Development of constitutive model for precast prestressed concrete segmental columns

The interest of using precast segmental columns in construction of concrete bridges has significantly increased in recent years. One research area of concrete bridges is the application of Precast Prestressed Concrete Segmental (PPCS) Column in any structural analysis software or FE program code. Modeling a PPCS column, which consists of various materials with interaction between them, is complicated and time-consuming. This research attempts to formulate the stiffness matrix of PPCS columns in order to form the constitutive model in linear form to evaluate the response of the columns. A two-dimensional finite element model is presented in the finite element package ANSYS. Parametric studies are conducted by finite element models to verify the constitutive models for the PPCS column with a different number of concrete segments. Comparison between the constitutive model and the FE program results indicates that the constitutive model is accurate enough to predict the deformation of the PPCS columns

The Effect of Smart Buildings on the Work Efficiency among Office Employees

According to researches conducted in the field of industrial psychology, the physical conditions of a work environment highly affect the mental health of employees. Therefore, the appropriate physical conditions in the work environment will lead to improved productivity and enhanced quality in employees' work. Since providing appropriate physical conditions need to spend a lot of energy and fuel, thus the use of technology in order to save energy consumption is of great importance. Among the applications of modern technologies in the field of energy consumption management, smartization of buildings can be mentioned. Smartization of buildings or use of building management systems (BMS), by commanding different components of a building to do their functions in optimum conditions, reduces unwanted consumptions while providing a pleasant and safe environment. To answer this question that how smart office buildings affect the performance and efficiency of its staff, this article deals with investigating and introducing the physical features and indicators of a suitable work environment. Then, the performance of each component of smart buildings in creating the physical comfort of the environment is introduced

Utilizing Ultra-High Performance Concrete Overlay for Road Pavement Repair and Strengthening Applications

This study aims to develop a new thixotropic ultra-high-performance concrete (UHPC) overlay for the repair and strengthening of damaged hot mix asphalt (HMA) pavements. The overlay is purposely designed to accommodate the roadway slope of up to 10% due to presence of viscosifying agent materials. The original UHPC materials are comprised of granite aggregate, ultra-fine calcium carbonate, shrinkage-reducing admixture, viscosifying agent, and expansive agent. The study is conducted with three sets of samples provided and considers thixotropic and mitigated shrinkage properties through comparing control (non-thixotropic) overlay 1 (thixotropic), and overlay 2 (thixotropic) mixtures. Based on the obtained results, only overlay 1 corresponds to the minimum requirement for pavement rehabilitation, with 160-200 mm flowability and -545.3 µm/m free shrinkage. As a result, an average 50 mm thick overlay 1 is selected to repair a damaged HMA pavement (1800 m2), while the field implementation procedures and drawing details are also presented in this paper

Simplified damage plasticity model for concrete

The past several years have witnessed an increase in research on the nonlinear analysis of the structures made from reinforced concrete. Several mathematical models were created to analyze the behavior of concrete and the reinforcements. Factors including inelasticity, time dependence, cracking and the interactive effects between reinforcement and concrete were considered. The crushing of the concrete in compression and the cracking of the concrete in tension are the two common failure modes of concrete. Material models were introduced for analyzing the behavior of unconfined concrete, and a possible constitutive model was the concrete damage plasticity (CDP) model. Due to the complexity of the CDP theory, the procedure was simplified and a simplified concrete damage plasticity (SCDP) model was developed in this paper. The SCDP model was further characterized in tabular forms to simulate the behavior of unconfined concrete. The parameters of the concrete damage plasticity model, including a damage parameter, strain hardening/softening rules, and certain other elements, were presented through the tables shown in the paper for concrete grades B20, B30, B40 and B50. All the aspects were discussed in relation to the effective application of a finite element method in the analysis. Finally, a simply supported prestressed beam was analyzed with respect to four different concrete grades through the finite element program. The results showed that the proposed model had good correlation with prior arts and empirical formulations

Seismic behaviour of prestressed and normal reinforcement of communication tower with ultra-high performance concrete, high strength concrete and normal concrete materials

Nowadays, advances in telecommunications and broadcasting have led to the implementation of communication towers for installing network equipment. These towers are designed to go as high as possible in order to cover large area and avoid obstructions. However, there exist many challenges faced by engineers in relation to design of the tall and slender structures such as the complexity configuration of the structure. The nonlinear dynamic analysis is the only method that describes the actual behaviour of a structure during earthquake. Therefore, this study aims to investigate the behaviour of ultra-high performance concrete (UHPFC), high-strength concrete (HSC) and normal concrete communication tower with 30 m height located in Malaysia under seismic excitation. Also, to provide strength, stiffness and stability for the slender structures due to their sensitivity to dynamic load such as earthquake and vibration forces. For this propose, the finite element model of the tower is developed and time history analysis of communication tower under seismic load was conducted. In addition, the effect of using prestress instead of conventional reinforcement was investigated. The result indicated that prestressing of tower had lesser effect on the lateral displacement of tower under earthquake excitation. Although, the tower with UHPFC and HSC material shows lower lateral peak displacement against earthquake load compared to the normal concrete, which led to the increase in the use of these materials in lateral stiffness of the tower structure

Analytical model for partially prestressed concrete beam-column elements

Nowadays, the demand for buildings and bridges with long span and light weight capable of withstanding any type of dynamic loading is increasing. The application of partially prestressing technique to reduce the yielding and damages in concrete members and structures offers an alternative solution to conventional reinforced concrete (RC) or fully prestressed concrete (FPC) approaches. Although partially prestressed concrete (PPC) has been widely used as a simple and economical construction technique for structures with medium to large span, there are no proper analytical and numerical models and detailed building code provisions for PPC elements. Besides, based on an extensive review of the literature, there is less information available about the possibility of identifying the damage in partially prestressed concrete beams and frame structures during earthquake excitation. Hence, in this study a new analytical model for PPC frame elements subjected to static and dynamic loads is developed. For this purpose, constitutive law and mathematical model for the three dimensional PPC beam-column element are formulated and a special finite element algorithm is developed. In order to develop three-dimensional nonlinear finite element formulations, the PPC frame element is represented by two nodes and an elastic element in between to reflect the elastic behavior of the member and two plastic hinges at each end of the member to reflect the inelastic behavior of the member. The elastic stiffness matrix of a three- dimensional PPC beam-column element with two nodes was developed during the present study; meanwhile, the elasto-plastic stiffness matrix of the three-dimensional PPC frame element having plastic hinges at both ends was derived using plasticity theory. Therefore, in order to detect the damages and determine the location of plastic hinges during dynamic loading in element, formulation for plasticity and yielding surface mechanism of PPC frame element is derived. A third degree polynomial using regression analysis was fitted to the results obtained from PPC section analysis to represent the mathematical model of the yield surface for each section. The developed analytical model and plasticity theory were codified and implemented in a special finite element program named ARCS3D in order to perform inelastic static and dynamic analysis for PPC structures. In order to validate the developed analytical model, plasticity formulation and the developed FE computer program code, five conventional RC and PPC beams and frames were fabricated and tested experimentally for cyclic load using dynamic actuator. The results showed a good correlation between the numerical analysis and the experimental tests. Several parametric studies were also undertaken for low-rise, medium-rise, and high-rise partially prestressed concrete framed buildings subjected to 2D nonlinear pushover and time history analysis. Furthermore, nonlinear pushover analysis was conducted on three-dimensional four-story RC and PPC buildings. Also, 3D nonlinear dynamic time history analysis was performed on the four-story RC and PPC frame buildings subjected to multi-directional EL-Centro earthquake accelerations. The functionality and effects of PPC buildings were then interpreted from different perspectives, such as variation of displacements, peak accelerations and plastic hinge formation. The results of numerical and experimental models indicated that application of the partially prestressed concrete members in structural systems effectively increased the strength and safety of the structure during dynamic loading. Also, the developed FEM program was able to successfully identify damage occurrence in PPC structural element during applied dynamic loads. To be more specific, a comparison between results shown that the ultimate capacity, degree of flexibility and energy dissipation capacity of the PPC beam specimens improved up to 70 %, 93 % and 300 % compared to the conventional RC beam specimen. From the experimental PPC frame results, the lateral load capacity and stiffness improved up to 34 % and 17 % compared to the RC frame. Also, no crack happened in the beam of the PPC frame under super imposed dead load. Furthermore, based on the parametric studies, application of PPC members in multi-storey concrete buildings subjected to seismic loads indicated a noticeable delay in the failure process, however, conventional RC buildings collapsed at the first stage of analysis. Ultimately, this study facilitates the analysis and design procedures of the multi-story PPC and RC buildings as well as bridges in an efficient computation time which is more economical compared to normal design methods

Plasticity model for partially prestressed concrete

Recently, the partially prestressed concrete (PPC) has been widely used as an effective construction technique for structures to reduce yielding and damages. However, there is no proper analytical model for PPC frame elements (beam-column members) to perform the finite element analysis. Besides, an extensive review of the literature uncovered little available information about the possibility of identifying damage to PPC members during applied vibration loads such as earthquake excitation. Hence, this paper presents the development of a new 3D analytical model for PPC beam-column element subjected to static and dynamic loads. In addition, a theory of plasticity and yielding surfaces for PPC frame elements are formulated in order to detect damage and determine the location of plastic hinges in the structural components under dynamic load. The developed analytical and plasticity models were codified and implemented in a finite element program in order to perform inelastic static and dynamic analysis for PPC structures. Then, sample PPC beam and frame members were cast and tested experimentally for flexural and incremental loading, respectively, to verify the developed analytical and plasticity model for PPC. The results show a good agreement between the analytical model and numerical analysis and the experimental test results. In addition, a comparison of the seismic response of reinforced concrete (RC) and PPC structures indicated that the stiffness and energy dissipation capacity of the structure with PPC members improved noticeably and the total number of plastic hinge formations in the structural members decreased