Cross-sections Of Structural Members Research Articles

Effect of Polyester Fiber on Workability Property of High Strength Concrete

The utilization of (HSC) high strength concrete in the construction industry is increasing all over the world because it reduces the cross-section of structural members and increases floor area. High strength concrete can be produced by using high cement content with low w/c ratio, mineral admixtures, and chemical admixture, and with suitable fiber. Nevertheless, in this research, HSC mix was achieved with the use of a special type BASF Master (M)/Polyheed 996 super-plasticizer based on polycarboxylic ether available in the market which reduced the w/c of concrete mixes, albeit attaining adequate workability. Compressive strength, up to 63 Mpa at 28 days, was achieved at slump value 178 mm by utilizing locally available materials like cement, sand, and coarse aggregates with a maximum 1.2% (by weight of cement) dosage of super-plasticizers. HSC has high workability, and to control the workability, different percentages of polyester fiber length 32 mm were also added to HSC. Polyester fiber controls the workability and improves the properties of HSC. There were four mixes designed with polyester fiber. The addition of polyester fiber content was 0.2%, 0.3%, 0.4%, and 0.5% (by weight of cement) in HSC, and the slump value were 153mm, 127mm, 102mm and 76mm respectively. It was observed that the usage of polyester fiber (0.2% to 0.5%) decreases workability by 14% to 57% of HSC. Therefore, it was concluded that increasing the percentage of fiber decreases the slump to the required value.

Seismic performance of Y‐type eccentrically braced frames combined with high‐strength steel based on performance‐based seismic design

SummaryIn the Y‐type eccentrically braced frame structures, the links as fuses are generally located outside the beams; the links can be easily repairable or replaceable after earthquake without obvious damage in the slab and beam. The non‐dissipative member (beams, braces, and columns) in the Y‐type eccentrically braced frames are overestimated designed to ensure adequate plastic deformation of links with dissipating sufficient energy. However, the traditionally code design not only wastes steel but also limits the application of eccentrically braced frames. In this paper, Y‐type eccentrically braced steel frames with high‐strength steel is proposed; links and braces are fabricated with Q345 steel (the nominal yield stress is 345 MPa); the beams and columns are fabricated with high‐strength steel. The usage of high‐strength steel effectively decreases the cross sections of structural members as well as reduces the construction cost. The performance‐based seismic design of eccentrically braced frames was proposed to achieve the ideal failure mode and the same objective. Based on this method, four groups Y‐type eccentrically braced frames of 5‐story, 10‐story, 15‐story, and 20‐story models with ideal failure modes were designed, and each group includes Y‐type eccentrically braced frames with ordinary steel and Y‐type eccentrically braced frames with high‐strength steel. Nonlinear pushover and nonlinear dynamic analyses were performed on all prototypes, and the near‐fault and far‐fault ground motions are considered. The bearing capacity, lateral stiffness, story drift, link rotations, and failure modes were compared. The results indicated that Y‐type eccentrically braced frames with high‐strength steel have a similar bearing capacity to ordinary steel; however, the lateral stiffness of Y‐type eccentrically braced frames with high‐strength steel is smaller. Similar failure modes and story drift distribution of the prototype structures designed using the performance‐based seismic design method are performed under rare earthquake conditions.

Numerical Analysis and Simulation of Spatial Concrete Frames after Fire

In order to analyze the mechanical properties under three conditions of fire-damage, rehabilitation and strengthening of spatial concrete frame structures after fire, two novel numerical models are developed in this paper by dividing the cross-sections of beams and columns into a lot of concrete fibers and steel fibers and dividing slabs into several layers along the direction of the slab thickness based on the concept of the fiber element model and the layered shell element model. These two models can consider the distribution of non-uniform temperature in the cross-sections of structural members and the changing of mechanical properties of fire-damaged, rehabilitated and strengthened materials. Besides, the Analytical System of Fire-damaged Concrete Frame (ASFCF) is established through the secondary development of ABAQUS Software that is completed by the programming language of Python. This system is used to analyze and compare the mechanical responses under three conditions of fire-damage, rehabilitation and strengthening of a multi-story, multi-span spatial concrete frame after fire. The results indicate that ASFCF can properly analyze the mechanical properties under three conditions of fire-damage, rehabilitation and strengthening of spatial concrete frames after fire, and it provides valuable references for assessing the residual mechanical properties and the mechanical properties after rehabilitation and strengthening of global concrete frame structures after fire.

Finite Element Analysis of Concrete Frames after Fire with Fiber Model

In order to analyze the residual mechanical properties of concrete frame structures after fire, a novel numerical model considering the distribution of non-uniform temperature in the cross-sections of structural members and the changing of mechanical properties of materials damaged by fire is developed in this paper by dividing the cross-sections of structural members into a lot of concrete fibers and steel fibers based on the concept of fiber model. Besides, the Analytical System of Fire-damaged Concrete Frame (ASFCF) is established through the secondary development of ABAQUS Software that is completed by the programming language of Python. This system is used to analyze the temperature fields and the nonlinear mechanical performances of a multi-story, multi-span, three-dimensional concrete frame after fire. The results indicate that ASFCF can properly analyze the mechanical properties of concrete frames after fire, and it provides valuable references for assessing the residual mechanical properties of concrete frames after fire.