LATERAL LOAD ANALYSIS OF TWO DIMENSIONAL FRAME

INTRODUCTION

In seismic analysis the earthquake forces are considered as lateral forces which represent the ground motion caused by earthquake. These lateral loads can seriously damage the structure and might even cause collapse of the structure. Comparison of portal method, D-value method and computer program has been made for analysis of two dimensional frame. 

PORTAL METHOD

The portal method is based on the assumptions that the shear force in an interior column is twice the shear force in an exterior column, there is a point of inflection at the center of each column, and there is a point of inflection at the center of each beam.

Shear force (V)

Portal method assumes that internal columns will take twice as much shear than the external columns, so therefore, the ratio in which shear force is distributed here will be 1:2:2:1.

Equation for exterior column:

Equation for interior column:

Bending moment (M)

Equation for calculating bending moments:

M = Shear force x (0.5xcolumn height)

D-VALUE METHOD

This method gives a tool for solving high static indeterminacy of the structural framing of the building. The D-value of a resisting elements at any one story is defined by the amount of shear reactive to the element when the relative horizontal displacement at the story under consideration has a unit value. The D-value method has been used for the analysis of seismic forces.

Moment of inertia is calculated using I = bh³/12.

Beam and column stiffness is calculated using K = I/L

Column stiffness is calculated using K̅ = (K₁ + K₂) / K_c (Bottom story, one end fixed) & K̅ = (K₁ + K₂+ K₃+ K₄) / 2K_c (Upper stories)

Story shear is calculated using V_n =[ V_t / ΣD_n ] D_n

Moment at bottom face is calculated using M_b = VYh

Moment at top face is calculated using M_t = V (1-Y)h 

COMPUTER MODELLING using ETABS

ETABS is a vast but easy to use software developed specifically for buildings and building structures. Its function includes modeling, analytical design, and detailing processes. ETABS help in analysis of large and complex buildings, even of nonlinear behavior.

ETABS has the ability to analyze the building of any possible configuration. ETABS also works on the following stages. Inserting all the relevant information, that are geometry, material properties, section properties, & loads and load cases. Assign material properties, section properties of given model. Story forces are imported by equivalent static lateral force method. Shear forces and bending moments are obtained by analyzing the model.

RESULTS

CONCLUSION

Portal method, because of its assumptions, is not as accurate as the D-value method upon comparison with ETABS results, but the approximations makes this method of analysis quite simpler and thus can be used for low rise buildings.

D-value method, being more precise, can be used for high rise buildings where the accuracy cannot be compromised.

Analysis by,

Aisha Iftikhar & team

SUPPLY CHAIN RISK MANAGEMENT-2

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              iii.        RISK EVALUATION

Acceptable risk levels will be unique to each organization and supply chain. They may vary by commodity, product, or service, as well as over time. Different risk-tolerance levels may be set for different levels of the organization. While generally tied to financial impact, through which risks may best be understood and compared, risks may also be tied to other corporate assets such as reputation.

One means of evaluating risk is to use a “heat-map” showing risk-events on a matrix defining likelihood and consequence levels. This technique allows managers to easily see the relative likelihood and consequence of differing risks. To use this method effectively it is critical to have well-defined and consistently used criteria for the different likelihood and consequence levels.

              iv.        RISK TREATMENT

When an enterprise understands its supply chain and analyzed its potential risks, it can implement an effective supply-chain risk management program with its partners, that is, its suppliers, carriers, and logistics providers. Such a program should have at least three elements: protecting the supply chain, responding to events, and continuing business operations while recovering from events. We discuss each of these below. An effective supply-chain risk management program must ensure that an enterprise and its partners implement appropriate measures to fully secure goods and their components from the point of origin to final destination.

Protection of Supply Chain includes:

ü  Physical Security

ü  Access Controls

ü  Personal Security

ü  Education and Training

ü  Procedural Security

ü  IT Security

ü  Business Partner Security

ü  Conveyance Security

Crisis Management comprises the overall strategic and tactical responses of an organization to recognize and respond effectively, efficiently and comprehensively to actualize threats. It involves proactive measures to detect, respond to, and recover from a crisis event. Crisis Management preparation and response activities are characterized by several phases:

ü  Preparation

ü  Response (consisting of Risk Assessment, Critical Incident Planning, Risk Mitigation, Emergency Response and Communications to Internal and External Stakeholders and Media Relations)

ü  Recovery and Business Resumption

ü  Testing, Training and Plan Maintenance

     To be effective, business-continuity planning (also referred to as business-continuity management) should be an integrated management process supported from the top levels and managed at both organizational and operational levels. A business-continuity planning team should also establish company risk-tolerance levels and recovery priorities, validate business-recovery strategies, designate team members from each critical business function, ensure planning and documentation meets established timelines, and conduct periodic evaluation of the business-continuity planning program as based on performance objectives. 

SUPPLY CHAIN RISK MANAGEMENT-1

1.  DEFINITION:

Supply Chain Risk Management (SCRM) is the implementation of strategies to manage both everyday and exceptional risks along the supply chain based on continuous risk assessment with the objective of reducing vulnerability and ensuring continuity. (Source: Cranfield University, School of Management).

Risk= Probability of Occurrence x Consequences

2.  Risk Management Process:

The process begins with identifying internal and external environments. Mapping its supply chain can help an enterprise identify the risks it faces and how best to prioritize and address them. Once a firm understands how to identify risks, it may undertake risk identification and assessment, which includes risk identification, risk analysis, and risk evaluation. If a firm has identified and prioritized the risks that it faces, it can devise risk treatment plans. This includes measures to protect the supply chain from risks, plans to respond to events that these risks may cause, and plans to continue operations in the face of disruptions and fully recovering from them. This may also involve determining ways to measure risks and the effectiveness of plans to limit them or to respond to disruptions.

              i.        RISK IDENTIFICATION

Risk identification might begin with brainstorming sessions, previous risk assessments, surveys, or still other efforts to identify and list potential risks within supply-chain processes. In any project risk can be categorized as:

-        Supply Risk

-        Process Risk

-        Demand Risk

-        Network/ Control Risk

-        Environmental Risk

-        SUPPLY RISK

Supply risk comes from dependency on key suppliers. It includes quality of supplied raw material, management of raw material and delay in provision due to transport, environmental or other accidental issue.

-        PROCESS RISK

Process risk comprises of productivity issues of both material and man power. A faulty equipment or machinery will affect the manufacturing process. Similarly ineffective staff or work crew will delay the process. Electric power failure, problem in computers or software and capacity shortage is classified as Process Risk.

-        DEMAND RISK

Inaccurate forecasts and unrealistic deadline may lead into quality issues which may cause loss of major customers. Innovative competitors in market may also lead a firm at shortage of demand.

-        NETWORK/CONTROL RISK

Lack of communication and collaboration, poor planning and security risk can be referred as Network/ Control Risk. Wrong administrator or rule maker and hierarchy levels in a firm/team create communication gap between employee and team player. Loss of data whether electronic or hard copy file can risk a firm a long time loss.

-        ENVIRONMENTAL RISK

Natural disasters and calamities are considered as Environmental Risk. Earthquake, hurricane or snow may cause destruction as well as long term delay of a project. Changes in government policies, economic recession and unavailability of technology are also categorized as Environmental Risk.

              ii.        RISK ANALYSIS

The risk analysis process should estimate the likelihood and consequence of risks facing a firm and accordingly prioritize them for ultimate treatment. Once an enterprise has identified its top risks, it may use more sophisticated methods, such as the bow-tie method, to fully understand the nature of the risk and to rate the likelihood and consequence of inherent risk (i.e., risk in the absence of any treatment) and residual risk (i.e., level of risk remaining after treatment).

Probabilistic studies of disaster such as earthquake or wind snow help out in planning. For example, we have charts for percentage increase of earthquake event over 50 years or 100 years. Also we have charts for maximum capable earthquake for an area. Similarly, we have charts for winds available.

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