Current Issue : April-June Volume : 2023 Issue Number : 2 Articles : 5 Articles
Lattice girder slab (LGS) is a precast composite slab that serves as an alternative to conventional concrete-in-place (CIP) slabs. The load-bearing capacity of joints for the LGSs is essential for large-span slabs with precast constructions, while limited connections could achieve both free-of-formwork construction and higher flexural bearing capacity. In order to enhance the flexural behavior of LGSs with free-of-formwork joints, the straight bar lapping connection away from the midspan, loop connection, and straight bar lapping connection within keyway for midspan joints were proposed in this study. Seven full-scale one-way LGSs with different transverse connections were tested under the four-point bending tests to investigate the joint behavior. The overall response and failure mode were observed during the test. The load versus midspan deflection, deflected shape, and characteristic load capacity were analyzed and discussed. The study showed that all the slabs’ deformability could reach as high as l/50 without load reduction. The LGS with the straight bar lapping connection in the midspan had the lowest flexural capacity (70% of the capacity for LGS without joints), while the flexural resistance of the slabs with other connections could be increased by 21.4% to 44.6% compared to LGSs with the traditional straight bar lapping connection in the midspan. The LGSs with the connections having keyways had the most significant improvement and could achieve high flexural capacity and 110% of deformability of the LGS without joints. The findings could enrich the connection types for LGSs for construction convenience and mechanical efficiency and further provide reference for the design of the two-way LGSs....
Road construction often focuses on the use of conventional materials. Due to the depletion of these conventional materials, this cannot be always true. To overcome such problems, several alternative construction materials have been proposed as sustainable solutions. Thus, this study has investigated the potential use of volcanic ash (VA) as an alternative filler material in hot mix asphalt. The investigation has used laboratory scale and purposive sampling method for sample collection. The plastic index and specific gravity of volcano ash are 0.92% and 2.44, respectively. The chemical composition analysis indicated that VA is a class-N pozzolana material. Maximum stability of 11.38 kN was obtained at full replacement of volcano ash. The tensile strength ratio of the mix at full replacement of CSD and volcanic ash is 82% and 98%, respectively. From the fatigue resistance analysis, the probable failure of pavement constructed with the mixture containing VA could be improved from 16600 to 14400. Due to its rough surface, VA has better bonding ability with bitumen compared to CSD. The mix prepared from VA has less deformation tendency than that prepared from CSD....
This paper analyzes two tailings dam databases and recent failures to assess the local and global failure rates of upstream, downstream, and centerline raised tailings dams. Since 2000, the failure rate for all three raising methods has decreased except in Brazil, which helps explain the recent Brazilian regulations banning upstream raising. However, the failure rates also show that the downstream and centerline raising methods of tailings dams are not immune to failure, so, if mining continues, one of these three raising methods will be used, and all have been involved in prior failures. The paper also presents data on failure mechanisms, showing that slope stability, earthquakes, and overtopping are the three primary causes of tailings dam failures. To continue decreasing the failure rate of tailings dams, the following features and practices should be used in all types of tailings dams: drainage systems, engineering analyses, instrumentation, monitoring, inspection, and qualified external peer review to further reduce the failure rates, especially in Brazil. Finally, a section containing data on release volume as a function of dam height and total storage volume is presented....
The jacking force is one of the important parameters affecting the construction process in the vertical tunnelling method. To study the dynamic changing process of jacking force with the jacked distance and the influencing factors of the maximum jacking force, both the indoor model test and numerical simulation were conducted. In the model test, we investigated the influence of the height of the soil and water content. The results indicated that the higher the overburden height was, the greater the jacking force. Moreover, the water content enhanced the compressibility of the soil and had little effect on the maximum jacking force. Additionally, the coupled Eulerian–Lagrangian (CEL) approach was used to simulate the vertical jacking construction. In the numerical simulation, we investigated two construction factors (jacking speed and the standpipe outer diameter) and four soil parameters (cohesion, internal friction angle, elastic modulus, and Poisson’s ratio). Before that, the CEL simulation results were compared with test data to prove the rationality of the CEL approach, and the two were in good agreement. The results showed that among the six influence parameters, according to the influence degree on the maximum jacking force from large to low, the outer diameter of the standpipe, internal friction angle, cohesion, elastic modulus, jacking speed, and Poisson’s ratio were ranked. In addition, the jacking speed of numerical analysis was suggested to be 0.2 m/s. The research results in this paper can provide a reference for the construction of the vertical tunnelling method....
In order to calculate the vehicle load model of Baijianhe Bridge, based on the vehicle load data of the health monitoring system, the vehicle type, vehicle weight, wheelbase, and other information were counted and the data were processed and diagraphed to obtain the probability density distribution. At the same time, the automobile load model parameters relative to the national current code and finite element method are calculated. The results show that 2-axle and 6-axle vehicles are the main vehicle types, accounting for about 48%. The number of upstream and downstream vehicles is the same, but the number of vehicles in the lane is much higher than in the overtaking lane. The carriageway is dominated by 6-axle vehicles, while the overtaking lane is dominated by 2- axle vehicles. The probability density distribution of vehicle weight in overtaking lane obeys mixed Gaussian distribution and that in the carriageway obeys Weibull distribution. According to the measured vehicle load data, the vehicle load suitable for Baijianhe Bridge is 1.1 times the highway-I vehicle load of the current Chinese standard “General Code for Design of Highway Bridges and Culvers” (JTG D60-2015)....
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