Steel-concrete Structures Research Articles

Evaluating the Fragility Curve in Steel–Concrete Structure Undergoing Seismic Progressive Collapse by Finite Element Method

Evaluating the Fragility Curve in Steel–Concrete Structure Undergoing Seismic Progressive Collapse by Finite Element Method

Novel Nano-Precursor Inhibiting Material for Improving Chloride Penetration Resistance of Concrete: Evaluation and Mechanism.

Durability improvement is always important for steel–concrete structures exposed to chloride salt environment. The present research investigated the influence of a novel nano-precursor inhibiting material (NPI), organic carboxylic acid ammonium salt, on the mechanical and transport properties of concrete. The NPI caused a slight reduction in the strength of concrete at later ages. NPI significantly decreased water absorption and slowed down the speed of water absorption of concrete. In addition, the NPI decreased the charge passed and the chloride migration coefficient, and the results of the natural chloride diffusion showed that the NPI decreased the chloride concentration and the chloride diffusion coefficient. The NPI effectively improved the resistance of chloride penetration into testing concrete. The improvement in the impermeability of concrete was ascribed to the incorporation with the NPI, which resulted in increasing the contact angle of cement pastes. The contact angle went up from 17.8° to 85.8° for 0% and 1.2% NPI, respectively, and cement pastes became less hydrophilic. Some small pore throats were unconnected. Besides, the NPI also optimized the pore size distribution of hardened cement paste.

JUSTIFICATION AND CHOOSING OF RATIONAL CONSTRUCTIVE CROSSSECTIONS, POSSIBILITIES OF USING IN DIFFERENT CONSTRUCTION DIRECTIONS

The development of modern construction is closely related to the efficient use problemof building materials in terms of rational use materials’ strength properties. The search of rationalstructure in terms of geometric parameters, the materials use and providing the same bearingcapacity is important question in the modern building. The purpose of article is to carry out acomparative analysis of the geometric and strength characteristics of different reinforced concretecross-sections, and consideration of existing methods for calculating the bearing capacity andassessment of the stress-strain state of reinforced concrete beams.The steel-concrete structures using in different building structures is paid much attention in theworld practice. The steel-concrete structures widespread using leads to the economy of materials,reducing the complexity of manufacture, reducing time erection. The using of reinforced concreteleads to significant economy of steel, and set the new tasks for the engineers in the same time: ownweight and geometric parameters reducing of the cross-section without reducing of bearing capacityin whole. With the search for new structures that would meet the building requirements and usage ofdifferent building, nowadays significant attention pays to the improvement and development of thesteel-concrete elements. During the development and improvement of steel-concrete structures,significant changes have been made in terms of ensuring the joint operation of reinforced concreteand steel. Such structures require constant research and improvement in order to reduce their ownweight, financial costs, etc. The question of finding a rational structure in terms of geometricparameters, the materials using, as well as ensuring the same bearing capacity is currently important

Experimental investigation on shear performance of transverse angle shear connectors

To overcome the concrete casting obstruction of the bottom slabs in prestressed concrete box-girders with corrugated steel webs (CSWs), transverse angle shear connectors were adopted in some cases. The overall behavior of such steel–concrete structures highly depended on the shear behavior of the connectors. Seven large-scale push-out specimens, with different height and spacing of shear connectors, were tested to examine the shear performance of transverse angle shear connectors. The failure modes, load-slip relationships, ultimate shear strengths, initial stiffness and ductility of specimens were explored. Based on the experimental results, this study suggests that both of the connector height and spacing impacted the shear strength of transverse angle connectors. The initial stiffness of specimens improved with the increasing of both connector height and number. The ductile characteristic can also be observed in the load-slip relationship. Compared with traditional longitudinal PBL shear connector, the transverse angle shear connectors also showed apparent strength enhancement and acceptable ductile characteristic. The equation for angle shear connectors suggested in Eurocode 4 can be used for predicting the shear strength of transverse angle shear connectors with spacing ranged from 350 mm to 450 mm.

Evolutionary Topology Optimization of Spatial Steel-Concrete Structures

Topology optimization techniques based on finite element analysis have been widely used in many fields, but most of the research and applications are based on single-material structures. Extended from the bi-directional evolutionary structural optimization (BESO) method, a new topology optimization technique for 3D structures made of multiple materials is presented in this paper. According to the sum of each element's principal stresses in the design domain, a material more suitable for this element would be assigned. Numerical examples of a steel- concrete cantilever, two different bridges and four floor systems are provided to demonstrate the effectiveness and practical value of the proposed method for the conceptual design of composite structures made of steel and concrete.

Thermal Behavior and Stress Response of Steel-concrete Structures under Solar Radiation

Steel-concrete structures are widely used because of their large space and strong plasticity, but the long construction period, complex splicing process and other factors will make the main body of the structure directly exposed to solar radiation, resulting in temperature changes on the surface of steel structure and concrete structure. In order to obtain the stress changes of steel-concrete structures under solar radiation, two kinds of steel-concrete structures with different support forms were simulated. Under three temperature gradients, the thermal behavior and mechanical properties of two kinds of steel-concrete structures composed of upper steel roof and lower concrete support were analyzed. The results show that there is a linear relationship between the thermal behavior and stress response of steel-concrete structure and the daily temperature difference caused by solar radiation. Under the action of thermal effect, the stress difference between the lower steel frame of the full support structure and the lower steel frame of the support structure on both sides is about 10.7%.

Structural system selection and design of Zhangzhou Opera House Fujian Province

Zhangzhou Opera House adopts the complex structure system of petal shape. According to the building shape and architectural layout, the structure combines the steel truss for large-span space and the frame-shear wall structure surrounding. This article introduced its structural system, multi-line defense line arrangement and anti-seismic performance objectives, and summarized the structural characteristics of the overall structure, especially focusing on key issues such as setting the ring floor beam to resist the extroversive forces, anti-seismic performance of key components and the design of the junction between the steel truss and concrete structure. The results show that the structure has strong adaptability to the building shape with suitable seismic performance, and fulfilling both the requirements of seismic performance design and the structural safety.

Advanced computer model for analysis of reinforced concrete and composite structures at elevated temperatures

abstract: This paper is concerned on the development of a computational model based on finite element procedures for advanced analysis capable of estimating the behavior of reinforced concrete and composite steel-concrete plane structures exposed to fire. The program implemented is called NASEN, the specific thermo-structural module is used to analyze structures under fire conditions. The effects of geometric nonlinearity, material nonlinearity and nonlinear thermal gradients are incorporated into the model, as well as the degradation of material properties with increased temperature. The methodology applied for the solution is based on the unidirectional coupling of the thermal and mechanical solutions. The cross-sections of the structural elements are discretized with two-dimensional meshes for thermal analysis, while the structural analysis uses a one-dimensional beam-column element. Numerical examples are presented to demonstrate the accuracy of the computational code developed in relation to the numerical and experimental solutions found in the literature. In summary, the program adequately predicted the response of the studied structures.

Fire resistance of lightweight steel-concrete slab panels under high-temperature exposure

Lightweight steel concrete structures (LSCS) - an innovative energy-efficient building structure type that can be used both as load-bearing and as enclosing one. They consist of profiled steel - usually galvanized and cold-bent - filled with a monolithic foam concrete with a 400kg/m3 density and with fiber cement sheets sheathing. These structures can be used in industrial and civil buildings as internal and external bearing and enclosing wall structures and as slabs, energy-efficient roof covering. According to the LSCS production method, prefabricated panels (walls and slabs) and building site performed constructions are distinguished. The paper presents the testing results with the aim to determine the fire resistance limit of a slab panel fragment by bearing capacity (R), loss of integrity (E), loss of heat insulating capability (I) and fire hazard class. Two samples of a slab panel fragment were selected for the fire resistance high-temperature tests. The actual fire resistance limit of samples of the slab panel fragment is at least REI 60 with a uniformly distributed load 4 kN/m2.

Combustibility of lightweight foam concrete based on natural protein foaming agent

There is an experimental study of samples of monolithic foam concrete “SOVBI” with a density of 205 kg /m3(grade D200) for combustibility. The evaluation criteria are the following values of combustion characteristics: temperature increment in the furnace, duration of the stable flame burning, sample mass loss. The experimental results show the following values for foam concrete: temperature increment in the furnace of 2 °C, duration of the stable flame burning of 0 s, and sample mass of 24.4%. Thus, monolithic foam concrete with a density of 205 kg/m3is noncombustible material. It is proposed to use monolithic foam concrete and other lightweight monolithic cellular foam concrete, as a structural fire protection for lightweight steel concrete structures. It, in turn, can increase the fire resistance of external walls and floor structure with the steel frame of cold-formed zinc-coated profiles.

Behavior of composite beams with external prestressing in sagging moment regions

Abstract Prestressed composite steel-concrete structures are scarcely used due to a lack of clear standardized design guidelines and formulations on the subject. The present research aims to present design methodologies for steel-concrete composite beams with external pretension applied via straight tendons. A computer program to perform structural analysis of such beams was developed based on two different methodologies: the first one is presented in ABNT NBR 8800:2008, in which the guidelines for the design of composite beams with compact webs are adjusted to include the effects of the pretension force. The second methodology is extracted from international literature and presents a structural design process based on stress distribution on the beam. Ninety prestressed and thirty non-prestressed beams were analyzed and designed with the aforementioned computer program to evaluate the influence of beam length, degree of symmetry of the steel profile and eccentricity of the pretension force on the mechanical resistance of the beams. It was observed that, although the prestressing force considerably improved resistance to bending, it introduced high compression stresses on the steel profile; hence, the pre-stressing of composite beams is proved efficient only for steel profiles with symmetrical cross-sections.

Comparison of Composite, Steel and Reinforced Concrete Columns

Architects now often require the use of slender load-bearing structures, but they must be sufficiently resistant to all loads. The use of the composite steel-concrete columns joins the main advantages of the individual materials. The most commonly used composite is the steel-concrete. Depending on the amount, shape, location and utilization rate of the steel or concrete, the composite columns are closer to the steel or reinforced concrete columns. The composite steel-concrete structures utilize high compressive strength of concrete and high tensile resistance of the structural steel. The steel-concrete connection is therefore highly efficient, and by combining, it is possible to produce relatively lightweight structures with wide use in high-rise buildings and bridges. The composite steel-concrete columns have high strength with a relatively small cross-sectional area. Composite efficiency also depends on the type of composite steel-concrete column. The most commonly used type is a steel tube filled with concrete. In the case of a steel tube filled with concrete, it is possible to use the confining effect of a steel tube, which prevents lateral deformation of the concrete and at the same time, the concrete core prevents compression of the steel tube. These two effects increase the total resistance of the composite steel-concrete column. Other types are partially or fully concrete-encased steel section. The use of a fully concrete-encased steel cross-section increases the fire resistance of the cross-section as the steel profile is protected by concrete against the effects of fire. The criterion for selecting the appropriate shape and type of the steel part of the column cross-section, the design of the global structural system of the object should be taken into account. Not only one European standard is needed to design composite steel-concrete structures. In addition to the standard EN 1994-1-1 Design of composite steel and concrete structures, it is also necessary to use standards EN 1992-1-1 Design of concrete structures and EN 1993-1-1 Design of steel structures.

Investigation on Moisture Damage Prevention of a Spherical Hinge Structure of a Swivel Bridge

As a key component of a swivel bridge, the spherical hinge is a steel-concrete structure, which is susceptible to moisture damage during waiting time. In this paper, spherical hinge moisture damage prevention is investigated comprehensively from two aspects of impermeable concrete and steel-concrete interface waterproof coating. Three impermeable concretes were prepared and tested by the compressive strength test, splitting tensile test, four-point bending test and the impermeability test. The test results illustrated that addition of cementitious capillary crystalline active masterbatch (CCCAM) and polypropylene fiber (PP) could improve the toughness and brittleness of concrete. The addition of CCCAM was an effective technique for improving the permeability of concrete. However, the incorporation of PP and CCCAM at the same time cannot improve the impermeability of concrete. This may be because the chaotic support structure formed by PP prevents the infiltration and uniform dispersion of CCCAM. A waterproof coating consolidation performance test was proposed to quantify the interface bond strength of waterproof coatings and assess the impact of temperature, moisture and freeze-thawing cycles on consolidation performance of waterproof coatings. The test results showed that temperature had a significant effect on the interface consolidation property of waterproof coatings and the optimal dosage of SBS modified asphalt (SBS), polyurethane (PLT) and unsaturated polyester resin (UPLS) waterproof coating is 1.18kg/m2, 0.95kg/m2 and 1.15kg/m2, respectively. Moreover, it was found that PLS waterproof coating maintained excellent properties in complex environment. This is because PLS has excellent shear strength and rubber characteristics, and it can form a hard–soft–hard transition layer between the concrete and steel, reducing the impact of environmental factors.

Experimental evaluation of the shear capacity of perfobond strips with steel fiber-reinforced mortar in narrow joint structures

Appropriate transfer of the shear force of a perfobond strip used as a shear connector in steel concrete hybrid structures depends on the restraining effect around the strip, and hence, the arrangement of the surrounding reinforcements is very important to improve the restraining effect. However, when the perfobond strip is arranged in narrow joint structures and when the rapid construction is also required, reinforcements are undesirable on the site. An alternate method to improve the restraining effect around the perfobond strip is to use steel fiber-reinforced mortar (SFRM). This study aims to evaluate appropriately the shear capacity of a perfobond strip with SFRM without surrounding reinforcements for narrow joint structures. Assuming these conditions, pull-out tests were conducted, and the data obtained were considered along with the results of push-out tests conducted in the previous study of the authors. Based on the results of both test series, the impacts of various factors on the shear capacity of the perfobond strip was analyzed comprehensively. The results showed that the shear capacity of a perfobond strip with SFRM increases with the perforation diameter, SFRM compressive strength, volume content of steel fibers in the mortar, and dimensions of the mortar block around the perfobond strip. Moreover, the plasticization of the perfobond steel plate and the difference in boundary conditions between the push-out and pull-out tests also affect the shear capacity of the perfobond strip. An equation was proposed for evaluating the shear capacity of the perfobond strip with SFRM without any surrounding reinforcements for narrow joint structures. The shear capacity obtained using the proposed equation has high correlation with the experimental value for both push-out and pull-out specimens.

Performance of the materials used for repair of reinforced concrete structures of communication conduits

It has been considered how some branded repair compositions, the repair cement compositions containing quartz sand and mixing water treated with low-temperature non-equilibrium plasma (LTNP), and the materials for external reinforcement of steel–concrete structures have influence on the bearing strength of the restored and reinforced floor slabs simulating steel–concrete flat-slab decks of communication conduits. It has been found that the examined repair cement-based compositions restore the bearing capacity of the simulating floor slabs by 72.1–96.2%, and when tested for breakdown the restored slabs fail within the repair composition. It is shown that after external reinforcement of the restored steel–concrete floor slabs with CarbonWrap Grid 380/1000 their bearing capacity increases by more than 1.7 times.

Applications of Light Steel and Light Concrete Structure System in Island Building

Zhang, J. and Zhao, F.-G., 2020. Applications of light steel and light concrete structure system in island building. In: Qiu, Y.; Zhu, H., and Fang, X. (eds.), Current Advancements in Marine and Coastal Research for Technological and Sociological Applications. Journal of Coastal Research, Special Issue No. 107, pp. 73-76. Coconut Creek (Florida), ISSN 0749-0208.Because the island is surrounded by a high salinity and humidity marine environment, the buildings on the island will also be corroded and damaged by the marine environment. As a new type of building structure system, light steel light concrete system integrates the advantages of reinforced concrete and light steel structure, and has stronger corrosion resistance, so it is more widely used. Based on this, this paper first analyzes the technical characteristics of the light steel light concrete system, then studies the applicability of the light steel light concrete structure system in the island building, and finally gives the application analysis of the light steel light concrete structure system in the island building.

Numerical and experimental investigation of prestressed steel-concrete composite beams

Prestressing in building structures has been used for a long time. However, the prestressing of structures with a combined cross section, such as steel-concrete structures, has appeared recently. The report is devoted to the structural types of prestressed steel – concrete structures, the description of technical solutions and comparative analysis with known sources. A comparative analysis of the methods of prestressing steel – concrete beams with widespread methods of prestressing reinforced concrete and steel structures is carried out. The article is devoted to prestressed composite beams, the identification of both the stress – strain state of beams of a composite section from prestressing and from operational loads is analyzed. Analytical expressions are given for assessing the strength of prestressed steel – concrete bending elements for different methods of prestressing, and the results of numerical and full-scale tests. Comparisons of the results of numerical and field experiments in the form of graphs are given. In conclusion, satisfactory convergence of various methods for assessing the strength of prestressed beams with experimental studies is noted.

Experimental study of the behavior of prefabricated lightweight concrete shear walls with channel sections framing under axial compression

In order to satisfy requirements of fireproof and thermal insulation property of lightweight steel and lightweight concrete structures, an innovative prefabricated lightweight concrete shear wall with channel sections framing is developed. This paper focuses on axial compressive behavior of the wall. Two full-scale specimens are tested under axial compressive loads. The compressive strength of ceramsite-foamed concrete is varied to investigate their impacts on axial bearing capacity and axial compressive stiffness of the specimens. The failure modes, load-displacement curves, and deformability of the specimens are also investigated. Test results show that the failure modes of shear wall are mainly local bucking failure of channel sections framing and local crushing of ceramsite-foamed concrete plate. Compared with the specimen infilled C7-grade ceramsite-foamed concrete, the axial bearing capacity and the axial compressive stiffness of infilled C10-grade ceramsite-foamed concrete specimen are increased by 15.6% and 16.3%, respectively. Therefore, this study can provide a reference for further research on the axial compression performance of the prefabricated lightweight concrete shear walls with channel sections framing.

Carbon emission energy management analysis of LCA-Based fabricated building construction

With the gradual warming of the global climate, the development of low-carbon buildings has become an inevitable trend, and research on the carbon emissions of buildings is also imperative. At present, in most studies on energy management of carbon emissions during the construction process, people cannot analyze them with a more accurate method. In order to find an effective carbon emission analysis method, based on the life cycle assessment method (LCA), this paper establishes a carbon emission model, and calculates the carbon emission of residential building materials in different areas, building materials in different industrial buildings, air conditioning cooling and heating schemes, and the whole life cycle of buildings. This article draws the following conclusions: The relationship between the carbon emissions of residential building materials in different regions is: severe cold area>cold area>hot summer and cold winter area>mild area>hot summer and warm winter area. In the analysis of frame structure, brick concrete structure and steel concrete structure, the most carbon emission is steel concrete structure, and the least is frame structure. The carbon emissions of different forms of air-conditioning cold sources are different. Among them, the second option is the direct-fired lithium bromide absorption chiller and hot water unit. The carbon emissions are related to the energy structure. For prefabricated buildings, the proportion of carbon emissions in the construction use phase is the highest, reaching 75%–80%, and the sum of the construction use phase and the building material production phase accounts for more than 90% of the total.

Approbation of an effective method for dynamic calculation of the steel and concrete bridge span

Problem statement. The article describes the method and results of determining the dynamic response of a continuous steel-reinforced concrete span of a road bridge to the passage of heavy vehicles, which is focused on the use of finite element computing systems. The data of dynamic calculations are compared with those obtained during full-scale dynamic tests of the operated structure. Results. Modern algorithms for dynamic calculation of continuous bridge structures on the action of sprung vehicles are analyzed, which allow taking into account the irregularities on the roadway, the influence of wheel bearing point movements on the vibrations of moving vehicles. It describes the sequence of performing dynamic calculations using modal analysis blocks and dynamic calculation of KE-complexes for a system of moving non-inert loads, followed by calculating the dynamic component of deflections and forces of elements of the bridge structure, taking into account the inertia of the vehicle and unevenness on the roadway. According modal analysis of steel-concrete span structures road bridge operated by means of spatial finite element calculation schemes are determined by their own shape supporting structure, which are then used for dynamic calculations in a moving inertial load. The results of dynamic calculations of the operated road bridge on the action of a three-axle truck moving at a constant speed are presented. Calculated deflections are compared with those obtained during full-scale static tests of the bridge. Numerical calculations estimate the effect of speed, roadway irregularities, and feedback between the vibrations of the bridge and the moving vehicle. Conclusion. The proposed method of dynamic calculation of bridge structures allows evaluating the dynamic quality of transport structures at the design stage and making optimal design decisions.