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Many displacement-based quadrilateral plate elements based on Mindlin-Reissner plate theory have been proposed to analyze the thin and moderately thick plate problems. However, numerical inaccuracies of some elements appear since the presence of shear locking and spurious zero energy modes for thin plate problems. To overcome these shortcomings, we employ the large increment method (LIM) for the analyses of the plate bending problems, and propose a force-based 8-node quadrilateral plate (8NQP) element which is based on Mindlin-Reissner plate theory and has no extra spurious zero energy mode. Several benchmark plate bending problems are presented to illustrate the accuracy and convergence of the plate element by comparing with the analytical solutions and displacement-based plate elements. The results show that the 8-node plate element produces fast convergence and accurate stress distributions in both the moderately thick and thin plate bending problems. The plate element is insensitive to mesh distortion and it can avoid the shear locking for thin plate analysis. [ABSTRACT FROM AUTHOR]

Local damages to a structure will cause disproportional collapse if the system is lack of robustness. This structural safety cannot be guaranteed by traditional ways, such as reliability analysis tools and construction management approaches. Therefore, it is very important to develop related theories for structural robustness. This paper presents a methodology to quantitatively assess the structural robustness from the topological point of view. In the proposed method, the structural failure is viewed as a feedback process. The transformations between the damage input and failure output form a closed-loop. The decisive factor of the operation of such a closed-loop is thought as the structural topology. Furthermore, the damage input and the failure output of the structure are measured by the uncertain disturbance and the change of the topology, respectively. After the sensitivity of the structural topology to the uncertain disturbance is studied, the transfer matrix is discovered to indicate the rationality of the topological relationship. The importance of each loading path, the structural robustness and the most vulnerable part of the system can be found concisely in accordance with this matrix. [ABSTRACT FROM AUTHOR]

Since 1960s, many research works on the reinforced concrete structure have been published and some concise and practical calculation methods for safety control during construction have been achieved. The reinforced concrete structure during construction is a time-dependent structure which consists of a partly completed structure and a formwork-shore system. Experience shows that the most critical condition of the time-dependent structure may happen when the formwork-shore system is partly removed or reset and accidents may occur. In the present paper, effect of ambient temperature variation between day and night is considered, new structural models for reinforced concrete frames, slab-column systems and shear wall structures are proposed, and a new software named Safety Analysis During Construction Considering Temperature (SACT) is also introduced. Compared with on-site measurements, the software SACT is validated for application on construction site. [ABSTRACT FROM AUTHOR]

The ultimate strength of reinforced concrete (RC) rectangular members subjected to combined bending, shear and torsion is obtained from the limit analysis proposed in the present paper. Based on a warped failure surface determined by external loads, and a reasonable assumed stress distribution balancing external loads but not violating the yield condition, the bending-shear-torsion interaction can be derived from equilibrium conditions. According to the definition of lower-bound theorem in limit analysis, the calculated ultimate loads will be carried safely by the structure. The present method is a simple approach to obtain carrying capacities for RC elements under complex external loads. After comparing with the test results, a good agreement has been observed. The present method can be extended to explain the failure mechanism of RC members subjected to axial loads, and it is possible to develop a simple unified theory of RC members for engineering. [ABSTRACT FROM AUTHOR]

Based on the traditional Nielsen model, a unified failure model on the uniformly reinforced concrete box section members under combined forces was introduced by Luo and Liu. One of their contributions is adjustment of the shear carrying capacity of concrete at the member failure surface. In the unified failure model, the comparison with the experimental results verified this adjustment. Nevertheless, it should be pointed out that the adjustment factor of shear carrying capacity at member failure surface for the reinforced concrete members in the unified failure model is a fixed adjustment constant for all experiment data, which is basically determined by curve fitting. However, the adjustment factor should vary with the normal stress at the member failure surface. In this paper, an advanced theoretical model is introduced, in which the adjustment factor of shear carrying capacity at failure surface is a variable related to the normal stress at failure surface. Furthermore, the advanced unified failure model on the uniformly reinforced concrete box section member can still be expressed in a simple form. Finally, the comparison with several groups of test data has verified that this advanced model is more accurate and feasible to be used in design. [ABSTRACT FROM AUTHOR]

A new model is proposed by an assumption of quartic polynomial function to simulate the relative slip of steel bar and surrounding concrete in RC tensile member. In the new model, the postcracking behavior with a tension-stiffening effect is considered. Through the extension of the new model, the relative slip of the perfectly bonded interface of RC bending member can also be determined, based on which an interpolating function can be introduced to study the relative slips under different bending moments for corroded RC bending members. Finally, two experimental results of corroded RC beams under four-point bending are used to verify the new models. [ABSTRACT FROM AUTHOR]

Structural robustness is the concept to evaluate whether local damages to the structure will cause disproportional consequences. It is one of the most important indexes to keep the structural safety, especially to consider a special loading named as 'human active damage'. In the present paper, the loaded structure is analyzed by a weighted graph. The joints and members of the structure correspond to the vertexes and edges of the graph, and the ratio of the most dangerous stress state to the material strength of each member is treated as the weight of each edge. Based on the quantitative description of the structural topology, the structure graph is expressed as a hierarchical model which is built by a set of vertex-connected units. The local damage can be expressed as the deterioration of the unit(s), while the final possible failure mode of the structure can be obtained by a specific assignment of its weighted graph. In this way, the relationship between the structural behavior and the combined damages of the subordinate units in each hierarchy can be formed as an envelope diagram. This diagram exactly shows the contribution of each subordinate unit to the robustness of the whole structure. Furthermore, the most vulnerable part, as well as the topologic difference between the subordinates, can be found visually. [ABSTRACT FROM AUTHOR]

As a force-based finite element method (FEM), large increment method (LIM) has been developed in recent years. It has been shown that LIM provided prominent advantage of parallel computation with high efficiency and low time consumption for member structural system. To fully utilize its advantage in parallel computation, it is the time to extend LIM to 2D and 3D continua analysis. In this paper, a 2D finite element library with the capability of modeling arbitrary configurations is developed. Some illustrative numerical examples are solved by using the proposed library; the obtained results are compared with those obtained from both traditional displacement-based FEM and analytical solutions, which has clearly shown the advantages of LIM. [ABSTRACT FROM AUTHOR]

It is urgently needed to describe the structural collapse process under extreme conditions to survive people. For reinforced concrete structures it is still a difficulty to describe the failure of reinforced concrete members under complex internal force combination, such as under axial forces, bending moment, shear forces, and torsion working together. In this paper, based on the traditional Nielsen model, a new unified failure model on reinforcement evenly distributed concrete members with box section under combined forces is introduced. The advantages of the proposed new model are to consider the dowel actions of reinforcements and reasonably to consider of the shear carrying capacity of concrete, especially when compression stress of concrete is in a high value. Finally, the theoretical results of the new model are compared with a series of experimental results of box section members. The comparison has verified that the new model is more accurate and feasible for the design and calculation of box section members. [ABSTRACT FROM AUTHOR]

The effects of length and location of the steel corrosion on the structural behavior and load capacity of reinforced concrete (RC) columns have been investigated. Results of the accelerated corrosion process and eccentric load test are presented in detail. Effects of the location of the partial length, the corrosion level within partial length and the asymmetrical deterioration of the concrete section on the mechanical behavior and load capacity of corroded RC columns are discussed. It is found that the mechanical behavior and load carrying capacity of corroded RC columns are simultaneously affected by the above mentioned factors. For the corroded RC columns with large eccentricity, a higher corrosion level in the tensile corroded length and a greater asymmetrical deterioration of the concrete section can result in less ductile behavior and larger load reduction of the column; while for the corroded RC columns with small eccentricity, the less ductile behavior and the larger load reduction of the column may result from the higher corrosion level in the compressive corroded length and the greater asymmetrical deterioration of the concrete section. [ABSTRACT FROM AUTHOR]

This paper investigates new damage detection method for bridges to ensure their safety. The idea of using displacement data of two symmetrical points for multiple damage detection is presented for the first time. After introducing the concept of Equivalent Element, a novel index termed as 'Symmetrical Displacement Difference Index (SDDI),' is proposed. The displacement under static load is used for constructing the new index. Then the relationship between the local flexural stiffness change caused by damage and SDDI value is generated. In application, SDDI values can be plotted after the measurement of displacement. The relative changes between the intact state and the damage state in the curve shapes can be used to indicate the position of damage. This new damage detection method based on SDDI is flexible enough to be applied to real-world bridges with inherent random uncertainty and actual support condition. Numerical and experimental examples have been conducted to examine the suitability of the method. This paper provides a simple, convenient, cost-effective, and nondestructive damage detection method for bridges. [ABSTRACT FROM AUTHOR]

Experimental study on shear behaviour of reinforced concrete (RC) beams with corrosion damaged partial length in one shear span is presented. In order to discover how mechanical behaviour and load capacity of the RC beam were influenced by the corrosion damaged partial length, 14 RC beams including two noncorroded RC beams, four RC beams with partially unbonded length and eight RC beams with partially corroded length were designed. The different shear span-to-effective depth ratios, the different designed partial lengths located in one shear span and the different corrosion levels within the designed partial lengths were the main considered parameters. Test results are presented in detail. Due to the different bond conditions as well as different damage status in the longitudinal bars and the contacted stirrups, the structural performance, ductility, load capacity of the test specimens with partially unbonded and corroded length are quite different. Due to the severe pitting corrosion of the longitudinal bars and rupture of the contacted stirrups within partial length of one shear span, reduced load capacity, stiffness and ductility are shown in beam with higher corrosion level within longer partial length. [ABSTRACT FROM AUTHOR]

The localization of damage for bridges to ensure their safety is investigated in this paper. Equivalent element concept is introduced into this study at the beginning. Support reaction data of each bearing under truck load are found to be able to lend themselves to indicate damage. A novel index termed as symmetrical support reaction difference index (SSRDI) is then developed. The reverse mapping between the local flexural stiffness change induced by damage and the SSRDI is generated. The proposed method based on SSRDI can be sensitive to tiny damages, and comparatively simple measurements are required during the application procedure. Another significant attraction of this method is that it can work in the presence of random uncertainties and actual support condition, which means it is suitable for real-world bridges. The effectiveness of the proposed method is demonstrated by numerical simulations performed on two kinds of bridges with reasonable damage severities. Its comparative advantage over the previous frequency method is also investigated. [ABSTRACT FROM AUTHOR]

This study presents a new idea of using only mid-span displacement measurement for damage detection of simply supported beams. Equivalent element concept is introduced at the beginning. In order to relate the damage detectability by means of mid-span displacement measurement with the damage-caused local stiffness change, a novel index termed as symmetrical mid-span displacement difference index (SMDDI) is proposed. The proposed method based on SMDDI is sensitive to tiny damage and comparatively small quantities of measurements are required during the application process. Another significant attraction of this method is putting aside the knowledge a-priori of the intact state. An example using simulated data has been conducted to examine the suitability of this method and assess its comparative advantages over the previous modal method. [ABSTRACT FROM AUTHOR]

The numerous construction projects in China provide the best environment for the development of information technology applied in building design. Various commercial CAD/CAE software applications are purchased by design firms for multi-disciplinary design tasks. However, researches on integration and interoperability are seldom considered. This study pursues a breakthrough point of integration in the architectural and structural domains and expects further development in other aspects. A central building information modeling (BIM) framework based on the industry foundation classes (IFC) is proposed to handle the data exchange between IFC-compatible architectural models and structural models. A central XML(extensible markup language)-based unified finite element model (FEM) is proposed for model conversion among various commercial structural CAE software applications. In addition to bidirectional data interfaces among IFC-based BIM, XML-based FEM and various commercial FEMs, some other components such as visualization, calculation and model editing/check are also equipped into the prototype system. [ABSTRACT FROM AUTHOR]

Steel corrosion in reinforced concrete (RC) structures leads to change of steel mechanical properties, longitudinal cracking in the concrete cover, and other related effects that weaken the serviceability and load capacity of the composites. It is therefore extremely important to have methods targeted to the evaluation of the structural damage induced by corrosion for estimating the residual load capacity of a structure, and then for inspection procedures and strengthening the maintenance interventions. This paper presents a simplified methodology capable of providing estimates of the residual life of corroded RC beams. The proposed method uses damaged material properties, and accounts for the length of partial corrosion and the amount of corrosion, concrete loss and change of bond strength within this specified length. A comparison of the model predictions with the experimental results published in the literature shows the validity of the model. It is also concluded that the ultimate flexural moment of corroded RC beam will not significantly influenced by the partially corroded or unbonded length and the bond characteristics over this partial length as long as the tensile steel of the beam can reach its yield strength. In addition, although complete loss of bond over the partial length is assumed to asses the residual strength of corrosion-damaged RC beam, neglecting the influence of bond strength within the corroded length may lead to underestimate the ultimate flexural capacity of the damaged beam, especially when the corrosion level of tensile steel of the RC beam is not very high. [ABSTRACT FROM AUTHOR]

Structural collapse under blast loads is a very complex process. For several decades, the engineering profession has considered some approaches to analyze the essential physics of collapse phenomena. Recently, the interest in this topic has risen to an apex since the collapse of the World Trade Center towers. A two-step analysis approach to capture the characteristics of structural collapse during explosions is proposed. A numerical example is presented to illustrate the performance of the presented approach. [ABSTRACT FROM AUTHOR]

A numerical model using the coupled smoothed particle hydrodynamics-finite element method (SPH-FEM) approach is presented for analysis of structures under blast loads. The analyses on two numerical cases, one for free field explosive and the other for structural response under blast loads, are performed to model the whole processes from the propagation of the pressure wave to the response of structures. Based on the simulation, it is concluded that this model can be used for reasonably accurate explosive analysis of structures. The resulting information would be valuable for protecting structures under blast loads. [ABSTRACT FROM AUTHOR]

Considering the change of bond strength between corroded steel and concrete, flexural carrying capacity of corroded reinforced concrete (RC) beam was calculated. On the basis of the condition of equilibrium of forces and compatibility of deformations for the whole beam, a model for the prediction of flexural carrying capacity of the corroded RC beam was proposed. Comparison of the model’s predictions with the experimental results published in the literature shows the practicality of the proposed method. [ABSTRACT FROM AUTHOR]

Reinforced concrete structural elements with box section are commonly used in the horizontal and vertical structure of bridges. The reinforced concrete structure in bridge often failed under the combined forces of bending, axial load, shear and torsion caused by wind and earthquake. It is very important to study the mechanism of RC box section structures subjected to a combination of forces. A theoretical study and deduction of the unified expression for failure of reinforced concrete members with box section under combined bending, shear, axial force and torsion were carried out with stress equilibrium assumption. Comparison of theoretical analysis results with experimental results showed that the unified expression for failure of reinforced concrete members with box section can be used for static calculation of such structure members. [ABSTRACT FROM AUTHOR]