Behavior and Design of Commercial Multistory Buildings Subjected to Blast

The behavior of nonmilitary buildings subjected to blast is considered. Case studies from World War II are described, as well as more recent events from the detonation of large vehicle borne devices in the Middle East, North America, and Europe. Conventional methods for nonseismic design are shown to lead to frames with overstrong beams connected together by relatively weak connections. This may explain much of the evidence from bomb damaged buildings in which building connections have been observed to fracture in a brittle manner when subjected to blast. The risk of progressive collapse may be minimized by strengthening beam to column connections located at close proximity to potential vehicle borne devices and a capacity design method for such strengthening is advocated.     

包钢薄板坯连铸厂房钢结构设计及其特点

本文介绍了包钢薄板坯连铸主厂房钢结构的设计及特点。该厂房为单层重型工业厂房，下柱为组合式H型钢双肢柱，屋面大梁为焊接工字钢梁，基本柱距为12m，车间设置295t／67t／22t吊车，屋面和墙面采用彩色压型钢板。同时，在结构选型和构造方面有新的改进和发展。     

Hodgkin's disease: a tumor with disturbed immunological pathways

An experimental testing program was conducted to investigate the uplift capacity of various rafter to top plate connections. Rather than simply testing the fastener in an ideal test specimen configuration, attention is paid to more realistic test specimens that account for as-built conditions. Consideration is also given to repetitive systems of these connections such as would be found in roof systems. The results from this investigation provide basic data on failure modes and capacities. Comparisons are made between test values, calculated design values, and manufacturers' published values. In addition to metal straps, alternative connection methods such as adhesives are investigated, and consideration is given to both new construction and retrofit of existing structures. The results from this study are used to develop possible schedules for rafter to top plate connections considering different roof slopes, rafter lengths, wind speeds, exposures, and internal pressures.     

Wind Damage to Masonry Buildings

An examination has been made of the methods of construction of masonry‐walled buildings, and their performance in severe windstorms. Particular emphasis was placed on low‐rise buildings using unreinforced concrete block walls and light roofs, which suffer the majority of wind damage. It is shown that traditionally built, nonengineered buildings have become more wind sensitive in recent years as the result of a reduction in the number of internal walls and a lowering of roof weights. Empirical design procedures regarding wall height‐to‐thickness ratios and roof anchorage have not changed to reflect this increased sensitivity, leaving many modern, nonengineered buildings with insufficient wind resistance. Professionally designed structures often have a similar structural form to traditionally built structures, since the same empirical design rules are often used to size walls and roof anchors. The longer roof spans in these buildings render them even more sensitive to wind uplift loads, and subject to progressive collapse. The inadequacies of present building code requirements are discussed and recommendations for improvements are made.     

Failure of Cold-Formed Steel Beams during Concrete Placement

During a concrete placement on the second story of a building under construction, the supporting cold-formed steel beams collapsed. Four workers were injured. The collapse occurred while concrete was being placed onto steel decking on the second floor of the structure. Cold-formed steel beams, without shoring, supported the steel decking. Analysis of the steel beams under the weight of concrete and workers using the applicable American Concrete Institute and American Iron and Steel Institute documents indicated that the beams were overstressed for construction loads. After the collapse, part of the structure was rebuilt using thicker beams. For the reconstruction, the slab was shored. Designing with cold-formed steel requires knowledge of failure modes that can often be safely ignored with hot-rolled steel, such as local buckling. Engineers designing with this material should take care to obtain the proper codes and design documents.     

Stability and Strength of Rigid and Semirigid Plane Frameworks

A computational technique for incorporating stability and strength into the analysis of plane frameworks is presented. The procedure for computing critical and/or collapse loads and for identifying the corresponding failure mode is outlined. The analysis is based on nonlinear kinematic relations and linearly elastic material behavior except at the plastic hinges—concentrated plasticity. The connections can be treated either as rigid or as flexible. The supports, in general, contain rotational restraints. The developed solution methodology is applicable to all multistory‐multibay orthogonal frames. The examples analyzed in the paper include: (1) A single‐story‐two‐bay frame with rigid joint connections; (2) a single‐story‐three‐bay frame with flexible joint connections; (3) a two‐story‐single‐bay frame with both rigid and flexible joint connections; and (4) a three‐story‐two‐bay frame with rigid joint connections. In all cases the loading consists of a symmetric distribution of concentrated loads on the beams, applied at the midspan positions and at or near the beam‐to‐column joints. The effect of several geometric and structural parameters is assessed.     

Bio-Based Composite Roof for Residential Construction

Bio-based composites are an innovative new class of materials that offer many advantages over traditional fiber reinforced composite materials, and may be suitable for use in light duty construction. A study was conducted to develop a bio-based composite roof structure, suitable for residential construction. First, to develop basic information about the flexural performance of the bio-composite, seven different beams were fabricated using a soybean oil-based resin and natural reinforcement (flax or recycled paper). The beams were tested in four-point bending to failure. Results showed that the beams made with recycled paper wrapped around the foam cores were the strongest and the stiffest of the beams tested. Using this composite design, a monolithic composite roof system was designed for residential construction. A scale model unit width beam from the roof was fabricated and tested. Tests included three- and four-point bending, a quasi-distributed load test, and test to failure. The model beam was shown to satisfy the design deflection criteria and had an ultimate strength 11 times greater than the design load. As this was a true scale model specimen, the results demonstrate that the prototype roof would also satisfy the design criteria for strength and stiffness, with similar factors of safety.     

Ronan Point Apartment Tower Collapse and its Effect on Building Codes

In the early morning hours of May 16, 1968, the occupant of apartment 90 on the 18th floor of the 22-story Ronan Point apartment tower, in London, lit a match to brew her morning cup of tea. The resulting gas explosion initiated a partial collapse of the structure that killed four people and injured 17 (one of whom subsequently died). On investigation, the apartment tower was found to be deeply flawed in both design and construction. The existing building codes were found to be inadequate for ensuring the safety and integrity of high-rise precast concrete apartment buildings. The Larsen–Nielson building system, intended for buildings with only six stories, had been extended past the point of safety. The tower consisted of precast panels joined together without a structural frame. The connections relied, in large part, on friction. The apartment tower lacked alternate load paths to redistribute forces in the event of a partial collapse. When the structure was dismantled, investigators found appallingly poor workmanship at the critical connections between the panels. Subsequently, building codes in many countries have adopted structural integrity or “robustness” provisions that may be directly traced to the Ronan Point collapse.     

Analysis of Causes of Falsework Failures in Concrete Structures

A study of 85 major falsework collapses of bridges and buildings in the past 23 yrs has documented the types of collapsed falseworks and failed permanent structures, the construction stages at the time of collapse, and the causes of failures. Three causes of failure were identified: triggering; enabling; and procedural causes. Most failures occurred because of the interaction of the triggering and enabling events that were, in many cases, produced by inadequacies in the procedural methods. Impact forces resulting from concreting operations have repeatedly triggered falsework failures that were enabled by deficiencies in the falsework bracings, components, connections, foundations, and design. Inadequate review of falsework design and monitoring procedures were frequent problems that facilitated the occurrernce of these events. The findings emphasize the importance of proper delineation of responsibility of each party in the building process in order to reduce falsework failures in the future.     

Evaluation of Distress in Supports of Hyperbolic Paraboloid Shell

A church building structure, composed of a saddle-type hyperbolic paraboloid concrete shell roof supported by buttresses and brick masonry walls, was constructed in 1963. At one corner of the structure, the perimeter of the roof shell projects beyond the exterior building walls to form a canopy over the main entrance. This canopy is partially supported by two brick masonry fin walls that project outward from the main building walls. At the time of original design, closed-form methods (equations) were the only practical way of analyzing this shell structure. However, the configuration of the roof shell was not consistent with detailing requirements of the closed-form methods. After 36?years of service, the fin walls had bowed significantly, were exhibiting wide cracks, had slipped laterally with respect to the roof shell, and were in danger of collapse. The writer led an investigation team that developed a finite element model of the church structure, studied the behavior of the church structure when subjected to applied loads and temperature changes, and developed repairs to restore structural integrity and serviceability.     

Structural Concept, Design, and Experimental Verification of a Glass Fiber-Reinforced Polymer Sandwich Roof Structure

This paper reports on the design and construction of a lightweight glass fiber-reinforced polymer roof structure in Basel, Switzerland. The sandwich construction allowed for an integration of static, building physical and architectural functions that enabled the prefabrication of the entire roof in only four lightweight elements that were easily transported to the site and rapidly installed. Cutting of foam blocks with a computerized numerical control machine and adhesive bonding proved to be advantageous procedures for the fabrication of the complex roof shape, without the use of expensive molds. The factor of safety of the design was adjusted during the design process through experimental verification. Although some of the characteristic material properties were overestimated in the preliminary design, the design properties for the final design were higher than for the preliminary design as it was possible to reduce the resistance factors (according to Eurocode format) after testing by a factor of 2.0. Existing design models and test standards to determine material properties proved to be applicable.     

Survey of Sustainable Building Design Practices in North America, Europe, and Asia

Sustainable design should be applied in all phases of the life cycle of a building, including programming, design, building construction, building operation, and finally demolition. This paper compares and contrasts sustainable design programs based on the life cycle of a building in North America, Europe, and Asia. Tables comparing programs from these three regions are provided for each phase in the life cycle of a building. These tables can be used by building design professionals as a reference guide to sustainable design around the world. The tables also highlight specific requirements or concerns that are applicable in a particular region. The similarities between different programs and regions can be taken into consideration during the planning of sustainable design work, regardless of the region of construction. Finally, references to more detailed program documents are provided so that interested readers can determine specific requirements that apply in a region of interest.     

Performance of Steel Frame Building which Experienced Intense Ground Motion

A two-story, steel moment frame building that was severely damaged during the Northridge earthquake (1994) is studied in detail. Immediately following the earthquake, the building was judged unsafe for occupancy due to a residual displacement of 7.6 cm (3 in.) in the first story. Opening of the exterior facade revealed severe cracking in the moment connections. All connections contained cracks that started in the weld at the bottom flange of the beam and propagated across the column flange and into the column panel zone. Four welded, beam-to-column, moment connections were taken from the building for additional cyclic testing under controlled conditions in the laboratory to evaluate their residual strength and deformation capacity. Results indicate that the badly damaged specimens still have significant residual strength and deformation capacity. All damaged specimens were tested to 3% rotation.     

建(构)筑物渗漏水浅析

通过对部分建(构)筑物渗漏水工程(如屋面漏水、地下工程漏水、厕浴间漏水、外墙渗水)的调查、分析,发现其主要原因为:防水设计不合理,材料质量无保证,施工质量差。建(构)筑物渗漏水影响建(构)筑物外观和使用功能;严重者导致钢筋锈蚀、混凝土发生碱骨料反应,受力系统承载力降低,危及主体结构安全。为此,应规范防水工程设计、施工,加强防水工程的监理和质检监管力度,增大防水工程的投入,采用防水新材料、新技术、新工艺等措施防治建(构)筑物渗漏水。     

CFRP Rehabilitation of Concrete Frame Joints with Inadequate Shear and Anchorage Details

The research presented in this study involves full-scale experimental evaluation of carbon fiber-reinforced polymer (CFRP) rehabilitation for existing beam-column joints designed for gravity load with common pre-1970s deficient reinforcement details when subjected to cyclic loading. Numerous studies have demonstrated effectiveness of externally bonded fiber-reinforced polymer (FRP) materials for retrofitting the deteriorating RC structures. Although these materials are widely used in bridges, their applications in buildings have been somewhat limited. In particular, the experimental investigations on external FRP retrofit of deficient beam-column joints have not thoroughly been investigated and they are mainly on scaled-down specimens. The failure of these subassemblies, which possess lack of shear reinforcement within the joint core and shortly embedded positive beam reinforcement, would possibly result in catastrophic collapse of reinforced concrete frame structure during an earthquake event. Recognizing the urgent need to upgrade these structural subassemblies, the current investigation uses CFRP retrofit techniques to enhance the performance of such deficient joints. Experimental variables studied entail the developed CFRP retrofit configurations, and magnitude of the applied column axial load. Comparative analysis of the lateral loads versus drift hysteresis loops, stiffness degradation, and total dissipated energy curves of three as-built and three corresponding CFRP-retrofitted RC joints revealed that significant improvement in the shear capacity of the upgraded joints occurred. More importantly, the slippage of short embedded beam positive reinforcement into the joint was substantially controlled due to the developed CFRP retrofit. The results demonstrate the effectiveness of CFRP retrofit configurations in enhancing the structural performance of actual size connections.     

Parametric Coordinator for Engineering Design

Coordination of design information is essential for the design team to provide accurate technical documents for the actual construction. Design changes are inevitable during any ordinary building project. If the design changes are not properly managed, design conflicts will be created, which will result in more expensive design or even failure in the design-construction process. However, little research has been done to address the issue and thereby provide tools for the management of design changes. This paper presents a novel approach that can facilitate the coordination of design information through managing design changes with the help of a parametric coordinator. Design changes of dimensions between different building components are specially discussed. The proposed parametric coordinator provides each building component with the linking knowledge that is described as a dimensional property and a reference property. A group design method is applied to check the design consistency. Illustrative examples are presented to demonstrate the feasibility of the proposed parametric approach for design change management.     

单层工业厂房改造中拔柱施工方法的改进

将托梁拔柱和托梁截柱拔柱方法结合起来，连续拆除单层工业厂房相邻多根混凝土柱，达到良好的效果，该施工方案为厂房改造提供了一种新的处理拔柱方式。     

建筑屋面防水层渗漏的原因及防治

建筑防水在建筑设计和施工中占有十分重要的地位。该文通过材料、设计、施工、管理四个方面对建筑屋面防水层渗漏的原因进行分析,并提出相应的防治措施。     

Shear Strengthening of Interior Slab–Column Connections Using Carbon Fiber-Reinforced Polymer Sheets

This paper presents the results of an experimental investigation undertaken to evaluate the punching shear capacity of interior slab–column connections, strengthened using flexible carbon fiber-reinforced polymer (CFRP) sheets. Sixteen square (670×670?mm) slab–column connections with different slab thicknesses (55 and 75 mm) and reinforcement ratios (1 and 1.5%) were tested. Twelve specimens were strengthened using CFRP sheets and the remaining four specimens were kept as controls. Without strengthening, all specimens were designed to experience punching shear failure. The CFRP sheets were bonded to the tension face of the specimens in two perpendicular directions parallel to the internal ordinary steel reinforcement. The test results clearly demonstrate that using CFRP leads to significant improvements in the flexural stiffness, flexural strength, and shear capacity of beam–column connections. Depending on the content of the ordinary reinforcement, thickness of the slab, and area of CFRP sheet, the flexural strength increased between 26 and 73% and the shear capacity increased between 17 and 45%. The measured stress in the CFRP sheets at nominal strength varied between 22 and 69% of the ultimate tensile strength of the fibers. Comparison with available prediction equations showed that the punching shear capacity can be predicted with reasonable accuracy if the contribution of CFRP reinforcement to the increase in flexural strength is accounted for. On the other hand, the code design expressions were conservative in predicting the capacity observed in the tests.