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Damage cases show that during earthquakes, the sharp stiffness mutation of subway station-tunnel junction structures can lead to dislocations at the connections. To address this, shaking table tests were conducted followed by numerical simulations of a typical junction structure with rigid connections. The modeling method was verified based on the test results. Furthermore, numerical models of junction structures with rigid and flexible connections, single stations, and single tunnels were built, and deformation modes and stress distributions were comparatively analyzed. Combining the experimental and numerical results, it is found that there exists an intensive deformation inconsistency between the stations and the tunnels responsible for the junction structures’ dislocation failures. The station operates in both racking and distortion deformation modes when the tunnel undergoes ovaling deformation. The tunnel bends relative to the end wall at the connection. The junction structure with rigid connections is most at risk at the point located at the tunnel section connected to the end wall and near the bottom plate-sidewall joint. With flexible connections, the tunnels integrally translate relative to the end wall, and the stress response of the end wall openings can be larger than those with rigid connections.

This study examined the racking performance of poplar laminated veneer lumber (LVL) frames using bolted steel filling plates to connect beam-column joints, poplar LVL frames using the embedment bars to connect beam-column joints, and frame-shear hybrid walls made of poplar LVL studs and oriented strand board (OSB) sheathing panels. A new design load spreader beam was used on the side of the top of a specimen to apply monotonic and cyclic loadings. It was found that the lateral force resistance, stiffness, and ultimate loads of poplar LVL pure frames with bolted steel filling plate connections and closed rod connections were much lower than those of the poplar LVL frame-shear wall hybrid structure. The highest initial stiffness of the poplar LVL hybrid frame-shear wall was 1.77 kN/mm, which was 24% and 22% lower than that of the conventional shear wall made with spruce-pine-fir studs and OSB or plywood sheathing panels, respectively. The poplar LVL frame-shear wall hybrid structure showed lower degradation in stiffness than the conventional shear wall. The hybrid frame-shear wall structures made of poplar LVL could meet the requirements of Chinese standard; however, diagonal braces were required in use of poplar LVL pure frames.

International audience

This paper presents the results of an experimental campaign investigating the seismic behaviour of full-size cross laminated timber (CLT) wall systems with sound-insulated shear-tension angle brackets. The main aim of the study was to investigate the influence of more and less flexible soundproofing bedding under the CLT wall. The paper shows a comparison of lateral load-bearing capacity, displacement capacity, ductility and stiffness obtained from racking tests on uninsulated specimens and specimens with various types of bedding insulation and levels of vertical load. Moreover, an analytical procedure to estimate the lateral load-displacement response of CLT walls with bedding insulation is proposed. This model is verified by direct comparison to the experimentally determined lateral load-displacement backbone curves. The results show that the elastomeric bedding does not have a significant effect on the bearing capacity of the wall system tested, but it reduces the stiffness and increases the displacement capacity. Due to the large decrease in stiffness, the insulation causes an overall reduction in ductility. The analytical estimation proposed was able to capture the reduction in lateral stiffness and adequately predict the load-bearing capacity.

Timber-framed shear walls are designed to resist the lateral loads on a building from wind and earthquake. Many regions around the world have developed standard test methods for evaluating the performance of timber-framed shear walls. Currently, Australia has no such standard test method for timber-framed shear walls. The aim of this study is to develop a standard loading protocol for evaluating the performance of timber-framed shear walls in Australia that is informed by the concerns of both earthquake engineers and wind engineers. To achieve this aim, the key objective of this study is to compare the performance of a standard timber-framed shear wall under three different monotonic (groups M1, M2 and M3) and four different cyclic (groups C1, C2, C3 and C4) loading protocols according to their respective standards. The number of test panels in each group was three ( 3 ) for a total number of 21 individual tests. Structural performance characteristics of the standard test panel, such as ultimate and yield strength and global stiffness, were found to be strongly dependent on the loading protocol. For example, ultimate strength was lower for test panels subject to monotonic loading (i.e., 5.99 , 6.41 and 6.34 k N / m for groups M1, M2 and M3 respectively) compared to test panels subject to cyclic loading (i.e., 6.70 , 6.73 , 8.03 and 8.11 k N / m for groups C1, C2, C3 and C4 respectively). Internal stiffness was found to be relatively consistent regardless of loading protocol. The higher ultimate and yield performance of group C3 (CUREE protocol) and C4 (Cyclone Testing Station protocol) is statistically significant, at the 5 % significance level, compared to results from all other test methods (i.e., AS1720.1, EN 594, ASTM E564, BRANZ P21 and ISO 16670). Differences in boundary conditions between the loading protocols might explain some of the differences in results; however, this hypothesis is not strongly supported by the evidence. These results are used to inform our recommendations for developing an Australian standard test method for evaluating the structural performance of timber-framed shear walls.

Equivalent linear time history analyses are conducted to calculate the seismic response of various types of cut-and-cover single box tunnels. A finite-element numerical model is calibrated against the results of centrifuge tests. The calculated tunnel responses compare favourably with the measurements. A validated model is then used to quantify the seismic response of box tunnels. The flexibility ratio (F) is illustrated to have a governing influence on the tunnel response. It is shown that the previously developed relationship betweenFand the racking ratio (R) is applicable for a wide range ofFup to 20. It is also shown that an increase inFaccompanies corresponding increase inR, the spectral acceleration in the tunnel lining, and the shear stress along the tunnel lining-soil interface. The thrust in the tunnel lining is also revealed to increase withF, although the calculated value is significantly lower than the pressure on yielding walls. Additionally, the surface settlement is shown to increase with an increase inF.

The goal of this study is to develop a racking model of plasterboard-sheathed timber walls as part of the efforts towards performance-based seismic engineering of low-rise light timber-framed (LTF) residential buildings in New Zealand. Residential buildings in New Zealand are primarily stand-alone low-rise LTF buildings, and their bracing elements are commonly plasterboard-sheathed LTF walls. It is an essential part of performance-based seismic designs of LTF buildings to be able to simulate the racking performance of plasterboard walls. In this study, racking test results of 12 plasterboard walls were collected and studied to gain insight into the seismic performance of plasterboard-sheathed LTF walls. The racking performance of these walls was examined in terms of stiffness/strength degradation, displacement capacity, superposition applicability and failure mechanisms. Subsequently, a mathematical analysis model for simulating racking performance of LTF plasterboard walls is developed and presented. The developed racking model is a closed-form wall model and could be easily used for conducting three-dimensional non-linear push-over studies of seismic performance of LTF buildings.

Accurately determining the transverse shear stiffness of steel storage rack upright frames is essential in calculating the elastic buckling load, performing earthquake design and serviceability checks. International racking design specifications recommend different approaches to evaluate this stiffness. The Rack Manufacturers Institute (RMI) specification conservatively uses an analytical solution based on Timoshenko and Gere's theory while the European (EN15512) and Australian (AS4084) specifications recommend experimental testing to be conducted. Previous studies have shown that Finite Element Analyses (FEA), solely using beam elements, fail to reproduce experimental test results and may overestimate the transverse shear stiffness by a factor up to 25. This discrepancy is likely attributed to the local deformations occurring at the bolted joints. In this paper, a model to capture the transverse shear stiffness of upright frames is developed using shell elements and advanced FEA. Its accuracy is verified against published experimental test results performed on three commercially used upright frame configurations with lip-to-lip bracing pattern. The model accurately reproduces the experimental stiffness, with differences ranging from 2% to 17%. Based on the FE model, the factors contributing to the transverse shear deformation of the frames are quantified and discussed for both lip-to-lip and back-to-back bracing patterns. For lip-to-lip upright frames, results show that the local deformations at the end of bracing members contributes the most to the shear deformation of the frames. For back-to-back upright frames, bolt bending and axial deformation of braces contribute the most to the shear deformation of the frames. Results from this paper would assist the racking industry in improving their products by focusing on the factors influencing the most the behaviour of the frames.

This paper presents an experimental study on the compressive and racking performance of eccentrically aligned dou-gong connections used in Chinese traditional timber structures. Four 1:3.4 scaled specimens were fabricated and tested with static compressive and cyclic lateral loading. The damage modes and load–displacement (or hysteresis) curves of the dou-gong connections as well as the influence of the composite action effect and vertical compression loading were discussed. It was found that the load–displacement curve of an eccentrically aligned dou-gong connection was nearly bilinear and the change of the vertical stiffness took place when the cap block cracked and loosened the lateral constraint on the overturning of the connection. The vertical initial compressive stiffness was nearly 70% of a concentrically aligned dou-gong connection according to a predictive formula established based on concentrically aligned dou-gong connection test results. The initial stiffness, yield load and maximum load of double dou-gong connections were found to be 262%, 332% and 373% of those of a single dou-gong connection, respectively. The composite action from the interlocked straight beams (by shear keys) and infill panel can increase the lateral stiffness by more than 55% and the energy dissipation capacity by more than 70%, though such composite action decreases with the worn out of the contact surfaces of the straight beams and the plastic deformation of the shear keys. The vertical load improved the stiffness and energy dissipation capacity of the connections mostly by the friction force. Specifically, an increase of 120% in the vertical compression load can lead to more than 50% increase in the lateral stiffness and up to 130% increase in the energy dissipation capacity.

The objective of this paper was to experimentally investigate the behavior of structural insulated panel (SIP) walls under in-plane cyclic loading and to test several panel-to-panel connections in order to measure their effect on the behavior of the walls. Each wall was constructed using two SIP panels with one top plate, one sill plate, two end plates, and a panel-to-panel connection. Each SIP panel had a 5.5 in. (14 cm) thick expanded polystyrene core sandwiched between two 4′ × 8′ (1.22 m × 2.44 m) sheets of 7/16″ (1.11 cm) oriented strand board. The top sill plates were split up between each panel in an effort to increase the potential for racking behavior of the walls and, therefore, the relative vertical displacement between the panels. In addition, as a preliminary study, three different steel connector configurations utilizing 26 gauge steel shear panels were considered in an effort to introduce additional ductility compared to more traditional block spline connection. From experimental observation of the wall with the block spline connection and the wall with no connection, the panel-to-panel connection was shown to contribute significant strength and stiffness to the wall system. The walls that were constructed with the first two configurations of the shear panels did not show any significant increase in either stiffness or ductility over the wall with the block spline. These walls also showed a decline in peak strength, which occurred at lower lateral displacements than the peak strength of the typical wall. For both of these cases, the shear panels yielded early and ruptured at the lateral deformation which caused peak load in each wall. The SIP wall implementing the third style of shear panel also did not demonstrate a significant increase in ductility as compared to the standard SIP wall. Despite the initially outlined potential, the preliminary study of implementation of the slit steel shear panels considered in this study did not significantly alter the performance of the conventionally connected SIP walls. Further study with stiff connectors capable of significant ductility prior to fracture would need to be implemented to realize the benefits of increased wall ductility.

In cold-formed steel building construction, cold-formed steel shear wall panels (CFSSWPs) are used as primary lateral load resisting components, that maintain the stability and the integrity of the structure. Traditionally, a CFSSWP constits of a cold-formed steel frame with structural sheeting, such as oriented strand board (OSB), gypsum wall board (GWB), plywood or other, screwed onto it. These type of elements have some unique properties, such as high elastic stiffness, large displacement ductility, etc. On the other hand, as the studs are closely spaced - a value of 60 cm for the spacing is common - only small openings are present, hence transparency is limitted; To increase the transparency of cold-formed steel buildings, which is a tendency in contemporary architecture, load-bearing capacities of glass can be utilised by bracing the frames with glass instead of traditional sheeting. The conventional two-component structural silicone Sikasil (R) SG-500 is considered for the load-bearing cold-formed steel-glass connection. In this research, the racking behaviour of 1.5 m by 3.5 m cold-formed steel frames onto which glass panels are circumferentially bonded on both sides is determined by means of experimental tests. This paper reports about the conducted experiments and the obtained data. From the tests, a value of 32.25 +/- 0.452 kN/m was obtained for the racking strength of the considered hybrid cold-formed steel-glass panels. A comparison with traditional CFSSWPs showed that the hybrid element can obtain similar racking strengths. Therefore, the study revealed the potential of hybrid cold-formed steel-glass elements using structural silicones to provide sufficient in-plane lateral stiffeness and strength.

The diagrid is a framework of diagonally intersecting members that are used in the construction of buildings and roofs. It requires a lower percentage of steel than a standard design. The need for columns and can be obviated by the use of diagrids. Diagonal members in the system carry gravity loads as well as lateral forces. Due to the triangulated configuration of members, internal axial forces arise in the members, in turn minimizing shear racking effects. Diagrid structures are generally used in the construction of high-rise buildings as lateral forces get minimized. The primary goal of the research is the design and analysis of diagrid structural systems for the high-rise buildings. The modeling was done by using PATRAN software and was analyzed using NASTRAN software. The study includes analysis of the representative models of various geometric forms for optimal construction in terms of strength, stiffness, aesthetic appearance, material requirement, and low cost. The investigations also include the study of the optimal cross section of diagrid members. A quasi-static environment and geometric nonlinear analysis are considered in the analysis of diagrid structures.

The aspects regarding the stiffness of the connections between the beams that support the storage pallets and the uprights is very important in the analysis of the displacements and stresses in the storage racking systems. The main purpose of this paper is to study the effects of both upright thickness and tab connector type on the rotational stiffness and on the capable bending moment of the connection. For this purpose, a number of 18 different groups of beam-connector-upright assemblies are prepared by combining three types of beams (different sizes of the box cross section), three kinds of uprights profiles (with a different thickness of the section walls), and two types of connectors (four-tab connectors and five-tab connectors). Flexural tests were carried out on 101 assemblies. For the assemblies containing the uprights having the thickness of 1.5 mm, the five-tab connector leads to a higher value of the capable moment and higher rotational stiffness than similar assemblies with four-tab connectors. A contrary phenomenon happens in case of the assemblies containing the upright profiles having a thickness of 2.0 mm regarding the capable design moment. It is shown how the safety coefficient of connection depends on both the rotational stiffness and capable bending moment.

An extensive parametric numerical study was performed after completed experimental campaign of timber-glass hybrid walls (TGW and TGWE). 36 timber-glass models (TG) with different outer dimensions were built and analysed with a goal to capture the basic response of mechanically tested timber-glass walls and to determine the racking stiffness of the calculated numerical models. Timber frame was modelled using linear beam elements with hinges in all four corners, an IGU was modelled as a multilayer shell and finally a layer of adhesive was modelled with linear and nonlinear springs, which were distributed circumferentially around the edge of IGU and connected onto a timber frame. Normal and shear stiffness coefficients for linear-elastic springs were calculated, while for nonlinear springs a special series of mechanical tests on polyurethane (PU) adhesive was performed since a lack of data available in addition to the desired amount of information needed for the numerical analysis. Uniaxial tension, compression and shear tests were made to obtain the results in form of the load-displacement curve, which presented a direct input for nonlinear normal and shear springs of the mathematical model. For each compression and tension mechanical test three specimens were prepared and tested up to rupture, while a double-lap shear test was conducted using two specimens giving two results each. PU adhesive specimens of the first series had dimensions of 50 mm $$\times $$ 50 mm and thickness of 5.0 mm. Mechanical tests were repeated for two additional thicknesses of PU adhesive, namely 7.0 mm and 9.0 mm. After completed experimental investigation on PU adhesive joint, together 108 numerical models with different external dimensions were analysed in commercial code SAP2000. Having the correct information about the stiffness of the single TG shear wall one can calculate the stiffness of the entire timber-glass building built with such walls.

Centrifuge experiments on seismic performance of relatively stiff underground reservoir structures in dry sand are modeled numerically. The capabilities of numerical simulations with calibrated equivalent linear soil properties in capturing the main features of experimentally measured responses are explored for both low and high amplitude earthquake motions. The scattering effects of the centrifuge container boundaries are also investigated by modeling the same soil deposit resting on an elastic bedrock and extending infinitely laterally, using the domain reduction method. It is observed that the calibrated equivalent linear soil models perform well in predicting accelerations, racking, and bending strains on the buried structure, even for high amplitude motions for which significant soil nonlinearity is expected. While not as accurate, the seismic lateral earth pressures predicted with these models are in fair agreement with direct measurements made with tactile sensors. The mismatches in earth pressures are likely due to local nonlinearities of soil and frictional contact, which were absent from the numerical models. It is also observed that the scattering effects of the container boundaries become more significant closer to the soil surface, and their characteristics are seen to depend on both the side boundaries and the embedded structure's stiffness.

Steel storage racks, commonly assembled from cold-formed steel profiles, are braced in the cross-aisle direction, where bracing members are typically bolted between two uprights forming an “upright frame”. Especially for high-bay racks and racks supporting the building enclosure, accurately determining the transverse shear stiffness of upright frames is essential in calculating the elastic buckling load, performing earthquake design and serviceability checks. International racking specifications recommend different approaches to evaluate the said transverse shear stiffness. The Rack Manufacturers Institute (RMI) Specification conservatively uses an analytical solution based on Timoshenko and Gere's theory while the European (EN15512) and Australian (AS4084) Specifications recommend testing to be conducted. Previous studies have shown that Finite Element Analyses (FEA), solely using beam elements, fail to reproduce experimental test results and may overestimate the transverse shear stiffness by a factor up to 25. This discrepancy is likely attributed to the local deformations occurring at the bolted joints. In this paper, a commercially used upright frame configuration has been modeled using shell elements in FEA and the response is verified against published experimental test results. A good correlation is found between the FEA and test results, concluding that shell elements are able to fully capture the behaviour of the upright frame. Future studies on the use of the FE model are also presented.

Centrifuge experiments were conducted to investigate the seismic response of stiff-unyielding buried reservoir structures with varying stiffness in medium-dense, dry sand. The results of these tests were used to evaluate the predictive capabilities of Class-C and C1, nonlinear, finite element analyses of the seismic response of these relatively stiff buried structures. All simulations were performed in two dimensions using the pressure-dependent, multi-yield-surface, plasticity-based soil constitutive model (PDMY02) implemented in OpenSees. For Class-C simulations, model parameters were calibrated based on the available cyclic simple shear tests on the test soil. For Class-C1 simulations, the same soil model was used along with user-defined modulus reduction curves that were corrected for soil's implied shear strength. The use of shear modulus reduction curves, which modeled a softer soil response compared to PDMY02, generally improved the prediction of site response in the far-field as well as seismic racking deformations, earth pressures, and bending strains on the structures. Experimentally, the dynamic thrust, racking, and bending strains on or of the model structures were shown to primarily peak near the strain-dependent fundamental frequency of the site, regardless of the fundamental frequency of the structure itself. This influence in addition to other important response parameters were captured reasonably well by Class-C1 simulations, with residuals ranging from −0.25 to 0.2.

In the current paper a simple mathematical model with a fictive diagonal for a quick and accurate determination of the racking stiffness of composite timber-framed wall elements is developed. The stiffness of the timber-framed wall is determined through the analytical calculation of the wall element, taking into account the bending and the shear flexibility of the composite wall element, the flexibility of the fasteners between the timber frame and the sheathing board along with the flexibility of the tensile and compressive support at the foundations. The model furthermore allows for consideration of the walls with door and window openings in addition to that of tensile cracks appearing in the fibre–plaster sheathing boards, with the stiffness of the wall element being reduced. By varying the fictive diagonal cross-section of the numerical model according to the presented facts, the appropriate stiffness of the timber-framed wall can be obtained and used in the 3D static model. The model is suitable for any three-dimensional modelling with the analysis of the lateral load impact (wind, earthquake) on the building being carried out by using simple 3-dimensional FEM software, which is extremely useful for engineering application.

The mechanical behaviour of timber frame shear walls subjected to in-plane forces has been investigated through full-scale tests. Eleven monotonic and 11 cyclic tests were performed on full-scale shear walls, each 2·5 m high and 2·5 m long. Different variables were changed during the tests as follows. Different vertical loads were applied, different angle brackets and hold-downs were used and different sheathing panels were connected to the timber frame. Also, the influence of openings was investigated. Furthermore, two walls with non-structural finishing were tested in order to correlate the inter-storey drift with the level of damage. This paper (part 2) reports on a comparison between different test results, permitting evaluation of the influence of each variable on the stiffness and the resistance of the walls. Moreover, the theoretical formulae presented in a companion paper (part 1) were compared with the outcome of the tests, and good agreement was found. The racking resistance predicted by Eurocode 5 was also checked using the data obtained from the tests.

As revealed by the collapse of the Daikai Metro station during the 1995 Kobe earthquake, underground structures are not immune to seismic loading. Shanghai Metro operates 16 lines of 676 km length, comprising 413 underground stations. An additional 1000 km with 600 underground stations are planned for the next 20 years, calling for improved understanding of their seismic response. This paper studies the seismic performance of a typical 2-storey, 3-span Shanghai Metro station in soft soil, combining shaking table testing and numerical modelling. Notwithstanding scale effects, shaking table testing is performed to allow detailed simulation of the complex structural system of the station. The structure is modelled using granular concrete and galvanized steel wires to simulate the RC prototype. To remedy the problem of scale effects, synthetic model soil (a mixture of sand and sawdust) is used, along with similitude relations derived considering dynamic equilibrium. The properties of the synthetic model soil are adjusted to satisfy similitude; target stiffness and density are attained by adjusting the mixture proportions. To quantify the transferability of the results to prototype scale, the experiments are simulated with nonlinear finite elements (FE), modelling the synthetic model soil with a kinematic hardening constitutive model, calibrated against resonant column and direct shear tests. The FE model is shown to compare adequately well with the shaking table tests. The validated FE model is used to predict the seismic response of the prototype, thus allowing indirect transfer of the results from model to prototype scale. The model in prototype scale is calibrated for the real soil layers against in situ (down-hole) and laboratory (resonant column) tests. Moving from model to prototype scale, the racking deformation remains qualitatively similar. The racking drift is reduced by 50% going from model to prototype scale, which is partly due to scale effects, but also related to differences between the idealized soil of the experiments and the multiple soil layers encountered in reality. The maximum bending moment also reduces by 30% going from model to prototype scale. The base of the lower-storey columns is proven to be the most vulnerable section, as was the case for Daikai.

The stiffness distribution of an atrium subway station with zero buried depth spatially varies when columns in the first level underground are removed and lateral beams replace the middle part of the floor slabs. It is pertinent to the mechanism and effects of multidirectional ground shaking on such structures. In this paper, the response characteristics of an atrium subway station subjected to bidirectional ground motions in a shaking table test were presented. Under horizontal seismic shaking, the structure, without a soil cover, showed a non-negligible rocking mode coupled with the well-known racking of the structure. Under vertical seismic shaking, the lateral beams, without supporting columns, demonstrated an obvious bending vibration associated with an overall up and downward movement. Overall, the horizontal component contributed more to dynamic response of the structure than the vertical component.

This paper provides a quantitative assessment of the racking performance of partially anchored timber framed walls, based on experimental tests. A total of 17 timber framed wall specimens, constructed from a combination of materials under different load configurations, were tested. The experimental study was designed to examine the influence of a range of geometrical parameters, such as fastener size and spacings, wall length, arrangement of studs and horizontal members, as well as the effect of vertical loading on the racking strength and stiffness of the walls. The experimental results were then compared with results obtained from design rules, as given in the relevant European standards, to determine the racking performance of the walls, and are discussed in the paper.

In order to design energy-efficient timber-frame buildings with enlarged fixed glazing, mostly placed in the south-oriented external wall, it is of primary importance not only to take advantage of a high possible solar potential to heat the building, but also to assure a horizontal stability of such timber-glass structures. The paper presents the outcomes of a large experimental research on timber-glass wall elements where glass panes are directly bonded to the timber frame, which results in a load-bearing and visually interesting wall element suitable for lightweight timber structures. Three different types of adhesives (silicone, polyurethane and epoxy) were used with two different bonding line conditions to obtain an optimal type of connection which will be in praxis suitable for wall elements subjected to either monotonic or dynamic load impact. In the presented experimental research, strain measurements were supported by additional numerical FE analysis. Only such detailed studies and analyses could lead to the complete understanding of the specimen’s failure mechanism. The failure mechanism depends primarily on the type of adhesive and the type of bonded joints. These two parameters have a decisive impact on the element ductility and are important for further research. The analysis of the measured and calculated values confirmed the predictions that the stiffness and load-bearing capacity of timber-glass wall elements crucially depend on the interaction between the wooden frame and glass, which in turn is a function of the flexibility of the particular type of adhesive used.

The article deals with a problem of racking strength and stiffness of timber based two-by-four wall systems insulated with polyurethane foam. There are racking strength and rigidity tests described in the main part of the work. Results of performed tests are compared to calculation of the racking strength according to national standard.

Finger-joined lumber studs are considered equivalent to, and can be used interchangeably with, unjoined lumber of the same grade in residential construction in Canada. However, there have been concerns expressed by engineers and users that there is no data available on the mechanical performance of shearwalls built with finger-joined studs to support this equivalency. This study was intended to address this information gap. Two groups of finger-joined studs were fabricated using ‘No. 2 or better’ grade spruce-pine-fir (SPF) lumber and a heat resistant polyvinyl acetate (PVA) adhesive. One group had 2–3 joints per stud, while the second group had 5–6 joints per stud. A control group of unjoined ‘No. 2 or better’ grade SPF lumber was sampled as a reference for comparison between groups. The stud dimensions were 38 mm × 89 mm × 2.44 m. Sheathing used was oriented strand board (OSB) panels with dimensions of 1.22 m × 2.44 m × 12.5 mm. The stud frame was fastened using 12d common wire nails and the sheathing was fastened to the stud frame using 8d common wire nails. A total of 12 shearwall test specimens of dimensions 2.44 m × 2.44 m were fabricated and tested. Test results showed that there was no statistically significant difference in the mechanical performance in terms of peak racking load and stiffness between shearwalls containing finger-joined studs (up to 5–6 joints) and shearwalls containing unjointed studs. The failure mode for each test wall was a combined sheathing nail withdrawal and sheathing nail head pull through. This study provides confirmation that finger-joined studs made using the PVA adhesive in this study could be deemed to be equivalent to unjoined studs in fabrication of shearwalls.

In the paper the results of experimental tests carried out on double-sided semi-rigid beam-to-column joints applied in the typical pallet racking systems are presented and discussed. The applicable European design standard EN 15512 “ Steel static storage systems. Adjustable pallet racking systems. Principles for structural design” obliges to perform experimental research as part of a complementary process of designing this type of structures. At the same time, the test procedure described in the said document is defined only for single-sided joints, whereas in typical pallet racking systems, double-sides joints are dominating, due to the way the systems are constructed. Having in mind the above mentioned reasons, the series of tests for double-sided configuration of beams have been carried out, based on standard provisions, as well as other standardization and advisory documents of a similar nature. The obtained results of stiffness and bending moment capacity for double-sided joints have been compared to the findings of experiments performed in the past for single-sided joints only, presented in some earlier publications, e.g. [4] .

A new method to assess the raking performance of Platform timber framed walls, is provided in this study: each component of the unit wall assembly is assumed as rigid, hence allowing to drastically reduce the overall number of DoFs involved within the model. The timber frame in particular, is modelled as a mechanism, having only two DoFs (regardless of the number of studs) corresponding to the horizontal and rotational displacements of the header beam. For a given imposed horizontal displacement Δ h , the corresponding racking load P ( Δ h ) is computed by numerical relaxation, allowing to consider a continuous function to represent the load-slip curves of the connections. A comparison of the numerical analysis against laboratory test results is provided, showing the method’s capability in predicting the raking strength of the wall, despite the assumed reduced number of DoFs.

Observations from past earthquakes have shown that subway tunnels can suffer severe damage or excessive deformation due to seismic shaking. This study presents the results of finite element analyses on subway tunnels installed in normally consolidated clay deposits subjected to far-field ground motions. The clay strata were modelled by a hyperbolic-hysteretic constitutive model. The influences of three factors on the seismic response of the clay-tunnel systems were examined, namely ground motion intensity, tunnel wall thickness and clay stiffness. Furthermore, the computed racking deformations of the tunnel were compared with several analytical estimations from the literature, and the relationship between racking ratio and flexibility ratio for rectangular tunnels installed in normally consolidated clay deposits was proposed. The findings may provide a useful reference for practical seismic design of tunnels.

Compared to bridges, underground structures are inappropriately regarded as less crucial components of road infrastructure in view of their supposedly low seismic vulnerability. The literature indicates, however, that shallow-buried rectangular structures, such as box culverts or rectangular tunnels, can be affected by shaking failure. To avoid the complexity of a fully non-linear soil–structure interaction analysis, a number of simplified methods have been proposed in recent years, which have gained popularity among designers. The aim of this paper is to investigate the applicability limits of such simplified analyses. The study compares the results obtained using simplified approaches with those emerging from non-linear static soil–structure interaction analyses, accounting for the following effects: the frictional behavior of the soil–structure interface, the geometry of the box structure, the overburden depth, the maximum PGA, and the increasing soil stiffness with increasing depth. The outcomes of the analysis indicate that shallow-buried rectangular structures are strongly affected by non-linear frictional effects at the soil–structure interface. The soil–structure interaction under seismic condition is shown to change smoothly from the condition of deep burial to the condition of “null overburden depth”. For a given aspect ratio, stiff, shallow-buried rectangular structures prove to be affected more deeply by sliding at the soil–structure interface than flexible structures and, for low aspect ratios, these structures may undergo a rigid rotation (rocking) that may even involve a partialization of the base foundation. For a reliable evaluation of member forces from racking distortions, rocking must be carefully taken into account.

A new beam and post system for multi-storey timber buildings has been developed in Sweden. The building is braced with timber walls constructed from two Kerto-Q LVL boards glued and screwed onto a glulam frame. The walls are prefabricated off-site and can be connected to the foundation using either glued-in steel rods with metric thread or nail plates. Introductory racking tests of full scale walls anchored with glued-in threaded rods were performed. The paper presents the results of the experiments and discusses the use of the transformed section method to predict racking capacity of the anchored wall. To evaluate the strength of the glued-in rods, a newly proposed model was employed. An analytical study was conducted to investigate the role of the sheathing and the contribution of the axial force on the racking capacity of the walls. The wall panels tested in this experimental programme showed high strength and stiffness under racking load. The anchoring joints with glued-in steel rods with metric thread demonstrated a high load-carrying capacity with, however, large scatter and a brittle failure mode characterized by pull-out from the timber member. The transformed section method was successfully used to predict the racking capacity of timber walls anchored with glued-in steel rods.

Following an accident on ro-ro passenger ship, guidelines for evaluation of securing arrangements have been issued by Maritime Bureau of Ministry of Land, Infrastructure, Transport and Tourism, taking into account that one of the causes of the accident was deemed as sliding failure of cargos. The method to evaluate cargo securing arrangements in the guidelines does not take into account stiffness of cargoes and securing gears, for the sake of practicality, while securing loads depend on such stiffness. The purpose of this research is to clarify the appropriateness of the method to evaluate securing arrangements in the guidelines for semi-trailers, i.e., one of representative cargoes on ro-ro ships. For this purpose, the securing loads calculated by the method set out in the guidelines and by a method considering stiffness were compared. For the calculation using the latter method, racking stiffness of a typical semi-trailer and spring coefficient of a commonly used securing gear were measured. It is concluded that the method set out in the guidelines gives appropriate results on the whole, but this method may provide too small securing load in case that acceleration acting on a cargo is small.

The stability of steel storage racks in the cross-aisle direction is typically ensured by cold-formed steel bolted upright frames. Sensitive to second-order effects, accurately determining the shear stiffness of these frames is essential for seismic design and for ensuring the stability of the rack, especially for high-bay racks and racks supporting the building enclosure, where the outer rack frames must withstand cross-aisle horizontal actions due to wind loading. The main international racking specifications adopt different approaches to determining the shear stiffness of cold-formed steel storage rack upright frames. The Rack Manufacturers Institute (RMI) specification conservatively uses Timoshenko and Gere's theory. The European Specification EN 15512 recommends testing, however it is not clear whether the shear stiffness obtained using the recommended test procedure is correct. The newly revised Australian Standard AS 4084 adopted the European approach but also introduced an alternative test method for determining the combined bending and shear stiffness of upright frames in the transverse direction. This paper reviews and analyses the factors influencing the shear deformation of cold-formed steel bolted upright frames and introduces the alternative test set-up adopted in the revised Australian Standard. 36 upright frames have been tested using the two test methods, and experimental results are presented, discussed and compared with finite element analysis results. Recommendations on how to use the test outcomes in design are also provided. Based on these recommendations, the paper shows that the two test methods are not equivalent and yield different results for the transverse shear stiffness of upright frames.

The available simplified analytical methods for the seismic design of underground structures either assume yielding or rigid-unyielding conditions. Underground reservoir structures do not fall into either of these categories. In this paper, we present the results of three centrifuge experiments that investigate the seismic response of stiff-unyielding buried structures in medium dense, dry sand and the influence of structure stiffness and earthquake motion properties on their performance. The structure to far-field spectral ratios were observed to amplify with increased structural flexibility and decreased soil-confining pressure at the predominant frequency of the base motion. Lateral earth pressures and racking displacements for a range of structural stiffnesses were compared with procedures commonly used in design. Pre-earthquake measured lateral earth pressures compared well with expected at-rest pressures. However, none of the commonly used procedures adequately captured the structural loadin...

Drive-in storage racks, made of cold-formed steel, are the main racking system used in industry for storing goods. The storage space utilization of drive-in racks is high at the price of the weak downaisle stability. This paper presents a general analysis of the lateral stiffness of drive-in racks in the downaisle direction. A total of 24 static tests of drive-in rack systems have been conducted under single-point horizontal force. The effects of some constructional details, such as bracing configuration, cargo pallets, and the number of bays, are considered. The experimental results indicate that either top plan bracing or back-spine bracing can change the load transfer through rack structures and increase the lateral stiffness of racks. By acting as the horizontal bracings of adjacent columns and reinforcing the rotational stiffness of column bases, the stored pallets are also the beneficial factor for improving the lateral stiffness of racks. According to the special structural characteristic o...

Pallet racking systems, made of thin-walled cold formed steel profiles, are commonly used to store valuable goods and products in the logistics industry. In service conditions, longitudinal (down-aisle) stability of the racks is provided by the flexural stiffness of the demountable beam-upright column connections and base joints. Rack designers usually prefer to avoid bracings for a full accessibility of shelves from both aisles. However, under seismic conditions, typical rack connections cannot often provide sufficient flexural performance in terms of stiffness and strength, which deems necessary to introduce spine (longitudinal) bracings in the down-aisle direction. Yet the racks can only be braced at one of their two longitudinal planes to allow pallet loading from the aisle, which results in an asymmetric horizontal bearing configuration. This combined with their perforated upright columns, and non-standard beam-upright and base connections make it even more difficult to estimate their complex global seismic performance. Therefore, full scale experimental investigations are strongly needed in order to understand and quantify the global performance of the braced storage racks, and improve their design for seismic actions. This paper presents the experimental results of the Europe's largest full-scale push-over testing program that has been carried out on racking systems. In particular, experimental global capacity curves of 6 fully-loaded pallet racking specimens with spine bracings, provided by 5 different international rack producers, are presented, discussing the key factors influencing the racks’ response, as well as the failure mechanisms of the different rack typologies. Furthermore, behaviour factor (q) values of each specimen are derived from re-analysis of test results. Vulnerability of braced racks to bracing connection failure is demonstrated, highlighting its causes. Design indications are provided in order to guarantee a globally homogenous ductility under seismic actions.

The performance of portal frame walls was studied using a finite-element model verified with results from tests of full-size portal frame walls. Parameters such as wall height, metal strap type and location, doubling of the bottom plate, sheathing placement, and nailing pattern were investigated. Results indicate that in all cases, lateral load capacity and stiffness are greatly reduced with the increase of wall height. Considering the effect of different metal strap types and locations, the tensile strength of metal straps has the greatest impact on the lateral load capacity and stiffness. Walls with metal straps placed directly on the framing members outperform walls with metal straps placed over the sheathing. For walls with a double bottom plate and two rows of nails fastening the bottom plate, the stiffness and lateral load capacity are slightly increased compared with walls with a single bottom plate. For walls with unblocked sheathing at midheight, the lateral load capacity is the same as i...

Steel storage racks, made of cold-formed steel, are used extensively in industry for storing goods. Two main racking systems prevail, referred to as selective racks and drive-in racks. International racking design codes deal mainly with selective racks, but limited design guidelines are available for drive-in racks. Drive-in racks require minimum floor space by storing pallets one after the other with no space between them. The forklift truck drives into the rack to store the pallets on the first-in, last-out principle. To allow forklift passage, drive-in racks can be braced only at the back (spine bracing) and at the top (plan bracing) in the down-aisle direction, resulting in a complex slender structure with poorly understood three-dimensional (3D) behavior and increased risk of collapse. Tests on drive-in rack systems to accurately capture their 3D behavior have not previously been available in the literature. This paper presents experimental results from full-scale tests conducted on a complete drive-...

This paper presents simple equations for the natural lateral and rotational periods of vibration for high-rise steel structures comprising braced frames with outrigger trusses. The structural floor plan can be symmetric or asymmetric combinations of identical bents. Each braced frame is modelled by a cantilever with a bending stiffness and racking shear stiffness. The outriggers are represented by a rotational spring. The stiffness of the outrigger spring is dependent on three specific modes of behaviour: bending and racking shear in the outrigger truss and axial lengthening or shortening of the exterior columns. This yields a simple calculation of the maximum horizontal deflection of the structure. For the rotational frequencies, the bending, racking shear and spring stiffness parameters of the steel structure each are combined to yield a torsional stiffness, a warping stiffness and a warping spring stiffness which allow an assessment of the rotation at the top. The approximate method of analysis relates the natural frequencies of the structure to the top deflection and rotation when the self-weight is taken as a distributed horizontal load. In the calculations a braced frame is represented by a rigid stick model with its overall flexibility assigned to a rotational spring at the base. Results obtained by the simplified method are compared to those from a finite element analysis. The approximate method gives acceptable conservative results for preliminary analysis.

The paper presents an experimental analysis of timber - framed wall panels with openings, coated with single fibre-plaster boards fastened to a timber frame. The present study is a continuation of the research work realized in the last years in reinforcing of the prefabricated timber-frame wall panels without any openings. The aim of the study presented here was to provide the information about the influence of the openings on the wall's racking load-carrying capacity as well as on the horizontal stiffness of the timber-frame wall panels. The tests were carried out on three groups of full-scale wall panels with different areas of openings. The measured results were compared to the results of wall panels without openings. Subsequently, the strength/stiffness ratios, defined as the ratios of strength/stiffness of wall panels with openings to those of no-opening wall panels were calculated. Finally, the obtained results were compared to three analytical procedures from the literature, namely the equations proposed by Yasumura and Sugiyama, by the Method B from Eurocode 5 and by the equations presented in Supek, Dujic and Zarnic. The presented experimental study also emphasizes the conclusion that the timber-frame wall panels containing an opening may be accounted to contribute to the overall horizontal load-carrying capacity, especially when a considerable part of the structure is made of such panels.

This paper presents the finite element buckling and dynamic analyses of two-dimensional (2D) single frames and three-dimensional (3D) frames of cold-formed sections with semirigid connections used in the conventional pallet racking system. The results of buckling analysis for the single 2D frames are compared with those from the experimental study and effective length approach given by RMI. The finite element model used for the single 2D plane frame is further extended to 3D frames with semirigid connections, for which the buckling analysis results are obtained. The buckling and dynamic analyses are carried out using ANSYS for 18 types of developed column sections. The stiffness of the semirigid connection is determined by both the single and double cantilever test methods, along with the nonlinear finite element analysis. Further, an equivalent single degree-of-freedom model is proposed for simulating the seismic behavior of the storage rack in the down-aisle direction, aimed at developing simplified equations for the fundamental period, base shear, and top displacement of the rack. A parametric study is carried out to compute the fundamental period and mode shape. The transient dynamic analysis is also performed for evaluating the impact of the forklift on columns of the frame.

The paper addresses the problem of determining the accidental forklift truck impact forces on steel storage racks. Based on first principles of mechanics, simple models of a loaded forklift truck and a drive-in racking structure are presented. Model masses, as well as stiffness and damping coefficients are calibrated against experimental results obtained from tests of a forklift truck and a drive-in racking structure. Comparisons between experimental results and solutions obtained from the simple mechanical models show that the simple models accurately reproduce the static and dynamic behaviours of their associated structures. Based on the drive-in rack impact test results presented in a companion paper (Gilbert and Rasmussen, submitted for publication) [1] and the simple mechanical models for drive-in racks, actual impact forces are calculated and presented. Finally, using the impact test results and the simple mechanical models, the actual motion of the forklift truck body is calculated. This motion, being a common characteristic to all drive-in racking impacts, allows impact forces to be obtained for various pallet loads, impact elevations and rack characteristics. Thus, the paper concludes with a general method for calculating forces generated under forklift truck impact.

This paper presents an experimental analysis of timber-framed wall elements with openings, coated with single fibre-plaster boards (FPB) fastened to a timber frame. The aim of the study presented here was to provide the information about the influence of the openings on the wall’s racking load-carrying capacity as well as on the horizontal stiffness of the timber-framed wall element. The tests were carried out on three groups of full-scale wall panels with different areas of openings. The measured results were compared to the results of wall panels without openings (having the same dimensions and material properties) obtained from the previous research work. Subsequently, the strength/stiffness ratios, defined as the ratios of strength/stiffness of wall panels with openings to those of no-opening wall panels, were calculated. Finally, the obtained results were compared to two analytical procedures from the literature, namely the equations proposed by Yasumura and Sugiyama and by the Method B from Eurocode 5. The comparison shows that the present results are more comparable to the former procedure, while the later one in general gives higher values of strength/stiffness ratios. The presented experimental study also emphasizes the conclusion that the timber-framed wall elements containing an opening may be accounted to contribute to the overall horizontal load-carrying capacity, especially when a considerable part of the structure is made of such panels.

This paper explains an experimental study on a full-scale L-shape single story light frame wood house under the uniform lateral load simulated using a gasbag. The study verifies that shear walls are staggered to each other and the 1.0-m offset between them behave as a continuous shear wall, floor diaphragm with a reentrant corner up to 1.0 m that does not need a continuous end chord. Degradation in racking stiffness of light frame wood construction after continuously repeated cyclic lateral loads is not observable, while intermittent and larger amplitude cycling can cause observable settling of residual deformation and degradation in racking stiffness. The rigidity performance and high racking resistance of the floor diaphragm enables the light frame wood building to remain intact under ultimate lateral load, and recommends interstory percent drift restrictions for the lateral wind load design of the structures and the way to properly calculate racking capacity of gypsum sheathings. The conclusion of this paper can benefit the engineering practice of the light frame wood structures in hazard lateral load regions.

The stability of steel storage racks, which are often unbraced, may depend solely on the pallet beam to upright connector and on the stiffness of the base plate to floor connection. This paper presents experimental results from cyclic tests performed on portal beam to upright bolted moment connections intended for cold-formed steel drive-in and drive-through storage racks. In storage racks, portal beams are typically connected to uprights by “tab connectors”, which are costly to manufacture and experience initial looseness. By simply bolting the portal beams to the uprights, bolted moment connections may represent a cost-effective alternative to “tab connectors”. A literature review shows that bolted moment connections between cold-formed steel members are economical and feasible. However, experimental results show a significant amount of looseness in the connection after an initial high moment–rotational stiffness. Being slender structures, storage racks are sensitive to the second-order P – Δ effect, and international racking specifications require the initial looseness of the tab connectors to be considered when analysing the stability of the rack in the down-aisle direction (sway motion). The non-linear cyclic behaviour of bolted moment connections is presented and explained herein. Based on finite element results, it is shown that, for drive-in and drive-through racks, the looseness in bolted moment connections can be ignored in ultimate limit states design. Finally, the paper concludes with proposing two methods, with different degree of complexity, for the design of drive-in and drive-through racks with bolted portal beam to upright bolted moment connections.

Shear walls in post-frame buildings are commonly constructed with timber posts and horizontally framed wall girts. The bottom wall girt, called the skirtboard or splashboard, is typically pressure preservative-treated (PPT) due its location near the ground. Wood plastic composite (WPC) lumber is an environmentally benign alternative to PPT lumber, and WPCs avoid the copper-rich chemical formulations found in PPT lumber that potentially accelerate the corrosion of the steel panels and fasteners. WPC products have mechanical properties different from those of lumber, so testing is required when substituting WPC products for PPT lumber in post-frame shear wall assemblies. In this study, a commercially available WPC product and PPT lumber were used as skirtboards in two common framing configurations of post-frame endwalls to evaluate possible effects on shear strength and stiffness. The study found that two 38 × 140 mm WPC boards can be substituted for a single 38 × 235 mm PPT board without significantly affecting the strength or stiffness of the shear walls. A high-density polyethylene WPC formulation was chosen for this study due to its relatively low modulus of elasticity as compared to other commercially available WPC formulations (e.g., using polypropylene or polyvinyl chloride). No significant buckling of the WPC members was observed during the tests. The dominant failure mode of the shear walls was buckling of the ribbed steel sheathing. It should be noted that this study only included a relatively limited sample of two wall constructions. Additional testing is recommended for wall constructions and materials not studied herein.

It is known that the shear performance of plywood depends on the grain direction of veneer sheets, and if veneer sheets are oriented 45 degree against the lateral sides, it indicates highest shear performance. Authors produced experimentally the diagonal plywood, which were laminated parallelogram veneers oriented diagonally against the lateral sides. The in-plane shear performance of the bearing wall, which joined diagonal plywood to the frame with the nail spaced 50mm to 150mm apart, was evaluated by racking test. When the nail space was shortened, load at yield point increased, but maximum load of diagonal plywood was almost equal to standard plywood. The comparable result was also obtained from the lateral nail resistance test.In conjunction with this, shear strain distribution of panel was measured by digital image correlation (DIC), and approximate shear modulus of panel could be calculated from load-strain curve. Shear strain of diagonal plywood was lower than that of standard plywood. The bearing wall using diagonal plywood indicated large initial stiffness. As a result, it was concluded that bearing wall using diagonal plywood indicates higher reference shear strength. In order to increase the shear strength that is added to diagonal plywood, it is effective if the interval of nail is to some extent shorter than 150mm, which is the specification of wall index 2.5 of bearing wall using standard plywood. Shear modulus of full-sized diagonal plywood was about 4 times as much as that of standard plywood.

Initial conditions introduced by different wedges in a traditional Japanese “Nuki” joint affect its stiffness and load carrying capacity significantly. Due to the complicated nature of the problem, no proper measurements have been undertaken historically, nor has there been theoretical modeling of the initial stress state in the joint. This leads to a lack of full understanding in the critical regions where high contact stresses are generated by locking wedges into various engaged positions. There is a need to undertake quantitative studies in those regions in order to make better designs and assist renovation of this type of the joint. In the work described in this paper, a series of experiments has been undertaken to investigate initial strain (and hence stress) states of the “Nuki” joint induced by the use of wedges with a typical angle but various tightnesses. A large number of strain gauges were used to obtain strain distributions in critical areas of the “Nuki” beam element. In Part 1 of the paper, 3-D nonlinear finite element models were developed to simulate the wedge insertion processes and the initial strain (stress) states. Numerical simulations were compared with the corresponding experimental results yielding reasonably good correlation. Racking resistance of the “Nuki” joint will be presented in Part 2.

The shear stiffness of pallet rack uprights in the cross-aisle direction is determined experimentally by a load test involving repeated tensile or compressive loading of a cross-aisle frame without cycling through the origin. The effects of looseness are ignored. This paper describes the results of a series of tests involving full cyclic loading through the origin, not only to determine the stiffness of the frame but also the looseness inherent in the connection. Design recommendations are made to include the effects of looseness in cross-aisle sway analyses and to use cyclic testing to determine the shear stiffness of racking frames. A parametric study was conducted on a commercial frame which showed that if the design recommendations are adhered to that the influence of shear stiffness in the cross-aisle direction does not normally have a significant effect on frame capacity.

Pallet rack uprights are braced in the cross-aisle direction forming a frame, which behaves like a built-up column. Currently two approaches prevail in the racking industry to determine the shear stiffness of these frames. The Rack Manufacturers’ Institute (RMI) code uses a theoretical formula whereas the Federation Europeenne de la Manutention (FEM) code requires testing. There is a considerable difference in the stiffness values determined by the two approaches. A literature review showed that the stiffness predicted by the RMI code could be up to 20 times higher than the experimental stiffness. The shear stiffness of the frames is influenced by the bracing pattern and the connections between the elements. Local distortion of the thin walled open section upright, joint eccentricity and slip due to bolt clearances all affect the behaviour of the frames. The present paper describes experimental and numerical studies conducted at Oxford Brookes University to evaluate shear stiffness.