The paper proposes an improved design of a shock absorber used in drilling deep oil and gas and geothermal wells with polycrystalline diamond compact (PDC) bits. The proposed innovations successfully combat the dangerous phenomenon of self-excited vibrations, which can lead to malfunctions such as stick-slip and whirling of the drilling tool. Most conventional drill shock absorbers are designed to only absorb longitudinal vibrations, which was sufficient when using roller cutter bits for the drilling process. However, the design features of PDC bits and the phenomenon of interaction of their cutters with interlayered rocks during deep drilling impose new requirements on the properties of the drill shock absorber. To protect the downhole tool from abnormal torque values and torque oscillations, it is proposed to equip the shock absorber with a special torque transmission unit in the form of a fourteen-thread self-releasing screw pair. This unit is capable of transforming increases in external torque into increases in the force that loads the elastic element of the shock absorber. The numerical and analytical models of the mechanism of transferring external axial load and torque to the elastic element of the drill shock absorber are constructed. The distribution of contact pressures on the interacting surfaces of the screw pair and the distribution of equivalent stresses in the screw pair parts are analysed. The strength of the proposed drill shock absorber assembly was evaluated using the Huber-von Mises energy criterion. The dependence of the load transmitted to the elastic element of the shock absorber on changes in the external torque and external axial force is investigated. In general, it is determined that the external load is distributed evenly between all turns of the screw pair, and the limit state of the parts of the proposed assembly is not reached even under high-torque operating load. The obtained analytical dependencies will allow to effectively determine the required strength and stiffness of the elastic element of the drill shock absorber at the design stage. The obtained analytical results were verified using a finite element model.

The public's demand for simple, livable houses means that material studies to support this continue to be carried out today, starting from using natural materials such as bamboo as precast concrete walls. This study aims to conduct an experimental study using bamboo rope from the Gigantochloa Apus variety as an alternative reinforcement for precast concrete walls. Research was carried out on 12 precast concrete wall test specimens, and the flexural properties, flexural strength, and crack patterns were formulated when subjected to a quasi-static load concentrated in the middle of the span. The concrete slab measures 600800 mm with a 50 and 75 mm thickness. The three configurations of bamboo bones used include (1) Gedhek-type woven bamboo slats, (2) bamboo slat type, and (3) Sasak-type woven bamboo slats. The research results show that Sasak-type woven bamboo slat reinforcement is the most effective alternative reinforcement. The behavior of the test specimen shows a ductile failure pattern similar to conventional reinforced concrete. The maximum moment capacity achieved is 1.5 to 2.2 times greater than the theoretical nominal moment capacity. Meanwhile, the behavior of test specimens with conventional plate-type woven bamboo slat reinforcement showed sudden and brittle failure due to slippage at the bond between the bamboo reinforcement and concrete. The average maximum moment from the test results is 60% of the theoretical nominal moment. The results of this research recommend that woven bamboo slats of the conventional plate reinforcement type are less effective as alternative reinforcement if they are not given special treatment to increase their adhesion to concrete. Gedhek-type woven bamboo slats are not effective as alternative reinforcement because they cause separation of the top and bottom parts of the woven concrete, thereby reducing the integrity of the cross-section and causing the cross-sectional capacity to be relatively small.

The source of financing largely determines the implementation of road maintenance. Due to the limited funding capacity of the Regional Government, the performance of road maintenance cannot be handled throughout the provincial road network, so it is necessary to determine the priorities and types of maintenance that must be performed carefully and accurately following the conditions. Therefore, this article conducts a study to determine the priority scale in road maintenance in the province of Lampung (Indonesia), which is limited by the government's financial capacity to make comprehensive improvements through a multi-criteria analysis approach. The approach used is a survey method with purposive sampling, integrated with a multi-criteria analysis approach to find eigenvalues as a priority for improvement. There are at least eight groups with 238 respondents who provide input in determining the priority of road preservation in the province of Lampung. The results show that there are ten main parameter criteria to assess the implementation of road preservation in the Lampung province, including accessibility, social, regional development, economy, number of vehicles, security, congestion, road damage, road safety, and regional disparities. The results of the calculation of the multi-criteria analysis of the parameters found that the "road damage" parameter has the highest weight or eigenvalue. The following parameter that becomes the main consideration is the economic aspect and accessibility, with the second and third largest eigenvalues. The security parameter is a factor that is not considered because it is ranked the lowest.

This article originates from an experimental program and nonlinear finite element analysis aimed at examining how pozzolanic concrete influences the behavior of RC shear walls with openings. To achieve this, stress-strain diagrams, and the elastic modulus of 33 cylindrical concrete specimens, each containing varying percentages of silica fume and zeolite (ranging from 0% to 25%), were evaluated. The impact of silica fume and zeolite pozzolans on the ductility and load-bearing capacity of RC shear walls with openings was explored. This was done by analyzing the mechanical properties of the specimens and integrating them into the analytical model. Subsequently, a shear wall with conventional concrete was simulated using the finite element method (FEM). The study delved into the effects of substituting the initial concrete with pozzolanic concrete within the shear wall. Additionally, it investigated the simultaneous reduction in the diameter of the reinforcing bars employed, all in the pursuit of attaining the optimal design for these walls. The findings demonstrated that employing pozzolanic concrete in shear walls, coupled with a balanced configuration of rebar, led to heightened ductility, improved energy absorption, and an enhanced load-bearing capacity for the walls.

The wooden trolley (in the sawing line using a vertical bandsaw) during work generally moves by iron wheels on two rails placed on the concrete floor. Due to the effect of noticeable cutting force applied by the saw blade and the vehicle's uneven weight on the wheels, it causes the vehicle to vibrate during the horizontal movement, affecting the stability of the wood sawing circuit. By modeling the problem of vibration of beams located on Winkler elastic foundations, subjected to mobile concentrated loads, the article has built a system of differential equations of vibration of two rails, giving an expression to calculate the vibration amplitude of the swan plane. The influence of the flexural rigidity EI of the rails and the elastic stiffness k of foundation on the vibration amplitude of the cutting plane is studied and analyzed. The use of the Dirac Delta function and the employed analytical solution allow the designers to evaluate the accuracy and reliability of the calculated results.

This study investigates the tensile behavior and crack repair of aluminum using fiberglass-reinforced composite patches. Tensile testing compared uncracked, pre-cracked, and repaired aluminum specimens. Pre-cracking by hole drilling decreased strength and ductility from stress concentrations. Composite patching recovered strength, with 4-ply laminates optimal. Uncracked samples failed by necking, pre-cracked by crack growth, and repaired by adhesive detachment. Results demonstrate composite patching effectively restores strength to cracked aluminum by mitigating stress concentrations when appropriately designed. Finite element modeling simulated stress reduction after patching. This work provides experimental data on composite patch performance for metal crack repair and confirms the approach as an effective strengthening technique, although further optimization is needed.

This paper investigates various techniques used to solve the differential equations governing the free vibration of columns. The present work focuses on the study of the free vibration of Euler’s Bernoulli column of equal strength in compression, considering its own weight and the axial load in compression and tension while subjected to symmetrical boundary conditions. The investigation utilizes the differential quadrature method to examine the fifth natural frequency parameters of the column in different states of column boundary conditions and varying geometric section shapes, including pin-pin and clamp-clamp configurations. The results of this work contribute valuable insights for informed decisions on selecting the cross-section types and appropriate boundary conditions for ensuring the stability of such columns in civil constructions.

Connection designs are established to ensure the stability of joined cut sections, the joints so designed should be based on the optimal performance as per the requirements. The connection joints so established should not be based on just strength but reliability and durability as well. This study focuses on tackling one of the major issues faced when using Glass Fibre Reinforced Polymers (GFRPs) as construction materials, which is based on the abrupt failure of the material under critical or maximum loading. Connection designs are established in GFRP short column H-sections based on Bolted Splicing connections by Eurocode 3 for steel splicing connections. A total of seven Connection designs are established using bearing and non-bearing splicing connections. A total of five models for each connection is established for manual testing and Finite Element Analysis (FEA) is used to simulate and analyze these connection designs. Parameters such as ultimate load, displacement at ultimate load, stiffness, compressive strength, failure mode, load versus displacement behavior graph, and percentage compressive strength compared to the un-cut section are provided in this study. The strongest specimen in this study displaced 128% and 127.7% compressive strength compared to an un-cut GFRP H-section when tested using manual testing and FEA accordingly.

Beam-column joints play an important role in the overall resistance of reinforced concrete frames during seismic events. The Earthquakes of Al Asnam on October 10, 1980, and Boumerdes on May 21, 2003 in Algeria, have highlighted the failure of beam-column joints as a cause of building collapse. 3D nonlinear finite element analysis with ANSYS software has been used in order to examine exterior RC beam-column joints under monotonic loading. The research has investigated the influence of the value of the column-to-beam strength ratio (CBSR) of these joints on shear strength and seismic performance of concrete structures by changing the height and longitudinal reinforcement of the beam while keeping column dimensions constant. It has been shown that the beam-column depth ratio and the beam longitudinal reinforcement ratio have a significant effect on the shear capacity and seismic behaviour of exterior beam-column joints. An appropriate value of the flexural strength ratio between the column and beam is crucial in order to establish a "strong column-weak beam" mechanism in reinforced concrete frames, because inadequate values can lead to premature failure or reduced shear capacity at the junction. The Algerian seismic code – RPA99/version2003 suggests a minimum value of column-to-beam strength ratio equal to 1.25 at joints for seismic design when building codes in other countries call for higher ratios. Nevertheless, this approach might not accurately represent the actual behaviour and could constrain the optimal performance of structures.

For several offshore installations, especially those for exploration of offshore resources, such as Floating Production Storage and Offloading (FPSO), the stability of subsea pipelines and exploration risers are closely related to the mooring system. High performance polymeric fibers have been used in recent decades for offshore mooring, more recently polyester has been challenged by advancement in ultra-deep waters due to its considerable elongation. A candidate fiber for lower elongation mooring systems is high modulus polyethylene (HMPE). The work describes mechanical characterization procedures in high modulus polyethylene fibers envisioning the possibility of offshore mooring systems made entirely with HMPE, which allow deeper water depths, as well as stability to the pipelines. As a result, the fiber is suitable for mechanical strength and linear tenacity. It still shows good performance in abrasion resistance, and loss of inelastic portions in cyclic loads. However, the behavior in creep, due to its slightly high strain rates, restricts its use, but recent fibers known as "Low creep" can be studied, allowing complete mooring systems made with HMPE.