Higher Moment Capacity Research Articles

Numerical Investigation of Cold Formed Z Purlins with Lap Bolted Connection

Abstract The main aim of this paper is to investigate the flexural rigidity of lapped cold-formed steel (CFS) purlin connections under monotonic loading, using a numerical model developed with finite element software ABAQUS. The purlins are made up of CFS Z-section, while high strength bolts of diameter 12 mm and grade 8.8 have been used. The test setup consists of simply supported two Z-section that are connected together using overlap connection, where load is being applied at mid span. Furthermore, a parametric study has been conducted to investigate various parameters including, length of lapped connections, thickness, and depth of CFS section and arrangement of bolts, to end up with a total of 15 case specimens. All case specimens were examined in detail in terms of load carrying capacity and deflection characteristics. The results showed that overlap connection is capable of transmitting moment and acts as semi-rigid connection. Moreover, results proved that increasing the ratio of overlap length to beam span resulted in an increase in connection moment capacity. Additionally, decreasing the ratio of lap length to section thickness increases the flexural capacity. Finally, the specimens with bolts in both flange and web at the position of overlap connection were found to have the highest moment capacity.

Reliability measurements of the furniture frames with selected joint types

The reliability was evaluated for frame construction with mortise and tenon (MT), dowel, and non-glued and glued staple joints made of beech wood. The moment capacities of the T-shaped joints were determined under static vertical loads. The MT joint had an average moment capacity of 204 Nm, followed by dowel joints (154 Nm). In staple joints, joint strength increased after gluing. A three-seat sofa frame was defined and theoretically subjected to loads on arm rails, side rails, and back posts. Moment levels on the joint of the frame were obtained by using the stiffness method. To measure the reliability, these moment levels were assumed to be normally distributed with a coefficient of variation of 10%; accordingly, the normal distribution of the data sets was transformed into a normal standard distribution, and then, the reliability of each joint on the frame was obtained by using probabilistic approaches. MT joints were found to have the highest moment capacity and, correspondingly, the highest reliability (99.99%). Gluing the staple joints increased the strength, so their reliabilities were increased. In designing frame construction, the critical joints should be determined, and then, the joinery system with the higher reliability should be used.

Flexural Performance of Splice Connections in Cross-Laminated Timber

This study demonstrates the moment resistance performance of various splice connections of cross-laminated timber (CLT) subjected to flatwise bending. A total of 33 samples in two groups (half-lapped and single-splined) were tested under four-point bending. The influence of fastener types on the half-lapped connections was investigated. Additionally, different lap lengths were considered to understand the influence of lap length on different fastener types. Steel plates with two different thicknesses and plywoods were attached with bolts onto the bottom face only to make the single spline connections. Additionally, plywoods were attached to the CLT members in two ways: (i) with the bolt only and (ii) glue plus bolts. The effect of bolt diameters on the spline connections was also examined, and the connections were tested along both the major and minor axes. To determine the characteristic values of the resistance properties, a statistical analysis was carried out following EN 14358:2016. The results indicate the bolted lap connections experience plastic deformations, whereas the screwed lap connections exhibit relatively linear behaviour until failure. The bolted and screwed lap connection with a lap length of 100 mm showed 39% and 33% higher moment capacity, respectively, than that with a 75 mm lap length. Additionally, the rotational rigidity and ductility of the lap connections increase with the increase in lap length. Irrespective of lap lengths, the bolted lap connections show higher moment capacity, support rotation and ductility, but lower rotational rigidity than screwed lap connections. An increase in bolt diameter increases moment capacity but decreases rotational rigidity. Compared to the plywood spline connections, the steel spline connections showed approximately 24%, 5% and 73% higher moment capacity, rotational rigidity and ductility, respectively. Additionally, the plywood spline connections without glue performed better than glued connections. Overall, compared to the half-lapped connections, the single-spline connections showed better performance.

Centrifuge modelling of root–soil interaction of laterally loaded trees under different loading conditions

Understanding the stability of trees under lateral loads arising from natural hazards (e.g. extreme weather and debris flows) is important, as fallen trees can become a potential threat to life and infrastructure. Two 1 : 20 scale three-dimensional printed analogue root system models, with architectures from field-surveyed root architecture data, were used to simulate the push-over behaviour of trees in silty sand under different conditions in the centrifuge. The peak overturning moments obtained were verified against data from field winching tests. Horizontal roots orientated in the loading direction and the central taproot complex contributed most to the overturning resistance. Increasing soil matric suction due to a lowering of the water table, increasing the loading rate and considering the presence of the fine root fraction all resulted in higher moment capacity and rotational stiffness of the root systems. The overturning behaviour was ductile in fully saturated soil and more brittle in partially saturated cases, with more root breakages in the windward horizontal roots and the taproot complex in the latter. These results suggest that it is important to measure the groundwater conditions when conducting winching tests and demonstrate a connection between soil effective stress, total root breakage area and peak moment resistance.

Experimental Testing and Analytical Modeling of Glulam Moment Connections with Self-Drilling Dowels

An experimental and analytical study on rotational behavior of glulam beam-column moment connections with self-drilling dowels (SDDs) is conducted. Connection properties including strength, stiffness, ductility, and energy dissipation were experimentally evaluated by testing seven full-scale connection specimens with and without self-tapping screw (STS) reinforcement along timber perpendicular to grain. All the connections showed high initial stiffness and high moment capacity when compared with the test results of bolted connections reported in the literature. The unreinforced connections had relatively low ductility due to timber splitting despite the increased fastener edge distance. The STS reinforcement effectively reduced the timber splitting tendency and encouraged the yielding of more SDDs, leading to slightly increased moment capacity, but significantly improved ductility. A modified analytical model (MAM) is then proposed to predict strength and rotation of the SDD moment connections based on force and moment equilibrium of the glulam members. Improved prediction accuracy is achieved for the SDD moment connections when compared with the past analytical methods.

Experimental Study on the Flexural Behavior of Concrete-Filled Steel Box Slabs

Different to conventional reinforced concrete or steel material, a new type of concrete-filled steel box slab has been proposed by effectively integrating the combined benefits of both steel and concrete. By filling concrete, this type of slab could avoid the local bucking of steel plate and then could provide a high moment capacity. Therefore, this study aims to investigate the flexural behavior of concrete-filled steel box slabs through testing seven specimens and characterize their failure characteristics, stress distribution and ultimate moment capacity. A comprehensive parametric study focuses on the influence of the steel plate thickness, the stud and stiffening plate on the slab flexural behavior. The results show that concrete-filled steel box slabs had a high moment capacity and good ductility. The thickness of the steel plate had a significant influence on the moment capacity of the specimen. The stud led to the reduction of the moment capacity of the slab. The stiffening plate effectively improved the flexural behavior of the specimen. Moreover, a calculation method was formulated to describe the moment capacity of the slab and compared with experimental results. The results show that the proposed method for the moment capacity of the slab was conservative and reasonable.

Experimental study on the flexural behavior of flat steel – concrete composite beam

In this study, a new type of composite beam named flat steel – concrete composite beam is suggested for the rapid development of assembly structures. Experiments were performed on seven flat steel – concrete composite beams and one traditional steel–concrete composite beam to investigate their flexural behaviors. The failure mode of bending-shear fracture for the flat steel – concrete composite beam is found while the traditional steel–concrete composite beam fails by compression-bending fracture. The plane cross-section assumption is applicable to the flat steel – concrete composite beam. Compared with the traditional steel–concrete composite beam, the flat steel – concrete composite beam exhibits higher flexural stiffness, higher moment capacity, and higher ductility capacity. Based on the design theory of the traditional steel–concrete composite beam, simplified models for estimating the flexural stiffness and ultimate moment capacity of the flat steel – concrete composite beam are proposed, and they agree well with the test data.

Seismic performance of fire exposed steel welded WUF-W and RBS connections

Strength properties of structural steel are reduced when exposed to fire above temperature 600°C. A widely used general rule is that if the steel members in the building frame are reasonably straight with no visible distortion after a fire event, it can be reused. If these members are accepted for reuse with minor or no repairs, then the performance of steel members with a high-temperature fire exposure under a future earthquake event should be known. This study investigated the cyclic response of fire exposed steel Welded Unreinforced Flange Web (WUF-W) and Reduced Beam Section (RBS) welded connections. The results showed that fire exposed steel connections are vulnerable to earthquake loading if they are reused with minor or no repairs. When the performance of connections was compared, it was understood that the usage of RBS connection provides high safety, whereas WUF-W connection has the high moment capacity and energy dissipation capacity.

The Behavior of Reinforced Concrete Members with Section Enlargement Using Self-Compacting Concrete

This paper presents the experimental results of section enlargement effects on prismatic reinforced concrete members. 125 by 200 mm reinforced concrete members with a compressive strength of 20.3 MPa reinforced with D12 steel bars having a yield stress of 335 MPa situated in the tension and compression area, were produced. Two specimens were prepared, the first functioning as the control element and designated as the Control Beam (CB). The second strengthened with a section enlargement using Self-Compacting Concrete (SCC) marked as the Strengthened Beam (SB). The SCC had a 28-day compressive strength of 23.9 MPa. The dimensions of the enlarged beam were 200 by 300 mm. The two specimens CB and SB were tested with a two-point loading system. Based on the tests data, the load–displacement and moment–curvature relationships characterizing the beams were generated. From the results it was concluded that the enlargement affected the load-carrying capacity and stiffness positively. The SB member had a six times higher moment capacity, while the stiffness performance was enhanced seven times when compared to the CB specimen. On the other hand, it was also demonstrated that the ductility of the SB decreased as a consequence of the increase in span-to-depth ratio. The study was expanded based on the rational analyses to evaluate the influence of the additional tensile steel and concrete strength ratio of the enlarged section. Copyright © 2020 Praise Worthy Prize - All rights reserved.

Castellated and common cruciform steel columns under axial and lateral cyclic loading

A numerical study has been done on the strength and hysteresis behavior of castellated and common cruciform steel columns under axial and lateral cyclic loading. The main feature of the castellation method is to make the I-sections stiffer by increasing the web height and reaching the higher moment capacity from the initial axis of the same weight of plain webbed members, and optimizing the use of heavy and costly constructional steel material and providing access to appropriate services. The effect of types of steel sections, web and flange boost of steel section, and length variations of specimens have been investigated and deformation, bearing capacity, hysteresis loops, ductility, and energy dissipation capacities have been discussed. Finite element analysis is performed based on initial geometric imperfection and geometric nonlinearity. The results of finite element analyses are close to the experimental results and showed that load carrying capacity of castellated cruciform steel columns was significantly higher and more suitable than common cruciform steel columns. Numerical results show that castellated cruciform steel columns have higher shear strength, good ductility and excellent energy dissipation capacity compared to conventional cruciform steel columns. The study evidenced that CPE steel sections can be used in seismic region. This study could provide a preliminary review for practical engineering applications and design specification for CPE steel sections.

Experimental and analytical analysis of moment-resisting connections with glued-in rods

Abstract The advances of timber engineering in the field of tall buildings raised a need for high performance connections that can accommodate increased demands due to higher loads and longer spans. A semi-rigid connection with glued-in rods was designed to fulfill these requirements. Moment-rotation behavior of this connection was investigated in a series of quasi-static cyclic tests. A moment-resisting connection was established between timber columns and steel base plates. Three different timber products, including hardwood and softwood species, and two different rod diameters were used. The columns were subjected to shear force and bending, to simulate the loading conditions of a column in a frame under lateral loads. The tests were performed with increasing rotation demand on the column until the failure. The connections provided high moment capacity and rotational stiffness. All of the tested specimens demonstrated ductile response, while the connections with hardwood performed especially well. No strength degradation was observed in multiple cycles, therefore the hysteretic energy dissipation was significant in cycles with high target displacement. The nature of the connection response was studied in detail and an analytical model was developed to describe the relationship between the moment and the rotation at the column base. The model is capable to predict the envelope of the cyclic response and corresponds well to the experimental results.

Utilizing Poppy Husk-based Particleboards as an Alternative Material in Case Furniture Construction

Particleboard can be defined as a wood-based panel produced under pressure and heat with the inclusion of wood particles or other lignocellulosic materials and an adhesive. The need for alternative resources to replace wood raw material has emerged. Poppy husk biomass might have a value-added opportunity, and it is possible to produce particleboards from poppy husk and other softwood species. In this study, moment capacities of L-type corner joints fabricated from poppy husk-based particleboards, which are expected to be an alternative material for case furniture, were investigated. For this purpose, particleboards with five different ratios of poppy husk (P1, P2, P3, P4, P5) were produced, and then L-type corner joints were prepared. Corner joints were connected to each other with two different joint techniques (screwed, minifixed). Specimens were tested under static tension and compression loads, which are the loads commonly experienced by joints during service. According to the results, joints constructed from P5 and connected with screws had the highest moment capacity, whereas joints constructed from P1 and connected with minifix had the lowest moment capacity. In conclusion, from a technical point of view, poppy husk-based particleboards could be utilized in case furniture manufacturing for applications that are not overstressed.

Built-Up Cold-Formed Steel Beams with Corrugated Webs Connected with Spot Welding

Corrugated web girders emerged in the past two decades. Their main advantages consists in the possibility to use slender webs avoiding the risk of premature local buckling. Consequently, higher moment capacity might be obtained increasing the beam depth with really thin webs, which are stiffened by the corrugations. Increased interest for this solution was observed for the main frames of single-storey steel buildings and steel bridges. A new solution was proposed at the Politehnica University of Timisoara, in which the beam is composed by a web of trapezoidal steel sheet and flanges of back-to-back lipped channel steel sections. This solution uses self-drilling screws for connecting flanges to the web and to ensure the continuity of the web as seam fasteners. Starting from this new technological solution the paper extends and investigates the use of spot welding as seam fastening to build the web, in order to increase the degree of automation of fabrication. Experimental work of specimens in shear having two or three layers of steel sheets connected by spot welding will be presented. The results will be implemented on a numerical model in order to study the behaviour of the beams presented above.

Performance Evaluation of Midply and Standard Corner Joints of Wood Portal Frames

AbstractExperimental results to determine the moment-resisting capacity of wood portal frame corner joints are presented in this paper. Two types of corner joints (standard and MIDPLY) were tested with different configurations. An L-shaped corner joint including a narrow braced wall segment and header was used as a test specimen. A total of 37 corner joints were tested. Test results showed that the installation of metal strap or the adding of exterior oriented strand board (OSB) sheathing, while using high-density wood product (LVL, LSL) as header increased the moment-resisting capacity of corner joints. Furthermore, the MIDPLY corner joint had higher moment capacity than the standard corner joint. The moment-carrying capacity of corner joints could be further increased by applying fiber-reinforced polymer (FRP) on top of exterior OSB sheathing. A detailed finite element (FE) model of a corner joint is presented. The FE model predictions correlated well with the experimental results.

Effect of Joint Technique on Moment Capacity of L-Type Furniture Corner Joints for Case Furniture Constructed

In this study, effects of joint technique and material type on moment capacity of case furniture “L” type comer joints under diagonal tensile and compression loads was aimed to determine. The specimens were prepared from 18 mm thick particleboard (PB), oriented strandboard (OSB), okoume (Aucoumea klaineana) plywood (OKP), medium density fiberboard (MDF), particleboard (YLLAM) and medium density fiberboard (MDFLAM) surfaced with synthetic resin sheet. Joining was made two different techniques which are dowel and dado – rabbet joints. Polyvinyl acetate adhesive was utilized in all joints. A total of 240 specimens were prepared, 120 specimens were tested under tension loads, remaining 120 were tested under compression loads including 6 material types, 2 joint techniques, 10 replications and 2 loading types. At the end of the tests; okume, plywood specimens are given the highest moment capacity under both tension and compression loads among the materials. In the case of joint techniques; dowel joints were given the best results under tension while the dado-rabbet joints were given the best results under compression