Roof Load Research Articles

Deformation and Fracture Mechanisms of Thick Hard Roofs in Upward Mining Coalfaces: A Mechanical Model and Its Validation

The safety and efficiency of underground coal mining are threatened by thick hard roofs characterized by large overhang areas, problematic spontaneous caving, and high dynamic load upon their breakage. In this study, a mechanical model of the bearing capacity of thick hard roofs in upward mining coalfaces associated with mining activities is built based on bending theories for beams with single generalized displacement and the elastic foundation beam theory. Using this method, we analyze the deformation and fracture mechanisms of a thick hard roof during upward mining. We further derive the mechanical equations of rotational angle, bending moment, shear force, and deflection of the free overhang and coal-bearing zone in the thick hard roof and an equation for calculating the limiting span. The mechanical behaviors of the thick hard roof bearing state are analyzed under different parameters. The results show that the foundation coefficient, roof thickness, and angle of upward mining have little influence on the roof bending moment but are positively correlated to the limiting span. Roof load and overhang length have a significant influence on the roof bending moment. They are negatively and positively correlated with the limiting span, respectively. Finally, a case study is performed on the Ш601 upward mining coalface in the Zhuzhuang Coal Mine. The distribution characteristics of the bending moment of the thick hard roof at different extraction stages are analyzed. At each stage, the limiting spans of the thick hard roof upon breaking were calculated as 13.18, 18.82, and 22.50 m, respectively, being close to the on-site measured periodic weighting lengths of 13.33, 19.33 m, and 22.67 m. This close fit proves the feasibility and accuracy of the developed mechanical model. The present study offers theoretical guidance for estimating the weighting length of thick hard roofs in coalfaces and for engineering technology control in similar scenarios.

Superhydrophobic foamed concrete based on response surface method: Mix design and its potential application in roofing systems

This study employs the response surface method to optimize the mixture design of superhydrophobic foamed concrete. The study investigates the influence of calcium stearate (CS, dosage 1 %∼5 %), polydimethylsiloxane (PDMS, dosage 2 %∼8 %), and hydroxypropyl methylcellulose (HPMC, dosage 0.05 %∼0.2 %) on various properties of foamed concrete, including density, compressive strength, contact angle, and water absorption. Additionally, the research explores the application of superhydrophobic foamed concrete in integrated roofing systems and assesses its thermal and structural performance through finite element analysis. Results reveal that foamed concrete achieves a contact angle greater than 150° when formulated with a mix ratio of CS (3 %), PDMS (8 %), and HPMC (0.05 %), or CS (3 %), PDMS (5 %), and HPMC (0.125 %). A negative linear correlation between the heat transfer coefficient and the thickness of foamed concrete is found. Furthermore, the heat transfer coefficient is inversely related to the spacing between the concave and convex drainage boards. Specifically, for a toe spacing of 50 mm and foamed concrete thickness exceeding 70 mm, the heat transfer coefficient of the roof measures 0.788 W/(m²·K). When the roof thickness increases from 70 mm to 100 mm, the roof heat transfer coefficient drops to 0.69 W/(m2∙K). When the toe spacing is increased from 50 mm to 60 mm, the heat transfer coefficient of the roof drops sharply to about 0.66 W/(m2∙K) at the thickness of 50 mm. The insulation requirements for the roof are satisfactorily met to 0.8 W/(m²·K). Under applied roof loads, the maximum von Mises stress experienced by the integrated roof is 0.6 MPa at a toe spacing of 50 mm. With the increase of the roof thickness, the maximum value of the DAMAGEC damage coefficient gradually decreases from 0.3 to 0.17. The maximum damage position has always been at the weak position of the four corners, which is consistent with the actual use status. The research findings on superhydrophobic foamed concrete have significant theoretical and engineering application value. Moreover, the construction of an "insulation/hydrophobic integrated" roof system demonstrates the feasibility of an integrated roof system and the potential for insulation/hydrophobic integration in roof system construction.

Deformation ability of modular gymnasium steel inner sleeve all-bolt cross connection joint based on 3D-DIC method

Immense roof loads present a significant hurdle for the functionality of continuously supported modular connection joints in movable modular gymnasium structures. Consequently, we introduced leveraging inner sleeves and bolts to interconnect the modular units of the upper and lower columns, aiming to bolster the strength of inter-unit connections. Despite its noteworthy benefits, the deformation behavior and force distribution characteristics of this novel design remain underexplored. Hence, our study employs three-dimensional digital image correlation (3D-DIC) measurement to precisely capture the full-field displacement and strain distributions within the core area of this joint. Four distinct joint specimens were designed, and conducted comprehensive static tests, encompassing variables such as the inclusion or exclusion of inner sleeves, reinforcing ribs, and diverse loading directions. 3D-DIC detected subtle deformations and local buckling phenomena, undetectable by the naked eye, and revealed their occurrence patterns. Furthermore, the detections underscore the critical role of weld quality between beams and columns in ensuring the overall safety of the joints. The joint exhibited earlier yielding in beam bending compared to column bending. To delve deeper into this joint, we generated moment-rotation curves leveraging DIC results, deducing that this joint exhibits rigid-joint characteristics. The specimens primarily showed damage modes such as beam-root fractures or member buckling, while the core area remained intact. This observation reinforces the classification of the joint as a full-strength entity. These insights enrich our comprehension of this novel joint and serve as invaluable references and aids for designers.

Determining patterns of the vertical load on a covered wagon roof with a frame in the form of a triangular arch

The object of this paper is the processes of perception and redistribution of loads in the roof of a railroad covered wagon with a frame in the form of a triangular arch. To reduce the tare of the covered wagon, it is proposed to improve the structure of its roof. A feature of this improvement is that the roof frame is made in the form of a triangular arch with a reinforcing belt. This contributes to the reduction of the total mass of the roof compared to a typical structure. The selection of execution profiles of the beams forming the arch is carried out according to the maximum values of the moments that act in their cross-section. Taking into account the chosen profile of the arches, the calculation of the strength of the roof when it receives vertical loads was carried out. It was established that the strength of the roof under the considered load schemes is within the permissible stress values. Since the improvement of the roof structure contributes to the reduction of its weight by 1.8 % compared to the prototype, the movement of the covered wagon was evaluated under conditions of moving while empty. To this end, a mathematical modeling of the load of the covered wagon in the vertical plane during its movement along the joint unevenness was carried out. On the basis of the performed calculation, it was established that the movement of the wagon is assessed as "good". Special feature of the results is that the reduction of the tare of the supporting structure of the wagon was achieved by improving its roof, as the least loaded unit. The field of practical application of the results is railroad transport, including other areas of mechanical engineering. The conditions for the practical use of the results are a symmetrical roof load scheme in operation. The results of this research could contribute to advancements related to the design of modern structures of freight wagons with improved technical and economic indicators

Damage analysis and mechanical performance evaluation of frame structures in recycling

Research on the recycling of space frame structures is beneficial to reduce the waste of resources and has important engineering application prospects. Repeated disassembly tests were carried out on a full size space frame structure with bolt-ball joints. The maximum number of cycles was 3. The test results showed that with the increase of the number of cycles, the damage of joints and tubes gradually increased, the phenomenon of false tightening increased, and the construction efficiency decreased. After three cycles, the damage of high-strength bolts accounted for 16.56 % and the damage of steel tubes accounted for 5 %. Due to the component damage and construction deviation, the deformation and stress of the structure after unloading could not be restored to that before loading. However, within three cycles, the overall displacement and stress of the frame structure under general roof loads were almost not affected by component damage and construction deviation. Furthermore, the distribution pattern of displacement and stress was independent of the number of cycles. The maximum mid-span displacement of the structure was about 80 mm and the maximum difference of the overall stress level was within 10 MPa. Finally, according to the test results, the relevant engineering suggestions for the recycling of space frame structures were put forward.

Seismic analyses of single-layer dome structures with random geometrical imperfections under stochastic ground motions

In this paper, seismic analyses of single-layer dome structures are carried out, with a particular emphasis on the incorporation of randomness in both geometrical imperfections and ground motions. First, the paper introduces models for random geometrical imperfections and stochastic ground motions, employing the Stochastic Imperfection Mode Superposition Method (SIMSM) for imperfections and utilizing the Spectral Representation Method (SRM) for ground motions. These models are designed to comprehensively account for the inherent uncertainties in real-world structural behavior. Subsequently, the Probability Density Evolution Method (PDEM) is applied to investigate the probabilistic response and seismic reliability of dome structures, which allows for a detailed examination of key performance indicators, such as displacement, plastic ratio, and strength damage, under the influence of random factors. Both deterministic and stochastic analyses are conducted to gain insights into the impact of randomness in geometrical imperfections and ground motions. The computational results unveil a crucial finding: an unfavorable distribution of imperfections can significantly compromise the dynamic performance and safety of single-layer dome structures. Furthermore, the paper delves into parametric analyses, with a specific focus on imperfection amplitude, the rise-span ratio and roof load as pivotal parameters. These analyses provide valuable insights into the sensitivity of the structural response to variations in these critical design factors.

Industrial Building Structure Planning With Cranes

Industrial building structure planning complies with standards and regulations, such as Procedures for Earthquake Resistance Planning, Minimum Loads for Building Design, and Specifications for Structural Steel Buildings. Vertical and lateral loads are fundamental to the structure's load flow process. Industrial buildings handle roof, wind, earthquakes, crane, and wall loads. Structural design must consider these elements, including the choice of lateral force-resisting systems such as X-bracing. In determining building loads, including earthquake and wind loads, various parameters such as wind speed, exposure category, and other factors must be considered by standard requirements such as SNI 1727-2020 and SNI 1726:2019. Selection of site class, wind direction, topographic, and ground surface elevation factors are essential in determining wind loads. This research method focuses on supporting structures consisting of purlins and girts in the context of industrial buildings. Purlins, made from hot or cold rolled steel, generally use C and Z profiles. Girts, made from cold or hot rolled steel, have profile variations such as C, Z, or hollow square sections. The girt structure design process determines dimensions, rod sag, internal requirements, and sag rod capacity.

Deformation Analysis of Desalinated Water Storage Tank Using Finite Element Method

Deformation in a structure is something that is very likely to occur when the object is subjected to a loading that leads to a pressure on the object. The approach taken to determine the deformation of the cylindrical tank was carried out using the finite element method using Ansys 2020 R2 software with axial loads due to the roof and circumferential loads on the cylinder from wind forces. The cylindrical tank that was the object observed in the practical work field was found to be deformed due to the very high loading from the roof and also the result of re-welding due to the repair of defective welds after being examined by ultrasonic testing. This was investigated using the finite element method to determine if the loading experienced by the cylinder was the main cause of the deformation and it was found that the maximum deformation was so small that it was difficult to say that the main cause of the deformation was the loading. It is known that re-welding a metal will change the mechanical properties of the material to become softer, which is the main reason why the deformation of the tank occurred in the practical field.

Mechanical performance study of a novel modular gymnasium inner sleeve all-bolt cross connection joint – part Ⅰ: Experiments and finite element modeling

The authors propose a novel movable modular gymnasium based on modular building technology to meet people's sports needs. However, the huge roof load puts higher requirements on the performance of modular units and their connecting joints. In light of this, the authors propose a novel connection joint using the inner sleeve and bolted connections, which connect the upper and lower columns of the modular unit to give it higher performance. In addition, it connects the upper and lower beams of the modular unit by bolts to improve its overall performance. The authors evaluated the mechanical properties of the connecting joints through experiments and simulations. The results indicate that the welding quality determines the beam-oriented bearing capacity of the connections while having little impact on the column-oriented bearing capacity. It is difficult for the inner sleeve to enhance the initial stiffness and beam-oriented bearing capacity of the joints due to the initial gap between the inner sleeve and the modular column. The restraint effect of the stiffening ribs induces the deformation of the inner sleeve, and its bearing capacity increases up to 91%. The inner sleeve improves the column-ward bearing capacity and deformation capacity of the joints, and its bearing capacity rises to 135%.

Experimental and numerical simulation study of mechanical properties of inner sleeve T-joint in modular gymnasia

In response to the contradiction between the insufficient number and unreasonable distribution of stadiums in cities and the increasing demand of people for fitness, the authors propose movable modular gymnasiums. This gymnasium takes advantage of the modular building, which can be quickly built, dismantled, and reassembled to fully utilize the temporary empty land in the city to meet the fitness demand of the people. However, the box modules bear a huge roof load, which puts higher demands on the performance of the modular units and their connecting joints. This study proposes a novel joint using an inner sleeve and bolted connections. The proposed connection uses an inner sleeve and bolts to connect the upper and lower columns of the modular unit to give it a higher bearing capacity. Bolts connect the lower unit's ceiling beam and the upper unit's floor beam to provide a better overall performance of the modular unit. The authors conducted experimental studies of 2 full-scale models and 24 finite-element parametric analyses. The results show that the welding quality determines the beam-ward bearing capacity of the joints, while it has little effect on the column-ward bearing capacity. In practical engineering, the authors suggest that the initial stiffness of the joints does not consider the contribution of the inner sleeve. The setting of stiffening ribs forces the inner sleeve to deform and force, improving the joints' mechanical properties, with the initial stiffness in the column direction increase of 25 %, the initial stiffness in the beam direction increase of 31 %, and a bearing capacity in the beam direction increase of 38 %. The design thickness of the inner sleeve and stiffening ribs should be close to the wall thickness of the modular beam and column. The results of this paper contribute to the development of fitness for the whole population and the expansion of the application of modular buildings.

Stability Analysis and Control Methods of a Layered Roof of Gob-Side Entry in Inclined Rock Strata.

In view of the instability of a layered roof of the gob-side entry in inclined rock strata, with the engineering background of the gob-side entry with a small-width coal pillar in Xutuan Mine, the deformation and failure characteristics of the layered roof and the control measures in inclined rock strata are studied by comprehensively adopting field investigation, numerical calculation, theoretical analysis, and engineering tests. The results show the following. (1) After the instability of the layered roof, an unstable zone, a substable zone, and a stable zone are formed accordingly in the surrounding rock from shallow to deep. The unstable zone is an active area in terms of roof deformation and is the main object in the surrounding rock control. The substable zone has a macro control effect on roof deformation. The stable zone is the main bearing structure of the roof. (2) The rock structure has a significant regulatory effect on roof deformation and damage. As the thickness of the layers increases, the bearing capacity of each layer increases and the overall strength of the roof increases. At the same time, the influence range of the substable zone increases, which has a restraining effect on the expansion of the unstable zone. (3) The maximum deformation of the roof decreases exponentially with the increase in thickness of the roof rock beam, increases linearly with the increase in lateral pressure and roof load, and increases exponentially with the increase in entry span. (4) Based on the "two enhancements and one weakening" surrounding rock control strategy, a support system with "high-strength bolts and cables, shotcrete, and anchor grouting" as the core is proposed. The results of field tests indicate that the designed support scheme effectively controls the deformation of the layered roof and achieves long-term stability of the gob-side entry with a small-width coal pillar.

Stability control of overburden and coal pillars in the gob-side entry under dynamic pressure

To improve the recovery ratio of coal resources and stress environment of the roadway, gob-side entries have been widely implemented to numerous coal mines in China. Traditional gob-side entry is generally excavated after the gob of the adjacent longwall face is stabilized. To achieve a balance between the seam mining and roadway excavation, numerous mine coals use the method of driving a roadway along the next gob, which heads adjacent to the advancing coal face, and maintaining a narrow coal pillar. Consequently, the dynamic pressure occurs at the gob-side entry; accordingly, the difficulty of roadway maintenance is increased. However, the traditional gob-side entry stability analysis is not applicable to a gob-side entry under dynamic pressure. In this study, the overburden structural model and coal pillar stress model of a gob-side entry under dynamic pressure were established considering the compression load of the immediate roof and gangue and influence law of the cantilever beam length of main roof. Subsequently, thickness, hardness, and deformation of the immediate roof on the stability of the gob-side entry were studied, and the theoretical criterion for the stability of “voussoir beam” structure and coal pillar of the gob-side entry under dynamic pressure were proposed. Based on the geological conditions in tailgate # 110505 of the Yushuling coal mine, reasonable measures were taken considering the aspects of roof cutting and pressure relief, coal pillar design, and surrounding rock reinforcement. After applying the proposed measures, the width of the coal pillar was reduced from 15 m to 4 m. Meanwhile, the grouting cable beam was used to strengthen the roof, and the narrow coal pillar was reinforced by a bidirectional grouting anchor cable was developed. As a result, after the roadway was stabilized, the roof-to-floor convergence and two-side convergence were 268 mm and 105 mm, respectively. Moreover, the stress concentration factor of the coal pillar was 1.20. The stability characteristics of the overburden and coal pillar of the gob-side entry under dynamic pressure were effectively controlled, and remarkable economic benefits were obtained in this coal mine. The techniques proposed for maintaining the stability of the 4 m wide coal pillar and ensuring the bidirectional grouting reinforcement have been successfully applied in a coal mine for the first time, which have high innovation and application values. This study provides a reference for the design and maintenance of the gob-side entry under dynamic pressure.

Study on Failure Mechanism and Support Design of Tunnel Surrounding Rock

Taking a tunnel as the engineering background, this paper focuses on the mechanism of large deformation of soft rock, the design and optimization of supporting technology, aiming at the problem of large deformation of tunnel surrounding rock. By means of numerical simulation, the failure mechanism of structural large deformation of layered surrounding rock is deeply analyzed and studied. The tunnel is simulated with different support parameters to find more reasonable support parameters and optimize the existing support. The results show that the displacement of surrounding rock increases with the increase of upper load. When the roof load is less than 0.7 MPa, the vertical displacement of the sensitive block tends to be stable after a certain period of time; When the top plate load is 0.7 MPa, the vertical displacement of the roof sensitive block cannot converge, so some reinforcement measures must be taken at this time. When the tunnel is supported by bolts, the longer the length of bolts, the better the effect will be. 3m anchor length should be selected for support, and other support methods should be added to control tunnel deformation.

Management strategies for maximizing the ecohydrological benefits of multilayer blue-green roofs in mediterranean urban areas

Multilayer Blue-Green Roofs are powerful nature-based solutions that can contribute to the creation of smart and resilient cities. These tools combine the retention capacity of traditional green roofs with the water storage of a rainwater harvesting tank. The additional storage layer enables to accumulate the rainwater percolating from the soil layer, that, if properly treated, can be reused for domestic purposes. Here, we explore the behavior of a Multilayer Blue-Green Roof prototype installed in Cagliari (Italy) in 2019, that have been equipped with a remotely controlled gate to regulate the storage capacity of the system. The gate installation allows to manage the Multilayer Blue-Green Roof in order to increase the flood mitigation capacity, minimizing the water stress for vegetation and limiting the roof load with adequate management practices. In this work, 10 rules for the management of the Multilayer Blue-Green Roof gate have been investigated and their performances in achieving different management goals (i.e., mitigating urban flood, increasing water storage and limiting roof load on the building) have been evaluated, with the aim to identify the most efficient approach to maximize the benefits of this nature based solution. An ecohydrological model have been calibrated based on field measurements carried out for 6 months. The model has been used to simulate the system performance in achieving the proposed goals, using as input nowdays and future rainfall and temperature time series. The analysis reveled the importance of the correct management of the gate, highthing how choosing and applying a specific management rule helps increasing the performance in reaching the desired goal.

Pengkinian Konstruksi Joglo Tanpa Empat Saka Guru

Title: Updating Joglo Construction Without Four Saka guru (Case Study of Pendopo Pura Agung Blambangan of Banyuwangi) Current architectural developments to maintain its sustainability have reached the awareness stage to explore the potential for the diversity of archipelago architecture, one of which is exploring the potential for the Joglo traditional house for the future. The demand for wide spans often comes to the fore, so it is not uncommon for new construction designs to respond to the demands for wide spans free from pillars. However, a solution is needed to solve this problem. The pillars and their frames are the main part of the main reinforcement system for the roof load as a whole, so they become prerequisites on behalf of the Joglo. This writing aims to analyze the updated form of construction without pillars that still maintain the Joglo form. The research method uses a qualitative descriptive approach by examining the process of eliminating the four pillars of teachers by analyzing the reliability of the structural system of the Puri Agung Blambangan pavilion and the Sabha Swagata Blambangan pavilion in Banyuwangi, East Java. The research results show how the construction of the four pillars and their frames are believed to be the main strength to withstand the roof’s weight. The construction system without the four pillars of the guru and their frames reduces the rigidity of the building because the strength is transferred to the pillars on the edges of the building and does not reflect the joglo structural and construction system. Many knot points have appeared without the pillars and the framework of a construction system, increasing the risk of collapse.

Failure Mechanism and Stability Control of Soft Roof in Advance Support Section of Mining Face

There is a great risk of roof falls in the advance support section of the mining face (ASSoMF), and it is difficult to control the roof. Based on the soft roof of Lijiahao coal mine, this paper studies the stress distribution of the ASSoMF and the space-time evolution of the surrounding rock plastic zone by using theoretical analysis and numerical simulation, and reveals its failure mechanism. Based on the control effect of support resistance on plastic zone, it is proposed that the advance support should mainly adapt to the roadway deformation. Advance equipment without repeated support for mechanized movement has been developed, and the support timing analysis and strength check have been carried out. Results show that the roadway at ASSoMF is in a non-uniform stress field, the confining pressure ratio reaches 1.5~7, and the surrounding rock forms asymmetric failure; the principal stress direction deflects, the angle between it and the vertical direction is about 10°~25°, and the plastic zone of the surrounding rock also rotates to the roadway roof. The proposed equipment can adapt to the characteristics of an unsymmetrical large deformation of a soft roof, and can effectively bear the roof load and maintain the stability of the roadway.

Research on Roof Load Transfer by Passing Coal Pillar of Working Face in Shallow Buried Closely Multiple-Seam

The dynamic load effect of supports is mainly caused by the movement of the roof structure and the load transfer of overburden. In view of the practice issue that the phenomenon of strong ground pressure is easy to happen, when the working face of the lower coal seam passes the inclined coal pillar in shallow buried closely multiple-seam, it will lead to supprot damaged. This paper takes the mining of over-inclined coal pillars in the 22410 working face of the Bulianta Coal Mine as the background, based on the research method combining the field measurement, physical simulation experiment, and numerical calculation, the evolution law of the front abutment pressure (FAP) and roof weighting in mining under the inclined coal pillar is analyzed, and the mechanism of the stress transfer of the inclined coal pillar and the dynamic load of the support is revealed. The research shows that the concentrated stress of the coal pillar is jointly borne by the front coal wall of the working face and the interburden structure above the support. The vertical stress transmitted from the coal pillar to the floor acts on the key blocks of the interburden of the lower coal seam, which causes strong pressure and dynamic load effect, such as roof structure cut-off. The periodic breaking of the key stratum of the interburden leads to the development height and range of the cracks increasing stepwise. The partition characteristics of the mutual transformation of the interburden stress, the FAP, and the working resistance (WR) by passing the coal pillar stage are revealed, which is divided into three stages and four regions. With the working face passing through the inclined coal pillar, the influence area of the concentrated stress of the coal pillar is reduced, and the peak stress of the coal pillar is gradually transferred to the outside of the coal pillar. When the working face is 5 m away from the coal pillar, the peak of FAP and WR reaches the maximum values, the roof is cutting along the peak stress line, and the working face has a strong weighting phenomenon. The research results are consistent with the field measurement results, providing a reference for the mining of working faces under similar conditions.

Optimización de la rigidez equivalente en estructuras de uno y dos pisos sometidas a cargas de techos verdes

Desde una perspectiva lineal y estática, el aumento de los desplazamientos de una estructura debido a la implementación de un techo verde podría ser contrarrestado con el incremento de la rigidez de la estructura. En este artículo se plantea el uso del algoritmo de evolución diferencial para optimizar la rigidez equivalente de una estructura de uno y dos pisos de altura, variando la carga de techo verde bajo el análisis de fuerza horizontal equivalente en la ciudad de Bogotá. A través del software MATLAB se programa y acopla el algoritmo de optimización y la metodología de análisis matricial de estructuras aporticadas tridimensionales sujetas al cumplimiento de la distorsión máxima de piso propuesta por la normativa de construcción colombiana. Un incremento máximo en la rigidez equivalente de 19.25% y 57.80% (estructuras de un piso), y de 11.12% y 32.97% (estructuras de dos pisos) para pesos de techos verdes de 100 kg/m2 y 300 kg/m2 respectivamente, es necesaria para cumplir requerimientos normativos. Se espera que esta investigación sirva como punto de partida para generar soluciones constructivas a la implementación de techos verdes en estructuras de uno y dos pisos en la ciudad de Bogotá.

Investigation of geomechanical properties of tephra relevant to roof loading for application in vulnerability analyses

Tephra fall can lead to significant additional loading on roofs. Understanding the relevant geomechanical properties of tephra is critical when assessing the vulnerability of buildings to tephra fall and designing buildings to withstand tephra loads. Through analysis of published data and new experimental results on dry tephra (both natural samples from Ascension Island, South Atlantic and synthetic tephra made from crushed aggregates), we discuss the geomechanical properties of tephra relevant to roof loading, which include bulk density, grain size distribution and internal angle of friction. Compiled published data for deposits from 64 global eruptions reveal no clear trend in deposit densities based on magma composition or eruption size. The global data show a wide range of values within single eruptions and between eruptions of similar compositions. Published grain size distributions near to source (≤ 10 km) vary widely but again there are no clear trends relating to magma composition. We used laboratory tests to investigate the internal angle of friction, which influences deposit sliding behaviour. For dry tephra, at the low normal stresses likely to be experienced in roof loads (≤ 35 kPa), we found similar values across all our tests (35.8° - 36.5°) suggesting that any internal sliding will be consistent across a variety of deposits. By considering different magma compositions, densities and grain size distributions, we have provided an envelope of values for deposit parameters relevant to roof loading, in which future eruptions are likely to sit. Finally, we created synthetic tephra (fine- and coarse-grained pumice and scoria) by crushing volcanic aggregates and compared it to samples from Ascension and published data. Our results reveal that synthetic tephra successfully replicated the properties relevant to loading, potentially reducing the need to collect and transport natural samples.

Application of Function Analysis using Function Analysis System Technique (FAST) Diagram on Taman Sari Apartment Construction Project

Construction projects require costs as a very important element in their implementation. There are several alternative methods that can be used as a rationale for conducting studies on cost savings. One of the alternatives that can be used for savings by eliminating unnecessary costs so that the value of the project can be reduced is Value Engineering (value engineering). One of the important stages in VE is the analysis of functions whose purpose is to identify the functions that are most beneficial for the study of VE. The method used in the analysis of this function is the Function Analysis System Technique (FAST) Diagram with the aim of defining the function of each work item analyzed and can review the basic functions that are used as guidelines in the selection of alternative designs for cost savings. In the Taman Sari Apartment construction project, a function analysis was carried out on high-value work items, namely structural work, frame work, door and window leaves, wall work, floor work and roof covering work. On the work of the structure identified the basic function of the work of the structure is to plan an alternative design with outputs in order to obtain cost efficiency. Then in the work of the frame, door leaves and windows have the basic function of planning an alternative design with output to be able to provide space access. Wall work with basic functions as a room divider to provide comfort and privacy as the resulting output. In floor work with the basic function of closing the floor base and the output is to beautify the room. For roof covering work has a basic function by calculating the roof load and output to obtain cost efficiency. After the implementation of the functioning analysis stage, cost savings are carried out by identifying and reducing unnecessary costs without reducing the quality and function level of the project it self.