Roof Load Research Articles

Effects of viscous damping models on a single-layer latticed dome during earthquakes

Rayleigh damping model is recommended in the recently developed Performance-Based Earthquake Engineering (PBEE) methodology, but this methodology does not provide sufficient information due to the complexity of the damping mechanism. Furthermore, each Rayleigh-type damping model may have its individual limitations. In this study, Rayleigh-type damping models that are used widely in engineering practice are discussed. The seismic performance of a large-span single-layer latticed dome subjected to earthquake ground motions is investigated using different Rayleigh damping models. Herein a simulation technique is developed considering low cycle fatigue (LCF) in steel material. In the simulation technique, Ramberg-Osgood steel material model with the low cycle fatigue effect is used to simulate the non-uniformly distributed material damping and low cycle fatigue damage in the structure. Subsequently, the damping forces of the structure generated by different damping models are compared and discussed; the effects of the damping ratio and roof load on the damping forces are evaluated. Finally, the low cycle fatigue damage values in sections of members are given using these damping models. Through a comparative analysis, an appropriate Rayleigh-type damping model used for a large span single-layer latticed dome subjected to earthquake ground motions is determined in terms of the existing damping models.

Study of roof stability of the end of working face in upward longwall top coal

Low recovery of longwall top coal caving (LTCC) remains one of the most difficult engineering problems in this mining method and impedes its application. The top coal left in the gob at face end accounts for a large portion of the total coal loss, and the instability of the leftover triangle coal at face end has long been a threat to the safety of miners and the mining equipment. In this paper, based on the engineering background of Ruilong mine, we explore the stability of the roof at the end of the face by using theoretical analysis, numerical simulation, and field measurement. Results reveal that in the inclined longwall top coal caving face, the immediate roof forms an “arch” structure, and the basic roof forms a “masonry beam” structure after the roof collapses; working resistance of the support calculated by the method of ultimate bearing capacity was adequate to meet the requirement of roof load; roof load of coal pillar was related to the length of key block and fracture position; and increasing the size of coal pillar could ensure the stability of both coal pillar and roof.

Analysis of Mining-induced Response for Floor Roadway Engineering and Surrounding Rock Control

For problem of surrounding rock control and instability of floor roadway under the influence of mining, the combination of site investigation, theoretical analysis, numerical calculation and field measurement methods are used. Firstly, the simplified calculation model of surrounding rock stress for floor roadway was established, and the calculation formula of that was theoretically derived. Secondly, the mining-induced responsive laws and deformation mechanism of surrounding rock stress for floor roadway were deeply analyzed. The results show that in the mining-induced neighborhood, the response of surrounding rock stress for floor roadway is extremely sensitive, and dynamic pressure coefficient of major principal stress is continuously increasing, which is the main stage for deformation occurred in surrounding rock. It is also found that mining response value of horizontal stress of floor roadway is much higher than that of vertical stress, which easily causes serious deformation in places where high deviatoric stress exists for two sides of roadway, as well as damage to bracing structure of roof load. Moreover, that can lead to instability of surrounding rock and collapse disaster of roof. Finally, engineering practice for roadway supporting shows that the compound control technology proposed (i.e. anchor with grouting - pressure relief cable - floor cable) is effective for stability controlling of rockmass around floor roadway.

Analysis of Secondary Roof Structure of the Working Face in Shendong Mining Area

A new form of roof—”secondary roof structure” form, according to the characteristics of significant differences existing between the measured roof pressure and the roof pressure calculated by “support-surrounding rock” formulas, exists in working face that was mined under the upper gob at short range in Shendong mining area. The reasons why additional static load of secondary roof came into being were gained through the analysis of main roof weight distribution coefficient. It is that main roof can not transfer all the static load to the front coal wall and the rear caved gangue, and partial weight of the gangue of upper gob served as the additional static load attaching to the roof of working face. The roof parameters of five working faces mining under the upper gob were counted based on the field measurement and theoretical analysis. What is more, here, the relationship between the M/L value and the roof form was analyzed. Also the roof pressure of 21305 working face of 1−2 coal seam was calculated based on the secondary roof structure model, and the additional static load coefficient (T) was used as measurement of the additional static load of secondary roof. Finally, the directions which can be made a breakthrough in theoretical research of secondary roof were introduced.

Design and Numerical Analysis of a Roof-Mounted Bicycle Carrier

The purpose of this paper is to present the design process and subsequent numerical analysis calculations of a new roof-mounted bicycle carrier for vehicles. The bicycle carrier is mounted on the vehicles longitudinal bars. The designed construction is subjected to both static and dynamic load sets to check if it meets the requirements of ISO 11154 norm – which specifies the minimum safety requests for roof load carrier intended for mounting on the roof of passengers cars and light commercial vehicles with a maximum authorized total mass up to 3,5t. To fulfil the specifications associated to safety, standards and traffic laws test four different software packages were used: CATIA V5 and NACA airfoil generator for designing, Cambridge Engineering Selector for choosing the most suitable materials and Abaqus CAE for Finite Element Analysis.

옥상녹화하중이 LH 공동주택 및 부대복리시설의 옥상층 슬래브 설계에 미치는 영향

옥상녹화하중이 LH 공동주택 및 부대복리시설의 옥상층 슬래브 설계에 미치는 영향

Failure mechanism and control technology of longwall coalface in large-cutting-height mining method

The stability control of longwall coalface is the key technology of large-cutting-height mining method. Therefore, a systematic study of the factors that affect coalface stability and its control technology is required in the development of large-cutting-height mining method in China. After the practical field observation and years of study, it was found that the more than 95% of failures in coalface are shear failure. The shear failure analysis model of coalface has been established, that can perform systematic study among factors such as mining height, coal mass strength, roof load, support resistance, and face flipper protecting plate horizontal force. Meanwhile, sensitivity analysis of factors influencing coalface stability showed that improving support capacity, cohesion of coal mass and decreasing roof load of coalface are the key to improve coalface stability. Numerical simulation of the factors affecting coalface stability has been performed using UDEC software and the results are consistent with the theoretical analysis. The coalface reinforcement technology of large-cutting-height mining method using the grouting combined with coir rope is presented. Laboratory tests have been carried out to verify its reinforcement effect and practical application has been implemented in several coal mines with good results. It has now become the main technology to reduce longwall coalface failure of large-cutting-height mining method.

Evaluation of Structural Performance and Dynamic Characteristics of Korean Traditional Timber Structure Sungnyemun

본 논문에서는 전통 목조건축물로 되어 있는 대한민국의 국보 1호인 숭례문의 구조해석을 수행하고 안전도를 평가하였다. 전통 목조건축의 대부분의 하중을 차지하고 있는 숭례문의 지붕하중을 상세히 산정하고 숭례문의 가구구성 특징을 면밀히 살펴 범용 구조해석 소프트웨어인 midas Gen으로 구조해석모델을 구축하였다. 수직하중에 대한 정적구조해석을 수행하고 주요 수직 수평 구조부재의 안전성과 주요 수평부재의 사용성을 평가하였다. 숭례문의 동적거동특성을 평가하기 위하여 현장에서의 충격해머실험과 구조해석 소프트웨어를 이용한 고유치해석을 수행하고 그 결과를 비교하고 주요모드를 도출하였다. 수직하중에 대한 검토결과 숭례문은 구조적 능력에 여유가 있는 것으로 나타났다.In this research, the structural analysis and safety evaluation for Sungnyemun -No.1 national treasure of Korea- was performed. Roof loads were calculated in detail, and structural analysis model was constructed using Midas Gen ver.820. Static structural analysis under vertical loads was performed and safety of main structural members and serviceability of main horizontal members were evaluated. To evaluate dynamic characteristics of Sungnyemun, both field measurements by impact hammer test and eigenvalue analysis by structural analysis software were performed and the results were compared. Sungnyemun showed rooms in their structural capacity.

수직하중에 대한 한옥 기둥부재의 초기설계를 위한 구조검토방안

In this study the section tables for the column members of Hanok were developed, which can be used in the early design stage of Hanok. The key items in developing section tables are column types, wood species and their material properties, connection types between column and horizontal members, roof loads, and member length and their topological disposition. The columns of Hanok are classified as four types, such as, exterior corner column, edge column, interior corner column and interior column. I proposed approximate calculation method for computing tributary loading area for each column types using representative span. The field applicability of the developed column section tables were evaluated using two test-bed Hanoks. The column sections by three methods, that is, detailed structural check, section tables and field adopted section were compared. It turned out that the sections from the section tables are somewhat conservative and has its limit that it did not considered lateral loads, but showed appropriate field applicability in initial design stage of Hanok.

Reliabilities of distances describing bolt placement for high strength steel connections

In the bolted connections, bolt placements are generally described and are generally made in the direction of design effects and in the perpendicular direction to design effects. In these both directions, the reliability of the distance of bolts to the edges of connection plate and the distance of bolts to each other is investigated for high strength steel connections built up with high strength bolts in this study. For this purpose, simple SL (bearing type shear connection) and SLP (bearing type shear connection for body-fit bolts) type steel connections with St 52 grade steel plates with 8 different thicknesses and with 8.8D grade high strength bolts (HV) were constituted and analyzed under H (Dead Loads+Live Loads+Snow Loads+Roof Loads) and HZ (H Loads+Wind Loads+Earthquake Loads) loadings. Geometric properties, material properties and design actions were taken as random variables. Monte Carlo Simulation method was used to compute failure risk and the first order second moment method was used to determine the reliability indexes of those different distances describing the placement of bolts. Results obtained from computations have been presented in graphics and in a Table. Then, they were compared with some values proposed by some structural codes. Finally, new equations were constituted for minimum and maximum values of distances describing bolt placement by regression analyses performed on those results.

Model for Snow Loading on Gable Roofs

AbstractA particularly large database containing simultaneous measurements of roof and ground snow loads were analyzed for the purpose of establishing a simple empirical model for gable roof snow loads. Due to the nature of the database, the model was developed specifically for unheated structures with nonslippery roof surfaces. As such, it is expected to provide conservative load estimates for heated structures and structures with slippery roof surfaces. The model results are compared to corresponding provisions for balanced and unbalanced snow loads in various United States and European codes and load standards.

Assessment and restoration of the first Greek power plant – Registered monument of industrial heritage

The first electric power station in Greece is a registered monument of the international industrial heritage. The building consists of three longitudinal parts with a total area of 4800m2 approximately in plan and has two levels of a height of 3m and 12m respectively. The structural system consists mainly of stone masonry walls and a steel roof. Nowadays the building is scheduled to be reused as a Museum of Electric Power and the need for structural upgrade arose mainly from current seismic requirements. According to the structural assessment study, the prevailing problem of the building is the combination of the presence of very high walls, interrupted by transverse walls at a distance of approximately 80m, and the complete lack of horizontal diaphragms. The building’s architectural, historic and technological value is significant and its preservation, by minimization of interventions, posed several problems to the retrofit design. New steel frames connected to and cooperating with the masonry walls were designed to bear the vertical roof loads and restore the horizontal diaphragm at the roof level, while also reducing the seismic actions at the walls. The total required strength was achieved by additionally implementing vertical post-tensioning bars and FRP strips.

UNA METODOLOGÍA INTEGRAL DE PROTECCIÓN PARA PREDECIR LOS RIESGOS DE APANTALLAMIENTO EN MINAS DE CARBÓN EN ESTADOS UNIDOS

RESUMEN: La prediccion del riesgo de apantallamiento (shield support) es importante para la seguridad y la productividad de una mina de carbon subterranea. Por lo tanto, este estudio presenta una metodologia completa para predecir los riesgos de apoyo en la proteccion de una zona minera virgen. Una superficie total de 33 pozos fueron perforados para cubrir la zona de explotacion minera. Todos los analisis se basan en la amplia fuerza y propiedades fisicas de los estratos por encima y por debajo del carbon veta B, incluyendo la propia veta B. El modelo modificado de bloque desprendido del techo se utilizo para determinar el apoyo capacidad de carga del techo, y en el techo para cargar mapas de isopacas tres alturas mineras fueron a la distribucion de la carga en diferentes alturas. Una ecuacion de regresion fue utilizado para obtener el maximo de presion suelo, y el mapa de isopacas mostro la diferencia de valor entre fuerza y masa rocosa suelo distribucion de la presion. Para aclarar las discontinuidades geologicas del techo inmediato y variacion de tipo tendencia diagrama, una valla, y las correspondientes respuestas. Gracias a la combinacion de la capacidad de carga del techo, suelo y geologicos las discontinuidades, los peligros de soporte se pone claramente de manifiesto en un mapa de peligros. La metodologia propuesta puede predecir el potencial apoyo en la proteccion los riesgos e identificar las areas en que apoyo complementario puede ponerse en practica, permitiendo asi que los ingenieros de minas para incorporar la capacidad de carga del techo, el piso y las discontinuidades geologicas con eficacia los riesgos integrados en un mapa de prediccion de diseno y estrategias de apoyo complementario. Keywords: prediccion del peligro del soporte de apantallamiento, zona minera virgen, capacidad de carga del techo, presion en el suelo, diagrama valla, mapa de isopacas.

자계서원 영귀루 붕괴 원인 분석 연구

일반적으로 전통 목구조의 주요 구조 부재 단면은 상부 지붕 하중에 의한 안전율이 상당히 커서 갑작스런 붕괴가 발생되는 경우는 매우 드물다. 그러나 최근 자계서원 영귀루는 지진, 태풍 등과 같은 외부 하중이 발생되지 않은 상태에서 붕괴되었다. 본 연구는 자계서원 영귀루의 붕괴 현황을 분석하고 상부 하중에 대한 구조내력을 중심으로 검토하고자 한다. 영귀루의 붕괴 전후 현황 조사 및 붕괴 양상을 분석하고 구조해석을 통해 전면 우측부분의 기둥 지지력 상실과 상부 지붕 하중의 불균형 등에 의해 전체 구조물의 붕괴되었을 가능성을 제시하였다. 이는 향후 건축문화재 등 전통 목구조의 구조적 안정성 확보를 위한 기초자료로 제공될 수 있다. In general, the horizontal section of the beam element in traditional wooden structures has a very high safety factor as the area is comparably big so it is very rare for the building to collapse in a sudden. Recently the Younggwilu(Pavilion) in Jagyeseowon(Traditional Private School) was collapsed from its natural state without any external load factors like the earthquake or typhoon. This study is analyzing the present state of the collapsed Younggwilu building and examining the structural strength of the upper structure and roof load. Structural analysis of the building was undertaken with the collected data of the investigation for the before and after state of the building and analysis of the collapse condition. The cause of collapse could be indicated as supporting failure of the front right column and the instability of the upper roof load distribution. This research could be provided as basic data for the structural stability of the traditional wooden structures for architectural cultural heritage.

Mechanical Behavior of Single-Layer Two-Way Grid Cylindrical Latticed Shell with Out-of-Plane Tension Members

Single layer two-way grid shell with in-plane and out-of-plane tension members is a new type of single-layer latticed shell roof. This study treats the effects of tension member installation on the buckling load and strength of a single layer two-way grid cylindrical shell roof by the numerical method. The tension members are installed to stiffen the rigidity of a single layer two-way grid shell roof and improve its stability behavior. Tension member installation and placement pattern is focused as both diagonal members of two-way grids and out-of-plane stiffened members in a cylindrical surface. The diagonal member and the out-of-plane member are used to increase the in-plane and the out-of-plane rigidity of a single layer two-way grid shell, respectively. The tension member placement pattern, the load distribution patterns, the initial imperfections and the initial axial force are considered for the numerical calculation parameters. It is confirmed by the numerical analysis that the tension members in out-of-plane and diagonals caused the increase in the buckling and strength of two-way grid shell.

Wood Panelized Roof Subpurlin Hanger Construction Defect Assessment and Load Testing to Establish Defect Tolerances

AbstractWood panelized roof systems are a highly popular system for the construction of large-footprint, low-slope roofs, typically for single-story warehouse or industrial buildings. These panelized systems have been used for decades, commonly in the western United States. In general, large modular sections of the roof assembly are constructed on the ground, then lifted into place and connected to the primary roof support elements, which allows for rapid roof erection. In 2008, a 2×6 by 3.0-m (10-ft)-long wood subpurlin fell from a building’s roof structure and landed on the floor approximately 9.1 m (30 ft) below during roof maintenance work. The building was constructed about 3 years prior to the subpurlin falling incident. The authors investigated the cause of the incident. Installation errors of the subpurlin hanger were found in sufficient quantity that the investigation grew to include a total of 21 similar buildings built by the same contractor, representing more than 370,000 m2 (4 million sq ft) ...

Structure Composition and Mechanical Principle of Assembled Self-Supported Warehouse

This paper describes the structure composition and characteristic of assembled self-supported warehouse. And its mechanical principle is introduced and compared with both the assembled pallet rack and the building structure. The assembled self-supported warehouse combines the two structure systems effect. The longitudinal horizontal load is transferred to foundation by means of roof truss and multi-pan portal rigid frame and the lateral horizontal load is transferred by means of spine bracing system and semi-rigid frame. Load on roof and goods load are transferred separately from roof truss and beams to columns, then these loads are transferred to foundation.

A numerical investigation of seismic performance of large span single-layer latticed domes with semi-rigid joints

It is still inadequate for investigating the highly nonlinear and complex mechanical behaviors of single-layer latticed domes by only performing a force-based demand-capacity analysis. The energy-based balance method has been largely accepted for assessing the seismic performance of a structure in recent years. The various factors, such as span-to-rise ratio, joint rigidity and damping model, have a remarkable effect on the load-carrying capacity of a single-layer latticed dome. Therefore, it is necessary to determine the maximum load-carrying capacity of a dome under extreme loading conditions. In this paper, a mechanical model for members of the semi-rigidly jointed single-layer latticed domes, which combines fiber section model with semi-rigid connections, is proposed. The static load-carrying capacity and seismic performance on the single-layer latticed domes are evaluated by means of the mechanical model. In these analyses, different geometric parameters, joint rigidities and roof loads are discussed. The buckling behaviors of members and damage distribution of the structure are presented in detail. The sensitivity of dynamic demand parameters of the structures subjected to strong earthquakes to the damping is analyzed. The results are helpful to have a better understanding of the seismic performance of the single-layer latticed domes.

Deep-hole pre-split blasting mechanism and its application for controlled roof caving in shallow depth seams

The shallow depth coal seams mined in the Shendong Mining Area has led to large area roof weighting frequently due to large thickness, high tensile strength and small overlying load of the main roof. As a result, many accidents have happened including hydraulic support being iron-bound, water inrush through the penetrating cracks along coal wall, and potentially induce large area residual pillars instability and even wind blast damage particularly in the conditions beneath a room mining goaf. To prevent the large area roof weighting accidents, deep-hole pre-split blasting technology for controlled roof caving is a suitable method and has been widely applied in the mines, and many in situ trials have already achieved a sound performance. According to the field conditions of the shallow depth coal seams, this paper employs cylindrical cavity expansion theory to calculate the three blasting-induced divisions including break zone, fracture zone and elastic vibration zone. The software of LS-DYNA3D was applied to establish a deep-hole pre-split blasting model, which presented the rock stress field and the break scope affected by the high energy explosion stress wave. The simulation results revealed the blasting for controlled roof caving mechanism and also optimized the blasting parameters. The field observations showed that, with the application of deep-hole pre-split blasting technology in Shigetai Mine, Shendong Mining Area, the first main roof weighting length was about 17.4m, and neither a hydraulic support being iron-bound nor a serious roof subsidence in the form of step convergence in the mining face happened during the first weighting period. The field application of deep-hole pre-split blasting for controlled roof caving has achieved the expected effects.

An investigation into the influence of a temperature load of a suspended roof in measurements for diagnostic purposes.

This paper presents issues concerning the necessity and possibility of including a temperature load of a suspended, open structure, especially in terms of correct identifying a displace- ment caused by snow and ice loads. Using statistical analysis tools, based on the results of periodic measurements, appropri- ate calculations were carried out. Both possibilities and limita- tions of this approach and the use of outcomes were indicated and the need for and directions of a continued research in this area were demonstrated.