10 PRACTICAL PROBLEMS TO THINK BEFORE DESIGNING A FOUNDATION
Get link
Facebook
Twitter
Pinterest
Email
Other Apps
10 PRACTICAL PROBLEMS TO THINK BEFORE DESIGNING A FOUNDATION
PRACTICAL PROBLEMS TO KEEP IN MIND BEFORE FOUNDATION DESIGN
Foundation design
There are, in foundation design, a number of practical construction problems and costs to be considered.
The chief ones are:
The foundations should be kept as shallow as possible, commensurate with climatic effects on, and strength of, the surface soil; particularly in waterlogged ground. Excavation in seriously waterlogged ground can be expensive and slow.
Expensive and complex shuttering details should be avoided, particularly in stiffened rafts. Attention should be paid to buildability.
Reduction in the costs of piling, improvements in ground treatment, advances in soil mechanics, etc. have considerably altered the economics of design, and many standard solutions are now out-of-date. There is a need to constantly review construction costs and techniques.
Designers need to be more aware of the assumptions made in design, the variability of ground conditions, the occasional inapplicability of refined soil analyses and the practicality of construction.
The reliability of the soil investigation, by critical assessment.
Effect of construction on ground properties, i.e. vibration from piling, deterioration of ground exposed by excavation in adverse weather conditions, removal of overburden, seasonal variation in the water-table, compaction of the ground by construction plant.
Effect of varying shape, length and rigidity of the foundation, and the need for movement and settlement joints.
After-effects on completed foundations of sulfate attack on concrete, ground movements due to frost heave, shrinkable clays, and the effects of trees; also changes in local environment, e.g. new construction, re-routing of heavy traffic, installation of plant in adjoining factories causing impact and vibration.
Fast but expensive construction may be more economic than low-cost but slow construction to clients needing quick return on capital investment.
Effect of new foundation loading on existing adjoining structures.
These practical considerations are illustrated by the following examples.
EXAMPLE 1:EXCAVATION IN WATERLOGGED GROUND
A simple example of excavation in waterlogged ground exemplifies the problems which may be encountered. At the commencement of a 1–2 m deep underpinning contract in mass concrete, groundwater was found to be rising much higher and faster than previous trial pits had indicated. The circumstances were such that a minipiling contractor was quickly brought onto site, and speedily installed what was, at face value, a more costly solution, but proved far less expensive overall than slowly struggling to construct with mass concrete while pumping. As will be well-known to many of our readers, few small site pumps are capable of running for longer than two hours without malfunctioning!
EXAMPLE 2:VARIABILITY OF GROUND CONDITIONS
On one site a varying clay fill had been placed to a depth of roughly 2 m over clay of a similar soft to firm consistency.
Since a large industrial estate was to be developed on the site in numerous phases by different developers, a thorough site investigation had been undertaken. Nevertheless, on more than one occasion, the project engineer found himself looking down a hole of depth 2 m or greater, trying to decide if a mass concrete base was about to be founded in fill or virgin ground, and in either case whether it would achieve 100 kN/m2 allowable bearing pressure or not. This emphasizes the importance of engineers looking at the ground first-hand by examining the trial pits rather than relying on the site investigation report from the relative comfort of their desk.
EXAMPLE 3:RELIABILITY OF THE SOILS INVESTIGATION
On one site a contractor quoted a small diameter steel tube pile length of 5 m (to achieve a suitable set), based upon a site investigation report. In the event his piles achieved the set at an average of 22 m (!), so obviously cost complications ensued. In addition to this, one of the main difficulties was convincing the contractor to guarantee his piles at that depth, as he was understandably concerned about their slenderness.
EXAMPLE 4:DETERIORATION OF GROUND EXPOSED BY EXCAVATION
An investigation by the authors’ practice of one particular failure springs to mind as an example. Part of a factory had been demolished exposing what had been a party wall, but a 20 m length of this wall was undermined by an excavation for a new service duct and a classic failure ensued. The exposed excavation was then left open over a wet weekend, resulting in softening of the face and a collapse occurred early on the Monday.
So often the most catastrophic of failures are as a result of these types of classic textbook examples, which could be prevented by the most basic precautions.
EXAMPLE 5:EFFECT OF NEW FOUNDATION ON EXISTING STRUCTURE
A new storage silo was to be constructed within an existing mill, and the proposal was to found it on a filled basement, in the same way that the adjacent silo had been 20 years before. The authors’ practice was called in for their opinion fairly late in the day, with the steel silo already under fabrication.
After investigation of the fill, the client was advised to carry the new silo on small diameter piles through the fill down to bedrock. This would thereby avoid placing additional loading into the fill, and thus causing settlement of the existing silo.
Construction tools list for building construction works such as concrete, brick masonry, leveling, wood works, floor works, slab works, brick laying, plastering etc. is provided. Every construction tool is necessary to achieve good results in the whole project. Along with these tools, the workers should also use some safety tools to prevent them from the unexpected accidents. Construction Tools List for Building Construction Some important construction tools and their uses are listed below: Bolster Boning rod Brick hammer Bump cutter/screed Chisel Circular saw Concrete mixer Cordless drill Crowbar Digging bar End frames Float Gloves Hand saw Helmet Hoe Iron pan Jack plane Ladder Line and pins Mason’s square Measuring box Measuring tape Measuring wheel Pick axe Plumb bob Plumb rule Polishers Putty knife Rammer Rubber Boots Safety glasses Safety helmet Sand screen machine Scratchers Sledge hammer Spade Spirit level Straight edge brushes Til
Building materials or construction materials are the major requirement in this modern age of technology. There are many types of building materials used for different construction works. Properties of Building Materials For a material to be considered as building material, it should have required engineering properties suitable for construction works. These properties of building materials are responsible for its quality and capacity and helps to decide applications of these material. Such properties of building materials are categorized as follows. Physical properties Mechanical properties Chemical properties Electrical properties Magnetic properties Thermal properties Physical Properties of Building Materials These are the properties required to estimate the quality and condition of the material without any external force. The physical properties of engineering materials are as follows. Bulk density Porosity Durability Density Density index Specific gravity
Setting out building plan on ground is one of the most significant steps in building constructions and any errors at this stage would cause considerable problems, if it is not tackled immediately. Errors During Setting Out Building Plan on Ground There are different types of errors that might be made when a structure is set out for example gross errors, systematic errors and random errors. These errors should be prevented and there are some measures to tackle these issues. These measures will be discussed in the following sections. Fig.1: Setting Out of Building Plan on Ground Fig.2: Setting Out Building Plan on Ground How to Prevent Errors During Setting Out of Building? Following are the different types of control that should be carried out to prevent any errors during setting out building plan on ground: Good practice in office On site control Equipment and staff Checks Marking the ground Use of grid offset Good Practice in Office To successfully set
Factors which affect selection of foundation for a building can be many from the soil conditions to the type of structure and loads from the building. All the factors are considered during selection of foundation for durable building construction. Factors Affecting Selection of Foundation Following are the factors which affect the selection of suitable foundations for building construction: Loads from building Type of soil Type of structures in neighborhood Type of foundations 1. Loads from Building The first factor considered is loads from building on the foundation. This load is a combination of dead load and imposed loads on the buildings. Other loads such as wind loads, earthquake loads, snow loads etc. are also considered based on location. The quantity of loads depends on the type of structure, number of floors and material of construction. As the number of floors increases, the dead load and imposed loads also increase. Choice of material for construction su
Various types of ceiling are used in building construction. Applications, aesthetics, advantages and disadvantages of these types of ceilings are discussed in this article. The ceiling of a building form one of the most important structural elements it terms of functionality as well as creativity which in turn bring good aesthetics to the building interior. This document would help you understand ceilings that in turn would help you understand the most suitable options while undertaking either repair or renovation work of our building interior. The ceiling gains a definition, ” A part of a building which encloses and is exposed overhead in a room, protected shaft or circulation space.” It helps us to create an enclosure and separation between spaces. They provide perfect lighting in the room by controlling diffusion of light. It also controls the sound around a room by making the room sound proof. It, therefore, stops the passage of sound between the rooms. Now ceiling also po
WHAT IS VOLUME BATCHING OF CONCRETE? Batching of concrete means measuring different ingredients of concrete (i.e. cement, sand, coarse aggregate and water) before mixing it. When this measurement is done on the basis of volume, we call it Volume Batching . Below are mentioned some of important points to remember before adopting volume batching method in field. Volume batching is not a good method for measuring concrete materials. It is not applicable in case of reinforced concrete structure. This method of concrete batching may not be economical. It can be only used for unimportant concrete or for small concrete works. HOW VOLUME BATCHING IS DONE IN FIELD? Before batching concrete ingredients in terms of volume, we need to know two things. What is the relative proportion of concrete ingredients in terms of volume? What is the water-cement ratio? After knowing these two things you can proceed to batch concrete ingredients in field. The table shown below can be
Many factors affects the determination of depth of foundation. Calculation for foundation depth is done based on type of soil, ground water table, loads from structure, bearing capacity of soil and other factors. General factors to be considered for determining depth of foundation are: 1. Load applied from structure to the foundation 2. Bearing capacity of soil 3. Depth of water level below the ground surface 4. Types of soil and depth of layers in case of layered soil 5. Depth of adjacent foundation The minimum depth of foundation should be considered to ensure that the soil is having the required safe bearing capacity as assumed in the design. However, it is advised to carry out soil investigation before deciding on depth of foundation. Soil investigation report will suggest the foundation depth based on the type of structure, soil properties, depth of water table, and all other variable that should be considered. Soil investigation report provides bearing capacity of
Underpinning is a method for repair and strengthening of building foundations. Underpinning methods, procedures and their applications in strengthening of different types of foundations is discussed in this article. There are situations where a failure in foundation or footing happens unexpectedly after the completion of whole structure (both sub and superstructure). Under such emergency situation, a remedial method has to be suggested to regain the structural stability. The method of underpinning help to strengthen the foundation of an existing building or any other infrastructure. These involve installation of permanent or temporary support to an already held foundation so that additional depth and bearing capacity is achieved. Selection of Underpinning Methods Underpinning methods are selected based on age of structure and types of works involved. Structure categories based on its age: Ancient Structures :Age greater than 150 years Recent Structures : Age between 5
here are several methods by which calculation of engineering consultant services cost can be carried out in construction. It is possible to employ various charging approach at different phase of the consultant services. The application of each method or combination of methods is dependent on nature, scope and complexity of the required engineering services. In this article, these charging consulting services are discussed. Following are the topics discussed for calculating cost of engineering services or consulting services in construction: What are the factors that affect the engineering service cost? Methods for charging engineering services What are the Factors that affect the Engineering Service Cost in Construction? There are various factors that control the cost of engineering services required for a specific project. These factors are outlined below: The conditions at project site. Degree of danger that may be encountered and exposure possibility. System of pr
Construction PM Software A new wave of web and cloud apps are streamlining communication, simplifying document management, and improving efficiency in construction management. Here are some of top construction management tools: Smartsheet Smartsheet is a spreadsheet-inspired work management tool with robust collaboration and communication features. With pre-built construction templates, it’s easy to create a timeline, track progress, manage documents, and organize the details. Gantt charts are automatically created and auto-adjust every time a change is made, so you can share the most up-to-date timeline with team members or stakeholders. You can upload files from your computer, Google Drive, Box, Dropbox, Evernote, or add a web URL, creating a central repository for all project documentation and contracts. Team members can have discussions directly in the sheet and set reminders and alerts, so everyone is on the same page. And lastly, Smartsheet integrates with ot
Comments