Cross-Laminated Timber (CLT) combines layers of dimension lumber in alternating grain direction to form a mass timber panel that can be used to create entire wall, floor and roof elements. The viability of CLT as an element to resist lateral forces from racking has been of great interest (Dujic et al. 2004, Blass and Fellmoser 2004, and Moosbrugger et al. 2006). However, most research to date has been conducted on full-scale wall panels connected with proprietary fasteners according to European Test Methods. Little research has focused on non-proprietary connections, including nails, bolts and lag screws. The behavior of CLT full-scale wall panels is dependent upon the individual connection properties including the panel-panel connections between adjoining CLT panels within the wall. The purpose of this research is to evaluate the behavior of three small-scale CLT connection configurations using non-proprietary fasteners. Three different connections -LVL surface spline with lag screws, half-lap joint with lag screws, and butt joint with a steel plate fastened with nails - were tested in both monotonic and cyclic tests. In all, 30 connection tests were conducted, with 15 monotonic test and 15 cyclic tests. Connection strength, stiffness, and ductility were recorded for each connection. Experimental values were compared to National Design Specification for Wood Construction, or NDS (AWC 2012) predictions for connection strength. Nailed steel plate connections yielded much greater loads and behaved in a more ductile manner than did the lag screwed connections. The surface spline and half-lap connections often failed in a catastrophic manner usually due to splitting of the spline and fastener failure. Experimental results were generally lower than predicted by the yield models for the surface spline and steel plate connections. The half-lap connection resulted in higher experimental results than predicted. A discussion of the connection strength for materials with a non-homogeneous grain direction is also included. / Master of Science

This thesis introduces an approach for modeling the monotonic and cyclic response of cold-formed steel framing screw-fastened connections in commercial finite element programs. The model proposed and verified herein lays the groundwork for seismic modeling of cold-formed steel (CFS) framing including shear walls, gravity walls, floor and roof diaphragms, and eventually whole building seismic analysis considering individual fastener behavior and CFS structural components modeled with thin-shell elements. An ABAQUS user element (UEL) is written and verified for a nonlinear hysteretic model that can simulate pinching and strength and stiffness degradation consistent with CFS screw-fastened connections. The user element is verified at the connection level, including complex cyclic deformation paths, by comparing to OpenSees connection simulation results. The connection model is employed in ABAQUS shear wall simulations of recent monotonic and cyclic experiments where each screw-fastened connection is represented as a UEL. The experimental and simulation results are consistent for shear wall load-deformation response and cyclic strength and stiffness degradation, confirming the validity of the UEL element and demonstrating that light steel framing performance can be directly studied with simulations as an alternative to experiments. / Master of Science

This research has been aimed to introduce larger moment carrying connections for any type of buildings, in particular the metal building industry. A total of four connection configurations, namely eight-bolt extended four wide, eight-bolt extended stiffened, six bolt flush unstiffened and twelve bolt extended unstiffened, have been investigated. The last two configurations are proposed whereas the first two configurations have been tested before, but the design procedures need to be validated against the test results. Design procedures, namely yield line analysis and bolt force models, were proposed to calculate moment capacity for end-plate yielding, moment capacity at bolt rupture with prying action and moment capacity at bolt rupture without prying action. The calculated values from these procedures were compared with the values obtained from the experimental test data available (whether from the literature or from this testing program). The experimental data from already tested configurations, eight-bolt extended four wide and eight-bolt extended stiffened, was analyzed. It was concluded that for the eight-bolt extended four wide configuration, the experimental values matched with the calculated values. For the eight-bolt extended stiffened configuration reasonable match was found between the experimentally obtained data and theoretically calculated values only for shallower depths. Hence, it was concluded that two deeper tests need to be performed for this configuration. A full-scale testing program was conducted for ten specimens covering three configurations. The two new configurations (six bolt flush unstiffened and twelve bolt multiple row extended unstiffened) were designed for a shallow and deep beam depth and the behavior of each depth observed for a thin end-plate and a thick end-plate respectively (four tests for each configuration). Also, two deep beam tests, one each for thick and thin plate behavior, were done for the eight-bolt extended stiffened configuration. Based on the comparison, it was determined whether the predicted values were in reasonable agreement with the experimental values or not. The design procedures for both the new configurations appear to be validated for a range of design parameters. The calculated moment capacities for bolt rupture, based on the nominal material properties, were found to be safe when compared with the experimentally obtained moments. The calculations for end-plate yield moments was within ±10% of the experimental yield moment. Also, for the deep tests for eight-bolt extended stiffened the yield line analysis seems to be a valid model and the bolt force model appears to be safe in comparison to the experimental values. / Master of Science

This thesis presents the results of testing to determine the significance of the group action factor at the 5% offset yield and capacity of single-shear bolted wood connections loaded parallel to grain. The single and multiple-bolt connections tested represent common connection geometries used in wood construction in the United States. The results of both monotonic and cyclic loading of connections are presented. Monotonic test data was used to determine an appropriately scaled CUREE Displacement Controlled Quasi-Static Cyclic Protocol. Overall, one hundred and eighty connections were tested using this cyclic protocol based on data obtained from thirty-three monotonic tests. Tested assemblies had geometric variables that include number of bolts per row, number of rows, bolt diameter, and side member material. In addition, the main and side member material and thickness were designed to produce three of the four major connection yield modes as defined by the 1997 National Design Specification for Wood Construction (AF&PA, 1997). Results from this research address the need for adequate spacing of bolts in a row to control the brittle connection behavior that directly affected the group action factor at capacity. / Master of Science

Wood pallets are heavily used throughout the United States and the World to transport, store, and protect goods. During a lifecycle, pallets typically experience various stresses from warehouse storage racks, materials handling equipment, and floor stacking situations. The components within the pallet interact to withstand load and impact forces. Every year product damage and human injury/death result from improperly designed pallets, non-reliable packaging systems, and careless materials handling methods. In use wood pallets are exposed to a variety of loads and support conditions. This research investigates the effect of different pallet designs and support conditions on pallet stiffness. Uniform loads were applied to pallet designs containing thick or thin components and three, four, or five non-notched and notched stringers. The pallets were supported using racked across the length, racked across the width, fork truck tine, and floor stack support conditions. Structural analysis was used to determine the test loads for each pallet bending test. Pallet deflections were measured in specific locations for each bending test. Pallet test results indicated that heavy duty pallets are 6.5 times stiffer than light duty pallets tested in the racked across width (RAW) support condition. Non-notched pallets tested are 51% stiffer than notched pallets in the racked across length (RAL) support condition. Test results also indicated that a wider fork tine support span decreases average pallet stiffness by 29% and 49% for 4 and 5 stringer pallets, compared to 3 stringer. The heavy duty pallets tested are, on average, 48.3% stiffer than light duty pallets in the fork tine support condition. For the notched fork tine support condition, the average pallet stiffness decreased by 29% and 3% for four and five stringer pallets, compared to three stringer. Pallet joints were tested to measure joint stiffness. Joint rotation tests were conducted to determine rotation modulus and joint withdrawal tests were conducted to determine joint withdrawal stiffness. The joint stiffness measurements were used as spring constants in structural analysis based on semi-rigid joint performance. Heavy duty pallet joints were approximately half as stiff (6758 in-lbs/radian) in rotation as light duty pallet joints (12907 in-lbs/radian). Light duty pallet joints were less stiff (44008 lbs/in) in withdrawal than heavy duty pallet joints (57823 in/lbs). The results from this research were used to compare with results from ANSYS (Version 11) structural model estimates. The average predicted error for all pallet bending tests was 13% (heavy duty) and 3% (light duty). / Master of Science

Much previous experimentation related to wood structures has employed monotonic loading to replicate static situations. However, instances of natural hazards have raised interest in the response of structural connections to dynamic loads. This increased interest led the Consortium of Universities for Research in Earthquake Engineering (CUREE) to develop a testing protocol for reverse-cyclic loading, which involves cycling loads through zero in order to test specimens in both tension and compression. With the CUREE testing protocol in place, recent research has been devoted to understanding the effects of reverse-cyclic loading on multiple-fastener connections. Experimentation by Heine (2001), Anderson (2002), Billings (2004) and others contributed to a better understanding of bolted connection behavior under reverse-cyclic loading. However, some questions remained. Billings was unable to consistently produce yield modes III and IV, meaning that her suggested bolt spacing of seven times the bolt diameter (7D) could not be applied to connections subject to these yield modes without further testing. In addition, the work of Anderson and Billings raised questions regarding the proper measurement of bending yield strength in bolts and the relationship between the bending yield strength and the tensile yield strength. These topics are each addressed by this project and thesis report. Results of the connection testing presented in this report can be used in conjunction with the work of Anderson and Billings to critically evaluate the 4D between-bolt spacing recommended by the National Design Specification (NDS) for Wood Construction (AF&PA, 2001). Results of the bolt testing provide a supplement to the search for a reliable method for the measurement of bending yield strength in bolts. / Master of Science

An experimental investigation was conducted to study the extended end-plate moment connections subjected to cyclic loading. Seven specimens representing three end-plate moment connection configurations commonly used in the pre-engineered building industry were used. The connections were designed using yield-line theory to predict end-plate yielding and the modified Kennedy method to predict maximum bolt force calculations including prying action. A displacement controlled loading history was used to load the specimens. The maximum moments obtained experimentally and the experimental bolt forces throughout loading were compared with analytical predictions and finite element model results. The inelastic rotation of connections was calculated and conclusions were drawn on the compliance of these connections with current AISC specifications. / Master of Science

No / This paper describes the experimental results of ten fire tests on medium-scale restrained steel sub-frames to investigate the relative behaviour and robustness of different types of steel joint in steel framed structures in fire. The ten fire tests were designed to investigate the effects of two column sizes (simulating two different levels of axial restraint to the connected beam) and five different types of joint, including fin plate, web cleat, flush endplate, flexible endplate and extended endplate connections. Each test frame, in the form of “rugby goalpost” consisting of one beam and two columns, was connected through two identical beam to column joints. All the steelwork was unprotected except for the top flange of the beam which was protected to simulate the effect of a concrete slab in reducing the beam top flange temperature. The column ends were restrained to examine the effects of axial restraint on the beam and the joints. This paper presents the observations of structural fire behaviour, including joint failure modes and beam limiting temperatures, the development of deflections at beam middle span and axial forces in the joints at elevated temperatures. The main conclusions are: (1) failure (fracture) was observed only in joints when the beam was in catenary action and a variety of joint failure modes were observed which provides valuable data in understanding joint behaviour; (2) the medium-scale steel beams were able to undergo very large deflections View the MathML source without failure; (3) the specimens with stronger connections such as extended endplate reached higher than their limiting temperatures, defined as the beam bottom flange temperature at middle span at which the axial load in the beam returned to zero. But the difference in beam limiting temperatures using different types of joint is small, less than 50 °C; also the column size had little effect (less than 30 °C) on the beam limiting temperature; (4) the beams connected to the larger column experienced less deflections, but higher axial force due to the higher axial restraint to the beam, which led to fracture of the joint components in these tests; in contrast, the lighter columns visibly deformed and formed plastic hinges at the joints, but there was little evidence of connection fracture in the test frames using the light columns; (5) the web cleat connection appears to have the best performance.

Yes / In the current practice, at the end of life of a reinforced concrete struc-ture, it is destructively demolished, and the demolition waste is limited to downcycling and low-tech applications, while the remaining is being landfilled. A recent report showed that construction and demolition waste (CDW) is the big-gest waste stream in the EU by weight, accounting for over 800 million tons in 2018, i.e. around 32% of the total waste generated. This approach is clearly wasteful of energy, jeopardizing the health of individuals and environments and at high cost. However, design for deconstruction (DfD) of reinforced concrete structures would facilitate the future reuse of structural elements at the end of their life, potentially achieving a significant reduction in embodied energy of structures and CO2 emission as well as giving the owners the benefit of retaining the value of their assets. In this paper, recent research developments and practical applications of DfD of reinforced concrete structures are reviewed and key technical issues are dis-cussed. The focus is on connections that should be designed in such a way to al-low demounting of precast reinforced concrete structural elements, including beam/column, wall/wall, column/column and segmental slab connections. The main achievements and progress to date are outlined for each type of dry connec-tions, along with the aspects that still need to be developed. The paper concludes with an outline of challenges in the application of DfD in concrete structures. / This project was supported by the Newton Prize 2020, UK-Turkey award, grant ref number NP2020PB\100026, funded by the Department for Business, Energy & Industrial Strategy. It has also received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 894100. / This paper is from the fib Symposium 2023, Building for the future: Durable, Sustainable, Resilient. 5-7 Jun, Istanbul, Turkey.

Yes / This paper presents an experimental investigation of a new dry connection for reinforced concrete slab elements. Seven full-scale slabs were tested; one slab was monolithic as control specimens, while the other six were assembled using top and bottom steel plates joined by high tensile steel bolts. Two scenarios were proposed for the connection, a simple bolted connection, and a connection with a shear key. The parameters studied were the use of stirrups at the connection section, the step size of the shear key as well as the bolt diameter and number. The test results showed that using a shear key at the assembled section in demountable slabs is more efficient than the simple bolted connection, providing higher flexural stiffness, load capacity, and less deflection. However, increasing the shear key step size improved the flexural performance of the demountable slabs. In addition, adding stirrups to the assembled section enhanced the flexural stiffness and the total load capacity of the demountable slabs. Furthermore, the predictions for the moment capacity and deflection demountable slabs have reasonably good agreement with the experimental results but require additional calibrated data from experiments to be generalized. / Department for Business, Energy and Industrial Strategy (BEIS)