•Twelve connections between high-rise racks and the spine bracing were experimentally investigated.•Comprehensive test data were generated using digital image correlation technique.•A component-based ...model is established for the rack-to-spine-bracing connections.•Component deformation patterns are explicitly considered in the analytical model.•Design recommendations are provided by performing analytical studies.
The primary lateral load resisting system of the high-rise braced steel storage racks is the spine bracing located at a short distance away from the rear rack frames. The connections between the rack frames and spine bracing, which transmit the horizontal stabilizing forces, dictate the effectiveness of the spine bracing and the global performance of the entire high-rise racking system. The first part of this paper experimentally establishes the behavior of the connections between the racks and the spine bracing under lateral loads, utilizing four groups of three nominally identical test specimens. A digital image correlation (DIC) measurement system is employed to generate comprehensive data associated with the behavior of individual components of such connections. The behavior of the connection components is quantified and discussed based on the three-dimensional deformation field recorded by the DIC system. The second part of this paper develops a component-based elastic analytical model for the connections between the racks and the spine bracing under consideration. The endplate spatial flexural bending mechanism, as well as the upright cross-section distortional behavior, are explicitly considered by the analytical model. The contributions of each individual component towards the total deformation of the connections are quantified. The paper concludes with design and construction recommendations for the enhancement of the connections between the racks and the spine bracing, while recognizing the limitations of this research.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Proposed several new connections by adding bolts or/and welding to traditional speed-lock connections.•Investigated the failure modes of new connections in detail through monotonic and cyclic ...experiments.•Studied the stiffness and hysteretic responses of all connections.•Explored the energy dissipation capabilities from the hysteretic responses for all the connections.•Investigated the ductility and stiffness degradation of all the connections.
The purpose of this paper is to explore the bearing capacity and energy dissipation of several variations of speed-lock connections of cold-formed steel storage racks. Commonly used speed-lock connection exists large slippage and low energy dissipation capacity, new speed-lock connections with additional bolts (and welds) are investigated in order to enhance its performance. Their monotonic behavior and hysteretic response under cyclic loading were studied experimentally using a cantilever test method. The tests were conducted using both the EN 15512 monotonic protocol and AISC seismic provisions’ cyclic-test protocol for each specimen. The failure modes, moment–rotation response, and associated stiffnesses, bearing capacities, and energy dissipation capabilities were fully investigated. Both monotonic and cyclic responses showed that the additional bolts (and welds) significantly enhanced the bearing capacities and deformability of the connections, though the initial stiffness and equivalent stiffness (i.e., according to the EN 15512 specification) showed little improvement. The hysteretic responses of all connection variations investigated demonstrated pinching behaviors. The energy dissipation capability has been greatly improved with additional bolts (and welds) except of the one with only lower bolts, which could also be corroborated through the analyses of the calculated equivalent viscous damping coefficient and the displacement ductility factor. In addition, the stiffness degradation has been observed for both positive loading and negative loading, and adding bolts and welds could effectively reduce this effect.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Steel storage racks are structures commonly used by all industries in Chile; nevertheless, due the seismic hazard in the country and its configurations, these structures are highly vulnerable to ...earthquakes and no specific regulations exist to design them. In this research, the seismic performance of steel storage racks subjected to Chilean Earthquakes was evaluated using nonlinear pushover and nonlinear dynamic analysis. The studied models consider different heights and global slenderness ratios in both directions and soil types. Racks were evaluated using an Incremental Dynamic Analysis (IDA) according to FEMA P695. Deformation values were exceeded in the down-aisle direction and the use of braces was necessary to control the interstory drift and high deformation levels. Also, the expected level of damage for drift design limits in models unbracing is not enough to keep the operation of the structures and more severe regulations are necessary to achieve a performance in agreement with Chilean design philosophy. Finally, the use of horizontal and lateral bracing improves the seismic performance of steel racks.
•Seismic performance is evaluated from nonlinear static and dynamic analysis with variation of geometrical properties and seismic hazard.•Horizontal braces improve the seismic performance in steel storage racks.•An incremental dynamic analysis was used to assess the performance according to FEMAP695.•The common procedures for seismic performance evaluation could not assess the real performance of steel storage racks.•A suggestion to incorporate additional requirements to Chilean design code has been proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•We study order picking problem in storages with mobile racks.•We investigate the problem of simultaneously allocating orders and racks.•The allocation orders and racks to pickers is formulated as an ...integer program (IP).•We present two heuristics (matheuristics) for the problem.•We also consider sequencing racks for presentation to each picker as an IP.
In this paper we investigate the problem of simultaneously allocating orders and mobile storage racks to static pickers. Here storage racks are allocated to pickers to enable them to pick all of the products for the orders that have been allocated to them. Problems of the type considered here arise in facilities operating as robotic mobile fulfilment systems. We present a formulation of the problem of allocating orders and racks to pickers as an integer program and discuss the complexity of the problem. We present two heuristics (matheuristics) for the problem, one using partial integer optimisation, that are directly based upon our formulation. We also consider the problem of how to sequence the racks for presentation at each individual picker and formulate this problem as an integer program. We prove that, subject to certain conditions being satisfied, a feasible rack sequence for all orders can be produced by focusing on just a subset of the orders to be dealt with by the picker. Computational results are presented, both for order and rack allocation, and for rack sequencing, for randomly generated test problems (that are made publicly available) involving up to 1000 products, 200 orders, 500 racks and 10 pickers.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Twelve rack-to-spine-bracing shear connections were experimentally investigated.•Comprehensive test data were generated using digital image correlation technique.•A component-based analytical model ...is established for the shear connections.•Three-dimensional behavior of individual components are analytically determined.•Design and construction recommendations for the shear connections are provided.
High-rise steel storage racks are cold-formed thin-walled steel frames, which achieve their lateral strength and stiffness by the use of a spine bracing system in the down-aisle direction commonly located at a short horizontal distance away from the main rack frames. The shear connections between the main rack frame and the spine bracing system play a dominant role in the effectiveness of the spine bracing system. This paper experimentally investigates the behavior of the shear connections used in industrial practice between a steel storage rack and the spine bracing system with posts using four groups of three nominally identical connection specimens. By employing a digital image correlation (DIC) system, the tests generate comprehensive data and establish the real-time deformation fields of individual components of such shear connections. Based on the component-based approach, a linear-elastic analytical model is developed for the type of shear connections under consideration. The proposed analytical model explicitly captures the behavior of the individual connection components, including the three-dimensional flexural bending of endplates, as well as the distortions of the open sections of the upright and the bracing post. Based on the proposed model, this paper quantifies the contribution of each component towards the total deformation of the shear connections. The investigation establishes that the cross-sectional distortion of the bracing post and the out-of-plane bending of the upright web are the most flexible components of such shear connections. Recommendations associated with the shear connections under consideration are proposed for the rack designers and manufacturers.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study aims to verify the damage and collapse of the pallet rack due to external forces, such as earthquakes, through a shake table test and analyze the behavioral characteristics of the pallet ...rack column foundation for each fixing condition caused by a continuous external force. A shake table test was conducted on a pallet rack commonly used in warehouses to examine its damage and collapse owing to external forces. In the shake table test, the strength of the load was increased to investigate the collapse of the pallet rack, and the failure of the member connection was regarded as a collapse. The behavioral characteristics were analyzed using the shake table test according to the conditions of the baseplate connections, which are determined by the external forces. The displacements caused by the external force, permanent displacement, cumulative displacement, and damage were analyzed from the data obtained through the experiment. Finally, the possibility of collapse according to the fixing condition was verified.
•Explored pallet rack damage and collapse due to external forces such as earthquakes.•Shake table test was conducted on a pallet rack commonly used in warehouses.•Analysis of external forces, permanent displacement, cumulative displacement, damage.•Results serve as reference for improving the stability and durability of pallet racks.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The baseplate upright connections of the steel storage racks are often attached to the concrete floor by anchor bolts possibly at an eccentric location. Currently available rack design specifications ...do not provide any guidelines to take account of the influence of eccentric anchor bolt location and do not consider the associated baseplate behavior in the design of such storage rack base connections. The first part of this paper experimentally established the flexural behavior of the baseplate upright connections with eccentric anchor bolts. The experiments considered an enhanced test setup and five groups of three nominally identical test specimens. Influencing parameters such as the baseplate thickness, anchor bolt size, the bracket thickness and the upright thickness were studied. The experimental observations revealed that the baseplate eccentric anchor bolt assembly plays a dominant role on the flexural behavior of the entire baseplate upright connections. The rotational stiffness, the failure mode and the moment capacity of the base connections are strongly intertwined with the eccentric anchor bolt location as well as the baseplate bending behavior. In order to further understand the behavior of such connections, in the second part of the paper, a component-based analytical model is established to predict the initial rotational stiffness and the progressive post yielding rotational stiffnesses of the baseplate upright connections. The moment capacity of the connections is also determined using a deformation limit-based method. The analytical model gives only a 3% underestimation of the initial stiffness and a 3% overestimation of the moment capacity compared with experimental results. The proposed model is suggested to be incorporated in future rack design specifications so that the model can be used by the rack designers to analytically determine the behavior parameters of the eccentric anchor bolted baseplate connections. The rack designers can also use the proposed model to identify the deformation contribution of each individual component and to develop a multi-linear moment-rotation relation of the baseplate upright connections without resorting to the physical experimental tests. Parametric studies were also performed using the proposed analytical model and the influence of relevant parameters had been quantified. Doubling of the baseplate thickness may result in a 11–37% increase in the initial rotational stiffness of the considered baseplate upright connections.
•The flexural behavior of fifteen eccentric anchor bolted steel storage rack baseplate upright connections were tested.•The flexural behavior of the baseplate connections is strongly intertwined with the eccentric anchor bolt position.•A component-based analytical model is established to predict the stiffness and ultimate moment of the baseplate connections.•The influence of the eccentric anchor bolt position on the base connection behavior is explicitly considered in the model.•Design guidelines for the eccentrically anchor bolted base connections are provided by performing parametric studies.
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The shear stiffness of braced frames of thin-walled cold-formed steel storage racks was experimentally and numerically investigated in order to establish the effect of connection flexibility on the ...accuracy of different analysis methods. The analyses which included a detailed 3D Finite Element model, a 2D frame analysis with beam elements and a simple hand calculation indicated significant variation of results compared with experimental values. A simplified modelling approach for 2D elastic analysis of braced frames was proposed. The approach is aimed at practical applications to account for the flexibility in bolted connections and leads to better approximation of the shear stiffness.
•Accuracy of conventional theoretical methods has been examined.•None of the conventional theoretical methods are accurate enough.•A simplified modelling approach is proposed for practical applications.•Proposed method accounts for the flexibility in bolted connections.•Adopting the proposed method leads to better approximation of the shear stiffness.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A series of earthquakes, the highest of magnitude
M
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5.9, hit a portion of the Po Valley in Northern Italy, which was only recently classified as seismic. The paper reports the findings and the ...lessons learnt from a preliminary field survey which was conducted immediately after the second event. As a result of the economic attitude of the affected area, and possibly of the characteristics of the event, an unprecedented number of industrial precast buildings were affected, resulting into most of the casualties as well as in large economic losses. Whereas most of the damaged and collapsed buildings were designed for gravity loads only, evidence of poor behavior of some precast buildings designed according to seismic provisions were discovered. The paper provides a description of the performance of precast buildings, highlighting the deficiencies that led to their poor behavior as well as some preliminary recommendations.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This paper is concerned with the equivalent static force method for the seismic design of selective storage racks with uplifting baseplates. It proposes a new procedure for determining the effective ...natural period of such racks in the cross-aisle direction for use in the NZS 1170.5 equivalent static method. The procedure is derived by comparing the base shear results of trialled Rayleigh methods against nonlinear time history analysis results involving 15 upright frame configurations, comprising 5 baseplate types for three, five and seven level racks. The time history analyses use a suite of 44 ground motion records. It is recommended that the effective natural period be computed in the Rayleigh method using nonlinear static analysis with the storage loads included, where the Rayleigh lateral loads create an overturning moment equal to the restoring moment of the storage loads. The proposed procedure leads to more efficient designs of storage racks with uplifting baseplates compared to the conventional procedure based on the use of linear analysis in the Rayleigh method for determining the natural period, but results in more conservative designs compared to the use of nonlinear time history analysis.
•First ever study on the equivalent static method for rocking racks.•Includes five baseplate types with very different responses.•Includes a comprehensive set of 44 ground motion records.•A new Rayleigh based method for determining the effective period.•A more efficient seismic design procedure for rocking racks.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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