture of steel frame connections with different types of weld access holes.

Fatigue behaviour and design of corroded reinforced concrete beams intervened by ICCP-SS

To improve the fatigue resistance of degraded reinforced concrete (RC) beams, the present study employs a dual-functional intervention, impressed current cathodic protection and structural strengthening (ICCP-SS). This paper presents the results of an experimental and analytical study of the fatigue performance of corroded simply supported beams with ICCP-SS intervention. The experimental programme comprises 16 RC beams subjected to accelerated corrosion and ICCP followed by four-point bending tests. The test results show that the corrosion of the steel reinforcements in the cathodically protected beams is effectively prevented. More importantly, the ICCP-SS intervention significantly enhances the fatigue resistance of the flexural members. In comparison to those of the corroded beams without any additional measures, the fatigue lives of the treated beams are significantly improved, by as much as 202%. The beams with the ICCP-SS intervention fail due to fatigue fracture of the steel reinforcement followed by a combination of slippage and rupture of the carbon fibre meshes. An amount of ductility is observed at the point of failure of the beams subjected to ICCP-SS intervention. In addition, the experimental results are compared with the predictions of the European and Japanese design codes as well as the Chinese design codes.

Application of Buckling Restrained Braces to Upgrade Vertical Stiffness of Existing RC Frames

Abstract In this paper, based on the RC frame structure of an industrial building, the finite element model of the structure is developed, according to the Chinese code for seismic design of buildings [9]. Considering the lack of seismic performance, the buckling restrained brace (BRB) is adopted for seismic retrofitting, and various configurations of buckling restrained support are considered for reinforcement. The elastic response spectrum analysis (RSA) and direct integration nonlinear time history analyses (NL-TH) are carried out for the frame structure before and after reinforcement using ETABS finite element software. From the joints displacement, inter-story displacement, inter-story shear force, acceleration, energy dissipation, and other aspects of the seismic response of the strengthened structure and the non-strengthened structure, the comparison has been made. The effect of buckling restrained support and common support on the existing building structure is verified through analytical modeling. After reinforcement, there is a 40%, 39.3%, 40%, 36.4%, and 38.3% reduction in the first period of vibration after the building is strengthened by inverted BRB, V BRB, two-story BRB, single BRB, and ordinary steel braces, respectively. Strengthening of the structure by buckling restrained braces and ordinary steel braces both decrease the original building displacement by more than 50% from the first to the fourth floor. Under severe earthquakes, the use of BRB reduced the column shear by 46.6%; similarly, the incorporation of ordinary steel braces reduced the column shear by 4.72%. It is concluded that using buckling restrained braces will increase the vertical stiffness of the structure to a very high extent.

Pushover analysis of structures subjected to combined actions of earthquake and wind

This paper puts forward a framework to investigate the structural performance of buildings subject to the combined action of earthquakes and wind. The study uses a pushover analysis to determine strength capacities of low- and medium-rise concrete structures to compare versus their strength, as inferred from the Chinese code for seismic design. The analysis addresses soil-structure interactions through the scrutiny of fixed-base and flexible-base conditions of three soil types ranging between dense and soft. The parametric study covers micro meteorological winds whose mean value spans between 0.5 m/s and 20 m/s. The simulated multi-load scenarios induce ductility levels going from 1 to 6 to totalise 288 case studies. The proposed framework reveals that consideration of earthquake and wind simultaneous effects could modify performance levels used for design through enhancing ductility demands. This evidences that, under current design recommendations, structures located in earthquake prone areas susceptible to unexpected levels of damage.