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

Resistance of Geopolymer, Epoxy and Cement Mortar to Hydrocarbon-Based Synthetic Engine Lubricant, Hydraulic Fluid, Jet Fuel and Elevated Temperatures

Due to routine maintenance of aircraft on the concrete pavement at army airbases, a large part of the pavement surface is often found saturated with different hydrocarbon-based oil, fuel, and fluid. In addition, the pavement concrete is subjected to the aircraft’s exhaust temperature during operation. This study examined the resistance ability of 3 different cementitious materials: (i) epoxy, (ii) fly ash (FA) based geopolymer with various alkali to fly ash (AL/FA) ratios and (iii) Portland cement (PC) mortar under a simulated airfield circumstance. The mortar specimens were repetitively exposed to a mixture of synthetic engine oil, hydraulic fluids, jet fuel and elevated temperatures (175 °C) for 5 months simultaneously. During the exposures, geopolymer and PC mortar both suffered saponification. The degree of saponification of geopolymer samples is found to be highly reliant on the AL/FA ratios. On the contrary, the epoxy mortar was found to be resistant to saponification. It was also found that the PC mortar developed numerous thermal cracks but epoxy and geopolymer did not experience any visual thermal cracks under the same conditions

Behaviour of Parallel Bamboo Strand Lumber under compression loading – an experimental study

This paper investigates the compression behaviour of 18 Parallel Bamboo Strand Lumber specimens. 25 mm × 25 mm square specimens with varying heights and fibre orientations were tested. Test results indicated typical 5-stage failure path, and a 45º failure plane in all specimens when the compression load was applied parallel to the fibres. Specimen height did not affect the ultimate load carrying capacities but showed considerable influence on the initial stiffness as well as the post-ultimate loading regime. Experimental results showed that the deformation ratio and the energy absorption ratio for longer specimens were not affected by fibre orientations

Saponification and scaling in ordinary concrete exposed to hydrocarbon fluids and high temperature at military airbases

The conventional Portland cement concrete (PCC) aprons that house Air Force and Navy aircrafts are reported to experience significant scaling on the surface, which is a serious concern for the safe operation of military aircrafts. The purpose of this study is to investigate the underlying scientific facts for the scaling of PCC aprons at military airbases. An experimental program was developed to replicate the physical and environmental circumstances that prevail in aprons at military airbases. Standard sized PCC cylinders were repeatedly exposed to aviation oils and high temperature, both simultaneously and separately, until surface scaling became obvious. Chemical analyses were conducted on the aviation oils, scaled concrete as well as on the original PCC; analysis results revealed that aviation oils contain ample hydrocarbon compounds to trigger surface scaling at high temperature. When PCC cylinders were repeatedly exposed to aviation oils and high temperature simultaneously, they underwent a saponification process after a couple of cycles of exposure, and rapidly developed scaling on the surface after subsequent exposures. Saponification increased with the increase in numbers of cyclic exposures and consequently resulted in the development of a significant volume of loose fines on the surface of the PCC cylinders. The repeated saponification and deposition of calcium phosphate (salts) at the top layer caused rapid scaling, by acting together. On the other hand, PCC cylinders that were exposed to aviation oils at ambient temperature neither experienced a saponification process nor developed scaling. The influence of w/c ratio on the saponification, scaling and thermal cracking was examined as a part of the current study. The present study reveals a relationship between the depth of scaling and aviation oils’ penetration depth, and the effect of high temperature, microcracks and voids, and their influences on the scaling process of PCC are also reported herein

Design considerations for the long-term behaviour of composite steel-concrete beams

From the 7th International Conference on Steel and Aluminium Structures (ICSAS) -held: Kuching, Malaysia, 13 July 2011

Long-term experiments of composite beams and connections

Composite steel–concrete solutions are commonly used in Australia for floor building applications. In these situations secondary beams are usually connected to primary beams or columns by means of composite web side plate connections, also known as fin or single plate joints, with the slab continuous at the connection. The rigidity of this arrangement can lead to extensive cracking at the joint and to significant compressive forces in the web side plate connection, which can compromise one of the design limit states. In this context, this paper focuses on serviceability limit state and presents the results of two sets of experiments aimed at investigating how the time-dependent behaviour of the concrete affects the response of such joints. The first set included six simply supported specimens subjected to a sustained negative moment with the connection placed at their mid-span. These were used to study the behaviour of the negative moment region of a continuous floor beam in isolation. The second set consisted of a full-scale two-span continuous composite beam with the joint specified at the internal support. The long-term response of these composite members was monitored measuring the changes in deflection, end rotation, strain and slip occurring over time. Design considerations are provided at the end of the paper and it is envisaged that these new experimental data will be useful for the validation and benchmarking of analytical and numerical model