American Institute Of Steel Construction Research Articles

Design method for axially compressed H-sectional aluminium alloy slender column based on CSM

In this study, a section-limiting stress that considers the influence of cross-section slenderness on the load-carrying capacity proposed by the continuous strength method (CSM) is introduced for the first time in the design of axially compressed H-section aluminium alloy slender columns. Experimental and numerical simulation tests are conducted on these columns to understand their axial compression performance and failure modes, with subsequent validation of the numerical simulation methods. Using the CSM limiting stress, imperfection factor, and stability calculation factor, this study proposes a design method for the overall stability load-carrying capacity of axially compressed H-section aluminium alloy slender columns. The load-carrying capacity predictions of the proposed design method are compared with those of the European, American, Australian/New Zealand, and Chinese design standards using axial compression tests and numerical simulations. An evaluation of these design methods and standards is also presented. In addition, reliability analyses are conducted following the approaches proposed by the American Institute of Steel Construction and the European design standard to assess the reliability levels of the aforementioned design methods and standards. Finally, the study presents a calculation example of an aluminium alloy slender column using the proposed design method.

Intermediate-point bracing for columns: New stiffness–buckling load formulae

According to the stiffness equation provided in the American Institute of Steel Construction (AISC) design specifications for intermediate-point braces, the required point brace stiffness increases with the number of point braces. This research aims to formulate a new stiffness design equation for intermediate-point braces that accounts for the decline in required stiffness with an increasing number of braces. The brace stiffness (β)–buckling load (Pcr) relationships for columns with point braces were investigated by performing a buckling analysis using the energy method with the Fourier series. A formula was derived, defining the β−Pcr relationships for each buckling mode of the columns, regardless of the number of point braces and whether the buckling is elastic or inelastic. The AISC stiffness equations for point braces were significantly conservative under most buckling loads. The proposed stiffness design equation requires lower brace stiffness with an increasing number of point braces, resulting in smaller brace members than the AISC design equations. Additionally, the proposed strength design equation can set relatively high strength requirements for the brace, reflecting that stiffness governs the design of the point brace. These new equations offer a more precise and efficient method for calculating required brace stiffness, providing valuable insights to improve structural design capabilities.

An optimal design approach for steel space frames with T-stub semi-rigid connections considering soil-structure interaction

An optimization technique for designing the steel space frame with T-stub semi-rigid connections and interaction between soil and structure is presented in this article. A three-parameter-based elastic foundation model is utilized to investigate soil-structure interactions (SSI). To enable two-way data transfer for all optimization methods, computer software was developed using C# version 17.8.6, which connects to SAP2000-OAPI version 22. Particle swarm optimization (PSO) and teaching-learning-based optimization (TLBO) are employed for optimal designs. These optimization techniques choose profile sections from a list, including 64W discrete sections from the American Institute of Steel Construction (AISC). The Load and Resistance Factor Design-American Institute of Steel Construction (LRFD-AISC) strength constraints, geometric constraints, inter-storey drift constraints, and displacement constraints are considered during optimization. The first phase entails creating optimal designs for two unique steel space frames that consider SSI but do not include T-stub semi-rigid connections. Following that, the same optimization procedures are carried out with T-stub semi-rigid connections. The parameters needed for the foundation model are obtained through soil surface displacements. Utilizing T-stub semi-rigid connections while considering the interaction between the structure and the soil produces increased structural weight.

Experimental Investigation and Numerical Analysis of the Axial Load Capacity of Circular Concrete-Filled Tubular Columns

This paper focuses on the experimental investigation of the axial load capacity of CFT (concrete-filled steel tube) columns under actual construction conditions during building reconstruction. A total of four samples were loaded up to failure. The varied parameters were the column length and absence/presence of the concrete infill within the steel tube. Further, the analysis is extended to developing a numerical model in the finite element-based software ABAQUS version 6.9. This numerical model includes material and geometrical nonlinearities and was validated with the experimental results. The contribution of the concrete core to the column capacity and the concrete core confinement effect are discussed. Finally, the column capacity was calculated according to several design codes: the Eurocode 4 with and without considering the confinement effect, American specifications, Australian standards, the American Institute of Steel Construction, and the Architectural Institute of Japan. The Eurocode 4 considering the confinement effect provides the closest results to those obtained in the tests.

Lateral torsional buckling of unsymmetric beams by FEM with linear elements

As the exact solution of lateral torsional buckling of elastic prismatic beams is practically limited to the simple case of simply supported beams under equal end moments, other loading conditions and boundary conditions require more practical solutions to the problem. As the general solution of lateral torsional buckling of unsymmetric beams is a function of the sign of the bending moment along the axis of the beam, i.e. location of the shear center concerning the compression zone of the cross section, application of the current traditional empirical expressions such as coefficient of the moment, Cb, becomes highly inconsistent and unwarranted to capture the correct critical moment as acknowledged by the American Institute of Steel Construction, AISC. The finite element method, FEM, offers a feasible alternative to overcome these shortcomings. FEM is formulated in its simplest form of linear elements for the general case of lateral torsional buckling of unsymmetric cross sections. Finite element development shows that the characteristic equation is of the nonlinear quadratic eigenvalue problem type. Using the classical polynomial shape functions for beams, FEM proves to be extremely accurate and can overcome the high inconsistencies and discrepancies embedded in the application of the classical methods.

Design method for determining appropriate stiffness for end point braces

The high dependence of end point braces on rotational restraint conditions differentiates them from intermediate point braces. Although the point brace stiffness equation of the American Institute of Steel Construction (AISC) design specifications applies to both braces, it restricts the stiffness to only the buckling load based on the unbraced length and an effective length factor of 1, which is too conservative for end point braces. This study investigated the relationship between end point brace stiffness and column buckling loads through buckling analyses using slope–deflection equations with stability functions, considering diverse supports, end rotation constraints, and column counts. Irrespective of the column count, the columns with end point braces exhibited a non-sway elastic buckling load of up to four times the Euler buckling load depending on the rotational restraint at the column ends. The proposed procedure enhances the AISC regulations by introducing a new equation that allows up to 90% utilization of the buckling load based on the unbraced length and an effective length factor of 1 or less, considering column end rotational constraints. The procedure was applied to six frames undergoing elastic or inelastic buckling and validated by assessing the buckling loads and related point brace stiffness. The proposed procedure significantly enlarged the load-bearing capacity of the column compared with the AISC design procedure, although both approaches obtained comparable point brace cross-sectional areas. It extends the buckling load limit for columns or frames with an end point brace, providing predictive insights into brace stiffness to improve structural design.

Enhancing the performance of anti-blast windows through the use of carbon nanotube reinforced polymer gaskets

Anti-blast windows are critical in ensuring the safety of structures exposed to explosive threats, such as terrorist attacks or accidental explosions. These windows consist of blast-resistant glass and a structural framing system that must be able to withstand the high-pressure shock of an explosion. The present study presents a novel structural framing system for anti-explosion windows that adheres to the standards set forth by the American Institute of Steel Construction (AISC) 360-16 Specifications and the Aluminum Design Manual (ADM) 2020. The system encompasses a distinct combination of aluminum 6063-T6 angles and ASTM A36 steel embed plates that are connected by spaced bolts and augmented by the addition of a carbon nanotube-reinforced polymer CNT/polymer gasket. A numerical investigation utilizing ABAQUS software was performed to evaluate the mechanical behavior of the window assembly under intense blast loads, taking into account the effect of incorporating the CNT/polymer gasket and the impact of the gasket weight fraction on the performance of the structure. The results of the study demonstrate that the use of the CNT/polymer gasket and increasing the wight fraction ratio resulted in improvement of the blast performance of the window frame structure in terms of the significant reduction in stress, deformation and rotation, as well as the increasing of the energy dissipation during the blast event compared to when the gasket was not utilized. These findings offer crucial benchmarks for the proposed structure and offer recommendations for its implementation in industry practice, with the ultimate goal of developing more efficient and effective designs for anti-explosion windows that meet industry standards.

Lateral Load Behavior of C-PSW/CFs Using Steel Members as Boundary Elements

Composite plate shear walls/concrete-filled (C-PSW/CFs), also known as SpeedCore systems, are a relatively new structural member in American codes and standards. Prior research has focused primarily on C-PSW/CF walls with either flange/closure plates or filled composite members as boundary elements. Walls without boundary elements have also been studied, but they are no longer permitted by the American Institute of Steel Construction (AISC 341-22). The reason is that composite walls without boundary elements do not provide adequate ductility for seismic design. This paper presents the results of experimental and numerical studies conducted to evaluate the cyclic lateral load behavior of C-PSW/CFs using hot-rolled structural steel members as boundary elements. The steel web plates of the C-PSW/CF specimens were connected to each other using threaded tie bars with double nut connections. Composite interaction between the steel and concrete infill was achieved using the tie bars and additional shear studs welded to the boundary elements. The composite walls were embedded and anchored to reinforced concrete foundation blocks using welded deformed bar anchors. The experimental investigations focused on the cyclic lateral load-drift responses including test observations and limit states, moment-rotation response of the plastic hinge and the section moment-curvature relationship, overall lateral stiffness, strength, and displacement ductility. The experimental results show that the specimens exceeded their nominal flexural capacities calculated using the plastic stress distribution method or fiber-based section modeling using measured material properties. The specimens had plastic hinge rotation capacity greater than 0.028 rad. and displacement ductility ratio greater than 5.2. Detailed 3D nonlinear inelastic finite element models and simpler fiber-based macro models of the tested specimens were developed and benchmarked using experimental results. The detailed 3D finite element models can reasonably simulate the global and local behavior of the specimens, and are recommended for conducting further parametric studies of composite wall design details. Simpler fiber-based macro models can efficiently simulate the cyclic lateral load behavior of the specimens, and are recommended for modeling C-PSW/CFs while simulating the behavior of multi-story building structures.

Optimal design of semi-rigid connection steel frame with infilled shear walls using dolphin echolocation algorithm

In this paper, the dolphin echolocation algorithm (DEA) was applied for optimization. Two different two-dimensional semi-rigid connection steel frames with infilled shear walls (SFIWs) were optimized to obtain the minimum weight with constraints on the element stresses and storey drift ratio according to the American Institute of Steel Construction (AISC) Load and Resistance Factor Design requirements. With the proposed method, the specific details of the infilled shear walls are not given during the design process, but are characterized by the lateral stiffness. The designer can decide which types of infilled shear walls are used according to the result obtained from the optimization. The infilled shear walls are modeled as braces with equivalent lateral stiffnesses, while the semi-rigid connections are used to obtain the practical behaviors of the SFIWs. The results demonstrate that the proposed method is suitable for optimizing semi-rigid connection steel frames with infilled shear walls.

Experimental and analytical investigation of notched steel plate as a novel shear connector

To ensure durability and save time in construction, steel–concrete composite slabs are widely used in aging bridge replacement. This paper proposes a novel type of shear connector named notched steel plate (NSP). The shear properties of four types of NSP shear connectors with heights of 50 mm and 75 mm and thickness values of 9 mm and 12 mm were evaluated by conducting push-out tests. Concrete cracks occurred firstly during the loading. After removing the concrete block, fracture of NSP shear connectors at the welding zone between NSP and steel plate was observed. A finite-element (FE) analysis was conducted considering the nonlinear properties of materials and interface between the NSP and concrete block. The shear stiffness, shear capacity and failure pattern obtained using the FE model matched with the test data. The verified FE model was used to investigate the failure mechanism of NSP and to clarify the effect of the constraint force, concrete compressive strength and steel strength on the NSP shear capacity. The experimental shear capacity values were compared with the values calculated by the specifications for channel and angle shear connectors. The results of the NSP shear capacity were similar to those obtained based on the American Institute of Steel Construction (AISC) specifications and Eurocode 4.

Simple Truss Model to estimate the shear strength of short links in the Eccentrically Braced Frame (EBF) steel system

The measured-to-estimated shear force ratio (Overstrength ratio) is an important metric for the capacity design of a shear link’s adjacent elements and connections. However, some investigations found that short links had an abnormally high overstrength ratio if the shear strength of short links is estimated by the provisions of the American Institute of Steel Construction (AISC 341-16). This study assesses the AISC 341-16 equation’s precision in estimating the shear strength of short links and suggests a Simple Truss Model (STM) for this purpose. The proposed STM considers the strain hardening of flanges and the web due to cyclic loading, where the STM was derived from the end links to reach the plastic moment strength (Mp). An experimental database of 109 specimens from the literature was gathered, screened, and preprocessed to assess the performance of these models. This research found that the overstrength ratio for built-up and rolled W-shape short links is underestimated by the AISC 341-16 provisions; only 4% and 13% of built-up and rolled W-shape specimens, respectively, meet the suggested AISC overstrength value of 1.25. The proposed STM model beat the AISC equation in predicting the overstrength values, with mean values of 1.21 and 1.15 for the built-up and rolled W-shape specimens, respectively. Additionally, for the built-up and W-shape specimens, respectively, 58% and 73% of the overstrength determined by STM conform with the recommended AISC overstrength value of 1.25. Since the STM considers the link length and cross-sectional area, contrary to what the AISC predicted, the calculated overstrength values are less susceptible to the link length ratio, flange width-to-thickness ratio, and the ratio of the flange-to-web areas. This study recommends switching from the current AISC equation to the STM because the STM predictions have statistical metrics that are noticeably better than the AISC equation, with Root Mean Square Error (RMSE) and Mean Absolute Percentage Error (MAPE) of 0.27 and 18.6%, 0.22 and 14.6%, and built-up and rolled W-shape links, respectively.

Teaching-learning-based optimization of unbraced steel frames with semi-rigid connections and column bases

The teaching-learning optimization (TLBO) technique is applied to unbraced steel frames with semi-rigid beam-to-column connections and semi-rigid column-to-base connections. The algorithm for design produces optimized steel frames by choosing appropriate sections from a set of standard steel sections. These standard steel sections, including wide-flange profiles (W), are provided by the American Institute of Steel Construction (AISC). The first example is subjected to the displacement, inter-story drift, and stress constraints of AISC-Load and Resistance Factor Design (LRFD) regulations. In addition, the displacement and stress limitations of the AISC-Allowable Stress Design (ASD) standard and the geometric (size) requirements are implemented in the last two examples. In finite element analysis, optimal designs of three alternative unbraced frames are performed with and without semi-rigid beam-to-column and column-to-base plate connections. All optimization techniques are encoded in the high-level programming language C# version 17.4.4 to integrate with SAP2000 version 22's Open Application Programming Interface (OAPI). The analysis results indicate that the rigidity of connections is determining parameter in the weight optimization of unbraced steel frames.

Comparative Study of Analysis and Design of Pre-Engineered- Buildings Using Staad Pro Software

Abstract: The STAAD-PRO offers an even bigger advantage over the manual procedure since it produces results that are more exact and precise. As the members are designed, using PEB construction instead of the Conventional Steel Building (CSB) design idea provides many benefits. With the use of conical IS sections, the PEB structure is designed in accordance with the bending moment distribution diagram along the whole span of the beam and column, therefore lowering the demand for steel.The stiffness matrix method is used to assess the basic framework of PEB systems. The structure's design geometry, load, and desirable load combinations as required by the user-selected building code are produced using acceptable voltage design (AVD) in compliance with the American Institute of Steel Construction or IS 800 specification in various modes. To produce a workable design, the software runs through the maximum number of cycles specified. The maximum displacement beam that results is 0.530. The end girder has a maximum shear force (Fy) and bending force (Mz) of 2.541 KN and 4.381 KN-m, respectively

Structural And Cost Analysis Of Reinforced Concrete And Steel Framed Structures: A Comparative Study In Lefkoşa, North Cyprus

The development of structural systems, materials, and analytical techniques have been used for designing different types of structures. Comparative studies of various buildings help identify the optimum choice depending on the project requirements and conditions. In this study, 8-story residential structures are designed in Lefkoşa, North Cyprus by steel and reinforced concrete frames with different load-resisting systems. Building Code Requirements for Structural Concrete (ACI 318-19) and American Institute of Steel Construction (AISC-15th edition) are both followed and the response spectrum method (RSM) is employed while ETABS and SAP2000 are used for modeling and analyzing the structures. The results obtained are the base shear, story shear, displacement, axial forces, bending moments for selected columns, the quantity of steel, the quantity of concrete, and the quantity of formwork are compared for different structures. The result shows that the cost of steel structure is higher by around 13 % as compared to RC.

Optimal Design of Semirigid Connection Steel Frame with Steel Plate Shear Walls Using Dolphin Echolocation Algorithm

Steel frame with steel plate shear walls (SPSWs) is used to resist lateral loads caused by wind and earthquakes in high-rise buildings. In this load-resisting system, the cost and performance are more efficient than in the moment frame system. Behaviors of beam-to-column connections are assumed to be pinned or fixed to simplify the calculation in the past few decades. However, studies have stated that such a simulation fails to reveal the response of beam-to-column connections. In this paper, a newly developed metaheuristic optimization algorithm—the dolphin echolocation algorithm (DE)—based on foraging prey using echolocation in dolphins is applied as the present study optimizer. Two different two-dimensional semirigid connection steel frames with SPSWs are optimized to obtain the minimum cost of semirigid connection steel frame with steel plate shear walls with constraints to element stresses and story drift ratio according to the American Institute of Steel Construction (AISC) Load and Resistance Factor Design (LFRD). SPSW is modeled as a brace with equivalent lateral stiffness, while the P−△ effects are considered in the steel frame. Semirigid connections are used to reveal the actual responses of beam-to-column connections. The results demonstrate the proposed method’s effectiveness for optimizing semirigid connection steel frames with SPSWs and the interaction between semirigid connections and the SPSWs.

Strength of transverse plate-to-rectangular HSS connection under single-concentrated compression

According to the American Institute of Steel Construction (AISC) Specification for Structural Steel Buildings (AISC 360), the transverse plate-to-HSS bearing strength of rectangular hollow structural sections (HSS) under single-concentrated compression shall be determined based on the applicable limit states in Section J10. From all the limit states, both the web local yielding (WLY) and web local crippling (WLC) are applicable for transverse plate-to-HSS concentrated compression. However, all the limit state equations in J10 were originally developed for wide-flange sections. Unlike the in-plane compression on the web of a wide-flange section, the concentrated compression on an HSS member acts like an eccentric load on the HSS web and a distributed load along the HSS flange. The eccentric load on the web and flange local bending due to the distributed load can considerably reduce the failure load as compared to the wide-flange sections. Experimental and nonlinear finite element analyses (NLFEA) carried out in this study indicate that WLY, WLC, and flange bending always simultaneously occur at failure of an HSS; hence, they are not independent limit states. While AISC WLY equation predicts a strength closer to the experimental and NLFEA results, the bearing strength of HSS members can range from 16% to 66% of that predicted by AISC WLC equations. Based on actual failure modes, 251 FE models were analyzed, and a single transverse plate-to-HSS bearing strength equation under compression for HSS members was formulated.

Design of buckling restrained steel braces using application programming interface between simulation and discrete optimization

In this study, buckling restrained braces (BRBs) are optimized through application programming interface between simulation and discrete optimization. It is aimed to maximize the energy dissipation capacity of BRBs considering the American Institute of Steel Construction (ANSI/AISC 341). Unlike other studies, BRBs modeled in the finite element packaged software are directly linked to optimization algorithms. So, the geometric and material nonlinearities are also considered. Harmony Search Algorithm (HSA), which simulates the improvisation musician performances in finding pleasing harmony, and Black Widow Optimization Algorithm (BWOA), which imitates inimitable paring attitude of black widow spiders, are taken as the optimizer tools of this study. They encoded in Microsoft Visual Basic programming language. Initially, the algorithmic performances of the HSA and BWOA are compared and evaluated on two benchmark structural engineering design problems. Afterward, two different shaped BRBs are modeled in a finite element analysis (FEA) based software, namely ANSYS Workbench. Then, the obtained simulations are integrated with the HS and BWO algorithms throughout the application programming interface without identification of complex objective function and design constraints in formulations. These are directly calculated by ANSYS Workbench over very simple formulas. So, the attained optimum designs of BRBs are investigated with a new approach. Furthermore, in order to see the supreme algorithmic performances of the HSA and BWOA, all benchmark and BRB design problems are solved so-called well-established conventional standard Genetic Algorithm (sGA). Eventually, the proposed novel design methodology gives opportunity and eases to the designers since it provides convenience in solving complicated problems having nonlinear objective function and design constraints that are tiresome to encode.

Comparative study and performance evaluation of steel moment resisting frames design with: Force-based design and performance-based plastic design

Incremental Dynamic Analysis (IDA), Nonlinear Response History Analysis (NLRHA) and Nonlinear Static Pushover Analysis (NSPA) has been carried out to evaluate seismic performance of Steel Moment Resisting Frames (SMRF). SMRF’s are used as the lateral resisting systems which consist of columns and beams joined by welding or using high strength bolts or combination of both. The resistance offered to the lateral forces is due to rigid frame action which develops bending moment and shear force in the frame members and joints. The 9-storey SMRF is been evaluated for two frames designed by Force Based Design (FBD) method and Performance Based Plastic Design (PBPD) method. The FBD frame is designed by using codal provision of ASCE 7 (American Based Seismic Code) and AISC (American Institute of Steel Construction) whereas PBPD frame is designed as per proposed work of Lee and Goel (2001) in which energy balance equation and pre-selected yield mechanism is considered. The evaluation study showed that the PBPD method for steel moment resisting frame is significantly more efficient in achieving a certain inelastic displacement/ductility for given seismic hazards compared to the existing design standards/specification for this system. By Nonlinear Static Pushover Analysis (NSPA) the PBPD method has achieved the target yield drift of 1.11% and FBD method has achieved 1.22% where the assumed yield drift was 1%. From NLRHA the percentage difference in achieved ductility factor for frame design by FBD method is 46.28% whereas for PBPD method it is 16.81%. From IDA inter storey drift is observed maximum in AISC design frame compared to PBPD design frame. Therefore, PBPD method frames responded as intended in design with much improved performances over those of the corresponding FBD method.

Compressive behavior of light–gauge steel tubes filled with concrete containing recycled aggregates

Abstract The axial capacity of light–gauge steel tube columns filled with concrete including recycled asphalt pavement (RAP) aggregates and recycled concrete aggregates (RCA) was investigated. A total of 51 specimens, including 6 bare steel tubes, 30 composite columns and 15 concrete-only columns were tested under uniaxial load. Fifteen concrete mixes were considered by replacing the weight of natural coarse aggregates (NA) with RCA and RAP at replacement levels of 0, 20, 40, 60, 80, and 100%. In addition, RAP and RCA were combined in the same mixes with replacement levels of (1) 20% RAP and 80% RCA; (2) 40% RAP and 60% RCA; (3) 60% RAP and 40% RCA; and (4) 80% RAP and 20% RCA. Experimental results were analyzed by reporting the ultimate capacities and the patterns of failure. Moreover, the predictions of EUROCODE 4 (EC4) and American Institute of Steel Construction (AISC) codes were checked. ABAQUS software was used to perform a finite element analysis (FEA) of the tested composite specimens. The results showed that using recycled aggregates decreased the carrying capacity of columns. Carrying capacity of light–gauge steel tubes filled with concrete including different combinations of RCA, NA and RAP aggregates can be conservatively predicted by the AISC and EC4 recommendations. Results of FEA showed a good agreement with the experimental results.

Estimation of Web Distortion Effect on the Elastic and Plastic Limiting Lengths for Lateral Torsional Buckling through the Web Strain Results

The present study is aimed to estimate the influence of the web distortion on the elastic (Lr) and plastic (Lp) limiting lengths given in the American Institute of Steel Construction (AISC code) for the lateral torsional buckling behavior of steel beams. For this aim, the W44x335 beam is adopted in the buckling analyses carried out by the ABAQUS finite element (FE) program. The strain results at mid-height of the web at mid-span of the beam are taken into account as monitoring parameters. The web strain results are found highly greater than the yield strain value when L/Lr is equal to 1.0. Hence, the elastic limiting length (Lr) is required to be considered greater than the calculated length as per the code formulation. The section is obtained to reach the maximum strain value at the web before the unbraced length (L) is equal to the plastic limiting length (Lp). Therefore, the calculated Lp is estimated with the given analytical formulation to be highly shorter than the length through the FE analysis. These outcomes prove that the formulations of the limiting lengths proposed in the AISC code don’t consider the influence of the web distortion that is predicted to lead to reducing the torsional and warping rigidity of the section. With the study, it is proposed to determine a reduction coefficient by performing more numerical analyzes for different cross sections and free openings in the regulation.