Structural fatigue in the 34-meter HA-Dec antennas

Structural modifications to the 34-m hour-angle-declination antennas, coupled with the use of the antennas beyond their intended lifespans, have led to structural fatigue, as evidenced by damage to the declination drive gear and cracks on the structural members and gussets. An analysis and simulation were made of the main antenna structural members. The analysis showed that the total stress to the antenna structure substantially exceeds the maximum levels recommended by the American Institute of Steel Construction (AISC). Although each of the separate static conditions of stress is only 50 percent of the total stress and does not reach the AISC reduced yield limit, fatigue can and did occur, causing the material to crack in the weakest places

Design and construction of tank-chassis and lifting structure for centrifugal pump HL260 M powered by a Diesel Engine

This article deals with the design, simulation and construction of a fuel storage tank-chassis and a lifting system coupled as a single unit to a Cummins QSK19 engine driven HL260m pump that can guarantee an operating autonomy of up to 12 continuous hours and can be transported to different locations by means of lifting systems. For the mechanical design the recommendations of the American Institute of Steel Construction (AISC) and the application of the failure criteria for Von Mises ductile materials or Maximum Energy Distortion were used. For the dimensioning of the storage tank, the average consumption stipulated by the manufacturer was used and the simulations were performed with SolidWorks®. A functional and safe system that can be used in on-site applications was achieved

Diseño estructural de una nave industrial para mejorar estándares de almacenamiento de concentrados de mineral en la unidad minera Toma La Mano, Carhuaz - 2021

El presente informe se enfoca en el diseño estructural de una nave industrial para mejorar estándares de almacenamiento de concentrados en la unidad minera Toma La Mano, aplicando el Reglamento Nacional de Edificaciones (RNE) y las especificaciones del American Institute of Steel Construction (AISC). Así mismo, se incluye el análisis de la estructura empleando el programa Sap2000 y el plano de estructura general empleando el programa AutoCad. Sin embargo, no se elaborará el diseño de las otras especialidades tales como: instalaciones eléctricas o electrónicas, instalaciones contra incendio, sistema colector de polvo, etc

STR-810: A FORMULATED APPROACH TO CISC SHEAR CONNECTION RESISTANCE AND FLEXIBILITY DESIGN

The design of simple shear connections has been extensively studied by several researchers. The design requirements for ductility and strength of these connections have been established through both experimental and theoretical approaches. However, the current Canadian design guidelines such as the Handbook of Steel Construction published by the Canadian Institute of Steel Construction (CISC) do not provide a formulated approach for the design of shear connections. In addition, the CISC design approach is somewhat out dated when it comes to providing adequate rotational ductility. In this paper, a formulated approach for the design of bolted double angle shear connections considering both strength and ductility is provided. The proposed design approach is discussed and compared with the current design approach outlined by the American Institute of Steel Construction (AISC). The proposed procedure is explained in detail through a design example

Shear Lag Factors for Tension Angles with Unequal-Length Longitudinal Welds

When a tension load is transmitted to some, but not all of the cross-sectional elements of a tension member, the tensile force is not uniformly distributed over the cross-sectional area of the tension member. The non-uniform stress distribution in the tension member is commonly referred to as the out-of-plane shear lag effect. The unequal-length longitudinal welds and the in-plane shear lag effect, however, are not addressed by the current American Institute of Steel Construction (AISC) Specification for the determination of the shear lag factors for tension members other than plates and Hollow Structural Sections (HSS). The purpose of this work is to propose a procedure for the computation of shear lag factors accounting for combined in-plane and out-of-plane shear lag effects on unequal-length longitudinal welded angles. The finite element method using three-dimensional solid elements and nonlinear static analyses accounting for combined material and geometric nonlinearities are conducted in this work to verify the accuracy of the proposed procedure

Computer program simplifies selection of structural steel columns

Computer program rapidly selects appropriate size steel columns and base plates for construction of multistory structures. The program produces a printed record containing the size of a section required at a particular elevation, the stress produced by the loads, and the allowable stresses for that section

Cyclic testing of steel I-beams reinforced with GFRP

Annual Stability Conference, ASC; Pittsburgh, PA; United States; 10 May 2011 through 14 May 2011Flange and web local buckling in beam plastic hinge regions of steel moment frames can prevent beam-column connections from achieving adequate plastic rotations under earthquake-induced forces. This threat is especially valid for existing steel moment frame buildings with beams that lack adequate flange/web slenderness ratios. As the use of fiber reinforced polymers (FRP) have increased in strengthening and repair of steel members in recent years, using FRPs in stabilizing local instabilities have also attracted attention. Previous computational studies have shown that longitudinally oriented glass FRP (GFRP) strips may serve to moderately brace beam flanges against the occurrence of local buckling during plastic hinging. An experimental study was conducted at Izmir Institute of Technology investigating the effects of GFRP reinforcement on local buckling behavior of existing steel I-beams with flange slenderness ratios (FSR) exceeding the slenderness limits set forth in current seismic design specifications and modified by a bottom flange triangular welded haunch. Four European HE400AA steel beams with a depth/width ratio of 1.26 and FSR of 11.4 were cyclically loaded up to 4% rotation in a cantilever beam test set-up. Both bare beams and beams with GFRP sheets were tested in order to investigate the contribution of GFRP sheets in mitigating local flange buckling. Different configurations of GFRP sheets were considered. The tests have shown that GFRP reinforcement can moderately mitigate inelastic flange local buckling.Scientific and Technological Research Council of Turkey; European Commission; Izmir Institute of Technolog

Method for Reducing Warping Stresses in Torsionally Loaded I-Section Members Using CFRP Plates

This paper presents a method for reducing warping normal stresses in torsionally loaded I-section members by utilizing carbon fiber-reinforced polymer (CFRP) plates. The CFRP plates are bonded to the outer surfaces of the flanges with a view to reducing warping normal stresses. The maximum warping normal stress in the flanges of a steel I-shaped member without the CFRP plates is compared to those obtained with the CFRP plates having various thicknesses. It has been found that the use of CFRP plates bonded to both flanges of the I-section result in a substantial reduction of the warping stresses. For the study presented, the maximum warping normal stress without CFRP plates drops down to merely one-third of its value when 0.625-in. thick CFRP plates are mounted on the outer surfaces of the I-section flanges

Torsional-flexural buckling of unevenly battened columns under eccentrical compressive loading

In this paper, an analytical model is developed to determine the torsional-flexural buckling load of a channel column braced by unevenly distributed batten plates. Solutions of the critical-buckling loads were derived for three boundary cases using the energy method in which the rotating angle between the adjacent battens was presented in the form of a piecewise cubic Hermite interpolation (PCHI) for unequally spaced battens. The validity of the PCHI method was numerically verified by the classic analytical approach for evenly battened columns and a finite-element analysis for unevenly battened ones, respectively. Parameter studies were then performed to examine the effects of loading eccentricities on the torsional-flexural buckling capacity of both evenly and unevenly battened columns. Design parameters taken into account were the ratios of pure torsional buckling load to pure flexural–buckling load, the number and position of battens, and the ratio of the relative extent of the eccentricity. Numerical results were summarized into a series of relative curves indicating the combination of the buckling load and corresponding moments for various buckling ratios.National Natural Science Foundation of China (NSFC) under grant number (No.) 51175442 and Sichuan International Cooperation Research Project under grant No. 2014HH002

Agricultural Product Loads and Warehouse Failures

Two manufactured metal building warehouses loaded with agricultural products failed in service. Inspection revealed considerable damage to the structure and the foundation. The building owner filed suit against the building supplier, the building erector, and the soils testing laboratory whose engineer had designed the foundation. The agricultural product imposed substantial outward lateral pressures on the walls of the structures. Review of the available design documents indicated that these loads had not been accounted for in design. A structural analysis revealed that elements of the structure were underdesigned for the agricultural product loads. In addition, the foundation did not have any slab reinforcement to resist the loads. To prevent similar failures, these loads must be accounted for in design. The steel structure design and foundation design were both deficient. A contributing factor was the lack of communication between the designer of the structure and the designer of the foundation, due to the lack of a single engineer of record to take responsibility for the buildings