Structural Cross Sections: Analysis and Design
Abstract
Structural Cross Sections: Analysis and Design provides valuable information on this key subject covering almost all aspects including theoretical formulation, practical analysis and design computations, various considerations and issues related to cross-sectional behavior, and computer applications for determination of cross-sectional response. The presented approach can handle all complex shapes, material behaviors and configurations. The book starts with a clear and rigorous overview of role of cross-sections and their behavior in overall structural design process. Basic aspects of structural mechanics are reviewed and procedures to determine basic cross-sectional properties, stress and strain distributions, stress resultants and other response parameters, are provided. A brief discussion about the role of material behavior in cross-sectional response is also included. The unified and integrated approach to determine axial-flexural capacity of cross-sections is utilized in development of P-M and M-M interaction diagrams of cross-sections of various shapes. The behavior and design of cross-sections subjected to shear and torsion is also included with emphasis on reinforced concrete sections. Several detailed flow charts are included to demonstrate the procedures used in ACI, BS and Euro codes for design of cross-section subjected to shear and torsion, followed by solved examples. The book also presents the discussion about various factors that can lead to ductile response of cross-sections, especially those made of reinforced concrete. The definition and development of action-deformation curves especially moment-curvature curve is discussed extensively. Various factors such as confinement, rebar distribution and axial load effect on the ductility are shown through examples. The use of moment-curvature curve to compute various section response parameters is also explained though equations and examples. Several typical techniques and materials for retrofitting of cross-sections of reinforced concrete beams, columns and slabs etc. are reviewed. A brief discussion of various informative references related to the evaluation and retrofitting of structures is included for practical applications. Towards the end, the book provides an overview of various software applications available for cross-section design and analysis. A framework for the development of a general-purpose cross-section analysis software, is presented and various features of few commercially available software packages are compared using some example cross-sections.
... The cross-section geometry can be in circular, rectangular, square, hexagonal, etc., forms in addition to the position of steel bars and their areal and elastic modulus amounts. For example, in the literature, especially in stiffness calculations, some works take the ratio of elastic modulus of concrete and steel, where stiffness is defined as the elastic modulus multiplied by the moment of inertia [6]. Such an elastic modulus ratio concept is important not only in common structural elements but also in prestressed, jacketed, and encased concretes [4,5]. ...
... Such an elastic modulus ratio concept is important not only in common structural elements but also in prestressed, jacketed, and encased concretes [4,5]. It is involved in all expressions related to the mass or weight of the members, axial, and flexural actions, deformations, strains, and stresses [6]. The importance of the elastic modulus ratio will be explained later in this paper based on a set of new formulations. ...
The combination of linearity and elasticity assumptions provides classical calculation procedures for the reinforced concrete (RC) columns and beams against internal and external seismic loads. In these calculation procedures, the elasticity modulus of the concrete is taken into account by ignoring the steel reinforcement due to its small area percentage in the total cross-section area. This paper presents an innovative column stress calculation procedure considering the concrete–steel composition as the equivalent elastic modulus based on the classical Hooke’s Law. This methodology takes into consideration also the elastic modulus of the steel, providing a reduction in the factor of safety. The application of the proposed method is presented for a series of RC column cross-section areas. It is observed that the proposed methodology leads to elastic modulus improvement of 6% to 27% compared to conventional calculations. The necessary flow chart for the execution of the proposed process steps and accordingly developed MATLAB program are provided for the application.
... When taken as a whole, the stress-strain curve for steel is quite complicated. However, in most circumstances, an idealization that is typically utilized is elastic-perfectly plastic (non-strain hardening) [17]. The reinforcing steel bars were modeled using Abaqus' plasticity model, a bilinear model characterized the stress-strain relationship of reinforcement (elastic perfectly plastic) as shown in Fig. 3. ...
... The elastic modulus and Poisson ratio were set to 200 GPa, and 0.3 respectively, since the steel elasto-plastic model were used ABAQUS requires initial yield stress at zero plastic strain, therefore yield strength and plastic strain were set to 410 MPa and 0 respectively [18]. Fig. 3: Idealized elasto-plastic stress-strain curve for steel by Anwar [17]. ...
This paper investigates the load capacity and failure modes of slender hollow RC column under axial and eccentric loads. For the slender hollow columns, different load eccentricities and hole shapes are used. The finite element software ABAQUS is used to model and analyze the columns. The experimental test result is used to conduct a verification investigation of the nonlinear finite element modeling. All specifications of the experimentally tested columns are taken into consideration in the modeling to establish the verification of the model. When the modeling and test results are compared, it is noticeable that they are in good agreement. As a result, the modeling’s accuracy is proved. Then, a parametric study included different slenderness ratio, section shape, concrete strength and SFR strengthened has been done with the same modeling method. The effects of these variables on the column load capacity are investigated. It is found that increasing slenderness ratio led to smaller peak load. Increasing of moment of inertia of square and circular section decreased the peak load capacity. The maximum bearing capacity increased with higher concrete strength. Also, SFR distribution through the length of columns effected on load bearing capacity.
... Often each of these types and their combinations are treated separately and differently for the purpose of determining design strength of members, which is largely derived from the strength and capacity of its cross-section. Table 1 below shows the wide spectrum and diversity of a concrete cross-section design problem (Anwar and Najam, 2016). Traditionally, each category of cross-section is treated separately with different theoretical treatment or design procedures. ...
... The general case of a section undergoing bending about an arbitrary axis will cover biaxial loaded columns, as well as beams. Therefore, a cross section undergoing axial and biaxial-flexural deformations ( Fig. 1) will be considered here to present the general formulation of this unified approach (Anwar and Najam, 2016). ...
The construction of composite high-rise building structures is rapidly increasing in recent years due to increased advantages in terms of improved structural performance and faster construction. This results in a significant reduction in cost and other resources, especially for high-rise building projects. The recent trends in composite construction are governed by the an achievement of optimum interactive behavior between structural steel and concrete components designed to take benefit of the best load-resisting characteristics and economy of each material. This paper discusses some key issues related to the application and design of composite structural components to result in better performance of high-rise buildings against gravity and lateral loads. It presents a unified approach to determine the axial-flexural capacity of various composite and complex cross-sections. Using this approach, the analysis of all composite cross-sections can be performed in an integrated manner. The paper also discusses important considerations which should be kept in mind for an effective design of composite members (columns, shear walls, floors, link beams and transfer systems) and presents insights on the practical aspects of composite concrete-steel construction in tall buildings
... Ductility is defined as the ability of a member to withstand a load after failure (Anwar & Najam, 2016), and in the current study it was measured from the load deflec-246 Sahib, H. A., Al-Asadi, A. K. (2022). Prediction of shear strength of cfRP-strengthened reinforced recycled aggregate concrete beams using various strengthening methods. ...
Fibre reinforced polymer (FRP) strengthening is a possible option when the load carrying capacity of a structure needs to be increased for various reasons. On the other hand, the focus nowadays aims to save the environment by reducing the waste material. A suggestion was made to use waste concrete as an aggregate. If this new material was used more, it would be possible to use recycle concrete aggregate (RCA) and carbon fibre reinforced polymer (CFRP) to strengthen reinforced concrete (RC) structures and make them more environmentally friendly. An experimental investigation study on the shear behaviour of RC beams strengthened with CFRP strips was carried out. Tests were conducted on six reinforced concrete beams, with variations in the replacement ratio of RCA and strengthened by different configurations of CFRP under four-point loading. The results indicated that the load carrying capacity was increased, on average, by 18.09 and 35.04% for beams strengthened with CFRP with an inclined strip (IS) and continuous strip (CS) configurations respectively. The results also indicated that the increases in the stiffness were 21.08 and 37.31 for beams strengthened with CFRP in the IS and CS configurations, respectively. In addition the ductility of the beams increased after strengthening.
... Hereby, a focus is set on making provisions against structural degradation and particularly preventing catastrophic failure. The loading and energy absorption capacity related performance can be specified in a load-displacement graph, as done e.g. by [62] for building structures, or for crash absorbing structures, see e.g. [63]. ...
Additive manufacturing is a promising technology for the sustainable production of lightweight parts through the direct fabrication of complex, near-net shapes. In addition, the great design freedom enables the application of topology optimization for automating the structural layout and hereby more efficient solutions for load-bearing components can be found.
However, there is no systematic approach for implementing sustainability as a guiding principle in the product development to collectively address related criteria. In this work, this issue is addressed in multiple ways and a novel generative design methodology is developed and demonstrated regarding the sustainable design for additive manufacturing and specifically laser powder bed fusion. In this connection, suitable sustainability measures are defined and a number of models are developed for automation.
Generative design models with advancements in topology optimization are contributed for automating the design and process layout. Hereby, restrictions of current methods in collectively optimizing very nonlinear behaving mechanical and process-related performance goals are overcome with reasonable computational effort. Furthermore, the resources in the laser powder bed fusion process are analyzed and a predictive model for early stage evaluation of solutions regarding their consumption is proposed. The latter is validated with production experiments and shows adequate qualitative as well as quantitative accuracy.
The contributions are combined in a multidisciplinary generative design model regarding sustainability optimization for laser powder bed fusion. The latter demonstrates effectiveness and feasibility in collectively modeling and optimizing multiple sustainability criteria in a lightweight design application.
... Renovation was proposed in cases where the existing structures needed to be upgraded to improve their performance by either altering the scope of the structure, providing additional facilities or improving existing ones (Anwar, Ahmed, 2017). Rehabilitation was proposed to make possible compatible uses for properties through repair, alterations and additions while preserving those portions or features which convey historical, cultural or architectural value. ...
After the inscription of the Historic City of Yazd on UNESCO’s World Heritage List in 2017, the number of tourists visiting increased. The area is formed of several neighborhoods. This study aims to propose a conservation plan for the oldest, the Shah Abul-Ghasem Neighborhood, using the urban design qualities suggested by Golkar. The study based on a field survey in the neighborhood was carried out in such a way that items related to urban design qualities were photographed and categorized into environmental, functional and aesthetic-experimental components. Proposed measures and recommendations for the development of tourism in the area are presented based on the field survey results.
... The reason for this is believed to be the higher confinement for circular columns than for noncircular columns due to the uniform distribution of confinement pressure around the circular cross section. 30 In contrast, for noncircular cross sections, the confinement pressure is much higher at the corners than on the flat sides. The high confinement pressure at the corners causes premature failure due to stress concentrations. ...
... The researchers conducted that the circular columns are suitable for seismic zones that need high strength and ductility in all directions [39]. The results of this study proved that the circular columns give enhanced performance than the square columns for equivalent cross-sectional area. ...
This paper looks at the effect of fibers shape, hollow ratio and cross sectional shape on the behavior of solid and hollow slurry infiltrated fiber concrete (SIFCON) columns. Two shape of steel fiber were used in the present study, straight micro fiber and hooked end fiber. Therefore, this study comprised of casting and testing two groups of SIFCON column specimens; columns group reinforced by hybrid fibers (3% straight micro fiber + 3% hooked end fiber) and columns group reinforced by 6% hooked end fibers. Each group comprises of six column specimens, 3 of them are circular and the others are square. Each circular column has an equivalent square column with the same cross-sectional area. These six columns have different hollow ratios (β = 0, 25% and 50%). Non-linear finite element analysis of axially loaded SIFCON columns has been done by using ABAQUS computer program. Analytical predictions of load carrying capacity, axial displacement, ductility and energy absorption capacity are compared with experimentally observed results of SIFCON columns, and the results shown a good agreement between them. The results illustrated that despite the small cross-sectional area and presence of longitudinal hole in columns, SIFCON columns were shown dazzling performance in terms of load carrying capacity, ductility and energy absorption capacity especially for columns reinforced by hybrid fiber. On the other hand, column performance deteriorates with increased hollow ratio. The results also demonstrated that the performance of circular columns exceeded that of square columns for the same cross-sectional area.
... model does not have blind bolts penetrating the SHS column for simplicity reasons although mechanical models that describe the behavior of blind-bolted angle connections have been proposed by Malaga-Chuquitaype and Elghazouli (2010). In this paper, the focus is on the effect of the different components on the connection by Anwar and Najam (2016), in relation to the strength and the rotational stiffness of the joint. The support and loading conditions of the three-dimensional finite element simulation are the same as the experiment by Karagiannis et al. (2017) for verification purposes.The displacement-induced load at the end of the beam is limited to 7mm in order the behavior of the joint to remain elastic. ...
Hybrid steel to timber connections are found in many buildings and bridges. These connections offer several advantages such as ease of construction and energy dissipation. This research paper aims to study the mechanical behavior of bolted hybrid connections that consists of a square hollow steel column (SHS) and a glulam timber beam. The connection between the two structural members is achieved by means of angles and preloaded bolts. A reference model is constructed and verified by comparison to experimental and numerical data from the international literature. Additionally, several parameters that affect the response of the connection are modified in order to investigate and quantify their effect, resulting in seven different case studies. These parameters are the size of the bolts, the thickness of the angles and the addition of stiffener. The moment-rotation curve of each case study is constructed and the results are commented. Finally, a proposed optimal configuration of the hybrid connection is presented.
... Bar structures may be subject to multiple solicitations (Anwar, 2017) as compression, traction, bending, twisting and impact, e.g. in trees and long bones. In the present paper we compared geometric as well as mechanical properties of straight prismatic porous bars with same volume but different forms. ...
There are considerable discussions amongst structural engineers about structural modeling but not much about the modeling of foundation. This is an interesting topic because a lot of the time while modeling any structure, the foundation is modeled in a very simplistic manner. It is assumed as fixed, pin or roller support. However, in reality, such idealized foundations are very rare. Most of the foundations are either footings, mat, piles, or other embedded structures. In fact, foundations are often huge structures by themselves. It may not always be good to simply convert them into single point and then assume them to be fixed, pin or roller. This article focuses on how the modeling of the foundation may greatly change the response of the structure itself and loads on footings, depending on the type of the structure. It is interesting to see that smaller structures like low rise buildings may be more affected by this modeling than high-rise buildings. Thus, understanding the effect of modeling of foundations and how it can be done to account for various interaction between structure and soil is of great importance. The soil-structure interaction is quite advance topic which is not discussed here in detail but basic concepts that should be considered are identified. Let us start with simple portal frame as shown in Fig.
In the field of structural design, there are a few concepts that many engineers are either not fully aware of or they are not utilizing it to the full extent. One of them is 'Moment curvature curve'. It contains a lot of information, but it seems it is one of the secrets that has been kept from many structural engineers. The moment-curvature (M-φ) relationship is probably the most important and useful action-deformation curve especially for flexural and compression members such as beams, columns, and shear walls. Many of the design codes, design procedures and handbooks do not provide sufficient information for the computation and use of M-φ relationships. This curve is dependent on several parameters including the material properties, cross-section geometries and level of axial load on the member.
Reinforced concrete structures are subjected to a complex variety of stresses and strains. The four basic actions are bending, axial load, shear, and torsion. Presently, there is no single comprehensive theory for reinforced concrete structural behavior that addresses all of these basic actions and their interactions. Furthermore, there is little consistency among countries around the world in their building codes, especially in the specifications for shear and torsion. Unified Theory of Reinforced Concrete addresses this serious problem by integrating available information with new research data, developing one unified theory of reinforced concrete behavior that embraces and accounts for all four basic actions and their combinations. The theory is presented in a systematic manner, elucidating its five component models from a pedagogical and historical perspective while emphasizing the fundamental principles of equilibrium, compatibility, and the constitutive laws of materials. The significance of relationships between models and their intrinsic consistencies are emphasized. This theory can serve as the foundation on which to build a universal design code that can be adopted internationally. In addition to frames, the book explains the fundamental concept of the design of wall-type and shell-type structures. Unified Theory of Reinforced Concrete will be an important reference for all engineers involved in the design of concrete structures. The book can also serve well as a text for a graduate course in structural engineering.