Lattice Boom Research Articles

Dynamic effects on the lattice boom crane due to the wind, moving load and earthquake events

The present research concerns the evaluation of the dynamic effect on lattice boom cranes. The dynamic actions involved in this research are: wind, moving load and earthquake, assumed as time-varying actions. The research starts with the design of a large crane by adopting classical standards for these structures (UNI EN 13001 series). The elaborations were performed by analytical methods followed by solid model building and finite element analysis (Solidworks® and Ansys® software). The next step was to define the aforementioned loads acting on these structures. The wind action model was compared with the static approach. Payload displacement induces high-intensity actions on the crane structure; to better understand these effects, several load curves were simulated. The last action considered is the earthquake phenomenon, which is not usually adopted to design this type of structure.

Study on the axial compressive ultimate load-carrying capacity of high strength steel tubes with lattice boom

Lattice boom used on the crawler crane are welded by slender high strength steel tubes. Many studies show that the actual bearing capacity of high-strength steel tubes is higher than the stability bearing capacity calculated according to the specification. To obtain the actual bearing capacity of high-strength steel tubes and apply it to engineering practice, a series of axial loading tests are carried out on two kinds of high-strength steel tubes of 20Mn2 and S890 to obtain their damage load. By handling test data, and the coefficient fitting and correction are carried out according to the stability coefficient calculation formula of the Chinese steel structure specification. The results show that it is conservative to calculate the bearing capacity of high strength steel tubes by using the stability curve in the specification, and the bearing capacity of high strength steel tubes calculated by fitted coefficient is more consistent with its actual bearing capacity.

Load-Sway Control for Rotary Crane Considering Torsional Deformations of Vertical Jib

Large rotary cranes have a lattice structure tower boom which causes torsional deformation when transporting heavy loads. Therefore, it is necessary to design a controller that takes into account the torsion of the tower boom to control the load-sway and position of the jib. This study proposes a linear state-space model of rotary cranes that takes into account the torsion of the tower boom which stands vertically, and designs a controller using this model. Both simulation and experimental results are investigated to illustrate the superior performance of the controller designed in this study.

Sensor-less and time-optimal control for load-sway and boom-twist suppression using boom horizontal motion of large cranes

Load-sway and boom-twist should both be considered in motion control given that a large crane typically has a long lattice boom. Hence, this study first analyzes the load-sway and boom-twist (vibration) of an actual crawler crane, and proposes a new dynamics model considering the above vibration. To ensure safety, sudden acceleration/deceleration is prohibited while controlling the motion of large crane. In addition, real time measurement and feedback of vibration is generally difficult. Hence, this study proposes a vibration sensor-less control based on a cycloidal motion trajectory with smooth acceleration/deceleration. Two-dimensional load-sway can be suppressed only by boom horizontal motion for simple implementation. Time optimality is also considered in the motion trajectory design in order to ensure operational efficiency. Experimental results demonstrate the effectiveness of the proposed approach.

Reliability-based design optimization for the lattice boom of crawler crane

The reliability-based design optimization (RBDO) problem involving discrete design variables and multi-working constraints is tackled with the consideration of the uncertainty factors in the optimal design of crawler crane’s lattice boom. In the optimization model, the uncertainties of material property, geometric parameters and loads are represented by random variables. The geometrical dimensions, performance functions’ reliability indexes and the minimum weight of lattice boom are defined respectively as the random design variables, probabilistic constraints and objective function. Integrating the reliability analysis method based on response surface method (RSM) with multi-island genetic algorithm (MIGA), an efficient reliability-based design optimization process for the lattice boom is developed under the typical constrained working conditions. Several verification cases are presented to demonstrate the effectiveness of optimization results. It is shown that the reliability-based design optimization method can not only satisfy the reliability constraints of the lattice boom, but also ensure the safety and economy of crawler crane boom as well as minimize the structure weight. The developed method is capable to be extended to the reliability-based design optimization of other large and complex construction machinery structures.

Morphing lattice boom for space applications

Structures used in space applications demand the highest levels of stiffness for their mass whilst also performing in a hostile environment. To partly address these requirements and so as to also pack efficiently for stowage during launch we propose a new type of compact telescopic morphing lattice space boom. This boom stows within a 1U CubeSat volume and is lightweight being only 0.4 kg. The boom has a total length of 2 m in its deployed state which is 20 times its stowed height. The device comprises two multi-stable cylindrical composite lattices that are joined telescopically. These lattices nest inside one another in the stowed configuration, with the objective of improving packaging efficiency. Notably, prestress and lamina orientation are used to smoothly change shape from being compact when stowed to being extended when deployed. The lattices in the boom have been designed to maximise deployment force and to be self-deploying by tuning manufacturing parameters. As a result, only a small, lightweight mechanism is required to regulate deployment speed of the lattice boom. By reversing its direction, this mechanism can be used to retract the lattice boom to its stowed configuration, thereby enabling two-way reconfigurability.

Local stress analysis of the lattice boom considering parametric uncertainty

The lattice boom of the crane consists of slender tubes and its stability is of paramount importance. At present, most studies about stability of the lattice boom are based on certain parameters. Considering the uncertainty of the design parameters in actual design and production, the local stress of the lattice boom should be analysed with uncertainty. We propose a response surface method based on D-optimal design to simulate the relationship between each parameter and the local stress of the chord. Based on the obtained response surface function, Monte Carlo method is used to analyse the reliability of the lattice boom. The analysis results show that the uncertainty of the design parameters has a great influence on the local stress of the lattice boom. The initial imperfection factor has the greatest influence, and the interaction between the parameters is relatively small except the initial imperfection factor. The response surface method based on D-optimal design can simulate the complex model function relationship and simplify the complex model, which is highly efficient. So, it has broad application prospects in large-scale complex models.

Local stress analysis of the lattice boom considering parametric uncertainty

The lattice boom of the crane consists of slender tubes and its stability is of paramount importance. At present, most studies about stability of the lattice boom are based on certain parameters. Considering the uncertainty of the design parameters in actual design and production, the local stress of the lattice boom should be analysed with uncertainty. We propose a response surface method based on D-optimal design to simulate the relationship between each parameter and the local stress of the chord. Based on the obtained response surface function, Monte Carlo method is used to analyse the reliability of the lattice boom. The analysis results show that the uncertainty of the design parameters has a great influence on the local stress of the lattice boom. The initial imperfection factor has the greatest influence, and the interaction between the parameters is relatively small except the initial imperfection factor. The response surface method based on D-optimal design can simulate the complex model function relationship and simplify the complex model, which is highly efficient. So, it has broad application prospects in large-scale complex models.

Izračunavanje dinamičkog ponašanja pokretnih kranova sa rešetkastom strelom tokom podizanja tereta

Lattice boom mobile cranes are mainly used to move heavy payloads with a large hoisting radius. During this work, crane motions cause dynamic forces on the crane's structure. In order to guarantee the safety of cranes, exact calculations are absolutely essential for the boom system. The calculation standards stipulate the use of special dynamic factors to estimate the dynamic loads. Several research projects have shown, that the standards often describe the dynamic effects only approximately. In order to calculate the dynamic behaviour accurately, without a disproportionate increase in computing time, special vibration models have been developed in a current research project. This paper presents a new vibration model for the process of hoisting suspended loads. The model is based on the response spectrum method and describes the dynamic effects in an exact way.

An accurate method for the calculation of ultimate load in lattice boom

To calculate the ultimate load of the lattice boom accurately, the effective length factor and imperfection factor are introduced to the current stability factor formula. First, we propose a stability factor formula by conducting a series of tests of high-strength steel tubes under axial compression and analyzing the experimental data. Second, the effective length factor of the chord which is caused by braces is calculated on the basis of different effective length factors and stability curves. Then, the correctness of the proposed effective length factor and the stability factor formula are proved by destructive tests under three loading modes. Using the modified stability factor formula, the accuracy of ultimate load of lattice boom is enhanced. These findings will be of great value for improving the design level of lattice boom and providing a theory and test basis for the completion of the buckling design method of the high-strength steel tubes.

해양플랜트용 격자 붐 크레인의 안전성 평가

해양플랜트용 격자 붐 크레인의 안전성 평가

Natural frequency analysis of lattice boom crane theoretically and experimentally

Having knowledge of dynamic properties named as natural frequency and mode shapes during the design process is important to determine proper design criteria. As a main aim of this study, experimental and theoretical modal analysis was carried out using a scaled physical model of selected lattice boom and comparing the frequency responses are evaluated. The 1/30 scaled physical model of a prototype lattice boom crane was designed and manufactured. Free vibration tests are performed and critical frequency values of the system are obtained. After that, physical structure was modeled by using ANSYS. Modal analysis was carried out. Efficiency of the numerical model is discussed by comparing the results which is found from theoretical and experimental studies. The comparative study showed that frequency values can be obtained from the finite element analysis. Thus, it will be possible to obtain frequency response of these kind of crane structures theoretically without needing experimental studies.

Research on Residual Fatigue Life Model for Lattice Boom of the Crane In-Service

There are lots of distributed sources in the process of fatigue crack propagation of the lattice boom, static evaluation of the reliability indicators cannot be satisfied to solve practical engineering problems. The load and fatigue resistance regards as a random process, considers the fatigue failure of the randomness in a variety of factors, the concept of dynamic reliability of the weights index is proposed, models of dynamic reliability of the weights index are built based on the fatigue bearing capacity mode and limit damage degree mode. Fatigue stress experiments comparisons are doing during a crawler crane according to the actual operating conditions and a K-type welded joints prototype. The results show that the dynamic reliability evaluation assessment model is more accurately in the fatigue life evaluation and the method can provide a new assessment method for engineering applications.

Fatigue Life Analysis of Crane K-Type Welded Joints Based on Non-Linear Cumulative Damage Theory

There are large numbers of welds on cranes’ lattice booms. Due to notably complicated force conditions, the fatigue life analysis of the lattice boom is difficult when designing the limit life. The fatigue cycle of the utilization level of a lattice boom crane is in the overlap zone of low-cycle fatigue and high-cycle fatigue. The poor accuracy of measurement of the fatigue life of lattice booms indicates that the calculation dispersion of the linear Palmgren-Miner (PM) rule was high. To obtain real crane stress spectra inexpensively and conveniently, a new stress spectra acquisition method based on the ‘measured & simulated & compared & statistics’ integrated strategy of crane K-type welded joints is proposed. The errors of the maximum stress amplitudes between the measured stress spectra and the simulated stress spectra were less than 10%. The fatigue test results also indicated that errors of the test fatigue life were less than 10% under both the simulated and the measured stress spectra. A new, simplified Huffman non-linear cumulative damage theory is proposed to calculate the fatigue life of crane K-type welded joints based on the notch stress and strain approaches. The calculation results indicated that the accuracy of the non-linear damage accumulation was higher than that of the PM rule, although the calculation result based on the non-linear damage accumulation method was slightly un-conservative when the initial damage was not considered in the calculation. By setting different initial damage conditions, various results were analysed, which revealed that the calculation errors of fatigue life based on the non-linear theory were less than 10% when the initial damage levels were set from 0.02 to 0.04. Such results are appropriate for engineering applications. When the fatigue life calculation needs to be more conservative, the initial damage levels may be set from 0.04 to 0.07; the resulting calculation errors could be less than 25%. As the Huffman non-linear cumulative damage theory requires data from only a few material properties, such as the cyclic stress-strain curve and the constant amplitude strain-life curve, it could therefore be more suitable for engineering applications with higher calculation accuracy and fewer costs.

A New Fatigue Life Calculation Method Based on Non-Linear Cumulative Damage Theory

Operating characteristics of small and medium tonnage lattice boom crane which withstand fatigue loads was analyzed in this paper. It showed that the lattice boom crane utilization level is in the overlap zone of low cycle fatigue and high cycle fatigue. There may be some plastic deformation in the structure. So the total damage calculated by the Palmgren-Miner rule had a large scatter. Typical operating conditions was analyzed that K-type welded joints of the boom is under axial load and in-plane bending loads. Several critical areas of K-type welded joints were determined by ANSYS finite element calculation software where the stress amplitude was larger on the single side of the lattice boom. A new stress spectrum acquisition method based on the “measured+statistics+compare+simulation” integrated strategy of crane K-type welded joints was proposed. Based on a simplified Huffman non-linear cumulative damage theory, fatigue life of crane K-type welded Joints were calculated based on the strain parameters. They were compared with Palmgren-Miner rule and together with fracture mechanics method. Results showed that although they were all conservative compared with test results, the new method can be applied easily in for engineering applications because it only need amplitude constant amplitude fatigue strain-life data.

Research on Residual Fatigue Life Model for Lattice Boom of the Crane In-Service

There were lots of distributed sources in the process of fatigue crack propagation of the lattice boom. Static evaluation of the reliability indicators couldnt be satisfied to solve practical engineering problems. The load and fatigue resistance were regarded as random processes and the fatigue failure of the randomness in a variety of factors, the concept of dynamic reliability of the weights index was proposed, models of dynamic reliability of the weights index were built based on the fatigue bearing capacity mode and limit damage degree mode. Fatigue stress experiments comparisons were done on a crawler crane according to the actual operating conditions with a K-type welded joints prototype. The results show that the dynamic reliability evaluation assessment model is more accurately in the fatigue life evaluation and the method can provide a new assessment method for engineering applications.

Cranes for Building Construction Projects

Cranes have come to symbolize building construction itself. They perform indispensable services in moving materials and components vertically and horizontally. Used since antiquity, their history is interrelated with the development of new power sources that replaced man and mule, first steam and later internal combustion, diesel, and electric engines. Mobile cranes can be rapidly deployed to lift heavy loads. New models with telescoping booms and all-terrain travel capability, compact urban machines, and even hybrids with tower cranes are beginning to replace the familiar lattice boom truck cranes. Mobile cranes have dominated the North American market, but a cultural change appears to be taking place toward tower cranes for building projects. Tower cranes, common in Europe for decades, are globally gaining in popularity with surging real estate developments. Ideal for dense urban environments and coming with a small footprint, they are available in a growing diversity of sizes and configurations. Sophisticated electronic controls and operator assistance devices are enhancing their safe and productive operation. While cranes occupy a central role on midrise and high-rise building projects, they operate in conjunction with other types of supporting equipment that are an essential part of the overall equipment array on today’s industrialized construction sites.

Fatal injuries in the United States construction industry involving cranes 1984-1994.

There is little published information concerning the epidemiology of injuries in the construction industry involving cranes other than for electrical injury from power line contact. For the 11-year period of 1984 through 1994, the US Occupational Safety and Health Administration (OSHA) investigated 502 deaths in 479 incidents involving cranes in the construction industry. Electrocution was the largest category, with 198 deaths (39%) reported. Other major categories were assembly/dismantling (58 deaths, 12%), boom buckling (41 deaths, 8%), crane upset/overturn (37 deaths, 7%), and rigging failure (36 deaths, 7%). The majority of the deaths during assembly/dismantling involved removal of the boom pins from lattice boom cranes. Only 34% of the construction firms employing the fatally injured workers had ever been inspected by OSHA. OSHA cited the employer for safety violations in 436 deaths (83%). Additional worker training, increased OSHA inspections, and crane inspection programs could prevent many crane-related deaths.